[PATCH v5 2/2] x86: Optimize strlen-avx2.S
Sunil Pandey
skpgkp2@gmail.com
Wed Sep 28 14:54:35 GMT 2022
On Wed, Sep 28, 2022 at 7:42 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> On Wed, Sep 28, 2022 at 6:55 AM Sunil Pandey <skpgkp2@gmail.com> wrote:
> >
> > Attached patch fixes BZ# 29611.
> >
> > I would like to backport it to 2.32,2.31,2.30,2.29 and 2.29. Let me know
> > if there is any objection.
> The ifunc-impl-list changes are missing BMI2 for memchr-avx2.S
>
> Can you post these as separate emails with the patches embedded instead of
> attached?
>
> >
Patches are also posted on bug report 29611.
https://sourceware.org/bugzilla/show_bug.cgi?id=29611
> >
> > On Sun, Sep 25, 2022 at 7:00 AM Noah Goldstein via Libc-alpha
> > <libc-alpha@sourceware.org> wrote:
> > >
> > > On Sun, Sep 25, 2022 at 1:19 AM Aurelien Jarno <aurelien@aurel32.net> wrote:
> > > >
> > > > On 2021-04-19 19:36, Noah Goldstein via Libc-alpha wrote:
> > > > > No bug. This commit optimizes strlen-avx2.S. The optimizations are
> > > > > mostly small things but they add up to roughly 10-30% performance
> > > > > improvement for strlen. The results for strnlen are bit more
> > > > > ambiguous. test-strlen, test-strnlen, test-wcslen, and test-wcsnlen
> > > > > are all passing.
> > > > >
> > > > > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > > > > ---
> > > > > sysdeps/x86_64/multiarch/ifunc-impl-list.c | 16 +-
> > > > > sysdeps/x86_64/multiarch/strlen-avx2.S | 532 +++++++++++++--------
> > > > > 2 files changed, 334 insertions(+), 214 deletions(-)
> > > > >
> > > > > diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > > > > index c377cab629..651b32908e 100644
> > > > > --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > > > > +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > > > > @@ -293,10 +293,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > > > > /* Support sysdeps/x86_64/multiarch/strlen.c. */
> > > > > IFUNC_IMPL (i, name, strlen,
> > > > > IFUNC_IMPL_ADD (array, i, strlen,
> > > > > - CPU_FEATURE_USABLE (AVX2),
> > > > > + (CPU_FEATURE_USABLE (AVX2)
> > > > > + && CPU_FEATURE_USABLE (BMI2)),
> > > > > __strlen_avx2)
> > > > > IFUNC_IMPL_ADD (array, i, strlen,
> > > > > (CPU_FEATURE_USABLE (AVX2)
> > > > > + && CPU_FEATURE_USABLE (BMI2)
> > > > > && CPU_FEATURE_USABLE (RTM)),
> > > > > __strlen_avx2_rtm)
> > > > > IFUNC_IMPL_ADD (array, i, strlen,
> > > > > @@ -309,10 +311,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > > > > /* Support sysdeps/x86_64/multiarch/strnlen.c. */
> > > > > IFUNC_IMPL (i, name, strnlen,
> > > > > IFUNC_IMPL_ADD (array, i, strnlen,
> > > > > - CPU_FEATURE_USABLE (AVX2),
> > > > > + (CPU_FEATURE_USABLE (AVX2)
> > > > > + && CPU_FEATURE_USABLE (BMI2)),
> > > > > __strnlen_avx2)
> > > > > IFUNC_IMPL_ADD (array, i, strnlen,
> > > > > (CPU_FEATURE_USABLE (AVX2)
> > > > > + && CPU_FEATURE_USABLE (BMI2)
> > > > > && CPU_FEATURE_USABLE (RTM)),
> > > > > __strnlen_avx2_rtm)
> > > > > IFUNC_IMPL_ADD (array, i, strnlen,
> > > > > @@ -654,10 +658,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > > > > /* Support sysdeps/x86_64/multiarch/wcslen.c. */
> > > > > IFUNC_IMPL (i, name, wcslen,
> > > > > IFUNC_IMPL_ADD (array, i, wcslen,
> > > > > - CPU_FEATURE_USABLE (AVX2),
> > > > > + (CPU_FEATURE_USABLE (AVX2)
> > > > > + && CPU_FEATURE_USABLE (BMI2)),
> > > > > __wcslen_avx2)
> > > > > IFUNC_IMPL_ADD (array, i, wcslen,
> > > > > (CPU_FEATURE_USABLE (AVX2)
> > > > > + && CPU_FEATURE_USABLE (BMI2)
> > > > > && CPU_FEATURE_USABLE (RTM)),
> > > > > __wcslen_avx2_rtm)
> > > > > IFUNC_IMPL_ADD (array, i, wcslen,
> > > > > @@ -670,10 +676,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> > > > > /* Support sysdeps/x86_64/multiarch/wcsnlen.c. */
> > > > > IFUNC_IMPL (i, name, wcsnlen,
> > > > > IFUNC_IMPL_ADD (array, i, wcsnlen,
> > > > > - CPU_FEATURE_USABLE (AVX2),
> > > > > + (CPU_FEATURE_USABLE (AVX2)
> > > > > + && CPU_FEATURE_USABLE (BMI2)),
> > > > > __wcsnlen_avx2)
> > > > > IFUNC_IMPL_ADD (array, i, wcsnlen,
> > > > > (CPU_FEATURE_USABLE (AVX2)
> > > > > + && CPU_FEATURE_USABLE (BMI2)
> > > > > && CPU_FEATURE_USABLE (RTM)),
> > > > > __wcsnlen_avx2_rtm)
> > > > > IFUNC_IMPL_ADD (array, i, wcsnlen,
> > > > > diff --git a/sysdeps/x86_64/multiarch/strlen-avx2.S b/sysdeps/x86_64/multiarch/strlen-avx2.S
> > > > > index 1caae9e6bc..bd2e6ee44a 100644
> > > > > --- a/sysdeps/x86_64/multiarch/strlen-avx2.S
> > > > > +++ b/sysdeps/x86_64/multiarch/strlen-avx2.S
> > > > > @@ -27,9 +27,11 @@
> > > > > # ifdef USE_AS_WCSLEN
> > > > > # define VPCMPEQ vpcmpeqd
> > > > > # define VPMINU vpminud
> > > > > +# define CHAR_SIZE 4
> > > > > # else
> > > > > # define VPCMPEQ vpcmpeqb
> > > > > # define VPMINU vpminub
> > > > > +# define CHAR_SIZE 1
> > > > > # endif
> > > > >
> > > > > # ifndef VZEROUPPER
> > > > > @@ -41,349 +43,459 @@
> > > > > # endif
> > > > >
> > > > > # define VEC_SIZE 32
> > > > > +# define PAGE_SIZE 4096
> > > > >
> > > > > .section SECTION(.text),"ax",@progbits
> > > > > ENTRY (STRLEN)
> > > > > # ifdef USE_AS_STRNLEN
> > > > > - /* Check for zero length. */
> > > > > + /* Check zero length. */
> > > > > test %RSI_LP, %RSI_LP
> > > > > jz L(zero)
> > > > > + /* Store max len in R8_LP before adjusting if using WCSLEN. */
> > > > > + mov %RSI_LP, %R8_LP
> > > > > # ifdef USE_AS_WCSLEN
> > > > > shl $2, %RSI_LP
> > > > > # elif defined __ILP32__
> > > > > /* Clear the upper 32 bits. */
> > > > > movl %esi, %esi
> > > > > # endif
> > > > > - mov %RSI_LP, %R8_LP
> > > > > # endif
> > > > > - movl %edi, %ecx
> > > > > + movl %edi, %eax
> > > > > movq %rdi, %rdx
> > > > > vpxor %xmm0, %xmm0, %xmm0
> > > > > -
> > > > > + /* Clear high bits from edi. Only keeping bits relevant to page
> > > > > + cross check. */
> > > > > + andl $(PAGE_SIZE - 1), %eax
> > > > > /* 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)
> > > > > + cmpl $(PAGE_SIZE - VEC_SIZE), %eax
> > > > > + ja L(cross_page_boundary)
> > > > >
> > > > > /* Check the first VEC_SIZE bytes. */
> > > > > - VPCMPEQ (%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > - testl %eax, %eax
> > > > > -
> > > > > + VPCMPEQ (%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > # ifdef USE_AS_STRNLEN
> > > > > - jnz L(first_vec_x0_check)
> > > > > - /* Adjust length and check the end of data. */
> > > > > - subq $VEC_SIZE, %rsi
> > > > > - jbe L(max)
> > > > > -# else
> > > > > - jnz L(first_vec_x0)
> > > > > + /* If length < VEC_SIZE handle special. */
> > > > > + cmpq $VEC_SIZE, %rsi
> > > > > + jbe L(first_vec_x0)
> > > > > # endif
> > > > > -
> > > > > - /* Align data for aligned loads in the loop. */
> > > > > - addq $VEC_SIZE, %rdi
> > > > > - andl $(VEC_SIZE - 1), %ecx
> > > > > - andq $-VEC_SIZE, %rdi
> > > > > + /* If empty continue to aligned_more. Otherwise return bit
> > > > > + position of first match. */
> > > > > + testl %eax, %eax
> > > > > + jz L(aligned_more)
> > > > > + tzcntl %eax, %eax
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > + shrl $2, %eax
> > > > > +# endif
> > > > > + VZEROUPPER_RETURN
> > > > >
> > > > > # ifdef USE_AS_STRNLEN
> > > > > - /* Adjust length. */
> > > > > - addq %rcx, %rsi
> > > > > +L(zero):
> > > > > + xorl %eax, %eax
> > > > > + ret
> > > > >
> > > > > - subq $(VEC_SIZE * 4), %rsi
> > > > > - jbe L(last_4x_vec_or_less)
> > > > > + .p2align 4
> > > > > +L(first_vec_x0):
> > > > > + /* Set bit for max len so that tzcnt will return min of max len
> > > > > + and position of first match. */
> > > > > + btsq %rsi, %rax
> > > > > + tzcntl %eax, %eax
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > + shrl $2, %eax
> > > > > +# endif
> > > > > + VZEROUPPER_RETURN
> > > > > # endif
> > > > > - jmp L(more_4x_vec)
> > > > >
> > > > > .p2align 4
> > > > > -L(cros_page_boundary):
> > > > > - andl $(VEC_SIZE - 1), %ecx
> > > > > - andq $-VEC_SIZE, %rdi
> > > > > - VPCMPEQ (%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > - /* Remove the leading bytes. */
> > > > > - sarl %cl, %eax
> > > > > - testl %eax, %eax
> > > > > - jz L(aligned_more)
> > > > > +L(first_vec_x1):
> > > > > tzcntl %eax, %eax
> > > > > + /* Safe to use 32 bit instructions as these are only called for
> > > > > + size = [1, 159]. */
> > > > > # ifdef USE_AS_STRNLEN
> > > > > - /* Check the end of data. */
> > > > > - cmpq %rax, %rsi
> > > > > - jbe L(max)
> > > > > + /* Use ecx which was computed earlier to compute correct value.
> > > > > + */
> > > > > + subl $(VEC_SIZE * 4 + 1), %ecx
> > > > > + addl %ecx, %eax
> > > > > +# else
> > > > > + subl %edx, %edi
> > > > > + incl %edi
> > > > > + addl %edi, %eax
> > > > > # endif
> > > > > - addq %rdi, %rax
> > > > > - addq %rcx, %rax
> > > > > - subq %rdx, %rax
> > > > > # ifdef USE_AS_WCSLEN
> > > > > - shrq $2, %rax
> > > > > + shrl $2, %eax
> > > > > # endif
> > > > > -L(return_vzeroupper):
> > > > > - ZERO_UPPER_VEC_REGISTERS_RETURN
> > > > > + VZEROUPPER_RETURN
> > > > >
> > > > > .p2align 4
> > > > > -L(aligned_more):
> > > > > +L(first_vec_x2):
> > > > > + tzcntl %eax, %eax
> > > > > + /* Safe to use 32 bit instructions as these are only called for
> > > > > + size = [1, 159]. */
> > > > > # ifdef USE_AS_STRNLEN
> > > > > - /* "rcx" is less than VEC_SIZE. 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
> > > > > -
> > > > > - /* Check the end of data. */
> > > > > - subq %rcx, %rsi
> > > > > - jbe L(max)
> > > > > + /* Use ecx which was computed earlier to compute correct value.
> > > > > + */
> > > > > + subl $(VEC_SIZE * 3 + 1), %ecx
> > > > > + addl %ecx, %eax
> > > > > +# else
> > > > > + subl %edx, %edi
> > > > > + addl $(VEC_SIZE + 1), %edi
> > > > > + addl %edi, %eax
> > > > > # endif
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > + shrl $2, %eax
> > > > > +# endif
> > > > > + VZEROUPPER_RETURN
> > > > >
> > > > > - addq $VEC_SIZE, %rdi
> > > > > + .p2align 4
> > > > > +L(first_vec_x3):
> > > > > + tzcntl %eax, %eax
> > > > > + /* Safe to use 32 bit instructions as these are only called for
> > > > > + size = [1, 159]. */
> > > > > +# ifdef USE_AS_STRNLEN
> > > > > + /* Use ecx which was computed earlier to compute correct value.
> > > > > + */
> > > > > + subl $(VEC_SIZE * 2 + 1), %ecx
> > > > > + addl %ecx, %eax
> > > > > +# else
> > > > > + subl %edx, %edi
> > > > > + addl $(VEC_SIZE * 2 + 1), %edi
> > > > > + addl %edi, %eax
> > > > > +# endif
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > + shrl $2, %eax
> > > > > +# endif
> > > > > + VZEROUPPER_RETURN
> > > > >
> > > > > + .p2align 4
> > > > > +L(first_vec_x4):
> > > > > + tzcntl %eax, %eax
> > > > > + /* Safe to use 32 bit instructions as these are only called for
> > > > > + size = [1, 159]. */
> > > > > # ifdef USE_AS_STRNLEN
> > > > > - subq $(VEC_SIZE * 4), %rsi
> > > > > - jbe L(last_4x_vec_or_less)
> > > > > + /* Use ecx which was computed earlier to compute correct value.
> > > > > + */
> > > > > + subl $(VEC_SIZE + 1), %ecx
> > > > > + addl %ecx, %eax
> > > > > +# else
> > > > > + subl %edx, %edi
> > > > > + addl $(VEC_SIZE * 3 + 1), %edi
> > > > > + addl %edi, %eax
> > > > > # endif
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > + shrl $2, %eax
> > > > > +# endif
> > > > > + VZEROUPPER_RETURN
> > > > >
> > > > > -L(more_4x_vec):
> > > > > + .p2align 5
> > > > > +L(aligned_more):
> > > > > + /* Align data to VEC_SIZE - 1. This is the same number of
> > > > > + instructions as using andq with -VEC_SIZE but saves 4 bytes of
> > > > > + code on the x4 check. */
> > > > > + orq $(VEC_SIZE - 1), %rdi
> > > > > +L(cross_page_continue):
> > > > > /* Check the first 4 * VEC_SIZE. Only one VEC_SIZE at a time
> > > > > since data is only aligned to VEC_SIZE. */
> > > > > - VPCMPEQ (%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > - testl %eax, %eax
> > > > > - jnz L(first_vec_x0)
> > > > > -
> > > > > - VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > +# ifdef USE_AS_STRNLEN
> > > > > + /* + 1 because rdi is aligned to VEC_SIZE - 1. + CHAR_SIZE because
> > > > > + it simplies the logic in last_4x_vec_or_less. */
> > > > > + leaq (VEC_SIZE * 4 + CHAR_SIZE + 1)(%rdi), %rcx
> > > > > + subq %rdx, %rcx
> > > > > +# endif
> > > > > + /* Load first VEC regardless. */
> > > > > + VPCMPEQ 1(%rdi), %ymm0, %ymm1
> > > > > +# ifdef USE_AS_STRNLEN
> > > > > + /* Adjust length. If near end handle specially. */
> > > > > + subq %rcx, %rsi
> > > > > + jb L(last_4x_vec_or_less)
> > > > > +# endif
> > > > > + vpmovmskb %ymm1, %eax
> > > > > testl %eax, %eax
> > > > > jnz L(first_vec_x1)
> > > > >
> > > > > - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > + VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > testl %eax, %eax
> > > > > jnz L(first_vec_x2)
> > > > >
> > > > > - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > + VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > testl %eax, %eax
> > > > > jnz L(first_vec_x3)
> > > > >
> > > > > - addq $(VEC_SIZE * 4), %rdi
> > > > > -
> > > > > -# ifdef USE_AS_STRNLEN
> > > > > - subq $(VEC_SIZE * 4), %rsi
> > > > > - jbe L(last_4x_vec_or_less)
> > > > > -# endif
> > > > > -
> > > > > - /* Align data to 4 * VEC_SIZE. */
> > > > > - movq %rdi, %rcx
> > > > > - andl $(4 * VEC_SIZE - 1), %ecx
> > > > > - andq $-(4 * VEC_SIZE), %rdi
> > > > > + VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > + testl %eax, %eax
> > > > > + jnz L(first_vec_x4)
> > > > >
> > > > > + /* Align data to VEC_SIZE * 4 - 1. */
> > > > > # ifdef USE_AS_STRNLEN
> > > > > - /* Adjust length. */
> > > > > + /* Before adjusting length check if at last VEC_SIZE * 4. */
> > > > > + cmpq $(VEC_SIZE * 4 - 1), %rsi
> > > > > + jbe L(last_4x_vec_or_less_load)
> > > > > + incq %rdi
> > > > > + movl %edi, %ecx
> > > > > + orq $(VEC_SIZE * 4 - 1), %rdi
> > > > > + andl $(VEC_SIZE * 4 - 1), %ecx
> > > > > + /* Readjust length. */
> > > > > addq %rcx, %rsi
> > > > > +# else
> > > > > + incq %rdi
> > > > > + orq $(VEC_SIZE * 4 - 1), %rdi
> > > > > # endif
> > > > > -
> > > > > + /* Compare 4 * VEC at a time forward. */
> > > > > .p2align 4
> > > > > L(loop_4x_vec):
> > > > > - /* Compare 4 * VEC at a time forward. */
> > > > > - vmovdqa (%rdi), %ymm1
> > > > > - vmovdqa VEC_SIZE(%rdi), %ymm2
> > > > > - vmovdqa (VEC_SIZE * 2)(%rdi), %ymm3
> > > > > - vmovdqa (VEC_SIZE * 3)(%rdi), %ymm4
> > > > > - VPMINU %ymm1, %ymm2, %ymm5
> > > > > - VPMINU %ymm3, %ymm4, %ymm6
> > > > > - VPMINU %ymm5, %ymm6, %ymm5
> > > > > -
> > > > > - VPCMPEQ %ymm5, %ymm0, %ymm5
> > > > > - vpmovmskb %ymm5, %eax
> > > > > - testl %eax, %eax
> > > > > - jnz L(4x_vec_end)
> > > > > -
> > > > > - addq $(VEC_SIZE * 4), %rdi
> > > > > -
> > > > > -# ifndef USE_AS_STRNLEN
> > > > > - jmp L(loop_4x_vec)
> > > > > -# else
> > > > > +# ifdef USE_AS_STRNLEN
> > > > > + /* Break if at end of length. */
> > > > > subq $(VEC_SIZE * 4), %rsi
> > > > > - ja L(loop_4x_vec)
> > > > > -
> > > > > -L(last_4x_vec_or_less):
> > > > > - /* Less than 4 * VEC and aligned to VEC_SIZE. */
> > > > > - addl $(VEC_SIZE * 2), %esi
> > > > > - jle L(last_2x_vec)
> > > > > + jb L(last_4x_vec_or_less_cmpeq)
> > > > > +# endif
> > > > > + /* Save some code size by microfusing VPMINU with the load. Since
> > > > > + the matches in ymm2/ymm4 can only be returned if there where no
> > > > > + matches in ymm1/ymm3 respectively there is no issue with overlap.
> > > > > + */
> > > > > + vmovdqa 1(%rdi), %ymm1
> > > > > + VPMINU (VEC_SIZE + 1)(%rdi), %ymm1, %ymm2
> > > > > + vmovdqa (VEC_SIZE * 2 + 1)(%rdi), %ymm3
> > > > > + VPMINU (VEC_SIZE * 3 + 1)(%rdi), %ymm3, %ymm4
> > > > > +
> > > > > + VPMINU %ymm2, %ymm4, %ymm5
> > > > > + VPCMPEQ %ymm5, %ymm0, %ymm5
> > > > > + vpmovmskb %ymm5, %ecx
> > > > >
> > > > > - VPCMPEQ (%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > - testl %eax, %eax
> > > > > - jnz L(first_vec_x0)
> > > > > + subq $-(VEC_SIZE * 4), %rdi
> > > > > + testl %ecx, %ecx
> > > > > + jz L(loop_4x_vec)
> > > > >
> > > > > - VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > - testl %eax, %eax
> > > > > - jnz L(first_vec_x1)
> > > > >
> > > > > - VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > + VPCMPEQ %ymm1, %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > + subq %rdx, %rdi
> > > > > testl %eax, %eax
> > > > > + jnz L(last_vec_return_x0)
> > > > >
> > > > > - jnz L(first_vec_x2_check)
> > > > > - subl $VEC_SIZE, %esi
> > > > > - jle L(max)
> > > > > -
> > > > > - VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > + VPCMPEQ %ymm2, %ymm0, %ymm2
> > > > > + vpmovmskb %ymm2, %eax
> > > > > testl %eax, %eax
> > > > > -
> > > > > - jnz L(first_vec_x3_check)
> > > > > - movq %r8, %rax
> > > > > -# ifdef USE_AS_WCSLEN
> > > > > + jnz L(last_vec_return_x1)
> > > > > +
> > > > > + /* Combine last 2 VEC. */
> > > > > + VPCMPEQ %ymm3, %ymm0, %ymm3
> > > > > + vpmovmskb %ymm3, %eax
> > > > > + /* rcx has combined result from all 4 VEC. It will only be used if
> > > > > + the first 3 other VEC all did not contain a match. */
> > > > > + salq $32, %rcx
> > > > > + orq %rcx, %rax
> > > > > + tzcntq %rax, %rax
> > > > > + subq $(VEC_SIZE * 2 - 1), %rdi
> > > > > + addq %rdi, %rax
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > -# endif
> > > > > +# endif
> > > > > VZEROUPPER_RETURN
> > > > >
> > > > > +
> > > > > +# ifdef USE_AS_STRNLEN
> > > > > .p2align 4
> > > > > -L(last_2x_vec):
> > > > > - addl $(VEC_SIZE * 2), %esi
> > > > > - VPCMPEQ (%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > - testl %eax, %eax
> > > > > +L(last_4x_vec_or_less_load):
> > > > > + /* Depending on entry adjust rdi / prepare first VEC in ymm1. */
> > > > > + subq $-(VEC_SIZE * 4), %rdi
> > > > > +L(last_4x_vec_or_less_cmpeq):
> > > > > + VPCMPEQ 1(%rdi), %ymm0, %ymm1
> > > > > +L(last_4x_vec_or_less):
> > > > >
> > > > > - jnz L(first_vec_x0_check)
> > > > > - subl $VEC_SIZE, %esi
> > > > > - jle L(max)
> > > > > + vpmovmskb %ymm1, %eax
> > > > > + /* If remaining length > VEC_SIZE * 2. This works if esi is off by
> > > > > + VEC_SIZE * 4. */
> > > > > + testl $(VEC_SIZE * 2), %esi
> > > > > + jnz L(last_4x_vec)
> > > > >
> > > > > - VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > + /* length may have been negative or positive by an offset of
> > > > > + VEC_SIZE * 4 depending on where this was called from. This fixes
> > > > > + that. */
> > > > > + andl $(VEC_SIZE * 4 - 1), %esi
> > > > > testl %eax, %eax
> > > > > - jnz L(first_vec_x1_check)
> > > > > - movq %r8, %rax
> > > > > -# ifdef USE_AS_WCSLEN
> > > > > - shrq $2, %rax
> > > > > -# endif
> > > > > - VZEROUPPER_RETURN
> > > > > + jnz L(last_vec_x1_check)
> > > > >
> > > > > - .p2align 4
> > > > > -L(first_vec_x0_check):
> > > > > + subl $VEC_SIZE, %esi
> > > > > + jb L(max)
> > > > > +
> > > > > + VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > tzcntl %eax, %eax
> > > > > /* Check the end of data. */
> > > > > - cmpq %rax, %rsi
> > > > > - jbe L(max)
> > > > > + cmpl %eax, %esi
> > > > > + jb L(max)
> > > > > + subq %rdx, %rdi
> > > > > + addl $(VEC_SIZE + 1), %eax
> > > > > addq %rdi, %rax
> > > > > - subq %rdx, %rax
> > > > > # ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > # endif
> > > > > VZEROUPPER_RETURN
> > > > > +# endif
> > > > >
> > > > > .p2align 4
> > > > > -L(first_vec_x1_check):
> > > > > +L(last_vec_return_x0):
> > > > > tzcntl %eax, %eax
> > > > > - /* Check the end of data. */
> > > > > - cmpq %rax, %rsi
> > > > > - jbe L(max)
> > > > > - addq $VEC_SIZE, %rax
> > > > > + subq $(VEC_SIZE * 4 - 1), %rdi
> > > > > addq %rdi, %rax
> > > > > - subq %rdx, %rax
> > > > > -# ifdef USE_AS_WCSLEN
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > -# endif
> > > > > +# endif
> > > > > VZEROUPPER_RETURN
> > > > >
> > > > > .p2align 4
> > > > > -L(first_vec_x2_check):
> > > > > +L(last_vec_return_x1):
> > > > > tzcntl %eax, %eax
> > > > > - /* Check the end of data. */
> > > > > - cmpq %rax, %rsi
> > > > > - jbe L(max)
> > > > > - addq $(VEC_SIZE * 2), %rax
> > > > > + subq $(VEC_SIZE * 3 - 1), %rdi
> > > > > addq %rdi, %rax
> > > > > - subq %rdx, %rax
> > > > > -# ifdef USE_AS_WCSLEN
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > -# endif
> > > > > +# endif
> > > > > VZEROUPPER_RETURN
> > > > >
> > > > > +# ifdef USE_AS_STRNLEN
> > > > > .p2align 4
> > > > > -L(first_vec_x3_check):
> > > > > +L(last_vec_x1_check):
> > > > > +
> > > > > tzcntl %eax, %eax
> > > > > /* Check the end of data. */
> > > > > - cmpq %rax, %rsi
> > > > > - jbe L(max)
> > > > > - addq $(VEC_SIZE * 3), %rax
> > > > > + cmpl %eax, %esi
> > > > > + jb L(max)
> > > > > + subq %rdx, %rdi
> > > > > + incl %eax
> > > > > addq %rdi, %rax
> > > > > - subq %rdx, %rax
> > > > > # ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > # endif
> > > > > VZEROUPPER_RETURN
> > > > >
> > > > > - .p2align 4
> > > > > L(max):
> > > > > movq %r8, %rax
> > > > > + VZEROUPPER_RETURN
> > > > > +
> > > > > + .p2align 4
> > > > > +L(last_4x_vec):
> > > > > + /* Test first 2x VEC normally. */
> > > > > + testl %eax, %eax
> > > > > + jnz L(last_vec_x1)
> > > > > +
> > > > > + VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > + testl %eax, %eax
> > > > > + jnz L(last_vec_x2)
> > > > > +
> > > > > + /* Normalize length. */
> > > > > + andl $(VEC_SIZE * 4 - 1), %esi
> > > > > + VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > + testl %eax, %eax
> > > > > + jnz L(last_vec_x3)
> > > > > +
> > > > > + subl $(VEC_SIZE * 3), %esi
> > > > > + jb L(max)
> > > > > +
> > > > > + VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > + tzcntl %eax, %eax
> > > > > + /* Check the end of data. */
> > > > > + cmpl %eax, %esi
> > > > > + jb L(max)
> > > > > + subq %rdx, %rdi
> > > > > + addl $(VEC_SIZE * 3 + 1), %eax
> > > > > + addq %rdi, %rax
> > > > > # ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > # endif
> > > > > VZEROUPPER_RETURN
> > > > >
> > > > > - .p2align 4
> > > > > -L(zero):
> > > > > - xorl %eax, %eax
> > > > > - ret
> > > > > -# endif
> > > > >
> > > > > .p2align 4
> > > > > -L(first_vec_x0):
> > > > > +L(last_vec_x1):
> > > > > + /* essentially duplicates of first_vec_x1 but use 64 bit
> > > > > + instructions. */
> > > > > tzcntl %eax, %eax
> > > > > + subq %rdx, %rdi
> > > > > + incl %eax
> > > > > addq %rdi, %rax
> > > > > - subq %rdx, %rax
> > > > > -# ifdef USE_AS_WCSLEN
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > -# endif
> > > > > +# endif
> > > > > VZEROUPPER_RETURN
> > > > >
> > > > > .p2align 4
> > > > > -L(first_vec_x1):
> > > > > +L(last_vec_x2):
> > > > > + /* essentially duplicates of first_vec_x1 but use 64 bit
> > > > > + instructions. */
> > > > > tzcntl %eax, %eax
> > > > > - addq $VEC_SIZE, %rax
> > > > > + subq %rdx, %rdi
> > > > > + addl $(VEC_SIZE + 1), %eax
> > > > > addq %rdi, %rax
> > > > > - subq %rdx, %rax
> > > > > -# ifdef USE_AS_WCSLEN
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > -# endif
> > > > > +# endif
> > > > > VZEROUPPER_RETURN
> > > > >
> > > > > .p2align 4
> > > > > -L(first_vec_x2):
> > > > > +L(last_vec_x3):
> > > > > tzcntl %eax, %eax
> > > > > - addq $(VEC_SIZE * 2), %rax
> > > > > + subl $(VEC_SIZE * 2), %esi
> > > > > + /* Check the end of data. */
> > > > > + cmpl %eax, %esi
> > > > > + jb L(max_end)
> > > > > + subq %rdx, %rdi
> > > > > + addl $(VEC_SIZE * 2 + 1), %eax
> > > > > addq %rdi, %rax
> > > > > - subq %rdx, %rax
> > > > > -# ifdef USE_AS_WCSLEN
> > > > > +# ifdef USE_AS_WCSLEN
> > > > > shrq $2, %rax
> > > > > -# endif
> > > > > +# endif
> > > > > + VZEROUPPER_RETURN
> > > > > +L(max_end):
> > > > > + movq %r8, %rax
> > > > > VZEROUPPER_RETURN
> > > > > +# endif
> > > > >
> > > > > + /* Cold case for crossing page with first load. */
> > > > > .p2align 4
> > > > > -L(4x_vec_end):
> > > > > - VPCMPEQ %ymm1, %ymm0, %ymm1
> > > > > - vpmovmskb %ymm1, %eax
> > > > > - testl %eax, %eax
> > > > > - jnz L(first_vec_x0)
> > > > > - VPCMPEQ %ymm2, %ymm0, %ymm2
> > > > > - vpmovmskb %ymm2, %eax
> > > > > +L(cross_page_boundary):
> > > > > + /* Align data to VEC_SIZE - 1. */
> > > > > + orq $(VEC_SIZE - 1), %rdi
> > > > > + VPCMPEQ -(VEC_SIZE - 1)(%rdi), %ymm0, %ymm1
> > > > > + vpmovmskb %ymm1, %eax
> > > > > + /* Remove the leading bytes. sarxl only uses bits [5:0] of COUNT
> > > > > + so no need to manually mod rdx. */
> > > > > + sarxl %edx, %eax, %eax
> > > >
> > > > This is a BMI2 instruction, which is not necessary available when AVX2
> > > > is available. This causes SIGILL on some CPU. I have reported that in
> > > > https://sourceware.org/bugzilla/show_bug.cgi?id=29611
> > >
> > > This is not a bug on master as:
> > >
> > > commit 83c5b368226c34a2f0a5287df40fc290b2b34359
> > > Author: H.J. Lu <hjl.tools@gmail.com>
> > > Date: Mon Apr 19 10:45:07 2021 -0700
> > >
> > > x86-64: Require BMI2 for strchr-avx2.S
> > >
> > > is already in tree. The issue is the avx2 changes where backported
> > > w.o H.J's changes.
> > > >
> > > > Regards
> > > > Aurelien
> > > >
> > > > --
> > > > Aurelien Jarno GPG: 4096R/1DDD8C9B
> > > > aurelien@aurel32.net http://www.aurel32.net
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