| Message ID | 20210517184406.2609574-2-goldstein.w.n@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v1,1/3] x86: Expand bench-memcmp.c and test-memcmp.c | expand |
On Mon, May 17, 2021 at 02:44:07PM -0400, Noah Goldstein wrote: > No bug. This commit optimizes memcmp-avx2.S. The optimizations include > adding a new vec compare path for small sizes, reorganizing the entry > control flow, and removing some unnecissary ALU instructions from the > main loop. test-memcmp and test-wmemcmp are both passing. > > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com> > --- > sysdeps/x86_64/multiarch/ifunc-memcmp.h | 1 + > sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S | 676 +++++++++++-------- > 2 files changed, 396 insertions(+), 281 deletions(-) > > diff --git a/sysdeps/x86_64/multiarch/ifunc-memcmp.h b/sysdeps/x86_64/multiarch/ifunc-memcmp.h > index 8bee1aff75..89e2129968 100644 > --- a/sysdeps/x86_64/multiarch/ifunc-memcmp.h > +++ b/sysdeps/x86_64/multiarch/ifunc-memcmp.h > @@ -33,6 +33,7 @@ IFUNC_SELECTOR (void) > > if (CPU_FEATURE_USABLE_P (cpu_features, AVX2) > && CPU_FEATURE_USABLE_P (cpu_features, MOVBE) > + && CPU_FEATURE_USABLE_P (cpu_features, BMI2) Please also update ifunc-impl-list.c to requre BMI2 for AVX2/EVEX memcmp. > && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load)) > { > if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL) > diff --git a/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S b/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S > index ad0fa962a1..2621ec907a 100644 > --- a/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S > +++ b/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S > @@ -19,17 +19,23 @@ > #if IS_IN (libc) > > /* memcmp/wmemcmp is implemented as: > - 1. For size from 2 to 7 bytes, load as big endian with movbe and bswap > - to avoid branches. > - 2. Use overlapping compare to avoid branch. > - 3. Use vector compare when size >= 4 bytes for memcmp or size >= 8 > - bytes for wmemcmp. > - 4. If size is 8 * VEC_SIZE or less, unroll the loop. > - 5. Compare 4 * VEC_SIZE at a time with the aligned first memory > + 1. Use ymm vector compares when possible. The only case where > + vector compares is not possible for when size < VEC_SIZE > + and loading from either s1 or s2 would cause a page cross. > + 2. For size from 2 to 7 bytes on page cross, load as big endian > + with movbe and bswap to avoid branches. > + 3. Use xmm vector compare when size >= 4 bytes for memcmp or > + size >= 8 bytes for wmemcmp. > + 4. Optimistically compare up to first 4 * VEC_SIZE one at a > + to check for early mismatches. Only do this if its guranteed the > + work is not wasted. > + 5. If size is 8 * VEC_SIZE or less, unroll the loop. > + 6. Compare 4 * VEC_SIZE at a time with the aligned first memory > area. > - 6. Use 2 vector compares when size is 2 * VEC_SIZE or less. > - 7. Use 4 vector compares when size is 4 * VEC_SIZE or less. > - 8. Use 8 vector compares when size is 8 * VEC_SIZE or less. */ > + 7. Use 2 vector compares when size is 2 * VEC_SIZE or less. > + 8. Use 4 vector compares when size is 4 * VEC_SIZE or less. > + 9. Use 8 vector compares when size is 8 * VEC_SIZE or less. */ > + > > # include <sysdep.h> > > @@ -38,8 +44,10 @@ > # endif > > # ifdef USE_AS_WMEMCMP > +# define CHAR_SIZE 4 > # define VPCMPEQ vpcmpeqd > # else > +# define CHAR_SIZE 1 > # define VPCMPEQ vpcmpeqb > # endif > > @@ -52,7 +60,7 @@ > # endif > > # define VEC_SIZE 32 > -# define VEC_MASK ((1 << VEC_SIZE) - 1) > +# define PAGE_SIZE 4096 > > /* Warning! > wmemcmp has to use SIGNED comparison for elements. > @@ -71,136 +79,359 @@ ENTRY (MEMCMP) > jb L(less_vec) > > /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */ > - vmovdqu (%rsi), %ymm2 > - VPCMPEQ (%rdi), %ymm2, %ymm2 > - vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > + vmovdqu (%rsi), %ymm1 > + VPCMPEQ (%rdi), %ymm1, %ymm1 > + vpmovmskb %ymm1, %eax > + /* NB: eax must be destination register if going to > + L(return_vec_[0,2]). For L(return_vec_3 destination register > + must be ecx. */ > + incl %eax > + jnz L(return_vec_0) > > cmpq $(VEC_SIZE * 2), %rdx > - jbe L(last_vec) > - > - VPCMPEQ %ymm0, %ymm0, %ymm0 > - /* More than 2 * VEC. */ > - cmpq $(VEC_SIZE * 8), %rdx > - ja L(more_8x_vec) > - cmpq $(VEC_SIZE * 4), %rdx > - jb L(last_4x_vec) > - > - /* From 4 * VEC to 8 * VEC, inclusively. */ > - vmovdqu (%rsi), %ymm1 > - VPCMPEQ (%rdi), %ymm1, %ymm1 > + jbe L(last_1x_vec) > > + /* Check second VEC no matter what. */ > vmovdqu VEC_SIZE(%rsi), %ymm2 > - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > + VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > + vpmovmskb %ymm2, %eax > + /* If all 4 VEC where equal eax will be all 1s so incl will > + overflow and set zero flag. */ > + incl %eax > + jnz L(return_vec_1) > > - vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 > - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > + /* Less than 4 * VEC. */ > + cmpq $(VEC_SIZE * 4), %rdx > + jbe L(last_2x_vec) > > + /* Check third and fourth VEC no matter what. */ > + vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 > + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > + vpmovmskb %ymm3, %eax > + incl %eax > + jnz L(return_vec_2) > vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 > - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > + vpmovmskb %ymm4, %ecx > + incl %ecx > + jnz L(return_vec_3) > > - vpand %ymm1, %ymm2, %ymm5 > - vpand %ymm3, %ymm4, %ymm6 > - vpand %ymm5, %ymm6, %ymm5 > + /* Go to 4x VEC loop. */ > + cmpq $(VEC_SIZE * 8), %rdx > + ja L(more_8x_vec) > > - vptest %ymm0, %ymm5 > - jnc L(4x_vec_end) > + /* Handle remainder of size = 4 * VEC + 1 to 8 * VEC without any > + branches. */ > > + /* Load first two VEC from s2 before adjusting addresses. */ > + vmovdqu -(VEC_SIZE * 4)(%rsi, %rdx), %ymm1 > + vmovdqu -(VEC_SIZE * 3)(%rsi, %rdx), %ymm2 > leaq -(4 * VEC_SIZE)(%rdi, %rdx), %rdi > leaq -(4 * VEC_SIZE)(%rsi, %rdx), %rsi > - vmovdqu (%rsi), %ymm1 > - VPCMPEQ (%rdi), %ymm1, %ymm1 > > - vmovdqu VEC_SIZE(%rsi), %ymm2 > - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > - vpand %ymm2, %ymm1, %ymm5 > + /* Wait to load from s1 until addressed adjust due to > + unlamination of microfusion with complex address mode. */ > + VPCMPEQ (%rdi), %ymm1, %ymm1 > + VPCMPEQ (VEC_SIZE)(%rdi), %ymm2, %ymm2 > > vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 > - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > - vpand %ymm3, %ymm5, %ymm5 > - > + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 > - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > - vpand %ymm4, %ymm5, %ymm5 > + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > > - vptest %ymm0, %ymm5 > - jnc L(4x_vec_end) > - xorl %eax, %eax > + /* Reduce VEC0 - VEC4. */ > + vpand %ymm1, %ymm2, %ymm5 > + vpand %ymm3, %ymm4, %ymm6 > + vpand %ymm5, %ymm6, %ymm7 > + vpmovmskb %ymm7, %ecx > + incl %ecx > + jnz L(return_vec_0_1_2_3) > + /* NB: eax must be zero to reach here. */ > + VZEROUPPER_RETURN > + > + .p2align 4 > +L(return_vec_0): > + tzcntl %eax, %eax > +# ifdef USE_AS_WMEMCMP > + movl (%rdi, %rax), %ecx > + xorl %edx, %edx > + cmpl (%rsi, %rax), %ecx > + /* NB: no partial register stall here because xorl zero idiom > + above. */ > + setg %dl > + leal -1(%rdx, %rdx), %eax > +# else > + movzbl (%rsi, %rax), %ecx > + movzbl (%rdi, %rax), %eax > + subl %ecx, %eax > +# endif > L(return_vzeroupper): > ZERO_UPPER_VEC_REGISTERS_RETURN > > .p2align 4 > -L(last_2x_vec): > - /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */ > - vmovdqu (%rsi), %ymm2 > - VPCMPEQ (%rdi), %ymm2, %ymm2 > - vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > +L(return_vec_1): > + tzcntl %eax, %eax > +# ifdef USE_AS_WMEMCMP > + movl VEC_SIZE(%rdi, %rax), %ecx > + xorl %edx, %edx > + cmpl VEC_SIZE(%rsi, %rax), %ecx > + setg %dl > + leal -1(%rdx, %rdx), %eax > +# else > + movzbl VEC_SIZE(%rsi, %rax), %ecx > + movzbl VEC_SIZE(%rdi, %rax), %eax > + subl %ecx, %eax > +# endif > + VZEROUPPER_RETURN > + > + .p2align 4 > +L(return_vec_2): > + tzcntl %eax, %eax > +# ifdef USE_AS_WMEMCMP > + movl (VEC_SIZE * 2)(%rdi, %rax), %ecx > + xorl %edx, %edx > + cmpl (VEC_SIZE * 2)(%rsi, %rax), %ecx > + setg %dl > + leal -1(%rdx, %rdx), %eax > +# else > + movzbl (VEC_SIZE * 2)(%rsi, %rax), %ecx > + movzbl (VEC_SIZE * 2)(%rdi, %rax), %eax > + subl %ecx, %eax > +# endif > + VZEROUPPER_RETURN > + > + /* NB: p2align 5 here to ensure 4x loop is 32 byte aligned. */ > + .p2align 5 > +L(8x_return_vec_0_1_2_3): > + /* Returning from L(more_8x_vec) requires restoring rsi. */ > + addq %rdi, %rsi > +L(return_vec_0_1_2_3): > + vpmovmskb %ymm1, %eax > + incl %eax > + jnz L(return_vec_0) > > -L(last_vec): > - /* Use overlapping loads to avoid branches. */ > - leaq -VEC_SIZE(%rdi, %rdx), %rdi > - leaq -VEC_SIZE(%rsi, %rdx), %rsi > - vmovdqu (%rsi), %ymm2 > - VPCMPEQ (%rdi), %ymm2, %ymm2 > vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > + incl %eax > + jnz L(return_vec_1) > + > + vpmovmskb %ymm3, %eax > + incl %eax > + jnz L(return_vec_2) > +L(return_vec_3): > + tzcntl %ecx, %ecx > +# ifdef USE_AS_WMEMCMP > + movl (VEC_SIZE * 3)(%rdi, %rcx), %eax > + xorl %edx, %edx > + cmpl (VEC_SIZE * 3)(%rsi, %rcx), %eax > + setg %dl > + leal -1(%rdx, %rdx), %eax > +# else > + movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax > + movzbl (VEC_SIZE * 3)(%rsi, %rcx), %ecx > + subl %ecx, %eax > +# endif > + VZEROUPPER_RETURN > + > + .p2align 4 > +L(more_8x_vec): > + /* Set end of s1 in rdx. */ > + leaq -(VEC_SIZE * 4)(%rdi, %rdx), %rdx > + /* rsi stores s2 - s1. This allows loop to only update one > + pointer. */ > + subq %rdi, %rsi > + /* Align s1 pointer. */ > + andq $-VEC_SIZE, %rdi > + /* Adjust because first 4x vec where check already. */ > + subq $-(VEC_SIZE * 4), %rdi > + .p2align 4 > +L(loop_4x_vec): > + /* rsi has s2 - s1 so get correct address by adding s1 (in rdi). > + */ > + vmovdqu (%rsi, %rdi), %ymm1 > + VPCMPEQ (%rdi), %ymm1, %ymm1 > + > + vmovdqu VEC_SIZE(%rsi, %rdi), %ymm2 > + VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > + > + vmovdqu (VEC_SIZE * 2)(%rsi, %rdi), %ymm3 > + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > + > + vmovdqu (VEC_SIZE * 3)(%rsi, %rdi), %ymm4 > + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > + > + vpand %ymm1, %ymm2, %ymm5 > + vpand %ymm3, %ymm4, %ymm6 > + vpand %ymm5, %ymm6, %ymm7 > + vpmovmskb %ymm7, %ecx > + incl %ecx > + jnz L(8x_return_vec_0_1_2_3) > + subq $-(VEC_SIZE * 4), %rdi > + /* Check if s1 pointer at end. */ > + cmpq %rdx, %rdi > + jb L(loop_4x_vec) > + > + subq %rdx, %rdi > + /* rdi has 4 * VEC_SIZE - remaining length. */ > + cmpl $(VEC_SIZE * 3), %edi > + jae L(8x_last_1x_vec) > + /* Load regardless of branch. */ > + vmovdqu (VEC_SIZE * 2)(%rsi, %rdx), %ymm3 > + cmpl $(VEC_SIZE * 2), %edi > + jae L(8x_last_2x_vec) > + > + /* Check last 4 VEC. */ > + vmovdqu (%rsi, %rdx), %ymm1 > + VPCMPEQ (%rdx), %ymm1, %ymm1 > + > + vmovdqu VEC_SIZE(%rsi, %rdx), %ymm2 > + VPCMPEQ VEC_SIZE(%rdx), %ymm2, %ymm2 > + > + VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm3, %ymm3 > + > + vmovdqu (VEC_SIZE * 3)(%rsi, %rdx), %ymm4 > + VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm4, %ymm4 > + > + vpand %ymm1, %ymm2, %ymm5 > + vpand %ymm3, %ymm4, %ymm6 > + vpand %ymm5, %ymm6, %ymm7 > + vpmovmskb %ymm7, %ecx > + /* Restore s1 pointer to rdi. */ > + movq %rdx, %rdi > + incl %ecx > + jnz L(8x_return_vec_0_1_2_3) > + /* NB: eax must be zero to reach here. */ > + VZEROUPPER_RETURN > + > + /* Only entry is from L(more_8x_vec). */ > + .p2align 4 > +L(8x_last_2x_vec): > + /* Check second to last VEC. rdx store end pointer of s1 and > + ymm3 has already been loaded with second to last VEC from s2. > + */ > + VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm3, %ymm3 > + vpmovmskb %ymm3, %eax > + incl %eax > + jnz L(8x_return_vec_2) > + /* Check last VEC. */ > + .p2align 4 > +L(8x_last_1x_vec): > + vmovdqu (VEC_SIZE * 3)(%rsi, %rdx), %ymm4 > + VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm4, %ymm4 > + vpmovmskb %ymm4, %eax > + incl %eax > + jnz L(8x_return_vec_3) > VZEROUPPER_RETURN > > .p2align 4 > -L(first_vec): > - /* A byte or int32 is different within 16 or 32 bytes. */ > - tzcntl %eax, %ecx > +L(last_2x_vec): > + /* Check second to last VEC. */ > + vmovdqu -(VEC_SIZE * 2)(%rsi, %rdx), %ymm1 > + VPCMPEQ -(VEC_SIZE * 2)(%rdi, %rdx), %ymm1, %ymm1 > + vpmovmskb %ymm1, %eax > + incl %eax > + jnz L(return_vec_1_end) > + /* Check last VEC. */ > +L(last_1x_vec): > + vmovdqu -(VEC_SIZE * 1)(%rsi, %rdx), %ymm1 > + VPCMPEQ -(VEC_SIZE * 1)(%rdi, %rdx), %ymm1, %ymm1 > + vpmovmskb %ymm1, %eax > + incl %eax > + jnz L(return_vec_0_end) > + VZEROUPPER_RETURN > + > + .p2align 4 > +L(8x_return_vec_2): > + subq $VEC_SIZE, %rdx > +L(8x_return_vec_3): > + tzcntl %eax, %eax > + addq %rdx, %rax > # ifdef USE_AS_WMEMCMP > - xorl %eax, %eax > - movl (%rdi, %rcx), %edx > - cmpl (%rsi, %rcx), %edx > -L(wmemcmp_return): > - setl %al > - negl %eax > - orl $1, %eax > + movl (VEC_SIZE * 3)(%rax), %ecx > + xorl %edx, %edx > + cmpl (VEC_SIZE * 3)(%rsi, %rax), %ecx > + setg %dl > + leal -1(%rdx, %rdx), %eax > # else > - movzbl (%rdi, %rcx), %eax > - movzbl (%rsi, %rcx), %edx > - sub %edx, %eax > + movzbl (VEC_SIZE * 3)(%rsi, %rax), %ecx > + movzbl (VEC_SIZE * 3)(%rax), %eax > + subl %ecx, %eax > # endif > VZEROUPPER_RETURN > > -# ifdef USE_AS_WMEMCMP > .p2align 4 > -L(4): > - xorl %eax, %eax > - movl (%rdi), %edx > - cmpl (%rsi), %edx > - jne L(wmemcmp_return) > - ret > +L(return_vec_1_end): > + tzcntl %eax, %eax > + addl %edx, %eax > +# ifdef USE_AS_WMEMCMP > + movl -(VEC_SIZE * 2)(%rdi, %rax), %ecx > + xorl %edx, %edx > + cmpl -(VEC_SIZE * 2)(%rsi, %rax), %ecx > + setg %dl > + leal -1(%rdx, %rdx), %eax > # else > + movzbl -(VEC_SIZE * 2)(%rsi, %rax), %ecx > + movzbl -(VEC_SIZE * 2)(%rdi, %rax), %eax > + subl %ecx, %eax > +# endif > + VZEROUPPER_RETURN > + > .p2align 4 > -L(between_4_7): > - /* Load as big endian with overlapping movbe to avoid branches. */ > - movbe (%rdi), %eax > - movbe (%rsi), %ecx > - shlq $32, %rax > - shlq $32, %rcx > - movbe -4(%rdi, %rdx), %edi > - movbe -4(%rsi, %rdx), %esi > - orq %rdi, %rax > - orq %rsi, %rcx > - subq %rcx, %rax > - je L(exit) > - sbbl %eax, %eax > - orl $1, %eax > - ret > +L(return_vec_0_end): > + tzcntl %eax, %eax > + addl %edx, %eax > +# ifdef USE_AS_WMEMCMP > + movl -VEC_SIZE(%rdi, %rax), %ecx > + xorl %edx, %edx > + cmpl -VEC_SIZE(%rsi, %rax), %ecx > + setg %dl > + leal -1(%rdx, %rdx), %eax > +# else > + movzbl -VEC_SIZE(%rsi, %rax), %ecx > + movzbl -VEC_SIZE(%rdi, %rax), %eax > + subl %ecx, %eax > +# endif > + VZEROUPPER_RETURN > > .p2align 4 > -L(exit): > - ret > +L(less_vec): > + /* Check if one or less CHAR. This is necessary for size = 0 but > + is also faster for size = CHAR_SIZE. */ > + cmpl $CHAR_SIZE, %edx > + jbe L(one_or_less) > + > + /* Check if loading one VEC from either s1 or s2 could cause a > + page cross. This can have false positives but is by far the > + fastest method. */ > + movl %edi, %eax > + orl %esi, %eax > + andl $(PAGE_SIZE - 1), %eax > + cmpl $(PAGE_SIZE - VEC_SIZE), %eax > + jg L(page_cross_less_vec) > + > + /* No page cross possible. */ > + vmovdqu (%rsi), %ymm2 > + VPCMPEQ (%rdi), %ymm2, %ymm2 > + vpmovmskb %ymm2, %eax > + incl %eax > + /* Result will be zero if s1 and s2 match. Otherwise first set > + bit will be first mismatch. */ > + bzhil %edx, %eax, %edx > + jnz L(return_vec_0) > + xorl %eax, %eax > + VZEROUPPER_RETURN > > .p2align 4 > -L(between_2_3): > +L(page_cross_less_vec): > + /* if USE_AS_WMEMCMP it can only be 0, 4, 8, 12, 16, 20, 24, 28 > + bytes. */ > + cmpl $16, %edx > + jae L(between_16_31) > +# ifndef USE_AS_WMEMCMP > + cmpl $8, %edx > + jae L(between_8_15) > + cmpl $4, %edx > + jae L(between_4_7) > + > /* Load as big endian to avoid branches. */ > movzwl (%rdi), %eax > movzwl (%rsi), %ecx > @@ -208,223 +439,106 @@ L(between_2_3): > shll $8, %ecx > bswap %eax > bswap %ecx > - movb -1(%rdi, %rdx), %al > - movb -1(%rsi, %rdx), %cl > + movzbl -1(%rdi, %rdx), %edi > + movzbl -1(%rsi, %rdx), %esi > + orl %edi, %eax > + orl %esi, %ecx > /* Subtraction is okay because the upper 8 bits are zero. */ > subl %ecx, %eax > + /* No ymm register was touched. */ > ret > > .p2align 4 > -L(1): > - movzbl (%rdi), %eax > +L(one_or_less): > + jb L(zero) > movzbl (%rsi), %ecx > + movzbl (%rdi), %eax > subl %ecx, %eax > - ret > -# endif > - > - .p2align 4 > -L(zero): > - xorl %eax, %eax > + /* No ymm register was touched. */ > ret > > .p2align 4 > -L(less_vec): > -# ifdef USE_AS_WMEMCMP > - /* It can only be 0, 4, 8, 12, 16, 20, 24, 28 bytes. */ > - cmpb $4, %dl > - je L(4) > - jb L(zero) > -# else > - cmpb $1, %dl > - je L(1) > - jb L(zero) > - cmpb $4, %dl > - jb L(between_2_3) > - cmpb $8, %dl > - jb L(between_4_7) > +L(between_8_15): > # endif > - cmpb $16, %dl > - jae L(between_16_31) > - /* It is between 8 and 15 bytes. */ > + /* If USE_AS_WMEMCMP fall through into 8-15 byte case. */ > vmovq (%rdi), %xmm1 > vmovq (%rsi), %xmm2 > - VPCMPEQ %xmm1, %xmm2, %xmm2 > + VPCMPEQ %xmm1, %xmm2, %xmm2 > vpmovmskb %xmm2, %eax > - subl $0xffff, %eax > - jnz L(first_vec) > + subl $0xffff, %eax > + jnz L(return_vec_0) > /* Use overlapping loads to avoid branches. */ > leaq -8(%rdi, %rdx), %rdi > leaq -8(%rsi, %rdx), %rsi > vmovq (%rdi), %xmm1 > vmovq (%rsi), %xmm2 > - VPCMPEQ %xmm1, %xmm2, %xmm2 > + VPCMPEQ %xmm1, %xmm2, %xmm2 > vpmovmskb %xmm2, %eax > - subl $0xffff, %eax > - jnz L(first_vec) > + subl $0xffff, %eax > + jnz L(return_vec_0) > + /* No ymm register was touched. */ > + ret > + > + .p2align 4 > +L(zero): > + xorl %eax, %eax > ret > > .p2align 4 > L(between_16_31): > /* From 16 to 31 bytes. No branch when size == 16. */ > vmovdqu (%rsi), %xmm2 > - VPCMPEQ (%rdi), %xmm2, %xmm2 > + VPCMPEQ (%rdi), %xmm2, %xmm2 > vpmovmskb %xmm2, %eax > - subl $0xffff, %eax > - jnz L(first_vec) > + subl $0xffff, %eax > + jnz L(return_vec_0) > > /* Use overlapping loads to avoid branches. */ > + > + vmovdqu -16(%rsi, %rdx), %xmm2 > leaq -16(%rdi, %rdx), %rdi > leaq -16(%rsi, %rdx), %rsi > - vmovdqu (%rsi), %xmm2 > - VPCMPEQ (%rdi), %xmm2, %xmm2 > + VPCMPEQ (%rdi), %xmm2, %xmm2 > vpmovmskb %xmm2, %eax > - subl $0xffff, %eax > - jnz L(first_vec) > + subl $0xffff, %eax > + jnz L(return_vec_0) > + /* No ymm register was touched. */ > ret > > - .p2align 4 > -L(more_8x_vec): > - /* More than 8 * VEC. Check the first VEC. */ > - vmovdqu (%rsi), %ymm2 > - VPCMPEQ (%rdi), %ymm2, %ymm2 > - vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > - > - /* Align the first memory area for aligned loads in the loop. > - Compute how much the first memory area is misaligned. */ > - movq %rdi, %rcx > - andl $(VEC_SIZE - 1), %ecx > - /* Get the negative of offset for alignment. */ > - subq $VEC_SIZE, %rcx > - /* Adjust the second memory area. */ > - subq %rcx, %rsi > - /* Adjust the first memory area which should be aligned now. */ > - subq %rcx, %rdi > - /* Adjust length. */ > - addq %rcx, %rdx > - > -L(loop_4x_vec): > - /* Compare 4 * VEC at a time forward. */ > - vmovdqu (%rsi), %ymm1 > - VPCMPEQ (%rdi), %ymm1, %ymm1 > - > - vmovdqu VEC_SIZE(%rsi), %ymm2 > - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > - vpand %ymm2, %ymm1, %ymm5 > - > - vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 > - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > - vpand %ymm3, %ymm5, %ymm5 > - > - vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 > - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > - vpand %ymm4, %ymm5, %ymm5 > - > - vptest %ymm0, %ymm5 > - jnc L(4x_vec_end) > - > - addq $(VEC_SIZE * 4), %rdi > - addq $(VEC_SIZE * 4), %rsi > - > - subq $(VEC_SIZE * 4), %rdx > - cmpq $(VEC_SIZE * 4), %rdx > - jae L(loop_4x_vec) > - > - /* Less than 4 * VEC. */ > - cmpq $VEC_SIZE, %rdx > - jbe L(last_vec) > - cmpq $(VEC_SIZE * 2), %rdx > - jbe L(last_2x_vec) > - > -L(last_4x_vec): > - /* From 2 * VEC to 4 * VEC. */ > - vmovdqu (%rsi), %ymm2 > - VPCMPEQ (%rdi), %ymm2, %ymm2 > - vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > - > - addq $VEC_SIZE, %rdi > - addq $VEC_SIZE, %rsi > - vmovdqu (%rsi), %ymm2 > - VPCMPEQ (%rdi), %ymm2, %ymm2 > - vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > - > - /* Use overlapping loads to avoid branches. */ > - leaq -(3 * VEC_SIZE)(%rdi, %rdx), %rdi > - leaq -(3 * VEC_SIZE)(%rsi, %rdx), %rsi > - vmovdqu (%rsi), %ymm2 > - VPCMPEQ (%rdi), %ymm2, %ymm2 > - vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > - > - addq $VEC_SIZE, %rdi > - addq $VEC_SIZE, %rsi > - vmovdqu (%rsi), %ymm2 > - VPCMPEQ (%rdi), %ymm2, %ymm2 > - vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > - VZEROUPPER_RETURN > - > - .p2align 4 > -L(4x_vec_end): > - vpmovmskb %ymm1, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec) > - vpmovmskb %ymm2, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec_x1) > - vpmovmskb %ymm3, %eax > - subl $VEC_MASK, %eax > - jnz L(first_vec_x2) > - vpmovmskb %ymm4, %eax > - subl $VEC_MASK, %eax > - tzcntl %eax, %ecx > # ifdef USE_AS_WMEMCMP > - xorl %eax, %eax > - movl (VEC_SIZE * 3)(%rdi, %rcx), %edx > - cmpl (VEC_SIZE * 3)(%rsi, %rcx), %edx > - jmp L(wmemcmp_return) > -# else > - movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax > - movzbl (VEC_SIZE * 3)(%rsi, %rcx), %edx > - sub %edx, %eax > -# endif > - VZEROUPPER_RETURN > - > .p2align 4 > -L(first_vec_x1): > - tzcntl %eax, %ecx > -# ifdef USE_AS_WMEMCMP > - xorl %eax, %eax > - movl VEC_SIZE(%rdi, %rcx), %edx > - cmpl VEC_SIZE(%rsi, %rcx), %edx > - jmp L(wmemcmp_return) > +L(one_or_less): > + jb L(zero) > + movl (%rdi), %ecx > + xorl %edx, %edx > + cmpl (%rsi), %ecx > + je L(zero) > + setg %dl > + leal -1(%rdx, %rdx), %eax > + /* No ymm register was touched. */ > + ret > # else > - movzbl VEC_SIZE(%rdi, %rcx), %eax > - movzbl VEC_SIZE(%rsi, %rcx), %edx > - sub %edx, %eax > -# endif > - VZEROUPPER_RETURN > > .p2align 4 > -L(first_vec_x2): > - tzcntl %eax, %ecx > -# ifdef USE_AS_WMEMCMP > - xorl %eax, %eax > - movl (VEC_SIZE * 2)(%rdi, %rcx), %edx > - cmpl (VEC_SIZE * 2)(%rsi, %rcx), %edx > - jmp L(wmemcmp_return) > -# else > - movzbl (VEC_SIZE * 2)(%rdi, %rcx), %eax > - movzbl (VEC_SIZE * 2)(%rsi, %rcx), %edx > - sub %edx, %eax > +L(between_4_7): > + /* Load as big endian with overlapping movbe to avoid branches. > + */ > + movbe (%rdi), %eax > + movbe (%rsi), %ecx > + shlq $32, %rax > + shlq $32, %rcx > + movbe -4(%rdi, %rdx), %edi > + movbe -4(%rsi, %rdx), %esi > + orq %rdi, %rax > + orq %rsi, %rcx > + subq %rcx, %rax > + jz L(zero_4_7) > + sbbl %eax, %eax > + orl $1, %eax > +L(zero_4_7): > + /* No ymm register was touched. */ > + ret > # endif > - VZEROUPPER_RETURN > + > END (MEMCMP) > #endif > -- > 2.29.2 > H.J.
On Tue, May 18, 2021 at 9:01 PM H.J. Lu <hjl.tools@gmail.com> wrote: > > On Mon, May 17, 2021 at 02:44:07PM -0400, Noah Goldstein wrote: > > No bug. This commit optimizes memcmp-avx2.S. The optimizations include > > adding a new vec compare path for small sizes, reorganizing the entry > > control flow, and removing some unnecissary ALU instructions from the > > main loop. test-memcmp and test-wmemcmp are both passing. > > > > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com> > > --- > > sysdeps/x86_64/multiarch/ifunc-memcmp.h | 1 + > > sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S | 676 +++++++++++-------- > > 2 files changed, 396 insertions(+), 281 deletions(-) > > > > diff --git a/sysdeps/x86_64/multiarch/ifunc-memcmp.h b/sysdeps/x86_64/multiarch/ifunc-memcmp.h > > index 8bee1aff75..89e2129968 100644 > > --- a/sysdeps/x86_64/multiarch/ifunc-memcmp.h > > +++ b/sysdeps/x86_64/multiarch/ifunc-memcmp.h > > @@ -33,6 +33,7 @@ IFUNC_SELECTOR (void) > > > > if (CPU_FEATURE_USABLE_P (cpu_features, AVX2) > > && CPU_FEATURE_USABLE_P (cpu_features, MOVBE) > > + && CPU_FEATURE_USABLE_P (cpu_features, BMI2) > > Please also update ifunc-impl-list.c to requre BMI2 for AVX2/EVEX > memcmp. Done. > > > && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load)) > > { > > if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL) > > diff --git a/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S b/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S > > index ad0fa962a1..2621ec907a 100644 > > --- a/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S > > +++ b/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S > > @@ -19,17 +19,23 @@ > > #if IS_IN (libc) > > > > /* memcmp/wmemcmp is implemented as: > > - 1. For size from 2 to 7 bytes, load as big endian with movbe and bswap > > - to avoid branches. > > - 2. Use overlapping compare to avoid branch. > > - 3. Use vector compare when size >= 4 bytes for memcmp or size >= 8 > > - bytes for wmemcmp. > > - 4. If size is 8 * VEC_SIZE or less, unroll the loop. > > - 5. Compare 4 * VEC_SIZE at a time with the aligned first memory > > + 1. Use ymm vector compares when possible. The only case where > > + vector compares is not possible for when size < VEC_SIZE > > + and loading from either s1 or s2 would cause a page cross. > > + 2. For size from 2 to 7 bytes on page cross, load as big endian > > + with movbe and bswap to avoid branches. > > + 3. Use xmm vector compare when size >= 4 bytes for memcmp or > > + size >= 8 bytes for wmemcmp. > > + 4. Optimistically compare up to first 4 * VEC_SIZE one at a > > + to check for early mismatches. Only do this if its guranteed the > > + work is not wasted. > > + 5. If size is 8 * VEC_SIZE or less, unroll the loop. > > + 6. Compare 4 * VEC_SIZE at a time with the aligned first memory > > area. > > - 6. Use 2 vector compares when size is 2 * VEC_SIZE or less. > > - 7. Use 4 vector compares when size is 4 * VEC_SIZE or less. > > - 8. Use 8 vector compares when size is 8 * VEC_SIZE or less. */ > > + 7. Use 2 vector compares when size is 2 * VEC_SIZE or less. > > + 8. Use 4 vector compares when size is 4 * VEC_SIZE or less. > > + 9. Use 8 vector compares when size is 8 * VEC_SIZE or less. */ > > + > > > > # include <sysdep.h> > > > > @@ -38,8 +44,10 @@ > > # endif > > > > # ifdef USE_AS_WMEMCMP > > +# define CHAR_SIZE 4 > > # define VPCMPEQ vpcmpeqd > > # else > > +# define CHAR_SIZE 1 > > # define VPCMPEQ vpcmpeqb > > # endif > > > > @@ -52,7 +60,7 @@ > > # endif > > > > # define VEC_SIZE 32 > > -# define VEC_MASK ((1 << VEC_SIZE) - 1) > > +# define PAGE_SIZE 4096 > > > > /* Warning! > > wmemcmp has to use SIGNED comparison for elements. > > @@ -71,136 +79,359 @@ ENTRY (MEMCMP) > > jb L(less_vec) > > > > /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */ > > - vmovdqu (%rsi), %ymm2 > > - VPCMPEQ (%rdi), %ymm2, %ymm2 > > - vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > + vmovdqu (%rsi), %ymm1 > > + VPCMPEQ (%rdi), %ymm1, %ymm1 > > + vpmovmskb %ymm1, %eax > > + /* NB: eax must be destination register if going to > > + L(return_vec_[0,2]). For L(return_vec_3 destination register > > + must be ecx. */ > > + incl %eax > > + jnz L(return_vec_0) > > > > cmpq $(VEC_SIZE * 2), %rdx > > - jbe L(last_vec) > > - > > - VPCMPEQ %ymm0, %ymm0, %ymm0 > > - /* More than 2 * VEC. */ > > - cmpq $(VEC_SIZE * 8), %rdx > > - ja L(more_8x_vec) > > - cmpq $(VEC_SIZE * 4), %rdx > > - jb L(last_4x_vec) > > - > > - /* From 4 * VEC to 8 * VEC, inclusively. */ > > - vmovdqu (%rsi), %ymm1 > > - VPCMPEQ (%rdi), %ymm1, %ymm1 > > + jbe L(last_1x_vec) > > > > + /* Check second VEC no matter what. */ > > vmovdqu VEC_SIZE(%rsi), %ymm2 > > - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > > + VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > > + vpmovmskb %ymm2, %eax > > + /* If all 4 VEC where equal eax will be all 1s so incl will > > + overflow and set zero flag. */ > > + incl %eax > > + jnz L(return_vec_1) > > > > - vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 > > - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > > + /* Less than 4 * VEC. */ > > + cmpq $(VEC_SIZE * 4), %rdx > > + jbe L(last_2x_vec) > > > > + /* Check third and fourth VEC no matter what. */ > > + vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 > > + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > > + vpmovmskb %ymm3, %eax > > + incl %eax > > + jnz L(return_vec_2) > > vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 > > - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > > + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > > + vpmovmskb %ymm4, %ecx > > + incl %ecx > > + jnz L(return_vec_3) > > > > - vpand %ymm1, %ymm2, %ymm5 > > - vpand %ymm3, %ymm4, %ymm6 > > - vpand %ymm5, %ymm6, %ymm5 > > + /* Go to 4x VEC loop. */ > > + cmpq $(VEC_SIZE * 8), %rdx > > + ja L(more_8x_vec) > > > > - vptest %ymm0, %ymm5 > > - jnc L(4x_vec_end) > > + /* Handle remainder of size = 4 * VEC + 1 to 8 * VEC without any > > + branches. */ > > > > + /* Load first two VEC from s2 before adjusting addresses. */ > > + vmovdqu -(VEC_SIZE * 4)(%rsi, %rdx), %ymm1 > > + vmovdqu -(VEC_SIZE * 3)(%rsi, %rdx), %ymm2 > > leaq -(4 * VEC_SIZE)(%rdi, %rdx), %rdi > > leaq -(4 * VEC_SIZE)(%rsi, %rdx), %rsi > > - vmovdqu (%rsi), %ymm1 > > - VPCMPEQ (%rdi), %ymm1, %ymm1 > > > > - vmovdqu VEC_SIZE(%rsi), %ymm2 > > - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > > - vpand %ymm2, %ymm1, %ymm5 > > + /* Wait to load from s1 until addressed adjust due to > > + unlamination of microfusion with complex address mode. */ > > + VPCMPEQ (%rdi), %ymm1, %ymm1 > > + VPCMPEQ (VEC_SIZE)(%rdi), %ymm2, %ymm2 > > > > vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 > > - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > > - vpand %ymm3, %ymm5, %ymm5 > > - > > + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > > vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 > > - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > > - vpand %ymm4, %ymm5, %ymm5 > > + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > > > > - vptest %ymm0, %ymm5 > > - jnc L(4x_vec_end) > > - xorl %eax, %eax > > + /* Reduce VEC0 - VEC4. */ > > + vpand %ymm1, %ymm2, %ymm5 > > + vpand %ymm3, %ymm4, %ymm6 > > + vpand %ymm5, %ymm6, %ymm7 > > + vpmovmskb %ymm7, %ecx > > + incl %ecx > > + jnz L(return_vec_0_1_2_3) > > + /* NB: eax must be zero to reach here. */ > > + VZEROUPPER_RETURN > > + > > + .p2align 4 > > +L(return_vec_0): > > + tzcntl %eax, %eax > > +# ifdef USE_AS_WMEMCMP > > + movl (%rdi, %rax), %ecx > > + xorl %edx, %edx > > + cmpl (%rsi, %rax), %ecx > > + /* NB: no partial register stall here because xorl zero idiom > > + above. */ > > + setg %dl > > + leal -1(%rdx, %rdx), %eax > > +# else > > + movzbl (%rsi, %rax), %ecx > > + movzbl (%rdi, %rax), %eax > > + subl %ecx, %eax > > +# endif > > L(return_vzeroupper): > > ZERO_UPPER_VEC_REGISTERS_RETURN > > > > .p2align 4 > > -L(last_2x_vec): > > - /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */ > > - vmovdqu (%rsi), %ymm2 > > - VPCMPEQ (%rdi), %ymm2, %ymm2 > > - vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > +L(return_vec_1): > > + tzcntl %eax, %eax > > +# ifdef USE_AS_WMEMCMP > > + movl VEC_SIZE(%rdi, %rax), %ecx > > + xorl %edx, %edx > > + cmpl VEC_SIZE(%rsi, %rax), %ecx > > + setg %dl > > + leal -1(%rdx, %rdx), %eax > > +# else > > + movzbl VEC_SIZE(%rsi, %rax), %ecx > > + movzbl VEC_SIZE(%rdi, %rax), %eax > > + subl %ecx, %eax > > +# endif > > + VZEROUPPER_RETURN > > + > > + .p2align 4 > > +L(return_vec_2): > > + tzcntl %eax, %eax > > +# ifdef USE_AS_WMEMCMP > > + movl (VEC_SIZE * 2)(%rdi, %rax), %ecx > > + xorl %edx, %edx > > + cmpl (VEC_SIZE * 2)(%rsi, %rax), %ecx > > + setg %dl > > + leal -1(%rdx, %rdx), %eax > > +# else > > + movzbl (VEC_SIZE * 2)(%rsi, %rax), %ecx > > + movzbl (VEC_SIZE * 2)(%rdi, %rax), %eax > > + subl %ecx, %eax > > +# endif > > + VZEROUPPER_RETURN > > + > > + /* NB: p2align 5 here to ensure 4x loop is 32 byte aligned. */ > > + .p2align 5 > > +L(8x_return_vec_0_1_2_3): > > + /* Returning from L(more_8x_vec) requires restoring rsi. */ > > + addq %rdi, %rsi > > +L(return_vec_0_1_2_3): > > + vpmovmskb %ymm1, %eax > > + incl %eax > > + jnz L(return_vec_0) > > > > -L(last_vec): > > - /* Use overlapping loads to avoid branches. */ > > - leaq -VEC_SIZE(%rdi, %rdx), %rdi > > - leaq -VEC_SIZE(%rsi, %rdx), %rsi > > - vmovdqu (%rsi), %ymm2 > > - VPCMPEQ (%rdi), %ymm2, %ymm2 > > vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > + incl %eax > > + jnz L(return_vec_1) > > + > > + vpmovmskb %ymm3, %eax > > + incl %eax > > + jnz L(return_vec_2) > > +L(return_vec_3): > > + tzcntl %ecx, %ecx > > +# ifdef USE_AS_WMEMCMP > > + movl (VEC_SIZE * 3)(%rdi, %rcx), %eax > > + xorl %edx, %edx > > + cmpl (VEC_SIZE * 3)(%rsi, %rcx), %eax > > + setg %dl > > + leal -1(%rdx, %rdx), %eax > > +# else > > + movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax > > + movzbl (VEC_SIZE * 3)(%rsi, %rcx), %ecx > > + subl %ecx, %eax > > +# endif > > + VZEROUPPER_RETURN > > + > > + .p2align 4 > > +L(more_8x_vec): > > + /* Set end of s1 in rdx. */ > > + leaq -(VEC_SIZE * 4)(%rdi, %rdx), %rdx > > + /* rsi stores s2 - s1. This allows loop to only update one > > + pointer. */ > > + subq %rdi, %rsi > > + /* Align s1 pointer. */ > > + andq $-VEC_SIZE, %rdi > > + /* Adjust because first 4x vec where check already. */ > > + subq $-(VEC_SIZE * 4), %rdi > > + .p2align 4 > > +L(loop_4x_vec): > > + /* rsi has s2 - s1 so get correct address by adding s1 (in rdi). > > + */ > > + vmovdqu (%rsi, %rdi), %ymm1 > > + VPCMPEQ (%rdi), %ymm1, %ymm1 > > + > > + vmovdqu VEC_SIZE(%rsi, %rdi), %ymm2 > > + VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > > + > > + vmovdqu (VEC_SIZE * 2)(%rsi, %rdi), %ymm3 > > + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > > + > > + vmovdqu (VEC_SIZE * 3)(%rsi, %rdi), %ymm4 > > + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > > + > > + vpand %ymm1, %ymm2, %ymm5 > > + vpand %ymm3, %ymm4, %ymm6 > > + vpand %ymm5, %ymm6, %ymm7 > > + vpmovmskb %ymm7, %ecx > > + incl %ecx > > + jnz L(8x_return_vec_0_1_2_3) > > + subq $-(VEC_SIZE * 4), %rdi > > + /* Check if s1 pointer at end. */ > > + cmpq %rdx, %rdi > > + jb L(loop_4x_vec) > > + > > + subq %rdx, %rdi > > + /* rdi has 4 * VEC_SIZE - remaining length. */ > > + cmpl $(VEC_SIZE * 3), %edi > > + jae L(8x_last_1x_vec) > > + /* Load regardless of branch. */ > > + vmovdqu (VEC_SIZE * 2)(%rsi, %rdx), %ymm3 > > + cmpl $(VEC_SIZE * 2), %edi > > + jae L(8x_last_2x_vec) > > + > > + /* Check last 4 VEC. */ > > + vmovdqu (%rsi, %rdx), %ymm1 > > + VPCMPEQ (%rdx), %ymm1, %ymm1 > > + > > + vmovdqu VEC_SIZE(%rsi, %rdx), %ymm2 > > + VPCMPEQ VEC_SIZE(%rdx), %ymm2, %ymm2 > > + > > + VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm3, %ymm3 > > + > > + vmovdqu (VEC_SIZE * 3)(%rsi, %rdx), %ymm4 > > + VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm4, %ymm4 > > + > > + vpand %ymm1, %ymm2, %ymm5 > > + vpand %ymm3, %ymm4, %ymm6 > > + vpand %ymm5, %ymm6, %ymm7 > > + vpmovmskb %ymm7, %ecx > > + /* Restore s1 pointer to rdi. */ > > + movq %rdx, %rdi > > + incl %ecx > > + jnz L(8x_return_vec_0_1_2_3) > > + /* NB: eax must be zero to reach here. */ > > + VZEROUPPER_RETURN > > + > > + /* Only entry is from L(more_8x_vec). */ > > + .p2align 4 > > +L(8x_last_2x_vec): > > + /* Check second to last VEC. rdx store end pointer of s1 and > > + ymm3 has already been loaded with second to last VEC from s2. > > + */ > > + VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm3, %ymm3 > > + vpmovmskb %ymm3, %eax > > + incl %eax > > + jnz L(8x_return_vec_2) > > + /* Check last VEC. */ > > + .p2align 4 > > +L(8x_last_1x_vec): > > + vmovdqu (VEC_SIZE * 3)(%rsi, %rdx), %ymm4 > > + VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm4, %ymm4 > > + vpmovmskb %ymm4, %eax > > + incl %eax > > + jnz L(8x_return_vec_3) > > VZEROUPPER_RETURN > > > > .p2align 4 > > -L(first_vec): > > - /* A byte or int32 is different within 16 or 32 bytes. */ > > - tzcntl %eax, %ecx > > +L(last_2x_vec): > > + /* Check second to last VEC. */ > > + vmovdqu -(VEC_SIZE * 2)(%rsi, %rdx), %ymm1 > > + VPCMPEQ -(VEC_SIZE * 2)(%rdi, %rdx), %ymm1, %ymm1 > > + vpmovmskb %ymm1, %eax > > + incl %eax > > + jnz L(return_vec_1_end) > > + /* Check last VEC. */ > > +L(last_1x_vec): > > + vmovdqu -(VEC_SIZE * 1)(%rsi, %rdx), %ymm1 > > + VPCMPEQ -(VEC_SIZE * 1)(%rdi, %rdx), %ymm1, %ymm1 > > + vpmovmskb %ymm1, %eax > > + incl %eax > > + jnz L(return_vec_0_end) > > + VZEROUPPER_RETURN > > + > > + .p2align 4 > > +L(8x_return_vec_2): > > + subq $VEC_SIZE, %rdx > > +L(8x_return_vec_3): > > + tzcntl %eax, %eax > > + addq %rdx, %rax > > # ifdef USE_AS_WMEMCMP > > - xorl %eax, %eax > > - movl (%rdi, %rcx), %edx > > - cmpl (%rsi, %rcx), %edx > > -L(wmemcmp_return): > > - setl %al > > - negl %eax > > - orl $1, %eax > > + movl (VEC_SIZE * 3)(%rax), %ecx > > + xorl %edx, %edx > > + cmpl (VEC_SIZE * 3)(%rsi, %rax), %ecx > > + setg %dl > > + leal -1(%rdx, %rdx), %eax > > # else > > - movzbl (%rdi, %rcx), %eax > > - movzbl (%rsi, %rcx), %edx > > - sub %edx, %eax > > + movzbl (VEC_SIZE * 3)(%rsi, %rax), %ecx > > + movzbl (VEC_SIZE * 3)(%rax), %eax > > + subl %ecx, %eax > > # endif > > VZEROUPPER_RETURN > > > > -# ifdef USE_AS_WMEMCMP > > .p2align 4 > > -L(4): > > - xorl %eax, %eax > > - movl (%rdi), %edx > > - cmpl (%rsi), %edx > > - jne L(wmemcmp_return) > > - ret > > +L(return_vec_1_end): > > + tzcntl %eax, %eax > > + addl %edx, %eax > > +# ifdef USE_AS_WMEMCMP > > + movl -(VEC_SIZE * 2)(%rdi, %rax), %ecx > > + xorl %edx, %edx > > + cmpl -(VEC_SIZE * 2)(%rsi, %rax), %ecx > > + setg %dl > > + leal -1(%rdx, %rdx), %eax > > # else > > + movzbl -(VEC_SIZE * 2)(%rsi, %rax), %ecx > > + movzbl -(VEC_SIZE * 2)(%rdi, %rax), %eax > > + subl %ecx, %eax > > +# endif > > + VZEROUPPER_RETURN > > + > > .p2align 4 > > -L(between_4_7): > > - /* Load as big endian with overlapping movbe to avoid branches. */ > > - movbe (%rdi), %eax > > - movbe (%rsi), %ecx > > - shlq $32, %rax > > - shlq $32, %rcx > > - movbe -4(%rdi, %rdx), %edi > > - movbe -4(%rsi, %rdx), %esi > > - orq %rdi, %rax > > - orq %rsi, %rcx > > - subq %rcx, %rax > > - je L(exit) > > - sbbl %eax, %eax > > - orl $1, %eax > > - ret > > +L(return_vec_0_end): > > + tzcntl %eax, %eax > > + addl %edx, %eax > > +# ifdef USE_AS_WMEMCMP > > + movl -VEC_SIZE(%rdi, %rax), %ecx > > + xorl %edx, %edx > > + cmpl -VEC_SIZE(%rsi, %rax), %ecx > > + setg %dl > > + leal -1(%rdx, %rdx), %eax > > +# else > > + movzbl -VEC_SIZE(%rsi, %rax), %ecx > > + movzbl -VEC_SIZE(%rdi, %rax), %eax > > + subl %ecx, %eax > > +# endif > > + VZEROUPPER_RETURN > > > > .p2align 4 > > -L(exit): > > - ret > > +L(less_vec): > > + /* Check if one or less CHAR. This is necessary for size = 0 but > > + is also faster for size = CHAR_SIZE. */ > > + cmpl $CHAR_SIZE, %edx > > + jbe L(one_or_less) > > + > > + /* Check if loading one VEC from either s1 or s2 could cause a > > + page cross. This can have false positives but is by far the > > + fastest method. */ > > + movl %edi, %eax > > + orl %esi, %eax > > + andl $(PAGE_SIZE - 1), %eax > > + cmpl $(PAGE_SIZE - VEC_SIZE), %eax > > + jg L(page_cross_less_vec) > > + > > + /* No page cross possible. */ > > + vmovdqu (%rsi), %ymm2 > > + VPCMPEQ (%rdi), %ymm2, %ymm2 > > + vpmovmskb %ymm2, %eax > > + incl %eax > > + /* Result will be zero if s1 and s2 match. Otherwise first set > > + bit will be first mismatch. */ > > + bzhil %edx, %eax, %edx > > + jnz L(return_vec_0) > > + xorl %eax, %eax > > + VZEROUPPER_RETURN > > > > .p2align 4 > > -L(between_2_3): > > +L(page_cross_less_vec): > > + /* if USE_AS_WMEMCMP it can only be 0, 4, 8, 12, 16, 20, 24, 28 > > + bytes. */ > > + cmpl $16, %edx > > + jae L(between_16_31) > > +# ifndef USE_AS_WMEMCMP > > + cmpl $8, %edx > > + jae L(between_8_15) > > + cmpl $4, %edx > > + jae L(between_4_7) > > + > > /* Load as big endian to avoid branches. */ > > movzwl (%rdi), %eax > > movzwl (%rsi), %ecx > > @@ -208,223 +439,106 @@ L(between_2_3): > > shll $8, %ecx > > bswap %eax > > bswap %ecx > > - movb -1(%rdi, %rdx), %al > > - movb -1(%rsi, %rdx), %cl > > + movzbl -1(%rdi, %rdx), %edi > > + movzbl -1(%rsi, %rdx), %esi > > + orl %edi, %eax > > + orl %esi, %ecx > > /* Subtraction is okay because the upper 8 bits are zero. */ > > subl %ecx, %eax > > + /* No ymm register was touched. */ > > ret > > > > .p2align 4 > > -L(1): > > - movzbl (%rdi), %eax > > +L(one_or_less): > > + jb L(zero) > > movzbl (%rsi), %ecx > > + movzbl (%rdi), %eax > > subl %ecx, %eax > > - ret > > -# endif > > - > > - .p2align 4 > > -L(zero): > > - xorl %eax, %eax > > + /* No ymm register was touched. */ > > ret > > > > .p2align 4 > > -L(less_vec): > > -# ifdef USE_AS_WMEMCMP > > - /* It can only be 0, 4, 8, 12, 16, 20, 24, 28 bytes. */ > > - cmpb $4, %dl > > - je L(4) > > - jb L(zero) > > -# else > > - cmpb $1, %dl > > - je L(1) > > - jb L(zero) > > - cmpb $4, %dl > > - jb L(between_2_3) > > - cmpb $8, %dl > > - jb L(between_4_7) > > +L(between_8_15): > > # endif > > - cmpb $16, %dl > > - jae L(between_16_31) > > - /* It is between 8 and 15 bytes. */ > > + /* If USE_AS_WMEMCMP fall through into 8-15 byte case. */ > > vmovq (%rdi), %xmm1 > > vmovq (%rsi), %xmm2 > > - VPCMPEQ %xmm1, %xmm2, %xmm2 > > + VPCMPEQ %xmm1, %xmm2, %xmm2 > > vpmovmskb %xmm2, %eax > > - subl $0xffff, %eax > > - jnz L(first_vec) > > + subl $0xffff, %eax > > + jnz L(return_vec_0) > > /* Use overlapping loads to avoid branches. */ > > leaq -8(%rdi, %rdx), %rdi > > leaq -8(%rsi, %rdx), %rsi > > vmovq (%rdi), %xmm1 > > vmovq (%rsi), %xmm2 > > - VPCMPEQ %xmm1, %xmm2, %xmm2 > > + VPCMPEQ %xmm1, %xmm2, %xmm2 > > vpmovmskb %xmm2, %eax > > - subl $0xffff, %eax > > - jnz L(first_vec) > > + subl $0xffff, %eax > > + jnz L(return_vec_0) > > + /* No ymm register was touched. */ > > + ret > > + > > + .p2align 4 > > +L(zero): > > + xorl %eax, %eax > > ret > > > > .p2align 4 > > L(between_16_31): > > /* From 16 to 31 bytes. No branch when size == 16. */ > > vmovdqu (%rsi), %xmm2 > > - VPCMPEQ (%rdi), %xmm2, %xmm2 > > + VPCMPEQ (%rdi), %xmm2, %xmm2 > > vpmovmskb %xmm2, %eax > > - subl $0xffff, %eax > > - jnz L(first_vec) > > + subl $0xffff, %eax > > + jnz L(return_vec_0) > > > > /* Use overlapping loads to avoid branches. */ > > + > > + vmovdqu -16(%rsi, %rdx), %xmm2 > > leaq -16(%rdi, %rdx), %rdi > > leaq -16(%rsi, %rdx), %rsi > > - vmovdqu (%rsi), %xmm2 > > - VPCMPEQ (%rdi), %xmm2, %xmm2 > > + VPCMPEQ (%rdi), %xmm2, %xmm2 > > vpmovmskb %xmm2, %eax > > - subl $0xffff, %eax > > - jnz L(first_vec) > > + subl $0xffff, %eax > > + jnz L(return_vec_0) > > + /* No ymm register was touched. */ > > ret > > > > - .p2align 4 > > -L(more_8x_vec): > > - /* More than 8 * VEC. Check the first VEC. */ > > - vmovdqu (%rsi), %ymm2 > > - VPCMPEQ (%rdi), %ymm2, %ymm2 > > - vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > - > > - /* Align the first memory area for aligned loads in the loop. > > - Compute how much the first memory area is misaligned. */ > > - movq %rdi, %rcx > > - andl $(VEC_SIZE - 1), %ecx > > - /* Get the negative of offset for alignment. */ > > - subq $VEC_SIZE, %rcx > > - /* Adjust the second memory area. */ > > - subq %rcx, %rsi > > - /* Adjust the first memory area which should be aligned now. */ > > - subq %rcx, %rdi > > - /* Adjust length. */ > > - addq %rcx, %rdx > > - > > -L(loop_4x_vec): > > - /* Compare 4 * VEC at a time forward. */ > > - vmovdqu (%rsi), %ymm1 > > - VPCMPEQ (%rdi), %ymm1, %ymm1 > > - > > - vmovdqu VEC_SIZE(%rsi), %ymm2 > > - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 > > - vpand %ymm2, %ymm1, %ymm5 > > - > > - vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 > > - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 > > - vpand %ymm3, %ymm5, %ymm5 > > - > > - vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 > > - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 > > - vpand %ymm4, %ymm5, %ymm5 > > - > > - vptest %ymm0, %ymm5 > > - jnc L(4x_vec_end) > > - > > - addq $(VEC_SIZE * 4), %rdi > > - addq $(VEC_SIZE * 4), %rsi > > - > > - subq $(VEC_SIZE * 4), %rdx > > - cmpq $(VEC_SIZE * 4), %rdx > > - jae L(loop_4x_vec) > > - > > - /* Less than 4 * VEC. */ > > - cmpq $VEC_SIZE, %rdx > > - jbe L(last_vec) > > - cmpq $(VEC_SIZE * 2), %rdx > > - jbe L(last_2x_vec) > > - > > -L(last_4x_vec): > > - /* From 2 * VEC to 4 * VEC. */ > > - vmovdqu (%rsi), %ymm2 > > - VPCMPEQ (%rdi), %ymm2, %ymm2 > > - vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > - > > - addq $VEC_SIZE, %rdi > > - addq $VEC_SIZE, %rsi > > - vmovdqu (%rsi), %ymm2 > > - VPCMPEQ (%rdi), %ymm2, %ymm2 > > - vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > - > > - /* Use overlapping loads to avoid branches. */ > > - leaq -(3 * VEC_SIZE)(%rdi, %rdx), %rdi > > - leaq -(3 * VEC_SIZE)(%rsi, %rdx), %rsi > > - vmovdqu (%rsi), %ymm2 > > - VPCMPEQ (%rdi), %ymm2, %ymm2 > > - vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > - > > - addq $VEC_SIZE, %rdi > > - addq $VEC_SIZE, %rsi > > - vmovdqu (%rsi), %ymm2 > > - VPCMPEQ (%rdi), %ymm2, %ymm2 > > - vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > - VZEROUPPER_RETURN > > - > > - .p2align 4 > > -L(4x_vec_end): > > - vpmovmskb %ymm1, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec) > > - vpmovmskb %ymm2, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec_x1) > > - vpmovmskb %ymm3, %eax > > - subl $VEC_MASK, %eax > > - jnz L(first_vec_x2) > > - vpmovmskb %ymm4, %eax > > - subl $VEC_MASK, %eax > > - tzcntl %eax, %ecx > > # ifdef USE_AS_WMEMCMP > > - xorl %eax, %eax > > - movl (VEC_SIZE * 3)(%rdi, %rcx), %edx > > - cmpl (VEC_SIZE * 3)(%rsi, %rcx), %edx > > - jmp L(wmemcmp_return) > > -# else > > - movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax > > - movzbl (VEC_SIZE * 3)(%rsi, %rcx), %edx > > - sub %edx, %eax > > -# endif > > - VZEROUPPER_RETURN > > - > > .p2align 4 > > -L(first_vec_x1): > > - tzcntl %eax, %ecx > > -# ifdef USE_AS_WMEMCMP > > - xorl %eax, %eax > > - movl VEC_SIZE(%rdi, %rcx), %edx > > - cmpl VEC_SIZE(%rsi, %rcx), %edx > > - jmp L(wmemcmp_return) > > +L(one_or_less): > > + jb L(zero) > > + movl (%rdi), %ecx > > + xorl %edx, %edx > > + cmpl (%rsi), %ecx > > + je L(zero) > > + setg %dl > > + leal -1(%rdx, %rdx), %eax > > + /* No ymm register was touched. */ > > + ret > > # else > > - movzbl VEC_SIZE(%rdi, %rcx), %eax > > - movzbl VEC_SIZE(%rsi, %rcx), %edx > > - sub %edx, %eax > > -# endif > > - VZEROUPPER_RETURN > > > > .p2align 4 > > -L(first_vec_x2): > > - tzcntl %eax, %ecx > > -# ifdef USE_AS_WMEMCMP > > - xorl %eax, %eax > > - movl (VEC_SIZE * 2)(%rdi, %rcx), %edx > > - cmpl (VEC_SIZE * 2)(%rsi, %rcx), %edx > > - jmp L(wmemcmp_return) > > -# else > > - movzbl (VEC_SIZE * 2)(%rdi, %rcx), %eax > > - movzbl (VEC_SIZE * 2)(%rsi, %rcx), %edx > > - sub %edx, %eax > > +L(between_4_7): > > + /* Load as big endian with overlapping movbe to avoid branches. > > + */ > > + movbe (%rdi), %eax > > + movbe (%rsi), %ecx > > + shlq $32, %rax > > + shlq $32, %rcx > > + movbe -4(%rdi, %rdx), %edi > > + movbe -4(%rsi, %rdx), %esi > > + orq %rdi, %rax > > + orq %rsi, %rcx > > + subq %rcx, %rax > > + jz L(zero_4_7) > > + sbbl %eax, %eax > > + orl $1, %eax > > +L(zero_4_7): > > + /* No ymm register was touched. */ > > + ret > > # endif > > - VZEROUPPER_RETURN > > + > > END (MEMCMP) > > #endif > > -- > > 2.29.2 > > > > > H.J.
diff --git a/sysdeps/x86_64/multiarch/ifunc-memcmp.h b/sysdeps/x86_64/multiarch/ifunc-memcmp.h index 8bee1aff75..89e2129968 100644 --- a/sysdeps/x86_64/multiarch/ifunc-memcmp.h +++ b/sysdeps/x86_64/multiarch/ifunc-memcmp.h @@ -33,6 +33,7 @@ IFUNC_SELECTOR (void) if (CPU_FEATURE_USABLE_P (cpu_features, AVX2) && CPU_FEATURE_USABLE_P (cpu_features, MOVBE) + && CPU_FEATURE_USABLE_P (cpu_features, BMI2) && CPU_FEATURES_ARCH_P (cpu_features, AVX_Fast_Unaligned_Load)) { if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL) diff --git a/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S b/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S index ad0fa962a1..2621ec907a 100644 --- a/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S +++ b/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S @@ -19,17 +19,23 @@ #if IS_IN (libc) /* memcmp/wmemcmp is implemented as: - 1. For size from 2 to 7 bytes, load as big endian with movbe and bswap - to avoid branches. - 2. Use overlapping compare to avoid branch. - 3. Use vector compare when size >= 4 bytes for memcmp or size >= 8 - bytes for wmemcmp. - 4. If size is 8 * VEC_SIZE or less, unroll the loop. - 5. Compare 4 * VEC_SIZE at a time with the aligned first memory + 1. Use ymm vector compares when possible. The only case where + vector compares is not possible for when size < VEC_SIZE + and loading from either s1 or s2 would cause a page cross. + 2. For size from 2 to 7 bytes on page cross, load as big endian + with movbe and bswap to avoid branches. + 3. Use xmm vector compare when size >= 4 bytes for memcmp or + size >= 8 bytes for wmemcmp. + 4. Optimistically compare up to first 4 * VEC_SIZE one at a + to check for early mismatches. Only do this if its guranteed the + work is not wasted. + 5. If size is 8 * VEC_SIZE or less, unroll the loop. + 6. Compare 4 * VEC_SIZE at a time with the aligned first memory area. - 6. Use 2 vector compares when size is 2 * VEC_SIZE or less. - 7. Use 4 vector compares when size is 4 * VEC_SIZE or less. - 8. Use 8 vector compares when size is 8 * VEC_SIZE or less. */ + 7. Use 2 vector compares when size is 2 * VEC_SIZE or less. + 8. Use 4 vector compares when size is 4 * VEC_SIZE or less. + 9. Use 8 vector compares when size is 8 * VEC_SIZE or less. */ + # include <sysdep.h> @@ -38,8 +44,10 @@ # endif # ifdef USE_AS_WMEMCMP +# define CHAR_SIZE 4 # define VPCMPEQ vpcmpeqd # else +# define CHAR_SIZE 1 # define VPCMPEQ vpcmpeqb # endif @@ -52,7 +60,7 @@ # endif # define VEC_SIZE 32 -# define VEC_MASK ((1 << VEC_SIZE) - 1) +# define PAGE_SIZE 4096 /* Warning! wmemcmp has to use SIGNED comparison for elements. @@ -71,136 +79,359 @@ ENTRY (MEMCMP) jb L(less_vec) /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */ - vmovdqu (%rsi), %ymm2 - VPCMPEQ (%rdi), %ymm2, %ymm2 - vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) + vmovdqu (%rsi), %ymm1 + VPCMPEQ (%rdi), %ymm1, %ymm1 + vpmovmskb %ymm1, %eax + /* NB: eax must be destination register if going to + L(return_vec_[0,2]). For L(return_vec_3 destination register + must be ecx. */ + incl %eax + jnz L(return_vec_0) cmpq $(VEC_SIZE * 2), %rdx - jbe L(last_vec) - - VPCMPEQ %ymm0, %ymm0, %ymm0 - /* More than 2 * VEC. */ - cmpq $(VEC_SIZE * 8), %rdx - ja L(more_8x_vec) - cmpq $(VEC_SIZE * 4), %rdx - jb L(last_4x_vec) - - /* From 4 * VEC to 8 * VEC, inclusively. */ - vmovdqu (%rsi), %ymm1 - VPCMPEQ (%rdi), %ymm1, %ymm1 + jbe L(last_1x_vec) + /* Check second VEC no matter what. */ vmovdqu VEC_SIZE(%rsi), %ymm2 - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 + VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 + vpmovmskb %ymm2, %eax + /* If all 4 VEC where equal eax will be all 1s so incl will + overflow and set zero flag. */ + incl %eax + jnz L(return_vec_1) - vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 + /* Less than 4 * VEC. */ + cmpq $(VEC_SIZE * 4), %rdx + jbe L(last_2x_vec) + /* Check third and fourth VEC no matter what. */ + vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 + vpmovmskb %ymm3, %eax + incl %eax + jnz L(return_vec_2) vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 + vpmovmskb %ymm4, %ecx + incl %ecx + jnz L(return_vec_3) - vpand %ymm1, %ymm2, %ymm5 - vpand %ymm3, %ymm4, %ymm6 - vpand %ymm5, %ymm6, %ymm5 + /* Go to 4x VEC loop. */ + cmpq $(VEC_SIZE * 8), %rdx + ja L(more_8x_vec) - vptest %ymm0, %ymm5 - jnc L(4x_vec_end) + /* Handle remainder of size = 4 * VEC + 1 to 8 * VEC without any + branches. */ + /* Load first two VEC from s2 before adjusting addresses. */ + vmovdqu -(VEC_SIZE * 4)(%rsi, %rdx), %ymm1 + vmovdqu -(VEC_SIZE * 3)(%rsi, %rdx), %ymm2 leaq -(4 * VEC_SIZE)(%rdi, %rdx), %rdi leaq -(4 * VEC_SIZE)(%rsi, %rdx), %rsi - vmovdqu (%rsi), %ymm1 - VPCMPEQ (%rdi), %ymm1, %ymm1 - vmovdqu VEC_SIZE(%rsi), %ymm2 - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 - vpand %ymm2, %ymm1, %ymm5 + /* Wait to load from s1 until addressed adjust due to + unlamination of microfusion with complex address mode. */ + VPCMPEQ (%rdi), %ymm1, %ymm1 + VPCMPEQ (VEC_SIZE)(%rdi), %ymm2, %ymm2 vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 - vpand %ymm3, %ymm5, %ymm5 - + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 - vpand %ymm4, %ymm5, %ymm5 + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 - vptest %ymm0, %ymm5 - jnc L(4x_vec_end) - xorl %eax, %eax + /* Reduce VEC0 - VEC4. */ + vpand %ymm1, %ymm2, %ymm5 + vpand %ymm3, %ymm4, %ymm6 + vpand %ymm5, %ymm6, %ymm7 + vpmovmskb %ymm7, %ecx + incl %ecx + jnz L(return_vec_0_1_2_3) + /* NB: eax must be zero to reach here. */ + VZEROUPPER_RETURN + + .p2align 4 +L(return_vec_0): + tzcntl %eax, %eax +# ifdef USE_AS_WMEMCMP + movl (%rdi, %rax), %ecx + xorl %edx, %edx + cmpl (%rsi, %rax), %ecx + /* NB: no partial register stall here because xorl zero idiom + above. */ + setg %dl + leal -1(%rdx, %rdx), %eax +# else + movzbl (%rsi, %rax), %ecx + movzbl (%rdi, %rax), %eax + subl %ecx, %eax +# endif L(return_vzeroupper): ZERO_UPPER_VEC_REGISTERS_RETURN .p2align 4 -L(last_2x_vec): - /* From VEC to 2 * VEC. No branch when size == VEC_SIZE. */ - vmovdqu (%rsi), %ymm2 - VPCMPEQ (%rdi), %ymm2, %ymm2 - vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) +L(return_vec_1): + tzcntl %eax, %eax +# ifdef USE_AS_WMEMCMP + movl VEC_SIZE(%rdi, %rax), %ecx + xorl %edx, %edx + cmpl VEC_SIZE(%rsi, %rax), %ecx + setg %dl + leal -1(%rdx, %rdx), %eax +# else + movzbl VEC_SIZE(%rsi, %rax), %ecx + movzbl VEC_SIZE(%rdi, %rax), %eax + subl %ecx, %eax +# endif + VZEROUPPER_RETURN + + .p2align 4 +L(return_vec_2): + tzcntl %eax, %eax +# ifdef USE_AS_WMEMCMP + movl (VEC_SIZE * 2)(%rdi, %rax), %ecx + xorl %edx, %edx + cmpl (VEC_SIZE * 2)(%rsi, %rax), %ecx + setg %dl + leal -1(%rdx, %rdx), %eax +# else + movzbl (VEC_SIZE * 2)(%rsi, %rax), %ecx + movzbl (VEC_SIZE * 2)(%rdi, %rax), %eax + subl %ecx, %eax +# endif + VZEROUPPER_RETURN + + /* NB: p2align 5 here to ensure 4x loop is 32 byte aligned. */ + .p2align 5 +L(8x_return_vec_0_1_2_3): + /* Returning from L(more_8x_vec) requires restoring rsi. */ + addq %rdi, %rsi +L(return_vec_0_1_2_3): + vpmovmskb %ymm1, %eax + incl %eax + jnz L(return_vec_0) -L(last_vec): - /* Use overlapping loads to avoid branches. */ - leaq -VEC_SIZE(%rdi, %rdx), %rdi - leaq -VEC_SIZE(%rsi, %rdx), %rsi - vmovdqu (%rsi), %ymm2 - VPCMPEQ (%rdi), %ymm2, %ymm2 vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) + incl %eax + jnz L(return_vec_1) + + vpmovmskb %ymm3, %eax + incl %eax + jnz L(return_vec_2) +L(return_vec_3): + tzcntl %ecx, %ecx +# ifdef USE_AS_WMEMCMP + movl (VEC_SIZE * 3)(%rdi, %rcx), %eax + xorl %edx, %edx + cmpl (VEC_SIZE * 3)(%rsi, %rcx), %eax + setg %dl + leal -1(%rdx, %rdx), %eax +# else + movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax + movzbl (VEC_SIZE * 3)(%rsi, %rcx), %ecx + subl %ecx, %eax +# endif + VZEROUPPER_RETURN + + .p2align 4 +L(more_8x_vec): + /* Set end of s1 in rdx. */ + leaq -(VEC_SIZE * 4)(%rdi, %rdx), %rdx + /* rsi stores s2 - s1. This allows loop to only update one + pointer. */ + subq %rdi, %rsi + /* Align s1 pointer. */ + andq $-VEC_SIZE, %rdi + /* Adjust because first 4x vec where check already. */ + subq $-(VEC_SIZE * 4), %rdi + .p2align 4 +L(loop_4x_vec): + /* rsi has s2 - s1 so get correct address by adding s1 (in rdi). + */ + vmovdqu (%rsi, %rdi), %ymm1 + VPCMPEQ (%rdi), %ymm1, %ymm1 + + vmovdqu VEC_SIZE(%rsi, %rdi), %ymm2 + VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 + + vmovdqu (VEC_SIZE * 2)(%rsi, %rdi), %ymm3 + VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 + + vmovdqu (VEC_SIZE * 3)(%rsi, %rdi), %ymm4 + VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 + + vpand %ymm1, %ymm2, %ymm5 + vpand %ymm3, %ymm4, %ymm6 + vpand %ymm5, %ymm6, %ymm7 + vpmovmskb %ymm7, %ecx + incl %ecx + jnz L(8x_return_vec_0_1_2_3) + subq $-(VEC_SIZE * 4), %rdi + /* Check if s1 pointer at end. */ + cmpq %rdx, %rdi + jb L(loop_4x_vec) + + subq %rdx, %rdi + /* rdi has 4 * VEC_SIZE - remaining length. */ + cmpl $(VEC_SIZE * 3), %edi + jae L(8x_last_1x_vec) + /* Load regardless of branch. */ + vmovdqu (VEC_SIZE * 2)(%rsi, %rdx), %ymm3 + cmpl $(VEC_SIZE * 2), %edi + jae L(8x_last_2x_vec) + + /* Check last 4 VEC. */ + vmovdqu (%rsi, %rdx), %ymm1 + VPCMPEQ (%rdx), %ymm1, %ymm1 + + vmovdqu VEC_SIZE(%rsi, %rdx), %ymm2 + VPCMPEQ VEC_SIZE(%rdx), %ymm2, %ymm2 + + VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm3, %ymm3 + + vmovdqu (VEC_SIZE * 3)(%rsi, %rdx), %ymm4 + VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm4, %ymm4 + + vpand %ymm1, %ymm2, %ymm5 + vpand %ymm3, %ymm4, %ymm6 + vpand %ymm5, %ymm6, %ymm7 + vpmovmskb %ymm7, %ecx + /* Restore s1 pointer to rdi. */ + movq %rdx, %rdi + incl %ecx + jnz L(8x_return_vec_0_1_2_3) + /* NB: eax must be zero to reach here. */ + VZEROUPPER_RETURN + + /* Only entry is from L(more_8x_vec). */ + .p2align 4 +L(8x_last_2x_vec): + /* Check second to last VEC. rdx store end pointer of s1 and + ymm3 has already been loaded with second to last VEC from s2. + */ + VPCMPEQ (VEC_SIZE * 2)(%rdx), %ymm3, %ymm3 + vpmovmskb %ymm3, %eax + incl %eax + jnz L(8x_return_vec_2) + /* Check last VEC. */ + .p2align 4 +L(8x_last_1x_vec): + vmovdqu (VEC_SIZE * 3)(%rsi, %rdx), %ymm4 + VPCMPEQ (VEC_SIZE * 3)(%rdx), %ymm4, %ymm4 + vpmovmskb %ymm4, %eax + incl %eax + jnz L(8x_return_vec_3) VZEROUPPER_RETURN .p2align 4 -L(first_vec): - /* A byte or int32 is different within 16 or 32 bytes. */ - tzcntl %eax, %ecx +L(last_2x_vec): + /* Check second to last VEC. */ + vmovdqu -(VEC_SIZE * 2)(%rsi, %rdx), %ymm1 + VPCMPEQ -(VEC_SIZE * 2)(%rdi, %rdx), %ymm1, %ymm1 + vpmovmskb %ymm1, %eax + incl %eax + jnz L(return_vec_1_end) + /* Check last VEC. */ +L(last_1x_vec): + vmovdqu -(VEC_SIZE * 1)(%rsi, %rdx), %ymm1 + VPCMPEQ -(VEC_SIZE * 1)(%rdi, %rdx), %ymm1, %ymm1 + vpmovmskb %ymm1, %eax + incl %eax + jnz L(return_vec_0_end) + VZEROUPPER_RETURN + + .p2align 4 +L(8x_return_vec_2): + subq $VEC_SIZE, %rdx +L(8x_return_vec_3): + tzcntl %eax, %eax + addq %rdx, %rax # ifdef USE_AS_WMEMCMP - xorl %eax, %eax - movl (%rdi, %rcx), %edx - cmpl (%rsi, %rcx), %edx -L(wmemcmp_return): - setl %al - negl %eax - orl $1, %eax + movl (VEC_SIZE * 3)(%rax), %ecx + xorl %edx, %edx + cmpl (VEC_SIZE * 3)(%rsi, %rax), %ecx + setg %dl + leal -1(%rdx, %rdx), %eax # else - movzbl (%rdi, %rcx), %eax - movzbl (%rsi, %rcx), %edx - sub %edx, %eax + movzbl (VEC_SIZE * 3)(%rsi, %rax), %ecx + movzbl (VEC_SIZE * 3)(%rax), %eax + subl %ecx, %eax # endif VZEROUPPER_RETURN -# ifdef USE_AS_WMEMCMP .p2align 4 -L(4): - xorl %eax, %eax - movl (%rdi), %edx - cmpl (%rsi), %edx - jne L(wmemcmp_return) - ret +L(return_vec_1_end): + tzcntl %eax, %eax + addl %edx, %eax +# ifdef USE_AS_WMEMCMP + movl -(VEC_SIZE * 2)(%rdi, %rax), %ecx + xorl %edx, %edx + cmpl -(VEC_SIZE * 2)(%rsi, %rax), %ecx + setg %dl + leal -1(%rdx, %rdx), %eax # else + movzbl -(VEC_SIZE * 2)(%rsi, %rax), %ecx + movzbl -(VEC_SIZE * 2)(%rdi, %rax), %eax + subl %ecx, %eax +# endif + VZEROUPPER_RETURN + .p2align 4 -L(between_4_7): - /* Load as big endian with overlapping movbe to avoid branches. */ - movbe (%rdi), %eax - movbe (%rsi), %ecx - shlq $32, %rax - shlq $32, %rcx - movbe -4(%rdi, %rdx), %edi - movbe -4(%rsi, %rdx), %esi - orq %rdi, %rax - orq %rsi, %rcx - subq %rcx, %rax - je L(exit) - sbbl %eax, %eax - orl $1, %eax - ret +L(return_vec_0_end): + tzcntl %eax, %eax + addl %edx, %eax +# ifdef USE_AS_WMEMCMP + movl -VEC_SIZE(%rdi, %rax), %ecx + xorl %edx, %edx + cmpl -VEC_SIZE(%rsi, %rax), %ecx + setg %dl + leal -1(%rdx, %rdx), %eax +# else + movzbl -VEC_SIZE(%rsi, %rax), %ecx + movzbl -VEC_SIZE(%rdi, %rax), %eax + subl %ecx, %eax +# endif + VZEROUPPER_RETURN .p2align 4 -L(exit): - ret +L(less_vec): + /* Check if one or less CHAR. This is necessary for size = 0 but + is also faster for size = CHAR_SIZE. */ + cmpl $CHAR_SIZE, %edx + jbe L(one_or_less) + + /* Check if loading one VEC from either s1 or s2 could cause a + page cross. This can have false positives but is by far the + fastest method. */ + movl %edi, %eax + orl %esi, %eax + andl $(PAGE_SIZE - 1), %eax + cmpl $(PAGE_SIZE - VEC_SIZE), %eax + jg L(page_cross_less_vec) + + /* No page cross possible. */ + vmovdqu (%rsi), %ymm2 + VPCMPEQ (%rdi), %ymm2, %ymm2 + vpmovmskb %ymm2, %eax + incl %eax + /* Result will be zero if s1 and s2 match. Otherwise first set + bit will be first mismatch. */ + bzhil %edx, %eax, %edx + jnz L(return_vec_0) + xorl %eax, %eax + VZEROUPPER_RETURN .p2align 4 -L(between_2_3): +L(page_cross_less_vec): + /* if USE_AS_WMEMCMP it can only be 0, 4, 8, 12, 16, 20, 24, 28 + bytes. */ + cmpl $16, %edx + jae L(between_16_31) +# ifndef USE_AS_WMEMCMP + cmpl $8, %edx + jae L(between_8_15) + cmpl $4, %edx + jae L(between_4_7) + /* Load as big endian to avoid branches. */ movzwl (%rdi), %eax movzwl (%rsi), %ecx @@ -208,223 +439,106 @@ L(between_2_3): shll $8, %ecx bswap %eax bswap %ecx - movb -1(%rdi, %rdx), %al - movb -1(%rsi, %rdx), %cl + movzbl -1(%rdi, %rdx), %edi + movzbl -1(%rsi, %rdx), %esi + orl %edi, %eax + orl %esi, %ecx /* Subtraction is okay because the upper 8 bits are zero. */ subl %ecx, %eax + /* No ymm register was touched. */ ret .p2align 4 -L(1): - movzbl (%rdi), %eax +L(one_or_less): + jb L(zero) movzbl (%rsi), %ecx + movzbl (%rdi), %eax subl %ecx, %eax - ret -# endif - - .p2align 4 -L(zero): - xorl %eax, %eax + /* No ymm register was touched. */ ret .p2align 4 -L(less_vec): -# ifdef USE_AS_WMEMCMP - /* It can only be 0, 4, 8, 12, 16, 20, 24, 28 bytes. */ - cmpb $4, %dl - je L(4) - jb L(zero) -# else - cmpb $1, %dl - je L(1) - jb L(zero) - cmpb $4, %dl - jb L(between_2_3) - cmpb $8, %dl - jb L(between_4_7) +L(between_8_15): # endif - cmpb $16, %dl - jae L(between_16_31) - /* It is between 8 and 15 bytes. */ + /* If USE_AS_WMEMCMP fall through into 8-15 byte case. */ vmovq (%rdi), %xmm1 vmovq (%rsi), %xmm2 - VPCMPEQ %xmm1, %xmm2, %xmm2 + VPCMPEQ %xmm1, %xmm2, %xmm2 vpmovmskb %xmm2, %eax - subl $0xffff, %eax - jnz L(first_vec) + subl $0xffff, %eax + jnz L(return_vec_0) /* Use overlapping loads to avoid branches. */ leaq -8(%rdi, %rdx), %rdi leaq -8(%rsi, %rdx), %rsi vmovq (%rdi), %xmm1 vmovq (%rsi), %xmm2 - VPCMPEQ %xmm1, %xmm2, %xmm2 + VPCMPEQ %xmm1, %xmm2, %xmm2 vpmovmskb %xmm2, %eax - subl $0xffff, %eax - jnz L(first_vec) + subl $0xffff, %eax + jnz L(return_vec_0) + /* No ymm register was touched. */ + ret + + .p2align 4 +L(zero): + xorl %eax, %eax ret .p2align 4 L(between_16_31): /* From 16 to 31 bytes. No branch when size == 16. */ vmovdqu (%rsi), %xmm2 - VPCMPEQ (%rdi), %xmm2, %xmm2 + VPCMPEQ (%rdi), %xmm2, %xmm2 vpmovmskb %xmm2, %eax - subl $0xffff, %eax - jnz L(first_vec) + subl $0xffff, %eax + jnz L(return_vec_0) /* Use overlapping loads to avoid branches. */ + + vmovdqu -16(%rsi, %rdx), %xmm2 leaq -16(%rdi, %rdx), %rdi leaq -16(%rsi, %rdx), %rsi - vmovdqu (%rsi), %xmm2 - VPCMPEQ (%rdi), %xmm2, %xmm2 + VPCMPEQ (%rdi), %xmm2, %xmm2 vpmovmskb %xmm2, %eax - subl $0xffff, %eax - jnz L(first_vec) + subl $0xffff, %eax + jnz L(return_vec_0) + /* No ymm register was touched. */ ret - .p2align 4 -L(more_8x_vec): - /* More than 8 * VEC. Check the first VEC. */ - vmovdqu (%rsi), %ymm2 - VPCMPEQ (%rdi), %ymm2, %ymm2 - vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) - - /* Align the first memory area for aligned loads in the loop. - Compute how much the first memory area is misaligned. */ - movq %rdi, %rcx - andl $(VEC_SIZE - 1), %ecx - /* Get the negative of offset for alignment. */ - subq $VEC_SIZE, %rcx - /* Adjust the second memory area. */ - subq %rcx, %rsi - /* Adjust the first memory area which should be aligned now. */ - subq %rcx, %rdi - /* Adjust length. */ - addq %rcx, %rdx - -L(loop_4x_vec): - /* Compare 4 * VEC at a time forward. */ - vmovdqu (%rsi), %ymm1 - VPCMPEQ (%rdi), %ymm1, %ymm1 - - vmovdqu VEC_SIZE(%rsi), %ymm2 - VPCMPEQ VEC_SIZE(%rdi), %ymm2, %ymm2 - vpand %ymm2, %ymm1, %ymm5 - - vmovdqu (VEC_SIZE * 2)(%rsi), %ymm3 - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm3, %ymm3 - vpand %ymm3, %ymm5, %ymm5 - - vmovdqu (VEC_SIZE * 3)(%rsi), %ymm4 - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm4, %ymm4 - vpand %ymm4, %ymm5, %ymm5 - - vptest %ymm0, %ymm5 - jnc L(4x_vec_end) - - addq $(VEC_SIZE * 4), %rdi - addq $(VEC_SIZE * 4), %rsi - - subq $(VEC_SIZE * 4), %rdx - cmpq $(VEC_SIZE * 4), %rdx - jae L(loop_4x_vec) - - /* Less than 4 * VEC. */ - cmpq $VEC_SIZE, %rdx - jbe L(last_vec) - cmpq $(VEC_SIZE * 2), %rdx - jbe L(last_2x_vec) - -L(last_4x_vec): - /* From 2 * VEC to 4 * VEC. */ - vmovdqu (%rsi), %ymm2 - VPCMPEQ (%rdi), %ymm2, %ymm2 - vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) - - addq $VEC_SIZE, %rdi - addq $VEC_SIZE, %rsi - vmovdqu (%rsi), %ymm2 - VPCMPEQ (%rdi), %ymm2, %ymm2 - vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) - - /* Use overlapping loads to avoid branches. */ - leaq -(3 * VEC_SIZE)(%rdi, %rdx), %rdi - leaq -(3 * VEC_SIZE)(%rsi, %rdx), %rsi - vmovdqu (%rsi), %ymm2 - VPCMPEQ (%rdi), %ymm2, %ymm2 - vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) - - addq $VEC_SIZE, %rdi - addq $VEC_SIZE, %rsi - vmovdqu (%rsi), %ymm2 - VPCMPEQ (%rdi), %ymm2, %ymm2 - vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) - VZEROUPPER_RETURN - - .p2align 4 -L(4x_vec_end): - vpmovmskb %ymm1, %eax - subl $VEC_MASK, %eax - jnz L(first_vec) - vpmovmskb %ymm2, %eax - subl $VEC_MASK, %eax - jnz L(first_vec_x1) - vpmovmskb %ymm3, %eax - subl $VEC_MASK, %eax - jnz L(first_vec_x2) - vpmovmskb %ymm4, %eax - subl $VEC_MASK, %eax - tzcntl %eax, %ecx # ifdef USE_AS_WMEMCMP - xorl %eax, %eax - movl (VEC_SIZE * 3)(%rdi, %rcx), %edx - cmpl (VEC_SIZE * 3)(%rsi, %rcx), %edx - jmp L(wmemcmp_return) -# else - movzbl (VEC_SIZE * 3)(%rdi, %rcx), %eax - movzbl (VEC_SIZE * 3)(%rsi, %rcx), %edx - sub %edx, %eax -# endif - VZEROUPPER_RETURN - .p2align 4 -L(first_vec_x1): - tzcntl %eax, %ecx -# ifdef USE_AS_WMEMCMP - xorl %eax, %eax - movl VEC_SIZE(%rdi, %rcx), %edx - cmpl VEC_SIZE(%rsi, %rcx), %edx - jmp L(wmemcmp_return) +L(one_or_less): + jb L(zero) + movl (%rdi), %ecx + xorl %edx, %edx + cmpl (%rsi), %ecx + je L(zero) + setg %dl + leal -1(%rdx, %rdx), %eax + /* No ymm register was touched. */ + ret # else - movzbl VEC_SIZE(%rdi, %rcx), %eax - movzbl VEC_SIZE(%rsi, %rcx), %edx - sub %edx, %eax -# endif - VZEROUPPER_RETURN .p2align 4 -L(first_vec_x2): - tzcntl %eax, %ecx -# ifdef USE_AS_WMEMCMP - xorl %eax, %eax - movl (VEC_SIZE * 2)(%rdi, %rcx), %edx - cmpl (VEC_SIZE * 2)(%rsi, %rcx), %edx - jmp L(wmemcmp_return) -# else - movzbl (VEC_SIZE * 2)(%rdi, %rcx), %eax - movzbl (VEC_SIZE * 2)(%rsi, %rcx), %edx - sub %edx, %eax +L(between_4_7): + /* Load as big endian with overlapping movbe to avoid branches. + */ + movbe (%rdi), %eax + movbe (%rsi), %ecx + shlq $32, %rax + shlq $32, %rcx + movbe -4(%rdi, %rdx), %edi + movbe -4(%rsi, %rdx), %esi + orq %rdi, %rax + orq %rsi, %rcx + subq %rcx, %rax + jz L(zero_4_7) + sbbl %eax, %eax + orl $1, %eax +L(zero_4_7): + /* No ymm register was touched. */ + ret # endif - VZEROUPPER_RETURN + END (MEMCMP) #endif
No bug. This commit optimizes memcmp-avx2.S. The optimizations include adding a new vec compare path for small sizes, reorganizing the entry control flow, and removing some unnecissary ALU instructions from the main loop. test-memcmp and test-wmemcmp are both passing. Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com> --- sysdeps/x86_64/multiarch/ifunc-memcmp.h | 1 + sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S | 676 +++++++++++-------- 2 files changed, 396 insertions(+), 281 deletions(-)