[v10,2/2] x86: Add support for compiling {raw|w}memchr with high ISA level

1. Refactor files so that all implementations for in the multiarch
   directory.
    - Essentially moved sse2 {raw|w}memchr.S implementation to
      multiarch/{raw|w}memchr-sse2.S

    - The non-multiarch {raw|w}memchr.S file now only includes one of
      the implementations in the multiarch directory based on the
      compiled ISA level (only used for non-multiarch builds.
      Otherwise we go through the ifunc selector).

2. Add ISA level build guards to different implementations.
    - I.e memchr-avx2.S which is ISA level 3 will only build if
      compiled ISA level <= 3. Otherwise there is no reason to include
      it as we will always use one of the ISA level 4
      implementations (memchr-evex{-rtm}.S).

3. Add new multiarch/rtld-{raw}memchr.S that just include the
   non-multiarch {raw}memchr.S which will in turn select the best
   implementation based on the compiled ISA level.

4. Refactor the ifunc selector and ifunc implementation list to use
   the ISA level aware wrapper macros that allow functions below the
   compiled ISA level (with a guranteed replacement) to be skipped.
    - Guranteed replacement essentially means that for any ISA level
      build there must be a function that the baseline of the ISA
      supports. So for {raw|w}memchr.S since there is not ISA level 2
      function, the ISA level 2 build still includes the ISA level
      1 (sse2) function. Once we reach the ISA level 3 build, however,
      {raw|w}memchr-avx2{-rtm}.S will always be sufficient so the ISA
      level 1 implementation ({raw|w}memchr-sse2.S) will not be built.

Tested with and without multiarch on x86_64 for ISA levels:
{generic, x86-64-v2, x86-64-v3, x86-64-v4}

And m32 with and without multiarch.
---
 sysdeps/x86_64/isa-default-impl.h             |   8 +
 sysdeps/x86_64/memchr.S                       | 357 +----------------
 sysdeps/x86_64/multiarch/ifunc-evex.h         |  29 +-
 sysdeps/x86_64/multiarch/ifunc-impl-list.c    |  72 ++--
 sysdeps/x86_64/multiarch/memchr-avx2.S        |   5 +-
 sysdeps/x86_64/multiarch/memchr-evex.S        |   5 +-
 sysdeps/x86_64/multiarch/memchr-sse2.S        | 363 +++++++++++++++++-
 sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S |   7 +-
 sysdeps/x86_64/multiarch/rawmemchr-avx2.S     |   7 +-
 sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S |   8 +-
 sysdeps/x86_64/multiarch/rawmemchr-evex.S     |   7 +-
 sysdeps/x86_64/multiarch/rawmemchr-sse2.S     | 198 +++++++++-
 sysdeps/x86_64/multiarch/rtld-memchr.S        |  18 +
 sysdeps/x86_64/multiarch/rtld-rawmemchr.S     |  18 +
 sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S   |   7 +-
 sysdeps/x86_64/multiarch/wmemchr-avx2.S       |   7 +-
 sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S   |   8 +-
 sysdeps/x86_64/multiarch/wmemchr-evex.S       |   7 +-
 sysdeps/x86_64/multiarch/wmemchr-sse2.S       |   9 +-
 sysdeps/x86_64/rawmemchr.S                    | 184 +--------
 sysdeps/x86_64/wmemchr.S                      |  28 ++
 21 files changed, 740 insertions(+), 612 deletions(-)
 create mode 100644 sysdeps/x86_64/multiarch/rtld-memchr.S
 create mode 100644 sysdeps/x86_64/multiarch/rtld-rawmemchr.S
 create mode 100644 sysdeps/x86_64/wmemchr.S

On Wed, Jun 22, 2022 at 1:58 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> 1. Refactor files so that all implementations for in the multiarch
>    directory.
>     - Essentially moved sse2 {raw|w}memchr.S implementation to
>       multiarch/{raw|w}memchr-sse2.S
>
>     - The non-multiarch {raw|w}memchr.S file now only includes one of
>       the implementations in the multiarch directory based on the
>       compiled ISA level (only used for non-multiarch builds.
>       Otherwise we go through the ifunc selector).
>
> 2. Add ISA level build guards to different implementations.
>     - I.e memchr-avx2.S which is ISA level 3 will only build if
>       compiled ISA level <= 3. Otherwise there is no reason to include
>       it as we will always use one of the ISA level 4
>       implementations (memchr-evex{-rtm}.S).
>
> 3. Add new multiarch/rtld-{raw}memchr.S that just include the
>    non-multiarch {raw}memchr.S which will in turn select the best
>    implementation based on the compiled ISA level.
>
> 4. Refactor the ifunc selector and ifunc implementation list to use
>    the ISA level aware wrapper macros that allow functions below the
>    compiled ISA level (with a guranteed replacement) to be skipped.
>     - Guranteed replacement essentially means that for any ISA level
>       build there must be a function that the baseline of the ISA
>       supports. So for {raw|w}memchr.S since there is not ISA level 2
>       function, the ISA level 2 build still includes the ISA level
>       1 (sse2) function. Once we reach the ISA level 3 build, however,
>       {raw|w}memchr-avx2{-rtm}.S will always be sufficient so the ISA
>       level 1 implementation ({raw|w}memchr-sse2.S) will not be built.
>
> Tested with and without multiarch on x86_64 for ISA levels:
> {generic, x86-64-v2, x86-64-v3, x86-64-v4}
>
> And m32 with and without multiarch.
> ---
>  sysdeps/x86_64/isa-default-impl.h             |   8 +
>  sysdeps/x86_64/memchr.S                       | 357 +----------------
>  sysdeps/x86_64/multiarch/ifunc-evex.h         |  29 +-
>  sysdeps/x86_64/multiarch/ifunc-impl-list.c    |  72 ++--
>  sysdeps/x86_64/multiarch/memchr-avx2.S        |   5 +-
>  sysdeps/x86_64/multiarch/memchr-evex.S        |   5 +-
>  sysdeps/x86_64/multiarch/memchr-sse2.S        | 363 +++++++++++++++++-
>  sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S |   7 +-
>  sysdeps/x86_64/multiarch/rawmemchr-avx2.S     |   7 +-
>  sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S |   8 +-
>  sysdeps/x86_64/multiarch/rawmemchr-evex.S     |   7 +-
>  sysdeps/x86_64/multiarch/rawmemchr-sse2.S     | 198 +++++++++-
>  sysdeps/x86_64/multiarch/rtld-memchr.S        |  18 +
>  sysdeps/x86_64/multiarch/rtld-rawmemchr.S     |  18 +
>  sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S   |   7 +-
>  sysdeps/x86_64/multiarch/wmemchr-avx2.S       |   7 +-
>  sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S   |   8 +-
>  sysdeps/x86_64/multiarch/wmemchr-evex.S       |   7 +-
>  sysdeps/x86_64/multiarch/wmemchr-sse2.S       |   9 +-
>  sysdeps/x86_64/rawmemchr.S                    | 184 +--------
>  sysdeps/x86_64/wmemchr.S                      |  28 ++
>  21 files changed, 740 insertions(+), 612 deletions(-)
>  create mode 100644 sysdeps/x86_64/multiarch/rtld-memchr.S
>  create mode 100644 sysdeps/x86_64/multiarch/rtld-rawmemchr.S
>  create mode 100644 sysdeps/x86_64/wmemchr.S
>
> diff --git a/sysdeps/x86_64/isa-default-impl.h b/sysdeps/x86_64/isa-default-impl.h
> index 34634668e5..b374a38b8b 100644
> --- a/sysdeps/x86_64/isa-default-impl.h
> +++ b/sysdeps/x86_64/isa-default-impl.h
> @@ -46,4 +46,12 @@
>  # error "Unsupported ISA Level!"
>  #endif
>
> +#if IS_IN(rtld) && !defined USE_MULTIARCH
> +#  error "RTLD version should only exist in multiarch build"
> +#endif
> +
> +#if defined USE_MULTIARCH && !IS_IN(rtld)
> +#  error "Multiarch build should not use ISA_DEFAULT_IMPL without RTLD"
> +#endif

Please do

#if IS_IN (rtld)
#else
#endif

>  #include ISA_DEFAULT_IMPL
> diff --git a/sysdeps/x86_64/memchr.S b/sysdeps/x86_64/memchr.S
> index a160fd9b00..20b43508c4 100644
> --- a/sysdeps/x86_64/memchr.S
> +++ b/sysdeps/x86_64/memchr.S
> @@ -15,358 +15,13 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#include <sysdep.h>
> +#define MEMCHR __memchr
>
> -#ifdef USE_AS_WMEMCHR
> -# define MEMCHR                wmemchr
> -# define PCMPEQ                pcmpeqd
> -# define CHAR_PER_VEC  4
> -#else
> -# define MEMCHR                memchr
> -# define PCMPEQ                pcmpeqb
> -# define CHAR_PER_VEC  16
> -#endif
> +#define DEFAULT_IMPL_V1        "multiarch/memchr-sse2.S"
> +#define DEFAULT_IMPL_V3        "multiarch/memchr-avx2.S"
> +#define DEFAULT_IMPL_V4        "multiarch/memchr-evex.S"
>
> -/* fast SSE2 version with using pmaxub and 64 byte loop */
> +#include "isa-default-impl.h"
>
> -       .text
> -ENTRY(MEMCHR)
> -       movd    %esi, %xmm1
> -       mov     %edi, %ecx
> -
> -#ifdef __ILP32__
> -       /* Clear the upper 32 bits.  */
> -       movl    %edx, %edx
> -#endif
> -#ifdef USE_AS_WMEMCHR
> -       test    %RDX_LP, %RDX_LP
> -       jz      L(return_null)
> -#else
> -       punpcklbw %xmm1, %xmm1
> -       test    %RDX_LP, %RDX_LP
> -       jz      L(return_null)
> -       punpcklbw %xmm1, %xmm1
> -#endif
> -
> -       and     $63, %ecx
> -       pshufd  $0, %xmm1, %xmm1
> -
> -       cmp     $48, %ecx
> -       ja      L(crosscache)
> -
> -       movdqu  (%rdi), %xmm0
> -       PCMPEQ  %xmm1, %xmm0
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -
> -       jnz     L(matches_1)
> -       sub     $CHAR_PER_VEC, %rdx
> -       jbe     L(return_null)
> -       add     $16, %rdi
> -       and     $15, %ecx
> -       and     $-16, %rdi
> -#ifdef USE_AS_WMEMCHR
> -       shr     $2, %ecx
> -#endif
> -       add     %rcx, %rdx
> -       sub     $(CHAR_PER_VEC * 4), %rdx
> -       jbe     L(exit_loop)
> -       jmp     L(loop_prolog)
> -
> -       .p2align 4
> -L(crosscache):
> -       and     $15, %ecx
> -       and     $-16, %rdi
> -       movdqa  (%rdi), %xmm0
> -
> -       PCMPEQ  %xmm1, %xmm0
> -       /* Check if there is a match.  */
> -       pmovmskb %xmm0, %eax
> -       /* Remove the leading bytes.  */
> -       sar     %cl, %eax
> -       test    %eax, %eax
> -       je      L(unaligned_no_match)
> -       /* Check which byte is a match.  */
> -       bsf     %eax, %eax
> -#ifdef USE_AS_WMEMCHR
> -       mov     %eax, %esi
> -       shr     $2, %esi
> -       sub     %rsi, %rdx
> -#else
> -       sub     %rax, %rdx
> -#endif
> -       jbe     L(return_null)
> -       add     %rdi, %rax
> -       add     %rcx, %rax
> -       ret
> -
> -       .p2align 4
> -L(unaligned_no_match):
> -       /* "rcx" is less than 16.  Calculate "rdx + rcx - 16" by using
> -          "rdx - (16 - rcx)" instead of "(rdx + rcx) - 16" to void
> -          possible addition overflow.  */
> -       neg     %rcx
> -       add     $16, %rcx
> -#ifdef USE_AS_WMEMCHR
> -       shr     $2, %ecx
> -#endif
> -       sub     %rcx, %rdx
> -       jbe     L(return_null)
> -       add     $16, %rdi
> -       sub     $(CHAR_PER_VEC * 4), %rdx
> -       jbe     L(exit_loop)
> -
> -       .p2align 4
> -L(loop_prolog):
> -       movdqa  (%rdi), %xmm0
> -       PCMPEQ  %xmm1, %xmm0
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -       jnz     L(matches)
> -
> -       movdqa  16(%rdi), %xmm2
> -       PCMPEQ  %xmm1, %xmm2
> -       pmovmskb %xmm2, %eax
> -       test    %eax, %eax
> -       jnz     L(matches16)
> -
> -       movdqa  32(%rdi), %xmm3
> -       PCMPEQ  %xmm1, %xmm3
> -       pmovmskb %xmm3, %eax
> -       test    %eax, %eax
> -       jnz     L(matches32)
> -
> -       movdqa  48(%rdi), %xmm4
> -       PCMPEQ  %xmm1, %xmm4
> -       add     $64, %rdi
> -       pmovmskb %xmm4, %eax
> -       test    %eax, %eax
> -       jnz     L(matches0)
> -
> -       test    $0x3f, %rdi
> -       jz      L(align64_loop)
> -
> -       sub     $(CHAR_PER_VEC * 4), %rdx
> -       jbe     L(exit_loop)
> -
> -       movdqa  (%rdi), %xmm0
> -       PCMPEQ  %xmm1, %xmm0
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -       jnz     L(matches)
> -
> -       movdqa  16(%rdi), %xmm2
> -       PCMPEQ  %xmm1, %xmm2
> -       pmovmskb %xmm2, %eax
> -       test    %eax, %eax
> -       jnz     L(matches16)
> -
> -       movdqa  32(%rdi), %xmm3
> -       PCMPEQ  %xmm1, %xmm3
> -       pmovmskb %xmm3, %eax
> -       test    %eax, %eax
> -       jnz     L(matches32)
> -
> -       movdqa  48(%rdi), %xmm3
> -       PCMPEQ  %xmm1, %xmm3
> -       pmovmskb %xmm3, %eax
> -
> -       add     $64, %rdi
> -       test    %eax, %eax
> -       jnz     L(matches0)
> -
> -       mov     %rdi, %rcx
> -       and     $-64, %rdi
> -       and     $63, %ecx
> -#ifdef USE_AS_WMEMCHR
> -       shr     $2, %ecx
> -#endif
> -       add     %rcx, %rdx
> -
> -       .p2align 4
> -L(align64_loop):
> -       sub     $(CHAR_PER_VEC * 4), %rdx
> -       jbe     L(exit_loop)
> -       movdqa  (%rdi), %xmm0
> -       movdqa  16(%rdi), %xmm2
> -       movdqa  32(%rdi), %xmm3
> -       movdqa  48(%rdi), %xmm4
> -
> -       PCMPEQ  %xmm1, %xmm0
> -       PCMPEQ  %xmm1, %xmm2
> -       PCMPEQ  %xmm1, %xmm3
> -       PCMPEQ  %xmm1, %xmm4
> -
> -       pmaxub  %xmm0, %xmm3
> -       pmaxub  %xmm2, %xmm4
> -       pmaxub  %xmm3, %xmm4
> -       pmovmskb %xmm4, %eax
> -
> -       add     $64, %rdi
> -
> -       test    %eax, %eax
> -       jz      L(align64_loop)
> -
> -       sub     $64, %rdi
> -
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -       jnz     L(matches)
> -
> -       pmovmskb %xmm2, %eax
> -       test    %eax, %eax
> -       jnz     L(matches16)
> -
> -       movdqa  32(%rdi), %xmm3
> -       PCMPEQ  %xmm1, %xmm3
> -
> -       PCMPEQ  48(%rdi), %xmm1
> -       pmovmskb %xmm3, %eax
> -       test    %eax, %eax
> -       jnz     L(matches32)
> -
> -       pmovmskb %xmm1, %eax
> -       bsf     %eax, %eax
> -       lea     48(%rdi, %rax), %rax
> -       ret
> -
> -       .p2align 4
> -L(exit_loop):
> -       add     $(CHAR_PER_VEC * 2), %edx
> -       jle     L(exit_loop_32)
> -
> -       movdqa  (%rdi), %xmm0
> -       PCMPEQ  %xmm1, %xmm0
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -       jnz     L(matches)
> -
> -       movdqa  16(%rdi), %xmm2
> -       PCMPEQ  %xmm1, %xmm2
> -       pmovmskb %xmm2, %eax
> -       test    %eax, %eax
> -       jnz     L(matches16)
> -
> -       movdqa  32(%rdi), %xmm3
> -       PCMPEQ  %xmm1, %xmm3
> -       pmovmskb %xmm3, %eax
> -       test    %eax, %eax
> -       jnz     L(matches32_1)
> -       sub     $CHAR_PER_VEC, %edx
> -       jle     L(return_null)
> -
> -       PCMPEQ  48(%rdi), %xmm1
> -       pmovmskb %xmm1, %eax
> -       test    %eax, %eax
> -       jnz     L(matches48_1)
> -       xor     %eax, %eax
> -       ret
> -
> -       .p2align 4
> -L(exit_loop_32):
> -       add     $(CHAR_PER_VEC * 2), %edx
> -       movdqa  (%rdi), %xmm0
> -       PCMPEQ  %xmm1, %xmm0
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -       jnz     L(matches_1)
> -       sub     $CHAR_PER_VEC, %edx
> -       jbe     L(return_null)
> -
> -       PCMPEQ  16(%rdi), %xmm1
> -       pmovmskb %xmm1, %eax
> -       test    %eax, %eax
> -       jnz     L(matches16_1)
> -       xor     %eax, %eax
> -       ret
> -
> -       .p2align 4
> -L(matches0):
> -       bsf     %eax, %eax
> -       lea     -16(%rax, %rdi), %rax
> -       ret
> -
> -       .p2align 4
> -L(matches):
> -       bsf     %eax, %eax
> -       add     %rdi, %rax
> -       ret
> -
> -       .p2align 4
> -L(matches16):
> -       bsf     %eax, %eax
> -       lea     16(%rax, %rdi), %rax
> -       ret
> -
> -       .p2align 4
> -L(matches32):
> -       bsf     %eax, %eax
> -       lea     32(%rax, %rdi), %rax
> -       ret
> -
> -       .p2align 4
> -L(matches_1):
> -       bsf     %eax, %eax
> -#ifdef USE_AS_WMEMCHR
> -       mov     %eax, %esi
> -       shr     $2, %esi
> -       sub     %rsi, %rdx
> -#else
> -       sub     %rax, %rdx
> -#endif
> -       jbe     L(return_null)
> -       add     %rdi, %rax
> -       ret
> -
> -       .p2align 4
> -L(matches16_1):
> -       bsf     %eax, %eax
> -#ifdef USE_AS_WMEMCHR
> -       mov     %eax, %esi
> -       shr     $2, %esi
> -       sub     %rsi, %rdx
> -#else
> -       sub     %rax, %rdx
> -#endif
> -       jbe     L(return_null)
> -       lea     16(%rdi, %rax), %rax
> -       ret
> -
> -       .p2align 4
> -L(matches32_1):
> -       bsf     %eax, %eax
> -#ifdef USE_AS_WMEMCHR
> -       mov     %eax, %esi
> -       shr     $2, %esi
> -       sub     %rsi, %rdx
> -#else
> -       sub     %rax, %rdx
> -#endif
> -       jbe     L(return_null)
> -       lea     32(%rdi, %rax), %rax
> -       ret
> -
> -       .p2align 4
> -L(matches48_1):
> -       bsf     %eax, %eax
> -#ifdef USE_AS_WMEMCHR
> -       mov     %eax, %esi
> -       shr     $2, %esi
> -       sub     %rsi, %rdx
> -#else
> -       sub     %rax, %rdx
> -#endif
> -       jbe     L(return_null)
> -       lea     48(%rdi, %rax), %rax
> -       ret
> -
> -       .p2align 4
> -L(return_null):
> -       xor     %eax, %eax
> -       ret
> -END(MEMCHR)
> -
> -#ifndef USE_AS_WMEMCHR
> -strong_alias (memchr, __memchr)
> +weak_alias (__memchr, memchr)
>  libc_hidden_builtin_def(memchr)
> -#endif
> diff --git a/sysdeps/x86_64/multiarch/ifunc-evex.h b/sysdeps/x86_64/multiarch/ifunc-evex.h
> index b8f7a12ea2..856c6261f8 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-evex.h
> +++ b/sysdeps/x86_64/multiarch/ifunc-evex.h
> @@ -19,24 +19,28 @@
>
>  #include <init-arch.h>
>
> -extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
> -extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> -extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex_rtm) attribute_hidden;
>
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
> +
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
>
>  static inline void *
>  IFUNC_SELECTOR (void)
>  {
> -  const struct cpu_features* cpu_features = __get_cpu_features ();
> -
> -  if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> -      && CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> -      && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
> +  const struct cpu_features *cpu_features = __get_cpu_features ();
> +
> +  /* NB: The X86_ISA_* feature check macros are evaluated at
> +     compile time.  */
> +  if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> +      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> +      && X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> +                                     AVX_Fast_Unaligned_Load))
>      {
> -      if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
> -         && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
> +      if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
> +         && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
>         {
>           if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
>             return OPTIMIZE (evex_rtm);
> @@ -47,9 +51,12 @@ IFUNC_SELECTOR (void)
>        if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
>         return OPTIMIZE (avx2_rtm);
>
> -      if (!CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_VZEROUPPER))
> +      if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> +                                      Prefer_No_VZEROUPPER))
>         return OPTIMIZE (avx2);
>      }
>
> +  /* This is unreachable (compile time checked) if ISA level >= 3
> +     so no need for a robust fallback here.  */
>    return OPTIMIZE (sse2);
>  }
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index 883362f63d..bf52cf96d0 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -25,7 +25,8 @@
>
>  /* Fill ARRAY of MAX elements with IFUNC implementations for function
>     NAME supported on target machine and return the number of valid
> -   entries.  */
> +   entries.  Each set of implementations for a given function is sorted in
> +   descending order by ISA level.  */
>
>  size_t
>  __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> @@ -53,24 +54,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>
>    /* Support sysdeps/x86_64/multiarch/memchr.c.  */
>    IFUNC_IMPL (i, name, memchr,
> -             IFUNC_IMPL_ADD (array, i, memchr,
> -                             CPU_FEATURE_USABLE (AVX2),
> -                             __memchr_avx2)
> -             IFUNC_IMPL_ADD (array, i, memchr,
> -                             (CPU_FEATURE_USABLE (AVX2)
> -                              && CPU_FEATURE_USABLE (RTM)),
> -                             __memchr_avx2_rtm)
> -             IFUNC_IMPL_ADD (array, i, memchr,
> +             X86_IFUNC_IMPL_ADD_V4 (array, i, memchr,
>                               (CPU_FEATURE_USABLE (AVX512VL)
>                                && CPU_FEATURE_USABLE (AVX512BW)
>                                && CPU_FEATURE_USABLE (BMI2)),
>                               __memchr_evex)
> -             IFUNC_IMPL_ADD (array, i, memchr,
> +             X86_IFUNC_IMPL_ADD_V4 (array, i, memchr,
>                               (CPU_FEATURE_USABLE (AVX512VL)
>                                && CPU_FEATURE_USABLE (AVX512BW)
>                                && CPU_FEATURE_USABLE (BMI2)),
>                               __memchr_evex_rtm)
> -             IFUNC_IMPL_ADD (array, i, memchr, 1, __memchr_sse2))
> +             X86_IFUNC_IMPL_ADD_V3 (array, i, memchr,
> +                             CPU_FEATURE_USABLE (AVX2),
> +                             __memchr_avx2)
> +             X86_IFUNC_IMPL_ADD_V3 (array, i, memchr,
> +                             (CPU_FEATURE_USABLE (AVX2)
> +                              && CPU_FEATURE_USABLE (RTM)),
> +                             __memchr_avx2_rtm)
> +             /* Can be lowered to V1 if a V2 implementation is added.  */
> +             X86_IFUNC_IMPL_ADD_V2 (array, i, memchr,
> +                             1,
> +                             __memchr_sse2))
>
>    /* Support sysdeps/x86_64/multiarch/memcmp.c.  */
>    IFUNC_IMPL (i, name, memcmp,
> @@ -288,24 +292,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>
>    /* Support sysdeps/x86_64/multiarch/rawmemchr.c.  */
>    IFUNC_IMPL (i, name, rawmemchr,
> -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> -                             CPU_FEATURE_USABLE (AVX2),
> -                             __rawmemchr_avx2)
> -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> -                             (CPU_FEATURE_USABLE (AVX2)
> -                              && CPU_FEATURE_USABLE (RTM)),
> -                             __rawmemchr_avx2_rtm)
> -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> +             X86_IFUNC_IMPL_ADD_V4 (array, i, rawmemchr,
>                               (CPU_FEATURE_USABLE (AVX512VL)
>                                && CPU_FEATURE_USABLE (AVX512BW)
>                                && CPU_FEATURE_USABLE (BMI2)),
>                               __rawmemchr_evex)
> -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> +             X86_IFUNC_IMPL_ADD_V4 (array, i, rawmemchr,
>                               (CPU_FEATURE_USABLE (AVX512VL)
>                                && CPU_FEATURE_USABLE (AVX512BW)
>                                && CPU_FEATURE_USABLE (BMI2)),
>                               __rawmemchr_evex_rtm)
> -             IFUNC_IMPL_ADD (array, i, rawmemchr, 1, __rawmemchr_sse2))
> +             X86_IFUNC_IMPL_ADD_V3 (array, i, rawmemchr,
> +                             CPU_FEATURE_USABLE (AVX2),
> +                             __rawmemchr_avx2)
> +             X86_IFUNC_IMPL_ADD_V3 (array, i, rawmemchr,
> +                             (CPU_FEATURE_USABLE (AVX2)
> +                              && CPU_FEATURE_USABLE (RTM)),
> +                             __rawmemchr_avx2_rtm)
> +             /* Can be lowered to V1 if a V2 implementation is added.  */
> +             X86_IFUNC_IMPL_ADD_V2 (array, i, rawmemchr,
> +                             1,
> +                             __rawmemchr_sse2))
>
>    /* Support sysdeps/x86_64/multiarch/strlen.c.  */
>    IFUNC_IMPL (i, name, strlen,
> @@ -748,24 +755,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
>
>    /* Support sysdeps/x86_64/multiarch/wmemchr.c.  */
>    IFUNC_IMPL (i, name, wmemchr,
> -             IFUNC_IMPL_ADD (array, i, wmemchr,
> -                             CPU_FEATURE_USABLE (AVX2),
> -                             __wmemchr_avx2)
> -             IFUNC_IMPL_ADD (array, i, wmemchr,
> -                             (CPU_FEATURE_USABLE (AVX2)
> -                              && CPU_FEATURE_USABLE (RTM)),
> -                             __wmemchr_avx2_rtm)
> -             IFUNC_IMPL_ADD (array, i, wmemchr,
> +             X86_IFUNC_IMPL_ADD_V4 (array, i, wmemchr,
>                               (CPU_FEATURE_USABLE (AVX512VL)
>                                && CPU_FEATURE_USABLE (AVX512BW)
>                                && CPU_FEATURE_USABLE (BMI2)),
>                               __wmemchr_evex)
> -             IFUNC_IMPL_ADD (array, i, wmemchr,
> +             X86_IFUNC_IMPL_ADD_V4 (array, i, wmemchr,
>                               (CPU_FEATURE_USABLE (AVX512VL)
>                                && CPU_FEATURE_USABLE (AVX512BW)
>                                && CPU_FEATURE_USABLE (BMI2)),
>                               __wmemchr_evex_rtm)
> -             IFUNC_IMPL_ADD (array, i, wmemchr, 1, __wmemchr_sse2))
> +             X86_IFUNC_IMPL_ADD_V3 (array, i, wmemchr,
> +                             CPU_FEATURE_USABLE (AVX2),
> +                             __wmemchr_avx2)
> +             X86_IFUNC_IMPL_ADD_V3 (array, i, wmemchr,
> +                             (CPU_FEATURE_USABLE (AVX2)
> +                              && CPU_FEATURE_USABLE (RTM)),
> +                             __wmemchr_avx2_rtm)
> +             /* Can be lowered to V1 if a V2 implementation is added.  */
> +             X86_IFUNC_IMPL_ADD_V2 (array, i, wmemchr,
> +                             1,
> +                             __wmemchr_sse2))
>
>    /* Support sysdeps/x86_64/multiarch/wmemcmp.c.  */
>    IFUNC_IMPL (i, name, wmemcmp,
> diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S
> index c5a256eb37..39be5f7083 100644
> --- a/sysdeps/x86_64/multiarch/memchr-avx2.S
> +++ b/sysdeps/x86_64/multiarch/memchr-avx2.S
> @@ -16,9 +16,10 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#if IS_IN (libc)
> +#include <isa-level.h>
> +#include <sysdep.h>
>
> -# include <sysdep.h>
> +#if ISA_SHOULD_BUILD (3)
>
>  # ifndef MEMCHR
>  #  define MEMCHR       __memchr_avx2
> diff --git a/sysdeps/x86_64/multiarch/memchr-evex.S b/sysdeps/x86_64/multiarch/memchr-evex.S
> index 0fd11b7632..0dd4f1dcce 100644
> --- a/sysdeps/x86_64/multiarch/memchr-evex.S
> +++ b/sysdeps/x86_64/multiarch/memchr-evex.S
> @@ -16,9 +16,10 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#if IS_IN (libc)
> +#include <isa-level.h>
> +#include <sysdep.h>
>
> -# include <sysdep.h>
> +#if ISA_SHOULD_BUILD (4)
>
>  # ifndef MEMCHR
>  #  define MEMCHR       __memchr_evex
> diff --git a/sysdeps/x86_64/multiarch/memchr-sse2.S b/sysdeps/x86_64/multiarch/memchr-sse2.S
> index 2c6fdd41d6..8c561cd687 100644
> --- a/sysdeps/x86_64/multiarch/memchr-sse2.S
> +++ b/sysdeps/x86_64/multiarch/memchr-sse2.S
> @@ -16,13 +16,360 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#if IS_IN (libc)
> -# define memchr __memchr_sse2
> +#include <isa-level.h>
> +#include <sysdep.h>
>
> -# undef strong_alias
> -# define strong_alias(memchr, __memchr)
> -# undef libc_hidden_builtin_def
> -# define libc_hidden_builtin_def(memchr)
> -#endif
> +/* MINIMUM_X86_ISA_LEVEL <= 2 because there is no V2 implementation
> +   so we need this to build for ISA V2 builds. */
> +#if ISA_SHOULD_BUILD (2)
> +
> +# ifndef MEMCHR
> +#  define MEMCHR       __memchr_sse2
> +# endif
> +# ifdef USE_AS_WMEMCHR
> +#  define PCMPEQ               pcmpeqd
> +#  define CHAR_PER_VEC 4
> +# else
> +#  define PCMPEQ               pcmpeqb
> +#  define CHAR_PER_VEC 16
> +# endif
> +
> +/* fast SSE2 version with using pmaxub and 64 byte loop */
> +
> +       .text
> +ENTRY(MEMCHR)
> +       movd    %esi, %xmm1
> +       mov     %edi, %ecx
> +
> +# ifdef __ILP32__
> +       /* Clear the upper 32 bits.  */
> +       movl    %edx, %edx
> +# endif
> +# ifdef USE_AS_WMEMCHR
> +       test    %RDX_LP, %RDX_LP
> +       jz      L(return_null)
> +# else
> +       punpcklbw %xmm1, %xmm1
> +       test    %RDX_LP, %RDX_LP
> +       jz      L(return_null)
> +       punpcklbw %xmm1, %xmm1
> +# endif
> +
> +       and     $63, %ecx
> +       pshufd  $0, %xmm1, %xmm1
> +
> +       cmp     $48, %ecx
> +       ja      L(crosscache)
> +
> +       movdqu  (%rdi), %xmm0
> +       PCMPEQ  %xmm1, %xmm0
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +
> +       jnz     L(matches_1)
> +       sub     $CHAR_PER_VEC, %rdx
> +       jbe     L(return_null)
> +       add     $16, %rdi
> +       and     $15, %ecx
> +       and     $-16, %rdi
> +# ifdef USE_AS_WMEMCHR
> +       shr     $2, %ecx
> +# endif
> +       add     %rcx, %rdx
> +       sub     $(CHAR_PER_VEC * 4), %rdx
> +       jbe     L(exit_loop)
> +       jmp     L(loop_prolog)
> +
> +       .p2align 4
> +L(crosscache):
> +       and     $15, %ecx
> +       and     $-16, %rdi
> +       movdqa  (%rdi), %xmm0
> +
> +       PCMPEQ  %xmm1, %xmm0
> +       /* Check if there is a match.  */
> +       pmovmskb %xmm0, %eax
> +       /* Remove the leading bytes.  */
> +       sar     %cl, %eax
> +       test    %eax, %eax
> +       je      L(unaligned_no_match)
> +       /* Check which byte is a match.  */
> +       bsf     %eax, %eax
> +# ifdef USE_AS_WMEMCHR
> +       mov     %eax, %esi
> +       shr     $2, %esi
> +       sub     %rsi, %rdx
> +# else
> +       sub     %rax, %rdx
> +# endif
> +       jbe     L(return_null)
> +       add     %rdi, %rax
> +       add     %rcx, %rax
> +       ret
> +
> +       .p2align 4
> +L(unaligned_no_match):
> +       /* "rcx" is less than 16.  Calculate "rdx + rcx - 16" by using
> +          "rdx - (16 - rcx)" instead of "(rdx + rcx) - 16" to void
> +          possible addition overflow.  */
> +       neg     %rcx
> +       add     $16, %rcx
> +# ifdef USE_AS_WMEMCHR
> +       shr     $2, %ecx
> +# endif
> +       sub     %rcx, %rdx
> +       jbe     L(return_null)
> +       add     $16, %rdi
> +       sub     $(CHAR_PER_VEC * 4), %rdx
> +       jbe     L(exit_loop)
> +
> +       .p2align 4
> +L(loop_prolog):
> +       movdqa  (%rdi), %xmm0
> +       PCMPEQ  %xmm1, %xmm0
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +       jnz     L(matches)
> +
> +       movdqa  16(%rdi), %xmm2
> +       PCMPEQ  %xmm1, %xmm2
> +       pmovmskb %xmm2, %eax
> +       test    %eax, %eax
> +       jnz     L(matches16)
> +
> +       movdqa  32(%rdi), %xmm3
> +       PCMPEQ  %xmm1, %xmm3
> +       pmovmskb %xmm3, %eax
> +       test    %eax, %eax
> +       jnz     L(matches32)
> +
> +       movdqa  48(%rdi), %xmm4
> +       PCMPEQ  %xmm1, %xmm4
> +       add     $64, %rdi
> +       pmovmskb %xmm4, %eax
> +       test    %eax, %eax
> +       jnz     L(matches0)
> +
> +       test    $0x3f, %rdi
> +       jz      L(align64_loop)
> +
> +       sub     $(CHAR_PER_VEC * 4), %rdx
> +       jbe     L(exit_loop)
> +
> +       movdqa  (%rdi), %xmm0
> +       PCMPEQ  %xmm1, %xmm0
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +       jnz     L(matches)
> +
> +       movdqa  16(%rdi), %xmm2
> +       PCMPEQ  %xmm1, %xmm2
> +       pmovmskb %xmm2, %eax
> +       test    %eax, %eax
> +       jnz     L(matches16)
> +
> +       movdqa  32(%rdi), %xmm3
> +       PCMPEQ  %xmm1, %xmm3
> +       pmovmskb %xmm3, %eax
> +       test    %eax, %eax
> +       jnz     L(matches32)
> +
> +       movdqa  48(%rdi), %xmm3
> +       PCMPEQ  %xmm1, %xmm3
> +       pmovmskb %xmm3, %eax
> +
> +       add     $64, %rdi
> +       test    %eax, %eax
> +       jnz     L(matches0)
> +
> +       mov     %rdi, %rcx
> +       and     $-64, %rdi
> +       and     $63, %ecx
> +# ifdef USE_AS_WMEMCHR
> +       shr     $2, %ecx
> +# endif
> +       add     %rcx, %rdx
> +
> +       .p2align 4
> +L(align64_loop):
> +       sub     $(CHAR_PER_VEC * 4), %rdx
> +       jbe     L(exit_loop)
> +       movdqa  (%rdi), %xmm0
> +       movdqa  16(%rdi), %xmm2
> +       movdqa  32(%rdi), %xmm3
> +       movdqa  48(%rdi), %xmm4
> +
> +       PCMPEQ  %xmm1, %xmm0
> +       PCMPEQ  %xmm1, %xmm2
> +       PCMPEQ  %xmm1, %xmm3
> +       PCMPEQ  %xmm1, %xmm4
>
> -#include "../memchr.S"
> +       pmaxub  %xmm0, %xmm3
> +       pmaxub  %xmm2, %xmm4
> +       pmaxub  %xmm3, %xmm4
> +       pmovmskb %xmm4, %eax
> +
> +       add     $64, %rdi
> +
> +       test    %eax, %eax
> +       jz      L(align64_loop)
> +
> +       sub     $64, %rdi
> +
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +       jnz     L(matches)
> +
> +       pmovmskb %xmm2, %eax
> +       test    %eax, %eax
> +       jnz     L(matches16)
> +
> +       movdqa  32(%rdi), %xmm3
> +       PCMPEQ  %xmm1, %xmm3
> +
> +       PCMPEQ  48(%rdi), %xmm1
> +       pmovmskb %xmm3, %eax
> +       test    %eax, %eax
> +       jnz     L(matches32)
> +
> +       pmovmskb %xmm1, %eax
> +       bsf     %eax, %eax
> +       lea     48(%rdi, %rax), %rax
> +       ret
> +
> +       .p2align 4
> +L(exit_loop):
> +       add     $(CHAR_PER_VEC * 2), %edx
> +       jle     L(exit_loop_32)
> +
> +       movdqa  (%rdi), %xmm0
> +       PCMPEQ  %xmm1, %xmm0
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +       jnz     L(matches)
> +
> +       movdqa  16(%rdi), %xmm2
> +       PCMPEQ  %xmm1, %xmm2
> +       pmovmskb %xmm2, %eax
> +       test    %eax, %eax
> +       jnz     L(matches16)
> +
> +       movdqa  32(%rdi), %xmm3
> +       PCMPEQ  %xmm1, %xmm3
> +       pmovmskb %xmm3, %eax
> +       test    %eax, %eax
> +       jnz     L(matches32_1)
> +       sub     $CHAR_PER_VEC, %edx
> +       jle     L(return_null)
> +
> +       PCMPEQ  48(%rdi), %xmm1
> +       pmovmskb %xmm1, %eax
> +       test    %eax, %eax
> +       jnz     L(matches48_1)
> +       xor     %eax, %eax
> +       ret
> +
> +       .p2align 4
> +L(exit_loop_32):
> +       add     $(CHAR_PER_VEC * 2), %edx
> +       movdqa  (%rdi), %xmm0
> +       PCMPEQ  %xmm1, %xmm0
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +       jnz     L(matches_1)
> +       sub     $CHAR_PER_VEC, %edx
> +       jbe     L(return_null)
> +
> +       PCMPEQ  16(%rdi), %xmm1
> +       pmovmskb %xmm1, %eax
> +       test    %eax, %eax
> +       jnz     L(matches16_1)
> +       xor     %eax, %eax
> +       ret
> +
> +       .p2align 4
> +L(matches0):
> +       bsf     %eax, %eax
> +       lea     -16(%rax, %rdi), %rax
> +       ret
> +
> +       .p2align 4
> +L(matches):
> +       bsf     %eax, %eax
> +       add     %rdi, %rax
> +       ret
> +
> +       .p2align 4
> +L(matches16):
> +       bsf     %eax, %eax
> +       lea     16(%rax, %rdi), %rax
> +       ret
> +
> +       .p2align 4
> +L(matches32):
> +       bsf     %eax, %eax
> +       lea     32(%rax, %rdi), %rax
> +       ret
> +
> +       .p2align 4
> +L(matches_1):
> +       bsf     %eax, %eax
> +# ifdef USE_AS_WMEMCHR
> +       mov     %eax, %esi
> +       shr     $2, %esi
> +       sub     %rsi, %rdx
> +# else
> +       sub     %rax, %rdx
> +# endif
> +       jbe     L(return_null)
> +       add     %rdi, %rax
> +       ret
> +
> +       .p2align 4
> +L(matches16_1):
> +       bsf     %eax, %eax
> +# ifdef USE_AS_WMEMCHR
> +       mov     %eax, %esi
> +       shr     $2, %esi
> +       sub     %rsi, %rdx
> +# else
> +       sub     %rax, %rdx
> +# endif
> +       jbe     L(return_null)
> +       lea     16(%rdi, %rax), %rax
> +       ret
> +
> +       .p2align 4
> +L(matches32_1):
> +       bsf     %eax, %eax
> +# ifdef USE_AS_WMEMCHR
> +       mov     %eax, %esi
> +       shr     $2, %esi
> +       sub     %rsi, %rdx
> +# else
> +       sub     %rax, %rdx
> +# endif
> +       jbe     L(return_null)
> +       lea     32(%rdi, %rax), %rax
> +       ret
> +
> +       .p2align 4
> +L(matches48_1):
> +       bsf     %eax, %eax
> +# ifdef USE_AS_WMEMCHR
> +       mov     %eax, %esi
> +       shr     $2, %esi
> +       sub     %rsi, %rdx
> +# else
> +       sub     %rax, %rdx
> +# endif
> +       jbe     L(return_null)
> +       lea     48(%rdi, %rax), %rax
> +       ret
> +
> +       .p2align 4
> +L(return_null):
> +       xor     %eax, %eax
> +       ret
> +END(MEMCHR)
> +#endif
> diff --git a/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S b/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> index acc5f6e2fb..5c1dcd3ca7 100644
> --- a/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> +++ b/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> @@ -1,4 +1,7 @@
> -#define MEMCHR __rawmemchr_avx2_rtm
> -#define USE_AS_RAWMEMCHR 1
> +#ifndef RAWMEMCHR
> +# define RAWMEMCHR     __rawmemchr_avx2_rtm
> +#endif
> +#define USE_AS_RAWMEMCHR       1
> +#define MEMCHR RAWMEMCHR
>
>  #include "memchr-avx2-rtm.S"

Will we ever use the RTM version as the default?

> diff --git a/sysdeps/x86_64/multiarch/rawmemchr-avx2.S b/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> index 128f9ea637..d6bff28757 100644
> --- a/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> +++ b/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> @@ -1,4 +1,7 @@
> -#define MEMCHR __rawmemchr_avx2
> -#define USE_AS_RAWMEMCHR 1
> +#ifndef RAWMEMCHR
> +# define RAWMEMCHR     __rawmemchr_avx2
> +#endif
> +#define USE_AS_RAWMEMCHR       1
> +#define MEMCHR RAWMEMCHR
>
>  #include "memchr-avx2.S"
> diff --git a/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S b/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> index deda1ca395..8ff7f27c9c 100644
> --- a/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> +++ b/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> @@ -1,3 +1,7 @@
> -#define MEMCHR __rawmemchr_evex_rtm
> -#define USE_AS_RAWMEMCHR 1
> +#ifndef RAWMEMCHR
> +# define RAWMEMCHR     __rawmemchr_evex_rtm
> +#endif
> +#define USE_AS_RAWMEMCHR       1
> +#define MEMCHR RAWMEMCHR
> +

Will we ever use the RTM version as the default?

>  #include "memchr-evex-rtm.S"
> diff --git a/sysdeps/x86_64/multiarch/rawmemchr-evex.S b/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> index ec942b77ba..dc1c450699 100644
> --- a/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> +++ b/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> @@ -1,4 +1,7 @@
> -#define MEMCHR __rawmemchr_evex
> -#define USE_AS_RAWMEMCHR 1
> +#ifndef RAWMEMCHR
> +# define RAWMEMCHR     __rawmemchr_evex
> +#endif
> +#define USE_AS_RAWMEMCHR       1
> +#define MEMCHR RAWMEMCHR
>
>  #include "memchr-evex.S"
> diff --git a/sysdeps/x86_64/multiarch/rawmemchr-sse2.S b/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> index 3841c14c34..e2c2e20d85 100644
> --- a/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> +++ b/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> @@ -16,14 +16,192 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -/* Define multiple versions only for the definition in libc. */
> -#if IS_IN (libc)
> -# define __rawmemchr __rawmemchr_sse2
> -
> -# undef weak_alias
> -# define weak_alias(__rawmemchr, rawmemchr)
> -# undef libc_hidden_def
> -# define libc_hidden_def(__rawmemchr)
> -#endif
> +#include <isa-level.h>
> +#include <sysdep.h>
> +
> +/* MINIMUM_X86_ISA_LEVEL <= 2 because there is no V2 implementation
> +   so we need this to build for ISA V2 builds. */
> +#if ISA_SHOULD_BUILD (2)
> +
> +# ifndef RAWMEMCHR
> +#  define RAWMEMCHR    __rawmemchr_sse2
> +# endif
> +
> +       .text
> +ENTRY (RAWMEMCHR)
> +       movd    %rsi, %xmm1
> +       mov     %rdi, %rcx
> +
> +       punpcklbw %xmm1, %xmm1
> +       punpcklbw %xmm1, %xmm1
> +
> +       and     $63, %rcx
> +       pshufd  $0, %xmm1, %xmm1
> +
> +       cmp     $48, %rcx
> +       ja      L(crosscache)
> +
> +       movdqu  (%rdi), %xmm0
> +       pcmpeqb %xmm1, %xmm0
> +/* Check if there is a match.  */
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +
> +       jnz     L(matches)
> +       add     $16, %rdi
> +       and     $-16, %rdi
> +       jmp     L(loop_prolog)
> +
> +       .p2align 4
> +L(crosscache):
> +       and     $15, %rcx
> +       and     $-16, %rdi
> +       movdqa  (%rdi), %xmm0
> +
> +       pcmpeqb %xmm1, %xmm0
> +/* Check if there is a match.  */
> +       pmovmskb %xmm0, %eax
> +/* Remove the leading bytes.  */
> +       sar     %cl, %eax
> +       test    %eax, %eax
> +       je      L(unaligned_no_match)
> +/* Check which byte is a match.  */
> +       bsf     %eax, %eax
> +
> +       add     %rdi, %rax
> +       add     %rcx, %rax
> +       ret
> +
> +       .p2align 4
> +L(unaligned_no_match):
> +       add     $16, %rdi
> +
> +       .p2align 4
> +L(loop_prolog):
> +       movdqa  (%rdi), %xmm0
> +       pcmpeqb %xmm1, %xmm0
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +       jnz     L(matches)
> +
> +       movdqa  16(%rdi), %xmm2
> +       pcmpeqb %xmm1, %xmm2
> +       pmovmskb %xmm2, %eax
> +       test    %eax, %eax
> +       jnz     L(matches16)
> +
> +       movdqa  32(%rdi), %xmm3
> +       pcmpeqb %xmm1, %xmm3
> +       pmovmskb %xmm3, %eax
> +       test    %eax, %eax
> +       jnz     L(matches32)
> +
> +       movdqa  48(%rdi), %xmm4
> +       pcmpeqb %xmm1, %xmm4
> +       add     $64, %rdi
> +       pmovmskb %xmm4, %eax
> +       test    %eax, %eax
> +       jnz     L(matches0)
> +
> +       test    $0x3f, %rdi
> +       jz      L(align64_loop)
> +
> +       movdqa  (%rdi), %xmm0
> +       pcmpeqb %xmm1, %xmm0
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +       jnz     L(matches)
> +
> +       movdqa  16(%rdi), %xmm2
> +       pcmpeqb %xmm1, %xmm2
> +       pmovmskb %xmm2, %eax
> +       test    %eax, %eax
> +       jnz     L(matches16)
>
> -#include "../rawmemchr.S"
> +       movdqa  32(%rdi), %xmm3
> +       pcmpeqb %xmm1, %xmm3
> +       pmovmskb %xmm3, %eax
> +       test    %eax, %eax
> +       jnz     L(matches32)
> +
> +       movdqa  48(%rdi), %xmm3
> +       pcmpeqb %xmm1, %xmm3
> +       pmovmskb %xmm3, %eax
> +
> +       add     $64, %rdi
> +       test    %eax, %eax
> +       jnz     L(matches0)
> +
> +       and     $-64, %rdi
> +
> +       .p2align 4
> +L(align64_loop):
> +       movdqa  (%rdi), %xmm0
> +       movdqa  16(%rdi), %xmm2
> +       movdqa  32(%rdi), %xmm3
> +       movdqa  48(%rdi), %xmm4
> +
> +       pcmpeqb %xmm1, %xmm0
> +       pcmpeqb %xmm1, %xmm2
> +       pcmpeqb %xmm1, %xmm3
> +       pcmpeqb %xmm1, %xmm4
> +
> +       pmaxub  %xmm0, %xmm3
> +       pmaxub  %xmm2, %xmm4
> +       pmaxub  %xmm3, %xmm4
> +       pmovmskb %xmm4, %eax
> +
> +       add     $64, %rdi
> +
> +       test    %eax, %eax
> +       jz      L(align64_loop)
> +
> +       sub     $64, %rdi
> +
> +       pmovmskb %xmm0, %eax
> +       test    %eax, %eax
> +       jnz     L(matches)
> +
> +       pmovmskb %xmm2, %eax
> +       test    %eax, %eax
> +       jnz     L(matches16)
> +
> +       movdqa  32(%rdi), %xmm3
> +       pcmpeqb %xmm1, %xmm3
> +
> +       pcmpeqb 48(%rdi), %xmm1
> +       pmovmskb %xmm3, %eax
> +       test    %eax, %eax
> +       jnz     L(matches32)
> +
> +       pmovmskb %xmm1, %eax
> +       bsf     %eax, %eax
> +       lea     48(%rdi, %rax), %rax
> +       ret
> +
> +       .p2align 4
> +L(matches0):
> +       bsf     %eax, %eax
> +       lea     -16(%rax, %rdi), %rax
> +       ret
> +
> +       .p2align 4
> +L(matches):
> +       bsf     %eax, %eax
> +       add     %rdi, %rax
> +       ret
> +
> +       .p2align 4
> +L(matches16):
> +       bsf     %eax, %eax
> +       lea     16(%rax, %rdi), %rax
> +       ret
> +
> +       .p2align 4
> +L(matches32):
> +       bsf     %eax, %eax
> +       lea     32(%rax, %rdi), %rax
> +       ret
> +
> +END (RAWMEMCHR)
> +#endif
> diff --git a/sysdeps/x86_64/multiarch/rtld-memchr.S b/sysdeps/x86_64/multiarch/rtld-memchr.S
> new file mode 100644
> index 0000000000..a14b192bed
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/rtld-memchr.S
> @@ -0,0 +1,18 @@
> +/* Copyright (C) 2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include "../memchr.S"
> diff --git a/sysdeps/x86_64/multiarch/rtld-rawmemchr.S b/sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> new file mode 100644
> index 0000000000..5d4110a052
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> @@ -0,0 +1,18 @@
> +/* Copyright (C) 2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include "../rawmemchr.S"
> diff --git a/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S b/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> index 58ed21db01..2a1cff5b05 100644
> --- a/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> +++ b/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> @@ -1,4 +1,7 @@
> -#define MEMCHR __wmemchr_avx2_rtm
> -#define USE_AS_WMEMCHR 1
> +#ifndef WMEMCHR
> +# define WMEMCHR       __wmemchr_avx2_rtm
> +#endif
> +#define USE_AS_WMEMCHR 1
> +#define MEMCHR WMEMCHR
>
>  #include "memchr-avx2-rtm.S"
> diff --git a/sysdeps/x86_64/multiarch/wmemchr-avx2.S b/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> index 282854f1a1..2bf93fd84b 100644
> --- a/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> +++ b/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> @@ -1,4 +1,7 @@
> -#define MEMCHR __wmemchr_avx2
> -#define USE_AS_WMEMCHR 1
> +#ifndef WMEMCHR
> +# define WMEMCHR       __wmemchr_avx2
> +#endif
> +#define USE_AS_WMEMCHR 1
> +#define MEMCHR WMEMCHR
>
>  #include "memchr-avx2.S"
> diff --git a/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S b/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> index a346cd35a1..c67309e8a1 100644
> --- a/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> +++ b/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> @@ -1,3 +1,7 @@
> -#define MEMCHR __wmemchr_evex_rtm
> -#define USE_AS_WMEMCHR 1
> +#ifndef WMEMCHR
> +# define WMEMCHR       __wmemchr_evex_rtm
> +#endif
> +#define USE_AS_WMEMCHR 1
> +#define MEMCHR WMEMCHR
> +
>  #include "memchr-evex-rtm.S"
> diff --git a/sysdeps/x86_64/multiarch/wmemchr-evex.S b/sysdeps/x86_64/multiarch/wmemchr-evex.S
> index 06cd0f9f5a..5512d5cdc3 100644
> --- a/sysdeps/x86_64/multiarch/wmemchr-evex.S
> +++ b/sysdeps/x86_64/multiarch/wmemchr-evex.S
> @@ -1,4 +1,7 @@
> -#define MEMCHR __wmemchr_evex
> -#define USE_AS_WMEMCHR 1
> +#ifndef WMEMCHR
> +# define WMEMCHR       __wmemchr_evex
> +#endif
> +#define USE_AS_WMEMCHR 1
> +#define MEMCHR WMEMCHR
>
>  #include "memchr-evex.S"
> diff --git a/sysdeps/x86_64/multiarch/wmemchr-sse2.S b/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> index 70a965d552..b675a070d4 100644
> --- a/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> +++ b/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> @@ -1,4 +1,7 @@
> -#define USE_AS_WMEMCHR 1
> -#define wmemchr __wmemchr_sse2
> +#ifndef WMEMCHR
> +# define WMEMCHR       __wmemchr_sse2
> +#endif
> +#define USE_AS_WMEMCHR 1
> +#define MEMCHR WMEMCHR
>
> -#include "../memchr.S"
> +#include "memchr-sse2.S"
> diff --git a/sysdeps/x86_64/rawmemchr.S b/sysdeps/x86_64/rawmemchr.S
> index 4c1a3383b9..ba7e5202e6 100644
> --- a/sysdeps/x86_64/rawmemchr.S
> +++ b/sysdeps/x86_64/rawmemchr.S
> @@ -17,185 +17,13 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>
> -#include <sysdep.h>
> +#define RAWMEMCHR      __rawmemchr
>
> -       .text
> -ENTRY (__rawmemchr)
> -       movd    %rsi, %xmm1
> -       mov     %rdi, %rcx
> +#define DEFAULT_IMPL_V1        "multiarch/rawmemchr-sse2.S"
> +#define DEFAULT_IMPL_V3        "multiarch/rawmemchr-avx2.S"
> +#define DEFAULT_IMPL_V4        "multiarch/rawmemchr-evex.S"
>
> -       punpcklbw %xmm1, %xmm1
> -       punpcklbw %xmm1, %xmm1
> -
> -       and     $63, %rcx
> -       pshufd  $0, %xmm1, %xmm1
> -
> -       cmp     $48, %rcx
> -       ja      L(crosscache)
> -
> -       movdqu  (%rdi), %xmm0
> -       pcmpeqb %xmm1, %xmm0
> -/* Check if there is a match.  */
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -
> -       jnz     L(matches)
> -       add     $16, %rdi
> -       and     $-16, %rdi
> -       jmp     L(loop_prolog)
> -
> -       .p2align 4
> -L(crosscache):
> -       and     $15, %rcx
> -       and     $-16, %rdi
> -       movdqa  (%rdi), %xmm0
> -
> -       pcmpeqb %xmm1, %xmm0
> -/* Check if there is a match.  */
> -       pmovmskb %xmm0, %eax
> -/* Remove the leading bytes.  */
> -       sar     %cl, %eax
> -       test    %eax, %eax
> -       je      L(unaligned_no_match)
> -/* Check which byte is a match.  */
> -       bsf     %eax, %eax
> -
> -       add     %rdi, %rax
> -       add     %rcx, %rax
> -       ret
> -
> -       .p2align 4
> -L(unaligned_no_match):
> -       add     $16, %rdi
> -
> -       .p2align 4
> -L(loop_prolog):
> -       movdqa  (%rdi), %xmm0
> -       pcmpeqb %xmm1, %xmm0
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -       jnz     L(matches)
> -
> -       movdqa  16(%rdi), %xmm2
> -       pcmpeqb %xmm1, %xmm2
> -       pmovmskb %xmm2, %eax
> -       test    %eax, %eax
> -       jnz     L(matches16)
> -
> -       movdqa  32(%rdi), %xmm3
> -       pcmpeqb %xmm1, %xmm3
> -       pmovmskb %xmm3, %eax
> -       test    %eax, %eax
> -       jnz     L(matches32)
> -
> -       movdqa  48(%rdi), %xmm4
> -       pcmpeqb %xmm1, %xmm4
> -       add     $64, %rdi
> -       pmovmskb %xmm4, %eax
> -       test    %eax, %eax
> -       jnz     L(matches0)
> -
> -       test    $0x3f, %rdi
> -       jz      L(align64_loop)
> -
> -       movdqa  (%rdi), %xmm0
> -       pcmpeqb %xmm1, %xmm0
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -       jnz     L(matches)
> -
> -       movdqa  16(%rdi), %xmm2
> -       pcmpeqb %xmm1, %xmm2
> -       pmovmskb %xmm2, %eax
> -       test    %eax, %eax
> -       jnz     L(matches16)
> -
> -       movdqa  32(%rdi), %xmm3
> -       pcmpeqb %xmm1, %xmm3
> -       pmovmskb %xmm3, %eax
> -       test    %eax, %eax
> -       jnz     L(matches32)
> -
> -       movdqa  48(%rdi), %xmm3
> -       pcmpeqb %xmm1, %xmm3
> -       pmovmskb %xmm3, %eax
> -
> -       add     $64, %rdi
> -       test    %eax, %eax
> -       jnz     L(matches0)
> -
> -       and     $-64, %rdi
> -
> -       .p2align 4
> -L(align64_loop):
> -       movdqa  (%rdi), %xmm0
> -       movdqa  16(%rdi), %xmm2
> -       movdqa  32(%rdi), %xmm3
> -       movdqa  48(%rdi), %xmm4
> -
> -       pcmpeqb %xmm1, %xmm0
> -       pcmpeqb %xmm1, %xmm2
> -       pcmpeqb %xmm1, %xmm3
> -       pcmpeqb %xmm1, %xmm4
> -
> -       pmaxub  %xmm0, %xmm3
> -       pmaxub  %xmm2, %xmm4
> -       pmaxub  %xmm3, %xmm4
> -       pmovmskb %xmm4, %eax
> -
> -       add     $64, %rdi
> -
> -       test    %eax, %eax
> -       jz      L(align64_loop)
> -
> -       sub     $64, %rdi
> -
> -       pmovmskb %xmm0, %eax
> -       test    %eax, %eax
> -       jnz     L(matches)
> -
> -       pmovmskb %xmm2, %eax
> -       test    %eax, %eax
> -       jnz     L(matches16)
> -
> -       movdqa  32(%rdi), %xmm3
> -       pcmpeqb %xmm1, %xmm3
> -
> -       pcmpeqb 48(%rdi), %xmm1
> -       pmovmskb %xmm3, %eax
> -       test    %eax, %eax
> -       jnz     L(matches32)
> -
> -       pmovmskb %xmm1, %eax
> -       bsf     %eax, %eax
> -       lea     48(%rdi, %rax), %rax
> -       ret
> -
> -       .p2align 4
> -L(matches0):
> -       bsf     %eax, %eax
> -       lea     -16(%rax, %rdi), %rax
> -       ret
> -
> -       .p2align 4
> -L(matches):
> -       bsf     %eax, %eax
> -       add     %rdi, %rax
> -       ret
> -
> -       .p2align 4
> -L(matches16):
> -       bsf     %eax, %eax
> -       lea     16(%rax, %rdi), %rax
> -       ret
> -
> -       .p2align 4
> -L(matches32):
> -       bsf     %eax, %eax
> -       lea     32(%rax, %rdi), %rax
> -       ret
> -
> -END (__rawmemchr)
> +#include "isa-default-impl.h"
>
>  weak_alias (__rawmemchr, rawmemchr)
> -libc_hidden_builtin_def (__rawmemchr)
> +libc_hidden_def (__rawmemchr)
> diff --git a/sysdeps/x86_64/wmemchr.S b/sysdeps/x86_64/wmemchr.S
> new file mode 100644
> index 0000000000..eef91e556b
> --- /dev/null
> +++ b/sysdeps/x86_64/wmemchr.S
> @@ -0,0 +1,28 @@
> +/* Copyright (C) 2011-2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#define WMEMCHR        __wmemchr
> +
> +#define DEFAULT_IMPL_V1        "multiarch/wmemchr-sse2.S"
> +#define DEFAULT_IMPL_V3        "multiarch/wmemchr-avx2.S"
> +#define DEFAULT_IMPL_V4        "multiarch/wmemchr-evex.S"
> +
> +#include "isa-default-impl.h"
> +
> +libc_hidden_def (__wmemchr)
> +weak_alias (__wmemchr, wmemchr)
> +libc_hidden_weak (wmemchr)
> --
> 2.34.1
>

On Wed, Jun 22, 2022 at 2:52 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Wed, Jun 22, 2022 at 1:58 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > 1. Refactor files so that all implementations for in the multiarch
> >    directory.
> >     - Essentially moved sse2 {raw|w}memchr.S implementation to
> >       multiarch/{raw|w}memchr-sse2.S
> >
> >     - The non-multiarch {raw|w}memchr.S file now only includes one of
> >       the implementations in the multiarch directory based on the
> >       compiled ISA level (only used for non-multiarch builds.
> >       Otherwise we go through the ifunc selector).
> >
> > 2. Add ISA level build guards to different implementations.
> >     - I.e memchr-avx2.S which is ISA level 3 will only build if
> >       compiled ISA level <= 3. Otherwise there is no reason to include
> >       it as we will always use one of the ISA level 4
> >       implementations (memchr-evex{-rtm}.S).
> >
> > 3. Add new multiarch/rtld-{raw}memchr.S that just include the
> >    non-multiarch {raw}memchr.S which will in turn select the best
> >    implementation based on the compiled ISA level.
> >
> > 4. Refactor the ifunc selector and ifunc implementation list to use
> >    the ISA level aware wrapper macros that allow functions below the
> >    compiled ISA level (with a guranteed replacement) to be skipped.
> >     - Guranteed replacement essentially means that for any ISA level
> >       build there must be a function that the baseline of the ISA
> >       supports. So for {raw|w}memchr.S since there is not ISA level 2
> >       function, the ISA level 2 build still includes the ISA level
> >       1 (sse2) function. Once we reach the ISA level 3 build, however,
> >       {raw|w}memchr-avx2{-rtm}.S will always be sufficient so the ISA
> >       level 1 implementation ({raw|w}memchr-sse2.S) will not be built.
> >
> > Tested with and without multiarch on x86_64 for ISA levels:
> > {generic, x86-64-v2, x86-64-v3, x86-64-v4}
> >
> > And m32 with and without multiarch.
> > ---
> >  sysdeps/x86_64/isa-default-impl.h             |   8 +
> >  sysdeps/x86_64/memchr.S                       | 357 +----------------
> >  sysdeps/x86_64/multiarch/ifunc-evex.h         |  29 +-
> >  sysdeps/x86_64/multiarch/ifunc-impl-list.c    |  72 ++--
> >  sysdeps/x86_64/multiarch/memchr-avx2.S        |   5 +-
> >  sysdeps/x86_64/multiarch/memchr-evex.S        |   5 +-
> >  sysdeps/x86_64/multiarch/memchr-sse2.S        | 363 +++++++++++++++++-
> >  sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S |   7 +-
> >  sysdeps/x86_64/multiarch/rawmemchr-avx2.S     |   7 +-
> >  sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S |   8 +-
> >  sysdeps/x86_64/multiarch/rawmemchr-evex.S     |   7 +-
> >  sysdeps/x86_64/multiarch/rawmemchr-sse2.S     | 198 +++++++++-
> >  sysdeps/x86_64/multiarch/rtld-memchr.S        |  18 +
> >  sysdeps/x86_64/multiarch/rtld-rawmemchr.S     |  18 +
> >  sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S   |   7 +-
> >  sysdeps/x86_64/multiarch/wmemchr-avx2.S       |   7 +-
> >  sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S   |   8 +-
> >  sysdeps/x86_64/multiarch/wmemchr-evex.S       |   7 +-
> >  sysdeps/x86_64/multiarch/wmemchr-sse2.S       |   9 +-
> >  sysdeps/x86_64/rawmemchr.S                    | 184 +--------
> >  sysdeps/x86_64/wmemchr.S                      |  28 ++
> >  21 files changed, 740 insertions(+), 612 deletions(-)
> >  create mode 100644 sysdeps/x86_64/multiarch/rtld-memchr.S
> >  create mode 100644 sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> >  create mode 100644 sysdeps/x86_64/wmemchr.S
> >
> > diff --git a/sysdeps/x86_64/isa-default-impl.h b/sysdeps/x86_64/isa-default-impl.h
> > index 34634668e5..b374a38b8b 100644
> > --- a/sysdeps/x86_64/isa-default-impl.h
> > +++ b/sysdeps/x86_64/isa-default-impl.h
> > @@ -46,4 +46,12 @@
> >  # error "Unsupported ISA Level!"
> >  #endif
> >
> > +#if IS_IN(rtld) && !defined USE_MULTIARCH
> > +#  error "RTLD version should only exist in multiarch build"
> > +#endif
> > +
> > +#if defined USE_MULTIARCH && !IS_IN(rtld)
> > +#  error "Multiarch build should not use ISA_DEFAULT_IMPL without RTLD"
> > +#endif
>
> Please do
>
> #if IS_IN (rtld)
> #else
> #endif
>
> >  #include ISA_DEFAULT_IMPL
> > diff --git a/sysdeps/x86_64/memchr.S b/sysdeps/x86_64/memchr.S
> > index a160fd9b00..20b43508c4 100644
> > --- a/sysdeps/x86_64/memchr.S
> > +++ b/sysdeps/x86_64/memchr.S
> > @@ -15,358 +15,13 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#include <sysdep.h>
> > +#define MEMCHR __memchr
> >
> > -#ifdef USE_AS_WMEMCHR
> > -# define MEMCHR                wmemchr
> > -# define PCMPEQ                pcmpeqd
> > -# define CHAR_PER_VEC  4
> > -#else
> > -# define MEMCHR                memchr
> > -# define PCMPEQ                pcmpeqb
> > -# define CHAR_PER_VEC  16
> > -#endif
> > +#define DEFAULT_IMPL_V1        "multiarch/memchr-sse2.S"
> > +#define DEFAULT_IMPL_V3        "multiarch/memchr-avx2.S"
> > +#define DEFAULT_IMPL_V4        "multiarch/memchr-evex.S"
> >
> > -/* fast SSE2 version with using pmaxub and 64 byte loop */
> > +#include "isa-default-impl.h"
> >
> > -       .text
> > -ENTRY(MEMCHR)
> > -       movd    %esi, %xmm1
> > -       mov     %edi, %ecx
> > -
> > -#ifdef __ILP32__
> > -       /* Clear the upper 32 bits.  */
> > -       movl    %edx, %edx
> > -#endif
> > -#ifdef USE_AS_WMEMCHR
> > -       test    %RDX_LP, %RDX_LP
> > -       jz      L(return_null)
> > -#else
> > -       punpcklbw %xmm1, %xmm1
> > -       test    %RDX_LP, %RDX_LP
> > -       jz      L(return_null)
> > -       punpcklbw %xmm1, %xmm1
> > -#endif
> > -
> > -       and     $63, %ecx
> > -       pshufd  $0, %xmm1, %xmm1
> > -
> > -       cmp     $48, %ecx
> > -       ja      L(crosscache)
> > -
> > -       movdqu  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -
> > -       jnz     L(matches_1)
> > -       sub     $CHAR_PER_VEC, %rdx
> > -       jbe     L(return_null)
> > -       add     $16, %rdi
> > -       and     $15, %ecx
> > -       and     $-16, %rdi
> > -#ifdef USE_AS_WMEMCHR
> > -       shr     $2, %ecx
> > -#endif
> > -       add     %rcx, %rdx
> > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > -       jbe     L(exit_loop)
> > -       jmp     L(loop_prolog)
> > -
> > -       .p2align 4
> > -L(crosscache):
> > -       and     $15, %ecx
> > -       and     $-16, %rdi
> > -       movdqa  (%rdi), %xmm0
> > -
> > -       PCMPEQ  %xmm1, %xmm0
> > -       /* Check if there is a match.  */
> > -       pmovmskb %xmm0, %eax
> > -       /* Remove the leading bytes.  */
> > -       sar     %cl, %eax
> > -       test    %eax, %eax
> > -       je      L(unaligned_no_match)
> > -       /* Check which byte is a match.  */
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       add     %rdi, %rax
> > -       add     %rcx, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(unaligned_no_match):
> > -       /* "rcx" is less than 16.  Calculate "rdx + rcx - 16" by using
> > -          "rdx - (16 - rcx)" instead of "(rdx + rcx) - 16" to void
> > -          possible addition overflow.  */
> > -       neg     %rcx
> > -       add     $16, %rcx
> > -#ifdef USE_AS_WMEMCHR
> > -       shr     $2, %ecx
> > -#endif
> > -       sub     %rcx, %rdx
> > -       jbe     L(return_null)
> > -       add     $16, %rdi
> > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > -       jbe     L(exit_loop)
> > -
> > -       .p2align 4
> > -L(loop_prolog):
> > -       movdqa  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       PCMPEQ  %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       movdqa  48(%rdi), %xmm4
> > -       PCMPEQ  %xmm1, %xmm4
> > -       add     $64, %rdi
> > -       pmovmskb %xmm4, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches0)
> > -
> > -       test    $0x3f, %rdi
> > -       jz      L(align64_loop)
> > -
> > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > -       jbe     L(exit_loop)
> > -
> > -       movdqa  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       PCMPEQ  %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       movdqa  48(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -
> > -       add     $64, %rdi
> > -       test    %eax, %eax
> > -       jnz     L(matches0)
> > -
> > -       mov     %rdi, %rcx
> > -       and     $-64, %rdi
> > -       and     $63, %ecx
> > -#ifdef USE_AS_WMEMCHR
> > -       shr     $2, %ecx
> > -#endif
> > -       add     %rcx, %rdx
> > -
> > -       .p2align 4
> > -L(align64_loop):
> > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > -       jbe     L(exit_loop)
> > -       movdqa  (%rdi), %xmm0
> > -       movdqa  16(%rdi), %xmm2
> > -       movdqa  32(%rdi), %xmm3
> > -       movdqa  48(%rdi), %xmm4
> > -
> > -       PCMPEQ  %xmm1, %xmm0
> > -       PCMPEQ  %xmm1, %xmm2
> > -       PCMPEQ  %xmm1, %xmm3
> > -       PCMPEQ  %xmm1, %xmm4
> > -
> > -       pmaxub  %xmm0, %xmm3
> > -       pmaxub  %xmm2, %xmm4
> > -       pmaxub  %xmm3, %xmm4
> > -       pmovmskb %xmm4, %eax
> > -
> > -       add     $64, %rdi
> > -
> > -       test    %eax, %eax
> > -       jz      L(align64_loop)
> > -
> > -       sub     $64, %rdi
> > -
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -
> > -       PCMPEQ  48(%rdi), %xmm1
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       pmovmskb %xmm1, %eax
> > -       bsf     %eax, %eax
> > -       lea     48(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(exit_loop):
> > -       add     $(CHAR_PER_VEC * 2), %edx
> > -       jle     L(exit_loop_32)
> > -
> > -       movdqa  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       PCMPEQ  %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32_1)
> > -       sub     $CHAR_PER_VEC, %edx
> > -       jle     L(return_null)
> > -
> > -       PCMPEQ  48(%rdi), %xmm1
> > -       pmovmskb %xmm1, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches48_1)
> > -       xor     %eax, %eax
> > -       ret
> > -
> > -       .p2align 4
> > -L(exit_loop_32):
> > -       add     $(CHAR_PER_VEC * 2), %edx
> > -       movdqa  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches_1)
> > -       sub     $CHAR_PER_VEC, %edx
> > -       jbe     L(return_null)
> > -
> > -       PCMPEQ  16(%rdi), %xmm1
> > -       pmovmskb %xmm1, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16_1)
> > -       xor     %eax, %eax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches0):
> > -       bsf     %eax, %eax
> > -       lea     -16(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches):
> > -       bsf     %eax, %eax
> > -       add     %rdi, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches16):
> > -       bsf     %eax, %eax
> > -       lea     16(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches32):
> > -       bsf     %eax, %eax
> > -       lea     32(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches_1):
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       add     %rdi, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches16_1):
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       lea     16(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches32_1):
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       lea     32(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches48_1):
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       lea     48(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(return_null):
> > -       xor     %eax, %eax
> > -       ret
> > -END(MEMCHR)
> > -
> > -#ifndef USE_AS_WMEMCHR
> > -strong_alias (memchr, __memchr)
> > +weak_alias (__memchr, memchr)
> >  libc_hidden_builtin_def(memchr)
> > -#endif
> > diff --git a/sysdeps/x86_64/multiarch/ifunc-evex.h b/sysdeps/x86_64/multiarch/ifunc-evex.h
> > index b8f7a12ea2..856c6261f8 100644
> > --- a/sysdeps/x86_64/multiarch/ifunc-evex.h
> > +++ b/sysdeps/x86_64/multiarch/ifunc-evex.h
> > @@ -19,24 +19,28 @@
> >
> >  #include <init-arch.h>
> >
> > -extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
> > -extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> > -extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
> >  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;
> >  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex_rtm) attribute_hidden;
> >
> > +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> > +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
> > +
> > +extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
> >
> >  static inline void *
> >  IFUNC_SELECTOR (void)
> >  {
> > -  const struct cpu_features* cpu_features = __get_cpu_features ();
> > -
> > -  if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> > -      && CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> > -      && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
> > +  const struct cpu_features *cpu_features = __get_cpu_features ();
> > +
> > +  /* NB: The X86_ISA_* feature check macros are evaluated at
> > +     compile time.  */
> > +  if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> > +      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> > +      && X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> > +                                     AVX_Fast_Unaligned_Load))
> >      {
> > -      if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
> > -         && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
> > +      if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
> > +         && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
> >         {
> >           if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
> >             return OPTIMIZE (evex_rtm);
> > @@ -47,9 +51,12 @@ IFUNC_SELECTOR (void)
> >        if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
> >         return OPTIMIZE (avx2_rtm);
> >
> > -      if (!CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_VZEROUPPER))
> > +      if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> > +                                      Prefer_No_VZEROUPPER))
> >         return OPTIMIZE (avx2);
> >      }
> >
> > +  /* This is unreachable (compile time checked) if ISA level >= 3
> > +     so no need for a robust fallback here.  */
> >    return OPTIMIZE (sse2);
> >  }
> > diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > index 883362f63d..bf52cf96d0 100644
> > --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > @@ -25,7 +25,8 @@
> >
> >  /* Fill ARRAY of MAX elements with IFUNC implementations for function
> >     NAME supported on target machine and return the number of valid
> > -   entries.  */
> > +   entries.  Each set of implementations for a given function is sorted in
> > +   descending order by ISA level.  */
> >
> >  size_t
> >  __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > @@ -53,24 +54,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> >
> >    /* Support sysdeps/x86_64/multiarch/memchr.c.  */
> >    IFUNC_IMPL (i, name, memchr,
> > -             IFUNC_IMPL_ADD (array, i, memchr,
> > -                             CPU_FEATURE_USABLE (AVX2),
> > -                             __memchr_avx2)
> > -             IFUNC_IMPL_ADD (array, i, memchr,
> > -                             (CPU_FEATURE_USABLE (AVX2)
> > -                              && CPU_FEATURE_USABLE (RTM)),
> > -                             __memchr_avx2_rtm)
> > -             IFUNC_IMPL_ADD (array, i, memchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, memchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __memchr_evex)
> > -             IFUNC_IMPL_ADD (array, i, memchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, memchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __memchr_evex_rtm)
> > -             IFUNC_IMPL_ADD (array, i, memchr, 1, __memchr_sse2))
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, memchr,
> > +                             CPU_FEATURE_USABLE (AVX2),
> > +                             __memchr_avx2)
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, memchr,
> > +                             (CPU_FEATURE_USABLE (AVX2)
> > +                              && CPU_FEATURE_USABLE (RTM)),
> > +                             __memchr_avx2_rtm)
> > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > +             X86_IFUNC_IMPL_ADD_V2 (array, i, memchr,
> > +                             1,
> > +                             __memchr_sse2))
> >
> >    /* Support sysdeps/x86_64/multiarch/memcmp.c.  */
> >    IFUNC_IMPL (i, name, memcmp,
> > @@ -288,24 +292,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> >
> >    /* Support sysdeps/x86_64/multiarch/rawmemchr.c.  */
> >    IFUNC_IMPL (i, name, rawmemchr,
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > -                             CPU_FEATURE_USABLE (AVX2),
> > -                             __rawmemchr_avx2)
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > -                             (CPU_FEATURE_USABLE (AVX2)
> > -                              && CPU_FEATURE_USABLE (RTM)),
> > -                             __rawmemchr_avx2_rtm)
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, rawmemchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __rawmemchr_evex)
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, rawmemchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __rawmemchr_evex_rtm)
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr, 1, __rawmemchr_sse2))
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, rawmemchr,
> > +                             CPU_FEATURE_USABLE (AVX2),
> > +                             __rawmemchr_avx2)
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, rawmemchr,
> > +                             (CPU_FEATURE_USABLE (AVX2)
> > +                              && CPU_FEATURE_USABLE (RTM)),
> > +                             __rawmemchr_avx2_rtm)
> > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > +             X86_IFUNC_IMPL_ADD_V2 (array, i, rawmemchr,
> > +                             1,
> > +                             __rawmemchr_sse2))
> >
> >    /* Support sysdeps/x86_64/multiarch/strlen.c.  */
> >    IFUNC_IMPL (i, name, strlen,
> > @@ -748,24 +755,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> >
> >    /* Support sysdeps/x86_64/multiarch/wmemchr.c.  */
> >    IFUNC_IMPL (i, name, wmemchr,
> > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > -                             CPU_FEATURE_USABLE (AVX2),
> > -                             __wmemchr_avx2)
> > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > -                             (CPU_FEATURE_USABLE (AVX2)
> > -                              && CPU_FEATURE_USABLE (RTM)),
> > -                             __wmemchr_avx2_rtm)
> > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, wmemchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __wmemchr_evex)
> > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, wmemchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __wmemchr_evex_rtm)
> > -             IFUNC_IMPL_ADD (array, i, wmemchr, 1, __wmemchr_sse2))
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, wmemchr,
> > +                             CPU_FEATURE_USABLE (AVX2),
> > +                             __wmemchr_avx2)
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, wmemchr,
> > +                             (CPU_FEATURE_USABLE (AVX2)
> > +                              && CPU_FEATURE_USABLE (RTM)),
> > +                             __wmemchr_avx2_rtm)
> > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > +             X86_IFUNC_IMPL_ADD_V2 (array, i, wmemchr,
> > +                             1,
> > +                             __wmemchr_sse2))
> >
> >    /* Support sysdeps/x86_64/multiarch/wmemcmp.c.  */
> >    IFUNC_IMPL (i, name, wmemcmp,
> > diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S
> > index c5a256eb37..39be5f7083 100644
> > --- a/sysdeps/x86_64/multiarch/memchr-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/memchr-avx2.S
> > @@ -16,9 +16,10 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#if IS_IN (libc)
> > +#include <isa-level.h>
> > +#include <sysdep.h>
> >
> > -# include <sysdep.h>
> > +#if ISA_SHOULD_BUILD (3)
> >
> >  # ifndef MEMCHR
> >  #  define MEMCHR       __memchr_avx2
> > diff --git a/sysdeps/x86_64/multiarch/memchr-evex.S b/sysdeps/x86_64/multiarch/memchr-evex.S
> > index 0fd11b7632..0dd4f1dcce 100644
> > --- a/sysdeps/x86_64/multiarch/memchr-evex.S
> > +++ b/sysdeps/x86_64/multiarch/memchr-evex.S
> > @@ -16,9 +16,10 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#if IS_IN (libc)
> > +#include <isa-level.h>
> > +#include <sysdep.h>
> >
> > -# include <sysdep.h>
> > +#if ISA_SHOULD_BUILD (4)
> >
> >  # ifndef MEMCHR
> >  #  define MEMCHR       __memchr_evex
> > diff --git a/sysdeps/x86_64/multiarch/memchr-sse2.S b/sysdeps/x86_64/multiarch/memchr-sse2.S
> > index 2c6fdd41d6..8c561cd687 100644
> > --- a/sysdeps/x86_64/multiarch/memchr-sse2.S
> > +++ b/sysdeps/x86_64/multiarch/memchr-sse2.S
> > @@ -16,13 +16,360 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#if IS_IN (libc)
> > -# define memchr __memchr_sse2
> > +#include <isa-level.h>
> > +#include <sysdep.h>
> >
> > -# undef strong_alias
> > -# define strong_alias(memchr, __memchr)
> > -# undef libc_hidden_builtin_def
> > -# define libc_hidden_builtin_def(memchr)
> > -#endif
> > +/* MINIMUM_X86_ISA_LEVEL <= 2 because there is no V2 implementation
> > +   so we need this to build for ISA V2 builds. */
> > +#if ISA_SHOULD_BUILD (2)
> > +
> > +# ifndef MEMCHR
> > +#  define MEMCHR       __memchr_sse2
> > +# endif
> > +# ifdef USE_AS_WMEMCHR
> > +#  define PCMPEQ               pcmpeqd
> > +#  define CHAR_PER_VEC 4
> > +# else
> > +#  define PCMPEQ               pcmpeqb
> > +#  define CHAR_PER_VEC 16
> > +# endif
> > +
> > +/* fast SSE2 version with using pmaxub and 64 byte loop */
> > +
> > +       .text
> > +ENTRY(MEMCHR)
> > +       movd    %esi, %xmm1
> > +       mov     %edi, %ecx
> > +
> > +# ifdef __ILP32__
> > +       /* Clear the upper 32 bits.  */
> > +       movl    %edx, %edx
> > +# endif
> > +# ifdef USE_AS_WMEMCHR
> > +       test    %RDX_LP, %RDX_LP
> > +       jz      L(return_null)
> > +# else
> > +       punpcklbw %xmm1, %xmm1
> > +       test    %RDX_LP, %RDX_LP
> > +       jz      L(return_null)
> > +       punpcklbw %xmm1, %xmm1
> > +# endif
> > +
> > +       and     $63, %ecx
> > +       pshufd  $0, %xmm1, %xmm1
> > +
> > +       cmp     $48, %ecx
> > +       ja      L(crosscache)
> > +
> > +       movdqu  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +
> > +       jnz     L(matches_1)
> > +       sub     $CHAR_PER_VEC, %rdx
> > +       jbe     L(return_null)
> > +       add     $16, %rdi
> > +       and     $15, %ecx
> > +       and     $-16, %rdi
> > +# ifdef USE_AS_WMEMCHR
> > +       shr     $2, %ecx
> > +# endif
> > +       add     %rcx, %rdx
> > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > +       jbe     L(exit_loop)
> > +       jmp     L(loop_prolog)
> > +
> > +       .p2align 4
> > +L(crosscache):
> > +       and     $15, %ecx
> > +       and     $-16, %rdi
> > +       movdqa  (%rdi), %xmm0
> > +
> > +       PCMPEQ  %xmm1, %xmm0
> > +       /* Check if there is a match.  */
> > +       pmovmskb %xmm0, %eax
> > +       /* Remove the leading bytes.  */
> > +       sar     %cl, %eax
> > +       test    %eax, %eax
> > +       je      L(unaligned_no_match)
> > +       /* Check which byte is a match.  */
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       add     %rdi, %rax
> > +       add     %rcx, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(unaligned_no_match):
> > +       /* "rcx" is less than 16.  Calculate "rdx + rcx - 16" by using
> > +          "rdx - (16 - rcx)" instead of "(rdx + rcx) - 16" to void
> > +          possible addition overflow.  */
> > +       neg     %rcx
> > +       add     $16, %rcx
> > +# ifdef USE_AS_WMEMCHR
> > +       shr     $2, %ecx
> > +# endif
> > +       sub     %rcx, %rdx
> > +       jbe     L(return_null)
> > +       add     $16, %rdi
> > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > +       jbe     L(exit_loop)
> > +
> > +       .p2align 4
> > +L(loop_prolog):
> > +       movdqa  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       PCMPEQ  %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       movdqa  48(%rdi), %xmm4
> > +       PCMPEQ  %xmm1, %xmm4
> > +       add     $64, %rdi
> > +       pmovmskb %xmm4, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches0)
> > +
> > +       test    $0x3f, %rdi
> > +       jz      L(align64_loop)
> > +
> > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > +       jbe     L(exit_loop)
> > +
> > +       movdqa  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       PCMPEQ  %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       movdqa  48(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +
> > +       add     $64, %rdi
> > +       test    %eax, %eax
> > +       jnz     L(matches0)
> > +
> > +       mov     %rdi, %rcx
> > +       and     $-64, %rdi
> > +       and     $63, %ecx
> > +# ifdef USE_AS_WMEMCHR
> > +       shr     $2, %ecx
> > +# endif
> > +       add     %rcx, %rdx
> > +
> > +       .p2align 4
> > +L(align64_loop):
> > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > +       jbe     L(exit_loop)
> > +       movdqa  (%rdi), %xmm0
> > +       movdqa  16(%rdi), %xmm2
> > +       movdqa  32(%rdi), %xmm3
> > +       movdqa  48(%rdi), %xmm4
> > +
> > +       PCMPEQ  %xmm1, %xmm0
> > +       PCMPEQ  %xmm1, %xmm2
> > +       PCMPEQ  %xmm1, %xmm3
> > +       PCMPEQ  %xmm1, %xmm4
> >
> > -#include "../memchr.S"
> > +       pmaxub  %xmm0, %xmm3
> > +       pmaxub  %xmm2, %xmm4
> > +       pmaxub  %xmm3, %xmm4
> > +       pmovmskb %xmm4, %eax
> > +
> > +       add     $64, %rdi
> > +
> > +       test    %eax, %eax
> > +       jz      L(align64_loop)
> > +
> > +       sub     $64, %rdi
> > +
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +
> > +       PCMPEQ  48(%rdi), %xmm1
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       pmovmskb %xmm1, %eax
> > +       bsf     %eax, %eax
> > +       lea     48(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(exit_loop):
> > +       add     $(CHAR_PER_VEC * 2), %edx
> > +       jle     L(exit_loop_32)
> > +
> > +       movdqa  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       PCMPEQ  %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32_1)
> > +       sub     $CHAR_PER_VEC, %edx
> > +       jle     L(return_null)
> > +
> > +       PCMPEQ  48(%rdi), %xmm1
> > +       pmovmskb %xmm1, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches48_1)
> > +       xor     %eax, %eax
> > +       ret
> > +
> > +       .p2align 4
> > +L(exit_loop_32):
> > +       add     $(CHAR_PER_VEC * 2), %edx
> > +       movdqa  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches_1)
> > +       sub     $CHAR_PER_VEC, %edx
> > +       jbe     L(return_null)
> > +
> > +       PCMPEQ  16(%rdi), %xmm1
> > +       pmovmskb %xmm1, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16_1)
> > +       xor     %eax, %eax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches0):
> > +       bsf     %eax, %eax
> > +       lea     -16(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches):
> > +       bsf     %eax, %eax
> > +       add     %rdi, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches16):
> > +       bsf     %eax, %eax
> > +       lea     16(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches32):
> > +       bsf     %eax, %eax
> > +       lea     32(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches_1):
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       add     %rdi, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches16_1):
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       lea     16(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches32_1):
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       lea     32(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches48_1):
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       lea     48(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(return_null):
> > +       xor     %eax, %eax
> > +       ret
> > +END(MEMCHR)
> > +#endif
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S b/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > index acc5f6e2fb..5c1dcd3ca7 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __rawmemchr_avx2_rtm
> > -#define USE_AS_RAWMEMCHR 1
> > +#ifndef RAWMEMCHR
> > +# define RAWMEMCHR     __rawmemchr_avx2_rtm
> > +#endif
> > +#define USE_AS_RAWMEMCHR       1
> > +#define MEMCHR RAWMEMCHR
> >
> >  #include "memchr-avx2-rtm.S"
>
> Will we ever use the RTM version as the default?

We had talked about it and agreed not to. I think we can
safely say we don't need it for the RTLD default because
we know no transactions.

As for the non-multiarch build selection it's a bit more ambiguous.

>
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-avx2.S b/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > index 128f9ea637..d6bff28757 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __rawmemchr_avx2
> > -#define USE_AS_RAWMEMCHR 1
> > +#ifndef RAWMEMCHR
> > +# define RAWMEMCHR     __rawmemchr_avx2
> > +#endif
> > +#define USE_AS_RAWMEMCHR       1
> > +#define MEMCHR RAWMEMCHR
> >
> >  #include "memchr-avx2.S"
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S b/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > index deda1ca395..8ff7f27c9c 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > @@ -1,3 +1,7 @@
> > -#define MEMCHR __rawmemchr_evex_rtm
> > -#define USE_AS_RAWMEMCHR 1
> > +#ifndef RAWMEMCHR
> > +# define RAWMEMCHR     __rawmemchr_evex_rtm
> > +#endif
> > +#define USE_AS_RAWMEMCHR       1
> > +#define MEMCHR RAWMEMCHR
> > +
>
> Will we ever use the RTM version as the default?
>
> >  #include "memchr-evex-rtm.S"
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-evex.S b/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > index ec942b77ba..dc1c450699 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __rawmemchr_evex
> > -#define USE_AS_RAWMEMCHR 1
> > +#ifndef RAWMEMCHR
> > +# define RAWMEMCHR     __rawmemchr_evex
> > +#endif
> > +#define USE_AS_RAWMEMCHR       1
> > +#define MEMCHR RAWMEMCHR
> >
> >  #include "memchr-evex.S"
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-sse2.S b/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > index 3841c14c34..e2c2e20d85 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > @@ -16,14 +16,192 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -/* Define multiple versions only for the definition in libc. */
> > -#if IS_IN (libc)
> > -# define __rawmemchr __rawmemchr_sse2
> > -
> > -# undef weak_alias
> > -# define weak_alias(__rawmemchr, rawmemchr)
> > -# undef libc_hidden_def
> > -# define libc_hidden_def(__rawmemchr)
> > -#endif
> > +#include <isa-level.h>
> > +#include <sysdep.h>
> > +
> > +/* MINIMUM_X86_ISA_LEVEL <= 2 because there is no V2 implementation
> > +   so we need this to build for ISA V2 builds. */
> > +#if ISA_SHOULD_BUILD (2)
> > +
> > +# ifndef RAWMEMCHR
> > +#  define RAWMEMCHR    __rawmemchr_sse2
> > +# endif
> > +
> > +       .text
> > +ENTRY (RAWMEMCHR)
> > +       movd    %rsi, %xmm1
> > +       mov     %rdi, %rcx
> > +
> > +       punpcklbw %xmm1, %xmm1
> > +       punpcklbw %xmm1, %xmm1
> > +
> > +       and     $63, %rcx
> > +       pshufd  $0, %xmm1, %xmm1
> > +
> > +       cmp     $48, %rcx
> > +       ja      L(crosscache)
> > +
> > +       movdqu  (%rdi), %xmm0
> > +       pcmpeqb %xmm1, %xmm0
> > +/* Check if there is a match.  */
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +
> > +       jnz     L(matches)
> > +       add     $16, %rdi
> > +       and     $-16, %rdi
> > +       jmp     L(loop_prolog)
> > +
> > +       .p2align 4
> > +L(crosscache):
> > +       and     $15, %rcx
> > +       and     $-16, %rdi
> > +       movdqa  (%rdi), %xmm0
> > +
> > +       pcmpeqb %xmm1, %xmm0
> > +/* Check if there is a match.  */
> > +       pmovmskb %xmm0, %eax
> > +/* Remove the leading bytes.  */
> > +       sar     %cl, %eax
> > +       test    %eax, %eax
> > +       je      L(unaligned_no_match)
> > +/* Check which byte is a match.  */
> > +       bsf     %eax, %eax
> > +
> > +       add     %rdi, %rax
> > +       add     %rcx, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(unaligned_no_match):
> > +       add     $16, %rdi
> > +
> > +       .p2align 4
> > +L(loop_prolog):
> > +       movdqa  (%rdi), %xmm0
> > +       pcmpeqb %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       pcmpeqb %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       pcmpeqb %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       movdqa  48(%rdi), %xmm4
> > +       pcmpeqb %xmm1, %xmm4
> > +       add     $64, %rdi
> > +       pmovmskb %xmm4, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches0)
> > +
> > +       test    $0x3f, %rdi
> > +       jz      L(align64_loop)
> > +
> > +       movdqa  (%rdi), %xmm0
> > +       pcmpeqb %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       pcmpeqb %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> >
> > -#include "../rawmemchr.S"
> > +       movdqa  32(%rdi), %xmm3
> > +       pcmpeqb %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       movdqa  48(%rdi), %xmm3
> > +       pcmpeqb %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +
> > +       add     $64, %rdi
> > +       test    %eax, %eax
> > +       jnz     L(matches0)
> > +
> > +       and     $-64, %rdi
> > +
> > +       .p2align 4
> > +L(align64_loop):
> > +       movdqa  (%rdi), %xmm0
> > +       movdqa  16(%rdi), %xmm2
> > +       movdqa  32(%rdi), %xmm3
> > +       movdqa  48(%rdi), %xmm4
> > +
> > +       pcmpeqb %xmm1, %xmm0
> > +       pcmpeqb %xmm1, %xmm2
> > +       pcmpeqb %xmm1, %xmm3
> > +       pcmpeqb %xmm1, %xmm4
> > +
> > +       pmaxub  %xmm0, %xmm3
> > +       pmaxub  %xmm2, %xmm4
> > +       pmaxub  %xmm3, %xmm4
> > +       pmovmskb %xmm4, %eax
> > +
> > +       add     $64, %rdi
> > +
> > +       test    %eax, %eax
> > +       jz      L(align64_loop)
> > +
> > +       sub     $64, %rdi
> > +
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       pcmpeqb %xmm1, %xmm3
> > +
> > +       pcmpeqb 48(%rdi), %xmm1
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       pmovmskb %xmm1, %eax
> > +       bsf     %eax, %eax
> > +       lea     48(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches0):
> > +       bsf     %eax, %eax
> > +       lea     -16(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches):
> > +       bsf     %eax, %eax
> > +       add     %rdi, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches16):
> > +       bsf     %eax, %eax
> > +       lea     16(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches32):
> > +       bsf     %eax, %eax
> > +       lea     32(%rax, %rdi), %rax
> > +       ret
> > +
> > +END (RAWMEMCHR)
> > +#endif
> > diff --git a/sysdeps/x86_64/multiarch/rtld-memchr.S b/sysdeps/x86_64/multiarch/rtld-memchr.S
> > new file mode 100644
> > index 0000000000..a14b192bed
> > --- /dev/null
> > +++ b/sysdeps/x86_64/multiarch/rtld-memchr.S
> > @@ -0,0 +1,18 @@
> > +/* Copyright (C) 2022 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#include "../memchr.S"
> > diff --git a/sysdeps/x86_64/multiarch/rtld-rawmemchr.S b/sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> > new file mode 100644
> > index 0000000000..5d4110a052
> > --- /dev/null
> > +++ b/sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> > @@ -0,0 +1,18 @@
> > +/* Copyright (C) 2022 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#include "../rawmemchr.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S b/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > index 58ed21db01..2a1cff5b05 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __wmemchr_avx2_rtm
> > -#define USE_AS_WMEMCHR 1
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_avx2_rtm
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> >
> >  #include "memchr-avx2-rtm.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-avx2.S b/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > index 282854f1a1..2bf93fd84b 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __wmemchr_avx2
> > -#define USE_AS_WMEMCHR 1
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_avx2
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> >
> >  #include "memchr-avx2.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S b/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > index a346cd35a1..c67309e8a1 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > @@ -1,3 +1,7 @@
> > -#define MEMCHR __wmemchr_evex_rtm
> > -#define USE_AS_WMEMCHR 1
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_evex_rtm
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> > +
> >  #include "memchr-evex-rtm.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-evex.S b/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > index 06cd0f9f5a..5512d5cdc3 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __wmemchr_evex
> > -#define USE_AS_WMEMCHR 1
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_evex
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> >
> >  #include "memchr-evex.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-sse2.S b/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > index 70a965d552..b675a070d4 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > @@ -1,4 +1,7 @@
> > -#define USE_AS_WMEMCHR 1
> > -#define wmemchr __wmemchr_sse2
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_sse2
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> >
> > -#include "../memchr.S"
> > +#include "memchr-sse2.S"
> > diff --git a/sysdeps/x86_64/rawmemchr.S b/sysdeps/x86_64/rawmemchr.S
> > index 4c1a3383b9..ba7e5202e6 100644
> > --- a/sysdeps/x86_64/rawmemchr.S
> > +++ b/sysdeps/x86_64/rawmemchr.S
> > @@ -17,185 +17,13 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#include <sysdep.h>
> > +#define RAWMEMCHR      __rawmemchr
> >
> > -       .text
> > -ENTRY (__rawmemchr)
> > -       movd    %rsi, %xmm1
> > -       mov     %rdi, %rcx
> > +#define DEFAULT_IMPL_V1        "multiarch/rawmemchr-sse2.S"
> > +#define DEFAULT_IMPL_V3        "multiarch/rawmemchr-avx2.S"
> > +#define DEFAULT_IMPL_V4        "multiarch/rawmemchr-evex.S"
> >
> > -       punpcklbw %xmm1, %xmm1
> > -       punpcklbw %xmm1, %xmm1
> > -
> > -       and     $63, %rcx
> > -       pshufd  $0, %xmm1, %xmm1
> > -
> > -       cmp     $48, %rcx
> > -       ja      L(crosscache)
> > -
> > -       movdqu  (%rdi), %xmm0
> > -       pcmpeqb %xmm1, %xmm0
> > -/* Check if there is a match.  */
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -
> > -       jnz     L(matches)
> > -       add     $16, %rdi
> > -       and     $-16, %rdi
> > -       jmp     L(loop_prolog)
> > -
> > -       .p2align 4
> > -L(crosscache):
> > -       and     $15, %rcx
> > -       and     $-16, %rdi
> > -       movdqa  (%rdi), %xmm0
> > -
> > -       pcmpeqb %xmm1, %xmm0
> > -/* Check if there is a match.  */
> > -       pmovmskb %xmm0, %eax
> > -/* Remove the leading bytes.  */
> > -       sar     %cl, %eax
> > -       test    %eax, %eax
> > -       je      L(unaligned_no_match)
> > -/* Check which byte is a match.  */
> > -       bsf     %eax, %eax
> > -
> > -       add     %rdi, %rax
> > -       add     %rcx, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(unaligned_no_match):
> > -       add     $16, %rdi
> > -
> > -       .p2align 4
> > -L(loop_prolog):
> > -       movdqa  (%rdi), %xmm0
> > -       pcmpeqb %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       pcmpeqb %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       pcmpeqb %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       movdqa  48(%rdi), %xmm4
> > -       pcmpeqb %xmm1, %xmm4
> > -       add     $64, %rdi
> > -       pmovmskb %xmm4, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches0)
> > -
> > -       test    $0x3f, %rdi
> > -       jz      L(align64_loop)
> > -
> > -       movdqa  (%rdi), %xmm0
> > -       pcmpeqb %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       pcmpeqb %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       pcmpeqb %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       movdqa  48(%rdi), %xmm3
> > -       pcmpeqb %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -
> > -       add     $64, %rdi
> > -       test    %eax, %eax
> > -       jnz     L(matches0)
> > -
> > -       and     $-64, %rdi
> > -
> > -       .p2align 4
> > -L(align64_loop):
> > -       movdqa  (%rdi), %xmm0
> > -       movdqa  16(%rdi), %xmm2
> > -       movdqa  32(%rdi), %xmm3
> > -       movdqa  48(%rdi), %xmm4
> > -
> > -       pcmpeqb %xmm1, %xmm0
> > -       pcmpeqb %xmm1, %xmm2
> > -       pcmpeqb %xmm1, %xmm3
> > -       pcmpeqb %xmm1, %xmm4
> > -
> > -       pmaxub  %xmm0, %xmm3
> > -       pmaxub  %xmm2, %xmm4
> > -       pmaxub  %xmm3, %xmm4
> > -       pmovmskb %xmm4, %eax
> > -
> > -       add     $64, %rdi
> > -
> > -       test    %eax, %eax
> > -       jz      L(align64_loop)
> > -
> > -       sub     $64, %rdi
> > -
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       pcmpeqb %xmm1, %xmm3
> > -
> > -       pcmpeqb 48(%rdi), %xmm1
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       pmovmskb %xmm1, %eax
> > -       bsf     %eax, %eax
> > -       lea     48(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches0):
> > -       bsf     %eax, %eax
> > -       lea     -16(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches):
> > -       bsf     %eax, %eax
> > -       add     %rdi, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches16):
> > -       bsf     %eax, %eax
> > -       lea     16(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches32):
> > -       bsf     %eax, %eax
> > -       lea     32(%rax, %rdi), %rax
> > -       ret
> > -
> > -END (__rawmemchr)
> > +#include "isa-default-impl.h"
> >
> >  weak_alias (__rawmemchr, rawmemchr)
> > -libc_hidden_builtin_def (__rawmemchr)
> > +libc_hidden_def (__rawmemchr)
> > diff --git a/sysdeps/x86_64/wmemchr.S b/sysdeps/x86_64/wmemchr.S
> > new file mode 100644
> > index 0000000000..eef91e556b
> > --- /dev/null
> > +++ b/sysdeps/x86_64/wmemchr.S
> > @@ -0,0 +1,28 @@
> > +/* Copyright (C) 2011-2022 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#define WMEMCHR        __wmemchr
> > +
> > +#define DEFAULT_IMPL_V1        "multiarch/wmemchr-sse2.S"
> > +#define DEFAULT_IMPL_V3        "multiarch/wmemchr-avx2.S"
> > +#define DEFAULT_IMPL_V4        "multiarch/wmemchr-evex.S"
> > +
> > +#include "isa-default-impl.h"
> > +
> > +libc_hidden_def (__wmemchr)
> > +weak_alias (__wmemchr, wmemchr)
> > +libc_hidden_weak (wmemchr)
> > --
> > 2.34.1
> >
>
>
> --
> H.J.

On Wed, Jun 22, 2022 at 3:04 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Wed, Jun 22, 2022 at 2:52 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Wed, Jun 22, 2022 at 1:58 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > >
> > > 1. Refactor files so that all implementations for in the multiarch
> > >    directory.
> > >     - Essentially moved sse2 {raw|w}memchr.S implementation to
> > >       multiarch/{raw|w}memchr-sse2.S
> > >
> > >     - The non-multiarch {raw|w}memchr.S file now only includes one of
> > >       the implementations in the multiarch directory based on the
> > >       compiled ISA level (only used for non-multiarch builds.
> > >       Otherwise we go through the ifunc selector).
> > >
> > > 2. Add ISA level build guards to different implementations.
> > >     - I.e memchr-avx2.S which is ISA level 3 will only build if
> > >       compiled ISA level <= 3. Otherwise there is no reason to include
> > >       it as we will always use one of the ISA level 4
> > >       implementations (memchr-evex{-rtm}.S).
> > >
> > > 3. Add new multiarch/rtld-{raw}memchr.S that just include the
> > >    non-multiarch {raw}memchr.S which will in turn select the best
> > >    implementation based on the compiled ISA level.
> > >
> > > 4. Refactor the ifunc selector and ifunc implementation list to use
> > >    the ISA level aware wrapper macros that allow functions below the
> > >    compiled ISA level (with a guranteed replacement) to be skipped.
> > >     - Guranteed replacement essentially means that for any ISA level
> > >       build there must be a function that the baseline of the ISA
> > >       supports. So for {raw|w}memchr.S since there is not ISA level 2
> > >       function, the ISA level 2 build still includes the ISA level
> > >       1 (sse2) function. Once we reach the ISA level 3 build, however,
> > >       {raw|w}memchr-avx2{-rtm}.S will always be sufficient so the ISA
> > >       level 1 implementation ({raw|w}memchr-sse2.S) will not be built.
> > >
> > > Tested with and without multiarch on x86_64 for ISA levels:
> > > {generic, x86-64-v2, x86-64-v3, x86-64-v4}
> > >
> > > And m32 with and without multiarch.
> > > ---
> > >  sysdeps/x86_64/isa-default-impl.h             |   8 +
> > >  sysdeps/x86_64/memchr.S                       | 357 +----------------
> > >  sysdeps/x86_64/multiarch/ifunc-evex.h         |  29 +-
> > >  sysdeps/x86_64/multiarch/ifunc-impl-list.c    |  72 ++--
> > >  sysdeps/x86_64/multiarch/memchr-avx2.S        |   5 +-
> > >  sysdeps/x86_64/multiarch/memchr-evex.S        |   5 +-
> > >  sysdeps/x86_64/multiarch/memchr-sse2.S        | 363 +++++++++++++++++-
> > >  sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S |   7 +-
> > >  sysdeps/x86_64/multiarch/rawmemchr-avx2.S     |   7 +-
> > >  sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S |   8 +-
> > >  sysdeps/x86_64/multiarch/rawmemchr-evex.S     |   7 +-
> > >  sysdeps/x86_64/multiarch/rawmemchr-sse2.S     | 198 +++++++++-
> > >  sysdeps/x86_64/multiarch/rtld-memchr.S        |  18 +
> > >  sysdeps/x86_64/multiarch/rtld-rawmemchr.S     |  18 +
> > >  sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S   |   7 +-
> > >  sysdeps/x86_64/multiarch/wmemchr-avx2.S       |   7 +-
> > >  sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S   |   8 +-
> > >  sysdeps/x86_64/multiarch/wmemchr-evex.S       |   7 +-
> > >  sysdeps/x86_64/multiarch/wmemchr-sse2.S       |   9 +-
> > >  sysdeps/x86_64/rawmemchr.S                    | 184 +--------
> > >  sysdeps/x86_64/wmemchr.S                      |  28 ++
> > >  21 files changed, 740 insertions(+), 612 deletions(-)
> > >  create mode 100644 sysdeps/x86_64/multiarch/rtld-memchr.S
> > >  create mode 100644 sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> > >  create mode 100644 sysdeps/x86_64/wmemchr.S
> > >
> > > diff --git a/sysdeps/x86_64/isa-default-impl.h b/sysdeps/x86_64/isa-default-impl.h
> > > index 34634668e5..b374a38b8b 100644
> > > --- a/sysdeps/x86_64/isa-default-impl.h
> > > +++ b/sysdeps/x86_64/isa-default-impl.h
> > > @@ -46,4 +46,12 @@
> > >  # error "Unsupported ISA Level!"
> > >  #endif
> > >
> > > +#if IS_IN(rtld) && !defined USE_MULTIARCH
> > > +#  error "RTLD version should only exist in multiarch build"
> > > +#endif
> > > +
> > > +#if defined USE_MULTIARCH && !IS_IN(rtld)
> > > +#  error "Multiarch build should not use ISA_DEFAULT_IMPL without RTLD"
> > > +#endif
> >
> > Please do
> >
> > #if IS_IN (rtld)
> > #else
> > #endif
> >
> > >  #include ISA_DEFAULT_IMPL
> > > diff --git a/sysdeps/x86_64/memchr.S b/sysdeps/x86_64/memchr.S
> > > index a160fd9b00..20b43508c4 100644
> > > --- a/sysdeps/x86_64/memchr.S
> > > +++ b/sysdeps/x86_64/memchr.S
> > > @@ -15,358 +15,13 @@
> > >     License along with the GNU C Library; if not, see
> > >     <https://www.gnu.org/licenses/>.  */
> > >
> > > -#include <sysdep.h>
> > > +#define MEMCHR __memchr
> > >
> > > -#ifdef USE_AS_WMEMCHR
> > > -# define MEMCHR                wmemchr
> > > -# define PCMPEQ                pcmpeqd
> > > -# define CHAR_PER_VEC  4
> > > -#else
> > > -# define MEMCHR                memchr
> > > -# define PCMPEQ                pcmpeqb
> > > -# define CHAR_PER_VEC  16
> > > -#endif
> > > +#define DEFAULT_IMPL_V1        "multiarch/memchr-sse2.S"
> > > +#define DEFAULT_IMPL_V3        "multiarch/memchr-avx2.S"
> > > +#define DEFAULT_IMPL_V4        "multiarch/memchr-evex.S"
> > >
> > > -/* fast SSE2 version with using pmaxub and 64 byte loop */
> > > +#include "isa-default-impl.h"
> > >
> > > -       .text
> > > -ENTRY(MEMCHR)
> > > -       movd    %esi, %xmm1
> > > -       mov     %edi, %ecx
> > > -
> > > -#ifdef __ILP32__
> > > -       /* Clear the upper 32 bits.  */
> > > -       movl    %edx, %edx
> > > -#endif
> > > -#ifdef USE_AS_WMEMCHR
> > > -       test    %RDX_LP, %RDX_LP
> > > -       jz      L(return_null)
> > > -#else
> > > -       punpcklbw %xmm1, %xmm1
> > > -       test    %RDX_LP, %RDX_LP
> > > -       jz      L(return_null)
> > > -       punpcklbw %xmm1, %xmm1
> > > -#endif
> > > -
> > > -       and     $63, %ecx
> > > -       pshufd  $0, %xmm1, %xmm1
> > > -
> > > -       cmp     $48, %ecx
> > > -       ja      L(crosscache)
> > > -
> > > -       movdqu  (%rdi), %xmm0
> > > -       PCMPEQ  %xmm1, %xmm0
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -
> > > -       jnz     L(matches_1)
> > > -       sub     $CHAR_PER_VEC, %rdx
> > > -       jbe     L(return_null)
> > > -       add     $16, %rdi
> > > -       and     $15, %ecx
> > > -       and     $-16, %rdi
> > > -#ifdef USE_AS_WMEMCHR
> > > -       shr     $2, %ecx
> > > -#endif
> > > -       add     %rcx, %rdx
> > > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > > -       jbe     L(exit_loop)
> > > -       jmp     L(loop_prolog)
> > > -
> > > -       .p2align 4
> > > -L(crosscache):
> > > -       and     $15, %ecx
> > > -       and     $-16, %rdi
> > > -       movdqa  (%rdi), %xmm0
> > > -
> > > -       PCMPEQ  %xmm1, %xmm0
> > > -       /* Check if there is a match.  */
> > > -       pmovmskb %xmm0, %eax
> > > -       /* Remove the leading bytes.  */
> > > -       sar     %cl, %eax
> > > -       test    %eax, %eax
> > > -       je      L(unaligned_no_match)
> > > -       /* Check which byte is a match.  */
> > > -       bsf     %eax, %eax
> > > -#ifdef USE_AS_WMEMCHR
> > > -       mov     %eax, %esi
> > > -       shr     $2, %esi
> > > -       sub     %rsi, %rdx
> > > -#else
> > > -       sub     %rax, %rdx
> > > -#endif
> > > -       jbe     L(return_null)
> > > -       add     %rdi, %rax
> > > -       add     %rcx, %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(unaligned_no_match):
> > > -       /* "rcx" is less than 16.  Calculate "rdx + rcx - 16" by using
> > > -          "rdx - (16 - rcx)" instead of "(rdx + rcx) - 16" to void
> > > -          possible addition overflow.  */
> > > -       neg     %rcx
> > > -       add     $16, %rcx
> > > -#ifdef USE_AS_WMEMCHR
> > > -       shr     $2, %ecx
> > > -#endif
> > > -       sub     %rcx, %rdx
> > > -       jbe     L(return_null)
> > > -       add     $16, %rdi
> > > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > > -       jbe     L(exit_loop)
> > > -
> > > -       .p2align 4
> > > -L(loop_prolog):
> > > -       movdqa  (%rdi), %xmm0
> > > -       PCMPEQ  %xmm1, %xmm0
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches)
> > > -
> > > -       movdqa  16(%rdi), %xmm2
> > > -       PCMPEQ  %xmm1, %xmm2
> > > -       pmovmskb %xmm2, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches16)
> > > -
> > > -       movdqa  32(%rdi), %xmm3
> > > -       PCMPEQ  %xmm1, %xmm3
> > > -       pmovmskb %xmm3, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches32)
> > > -
> > > -       movdqa  48(%rdi), %xmm4
> > > -       PCMPEQ  %xmm1, %xmm4
> > > -       add     $64, %rdi
> > > -       pmovmskb %xmm4, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches0)
> > > -
> > > -       test    $0x3f, %rdi
> > > -       jz      L(align64_loop)
> > > -
> > > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > > -       jbe     L(exit_loop)
> > > -
> > > -       movdqa  (%rdi), %xmm0
> > > -       PCMPEQ  %xmm1, %xmm0
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches)
> > > -
> > > -       movdqa  16(%rdi), %xmm2
> > > -       PCMPEQ  %xmm1, %xmm2
> > > -       pmovmskb %xmm2, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches16)
> > > -
> > > -       movdqa  32(%rdi), %xmm3
> > > -       PCMPEQ  %xmm1, %xmm3
> > > -       pmovmskb %xmm3, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches32)
> > > -
> > > -       movdqa  48(%rdi), %xmm3
> > > -       PCMPEQ  %xmm1, %xmm3
> > > -       pmovmskb %xmm3, %eax
> > > -
> > > -       add     $64, %rdi
> > > -       test    %eax, %eax
> > > -       jnz     L(matches0)
> > > -
> > > -       mov     %rdi, %rcx
> > > -       and     $-64, %rdi
> > > -       and     $63, %ecx
> > > -#ifdef USE_AS_WMEMCHR
> > > -       shr     $2, %ecx
> > > -#endif
> > > -       add     %rcx, %rdx
> > > -
> > > -       .p2align 4
> > > -L(align64_loop):
> > > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > > -       jbe     L(exit_loop)
> > > -       movdqa  (%rdi), %xmm0
> > > -       movdqa  16(%rdi), %xmm2
> > > -       movdqa  32(%rdi), %xmm3
> > > -       movdqa  48(%rdi), %xmm4
> > > -
> > > -       PCMPEQ  %xmm1, %xmm0
> > > -       PCMPEQ  %xmm1, %xmm2
> > > -       PCMPEQ  %xmm1, %xmm3
> > > -       PCMPEQ  %xmm1, %xmm4
> > > -
> > > -       pmaxub  %xmm0, %xmm3
> > > -       pmaxub  %xmm2, %xmm4
> > > -       pmaxub  %xmm3, %xmm4
> > > -       pmovmskb %xmm4, %eax
> > > -
> > > -       add     $64, %rdi
> > > -
> > > -       test    %eax, %eax
> > > -       jz      L(align64_loop)
> > > -
> > > -       sub     $64, %rdi
> > > -
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches)
> > > -
> > > -       pmovmskb %xmm2, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches16)
> > > -
> > > -       movdqa  32(%rdi), %xmm3
> > > -       PCMPEQ  %xmm1, %xmm3
> > > -
> > > -       PCMPEQ  48(%rdi), %xmm1
> > > -       pmovmskb %xmm3, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches32)
> > > -
> > > -       pmovmskb %xmm1, %eax
> > > -       bsf     %eax, %eax
> > > -       lea     48(%rdi, %rax), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(exit_loop):
> > > -       add     $(CHAR_PER_VEC * 2), %edx
> > > -       jle     L(exit_loop_32)
> > > -
> > > -       movdqa  (%rdi), %xmm0
> > > -       PCMPEQ  %xmm1, %xmm0
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches)
> > > -
> > > -       movdqa  16(%rdi), %xmm2
> > > -       PCMPEQ  %xmm1, %xmm2
> > > -       pmovmskb %xmm2, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches16)
> > > -
> > > -       movdqa  32(%rdi), %xmm3
> > > -       PCMPEQ  %xmm1, %xmm3
> > > -       pmovmskb %xmm3, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches32_1)
> > > -       sub     $CHAR_PER_VEC, %edx
> > > -       jle     L(return_null)
> > > -
> > > -       PCMPEQ  48(%rdi), %xmm1
> > > -       pmovmskb %xmm1, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches48_1)
> > > -       xor     %eax, %eax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(exit_loop_32):
> > > -       add     $(CHAR_PER_VEC * 2), %edx
> > > -       movdqa  (%rdi), %xmm0
> > > -       PCMPEQ  %xmm1, %xmm0
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches_1)
> > > -       sub     $CHAR_PER_VEC, %edx
> > > -       jbe     L(return_null)
> > > -
> > > -       PCMPEQ  16(%rdi), %xmm1
> > > -       pmovmskb %xmm1, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches16_1)
> > > -       xor     %eax, %eax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches0):
> > > -       bsf     %eax, %eax
> > > -       lea     -16(%rax, %rdi), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches):
> > > -       bsf     %eax, %eax
> > > -       add     %rdi, %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches16):
> > > -       bsf     %eax, %eax
> > > -       lea     16(%rax, %rdi), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches32):
> > > -       bsf     %eax, %eax
> > > -       lea     32(%rax, %rdi), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches_1):
> > > -       bsf     %eax, %eax
> > > -#ifdef USE_AS_WMEMCHR
> > > -       mov     %eax, %esi
> > > -       shr     $2, %esi
> > > -       sub     %rsi, %rdx
> > > -#else
> > > -       sub     %rax, %rdx
> > > -#endif
> > > -       jbe     L(return_null)
> > > -       add     %rdi, %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches16_1):
> > > -       bsf     %eax, %eax
> > > -#ifdef USE_AS_WMEMCHR
> > > -       mov     %eax, %esi
> > > -       shr     $2, %esi
> > > -       sub     %rsi, %rdx
> > > -#else
> > > -       sub     %rax, %rdx
> > > -#endif
> > > -       jbe     L(return_null)
> > > -       lea     16(%rdi, %rax), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches32_1):
> > > -       bsf     %eax, %eax
> > > -#ifdef USE_AS_WMEMCHR
> > > -       mov     %eax, %esi
> > > -       shr     $2, %esi
> > > -       sub     %rsi, %rdx
> > > -#else
> > > -       sub     %rax, %rdx
> > > -#endif
> > > -       jbe     L(return_null)
> > > -       lea     32(%rdi, %rax), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches48_1):
> > > -       bsf     %eax, %eax
> > > -#ifdef USE_AS_WMEMCHR
> > > -       mov     %eax, %esi
> > > -       shr     $2, %esi
> > > -       sub     %rsi, %rdx
> > > -#else
> > > -       sub     %rax, %rdx
> > > -#endif
> > > -       jbe     L(return_null)
> > > -       lea     48(%rdi, %rax), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(return_null):
> > > -       xor     %eax, %eax
> > > -       ret
> > > -END(MEMCHR)
> > > -
> > > -#ifndef USE_AS_WMEMCHR
> > > -strong_alias (memchr, __memchr)
> > > +weak_alias (__memchr, memchr)
> > >  libc_hidden_builtin_def(memchr)
> > > -#endif
> > > diff --git a/sysdeps/x86_64/multiarch/ifunc-evex.h b/sysdeps/x86_64/multiarch/ifunc-evex.h
> > > index b8f7a12ea2..856c6261f8 100644
> > > --- a/sysdeps/x86_64/multiarch/ifunc-evex.h
> > > +++ b/sysdeps/x86_64/multiarch/ifunc-evex.h
> > > @@ -19,24 +19,28 @@
> > >
> > >  #include <init-arch.h>
> > >
> > > -extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
> > > -extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> > > -extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
> > >  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;
> > >  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex_rtm) attribute_hidden;
> > >
> > > +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> > > +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
> > > +
> > > +extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
> > >
> > >  static inline void *
> > >  IFUNC_SELECTOR (void)
> > >  {
> > > -  const struct cpu_features* cpu_features = __get_cpu_features ();
> > > -
> > > -  if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> > > -      && CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> > > -      && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
> > > +  const struct cpu_features *cpu_features = __get_cpu_features ();
> > > +
> > > +  /* NB: The X86_ISA_* feature check macros are evaluated at
> > > +     compile time.  */
> > > +  if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> > > +      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> > > +      && X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> > > +                                     AVX_Fast_Unaligned_Load))
> > >      {
> > > -      if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
> > > -         && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
> > > +      if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
> > > +         && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
> > >         {
> > >           if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
> > >             return OPTIMIZE (evex_rtm);
> > > @@ -47,9 +51,12 @@ IFUNC_SELECTOR (void)
> > >        if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
> > >         return OPTIMIZE (avx2_rtm);
> > >
> > > -      if (!CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_VZEROUPPER))
> > > +      if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> > > +                                      Prefer_No_VZEROUPPER))
> > >         return OPTIMIZE (avx2);
> > >      }
> > >
> > > +  /* This is unreachable (compile time checked) if ISA level >= 3
> > > +     so no need for a robust fallback here.  */
> > >    return OPTIMIZE (sse2);
> > >  }
> > > diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > > index 883362f63d..bf52cf96d0 100644
> > > --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > > +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > > @@ -25,7 +25,8 @@
> > >
> > >  /* Fill ARRAY of MAX elements with IFUNC implementations for function
> > >     NAME supported on target machine and return the number of valid
> > > -   entries.  */
> > > +   entries.  Each set of implementations for a given function is sorted in
> > > +   descending order by ISA level.  */
> > >
> > >  size_t
> > >  __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > > @@ -53,24 +54,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > >
> > >    /* Support sysdeps/x86_64/multiarch/memchr.c.  */
> > >    IFUNC_IMPL (i, name, memchr,
> > > -             IFUNC_IMPL_ADD (array, i, memchr,
> > > -                             CPU_FEATURE_USABLE (AVX2),
> > > -                             __memchr_avx2)
> > > -             IFUNC_IMPL_ADD (array, i, memchr,
> > > -                             (CPU_FEATURE_USABLE (AVX2)
> > > -                              && CPU_FEATURE_USABLE (RTM)),
> > > -                             __memchr_avx2_rtm)
> > > -             IFUNC_IMPL_ADD (array, i, memchr,
> > > +             X86_IFUNC_IMPL_ADD_V4 (array, i, memchr,
> > >                               (CPU_FEATURE_USABLE (AVX512VL)
> > >                                && CPU_FEATURE_USABLE (AVX512BW)
> > >                                && CPU_FEATURE_USABLE (BMI2)),
> > >                               __memchr_evex)
> > > -             IFUNC_IMPL_ADD (array, i, memchr,
> > > +             X86_IFUNC_IMPL_ADD_V4 (array, i, memchr,
> > >                               (CPU_FEATURE_USABLE (AVX512VL)
> > >                                && CPU_FEATURE_USABLE (AVX512BW)
> > >                                && CPU_FEATURE_USABLE (BMI2)),
> > >                               __memchr_evex_rtm)
> > > -             IFUNC_IMPL_ADD (array, i, memchr, 1, __memchr_sse2))
> > > +             X86_IFUNC_IMPL_ADD_V3 (array, i, memchr,
> > > +                             CPU_FEATURE_USABLE (AVX2),
> > > +                             __memchr_avx2)
> > > +             X86_IFUNC_IMPL_ADD_V3 (array, i, memchr,
> > > +                             (CPU_FEATURE_USABLE (AVX2)
> > > +                              && CPU_FEATURE_USABLE (RTM)),
> > > +                             __memchr_avx2_rtm)
> > > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > > +             X86_IFUNC_IMPL_ADD_V2 (array, i, memchr,
> > > +                             1,
> > > +                             __memchr_sse2))
> > >
> > >    /* Support sysdeps/x86_64/multiarch/memcmp.c.  */
> > >    IFUNC_IMPL (i, name, memcmp,
> > > @@ -288,24 +292,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > >
> > >    /* Support sysdeps/x86_64/multiarch/rawmemchr.c.  */
> > >    IFUNC_IMPL (i, name, rawmemchr,
> > > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > > -                             CPU_FEATURE_USABLE (AVX2),
> > > -                             __rawmemchr_avx2)
> > > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > > -                             (CPU_FEATURE_USABLE (AVX2)
> > > -                              && CPU_FEATURE_USABLE (RTM)),
> > > -                             __rawmemchr_avx2_rtm)
> > > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > > +             X86_IFUNC_IMPL_ADD_V4 (array, i, rawmemchr,
> > >                               (CPU_FEATURE_USABLE (AVX512VL)
> > >                                && CPU_FEATURE_USABLE (AVX512BW)
> > >                                && CPU_FEATURE_USABLE (BMI2)),
> > >                               __rawmemchr_evex)
> > > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > > +             X86_IFUNC_IMPL_ADD_V4 (array, i, rawmemchr,
> > >                               (CPU_FEATURE_USABLE (AVX512VL)
> > >                                && CPU_FEATURE_USABLE (AVX512BW)
> > >                                && CPU_FEATURE_USABLE (BMI2)),
> > >                               __rawmemchr_evex_rtm)
> > > -             IFUNC_IMPL_ADD (array, i, rawmemchr, 1, __rawmemchr_sse2))
> > > +             X86_IFUNC_IMPL_ADD_V3 (array, i, rawmemchr,
> > > +                             CPU_FEATURE_USABLE (AVX2),
> > > +                             __rawmemchr_avx2)
> > > +             X86_IFUNC_IMPL_ADD_V3 (array, i, rawmemchr,
> > > +                             (CPU_FEATURE_USABLE (AVX2)
> > > +                              && CPU_FEATURE_USABLE (RTM)),
> > > +                             __rawmemchr_avx2_rtm)
> > > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > > +             X86_IFUNC_IMPL_ADD_V2 (array, i, rawmemchr,
> > > +                             1,
> > > +                             __rawmemchr_sse2))
> > >
> > >    /* Support sysdeps/x86_64/multiarch/strlen.c.  */
> > >    IFUNC_IMPL (i, name, strlen,
> > > @@ -748,24 +755,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > >
> > >    /* Support sysdeps/x86_64/multiarch/wmemchr.c.  */
> > >    IFUNC_IMPL (i, name, wmemchr,
> > > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > > -                             CPU_FEATURE_USABLE (AVX2),
> > > -                             __wmemchr_avx2)
> > > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > > -                             (CPU_FEATURE_USABLE (AVX2)
> > > -                              && CPU_FEATURE_USABLE (RTM)),
> > > -                             __wmemchr_avx2_rtm)
> > > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > > +             X86_IFUNC_IMPL_ADD_V4 (array, i, wmemchr,
> > >                               (CPU_FEATURE_USABLE (AVX512VL)
> > >                                && CPU_FEATURE_USABLE (AVX512BW)
> > >                                && CPU_FEATURE_USABLE (BMI2)),
> > >                               __wmemchr_evex)
> > > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > > +             X86_IFUNC_IMPL_ADD_V4 (array, i, wmemchr,
> > >                               (CPU_FEATURE_USABLE (AVX512VL)
> > >                                && CPU_FEATURE_USABLE (AVX512BW)
> > >                                && CPU_FEATURE_USABLE (BMI2)),
> > >                               __wmemchr_evex_rtm)
> > > -             IFUNC_IMPL_ADD (array, i, wmemchr, 1, __wmemchr_sse2))
> > > +             X86_IFUNC_IMPL_ADD_V3 (array, i, wmemchr,
> > > +                             CPU_FEATURE_USABLE (AVX2),
> > > +                             __wmemchr_avx2)
> > > +             X86_IFUNC_IMPL_ADD_V3 (array, i, wmemchr,
> > > +                             (CPU_FEATURE_USABLE (AVX2)
> > > +                              && CPU_FEATURE_USABLE (RTM)),
> > > +                             __wmemchr_avx2_rtm)
> > > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > > +             X86_IFUNC_IMPL_ADD_V2 (array, i, wmemchr,
> > > +                             1,
> > > +                             __wmemchr_sse2))
> > >
> > >    /* Support sysdeps/x86_64/multiarch/wmemcmp.c.  */
> > >    IFUNC_IMPL (i, name, wmemcmp,
> > > diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S
> > > index c5a256eb37..39be5f7083 100644
> > > --- a/sysdeps/x86_64/multiarch/memchr-avx2.S
> > > +++ b/sysdeps/x86_64/multiarch/memchr-avx2.S
> > > @@ -16,9 +16,10 @@
> > >     License along with the GNU C Library; if not, see
> > >     <https://www.gnu.org/licenses/>.  */
> > >
> > > -#if IS_IN (libc)
> > > +#include <isa-level.h>
> > > +#include <sysdep.h>
> > >
> > > -# include <sysdep.h>
> > > +#if ISA_SHOULD_BUILD (3)
> > >
> > >  # ifndef MEMCHR
> > >  #  define MEMCHR       __memchr_avx2
> > > diff --git a/sysdeps/x86_64/multiarch/memchr-evex.S b/sysdeps/x86_64/multiarch/memchr-evex.S
> > > index 0fd11b7632..0dd4f1dcce 100644
> > > --- a/sysdeps/x86_64/multiarch/memchr-evex.S
> > > +++ b/sysdeps/x86_64/multiarch/memchr-evex.S
> > > @@ -16,9 +16,10 @@
> > >     License along with the GNU C Library; if not, see
> > >     <https://www.gnu.org/licenses/>.  */
> > >
> > > -#if IS_IN (libc)
> > > +#include <isa-level.h>
> > > +#include <sysdep.h>
> > >
> > > -# include <sysdep.h>
> > > +#if ISA_SHOULD_BUILD (4)
> > >
> > >  # ifndef MEMCHR
> > >  #  define MEMCHR       __memchr_evex
> > > diff --git a/sysdeps/x86_64/multiarch/memchr-sse2.S b/sysdeps/x86_64/multiarch/memchr-sse2.S
> > > index 2c6fdd41d6..8c561cd687 100644
> > > --- a/sysdeps/x86_64/multiarch/memchr-sse2.S
> > > +++ b/sysdeps/x86_64/multiarch/memchr-sse2.S
> > > @@ -16,13 +16,360 @@
> > >     License along with the GNU C Library; if not, see
> > >     <https://www.gnu.org/licenses/>.  */
> > >
> > > -#if IS_IN (libc)
> > > -# define memchr __memchr_sse2
> > > +#include <isa-level.h>
> > > +#include <sysdep.h>
> > >
> > > -# undef strong_alias
> > > -# define strong_alias(memchr, __memchr)
> > > -# undef libc_hidden_builtin_def
> > > -# define libc_hidden_builtin_def(memchr)
> > > -#endif
> > > +/* MINIMUM_X86_ISA_LEVEL <= 2 because there is no V2 implementation
> > > +   so we need this to build for ISA V2 builds. */
> > > +#if ISA_SHOULD_BUILD (2)
> > > +
> > > +# ifndef MEMCHR
> > > +#  define MEMCHR       __memchr_sse2
> > > +# endif
> > > +# ifdef USE_AS_WMEMCHR
> > > +#  define PCMPEQ               pcmpeqd
> > > +#  define CHAR_PER_VEC 4
> > > +# else
> > > +#  define PCMPEQ               pcmpeqb
> > > +#  define CHAR_PER_VEC 16
> > > +# endif
> > > +
> > > +/* fast SSE2 version with using pmaxub and 64 byte loop */
> > > +
> > > +       .text
> > > +ENTRY(MEMCHR)
> > > +       movd    %esi, %xmm1
> > > +       mov     %edi, %ecx
> > > +
> > > +# ifdef __ILP32__
> > > +       /* Clear the upper 32 bits.  */
> > > +       movl    %edx, %edx
> > > +# endif
> > > +# ifdef USE_AS_WMEMCHR
> > > +       test    %RDX_LP, %RDX_LP
> > > +       jz      L(return_null)
> > > +# else
> > > +       punpcklbw %xmm1, %xmm1
> > > +       test    %RDX_LP, %RDX_LP
> > > +       jz      L(return_null)
> > > +       punpcklbw %xmm1, %xmm1
> > > +# endif
> > > +
> > > +       and     $63, %ecx
> > > +       pshufd  $0, %xmm1, %xmm1
> > > +
> > > +       cmp     $48, %ecx
> > > +       ja      L(crosscache)
> > > +
> > > +       movdqu  (%rdi), %xmm0
> > > +       PCMPEQ  %xmm1, %xmm0
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +
> > > +       jnz     L(matches_1)
> > > +       sub     $CHAR_PER_VEC, %rdx
> > > +       jbe     L(return_null)
> > > +       add     $16, %rdi
> > > +       and     $15, %ecx
> > > +       and     $-16, %rdi
> > > +# ifdef USE_AS_WMEMCHR
> > > +       shr     $2, %ecx
> > > +# endif
> > > +       add     %rcx, %rdx
> > > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > > +       jbe     L(exit_loop)
> > > +       jmp     L(loop_prolog)
> > > +
> > > +       .p2align 4
> > > +L(crosscache):
> > > +       and     $15, %ecx
> > > +       and     $-16, %rdi
> > > +       movdqa  (%rdi), %xmm0
> > > +
> > > +       PCMPEQ  %xmm1, %xmm0
> > > +       /* Check if there is a match.  */
> > > +       pmovmskb %xmm0, %eax
> > > +       /* Remove the leading bytes.  */
> > > +       sar     %cl, %eax
> > > +       test    %eax, %eax
> > > +       je      L(unaligned_no_match)
> > > +       /* Check which byte is a match.  */
> > > +       bsf     %eax, %eax
> > > +# ifdef USE_AS_WMEMCHR
> > > +       mov     %eax, %esi
> > > +       shr     $2, %esi
> > > +       sub     %rsi, %rdx
> > > +# else
> > > +       sub     %rax, %rdx
> > > +# endif
> > > +       jbe     L(return_null)
> > > +       add     %rdi, %rax
> > > +       add     %rcx, %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(unaligned_no_match):
> > > +       /* "rcx" is less than 16.  Calculate "rdx + rcx - 16" by using
> > > +          "rdx - (16 - rcx)" instead of "(rdx + rcx) - 16" to void
> > > +          possible addition overflow.  */
> > > +       neg     %rcx
> > > +       add     $16, %rcx
> > > +# ifdef USE_AS_WMEMCHR
> > > +       shr     $2, %ecx
> > > +# endif
> > > +       sub     %rcx, %rdx
> > > +       jbe     L(return_null)
> > > +       add     $16, %rdi
> > > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > > +       jbe     L(exit_loop)
> > > +
> > > +       .p2align 4
> > > +L(loop_prolog):
> > > +       movdqa  (%rdi), %xmm0
> > > +       PCMPEQ  %xmm1, %xmm0
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches)
> > > +
> > > +       movdqa  16(%rdi), %xmm2
> > > +       PCMPEQ  %xmm1, %xmm2
> > > +       pmovmskb %xmm2, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches16)
> > > +
> > > +       movdqa  32(%rdi), %xmm3
> > > +       PCMPEQ  %xmm1, %xmm3
> > > +       pmovmskb %xmm3, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches32)
> > > +
> > > +       movdqa  48(%rdi), %xmm4
> > > +       PCMPEQ  %xmm1, %xmm4
> > > +       add     $64, %rdi
> > > +       pmovmskb %xmm4, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches0)
> > > +
> > > +       test    $0x3f, %rdi
> > > +       jz      L(align64_loop)
> > > +
> > > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > > +       jbe     L(exit_loop)
> > > +
> > > +       movdqa  (%rdi), %xmm0
> > > +       PCMPEQ  %xmm1, %xmm0
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches)
> > > +
> > > +       movdqa  16(%rdi), %xmm2
> > > +       PCMPEQ  %xmm1, %xmm2
> > > +       pmovmskb %xmm2, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches16)
> > > +
> > > +       movdqa  32(%rdi), %xmm3
> > > +       PCMPEQ  %xmm1, %xmm3
> > > +       pmovmskb %xmm3, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches32)
> > > +
> > > +       movdqa  48(%rdi), %xmm3
> > > +       PCMPEQ  %xmm1, %xmm3
> > > +       pmovmskb %xmm3, %eax
> > > +
> > > +       add     $64, %rdi
> > > +       test    %eax, %eax
> > > +       jnz     L(matches0)
> > > +
> > > +       mov     %rdi, %rcx
> > > +       and     $-64, %rdi
> > > +       and     $63, %ecx
> > > +# ifdef USE_AS_WMEMCHR
> > > +       shr     $2, %ecx
> > > +# endif
> > > +       add     %rcx, %rdx
> > > +
> > > +       .p2align 4
> > > +L(align64_loop):
> > > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > > +       jbe     L(exit_loop)
> > > +       movdqa  (%rdi), %xmm0
> > > +       movdqa  16(%rdi), %xmm2
> > > +       movdqa  32(%rdi), %xmm3
> > > +       movdqa  48(%rdi), %xmm4
> > > +
> > > +       PCMPEQ  %xmm1, %xmm0
> > > +       PCMPEQ  %xmm1, %xmm2
> > > +       PCMPEQ  %xmm1, %xmm3
> > > +       PCMPEQ  %xmm1, %xmm4
> > >
> > > -#include "../memchr.S"
> > > +       pmaxub  %xmm0, %xmm3
> > > +       pmaxub  %xmm2, %xmm4
> > > +       pmaxub  %xmm3, %xmm4
> > > +       pmovmskb %xmm4, %eax
> > > +
> > > +       add     $64, %rdi
> > > +
> > > +       test    %eax, %eax
> > > +       jz      L(align64_loop)
> > > +
> > > +       sub     $64, %rdi
> > > +
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches)
> > > +
> > > +       pmovmskb %xmm2, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches16)
> > > +
> > > +       movdqa  32(%rdi), %xmm3
> > > +       PCMPEQ  %xmm1, %xmm3
> > > +
> > > +       PCMPEQ  48(%rdi), %xmm1
> > > +       pmovmskb %xmm3, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches32)
> > > +
> > > +       pmovmskb %xmm1, %eax
> > > +       bsf     %eax, %eax
> > > +       lea     48(%rdi, %rax), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(exit_loop):
> > > +       add     $(CHAR_PER_VEC * 2), %edx
> > > +       jle     L(exit_loop_32)
> > > +
> > > +       movdqa  (%rdi), %xmm0
> > > +       PCMPEQ  %xmm1, %xmm0
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches)
> > > +
> > > +       movdqa  16(%rdi), %xmm2
> > > +       PCMPEQ  %xmm1, %xmm2
> > > +       pmovmskb %xmm2, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches16)
> > > +
> > > +       movdqa  32(%rdi), %xmm3
> > > +       PCMPEQ  %xmm1, %xmm3
> > > +       pmovmskb %xmm3, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches32_1)
> > > +       sub     $CHAR_PER_VEC, %edx
> > > +       jle     L(return_null)
> > > +
> > > +       PCMPEQ  48(%rdi), %xmm1
> > > +       pmovmskb %xmm1, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches48_1)
> > > +       xor     %eax, %eax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(exit_loop_32):
> > > +       add     $(CHAR_PER_VEC * 2), %edx
> > > +       movdqa  (%rdi), %xmm0
> > > +       PCMPEQ  %xmm1, %xmm0
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches_1)
> > > +       sub     $CHAR_PER_VEC, %edx
> > > +       jbe     L(return_null)
> > > +
> > > +       PCMPEQ  16(%rdi), %xmm1
> > > +       pmovmskb %xmm1, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches16_1)
> > > +       xor     %eax, %eax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches0):
> > > +       bsf     %eax, %eax
> > > +       lea     -16(%rax, %rdi), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches):
> > > +       bsf     %eax, %eax
> > > +       add     %rdi, %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches16):
> > > +       bsf     %eax, %eax
> > > +       lea     16(%rax, %rdi), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches32):
> > > +       bsf     %eax, %eax
> > > +       lea     32(%rax, %rdi), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches_1):
> > > +       bsf     %eax, %eax
> > > +# ifdef USE_AS_WMEMCHR
> > > +       mov     %eax, %esi
> > > +       shr     $2, %esi
> > > +       sub     %rsi, %rdx
> > > +# else
> > > +       sub     %rax, %rdx
> > > +# endif
> > > +       jbe     L(return_null)
> > > +       add     %rdi, %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches16_1):
> > > +       bsf     %eax, %eax
> > > +# ifdef USE_AS_WMEMCHR
> > > +       mov     %eax, %esi
> > > +       shr     $2, %esi
> > > +       sub     %rsi, %rdx
> > > +# else
> > > +       sub     %rax, %rdx
> > > +# endif
> > > +       jbe     L(return_null)
> > > +       lea     16(%rdi, %rax), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches32_1):
> > > +       bsf     %eax, %eax
> > > +# ifdef USE_AS_WMEMCHR
> > > +       mov     %eax, %esi
> > > +       shr     $2, %esi
> > > +       sub     %rsi, %rdx
> > > +# else
> > > +       sub     %rax, %rdx
> > > +# endif
> > > +       jbe     L(return_null)
> > > +       lea     32(%rdi, %rax), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches48_1):
> > > +       bsf     %eax, %eax
> > > +# ifdef USE_AS_WMEMCHR
> > > +       mov     %eax, %esi
> > > +       shr     $2, %esi
> > > +       sub     %rsi, %rdx
> > > +# else
> > > +       sub     %rax, %rdx
> > > +# endif
> > > +       jbe     L(return_null)
> > > +       lea     48(%rdi, %rax), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(return_null):
> > > +       xor     %eax, %eax
> > > +       ret
> > > +END(MEMCHR)
> > > +#endif
> > > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S b/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > > index acc5f6e2fb..5c1dcd3ca7 100644
> > > --- a/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > > +++ b/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > > @@ -1,4 +1,7 @@
> > > -#define MEMCHR __rawmemchr_avx2_rtm
> > > -#define USE_AS_RAWMEMCHR 1
> > > +#ifndef RAWMEMCHR
> > > +# define RAWMEMCHR     __rawmemchr_avx2_rtm
> > > +#endif
> > > +#define USE_AS_RAWMEMCHR       1
> > > +#define MEMCHR RAWMEMCHR
> > >
> > >  #include "memchr-avx2-rtm.S"
> >
> > Will we ever use the RTM version as the default?
>
> We had talked about it and agreed not to. I think we can
> safely say we don't need it for the RTLD default because
> we know no transactions.
>
> As for the non-multiarch build selection it's a bit more ambiguous.

Since the RTM version isn't used for default, we should
leave the RTM .S files alone.

> >
> > > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-avx2.S b/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > > index 128f9ea637..d6bff28757 100644
> > > --- a/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > > +++ b/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > > @@ -1,4 +1,7 @@
> > > -#define MEMCHR __rawmemchr_avx2
> > > -#define USE_AS_RAWMEMCHR 1
> > > +#ifndef RAWMEMCHR
> > > +# define RAWMEMCHR     __rawmemchr_avx2
> > > +#endif
> > > +#define USE_AS_RAWMEMCHR       1
> > > +#define MEMCHR RAWMEMCHR
> > >
> > >  #include "memchr-avx2.S"
> > > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S b/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > > index deda1ca395..8ff7f27c9c 100644
> > > --- a/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > > +++ b/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > > @@ -1,3 +1,7 @@
> > > -#define MEMCHR __rawmemchr_evex_rtm
> > > -#define USE_AS_RAWMEMCHR 1
> > > +#ifndef RAWMEMCHR
> > > +# define RAWMEMCHR     __rawmemchr_evex_rtm
> > > +#endif
> > > +#define USE_AS_RAWMEMCHR       1
> > > +#define MEMCHR RAWMEMCHR
> > > +
> >
> > Will we ever use the RTM version as the default?
> >
> > >  #include "memchr-evex-rtm.S"
> > > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-evex.S b/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > > index ec942b77ba..dc1c450699 100644
> > > --- a/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > > +++ b/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > > @@ -1,4 +1,7 @@
> > > -#define MEMCHR __rawmemchr_evex
> > > -#define USE_AS_RAWMEMCHR 1
> > > +#ifndef RAWMEMCHR
> > > +# define RAWMEMCHR     __rawmemchr_evex
> > > +#endif
> > > +#define USE_AS_RAWMEMCHR       1
> > > +#define MEMCHR RAWMEMCHR
> > >
> > >  #include "memchr-evex.S"
> > > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-sse2.S b/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > > index 3841c14c34..e2c2e20d85 100644
> > > --- a/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > > +++ b/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > > @@ -16,14 +16,192 @@
> > >     License along with the GNU C Library; if not, see
> > >     <https://www.gnu.org/licenses/>.  */
> > >
> > > -/* Define multiple versions only for the definition in libc. */
> > > -#if IS_IN (libc)
> > > -# define __rawmemchr __rawmemchr_sse2
> > > -
> > > -# undef weak_alias
> > > -# define weak_alias(__rawmemchr, rawmemchr)
> > > -# undef libc_hidden_def
> > > -# define libc_hidden_def(__rawmemchr)
> > > -#endif
> > > +#include <isa-level.h>
> > > +#include <sysdep.h>
> > > +
> > > +/* MINIMUM_X86_ISA_LEVEL <= 2 because there is no V2 implementation
> > > +   so we need this to build for ISA V2 builds. */
> > > +#if ISA_SHOULD_BUILD (2)
> > > +
> > > +# ifndef RAWMEMCHR
> > > +#  define RAWMEMCHR    __rawmemchr_sse2
> > > +# endif
> > > +
> > > +       .text
> > > +ENTRY (RAWMEMCHR)
> > > +       movd    %rsi, %xmm1
> > > +       mov     %rdi, %rcx
> > > +
> > > +       punpcklbw %xmm1, %xmm1
> > > +       punpcklbw %xmm1, %xmm1
> > > +
> > > +       and     $63, %rcx
> > > +       pshufd  $0, %xmm1, %xmm1
> > > +
> > > +       cmp     $48, %rcx
> > > +       ja      L(crosscache)
> > > +
> > > +       movdqu  (%rdi), %xmm0
> > > +       pcmpeqb %xmm1, %xmm0
> > > +/* Check if there is a match.  */
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +
> > > +       jnz     L(matches)
> > > +       add     $16, %rdi
> > > +       and     $-16, %rdi
> > > +       jmp     L(loop_prolog)
> > > +
> > > +       .p2align 4
> > > +L(crosscache):
> > > +       and     $15, %rcx
> > > +       and     $-16, %rdi
> > > +       movdqa  (%rdi), %xmm0
> > > +
> > > +       pcmpeqb %xmm1, %xmm0
> > > +/* Check if there is a match.  */
> > > +       pmovmskb %xmm0, %eax
> > > +/* Remove the leading bytes.  */
> > > +       sar     %cl, %eax
> > > +       test    %eax, %eax
> > > +       je      L(unaligned_no_match)
> > > +/* Check which byte is a match.  */
> > > +       bsf     %eax, %eax
> > > +
> > > +       add     %rdi, %rax
> > > +       add     %rcx, %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(unaligned_no_match):
> > > +       add     $16, %rdi
> > > +
> > > +       .p2align 4
> > > +L(loop_prolog):
> > > +       movdqa  (%rdi), %xmm0
> > > +       pcmpeqb %xmm1, %xmm0
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches)
> > > +
> > > +       movdqa  16(%rdi), %xmm2
> > > +       pcmpeqb %xmm1, %xmm2
> > > +       pmovmskb %xmm2, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches16)
> > > +
> > > +       movdqa  32(%rdi), %xmm3
> > > +       pcmpeqb %xmm1, %xmm3
> > > +       pmovmskb %xmm3, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches32)
> > > +
> > > +       movdqa  48(%rdi), %xmm4
> > > +       pcmpeqb %xmm1, %xmm4
> > > +       add     $64, %rdi
> > > +       pmovmskb %xmm4, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches0)
> > > +
> > > +       test    $0x3f, %rdi
> > > +       jz      L(align64_loop)
> > > +
> > > +       movdqa  (%rdi), %xmm0
> > > +       pcmpeqb %xmm1, %xmm0
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches)
> > > +
> > > +       movdqa  16(%rdi), %xmm2
> > > +       pcmpeqb %xmm1, %xmm2
> > > +       pmovmskb %xmm2, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches16)
> > >
> > > -#include "../rawmemchr.S"
> > > +       movdqa  32(%rdi), %xmm3
> > > +       pcmpeqb %xmm1, %xmm3
> > > +       pmovmskb %xmm3, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches32)
> > > +
> > > +       movdqa  48(%rdi), %xmm3
> > > +       pcmpeqb %xmm1, %xmm3
> > > +       pmovmskb %xmm3, %eax
> > > +
> > > +       add     $64, %rdi
> > > +       test    %eax, %eax
> > > +       jnz     L(matches0)
> > > +
> > > +       and     $-64, %rdi
> > > +
> > > +       .p2align 4
> > > +L(align64_loop):
> > > +       movdqa  (%rdi), %xmm0
> > > +       movdqa  16(%rdi), %xmm2
> > > +       movdqa  32(%rdi), %xmm3
> > > +       movdqa  48(%rdi), %xmm4
> > > +
> > > +       pcmpeqb %xmm1, %xmm0
> > > +       pcmpeqb %xmm1, %xmm2
> > > +       pcmpeqb %xmm1, %xmm3
> > > +       pcmpeqb %xmm1, %xmm4
> > > +
> > > +       pmaxub  %xmm0, %xmm3
> > > +       pmaxub  %xmm2, %xmm4
> > > +       pmaxub  %xmm3, %xmm4
> > > +       pmovmskb %xmm4, %eax
> > > +
> > > +       add     $64, %rdi
> > > +
> > > +       test    %eax, %eax
> > > +       jz      L(align64_loop)
> > > +
> > > +       sub     $64, %rdi
> > > +
> > > +       pmovmskb %xmm0, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches)
> > > +
> > > +       pmovmskb %xmm2, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches16)
> > > +
> > > +       movdqa  32(%rdi), %xmm3
> > > +       pcmpeqb %xmm1, %xmm3
> > > +
> > > +       pcmpeqb 48(%rdi), %xmm1
> > > +       pmovmskb %xmm3, %eax
> > > +       test    %eax, %eax
> > > +       jnz     L(matches32)
> > > +
> > > +       pmovmskb %xmm1, %eax
> > > +       bsf     %eax, %eax
> > > +       lea     48(%rdi, %rax), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches0):
> > > +       bsf     %eax, %eax
> > > +       lea     -16(%rax, %rdi), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches):
> > > +       bsf     %eax, %eax
> > > +       add     %rdi, %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches16):
> > > +       bsf     %eax, %eax
> > > +       lea     16(%rax, %rdi), %rax
> > > +       ret
> > > +
> > > +       .p2align 4
> > > +L(matches32):
> > > +       bsf     %eax, %eax
> > > +       lea     32(%rax, %rdi), %rax
> > > +       ret
> > > +
> > > +END (RAWMEMCHR)
> > > +#endif
> > > diff --git a/sysdeps/x86_64/multiarch/rtld-memchr.S b/sysdeps/x86_64/multiarch/rtld-memchr.S
> > > new file mode 100644
> > > index 0000000000..a14b192bed
> > > --- /dev/null
> > > +++ b/sysdeps/x86_64/multiarch/rtld-memchr.S
> > > @@ -0,0 +1,18 @@
> > > +/* Copyright (C) 2022 Free Software Foundation, Inc.
> > > +   This file is part of the GNU C Library.
> > > +
> > > +   The GNU C Library is free software; you can redistribute it and/or
> > > +   modify it under the terms of the GNU Lesser General Public
> > > +   License as published by the Free Software Foundation; either
> > > +   version 2.1 of the License, or (at your option) any later version.
> > > +
> > > +   The GNU C Library is distributed in the hope that it will be useful,
> > > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > > +   Lesser General Public License for more details.
> > > +
> > > +   You should have received a copy of the GNU Lesser General Public
> > > +   License along with the GNU C Library; if not, see
> > > +   <https://www.gnu.org/licenses/>.  */
> > > +
> > > +#include "../memchr.S"
> > > diff --git a/sysdeps/x86_64/multiarch/rtld-rawmemchr.S b/sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> > > new file mode 100644
> > > index 0000000000..5d4110a052
> > > --- /dev/null
> > > +++ b/sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> > > @@ -0,0 +1,18 @@
> > > +/* Copyright (C) 2022 Free Software Foundation, Inc.
> > > +   This file is part of the GNU C Library.
> > > +
> > > +   The GNU C Library is free software; you can redistribute it and/or
> > > +   modify it under the terms of the GNU Lesser General Public
> > > +   License as published by the Free Software Foundation; either
> > > +   version 2.1 of the License, or (at your option) any later version.
> > > +
> > > +   The GNU C Library is distributed in the hope that it will be useful,
> > > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > > +   Lesser General Public License for more details.
> > > +
> > > +   You should have received a copy of the GNU Lesser General Public
> > > +   License along with the GNU C Library; if not, see
> > > +   <https://www.gnu.org/licenses/>.  */
> > > +
> > > +#include "../rawmemchr.S"
> > > diff --git a/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S b/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > > index 58ed21db01..2a1cff5b05 100644
> > > --- a/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > > +++ b/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > > @@ -1,4 +1,7 @@
> > > -#define MEMCHR __wmemchr_avx2_rtm
> > > -#define USE_AS_WMEMCHR 1
> > > +#ifndef WMEMCHR
> > > +# define WMEMCHR       __wmemchr_avx2_rtm
> > > +#endif
> > > +#define USE_AS_WMEMCHR 1
> > > +#define MEMCHR WMEMCHR
> > >
> > >  #include "memchr-avx2-rtm.S"
> > > diff --git a/sysdeps/x86_64/multiarch/wmemchr-avx2.S b/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > > index 282854f1a1..2bf93fd84b 100644
> > > --- a/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > > +++ b/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > > @@ -1,4 +1,7 @@
> > > -#define MEMCHR __wmemchr_avx2
> > > -#define USE_AS_WMEMCHR 1
> > > +#ifndef WMEMCHR
> > > +# define WMEMCHR       __wmemchr_avx2
> > > +#endif
> > > +#define USE_AS_WMEMCHR 1
> > > +#define MEMCHR WMEMCHR
> > >
> > >  #include "memchr-avx2.S"
> > > diff --git a/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S b/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > > index a346cd35a1..c67309e8a1 100644
> > > --- a/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > > +++ b/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > > @@ -1,3 +1,7 @@
> > > -#define MEMCHR __wmemchr_evex_rtm
> > > -#define USE_AS_WMEMCHR 1
> > > +#ifndef WMEMCHR
> > > +# define WMEMCHR       __wmemchr_evex_rtm
> > > +#endif
> > > +#define USE_AS_WMEMCHR 1
> > > +#define MEMCHR WMEMCHR
> > > +
> > >  #include "memchr-evex-rtm.S"
> > > diff --git a/sysdeps/x86_64/multiarch/wmemchr-evex.S b/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > > index 06cd0f9f5a..5512d5cdc3 100644
> > > --- a/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > > +++ b/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > > @@ -1,4 +1,7 @@
> > > -#define MEMCHR __wmemchr_evex
> > > -#define USE_AS_WMEMCHR 1
> > > +#ifndef WMEMCHR
> > > +# define WMEMCHR       __wmemchr_evex
> > > +#endif
> > > +#define USE_AS_WMEMCHR 1
> > > +#define MEMCHR WMEMCHR
> > >
> > >  #include "memchr-evex.S"
> > > diff --git a/sysdeps/x86_64/multiarch/wmemchr-sse2.S b/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > > index 70a965d552..b675a070d4 100644
> > > --- a/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > > +++ b/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > > @@ -1,4 +1,7 @@
> > > -#define USE_AS_WMEMCHR 1
> > > -#define wmemchr __wmemchr_sse2
> > > +#ifndef WMEMCHR
> > > +# define WMEMCHR       __wmemchr_sse2
> > > +#endif
> > > +#define USE_AS_WMEMCHR 1
> > > +#define MEMCHR WMEMCHR
> > >
> > > -#include "../memchr.S"
> > > +#include "memchr-sse2.S"
> > > diff --git a/sysdeps/x86_64/rawmemchr.S b/sysdeps/x86_64/rawmemchr.S
> > > index 4c1a3383b9..ba7e5202e6 100644
> > > --- a/sysdeps/x86_64/rawmemchr.S
> > > +++ b/sysdeps/x86_64/rawmemchr.S
> > > @@ -17,185 +17,13 @@
> > >     License along with the GNU C Library; if not, see
> > >     <https://www.gnu.org/licenses/>.  */
> > >
> > > -#include <sysdep.h>
> > > +#define RAWMEMCHR      __rawmemchr
> > >
> > > -       .text
> > > -ENTRY (__rawmemchr)
> > > -       movd    %rsi, %xmm1
> > > -       mov     %rdi, %rcx
> > > +#define DEFAULT_IMPL_V1        "multiarch/rawmemchr-sse2.S"
> > > +#define DEFAULT_IMPL_V3        "multiarch/rawmemchr-avx2.S"
> > > +#define DEFAULT_IMPL_V4        "multiarch/rawmemchr-evex.S"
> > >
> > > -       punpcklbw %xmm1, %xmm1
> > > -       punpcklbw %xmm1, %xmm1
> > > -
> > > -       and     $63, %rcx
> > > -       pshufd  $0, %xmm1, %xmm1
> > > -
> > > -       cmp     $48, %rcx
> > > -       ja      L(crosscache)
> > > -
> > > -       movdqu  (%rdi), %xmm0
> > > -       pcmpeqb %xmm1, %xmm0
> > > -/* Check if there is a match.  */
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -
> > > -       jnz     L(matches)
> > > -       add     $16, %rdi
> > > -       and     $-16, %rdi
> > > -       jmp     L(loop_prolog)
> > > -
> > > -       .p2align 4
> > > -L(crosscache):
> > > -       and     $15, %rcx
> > > -       and     $-16, %rdi
> > > -       movdqa  (%rdi), %xmm0
> > > -
> > > -       pcmpeqb %xmm1, %xmm0
> > > -/* Check if there is a match.  */
> > > -       pmovmskb %xmm0, %eax
> > > -/* Remove the leading bytes.  */
> > > -       sar     %cl, %eax
> > > -       test    %eax, %eax
> > > -       je      L(unaligned_no_match)
> > > -/* Check which byte is a match.  */
> > > -       bsf     %eax, %eax
> > > -
> > > -       add     %rdi, %rax
> > > -       add     %rcx, %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(unaligned_no_match):
> > > -       add     $16, %rdi
> > > -
> > > -       .p2align 4
> > > -L(loop_prolog):
> > > -       movdqa  (%rdi), %xmm0
> > > -       pcmpeqb %xmm1, %xmm0
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches)
> > > -
> > > -       movdqa  16(%rdi), %xmm2
> > > -       pcmpeqb %xmm1, %xmm2
> > > -       pmovmskb %xmm2, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches16)
> > > -
> > > -       movdqa  32(%rdi), %xmm3
> > > -       pcmpeqb %xmm1, %xmm3
> > > -       pmovmskb %xmm3, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches32)
> > > -
> > > -       movdqa  48(%rdi), %xmm4
> > > -       pcmpeqb %xmm1, %xmm4
> > > -       add     $64, %rdi
> > > -       pmovmskb %xmm4, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches0)
> > > -
> > > -       test    $0x3f, %rdi
> > > -       jz      L(align64_loop)
> > > -
> > > -       movdqa  (%rdi), %xmm0
> > > -       pcmpeqb %xmm1, %xmm0
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches)
> > > -
> > > -       movdqa  16(%rdi), %xmm2
> > > -       pcmpeqb %xmm1, %xmm2
> > > -       pmovmskb %xmm2, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches16)
> > > -
> > > -       movdqa  32(%rdi), %xmm3
> > > -       pcmpeqb %xmm1, %xmm3
> > > -       pmovmskb %xmm3, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches32)
> > > -
> > > -       movdqa  48(%rdi), %xmm3
> > > -       pcmpeqb %xmm1, %xmm3
> > > -       pmovmskb %xmm3, %eax
> > > -
> > > -       add     $64, %rdi
> > > -       test    %eax, %eax
> > > -       jnz     L(matches0)
> > > -
> > > -       and     $-64, %rdi
> > > -
> > > -       .p2align 4
> > > -L(align64_loop):
> > > -       movdqa  (%rdi), %xmm0
> > > -       movdqa  16(%rdi), %xmm2
> > > -       movdqa  32(%rdi), %xmm3
> > > -       movdqa  48(%rdi), %xmm4
> > > -
> > > -       pcmpeqb %xmm1, %xmm0
> > > -       pcmpeqb %xmm1, %xmm2
> > > -       pcmpeqb %xmm1, %xmm3
> > > -       pcmpeqb %xmm1, %xmm4
> > > -
> > > -       pmaxub  %xmm0, %xmm3
> > > -       pmaxub  %xmm2, %xmm4
> > > -       pmaxub  %xmm3, %xmm4
> > > -       pmovmskb %xmm4, %eax
> > > -
> > > -       add     $64, %rdi
> > > -
> > > -       test    %eax, %eax
> > > -       jz      L(align64_loop)
> > > -
> > > -       sub     $64, %rdi
> > > -
> > > -       pmovmskb %xmm0, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches)
> > > -
> > > -       pmovmskb %xmm2, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches16)
> > > -
> > > -       movdqa  32(%rdi), %xmm3
> > > -       pcmpeqb %xmm1, %xmm3
> > > -
> > > -       pcmpeqb 48(%rdi), %xmm1
> > > -       pmovmskb %xmm3, %eax
> > > -       test    %eax, %eax
> > > -       jnz     L(matches32)
> > > -
> > > -       pmovmskb %xmm1, %eax
> > > -       bsf     %eax, %eax
> > > -       lea     48(%rdi, %rax), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches0):
> > > -       bsf     %eax, %eax
> > > -       lea     -16(%rax, %rdi), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches):
> > > -       bsf     %eax, %eax
> > > -       add     %rdi, %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches16):
> > > -       bsf     %eax, %eax
> > > -       lea     16(%rax, %rdi), %rax
> > > -       ret
> > > -
> > > -       .p2align 4
> > > -L(matches32):
> > > -       bsf     %eax, %eax
> > > -       lea     32(%rax, %rdi), %rax
> > > -       ret
> > > -
> > > -END (__rawmemchr)
> > > +#include "isa-default-impl.h"
> > >
> > >  weak_alias (__rawmemchr, rawmemchr)
> > > -libc_hidden_builtin_def (__rawmemchr)
> > > +libc_hidden_def (__rawmemchr)
> > > diff --git a/sysdeps/x86_64/wmemchr.S b/sysdeps/x86_64/wmemchr.S
> > > new file mode 100644
> > > index 0000000000..eef91e556b
> > > --- /dev/null
> > > +++ b/sysdeps/x86_64/wmemchr.S
> > > @@ -0,0 +1,28 @@
> > > +/* Copyright (C) 2011-2022 Free Software Foundation, Inc.
> > > +   This file is part of the GNU C Library.
> > > +
> > > +   The GNU C Library is free software; you can redistribute it and/or
> > > +   modify it under the terms of the GNU Lesser General Public
> > > +   License as published by the Free Software Foundation; either
> > > +   version 2.1 of the License, or (at your option) any later version.
> > > +
> > > +   The GNU C Library is distributed in the hope that it will be useful,
> > > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > > +   Lesser General Public License for more details.
> > > +
> > > +   You should have received a copy of the GNU Lesser General Public
> > > +   License along with the GNU C Library; if not, see
> > > +   <https://www.gnu.org/licenses/>.  */
> > > +
> > > +#define WMEMCHR        __wmemchr
> > > +
> > > +#define DEFAULT_IMPL_V1        "multiarch/wmemchr-sse2.S"
> > > +#define DEFAULT_IMPL_V3        "multiarch/wmemchr-avx2.S"
> > > +#define DEFAULT_IMPL_V4        "multiarch/wmemchr-evex.S"
> > > +
> > > +#include "isa-default-impl.h"
> > > +
> > > +libc_hidden_def (__wmemchr)
> > > +weak_alias (__wmemchr, wmemchr)
> > > +libc_hidden_weak (wmemchr)
> > > --
> > > 2.34.1
> > >
> >
> >
> > --
> > H.J.

On Wed, Jun 22, 2022 at 2:52 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Wed, Jun 22, 2022 at 1:58 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > 1. Refactor files so that all implementations for in the multiarch
> >    directory.
> >     - Essentially moved sse2 {raw|w}memchr.S implementation to
> >       multiarch/{raw|w}memchr-sse2.S
> >
> >     - The non-multiarch {raw|w}memchr.S file now only includes one of
> >       the implementations in the multiarch directory based on the
> >       compiled ISA level (only used for non-multiarch builds.
> >       Otherwise we go through the ifunc selector).
> >
> > 2. Add ISA level build guards to different implementations.
> >     - I.e memchr-avx2.S which is ISA level 3 will only build if
> >       compiled ISA level <= 3. Otherwise there is no reason to include
> >       it as we will always use one of the ISA level 4
> >       implementations (memchr-evex{-rtm}.S).
> >
> > 3. Add new multiarch/rtld-{raw}memchr.S that just include the
> >    non-multiarch {raw}memchr.S which will in turn select the best
> >    implementation based on the compiled ISA level.
> >
> > 4. Refactor the ifunc selector and ifunc implementation list to use
> >    the ISA level aware wrapper macros that allow functions below the
> >    compiled ISA level (with a guranteed replacement) to be skipped.
> >     - Guranteed replacement essentially means that for any ISA level
> >       build there must be a function that the baseline of the ISA
> >       supports. So for {raw|w}memchr.S since there is not ISA level 2
> >       function, the ISA level 2 build still includes the ISA level
> >       1 (sse2) function. Once we reach the ISA level 3 build, however,
> >       {raw|w}memchr-avx2{-rtm}.S will always be sufficient so the ISA
> >       level 1 implementation ({raw|w}memchr-sse2.S) will not be built.
> >
> > Tested with and without multiarch on x86_64 for ISA levels:
> > {generic, x86-64-v2, x86-64-v3, x86-64-v4}
> >
> > And m32 with and without multiarch.
> > ---
> >  sysdeps/x86_64/isa-default-impl.h             |   8 +
> >  sysdeps/x86_64/memchr.S                       | 357 +----------------
> >  sysdeps/x86_64/multiarch/ifunc-evex.h         |  29 +-
> >  sysdeps/x86_64/multiarch/ifunc-impl-list.c    |  72 ++--
> >  sysdeps/x86_64/multiarch/memchr-avx2.S        |   5 +-
> >  sysdeps/x86_64/multiarch/memchr-evex.S        |   5 +-
> >  sysdeps/x86_64/multiarch/memchr-sse2.S        | 363 +++++++++++++++++-
> >  sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S |   7 +-
> >  sysdeps/x86_64/multiarch/rawmemchr-avx2.S     |   7 +-
> >  sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S |   8 +-
> >  sysdeps/x86_64/multiarch/rawmemchr-evex.S     |   7 +-
> >  sysdeps/x86_64/multiarch/rawmemchr-sse2.S     | 198 +++++++++-
> >  sysdeps/x86_64/multiarch/rtld-memchr.S        |  18 +
> >  sysdeps/x86_64/multiarch/rtld-rawmemchr.S     |  18 +
> >  sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S   |   7 +-
> >  sysdeps/x86_64/multiarch/wmemchr-avx2.S       |   7 +-
> >  sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S   |   8 +-
> >  sysdeps/x86_64/multiarch/wmemchr-evex.S       |   7 +-
> >  sysdeps/x86_64/multiarch/wmemchr-sse2.S       |   9 +-
> >  sysdeps/x86_64/rawmemchr.S                    | 184 +--------
> >  sysdeps/x86_64/wmemchr.S                      |  28 ++
> >  21 files changed, 740 insertions(+), 612 deletions(-)
> >  create mode 100644 sysdeps/x86_64/multiarch/rtld-memchr.S
> >  create mode 100644 sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> >  create mode 100644 sysdeps/x86_64/wmemchr.S
> >
> > diff --git a/sysdeps/x86_64/isa-default-impl.h b/sysdeps/x86_64/isa-default-impl.h
> > index 34634668e5..b374a38b8b 100644
> > --- a/sysdeps/x86_64/isa-default-impl.h
> > +++ b/sysdeps/x86_64/isa-default-impl.h
> > @@ -46,4 +46,12 @@
> >  # error "Unsupported ISA Level!"
> >  #endif
> >
> > +#if IS_IN(rtld) && !defined USE_MULTIARCH
> > +#  error "RTLD version should only exist in multiarch build"
> > +#endif
> > +
> > +#if defined USE_MULTIARCH && !IS_IN(rtld)
> > +#  error "Multiarch build should not use ISA_DEFAULT_IMPL without RTLD"
> > +#endif
>
> Please do
>
> #if IS_IN (rtld)

Fixed in v12.
> #else
> #endif
>
> >  #include ISA_DEFAULT_IMPL
> > diff --git a/sysdeps/x86_64/memchr.S b/sysdeps/x86_64/memchr.S
> > index a160fd9b00..20b43508c4 100644
> > --- a/sysdeps/x86_64/memchr.S
> > +++ b/sysdeps/x86_64/memchr.S
> > @@ -15,358 +15,13 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#include <sysdep.h>
> > +#define MEMCHR __memchr
> >
> > -#ifdef USE_AS_WMEMCHR
> > -# define MEMCHR                wmemchr
> > -# define PCMPEQ                pcmpeqd
> > -# define CHAR_PER_VEC  4
> > -#else
> > -# define MEMCHR                memchr
> > -# define PCMPEQ                pcmpeqb
> > -# define CHAR_PER_VEC  16
> > -#endif
> > +#define DEFAULT_IMPL_V1        "multiarch/memchr-sse2.S"
> > +#define DEFAULT_IMPL_V3        "multiarch/memchr-avx2.S"
> > +#define DEFAULT_IMPL_V4        "multiarch/memchr-evex.S"
> >
> > -/* fast SSE2 version with using pmaxub and 64 byte loop */
> > +#include "isa-default-impl.h"
> >
> > -       .text
> > -ENTRY(MEMCHR)
> > -       movd    %esi, %xmm1
> > -       mov     %edi, %ecx
> > -
> > -#ifdef __ILP32__
> > -       /* Clear the upper 32 bits.  */
> > -       movl    %edx, %edx
> > -#endif
> > -#ifdef USE_AS_WMEMCHR
> > -       test    %RDX_LP, %RDX_LP
> > -       jz      L(return_null)
> > -#else
> > -       punpcklbw %xmm1, %xmm1
> > -       test    %RDX_LP, %RDX_LP
> > -       jz      L(return_null)
> > -       punpcklbw %xmm1, %xmm1
> > -#endif
> > -
> > -       and     $63, %ecx
> > -       pshufd  $0, %xmm1, %xmm1
> > -
> > -       cmp     $48, %ecx
> > -       ja      L(crosscache)
> > -
> > -       movdqu  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -
> > -       jnz     L(matches_1)
> > -       sub     $CHAR_PER_VEC, %rdx
> > -       jbe     L(return_null)
> > -       add     $16, %rdi
> > -       and     $15, %ecx
> > -       and     $-16, %rdi
> > -#ifdef USE_AS_WMEMCHR
> > -       shr     $2, %ecx
> > -#endif
> > -       add     %rcx, %rdx
> > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > -       jbe     L(exit_loop)
> > -       jmp     L(loop_prolog)
> > -
> > -       .p2align 4
> > -L(crosscache):
> > -       and     $15, %ecx
> > -       and     $-16, %rdi
> > -       movdqa  (%rdi), %xmm0
> > -
> > -       PCMPEQ  %xmm1, %xmm0
> > -       /* Check if there is a match.  */
> > -       pmovmskb %xmm0, %eax
> > -       /* Remove the leading bytes.  */
> > -       sar     %cl, %eax
> > -       test    %eax, %eax
> > -       je      L(unaligned_no_match)
> > -       /* Check which byte is a match.  */
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       add     %rdi, %rax
> > -       add     %rcx, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(unaligned_no_match):
> > -       /* "rcx" is less than 16.  Calculate "rdx + rcx - 16" by using
> > -          "rdx - (16 - rcx)" instead of "(rdx + rcx) - 16" to void
> > -          possible addition overflow.  */
> > -       neg     %rcx
> > -       add     $16, %rcx
> > -#ifdef USE_AS_WMEMCHR
> > -       shr     $2, %ecx
> > -#endif
> > -       sub     %rcx, %rdx
> > -       jbe     L(return_null)
> > -       add     $16, %rdi
> > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > -       jbe     L(exit_loop)
> > -
> > -       .p2align 4
> > -L(loop_prolog):
> > -       movdqa  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       PCMPEQ  %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       movdqa  48(%rdi), %xmm4
> > -       PCMPEQ  %xmm1, %xmm4
> > -       add     $64, %rdi
> > -       pmovmskb %xmm4, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches0)
> > -
> > -       test    $0x3f, %rdi
> > -       jz      L(align64_loop)
> > -
> > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > -       jbe     L(exit_loop)
> > -
> > -       movdqa  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       PCMPEQ  %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       movdqa  48(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -
> > -       add     $64, %rdi
> > -       test    %eax, %eax
> > -       jnz     L(matches0)
> > -
> > -       mov     %rdi, %rcx
> > -       and     $-64, %rdi
> > -       and     $63, %ecx
> > -#ifdef USE_AS_WMEMCHR
> > -       shr     $2, %ecx
> > -#endif
> > -       add     %rcx, %rdx
> > -
> > -       .p2align 4
> > -L(align64_loop):
> > -       sub     $(CHAR_PER_VEC * 4), %rdx
> > -       jbe     L(exit_loop)
> > -       movdqa  (%rdi), %xmm0
> > -       movdqa  16(%rdi), %xmm2
> > -       movdqa  32(%rdi), %xmm3
> > -       movdqa  48(%rdi), %xmm4
> > -
> > -       PCMPEQ  %xmm1, %xmm0
> > -       PCMPEQ  %xmm1, %xmm2
> > -       PCMPEQ  %xmm1, %xmm3
> > -       PCMPEQ  %xmm1, %xmm4
> > -
> > -       pmaxub  %xmm0, %xmm3
> > -       pmaxub  %xmm2, %xmm4
> > -       pmaxub  %xmm3, %xmm4
> > -       pmovmskb %xmm4, %eax
> > -
> > -       add     $64, %rdi
> > -
> > -       test    %eax, %eax
> > -       jz      L(align64_loop)
> > -
> > -       sub     $64, %rdi
> > -
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -
> > -       PCMPEQ  48(%rdi), %xmm1
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       pmovmskb %xmm1, %eax
> > -       bsf     %eax, %eax
> > -       lea     48(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(exit_loop):
> > -       add     $(CHAR_PER_VEC * 2), %edx
> > -       jle     L(exit_loop_32)
> > -
> > -       movdqa  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       PCMPEQ  %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       PCMPEQ  %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32_1)
> > -       sub     $CHAR_PER_VEC, %edx
> > -       jle     L(return_null)
> > -
> > -       PCMPEQ  48(%rdi), %xmm1
> > -       pmovmskb %xmm1, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches48_1)
> > -       xor     %eax, %eax
> > -       ret
> > -
> > -       .p2align 4
> > -L(exit_loop_32):
> > -       add     $(CHAR_PER_VEC * 2), %edx
> > -       movdqa  (%rdi), %xmm0
> > -       PCMPEQ  %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches_1)
> > -       sub     $CHAR_PER_VEC, %edx
> > -       jbe     L(return_null)
> > -
> > -       PCMPEQ  16(%rdi), %xmm1
> > -       pmovmskb %xmm1, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16_1)
> > -       xor     %eax, %eax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches0):
> > -       bsf     %eax, %eax
> > -       lea     -16(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches):
> > -       bsf     %eax, %eax
> > -       add     %rdi, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches16):
> > -       bsf     %eax, %eax
> > -       lea     16(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches32):
> > -       bsf     %eax, %eax
> > -       lea     32(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches_1):
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       add     %rdi, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches16_1):
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       lea     16(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches32_1):
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       lea     32(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches48_1):
> > -       bsf     %eax, %eax
> > -#ifdef USE_AS_WMEMCHR
> > -       mov     %eax, %esi
> > -       shr     $2, %esi
> > -       sub     %rsi, %rdx
> > -#else
> > -       sub     %rax, %rdx
> > -#endif
> > -       jbe     L(return_null)
> > -       lea     48(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(return_null):
> > -       xor     %eax, %eax
> > -       ret
> > -END(MEMCHR)
> > -
> > -#ifndef USE_AS_WMEMCHR
> > -strong_alias (memchr, __memchr)
> > +weak_alias (__memchr, memchr)
> >  libc_hidden_builtin_def(memchr)
> > -#endif
> > diff --git a/sysdeps/x86_64/multiarch/ifunc-evex.h b/sysdeps/x86_64/multiarch/ifunc-evex.h
> > index b8f7a12ea2..856c6261f8 100644
> > --- a/sysdeps/x86_64/multiarch/ifunc-evex.h
> > +++ b/sysdeps/x86_64/multiarch/ifunc-evex.h
> > @@ -19,24 +19,28 @@
> >
> >  #include <init-arch.h>
> >
> > -extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
> > -extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> > -extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
> >  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;
> >  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex_rtm) attribute_hidden;
> >
> > +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
> > +extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
> > +
> > +extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
> >
> >  static inline void *
> >  IFUNC_SELECTOR (void)
> >  {
> > -  const struct cpu_features* cpu_features = __get_cpu_features ();
> > -
> > -  if (CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> > -      && CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> > -      && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load))
> > +  const struct cpu_features *cpu_features = __get_cpu_features ();
> > +
> > +  /* NB: The X86_ISA_* feature check macros are evaluated at
> > +     compile time.  */
> > +  if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX2)
> > +      && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, BMI2)
> > +      && X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> > +                                     AVX_Fast_Unaligned_Load))
> >      {
> > -      if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
> > -         && CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
> > +      if (X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
> > +         && X86_ISA_CPU_FEATURE_USABLE_P (cpu_features, AVX512BW))
> >         {
> >           if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
> >             return OPTIMIZE (evex_rtm);
> > @@ -47,9 +51,12 @@ IFUNC_SELECTOR (void)
> >        if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
> >         return OPTIMIZE (avx2_rtm);
> >
> > -      if (!CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_VZEROUPPER))
> > +      if (X86_ISA_CPU_FEATURES_ARCH_P (cpu_features,
> > +                                      Prefer_No_VZEROUPPER))
> >         return OPTIMIZE (avx2);
> >      }
> >
> > +  /* This is unreachable (compile time checked) if ISA level >= 3
> > +     so no need for a robust fallback here.  */
> >    return OPTIMIZE (sse2);
> >  }
> > diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > index 883362f63d..bf52cf96d0 100644
> > --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > @@ -25,7 +25,8 @@
> >
> >  /* Fill ARRAY of MAX elements with IFUNC implementations for function
> >     NAME supported on target machine and return the number of valid
> > -   entries.  */
> > +   entries.  Each set of implementations for a given function is sorted in
> > +   descending order by ISA level.  */
> >
> >  size_t
> >  __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > @@ -53,24 +54,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> >
> >    /* Support sysdeps/x86_64/multiarch/memchr.c.  */
> >    IFUNC_IMPL (i, name, memchr,
> > -             IFUNC_IMPL_ADD (array, i, memchr,
> > -                             CPU_FEATURE_USABLE (AVX2),
> > -                             __memchr_avx2)
> > -             IFUNC_IMPL_ADD (array, i, memchr,
> > -                             (CPU_FEATURE_USABLE (AVX2)
> > -                              && CPU_FEATURE_USABLE (RTM)),
> > -                             __memchr_avx2_rtm)
> > -             IFUNC_IMPL_ADD (array, i, memchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, memchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __memchr_evex)
> > -             IFUNC_IMPL_ADD (array, i, memchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, memchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __memchr_evex_rtm)
> > -             IFUNC_IMPL_ADD (array, i, memchr, 1, __memchr_sse2))
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, memchr,
> > +                             CPU_FEATURE_USABLE (AVX2),
> > +                             __memchr_avx2)
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, memchr,
> > +                             (CPU_FEATURE_USABLE (AVX2)
> > +                              && CPU_FEATURE_USABLE (RTM)),
> > +                             __memchr_avx2_rtm)
> > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > +             X86_IFUNC_IMPL_ADD_V2 (array, i, memchr,
> > +                             1,
> > +                             __memchr_sse2))
> >
> >    /* Support sysdeps/x86_64/multiarch/memcmp.c.  */
> >    IFUNC_IMPL (i, name, memcmp,
> > @@ -288,24 +292,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> >
> >    /* Support sysdeps/x86_64/multiarch/rawmemchr.c.  */
> >    IFUNC_IMPL (i, name, rawmemchr,
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > -                             CPU_FEATURE_USABLE (AVX2),
> > -                             __rawmemchr_avx2)
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > -                             (CPU_FEATURE_USABLE (AVX2)
> > -                              && CPU_FEATURE_USABLE (RTM)),
> > -                             __rawmemchr_avx2_rtm)
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, rawmemchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __rawmemchr_evex)
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, rawmemchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __rawmemchr_evex_rtm)
> > -             IFUNC_IMPL_ADD (array, i, rawmemchr, 1, __rawmemchr_sse2))
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, rawmemchr,
> > +                             CPU_FEATURE_USABLE (AVX2),
> > +                             __rawmemchr_avx2)
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, rawmemchr,
> > +                             (CPU_FEATURE_USABLE (AVX2)
> > +                              && CPU_FEATURE_USABLE (RTM)),
> > +                             __rawmemchr_avx2_rtm)
> > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > +             X86_IFUNC_IMPL_ADD_V2 (array, i, rawmemchr,
> > +                             1,
> > +                             __rawmemchr_sse2))
> >
> >    /* Support sysdeps/x86_64/multiarch/strlen.c.  */
> >    IFUNC_IMPL (i, name, strlen,
> > @@ -748,24 +755,27 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> >
> >    /* Support sysdeps/x86_64/multiarch/wmemchr.c.  */
> >    IFUNC_IMPL (i, name, wmemchr,
> > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > -                             CPU_FEATURE_USABLE (AVX2),
> > -                             __wmemchr_avx2)
> > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > -                             (CPU_FEATURE_USABLE (AVX2)
> > -                              && CPU_FEATURE_USABLE (RTM)),
> > -                             __wmemchr_avx2_rtm)
> > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, wmemchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __wmemchr_evex)
> > -             IFUNC_IMPL_ADD (array, i, wmemchr,
> > +             X86_IFUNC_IMPL_ADD_V4 (array, i, wmemchr,
> >                               (CPU_FEATURE_USABLE (AVX512VL)
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __wmemchr_evex_rtm)
> > -             IFUNC_IMPL_ADD (array, i, wmemchr, 1, __wmemchr_sse2))
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, wmemchr,
> > +                             CPU_FEATURE_USABLE (AVX2),
> > +                             __wmemchr_avx2)
> > +             X86_IFUNC_IMPL_ADD_V3 (array, i, wmemchr,
> > +                             (CPU_FEATURE_USABLE (AVX2)
> > +                              && CPU_FEATURE_USABLE (RTM)),
> > +                             __wmemchr_avx2_rtm)
> > +             /* Can be lowered to V1 if a V2 implementation is added.  */
> > +             X86_IFUNC_IMPL_ADD_V2 (array, i, wmemchr,
> > +                             1,
> > +                             __wmemchr_sse2))
> >
> >    /* Support sysdeps/x86_64/multiarch/wmemcmp.c.  */
> >    IFUNC_IMPL (i, name, wmemcmp,
> > diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S
> > index c5a256eb37..39be5f7083 100644
> > --- a/sysdeps/x86_64/multiarch/memchr-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/memchr-avx2.S
> > @@ -16,9 +16,10 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#if IS_IN (libc)
> > +#include <isa-level.h>
> > +#include <sysdep.h>
> >
> > -# include <sysdep.h>
> > +#if ISA_SHOULD_BUILD (3)
> >
> >  # ifndef MEMCHR
> >  #  define MEMCHR       __memchr_avx2
> > diff --git a/sysdeps/x86_64/multiarch/memchr-evex.S b/sysdeps/x86_64/multiarch/memchr-evex.S
> > index 0fd11b7632..0dd4f1dcce 100644
> > --- a/sysdeps/x86_64/multiarch/memchr-evex.S
> > +++ b/sysdeps/x86_64/multiarch/memchr-evex.S
> > @@ -16,9 +16,10 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#if IS_IN (libc)
> > +#include <isa-level.h>
> > +#include <sysdep.h>
> >
> > -# include <sysdep.h>
> > +#if ISA_SHOULD_BUILD (4)
> >
> >  # ifndef MEMCHR
> >  #  define MEMCHR       __memchr_evex
> > diff --git a/sysdeps/x86_64/multiarch/memchr-sse2.S b/sysdeps/x86_64/multiarch/memchr-sse2.S
> > index 2c6fdd41d6..8c561cd687 100644
> > --- a/sysdeps/x86_64/multiarch/memchr-sse2.S
> > +++ b/sysdeps/x86_64/multiarch/memchr-sse2.S
> > @@ -16,13 +16,360 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#if IS_IN (libc)
> > -# define memchr __memchr_sse2
> > +#include <isa-level.h>
> > +#include <sysdep.h>
> >
> > -# undef strong_alias
> > -# define strong_alias(memchr, __memchr)
> > -# undef libc_hidden_builtin_def
> > -# define libc_hidden_builtin_def(memchr)
> > -#endif
> > +/* MINIMUM_X86_ISA_LEVEL <= 2 because there is no V2 implementation
> > +   so we need this to build for ISA V2 builds. */
> > +#if ISA_SHOULD_BUILD (2)
> > +
> > +# ifndef MEMCHR
> > +#  define MEMCHR       __memchr_sse2
> > +# endif
> > +# ifdef USE_AS_WMEMCHR
> > +#  define PCMPEQ               pcmpeqd
> > +#  define CHAR_PER_VEC 4
> > +# else
> > +#  define PCMPEQ               pcmpeqb
> > +#  define CHAR_PER_VEC 16
> > +# endif
> > +
> > +/* fast SSE2 version with using pmaxub and 64 byte loop */
> > +
> > +       .text
> > +ENTRY(MEMCHR)
> > +       movd    %esi, %xmm1
> > +       mov     %edi, %ecx
> > +
> > +# ifdef __ILP32__
> > +       /* Clear the upper 32 bits.  */
> > +       movl    %edx, %edx
> > +# endif
> > +# ifdef USE_AS_WMEMCHR
> > +       test    %RDX_LP, %RDX_LP
> > +       jz      L(return_null)
> > +# else
> > +       punpcklbw %xmm1, %xmm1
> > +       test    %RDX_LP, %RDX_LP
> > +       jz      L(return_null)
> > +       punpcklbw %xmm1, %xmm1
> > +# endif
> > +
> > +       and     $63, %ecx
> > +       pshufd  $0, %xmm1, %xmm1
> > +
> > +       cmp     $48, %ecx
> > +       ja      L(crosscache)
> > +
> > +       movdqu  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +
> > +       jnz     L(matches_1)
> > +       sub     $CHAR_PER_VEC, %rdx
> > +       jbe     L(return_null)
> > +       add     $16, %rdi
> > +       and     $15, %ecx
> > +       and     $-16, %rdi
> > +# ifdef USE_AS_WMEMCHR
> > +       shr     $2, %ecx
> > +# endif
> > +       add     %rcx, %rdx
> > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > +       jbe     L(exit_loop)
> > +       jmp     L(loop_prolog)
> > +
> > +       .p2align 4
> > +L(crosscache):
> > +       and     $15, %ecx
> > +       and     $-16, %rdi
> > +       movdqa  (%rdi), %xmm0
> > +
> > +       PCMPEQ  %xmm1, %xmm0
> > +       /* Check if there is a match.  */
> > +       pmovmskb %xmm0, %eax
> > +       /* Remove the leading bytes.  */
> > +       sar     %cl, %eax
> > +       test    %eax, %eax
> > +       je      L(unaligned_no_match)
> > +       /* Check which byte is a match.  */
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       add     %rdi, %rax
> > +       add     %rcx, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(unaligned_no_match):
> > +       /* "rcx" is less than 16.  Calculate "rdx + rcx - 16" by using
> > +          "rdx - (16 - rcx)" instead of "(rdx + rcx) - 16" to void
> > +          possible addition overflow.  */
> > +       neg     %rcx
> > +       add     $16, %rcx
> > +# ifdef USE_AS_WMEMCHR
> > +       shr     $2, %ecx
> > +# endif
> > +       sub     %rcx, %rdx
> > +       jbe     L(return_null)
> > +       add     $16, %rdi
> > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > +       jbe     L(exit_loop)
> > +
> > +       .p2align 4
> > +L(loop_prolog):
> > +       movdqa  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       PCMPEQ  %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       movdqa  48(%rdi), %xmm4
> > +       PCMPEQ  %xmm1, %xmm4
> > +       add     $64, %rdi
> > +       pmovmskb %xmm4, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches0)
> > +
> > +       test    $0x3f, %rdi
> > +       jz      L(align64_loop)
> > +
> > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > +       jbe     L(exit_loop)
> > +
> > +       movdqa  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       PCMPEQ  %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       movdqa  48(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +
> > +       add     $64, %rdi
> > +       test    %eax, %eax
> > +       jnz     L(matches0)
> > +
> > +       mov     %rdi, %rcx
> > +       and     $-64, %rdi
> > +       and     $63, %ecx
> > +# ifdef USE_AS_WMEMCHR
> > +       shr     $2, %ecx
> > +# endif
> > +       add     %rcx, %rdx
> > +
> > +       .p2align 4
> > +L(align64_loop):
> > +       sub     $(CHAR_PER_VEC * 4), %rdx
> > +       jbe     L(exit_loop)
> > +       movdqa  (%rdi), %xmm0
> > +       movdqa  16(%rdi), %xmm2
> > +       movdqa  32(%rdi), %xmm3
> > +       movdqa  48(%rdi), %xmm4
> > +
> > +       PCMPEQ  %xmm1, %xmm0
> > +       PCMPEQ  %xmm1, %xmm2
> > +       PCMPEQ  %xmm1, %xmm3
> > +       PCMPEQ  %xmm1, %xmm4
> >
> > -#include "../memchr.S"
> > +       pmaxub  %xmm0, %xmm3
> > +       pmaxub  %xmm2, %xmm4
> > +       pmaxub  %xmm3, %xmm4
> > +       pmovmskb %xmm4, %eax
> > +
> > +       add     $64, %rdi
> > +
> > +       test    %eax, %eax
> > +       jz      L(align64_loop)
> > +
> > +       sub     $64, %rdi
> > +
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +
> > +       PCMPEQ  48(%rdi), %xmm1
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       pmovmskb %xmm1, %eax
> > +       bsf     %eax, %eax
> > +       lea     48(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(exit_loop):
> > +       add     $(CHAR_PER_VEC * 2), %edx
> > +       jle     L(exit_loop_32)
> > +
> > +       movdqa  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       PCMPEQ  %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       PCMPEQ  %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32_1)
> > +       sub     $CHAR_PER_VEC, %edx
> > +       jle     L(return_null)
> > +
> > +       PCMPEQ  48(%rdi), %xmm1
> > +       pmovmskb %xmm1, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches48_1)
> > +       xor     %eax, %eax
> > +       ret
> > +
> > +       .p2align 4
> > +L(exit_loop_32):
> > +       add     $(CHAR_PER_VEC * 2), %edx
> > +       movdqa  (%rdi), %xmm0
> > +       PCMPEQ  %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches_1)
> > +       sub     $CHAR_PER_VEC, %edx
> > +       jbe     L(return_null)
> > +
> > +       PCMPEQ  16(%rdi), %xmm1
> > +       pmovmskb %xmm1, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16_1)
> > +       xor     %eax, %eax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches0):
> > +       bsf     %eax, %eax
> > +       lea     -16(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches):
> > +       bsf     %eax, %eax
> > +       add     %rdi, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches16):
> > +       bsf     %eax, %eax
> > +       lea     16(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches32):
> > +       bsf     %eax, %eax
> > +       lea     32(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches_1):
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       add     %rdi, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches16_1):
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       lea     16(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches32_1):
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       lea     32(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches48_1):
> > +       bsf     %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +       mov     %eax, %esi
> > +       shr     $2, %esi
> > +       sub     %rsi, %rdx
> > +# else
> > +       sub     %rax, %rdx
> > +# endif
> > +       jbe     L(return_null)
> > +       lea     48(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(return_null):
> > +       xor     %eax, %eax
> > +       ret
> > +END(MEMCHR)
> > +#endif
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S b/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > index acc5f6e2fb..5c1dcd3ca7 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-avx2-rtm.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __rawmemchr_avx2_rtm
> > -#define USE_AS_RAWMEMCHR 1
> > +#ifndef RAWMEMCHR
> > +# define RAWMEMCHR     __rawmemchr_avx2_rtm
> > +#endif
> > +#define USE_AS_RAWMEMCHR       1
> > +#define MEMCHR RAWMEMCHR
> >
> >  #include "memchr-avx2-rtm.S"
>
> Will we ever use the RTM version as the default?
>
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-avx2.S b/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > index 128f9ea637..d6bff28757 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-avx2.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __rawmemchr_avx2
> > -#define USE_AS_RAWMEMCHR 1
> > +#ifndef RAWMEMCHR
> > +# define RAWMEMCHR     __rawmemchr_avx2
> > +#endif
> > +#define USE_AS_RAWMEMCHR       1
> > +#define MEMCHR RAWMEMCHR
> >
> >  #include "memchr-avx2.S"
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S b/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > index deda1ca395..8ff7f27c9c 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-evex-rtm.S
> > @@ -1,3 +1,7 @@
> > -#define MEMCHR __rawmemchr_evex_rtm
> > -#define USE_AS_RAWMEMCHR 1
> > +#ifndef RAWMEMCHR
> > +# define RAWMEMCHR     __rawmemchr_evex_rtm
> > +#endif
> > +#define USE_AS_RAWMEMCHR       1
> > +#define MEMCHR RAWMEMCHR
> > +
>
> Will we ever use the RTM version as the default?
>
> >  #include "memchr-evex-rtm.S"
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-evex.S b/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > index ec942b77ba..dc1c450699 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-evex.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __rawmemchr_evex
> > -#define USE_AS_RAWMEMCHR 1
> > +#ifndef RAWMEMCHR
> > +# define RAWMEMCHR     __rawmemchr_evex
> > +#endif
> > +#define USE_AS_RAWMEMCHR       1
> > +#define MEMCHR RAWMEMCHR
> >
> >  #include "memchr-evex.S"
> > diff --git a/sysdeps/x86_64/multiarch/rawmemchr-sse2.S b/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > index 3841c14c34..e2c2e20d85 100644
> > --- a/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > +++ b/sysdeps/x86_64/multiarch/rawmemchr-sse2.S
> > @@ -16,14 +16,192 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -/* Define multiple versions only for the definition in libc. */
> > -#if IS_IN (libc)
> > -# define __rawmemchr __rawmemchr_sse2
> > -
> > -# undef weak_alias
> > -# define weak_alias(__rawmemchr, rawmemchr)
> > -# undef libc_hidden_def
> > -# define libc_hidden_def(__rawmemchr)
> > -#endif
> > +#include <isa-level.h>
> > +#include <sysdep.h>
> > +
> > +/* MINIMUM_X86_ISA_LEVEL <= 2 because there is no V2 implementation
> > +   so we need this to build for ISA V2 builds. */
> > +#if ISA_SHOULD_BUILD (2)
> > +
> > +# ifndef RAWMEMCHR
> > +#  define RAWMEMCHR    __rawmemchr_sse2
> > +# endif
> > +
> > +       .text
> > +ENTRY (RAWMEMCHR)
> > +       movd    %rsi, %xmm1
> > +       mov     %rdi, %rcx
> > +
> > +       punpcklbw %xmm1, %xmm1
> > +       punpcklbw %xmm1, %xmm1
> > +
> > +       and     $63, %rcx
> > +       pshufd  $0, %xmm1, %xmm1
> > +
> > +       cmp     $48, %rcx
> > +       ja      L(crosscache)
> > +
> > +       movdqu  (%rdi), %xmm0
> > +       pcmpeqb %xmm1, %xmm0
> > +/* Check if there is a match.  */
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +
> > +       jnz     L(matches)
> > +       add     $16, %rdi
> > +       and     $-16, %rdi
> > +       jmp     L(loop_prolog)
> > +
> > +       .p2align 4
> > +L(crosscache):
> > +       and     $15, %rcx
> > +       and     $-16, %rdi
> > +       movdqa  (%rdi), %xmm0
> > +
> > +       pcmpeqb %xmm1, %xmm0
> > +/* Check if there is a match.  */
> > +       pmovmskb %xmm0, %eax
> > +/* Remove the leading bytes.  */
> > +       sar     %cl, %eax
> > +       test    %eax, %eax
> > +       je      L(unaligned_no_match)
> > +/* Check which byte is a match.  */
> > +       bsf     %eax, %eax
> > +
> > +       add     %rdi, %rax
> > +       add     %rcx, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(unaligned_no_match):
> > +       add     $16, %rdi
> > +
> > +       .p2align 4
> > +L(loop_prolog):
> > +       movdqa  (%rdi), %xmm0
> > +       pcmpeqb %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       pcmpeqb %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       pcmpeqb %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       movdqa  48(%rdi), %xmm4
> > +       pcmpeqb %xmm1, %xmm4
> > +       add     $64, %rdi
> > +       pmovmskb %xmm4, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches0)
> > +
> > +       test    $0x3f, %rdi
> > +       jz      L(align64_loop)
> > +
> > +       movdqa  (%rdi), %xmm0
> > +       pcmpeqb %xmm1, %xmm0
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       movdqa  16(%rdi), %xmm2
> > +       pcmpeqb %xmm1, %xmm2
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> >
> > -#include "../rawmemchr.S"
> > +       movdqa  32(%rdi), %xmm3
> > +       pcmpeqb %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       movdqa  48(%rdi), %xmm3
> > +       pcmpeqb %xmm1, %xmm3
> > +       pmovmskb %xmm3, %eax
> > +
> > +       add     $64, %rdi
> > +       test    %eax, %eax
> > +       jnz     L(matches0)
> > +
> > +       and     $-64, %rdi
> > +
> > +       .p2align 4
> > +L(align64_loop):
> > +       movdqa  (%rdi), %xmm0
> > +       movdqa  16(%rdi), %xmm2
> > +       movdqa  32(%rdi), %xmm3
> > +       movdqa  48(%rdi), %xmm4
> > +
> > +       pcmpeqb %xmm1, %xmm0
> > +       pcmpeqb %xmm1, %xmm2
> > +       pcmpeqb %xmm1, %xmm3
> > +       pcmpeqb %xmm1, %xmm4
> > +
> > +       pmaxub  %xmm0, %xmm3
> > +       pmaxub  %xmm2, %xmm4
> > +       pmaxub  %xmm3, %xmm4
> > +       pmovmskb %xmm4, %eax
> > +
> > +       add     $64, %rdi
> > +
> > +       test    %eax, %eax
> > +       jz      L(align64_loop)
> > +
> > +       sub     $64, %rdi
> > +
> > +       pmovmskb %xmm0, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches)
> > +
> > +       pmovmskb %xmm2, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches16)
> > +
> > +       movdqa  32(%rdi), %xmm3
> > +       pcmpeqb %xmm1, %xmm3
> > +
> > +       pcmpeqb 48(%rdi), %xmm1
> > +       pmovmskb %xmm3, %eax
> > +       test    %eax, %eax
> > +       jnz     L(matches32)
> > +
> > +       pmovmskb %xmm1, %eax
> > +       bsf     %eax, %eax
> > +       lea     48(%rdi, %rax), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches0):
> > +       bsf     %eax, %eax
> > +       lea     -16(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches):
> > +       bsf     %eax, %eax
> > +       add     %rdi, %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches16):
> > +       bsf     %eax, %eax
> > +       lea     16(%rax, %rdi), %rax
> > +       ret
> > +
> > +       .p2align 4
> > +L(matches32):
> > +       bsf     %eax, %eax
> > +       lea     32(%rax, %rdi), %rax
> > +       ret
> > +
> > +END (RAWMEMCHR)
> > +#endif
> > diff --git a/sysdeps/x86_64/multiarch/rtld-memchr.S b/sysdeps/x86_64/multiarch/rtld-memchr.S
> > new file mode 100644
> > index 0000000000..a14b192bed
> > --- /dev/null
> > +++ b/sysdeps/x86_64/multiarch/rtld-memchr.S
> > @@ -0,0 +1,18 @@
> > +/* Copyright (C) 2022 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#include "../memchr.S"
> > diff --git a/sysdeps/x86_64/multiarch/rtld-rawmemchr.S b/sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> > new file mode 100644
> > index 0000000000..5d4110a052
> > --- /dev/null
> > +++ b/sysdeps/x86_64/multiarch/rtld-rawmemchr.S
> > @@ -0,0 +1,18 @@
> > +/* Copyright (C) 2022 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#include "../rawmemchr.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S b/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > index 58ed21db01..2a1cff5b05 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-avx2-rtm.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __wmemchr_avx2_rtm
> > -#define USE_AS_WMEMCHR 1
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_avx2_rtm
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> >
> >  #include "memchr-avx2-rtm.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-avx2.S b/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > index 282854f1a1..2bf93fd84b 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-avx2.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __wmemchr_avx2
> > -#define USE_AS_WMEMCHR 1
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_avx2
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> >
> >  #include "memchr-avx2.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S b/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > index a346cd35a1..c67309e8a1 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-evex-rtm.S
> > @@ -1,3 +1,7 @@
> > -#define MEMCHR __wmemchr_evex_rtm
> > -#define USE_AS_WMEMCHR 1
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_evex_rtm
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> > +
> >  #include "memchr-evex-rtm.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-evex.S b/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > index 06cd0f9f5a..5512d5cdc3 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-evex.S
> > @@ -1,4 +1,7 @@
> > -#define MEMCHR __wmemchr_evex
> > -#define USE_AS_WMEMCHR 1
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_evex
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> >
> >  #include "memchr-evex.S"
> > diff --git a/sysdeps/x86_64/multiarch/wmemchr-sse2.S b/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > index 70a965d552..b675a070d4 100644
> > --- a/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > +++ b/sysdeps/x86_64/multiarch/wmemchr-sse2.S
> > @@ -1,4 +1,7 @@
> > -#define USE_AS_WMEMCHR 1
> > -#define wmemchr __wmemchr_sse2
> > +#ifndef WMEMCHR
> > +# define WMEMCHR       __wmemchr_sse2
> > +#endif
> > +#define USE_AS_WMEMCHR 1
> > +#define MEMCHR WMEMCHR
> >
> > -#include "../memchr.S"
> > +#include "memchr-sse2.S"
> > diff --git a/sysdeps/x86_64/rawmemchr.S b/sysdeps/x86_64/rawmemchr.S
> > index 4c1a3383b9..ba7e5202e6 100644
> > --- a/sysdeps/x86_64/rawmemchr.S
> > +++ b/sysdeps/x86_64/rawmemchr.S
> > @@ -17,185 +17,13 @@
> >     License along with the GNU C Library; if not, see
> >     <https://www.gnu.org/licenses/>.  */
> >
> > -#include <sysdep.h>
> > +#define RAWMEMCHR      __rawmemchr
> >
> > -       .text
> > -ENTRY (__rawmemchr)
> > -       movd    %rsi, %xmm1
> > -       mov     %rdi, %rcx
> > +#define DEFAULT_IMPL_V1        "multiarch/rawmemchr-sse2.S"
> > +#define DEFAULT_IMPL_V3        "multiarch/rawmemchr-avx2.S"
> > +#define DEFAULT_IMPL_V4        "multiarch/rawmemchr-evex.S"
> >
> > -       punpcklbw %xmm1, %xmm1
> > -       punpcklbw %xmm1, %xmm1
> > -
> > -       and     $63, %rcx
> > -       pshufd  $0, %xmm1, %xmm1
> > -
> > -       cmp     $48, %rcx
> > -       ja      L(crosscache)
> > -
> > -       movdqu  (%rdi), %xmm0
> > -       pcmpeqb %xmm1, %xmm0
> > -/* Check if there is a match.  */
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -
> > -       jnz     L(matches)
> > -       add     $16, %rdi
> > -       and     $-16, %rdi
> > -       jmp     L(loop_prolog)
> > -
> > -       .p2align 4
> > -L(crosscache):
> > -       and     $15, %rcx
> > -       and     $-16, %rdi
> > -       movdqa  (%rdi), %xmm0
> > -
> > -       pcmpeqb %xmm1, %xmm0
> > -/* Check if there is a match.  */
> > -       pmovmskb %xmm0, %eax
> > -/* Remove the leading bytes.  */
> > -       sar     %cl, %eax
> > -       test    %eax, %eax
> > -       je      L(unaligned_no_match)
> > -/* Check which byte is a match.  */
> > -       bsf     %eax, %eax
> > -
> > -       add     %rdi, %rax
> > -       add     %rcx, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(unaligned_no_match):
> > -       add     $16, %rdi
> > -
> > -       .p2align 4
> > -L(loop_prolog):
> > -       movdqa  (%rdi), %xmm0
> > -       pcmpeqb %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       pcmpeqb %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       pcmpeqb %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       movdqa  48(%rdi), %xmm4
> > -       pcmpeqb %xmm1, %xmm4
> > -       add     $64, %rdi
> > -       pmovmskb %xmm4, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches0)
> > -
> > -       test    $0x3f, %rdi
> > -       jz      L(align64_loop)
> > -
> > -       movdqa  (%rdi), %xmm0
> > -       pcmpeqb %xmm1, %xmm0
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       movdqa  16(%rdi), %xmm2
> > -       pcmpeqb %xmm1, %xmm2
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       pcmpeqb %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       movdqa  48(%rdi), %xmm3
> > -       pcmpeqb %xmm1, %xmm3
> > -       pmovmskb %xmm3, %eax
> > -
> > -       add     $64, %rdi
> > -       test    %eax, %eax
> > -       jnz     L(matches0)
> > -
> > -       and     $-64, %rdi
> > -
> > -       .p2align 4
> > -L(align64_loop):
> > -       movdqa  (%rdi), %xmm0
> > -       movdqa  16(%rdi), %xmm2
> > -       movdqa  32(%rdi), %xmm3
> > -       movdqa  48(%rdi), %xmm4
> > -
> > -       pcmpeqb %xmm1, %xmm0
> > -       pcmpeqb %xmm1, %xmm2
> > -       pcmpeqb %xmm1, %xmm3
> > -       pcmpeqb %xmm1, %xmm4
> > -
> > -       pmaxub  %xmm0, %xmm3
> > -       pmaxub  %xmm2, %xmm4
> > -       pmaxub  %xmm3, %xmm4
> > -       pmovmskb %xmm4, %eax
> > -
> > -       add     $64, %rdi
> > -
> > -       test    %eax, %eax
> > -       jz      L(align64_loop)
> > -
> > -       sub     $64, %rdi
> > -
> > -       pmovmskb %xmm0, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches)
> > -
> > -       pmovmskb %xmm2, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches16)
> > -
> > -       movdqa  32(%rdi), %xmm3
> > -       pcmpeqb %xmm1, %xmm3
> > -
> > -       pcmpeqb 48(%rdi), %xmm1
> > -       pmovmskb %xmm3, %eax
> > -       test    %eax, %eax
> > -       jnz     L(matches32)
> > -
> > -       pmovmskb %xmm1, %eax
> > -       bsf     %eax, %eax
> > -       lea     48(%rdi, %rax), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches0):
> > -       bsf     %eax, %eax
> > -       lea     -16(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches):
> > -       bsf     %eax, %eax
> > -       add     %rdi, %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches16):
> > -       bsf     %eax, %eax
> > -       lea     16(%rax, %rdi), %rax
> > -       ret
> > -
> > -       .p2align 4
> > -L(matches32):
> > -       bsf     %eax, %eax
> > -       lea     32(%rax, %rdi), %rax
> > -       ret
> > -
> > -END (__rawmemchr)
> > +#include "isa-default-impl.h"
> >
> >  weak_alias (__rawmemchr, rawmemchr)
> > -libc_hidden_builtin_def (__rawmemchr)
> > +libc_hidden_def (__rawmemchr)
> > diff --git a/sysdeps/x86_64/wmemchr.S b/sysdeps/x86_64/wmemchr.S
> > new file mode 100644
> > index 0000000000..eef91e556b
> > --- /dev/null
> > +++ b/sysdeps/x86_64/wmemchr.S
> > @@ -0,0 +1,28 @@
> > +/* Copyright (C) 2011-2022 Free Software Foundation, Inc.
> > +   This file is part of the GNU C Library.
> > +
> > +   The GNU C Library is free software; you can redistribute it and/or
> > +   modify it under the terms of the GNU Lesser General Public
> > +   License as published by the Free Software Foundation; either
> > +   version 2.1 of the License, or (at your option) any later version.
> > +
> > +   The GNU C Library is distributed in the hope that it will be useful,
> > +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> > +   Lesser General Public License for more details.
> > +
> > +   You should have received a copy of the GNU Lesser General Public
> > +   License along with the GNU C Library; if not, see
> > +   <https://www.gnu.org/licenses/>.  */
> > +
> > +#define WMEMCHR        __wmemchr
> > +
> > +#define DEFAULT_IMPL_V1        "multiarch/wmemchr-sse2.S"
> > +#define DEFAULT_IMPL_V3        "multiarch/wmemchr-avx2.S"
> > +#define DEFAULT_IMPL_V4        "multiarch/wmemchr-evex.S"
> > +
> > +#include "isa-default-impl.h"
> > +
> > +libc_hidden_def (__wmemchr)
> > +weak_alias (__wmemchr, wmemchr)
> > +libc_hidden_weak (wmemchr)
> > --
> > 2.34.1
> >
>
>
> --
> H.J.