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From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Sunil Pandey <skpgkp2@gmail.com>
Cc: Libc-stable Mailing List <libc-stable@sourceware.org>,
	Hongjiu Lu <hjl.tools@gmail.com>,
	 GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH v5 2/2] x86: Optimize strlen-avx2.S
Date: Wed, 28 Sep 2022 07:42:28 -0700	[thread overview]
Message-ID: <CAFUsyfK+WPA9TdpTR25mXNDav+3s2saMOzwoJ-Hu6u6UH9XwbQ@mail.gmail.com> (raw)
In-Reply-To: <CAMAf5_eD8ABiFiKabV5xKkR-xLR7sK7Dx18z4VoawUUwkomf+g@mail.gmail.com>

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?

>
>
> 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

  parent reply	other threads:[~2022-09-28 14:42 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210419233607.916848-1-goldstein.w.n@gmail.com>
     [not found] ` <20210419233607.916848-2-goldstein.w.n@gmail.com>
     [not found]   ` <YzAO/ictPso/Y5LS@aurel32.net>
     [not found]     ` <CAFUsyf+U==grKgr9ZivEHDYsj=Xxi0MXBtQDfkU-JBHxb0pq+A@mail.gmail.com>
2022-09-28 13:54       ` Sunil Pandey
2022-09-28 14:02         ` Darren Tristano
2022-09-28 14:42         ` Noah Goldstein [this message]
2022-09-28 14:54           ` Sunil Pandey
2022-09-28 15:00             ` Noah Goldstein
2022-09-28 18:24               ` H.J. Lu
2022-09-30 13:19                 ` FUCKETY FUCK FUCK FUCK - PLEASE FUCKING REMOVE ME> Darren Tristano
2022-09-28 18:23         ` [PATCH v5 2/2] x86: Optimize strlen-avx2.S H.J. Lu
2022-09-28 19:09           ` Sunil Pandey
2022-09-28 19:23             ` H.J. Lu
2022-09-30 13:19           ` FUCKETY FUCK FUCK FUCK - PLEASE FUCKING REMOVE ME> Darren Tristano
2022-10-04 21:19         ` [PATCH v5 2/2] x86: Optimize strlen-avx2.S Aurelien Jarno
2022-10-04 21:29           ` H.J. Lu
2022-10-05  1:10           ` Sunil Pandey
2022-10-05 14:23             ` Noah Goldstein
2022-10-05 16:35               ` Sunil Pandey
2022-10-05 17:11             ` Aurelien Jarno
2022-10-05 18:34               ` Sunil Pandey

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