[v2,3/3] x86: Optimize memchr-evex.S

No bug. This commit optimizes memchr-evex.S. The optimizations include
replacing some branches with cmovcc, avoiding some branches entirely
in the less_4x_vec case, making the page cross logic less strict,
saving some ALU in the alignment process, and most importantly
increasing ILP in the 4x loop. test-memchr, test-rawmemchr, and
test-wmemchr are all passing.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
---
 sysdeps/x86_64/multiarch/memchr-evex.S | 547 +++++++++++++++----------
 1 file changed, 322 insertions(+), 225 deletions(-)

On Mon, May 03, 2021 at 04:06:55PM -0400, Noah Goldstein wrote:
> No bug. This commit optimizes memchr-evex.S. The optimizations include
> replacing some branches with cmovcc, avoiding some branches entirely
> in the less_4x_vec case, making the page cross logic less strict,
> saving some ALU in the alignment process, and most importantly
> increasing ILP in the 4x loop. test-memchr, test-rawmemchr, and
> test-wmemchr are all passing.
> 
> Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> ---
>  sysdeps/x86_64/multiarch/memchr-evex.S | 547 +++++++++++++++----------
>  1 file changed, 322 insertions(+), 225 deletions(-)
> 
> diff --git a/sysdeps/x86_64/multiarch/memchr-evex.S b/sysdeps/x86_64/multiarch/memchr-evex.S
> index 6dd5d67b90..147d7aa8ee 100644
> --- a/sysdeps/x86_64/multiarch/memchr-evex.S
> +++ b/sysdeps/x86_64/multiarch/memchr-evex.S
> @@ -26,14 +26,28 @@
>  
>  # ifdef USE_AS_WMEMCHR
>  #  define VPBROADCAST	vpbroadcastd
> -#  define VPCMP		vpcmpd
> -#  define SHIFT_REG	r8d
> +#  define VPMINU	vpminud
> +#  define VPCMP	vpcmpd
> +#  define VPCMPEQ	vpcmpeqd
> +#  define CHAR_SIZE	4
>  # else
>  #  define VPBROADCAST	vpbroadcastb
> -#  define VPCMP		vpcmpb
> -#  define SHIFT_REG	ecx
> +#  define VPMINU	vpminub
> +#  define VPCMP	vpcmpb
> +#  define VPCMPEQ	vpcmpeqb
> +#  define CHAR_SIZE	1
>  # endif
>  
> +# ifdef USE_AS_RAWMEMCHR
> +#  define RAW_PTR_REG	rcx
> +#  define ALGN_PTR_REG	rdi
> +# else
> +#  define RAW_PTR_REG	rdi
> +#  define ALGN_PTR_REG	rcx
> +# endif
> +
> +# define XZERO		xmm23
> +# define YZERO		ymm23

Please rename XZERO/YZERO to XMMZERO/YMMZERO.  OK with this change.

Thanks.

>  # define XMMMATCH	xmm16
>  # define YMMMATCH	ymm16
>  # define YMM1		ymm17
> @@ -44,6 +58,8 @@
>  # define YMM6		ymm22
>  
>  # define VEC_SIZE 32
> +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
> +# define PAGE_SIZE 4096
>  
>  	.section .text.evex,"ax",@progbits
>  ENTRY (MEMCHR)
> @@ -51,11 +67,7 @@ ENTRY (MEMCHR)
>  	/* Check for zero length.  */
>  	test	%RDX_LP, %RDX_LP
>  	jz	L(zero)
> -# endif
> -	movl	%edi, %ecx
> -# ifdef USE_AS_WMEMCHR
> -	shl	$2, %RDX_LP
> -# else
> +
>  #  ifdef __ILP32__
>  	/* Clear the upper 32 bits.  */
>  	movl	%edx, %edx
> @@ -64,318 +76,403 @@ ENTRY (MEMCHR)
>  	/* Broadcast CHAR to YMMMATCH.  */
>  	VPBROADCAST %esi, %YMMMATCH
>  	/* Check if we may cross page boundary with one vector load.  */
> -	andl	$(2 * VEC_SIZE - 1), %ecx
> -	cmpl	$VEC_SIZE, %ecx
> -	ja	L(cros_page_boundary)
> +	movl	%edi, %eax
> +	andl	$(PAGE_SIZE - 1), %eax
> +	cmpl	$(PAGE_SIZE - VEC_SIZE), %eax
> +	ja	L(cross_page_boundary)
>  
>  	/* Check the first VEC_SIZE bytes.  */
> -	VPCMP	$0, (%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> -	testl	%eax, %eax
> -
> +	VPCMP	$0, (%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
>  # ifndef USE_AS_RAWMEMCHR
> -	jnz	L(first_vec_x0_check)
> -	/* Adjust length and check the end of data.  */
> -	subq	$VEC_SIZE, %rdx
> -	jbe	L(zero)
> +	/* If length < CHAR_PER_VEC handle special.  */
> +	cmpq	$CHAR_PER_VEC, %rdx
> +	jbe	L(first_vec_x0)
> +# endif
> +	testl	%eax, %eax
> +	jz	L(aligned_more)
> +	tzcntl	%eax, %eax
> +# ifdef USE_AS_WMEMCHR
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	(%rdi, %rax, CHAR_SIZE), %rax
>  # else
> -	jnz	L(first_vec_x0)
> +	addq	%rdi, %rax
>  # endif
> -
> -	/* Align data for aligned loads in the loop.  */
> -	addq	$VEC_SIZE, %rdi
> -	andl	$(VEC_SIZE - 1), %ecx
> -	andq	$-VEC_SIZE, %rdi
> +	ret
>  
>  # ifndef USE_AS_RAWMEMCHR
> -	/* Adjust length.  */
> -	addq	%rcx, %rdx
> -
> -	subq	$(VEC_SIZE * 4), %rdx
> -	jbe	L(last_4x_vec_or_less)
> -# endif
> -	jmp	L(more_4x_vec)
> +L(zero):
> +	xorl	%eax, %eax
> +	ret
>  
> +	.p2align 5
> +L(first_vec_x0):
> +	/* Check if first match was before length.  */
> +	tzcntl	%eax, %eax
> +	xorl	%ecx, %ecx
> +	cmpl	%eax, %edx
> +	leaq	(%rdi, %rax, CHAR_SIZE), %rax
> +	cmovle	%rcx, %rax
> +	ret
> +# else
> +	/* NB: first_vec_x0 is 17 bytes which will leave
> +	   cross_page_boundary (which is relatively cold) close enough
> +	   to ideal alignment. So only realign L(cross_page_boundary) if
> +	   rawmemchr.  */
>  	.p2align 4
> -L(cros_page_boundary):
> -	andl	$(VEC_SIZE - 1), %ecx
> +# endif
> +L(cross_page_boundary):
> +	/* Save pointer before aligning as its original value is
> +	   necessary for computer return address if byte is found or
> +	   adjusting length if it is not and this is memchr.  */
> +	movq	%rdi, %rcx
> +	/* Align data to VEC_SIZE. ALGN_PTR_REG is rcx for memchr and rdi
> +	   for rawmemchr.  */
> +	andq	$-VEC_SIZE, %ALGN_PTR_REG
> +	VPCMP	$0, (%ALGN_PTR_REG), %YMMMATCH, %k0
> +	kmovd	%k0, %r8d
>  # ifdef USE_AS_WMEMCHR
> -	/* NB: Divide shift count by 4 since each bit in K1 represent 4
> +	/* NB: Divide shift count by 4 since each bit in K0 represent 4
>  	   bytes.  */
> -	movl	%ecx, %SHIFT_REG
> -	sarl	$2, %SHIFT_REG
> +	sarl	$2, %eax
> +# endif
> +# ifndef USE_AS_RAWMEMCHR
> +	movl	$(PAGE_SIZE / CHAR_SIZE), %esi
> +	subl	%eax, %esi
>  # endif
> -	andq	$-VEC_SIZE, %rdi
> -	VPCMP	$0, (%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> -	/* Remove the leading bytes.  */
> -	sarxl	%SHIFT_REG, %eax, %eax
> -	testl	%eax, %eax
> -	jz	L(aligned_more)
> -	tzcntl	%eax, %eax
>  # ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	sall	$2, %eax
> +	andl	$(CHAR_PER_VEC - 1), %eax
>  # endif
> +	/* Remove the leading bytes.  */
> +	sarxl	%eax, %r8d, %eax
>  # ifndef USE_AS_RAWMEMCHR
>  	/* Check the end of data.  */
> -	cmpq	%rax, %rdx
> -	jbe	L(zero)
> +	cmpq	%rsi, %rdx
> +	jbe	L(first_vec_x0)
> +# endif
> +	testl	%eax, %eax
> +	jz	L(cross_page_continue)
> +	tzcntl	%eax, %eax
> +# ifdef USE_AS_WMEMCHR
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	(%RAW_PTR_REG, %rax, CHAR_SIZE), %rax
> +# else
> +	addq	%RAW_PTR_REG, %rax
>  # endif
> -	addq	%rdi, %rax
> -	addq	%rcx, %rax
>  	ret
>  
>  	.p2align 4
> -L(aligned_more):
> -# ifndef USE_AS_RAWMEMCHR
> -        /* Calculate "rdx + rcx - VEC_SIZE" with "rdx - (VEC_SIZE - rcx)"
> -	   instead of "(rdx + rcx) - VEC_SIZE" to void possible addition
> -	   overflow.  */
> -	negq	%rcx
> -	addq	$VEC_SIZE, %rcx
> +L(first_vec_x1):
> +	tzcntl	%eax, %eax
> +	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
> +	ret
>  
> -	/* Check the end of data.  */
> -	subq	%rcx, %rdx
> -	jbe	L(zero)
> -# endif
> +	.p2align 4
> +L(first_vec_x2):
> +	tzcntl	%eax, %eax
> +	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> +	ret
>  
> -	addq	$VEC_SIZE, %rdi
> +	.p2align 4
> +L(first_vec_x3):
> +	tzcntl	%eax, %eax
> +	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
> +	ret
>  
> -# ifndef USE_AS_RAWMEMCHR
> -	subq	$(VEC_SIZE * 4), %rdx
> -	jbe	L(last_4x_vec_or_less)
> -# endif
> +	.p2align 4
> +L(first_vec_x4):
> +	tzcntl	%eax, %eax
> +	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
> +	ret
>  
> -L(more_4x_vec):
> +	.p2align 5
> +L(aligned_more):
>  	/* Check the first 4 * VEC_SIZE.  Only one VEC_SIZE at a time
>  	   since data is only aligned to VEC_SIZE.  */
> -	VPCMP	$0, (%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> -	testl	%eax, %eax
> -	jnz	L(first_vec_x0)
>  
> -	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> +# ifndef USE_AS_RAWMEMCHR
> +	/* Align data to VEC_SIZE.  */
> +L(cross_page_continue):
> +	xorl	%ecx, %ecx
> +	subl	%edi, %ecx
> +	andq	$-VEC_SIZE, %rdi
> +	/* esi is for adjusting length to see if near the end.  */
> +	leal	(VEC_SIZE * 5)(%rdi, %rcx), %esi
> +#  ifdef USE_AS_WMEMCHR
> +	/* NB: Divide bytes by 4 to get the wchar_t count.  */
> +	sarl	$2, %esi
> +#  endif
> +# else
> +	andq	$-VEC_SIZE, %rdi
> +L(cross_page_continue):
> +# endif
> +	/* Load first VEC regardless.  */
> +	VPCMP	$0, (VEC_SIZE)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
> +# ifndef USE_AS_RAWMEMCHR
> +	/* Adjust length. If near end handle specially.  */
> +	subq	%rsi, %rdx
> +	jbe	L(last_4x_vec_or_less)
> +# endif
>  	testl	%eax, %eax
>  	jnz	L(first_vec_x1)
>  
> -	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> +	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
>  	testl	%eax, %eax
>  	jnz	L(first_vec_x2)
>  
> -	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> +	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
>  	testl	%eax, %eax
>  	jnz	L(first_vec_x3)
>  
> -	addq	$(VEC_SIZE * 4), %rdi
> +	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
> +	testl	%eax, %eax
> +	jnz	L(first_vec_x4)
> +
>  
>  # ifndef USE_AS_RAWMEMCHR
> -	subq	$(VEC_SIZE * 4), %rdx
> -	jbe	L(last_4x_vec_or_less)
> -# endif
> +	/* Check if at last CHAR_PER_VEC * 4 length.  */
> +	subq	$(CHAR_PER_VEC * 4), %rdx
> +	jbe	L(last_4x_vec_or_less_cmpeq)
> +	addq	$VEC_SIZE, %rdi
>  
> -	/* Align data to 4 * VEC_SIZE.  */
> -	movq	%rdi, %rcx
> -	andl	$(4 * VEC_SIZE - 1), %ecx
> +	/* Align data to VEC_SIZE * 4 for the loop and readjust length.
> +	 */
> +#  ifdef USE_AS_WMEMCHR
> +	movl	%edi, %ecx
>  	andq	$-(4 * VEC_SIZE), %rdi
> -
> -# ifndef USE_AS_RAWMEMCHR
> -	/* Adjust length.  */
> +	andl	$(VEC_SIZE * 4 - 1), %ecx
> +	/* NB: Divide bytes by 4 to get the wchar_t count.  */
> +	sarl	$2, %ecx
>  	addq	%rcx, %rdx
> +#  else
> +	addq	%rdi, %rdx
> +	andq	$-(4 * VEC_SIZE), %rdi
> +	subq	%rdi, %rdx
> +#  endif
> +# else
> +	addq	$VEC_SIZE, %rdi
> +	andq	$-(4 * VEC_SIZE), %rdi
>  # endif
>  
> +	vpxorq	%XZERO, %XZERO, %XZERO
> +
> +	/* Compare 4 * VEC at a time forward.  */
>  	.p2align 4
>  L(loop_4x_vec):
> -	/* Compare 4 * VEC at a time forward.  */
> -	VPCMP	$0, (%rdi), %YMMMATCH, %k1
> -	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k2
> -	kord	%k1, %k2, %k5
> -	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k3
> -	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k4
> -
> -	kord	%k3, %k4, %k6
> -	kortestd %k5, %k6
> -	jnz	L(4x_vec_end)
> -
> -	addq	$(VEC_SIZE * 4), %rdi
> -
> +	/* It would be possible to save some instructions using 4x VPCMP
> +	   but bottleneck on port 5 makes it not woth it.  */
> +	VPCMP	$4, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k1
> +	/* xor will set bytes match esi to zero.  */
> +	vpxorq	(VEC_SIZE * 5)(%rdi), %YMMMATCH, %YMM2
> +	vpxorq	(VEC_SIZE * 6)(%rdi), %YMMMATCH, %YMM3
> +	VPCMP	$0, (VEC_SIZE * 7)(%rdi), %YMMMATCH, %k3
> +	/* Reduce VEC2 / VEC3 with min and VEC1 with zero mask.  */
> +	VPMINU	%YMM2, %YMM3, %YMM3 {%k1} {z}
> +	VPCMP	$0, %YMM3, %YZERO, %k2
>  # ifdef USE_AS_RAWMEMCHR
> -	jmp	L(loop_4x_vec)
> +	subq	$-(VEC_SIZE * 4), %rdi
> +	kortestd %k2, %k3
> +	jz	L(loop_4x_vec)
>  # else
> -	subq	$(VEC_SIZE * 4), %rdx
> +	kortestd %k2, %k3
> +	jnz	L(loop_4x_vec_end)
> +
> +	subq	$-(VEC_SIZE * 4), %rdi
> +
> +	subq	$(CHAR_PER_VEC * 4), %rdx
>  	ja	L(loop_4x_vec)
>  
> +	/* Fall through into less than 4 remaining vectors of length case.
> +	 */
> +	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
> +	addq	$(VEC_SIZE * 3), %rdi
> +	.p2align 4
>  L(last_4x_vec_or_less):
> -	/* Less than 4 * VEC and aligned to VEC_SIZE.  */
> -	addl	$(VEC_SIZE * 2), %edx
> -	jle	L(last_2x_vec)
> -
> -	VPCMP	$0, (%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> +	/* Check if first VEC contained match.  */
>  	testl	%eax, %eax
> -	jnz	L(first_vec_x0)
> +	jnz	L(first_vec_x1_check)
>  
> -	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> -	testl	%eax, %eax
> -	jnz	L(first_vec_x1)
> +	/* If remaining length > CHAR_PER_VEC * 2.  */
> +	addl	$(CHAR_PER_VEC * 2), %edx
> +	jg	L(last_4x_vec)
>  
> -	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> -	testl	%eax, %eax
> +L(last_2x_vec):
> +	/* If remaining length < CHAR_PER_VEC.  */
> +	addl	$CHAR_PER_VEC, %edx
> +	jle	L(zero_end)
>  
> -	jnz	L(first_vec_x2_check)
> -	subl	$VEC_SIZE, %edx
> -	jle	L(zero)
> +	/* Check VEC2 and compare any match with remaining length.  */
> +	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
> +	tzcntl	%eax, %eax
> +	cmpl	%eax, %edx
> +	jbe	L(set_zero_end)
> +	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> +L(zero_end):
> +	ret
>  
> -	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> -	testl	%eax, %eax
>  
> -	jnz	L(first_vec_x3_check)
> +	.p2align 4
> +L(first_vec_x1_check):
> +	tzcntl	%eax, %eax
> +	/* Adjust length.  */
> +	subl	$-(CHAR_PER_VEC * 4), %edx
> +	/* Check if match within remaining length.  */
> +	cmpl	%eax, %edx
> +	jbe	L(set_zero_end)
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
> +	ret
> +L(set_zero_end):
>  	xorl	%eax, %eax
>  	ret
>  
>  	.p2align 4
> -L(last_2x_vec):
> -	addl	$(VEC_SIZE * 2), %edx
> -	VPCMP	$0, (%rdi), %YMMMATCH, %k1
> +L(loop_4x_vec_end):
> +# endif
> +	/* rawmemchr will fall through into this if match was found in
> +	   loop.  */
> +
> +	/* k1 has not of matches with VEC1.  */
>  	kmovd	%k1, %eax
> -	testl	%eax, %eax
> +# ifdef USE_AS_WMEMCHR
> +	subl	$((1 << CHAR_PER_VEC) - 1), %eax
> +# else
> +	incl	%eax
> +# endif
> +	jnz	L(last_vec_x1_return)
>  
> -	jnz	L(first_vec_x0_check)
> -	subl	$VEC_SIZE, %edx
> -	jle	L(zero)
> +	VPCMP	$0, %YMM2, %YZERO, %k0
> +	kmovd	%k0, %eax
> +	testl	%eax, %eax
> +	jnz	L(last_vec_x2_return)
>  
> -	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1
> -	kmovd	%k1, %eax
> +	kmovd	%k2, %eax
>  	testl	%eax, %eax
> -	jnz	L(first_vec_x1_check)
> -	xorl	%eax, %eax
> -	ret
> +	jnz	L(last_vec_x3_return)
>  
> -	.p2align 4
> -L(first_vec_x0_check):
> +	kmovd	%k3, %eax
>  	tzcntl	%eax, %eax
> -# ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	sall	$2, %eax
> +# ifdef USE_AS_RAWMEMCHR
> +	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
> +# else
> +	leaq	(VEC_SIZE * 7)(%rdi, %rax, CHAR_SIZE), %rax
>  # endif
> -	/* Check the end of data.  */
> -	cmpq	%rax, %rdx
> -	jbe	L(zero)
> -	addq	%rdi, %rax
>  	ret
>  
>  	.p2align 4
> -L(first_vec_x1_check):
> +L(last_vec_x1_return):
>  	tzcntl	%eax, %eax
> -# ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	sall	$2, %eax
> -# endif
> -	/* Check the end of data.  */
> -	cmpq	%rax, %rdx
> -	jbe	L(zero)
> -	addq	$VEC_SIZE, %rax
> +# ifdef USE_AS_RAWMEMCHR
> +#  ifdef USE_AS_WMEMCHR
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	(%rdi, %rax, CHAR_SIZE), %rax
> +#  else
>  	addq	%rdi, %rax
> -	ret
> -
> -	.p2align 4
> -L(first_vec_x2_check):
> -	tzcntl	%eax, %eax
> -# ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	sall	$2, %eax
> +#  endif
> +# else
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
>  # endif
> -	/* Check the end of data.  */
> -	cmpq	%rax, %rdx
> -	jbe	L(zero)
> -	addq	$(VEC_SIZE * 2), %rax
> -	addq	%rdi, %rax
>  	ret
>  
>  	.p2align 4
> -L(first_vec_x3_check):
> +L(last_vec_x2_return):
>  	tzcntl	%eax, %eax
> -# ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	sall	$2, %eax
> +# ifdef USE_AS_RAWMEMCHR
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
> +# else
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	(VEC_SIZE * 5)(%rdi, %rax, CHAR_SIZE), %rax
>  # endif
> -	/* Check the end of data.  */
> -	cmpq	%rax, %rdx
> -	jbe	L(zero)
> -	addq	$(VEC_SIZE * 3), %rax
> -	addq	%rdi, %rax
>  	ret
>  
>  	.p2align 4
> -L(zero):
> -	xorl	%eax, %eax
> -	ret
> -# endif
> -
> -	.p2align 4
> -L(first_vec_x0):
> +L(last_vec_x3_return):
>  	tzcntl	%eax, %eax
> -# ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	leaq	(%rdi, %rax, 4), %rax
> +# ifdef USE_AS_RAWMEMCHR
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
>  # else
> -	addq	%rdi, %rax
> +	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> +	leaq	(VEC_SIZE * 6)(%rdi, %rax, CHAR_SIZE), %rax
>  # endif
>  	ret
>  
> +
> +# ifndef USE_AS_RAWMEMCHR
> +L(last_4x_vec_or_less_cmpeq):
> +	VPCMP	$0, (VEC_SIZE * 5)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
> +	subq	$-(VEC_SIZE * 4), %rdi
> +	/* Check first VEC regardless.  */
> +	testl	%eax, %eax
> +	jnz	L(first_vec_x1_check)
> +
> +	/* If remaining length <= CHAR_PER_VEC * 2.  */
> +	addl	$(CHAR_PER_VEC * 2), %edx
> +	jle	L(last_2x_vec)
> +
>  	.p2align 4
> -L(first_vec_x1):
> +L(last_4x_vec):
> +	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
> +	testl	%eax, %eax
> +	jnz	L(last_vec_x2)
> +
> +
> +	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
> +	/* Create mask for possible matches within remaining length.  */
> +#  ifdef USE_AS_WMEMCHR
> +	movl	$((1 << (CHAR_PER_VEC * 2)) - 1), %ecx
> +	bzhil	%edx, %ecx, %ecx
> +#  else
> +	movq	$-1, %rcx
> +	bzhiq	%rdx, %rcx, %rcx
> +#  endif
> +	/* Test matches in data against length match.  */
> +	andl	%ecx, %eax
> +	jnz	L(last_vec_x3)
> +
> +	/* if remaining length <= CHAR_PER_VEC * 3 (Note this is after
> +	   remaining length was found to be > CHAR_PER_VEC * 2.  */
> +	subl	$CHAR_PER_VEC, %edx
> +	jbe	L(zero_end2)
> +
> +
> +	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
> +	kmovd	%k0, %eax
> +	/* Shift remaining length mask for last VEC.  */
> +#  ifdef USE_AS_WMEMCHR
> +	shrl	$CHAR_PER_VEC, %ecx
> +#  else
> +	shrq	$CHAR_PER_VEC, %rcx
> +#  endif
> +	andl	%ecx, %eax
> +	jz	L(zero_end2)
>  	tzcntl	%eax, %eax
> -# ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	leaq	VEC_SIZE(%rdi, %rax, 4), %rax
> -# else
> -	addq	$VEC_SIZE, %rax
> -	addq	%rdi, %rax
> -# endif
> +	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
> +L(zero_end2):
>  	ret
>  
> -	.p2align 4
> -L(first_vec_x2):
> +L(last_vec_x2):
>  	tzcntl	%eax, %eax
> -# ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	leaq	(VEC_SIZE * 2)(%rdi, %rax, 4), %rax
> -# else
> -	addq	$(VEC_SIZE * 2), %rax
> -	addq	%rdi, %rax
> -# endif
> +	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
>  	ret
>  
>  	.p2align 4
> -L(4x_vec_end):
> -	kmovd	%k1, %eax
> -	testl	%eax, %eax
> -	jnz	L(first_vec_x0)
> -	kmovd	%k2, %eax
> -	testl	%eax, %eax
> -	jnz	L(first_vec_x1)
> -	kmovd	%k3, %eax
> -	testl	%eax, %eax
> -	jnz	L(first_vec_x2)
> -	kmovd	%k4, %eax
> -	testl	%eax, %eax
> -L(first_vec_x3):
> +L(last_vec_x3):
>  	tzcntl	%eax, %eax
> -# ifdef USE_AS_WMEMCHR
> -	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> -	leaq	(VEC_SIZE * 3)(%rdi, %rax, 4), %rax
> -# else
> -	addq	$(VEC_SIZE * 3), %rax
> -	addq	%rdi, %rax
> -# endif
> +	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
>  	ret
> +# endif
>  
>  END (MEMCHR)
>  #endif
> -- 
> 2.29.2
>

On Mon, May 3, 2021 at 6:26 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Mon, May 03, 2021 at 04:06:55PM -0400, Noah Goldstein wrote:
> > No bug. This commit optimizes memchr-evex.S. The optimizations include
> > replacing some branches with cmovcc, avoiding some branches entirely
> > in the less_4x_vec case, making the page cross logic less strict,
> > saving some ALU in the alignment process, and most importantly
> > increasing ILP in the 4x loop. test-memchr, test-rawmemchr, and
> > test-wmemchr are all passing.
> >
> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > ---
> >  sysdeps/x86_64/multiarch/memchr-evex.S | 547 +++++++++++++++----------
> >  1 file changed, 322 insertions(+), 225 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/memchr-evex.S b/sysdeps/x86_64/multiarch/memchr-evex.S
> > index 6dd5d67b90..147d7aa8ee 100644
> > --- a/sysdeps/x86_64/multiarch/memchr-evex.S
> > +++ b/sysdeps/x86_64/multiarch/memchr-evex.S
> > @@ -26,14 +26,28 @@
> >
> >  # ifdef USE_AS_WMEMCHR
> >  #  define VPBROADCAST        vpbroadcastd
> > -#  define VPCMP              vpcmpd
> > -#  define SHIFT_REG  r8d
> > +#  define VPMINU     vpminud
> > +#  define VPCMP      vpcmpd
> > +#  define VPCMPEQ    vpcmpeqd
> > +#  define CHAR_SIZE  4
> >  # else
> >  #  define VPBROADCAST        vpbroadcastb
> > -#  define VPCMP              vpcmpb
> > -#  define SHIFT_REG  ecx
> > +#  define VPMINU     vpminub
> > +#  define VPCMP      vpcmpb
> > +#  define VPCMPEQ    vpcmpeqb
> > +#  define CHAR_SIZE  1
> >  # endif
> >
> > +# ifdef USE_AS_RAWMEMCHR
> > +#  define RAW_PTR_REG        rcx
> > +#  define ALGN_PTR_REG       rdi
> > +# else
> > +#  define RAW_PTR_REG        rdi
> > +#  define ALGN_PTR_REG       rcx
> > +# endif
> > +
> > +# define XZERO               xmm23
> > +# define YZERO               ymm23
>
> Please rename XZERO/YZERO to XMMZERO/YMMZERO.  OK with this change.

Done and thanks!

>
> Thanks.
>
> >  # define XMMMATCH    xmm16
> >  # define YMMMATCH    ymm16
> >  # define YMM1                ymm17
> > @@ -44,6 +58,8 @@
> >  # define YMM6                ymm22
> >
> >  # define VEC_SIZE 32
> > +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
> > +# define PAGE_SIZE 4096
> >
> >       .section .text.evex,"ax",@progbits
> >  ENTRY (MEMCHR)
> > @@ -51,11 +67,7 @@ ENTRY (MEMCHR)
> >       /* Check for zero length.  */
> >       test    %RDX_LP, %RDX_LP
> >       jz      L(zero)
> > -# endif
> > -     movl    %edi, %ecx
> > -# ifdef USE_AS_WMEMCHR
> > -     shl     $2, %RDX_LP
> > -# else
> > +
> >  #  ifdef __ILP32__
> >       /* Clear the upper 32 bits.  */
> >       movl    %edx, %edx
> > @@ -64,318 +76,403 @@ ENTRY (MEMCHR)
> >       /* Broadcast CHAR to YMMMATCH.  */
> >       VPBROADCAST %esi, %YMMMATCH
> >       /* Check if we may cross page boundary with one vector load.  */
> > -     andl    $(2 * VEC_SIZE - 1), %ecx
> > -     cmpl    $VEC_SIZE, %ecx
> > -     ja      L(cros_page_boundary)
> > +     movl    %edi, %eax
> > +     andl    $(PAGE_SIZE - 1), %eax
> > +     cmpl    $(PAGE_SIZE - VEC_SIZE), %eax
> > +     ja      L(cross_page_boundary)
> >
> >       /* Check the first VEC_SIZE bytes.  */
> > -     VPCMP   $0, (%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > -     testl   %eax, %eax
> > -
> > +     VPCMP   $0, (%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> >  # ifndef USE_AS_RAWMEMCHR
> > -     jnz     L(first_vec_x0_check)
> > -     /* Adjust length and check the end of data.  */
> > -     subq    $VEC_SIZE, %rdx
> > -     jbe     L(zero)
> > +     /* If length < CHAR_PER_VEC handle special.  */
> > +     cmpq    $CHAR_PER_VEC, %rdx
> > +     jbe     L(first_vec_x0)
> > +# endif
> > +     testl   %eax, %eax
> > +     jz      L(aligned_more)
> > +     tzcntl  %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    (%rdi, %rax, CHAR_SIZE), %rax
> >  # else
> > -     jnz     L(first_vec_x0)
> > +     addq    %rdi, %rax
> >  # endif
> > -
> > -     /* Align data for aligned loads in the loop.  */
> > -     addq    $VEC_SIZE, %rdi
> > -     andl    $(VEC_SIZE - 1), %ecx
> > -     andq    $-VEC_SIZE, %rdi
> > +     ret
> >
> >  # ifndef USE_AS_RAWMEMCHR
> > -     /* Adjust length.  */
> > -     addq    %rcx, %rdx
> > -
> > -     subq    $(VEC_SIZE * 4), %rdx
> > -     jbe     L(last_4x_vec_or_less)
> > -# endif
> > -     jmp     L(more_4x_vec)
> > +L(zero):
> > +     xorl    %eax, %eax
> > +     ret
> >
> > +     .p2align 5
> > +L(first_vec_x0):
> > +     /* Check if first match was before length.  */
> > +     tzcntl  %eax, %eax
> > +     xorl    %ecx, %ecx
> > +     cmpl    %eax, %edx
> > +     leaq    (%rdi, %rax, CHAR_SIZE), %rax
> > +     cmovle  %rcx, %rax
> > +     ret
> > +# else
> > +     /* NB: first_vec_x0 is 17 bytes which will leave
> > +        cross_page_boundary (which is relatively cold) close enough
> > +        to ideal alignment. So only realign L(cross_page_boundary) if
> > +        rawmemchr.  */
> >       .p2align 4
> > -L(cros_page_boundary):
> > -     andl    $(VEC_SIZE - 1), %ecx
> > +# endif
> > +L(cross_page_boundary):
> > +     /* Save pointer before aligning as its original value is
> > +        necessary for computer return address if byte is found or
> > +        adjusting length if it is not and this is memchr.  */
> > +     movq    %rdi, %rcx
> > +     /* Align data to VEC_SIZE. ALGN_PTR_REG is rcx for memchr and rdi
> > +        for rawmemchr.  */
> > +     andq    $-VEC_SIZE, %ALGN_PTR_REG
> > +     VPCMP   $0, (%ALGN_PTR_REG), %YMMMATCH, %k0
> > +     kmovd   %k0, %r8d
> >  # ifdef USE_AS_WMEMCHR
> > -     /* NB: Divide shift count by 4 since each bit in K1 represent 4
> > +     /* NB: Divide shift count by 4 since each bit in K0 represent 4
> >          bytes.  */
> > -     movl    %ecx, %SHIFT_REG
> > -     sarl    $2, %SHIFT_REG
> > +     sarl    $2, %eax
> > +# endif
> > +# ifndef USE_AS_RAWMEMCHR
> > +     movl    $(PAGE_SIZE / CHAR_SIZE), %esi
> > +     subl    %eax, %esi
> >  # endif
> > -     andq    $-VEC_SIZE, %rdi
> > -     VPCMP   $0, (%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > -     /* Remove the leading bytes.  */
> > -     sarxl   %SHIFT_REG, %eax, %eax
> > -     testl   %eax, %eax
> > -     jz      L(aligned_more)
> > -     tzcntl  %eax, %eax
> >  # ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     sall    $2, %eax
> > +     andl    $(CHAR_PER_VEC - 1), %eax
> >  # endif
> > +     /* Remove the leading bytes.  */
> > +     sarxl   %eax, %r8d, %eax
> >  # ifndef USE_AS_RAWMEMCHR
> >       /* Check the end of data.  */
> > -     cmpq    %rax, %rdx
> > -     jbe     L(zero)
> > +     cmpq    %rsi, %rdx
> > +     jbe     L(first_vec_x0)
> > +# endif
> > +     testl   %eax, %eax
> > +     jz      L(cross_page_continue)
> > +     tzcntl  %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    (%RAW_PTR_REG, %rax, CHAR_SIZE), %rax
> > +# else
> > +     addq    %RAW_PTR_REG, %rax
> >  # endif
> > -     addq    %rdi, %rax
> > -     addq    %rcx, %rax
> >       ret
> >
> >       .p2align 4
> > -L(aligned_more):
> > -# ifndef USE_AS_RAWMEMCHR
> > -        /* Calculate "rdx + rcx - VEC_SIZE" with "rdx - (VEC_SIZE - rcx)"
> > -        instead of "(rdx + rcx) - VEC_SIZE" to void possible addition
> > -        overflow.  */
> > -     negq    %rcx
> > -     addq    $VEC_SIZE, %rcx
> > +L(first_vec_x1):
> > +     tzcntl  %eax, %eax
> > +     leaq    VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
> > +     ret
> >
> > -     /* Check the end of data.  */
> > -     subq    %rcx, %rdx
> > -     jbe     L(zero)
> > -# endif
> > +     .p2align 4
> > +L(first_vec_x2):
> > +     tzcntl  %eax, %eax
> > +     leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> > +     ret
> >
> > -     addq    $VEC_SIZE, %rdi
> > +     .p2align 4
> > +L(first_vec_x3):
> > +     tzcntl  %eax, %eax
> > +     leaq    (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
> > +     ret
> >
> > -# ifndef USE_AS_RAWMEMCHR
> > -     subq    $(VEC_SIZE * 4), %rdx
> > -     jbe     L(last_4x_vec_or_less)
> > -# endif
> > +     .p2align 4
> > +L(first_vec_x4):
> > +     tzcntl  %eax, %eax
> > +     leaq    (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
> > +     ret
> >
> > -L(more_4x_vec):
> > +     .p2align 5
> > +L(aligned_more):
> >       /* Check the first 4 * VEC_SIZE.  Only one VEC_SIZE at a time
> >          since data is only aligned to VEC_SIZE.  */
> > -     VPCMP   $0, (%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > -     testl   %eax, %eax
> > -     jnz     L(first_vec_x0)
> >
> > -     VPCMP   $0, VEC_SIZE(%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > +# ifndef USE_AS_RAWMEMCHR
> > +     /* Align data to VEC_SIZE.  */
> > +L(cross_page_continue):
> > +     xorl    %ecx, %ecx
> > +     subl    %edi, %ecx
> > +     andq    $-VEC_SIZE, %rdi
> > +     /* esi is for adjusting length to see if near the end.  */
> > +     leal    (VEC_SIZE * 5)(%rdi, %rcx), %esi
> > +#  ifdef USE_AS_WMEMCHR
> > +     /* NB: Divide bytes by 4 to get the wchar_t count.  */
> > +     sarl    $2, %esi
> > +#  endif
> > +# else
> > +     andq    $-VEC_SIZE, %rdi
> > +L(cross_page_continue):
> > +# endif
> > +     /* Load first VEC regardless.  */
> > +     VPCMP   $0, (VEC_SIZE)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> > +# ifndef USE_AS_RAWMEMCHR
> > +     /* Adjust length. If near end handle specially.  */
> > +     subq    %rsi, %rdx
> > +     jbe     L(last_4x_vec_or_less)
> > +# endif
> >       testl   %eax, %eax
> >       jnz     L(first_vec_x1)
> >
> > -     VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > +     VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> >       testl   %eax, %eax
> >       jnz     L(first_vec_x2)
> >
> > -     VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > +     VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> >       testl   %eax, %eax
> >       jnz     L(first_vec_x3)
> >
> > -     addq    $(VEC_SIZE * 4), %rdi
> > +     VPCMP   $0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> > +     testl   %eax, %eax
> > +     jnz     L(first_vec_x4)
> > +
> >
> >  # ifndef USE_AS_RAWMEMCHR
> > -     subq    $(VEC_SIZE * 4), %rdx
> > -     jbe     L(last_4x_vec_or_less)
> > -# endif
> > +     /* Check if at last CHAR_PER_VEC * 4 length.  */
> > +     subq    $(CHAR_PER_VEC * 4), %rdx
> > +     jbe     L(last_4x_vec_or_less_cmpeq)
> > +     addq    $VEC_SIZE, %rdi
> >
> > -     /* Align data to 4 * VEC_SIZE.  */
> > -     movq    %rdi, %rcx
> > -     andl    $(4 * VEC_SIZE - 1), %ecx
> > +     /* Align data to VEC_SIZE * 4 for the loop and readjust length.
> > +      */
> > +#  ifdef USE_AS_WMEMCHR
> > +     movl    %edi, %ecx
> >       andq    $-(4 * VEC_SIZE), %rdi
> > -
> > -# ifndef USE_AS_RAWMEMCHR
> > -     /* Adjust length.  */
> > +     andl    $(VEC_SIZE * 4 - 1), %ecx
> > +     /* NB: Divide bytes by 4 to get the wchar_t count.  */
> > +     sarl    $2, %ecx
> >       addq    %rcx, %rdx
> > +#  else
> > +     addq    %rdi, %rdx
> > +     andq    $-(4 * VEC_SIZE), %rdi
> > +     subq    %rdi, %rdx
> > +#  endif
> > +# else
> > +     addq    $VEC_SIZE, %rdi
> > +     andq    $-(4 * VEC_SIZE), %rdi
> >  # endif
> >
> > +     vpxorq  %XZERO, %XZERO, %XZERO
> > +
> > +     /* Compare 4 * VEC at a time forward.  */
> >       .p2align 4
> >  L(loop_4x_vec):
> > -     /* Compare 4 * VEC at a time forward.  */
> > -     VPCMP   $0, (%rdi), %YMMMATCH, %k1
> > -     VPCMP   $0, VEC_SIZE(%rdi), %YMMMATCH, %k2
> > -     kord    %k1, %k2, %k5
> > -     VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k3
> > -     VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k4
> > -
> > -     kord    %k3, %k4, %k6
> > -     kortestd %k5, %k6
> > -     jnz     L(4x_vec_end)
> > -
> > -     addq    $(VEC_SIZE * 4), %rdi
> > -
> > +     /* It would be possible to save some instructions using 4x VPCMP
> > +        but bottleneck on port 5 makes it not woth it.  */
> > +     VPCMP   $4, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k1
> > +     /* xor will set bytes match esi to zero.  */
> > +     vpxorq  (VEC_SIZE * 5)(%rdi), %YMMMATCH, %YMM2
> > +     vpxorq  (VEC_SIZE * 6)(%rdi), %YMMMATCH, %YMM3
> > +     VPCMP   $0, (VEC_SIZE * 7)(%rdi), %YMMMATCH, %k3
> > +     /* Reduce VEC2 / VEC3 with min and VEC1 with zero mask.  */
> > +     VPMINU  %YMM2, %YMM3, %YMM3 {%k1} {z}
> > +     VPCMP   $0, %YMM3, %YZERO, %k2
> >  # ifdef USE_AS_RAWMEMCHR
> > -     jmp     L(loop_4x_vec)
> > +     subq    $-(VEC_SIZE * 4), %rdi
> > +     kortestd %k2, %k3
> > +     jz      L(loop_4x_vec)
> >  # else
> > -     subq    $(VEC_SIZE * 4), %rdx
> > +     kortestd %k2, %k3
> > +     jnz     L(loop_4x_vec_end)
> > +
> > +     subq    $-(VEC_SIZE * 4), %rdi
> > +
> > +     subq    $(CHAR_PER_VEC * 4), %rdx
> >       ja      L(loop_4x_vec)
> >
> > +     /* Fall through into less than 4 remaining vectors of length case.
> > +      */
> > +     VPCMP   $0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> > +     addq    $(VEC_SIZE * 3), %rdi
> > +     .p2align 4
> >  L(last_4x_vec_or_less):
> > -     /* Less than 4 * VEC and aligned to VEC_SIZE.  */
> > -     addl    $(VEC_SIZE * 2), %edx
> > -     jle     L(last_2x_vec)
> > -
> > -     VPCMP   $0, (%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > +     /* Check if first VEC contained match.  */
> >       testl   %eax, %eax
> > -     jnz     L(first_vec_x0)
> > +     jnz     L(first_vec_x1_check)
> >
> > -     VPCMP   $0, VEC_SIZE(%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > -     testl   %eax, %eax
> > -     jnz     L(first_vec_x1)
> > +     /* If remaining length > CHAR_PER_VEC * 2.  */
> > +     addl    $(CHAR_PER_VEC * 2), %edx
> > +     jg      L(last_4x_vec)
> >
> > -     VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > -     testl   %eax, %eax
> > +L(last_2x_vec):
> > +     /* If remaining length < CHAR_PER_VEC.  */
> > +     addl    $CHAR_PER_VEC, %edx
> > +     jle     L(zero_end)
> >
> > -     jnz     L(first_vec_x2_check)
> > -     subl    $VEC_SIZE, %edx
> > -     jle     L(zero)
> > +     /* Check VEC2 and compare any match with remaining length.  */
> > +     VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> > +     tzcntl  %eax, %eax
> > +     cmpl    %eax, %edx
> > +     jbe     L(set_zero_end)
> > +     leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> > +L(zero_end):
> > +     ret
> >
> > -     VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > -     testl   %eax, %eax
> >
> > -     jnz     L(first_vec_x3_check)
> > +     .p2align 4
> > +L(first_vec_x1_check):
> > +     tzcntl  %eax, %eax
> > +     /* Adjust length.  */
> > +     subl    $-(CHAR_PER_VEC * 4), %edx
> > +     /* Check if match within remaining length.  */
> > +     cmpl    %eax, %edx
> > +     jbe     L(set_zero_end)
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
> > +     ret
> > +L(set_zero_end):
> >       xorl    %eax, %eax
> >       ret
> >
> >       .p2align 4
> > -L(last_2x_vec):
> > -     addl    $(VEC_SIZE * 2), %edx
> > -     VPCMP   $0, (%rdi), %YMMMATCH, %k1
> > +L(loop_4x_vec_end):
> > +# endif
> > +     /* rawmemchr will fall through into this if match was found in
> > +        loop.  */
> > +
> > +     /* k1 has not of matches with VEC1.  */
> >       kmovd   %k1, %eax
> > -     testl   %eax, %eax
> > +# ifdef USE_AS_WMEMCHR
> > +     subl    $((1 << CHAR_PER_VEC) - 1), %eax
> > +# else
> > +     incl    %eax
> > +# endif
> > +     jnz     L(last_vec_x1_return)
> >
> > -     jnz     L(first_vec_x0_check)
> > -     subl    $VEC_SIZE, %edx
> > -     jle     L(zero)
> > +     VPCMP   $0, %YMM2, %YZERO, %k0
> > +     kmovd   %k0, %eax
> > +     testl   %eax, %eax
> > +     jnz     L(last_vec_x2_return)
> >
> > -     VPCMP   $0, VEC_SIZE(%rdi), %YMMMATCH, %k1
> > -     kmovd   %k1, %eax
> > +     kmovd   %k2, %eax
> >       testl   %eax, %eax
> > -     jnz     L(first_vec_x1_check)
> > -     xorl    %eax, %eax
> > -     ret
> > +     jnz     L(last_vec_x3_return)
> >
> > -     .p2align 4
> > -L(first_vec_x0_check):
> > +     kmovd   %k3, %eax
> >       tzcntl  %eax, %eax
> > -# ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     sall    $2, %eax
> > +# ifdef USE_AS_RAWMEMCHR
> > +     leaq    (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
> > +# else
> > +     leaq    (VEC_SIZE * 7)(%rdi, %rax, CHAR_SIZE), %rax
> >  # endif
> > -     /* Check the end of data.  */
> > -     cmpq    %rax, %rdx
> > -     jbe     L(zero)
> > -     addq    %rdi, %rax
> >       ret
> >
> >       .p2align 4
> > -L(first_vec_x1_check):
> > +L(last_vec_x1_return):
> >       tzcntl  %eax, %eax
> > -# ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     sall    $2, %eax
> > -# endif
> > -     /* Check the end of data.  */
> > -     cmpq    %rax, %rdx
> > -     jbe     L(zero)
> > -     addq    $VEC_SIZE, %rax
> > +# ifdef USE_AS_RAWMEMCHR
> > +#  ifdef USE_AS_WMEMCHR
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    (%rdi, %rax, CHAR_SIZE), %rax
> > +#  else
> >       addq    %rdi, %rax
> > -     ret
> > -
> > -     .p2align 4
> > -L(first_vec_x2_check):
> > -     tzcntl  %eax, %eax
> > -# ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     sall    $2, %eax
> > +#  endif
> > +# else
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
> >  # endif
> > -     /* Check the end of data.  */
> > -     cmpq    %rax, %rdx
> > -     jbe     L(zero)
> > -     addq    $(VEC_SIZE * 2), %rax
> > -     addq    %rdi, %rax
> >       ret
> >
> >       .p2align 4
> > -L(first_vec_x3_check):
> > +L(last_vec_x2_return):
> >       tzcntl  %eax, %eax
> > -# ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     sall    $2, %eax
> > +# ifdef USE_AS_RAWMEMCHR
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax
> > +# else
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    (VEC_SIZE * 5)(%rdi, %rax, CHAR_SIZE), %rax
> >  # endif
> > -     /* Check the end of data.  */
> > -     cmpq    %rax, %rdx
> > -     jbe     L(zero)
> > -     addq    $(VEC_SIZE * 3), %rax
> > -     addq    %rdi, %rax
> >       ret
> >
> >       .p2align 4
> > -L(zero):
> > -     xorl    %eax, %eax
> > -     ret
> > -# endif
> > -
> > -     .p2align 4
> > -L(first_vec_x0):
> > +L(last_vec_x3_return):
> >       tzcntl  %eax, %eax
> > -# ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (%rdi, %rax, 4), %rax
> > +# ifdef USE_AS_RAWMEMCHR
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> >  # else
> > -     addq    %rdi, %rax
> > +     /* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */
> > +     leaq    (VEC_SIZE * 6)(%rdi, %rax, CHAR_SIZE), %rax
> >  # endif
> >       ret
> >
> > +
> > +# ifndef USE_AS_RAWMEMCHR
> > +L(last_4x_vec_or_less_cmpeq):
> > +     VPCMP   $0, (VEC_SIZE * 5)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> > +     subq    $-(VEC_SIZE * 4), %rdi
> > +     /* Check first VEC regardless.  */
> > +     testl   %eax, %eax
> > +     jnz     L(first_vec_x1_check)
> > +
> > +     /* If remaining length <= CHAR_PER_VEC * 2.  */
> > +     addl    $(CHAR_PER_VEC * 2), %edx
> > +     jle     L(last_2x_vec)
> > +
> >       .p2align 4
> > -L(first_vec_x1):
> > +L(last_4x_vec):
> > +     VPCMP   $0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> > +     testl   %eax, %eax
> > +     jnz     L(last_vec_x2)
> > +
> > +
> > +     VPCMP   $0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> > +     /* Create mask for possible matches within remaining length.  */
> > +#  ifdef USE_AS_WMEMCHR
> > +     movl    $((1 << (CHAR_PER_VEC * 2)) - 1), %ecx
> > +     bzhil   %edx, %ecx, %ecx
> > +#  else
> > +     movq    $-1, %rcx
> > +     bzhiq   %rdx, %rcx, %rcx
> > +#  endif
> > +     /* Test matches in data against length match.  */
> > +     andl    %ecx, %eax
> > +     jnz     L(last_vec_x3)
> > +
> > +     /* if remaining length <= CHAR_PER_VEC * 3 (Note this is after
> > +        remaining length was found to be > CHAR_PER_VEC * 2.  */
> > +     subl    $CHAR_PER_VEC, %edx
> > +     jbe     L(zero_end2)
> > +
> > +
> > +     VPCMP   $0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0
> > +     kmovd   %k0, %eax
> > +     /* Shift remaining length mask for last VEC.  */
> > +#  ifdef USE_AS_WMEMCHR
> > +     shrl    $CHAR_PER_VEC, %ecx
> > +#  else
> > +     shrq    $CHAR_PER_VEC, %rcx
> > +#  endif
> > +     andl    %ecx, %eax
> > +     jz      L(zero_end2)
> >       tzcntl  %eax, %eax
> > -# ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    VEC_SIZE(%rdi, %rax, 4), %rax
> > -# else
> > -     addq    $VEC_SIZE, %rax
> > -     addq    %rdi, %rax
> > -# endif
> > +     leaq    (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
> > +L(zero_end2):
> >       ret
> >
> > -     .p2align 4
> > -L(first_vec_x2):
> > +L(last_vec_x2):
> >       tzcntl  %eax, %eax
> > -# ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (VEC_SIZE * 2)(%rdi, %rax, 4), %rax
> > -# else
> > -     addq    $(VEC_SIZE * 2), %rax
> > -     addq    %rdi, %rax
> > -# endif
> > +     leaq    (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> >       ret
> >
> >       .p2align 4
> > -L(4x_vec_end):
> > -     kmovd   %k1, %eax
> > -     testl   %eax, %eax
> > -     jnz     L(first_vec_x0)
> > -     kmovd   %k2, %eax
> > -     testl   %eax, %eax
> > -     jnz     L(first_vec_x1)
> > -     kmovd   %k3, %eax
> > -     testl   %eax, %eax
> > -     jnz     L(first_vec_x2)
> > -     kmovd   %k4, %eax
> > -     testl   %eax, %eax
> > -L(first_vec_x3):
> > +L(last_vec_x3):
> >       tzcntl  %eax, %eax
> > -# ifdef USE_AS_WMEMCHR
> > -     /* NB: Multiply wchar_t count by 4 to get the number of bytes.  */
> > -     leaq    (VEC_SIZE * 3)(%rdi, %rax, 4), %rax
> > -# else
> > -     addq    $(VEC_SIZE * 3), %rax
> > -     addq    %rdi, %rax
> > -# endif
> > +     leaq    (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
> >       ret
> > +# endif
> >
> >  END (MEMCHR)
> >  #endif
> > --
> > 2.29.2
> >