From: Noah Goldstein <goldstein.w.n@gmail.com>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: GNU C Library <libc-alpha@sourceware.org>,
"Carlos O'Donell" <carlos@systemhalted.org>
Subject: Re: [PATCH v1 03/23] x86: Code cleanup in strchr-avx2 and comment justifying branch
Date: Thu, 24 Mar 2022 14:20:16 -0500 [thread overview]
Message-ID: <CAFUsyfKfR3haCneczj0=ji+u3X_RsMNCXuOadytBrcaxgoEVTg@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOqQHH-20_czF-vtb_L_6MRBer=H9g3XpNBQLzcoSLZj+A@mail.gmail.com>
On Thu, Mar 24, 2022 at 1:53 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Wed, Mar 23, 2022 at 2:58 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > Small code cleanup for size: -53 bytes.
> >
> > Add comment justifying using a branch to do NULL/non-null return.
>
>
> Do you have followup patches to improve its performance? We are
> backporting all x86-64 improvements to Intel release branches:
>
> https://gitlab.com/x86-glibc/glibc/-/wikis/home
>
> Patches without performance improvements are undesirable.
No further changes planned at the moment, code size saves
seem worth it for master though. Also in favor of adding the comment
as I think its non-intuitive.
>
> > All string/memory tests pass and no regressions in benchtests.
> >
> > geometric_mean(N=20) of all benchmarks Original / New: 1.00
> > ---
> > Geomtric Mean N=20 runs; All functions page aligned
> > length, alignment, pos, rand, seek_char/branch, max_char/perc-zero, New Time / Old Time
> > 2048, 0, 32, 0, 23, 127, 1.033
> > 2048, 1, 32, 0, 23, 127, 1.006
> > 2048, 0, 64, 0, 23, 127, 1.02
> > 2048, 2, 64, 0, 23, 127, 0.992
> > 2048, 0, 128, 0, 23, 127, 0.996
> > 2048, 3, 128, 0, 23, 127, 0.966
> > 2048, 0, 256, 0, 23, 127, 0.996
> > 2048, 4, 256, 0, 23, 127, 0.998
> > 2048, 0, 512, 0, 23, 127, 0.991
> > 2048, 5, 512, 0, 23, 127, 0.991
> > 2048, 0, 1024, 0, 23, 127, 0.993
> > 2048, 6, 1024, 0, 23, 127, 0.992
> > 2048, 0, 2048, 0, 23, 127, 0.992
> > 2048, 7, 2048, 0, 23, 127, 0.976
> > 4096, 0, 32, 0, 23, 127, 0.983
> > 4096, 1, 32, 0, 23, 127, 0.994
> > 4096, 0, 64, 0, 23, 127, 0.968
> > 4096, 2, 64, 0, 23, 127, 1.018
> > 4096, 0, 128, 0, 23, 127, 0.99
> > 4096, 3, 128, 0, 23, 127, 1.001
> > 4096, 0, 256, 0, 23, 127, 1.0
> > 4096, 4, 256, 0, 23, 127, 1.001
> > 4096, 0, 512, 0, 23, 127, 0.989
> > 4096, 5, 512, 0, 23, 127, 0.988
> > 4096, 0, 1024, 0, 23, 127, 0.994
> > 4096, 6, 1024, 0, 23, 127, 0.993
> > 4096, 0, 2048, 0, 23, 127, 0.987
> > 4096, 7, 2048, 0, 23, 127, 0.996
> > 256, 1, 64, 0, 23, 127, 1.004
> > 256, 2, 64, 0, 23, 127, 1.004
> > 256, 3, 64, 0, 23, 127, 0.992
> > 256, 4, 64, 0, 23, 127, 1.001
> > 256, 5, 64, 0, 23, 127, 1.001
> > 256, 6, 64, 0, 23, 127, 0.998
> > 256, 7, 64, 0, 23, 127, 0.994
> > 512, 0, 256, 0, 23, 127, 0.999
> > 512, 16, 256, 0, 23, 127, 1.002
> > 512, 32, 256, 0, 23, 127, 0.994
> > 512, 48, 256, 0, 23, 127, 0.991
> > 512, 64, 256, 0, 23, 127, 0.994
> > 512, 80, 256, 0, 23, 127, 0.994
> > 512, 96, 256, 0, 23, 127, 0.996
> > 512, 112, 256, 0, 23, 127, 0.999
> > 1, 0, 0, 0, 23, 127, 0.978
> > 2, 0, 1, 0, 23, 127, 0.981
> > 3, 0, 2, 0, 23, 127, 0.993
> > 4, 0, 3, 0, 23, 127, 1.004
> > 5, 0, 4, 0, 23, 127, 1.002
> > 6, 0, 5, 0, 23, 127, 0.991
> > 7, 0, 6, 0, 23, 127, 0.99
> > 8, 0, 7, 0, 23, 127, 1.012
> > 9, 0, 8, 0, 23, 127, 0.994
> > 10, 0, 9, 0, 23, 127, 1.003
> > 11, 0, 10, 0, 23, 127, 0.999
> > 12, 0, 11, 0, 23, 127, 1.007
> > 13, 0, 12, 0, 23, 127, 1.0
> > 14, 0, 13, 0, 23, 127, 0.997
> > 15, 0, 14, 0, 23, 127, 0.996
> > 16, 0, 15, 0, 23, 127, 0.993
> > 17, 0, 16, 0, 23, 127, 1.002
> > 18, 0, 17, 0, 23, 127, 0.997
> > 19, 0, 18, 0, 23, 127, 0.998
> > 20, 0, 19, 0, 23, 127, 0.994
> > 21, 0, 20, 0, 23, 127, 0.99
> > 22, 0, 21, 0, 23, 127, 0.992
> > 23, 0, 22, 0, 23, 127, 0.996
> > 24, 0, 23, 0, 23, 127, 0.991
> > 25, 0, 24, 0, 23, 127, 0.997
> > 26, 0, 25, 0, 23, 127, 1.011
> > 27, 0, 26, 0, 23, 127, 1.013
> > 28, 0, 27, 0, 23, 127, 0.996
> > 29, 0, 28, 0, 23, 127, 0.993
> > 30, 0, 29, 0, 23, 127, 1.009
> > 31, 0, 30, 0, 23, 127, 1.009
> > 32, 0, 31, 0, 23, 127, 1.008
> > 2048, 0, 32, 0, 0, 127, 1.0
> > 2048, 1, 32, 0, 0, 127, 1.01
> > 2048, 0, 64, 0, 0, 127, 0.997
> > 2048, 2, 64, 0, 0, 127, 1.002
> > 2048, 0, 128, 0, 0, 127, 0.986
> > 2048, 3, 128, 0, 0, 127, 0.997
> > 2048, 0, 256, 0, 0, 127, 1.002
> > 2048, 4, 256, 0, 0, 127, 0.999
> > 2048, 0, 512, 0, 0, 127, 0.991
> > 2048, 5, 512, 0, 0, 127, 0.984
> > 2048, 0, 1024, 0, 0, 127, 0.994
> > 2048, 6, 1024, 0, 0, 127, 0.993
> > 2048, 0, 2048, 0, 0, 127, 0.951
> > 2048, 7, 2048, 0, 0, 127, 0.989
> > 4096, 0, 32, 0, 0, 127, 0.993
> > 4096, 1, 32, 0, 0, 127, 0.997
> > 4096, 0, 64, 0, 0, 127, 1.004
> > 4096, 2, 64, 0, 0, 127, 1.016
> > 4096, 0, 128, 0, 0, 127, 0.973
> > 4096, 3, 128, 0, 0, 127, 1.001
> > 4096, 0, 256, 0, 0, 127, 0.999
> > 4096, 4, 256, 0, 0, 127, 0.998
> > 4096, 0, 512, 0, 0, 127, 0.99
> > 4096, 5, 512, 0, 0, 127, 0.985
> > 4096, 0, 1024, 0, 0, 127, 0.993
> > 4096, 6, 1024, 0, 0, 127, 0.997
> > 4096, 0, 2048, 0, 0, 127, 0.995
> > 4096, 7, 2048, 0, 0, 127, 0.996
> > 256, 1, 64, 0, 0, 127, 1.01
> > 256, 2, 64, 0, 0, 127, 1.024
> > 256, 3, 64, 0, 0, 127, 1.03
> > 256, 4, 64, 0, 0, 127, 1.004
> > 256, 5, 64, 0, 0, 127, 0.998
> > 256, 6, 64, 0, 0, 127, 0.998
> > 256, 7, 64, 0, 0, 127, 0.997
> > 512, 0, 256, 0, 0, 127, 0.996
> > 512, 16, 256, 0, 0, 127, 0.995
> > 512, 32, 256, 0, 0, 127, 0.996
> > 512, 48, 256, 0, 0, 127, 0.992
> > 512, 64, 256, 0, 0, 127, 0.999
> > 512, 80, 256, 0, 0, 127, 1.002
> > 512, 96, 256, 0, 0, 127, 0.999
> > 512, 112, 256, 0, 0, 127, 0.998
> > 1, 0, 0, 0, 0, 127, 1.016
> > 2, 0, 1, 0, 0, 127, 0.998
> > 3, 0, 2, 0, 0, 127, 1.02
> > 4, 0, 3, 0, 0, 127, 1.004
> > 5, 0, 4, 0, 0, 127, 1.021
> > 6, 0, 5, 0, 0, 127, 1.014
> > 7, 0, 6, 0, 0, 127, 1.007
> > 8, 0, 7, 0, 0, 127, 1.016
> > 9, 0, 8, 0, 0, 127, 1.003
> > 10, 0, 9, 0, 0, 127, 1.004
> > 11, 0, 10, 0, 0, 127, 0.995
> > 12, 0, 11, 0, 0, 127, 1.009
> > 13, 0, 12, 0, 0, 127, 1.005
> > 14, 0, 13, 0, 0, 127, 0.987
> > 15, 0, 14, 0, 0, 127, 0.998
> > 16, 0, 15, 0, 0, 127, 1.004
> > 17, 0, 16, 0, 0, 127, 1.01
> > 18, 0, 17, 0, 0, 127, 1.01
> > 19, 0, 18, 0, 0, 127, 1.006
> > 20, 0, 19, 0, 0, 127, 1.012
> > 21, 0, 20, 0, 0, 127, 0.999
> > 22, 0, 21, 0, 0, 127, 1.004
> > 23, 0, 22, 0, 0, 127, 0.988
> > 24, 0, 23, 0, 0, 127, 0.993
> > 25, 0, 24, 0, 0, 127, 1.004
> > 26, 0, 25, 0, 0, 127, 0.99
> > 27, 0, 26, 0, 0, 127, 1.016
> > 28, 0, 27, 0, 0, 127, 0.987
> > 29, 0, 28, 0, 0, 127, 0.989
> > 30, 0, 29, 0, 0, 127, 0.998
> > 31, 0, 30, 0, 0, 127, 1.005
> > 32, 0, 31, 0, 0, 127, 0.993
> >
> > 16, 0, 15, 1, 1, 0, 1.002
> > 16, 0, 15, 1, 0, 0, 1.0
> > 16, 0, 15, 1, 1, 0.1, 1.034
> > 16, 0, 15, 1, 0, 0.1, 1.03
> > 16, 0, 15, 1, 1, 0.25, 0.993
> > 16, 0, 15, 1, 0, 0.25, 1.081
> > 16, 0, 15, 1, 1, 0.33, 0.959
> > 16, 0, 15, 1, 0, 0.33, 1.142
> > 16, 0, 15, 1, 1, 0.5, 0.929
> > 16, 0, 15, 1, 0, 0.5, 1.072
> > 16, 0, 15, 1, 1, 0.66, 0.984
> > 16, 0, 15, 1, 0, 0.66, 1.069
> > 16, 0, 15, 1, 1, 0.75, 0.969
> > 16, 0, 15, 1, 0, 0.75, 1.059
> > 16, 0, 15, 1, 1, 0.9, 0.98
> > 16, 0, 15, 1, 0, 0.9, 0.994
> > 16, 0, 15, 1, 1, 1, 0.993
> > 16, 0, 15, 1, 0, 1, 0.996
> >
> > sysdeps/x86_64/multiarch/strchr-avx2.S | 204 +++++++++++++------------
> > 1 file changed, 107 insertions(+), 97 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/strchr-avx2.S b/sysdeps/x86_64/multiarch/strchr-avx2.S
> > index 086cabf76a..1a916cc951 100644
> > --- a/sysdeps/x86_64/multiarch/strchr-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/strchr-avx2.S
> > @@ -48,13 +48,13 @@
> > # define PAGE_SIZE 4096
> >
> > .section SECTION(.text),"ax",@progbits
> > -ENTRY (STRCHR)
> > +ENTRY_P2ALIGN (STRCHR, 5)
> > /* Broadcast CHAR to YMM0. */
> > vmovd %esi, %xmm0
> > movl %edi, %eax
> > andl $(PAGE_SIZE - 1), %eax
> > VPBROADCAST %xmm0, %ymm0
> > - vpxor %xmm9, %xmm9, %xmm9
> > + vpxor %xmm1, %xmm1, %xmm1
> >
> > /* Check if we cross page boundary with one vector load. */
> > cmpl $(PAGE_SIZE - VEC_SIZE), %eax
> > @@ -62,37 +62,29 @@ ENTRY (STRCHR)
> >
> > /* Check the first VEC_SIZE bytes. Search for both CHAR and the
> > null byte. */
> > - vmovdqu (%rdi), %ymm8
> > - VPCMPEQ %ymm8, %ymm0, %ymm1
> > - VPCMPEQ %ymm8, %ymm9, %ymm2
> > - vpor %ymm1, %ymm2, %ymm1
> > - vpmovmskb %ymm1, %eax
> > + vmovdqu (%rdi), %ymm2
> > + VPCMPEQ %ymm2, %ymm0, %ymm3
> > + VPCMPEQ %ymm2, %ymm1, %ymm2
> > + vpor %ymm3, %ymm2, %ymm3
> > + vpmovmskb %ymm3, %eax
> > testl %eax, %eax
> > jz L(aligned_more)
> > tzcntl %eax, %eax
> > # ifndef USE_AS_STRCHRNUL
> > - /* Found CHAR or the null byte. */
> > - cmp (%rdi, %rax), %CHAR_REG
> > - jne L(zero)
> > -# endif
> > - addq %rdi, %rax
> > - VZEROUPPER_RETURN
> > -
> > - /* .p2align 5 helps keep performance more consistent if ENTRY()
> > - alignment % 32 was either 16 or 0. As well this makes the
> > - alignment % 32 of the loop_4x_vec fixed which makes tuning it
> > - easier. */
> > - .p2align 5
> > -L(first_vec_x4):
> > - tzcntl %eax, %eax
> > - addq $(VEC_SIZE * 3 + 1), %rdi
> > -# ifndef USE_AS_STRCHRNUL
> > - /* Found CHAR or the null byte. */
> > + /* Found CHAR or the null byte. */
> > cmp (%rdi, %rax), %CHAR_REG
> > + /* NB: Use a branch instead of cmovcc here. The expectation is
> > + that with strchr the user will branch based on input being
> > + null. Since this branch will be 100% predictive of the user
> > + branch a branch miss here should save what otherwise would
> > + be branch miss in the user code. Otherwise using a branch 1)
> > + saves code size and 2) is faster in highly predictable
> > + environments. */
> > jne L(zero)
> > # endif
> > addq %rdi, %rax
> > - VZEROUPPER_RETURN
> > +L(return_vzeroupper):
> > + ZERO_UPPER_VEC_REGISTERS_RETURN
> >
> > # ifndef USE_AS_STRCHRNUL
> > L(zero):
> > @@ -103,7 +95,8 @@ L(zero):
> >
> > .p2align 4
> > L(first_vec_x1):
> > - tzcntl %eax, %eax
> > + /* Use bsf to save code size. */
> > + bsfl %eax, %eax
> > incq %rdi
> > # ifndef USE_AS_STRCHRNUL
> > /* Found CHAR or the null byte. */
> > @@ -113,9 +106,10 @@ L(first_vec_x1):
> > addq %rdi, %rax
> > VZEROUPPER_RETURN
> >
> > - .p2align 4
> > + .p2align 4,, 10
> > L(first_vec_x2):
> > - tzcntl %eax, %eax
> > + /* Use bsf to save code size. */
> > + bsfl %eax, %eax
> > addq $(VEC_SIZE + 1), %rdi
> > # ifndef USE_AS_STRCHRNUL
> > /* Found CHAR or the null byte. */
> > @@ -125,9 +119,10 @@ L(first_vec_x2):
> > addq %rdi, %rax
> > VZEROUPPER_RETURN
> >
> > - .p2align 4
> > + .p2align 4,, 8
> > L(first_vec_x3):
> > - tzcntl %eax, %eax
> > + /* Use bsf to save code size. */
> > + bsfl %eax, %eax
> > addq $(VEC_SIZE * 2 + 1), %rdi
> > # ifndef USE_AS_STRCHRNUL
> > /* Found CHAR or the null byte. */
> > @@ -137,6 +132,21 @@ L(first_vec_x3):
> > addq %rdi, %rax
> > VZEROUPPER_RETURN
> >
> > + .p2align 4,, 10
> > +L(first_vec_x4):
> > + /* Use bsf to save code size. */
> > + bsfl %eax, %eax
> > + addq $(VEC_SIZE * 3 + 1), %rdi
> > +# ifndef USE_AS_STRCHRNUL
> > + /* Found CHAR or the null byte. */
> > + cmp (%rdi, %rax), %CHAR_REG
> > + jne L(zero)
> > +# endif
> > + addq %rdi, %rax
> > + VZEROUPPER_RETURN
> > +
> > +
> > +
> > .p2align 4
> > L(aligned_more):
> > /* Align data to VEC_SIZE - 1. This is the same number of
> > @@ -146,90 +156,92 @@ L(aligned_more):
> > L(cross_page_continue):
> > /* Check the next 4 * VEC_SIZE. Only one VEC_SIZE at a time
> > since data is only aligned to VEC_SIZE. */
> > - vmovdqa 1(%rdi), %ymm8
> > - VPCMPEQ %ymm8, %ymm0, %ymm1
> > - VPCMPEQ %ymm8, %ymm9, %ymm2
> > - vpor %ymm1, %ymm2, %ymm1
> > - vpmovmskb %ymm1, %eax
> > + vmovdqa 1(%rdi), %ymm2
> > + VPCMPEQ %ymm2, %ymm0, %ymm3
> > + VPCMPEQ %ymm2, %ymm1, %ymm2
> > + vpor %ymm3, %ymm2, %ymm3
> > + vpmovmskb %ymm3, %eax
> > testl %eax, %eax
> > jnz L(first_vec_x1)
> >
> > - vmovdqa (VEC_SIZE + 1)(%rdi), %ymm8
> > - VPCMPEQ %ymm8, %ymm0, %ymm1
> > - VPCMPEQ %ymm8, %ymm9, %ymm2
> > - vpor %ymm1, %ymm2, %ymm1
> > - vpmovmskb %ymm1, %eax
> > + vmovdqa (VEC_SIZE + 1)(%rdi), %ymm2
> > + VPCMPEQ %ymm2, %ymm0, %ymm3
> > + VPCMPEQ %ymm2, %ymm1, %ymm2
> > + vpor %ymm3, %ymm2, %ymm3
> > + vpmovmskb %ymm3, %eax
> > testl %eax, %eax
> > jnz L(first_vec_x2)
> >
> > - vmovdqa (VEC_SIZE * 2 + 1)(%rdi), %ymm8
> > - VPCMPEQ %ymm8, %ymm0, %ymm1
> > - VPCMPEQ %ymm8, %ymm9, %ymm2
> > - vpor %ymm1, %ymm2, %ymm1
> > - vpmovmskb %ymm1, %eax
> > + vmovdqa (VEC_SIZE * 2 + 1)(%rdi), %ymm2
> > + VPCMPEQ %ymm2, %ymm0, %ymm3
> > + VPCMPEQ %ymm2, %ymm1, %ymm2
> > + vpor %ymm3, %ymm2, %ymm3
> > + vpmovmskb %ymm3, %eax
> > testl %eax, %eax
> > jnz L(first_vec_x3)
> >
> > - vmovdqa (VEC_SIZE * 3 + 1)(%rdi), %ymm8
> > - VPCMPEQ %ymm8, %ymm0, %ymm1
> > - VPCMPEQ %ymm8, %ymm9, %ymm2
> > - vpor %ymm1, %ymm2, %ymm1
> > - vpmovmskb %ymm1, %eax
> > + vmovdqa (VEC_SIZE * 3 + 1)(%rdi), %ymm2
> > + VPCMPEQ %ymm2, %ymm0, %ymm3
> > + VPCMPEQ %ymm2, %ymm1, %ymm2
> > + vpor %ymm3, %ymm2, %ymm3
> > + vpmovmskb %ymm3, %eax
> > testl %eax, %eax
> > jnz L(first_vec_x4)
> > - /* Align data to VEC_SIZE * 4 - 1. */
> > - addq $(VEC_SIZE * 4 + 1), %rdi
> > - andq $-(VEC_SIZE * 4), %rdi
> > + /* Align data to VEC_SIZE * 4 - 1. */
> > + incq %rdi
> > + orq $(VEC_SIZE * 4 - 1), %rdi
> > .p2align 4
> > L(loop_4x_vec):
> > /* Compare 4 * VEC at a time forward. */
> > - vmovdqa (%rdi), %ymm5
> > - vmovdqa (VEC_SIZE)(%rdi), %ymm6
> > - vmovdqa (VEC_SIZE * 2)(%rdi), %ymm7
> > - vmovdqa (VEC_SIZE * 3)(%rdi), %ymm8
> > + vmovdqa 1(%rdi), %ymm6
> > + vmovdqa (VEC_SIZE + 1)(%rdi), %ymm7
> >
> > /* Leaves only CHARS matching esi as 0. */
> > - vpxor %ymm5, %ymm0, %ymm1
> > vpxor %ymm6, %ymm0, %ymm2
> > vpxor %ymm7, %ymm0, %ymm3
> > - vpxor %ymm8, %ymm0, %ymm4
> >
> > - VPMINU %ymm1, %ymm5, %ymm1
> > VPMINU %ymm2, %ymm6, %ymm2
> > VPMINU %ymm3, %ymm7, %ymm3
> > - VPMINU %ymm4, %ymm8, %ymm4
> >
> > - VPMINU %ymm1, %ymm2, %ymm5
> > - VPMINU %ymm3, %ymm4, %ymm6
> > + vmovdqa (VEC_SIZE * 2 + 1)(%rdi), %ymm6
> > + vmovdqa (VEC_SIZE * 3 + 1)(%rdi), %ymm7
> > +
> > + vpxor %ymm6, %ymm0, %ymm4
> > + vpxor %ymm7, %ymm0, %ymm5
> > +
> > + VPMINU %ymm4, %ymm6, %ymm4
> > + VPMINU %ymm5, %ymm7, %ymm5
> >
> > - VPMINU %ymm5, %ymm6, %ymm6
> > + VPMINU %ymm2, %ymm3, %ymm6
> > + VPMINU %ymm4, %ymm5, %ymm7
> >
> > - VPCMPEQ %ymm6, %ymm9, %ymm6
> > - vpmovmskb %ymm6, %ecx
> > + VPMINU %ymm6, %ymm7, %ymm7
> > +
> > + VPCMPEQ %ymm7, %ymm1, %ymm7
> > + vpmovmskb %ymm7, %ecx
> > subq $-(VEC_SIZE * 4), %rdi
> > testl %ecx, %ecx
> > jz L(loop_4x_vec)
> >
> > -
> > - VPCMPEQ %ymm1, %ymm9, %ymm1
> > - vpmovmskb %ymm1, %eax
> > + VPCMPEQ %ymm2, %ymm1, %ymm2
> > + vpmovmskb %ymm2, %eax
> > testl %eax, %eax
> > jnz L(last_vec_x0)
> >
> >
> > - VPCMPEQ %ymm5, %ymm9, %ymm2
> > - vpmovmskb %ymm2, %eax
> > + VPCMPEQ %ymm3, %ymm1, %ymm3
> > + vpmovmskb %ymm3, %eax
> > testl %eax, %eax
> > jnz L(last_vec_x1)
> >
> > - VPCMPEQ %ymm3, %ymm9, %ymm3
> > - vpmovmskb %ymm3, %eax
> > + VPCMPEQ %ymm4, %ymm1, %ymm4
> > + vpmovmskb %ymm4, %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), %rdi
> > + subq $(VEC_SIZE * 2 - 1), %rdi
> > # ifndef USE_AS_STRCHRNUL
> > /* Found CHAR or the null byte. */
> > cmp (%rdi, %rax), %CHAR_REG
> > @@ -239,10 +251,11 @@ L(loop_4x_vec):
> > VZEROUPPER_RETURN
> >
> >
> > - .p2align 4
> > + .p2align 4,, 10
> > L(last_vec_x0):
> > - tzcntl %eax, %eax
> > - addq $-(VEC_SIZE * 4), %rdi
> > + /* Use bsf to save code size. */
> > + bsfl %eax, %eax
> > + addq $-(VEC_SIZE * 4 - 1), %rdi
> > # ifndef USE_AS_STRCHRNUL
> > /* Found CHAR or the null byte. */
> > cmp (%rdi, %rax), %CHAR_REG
> > @@ -251,16 +264,11 @@ L(last_vec_x0):
> > addq %rdi, %rax
> > VZEROUPPER_RETURN
> >
> > -# ifndef USE_AS_STRCHRNUL
> > -L(zero_end):
> > - xorl %eax, %eax
> > - VZEROUPPER_RETURN
> > -# endif
> >
> > - .p2align 4
> > + .p2align 4,, 10
> > L(last_vec_x1):
> > tzcntl %eax, %eax
> > - subq $(VEC_SIZE * 3), %rdi
> > + subq $(VEC_SIZE * 3 - 1), %rdi
> > # ifndef USE_AS_STRCHRNUL
> > /* Found CHAR or the null byte. */
> > cmp (%rdi, %rax), %CHAR_REG
> > @@ -269,18 +277,23 @@ L(last_vec_x1):
> > addq %rdi, %rax
> > VZEROUPPER_RETURN
> >
> > +# ifndef USE_AS_STRCHRNUL
> > +L(zero_end):
> > + xorl %eax, %eax
> > + VZEROUPPER_RETURN
> > +# endif
> >
> > /* Cold case for crossing page with first load. */
> > - .p2align 4
> > + .p2align 4,, 8
> > L(cross_page_boundary):
> > movq %rdi, %rdx
> > /* Align rdi to VEC_SIZE - 1. */
> > orq $(VEC_SIZE - 1), %rdi
> > - vmovdqa -(VEC_SIZE - 1)(%rdi), %ymm8
> > - VPCMPEQ %ymm8, %ymm0, %ymm1
> > - VPCMPEQ %ymm8, %ymm9, %ymm2
> > - vpor %ymm1, %ymm2, %ymm1
> > - vpmovmskb %ymm1, %eax
> > + vmovdqa -(VEC_SIZE - 1)(%rdi), %ymm2
> > + VPCMPEQ %ymm2, %ymm0, %ymm3
> > + VPCMPEQ %ymm2, %ymm1, %ymm2
> > + vpor %ymm3, %ymm2, %ymm3
> > + vpmovmskb %ymm3, %eax
> > /* Remove the leading bytes. sarxl only uses bits [5:0] of COUNT
> > so no need to manually mod edx. */
> > sarxl %edx, %eax, %eax
> > @@ -291,13 +304,10 @@ L(cross_page_boundary):
> > xorl %ecx, %ecx
> > /* Found CHAR or the null byte. */
> > cmp (%rdx, %rax), %CHAR_REG
> > - leaq (%rdx, %rax), %rax
> > - cmovne %rcx, %rax
> > -# else
> > - addq %rdx, %rax
> > + jne L(zero_end)
> > # endif
> > -L(return_vzeroupper):
> > - ZERO_UPPER_VEC_REGISTERS_RETURN
> > + addq %rdx, %rax
> > + VZEROUPPER_RETURN
> >
> > END (STRCHR)
> > -# endif
> > +#endif
> > --
> > 2.25.1
> >
>
>
> --
> H.J.
next prev parent reply other threads:[~2022-03-24 19:20 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 21:57 [PATCH v1 01/23] benchtests: Use json-lib in bench-strchr.c Noah Goldstein
2022-03-23 21:57 ` [PATCH v1 02/23] benchtests: Add random benchmark " Noah Goldstein
2022-03-24 18:44 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 03/23] x86: Code cleanup in strchr-avx2 and comment justifying branch Noah Goldstein
2022-03-24 18:53 ` H.J. Lu
2022-03-24 19:20 ` Noah Goldstein [this message]
2022-03-24 19:36 ` H.J. Lu
2022-05-12 19:31 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 04/23] x86: Code cleanup in strchr-evex " Noah Goldstein
2022-03-24 18:54 ` H.J. Lu
2022-05-12 19:32 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 05/23] benchtests: Use json-lib in bench-strpbrk.c Noah Goldstein
2022-03-24 18:54 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 06/23] benchtests: Use json-lib in bench-strspn.c Noah Goldstein
2022-03-24 18:54 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 07/23] x86: Optimize strcspn and strpbrk in strcspn-c.c Noah Goldstein
2022-03-24 18:55 ` H.J. Lu
2022-05-12 19:34 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 08/23] x86: Optimize strspn in strspn-c.c Noah Goldstein
2022-03-24 18:56 ` H.J. Lu
2022-05-12 19:39 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 09/23] x86: Remove strcspn-sse2.S and use the generic implementation Noah Goldstein
2022-03-24 18:57 ` H.J. Lu
2022-05-12 19:40 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 10/23] x86: Remove strpbrk-sse2.S " Noah Goldstein
2022-03-24 18:57 ` H.J. Lu
2022-05-12 19:41 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 11/23] x86: Remove strspn-sse2.S " Noah Goldstein
2022-03-24 18:57 ` H.J. Lu
2022-05-12 19:42 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 12/23] x86: Fix fallback for wcsncmp_avx2 in strcmp-avx2.S [BZ #28896] Noah Goldstein
2022-03-24 18:59 ` H.J. Lu
2022-03-24 19:18 ` Noah Goldstein
2022-03-24 19:34 ` H.J. Lu
2022-03-24 19:39 ` Noah Goldstein
2022-03-24 20:50 ` [PATCH v2 12/31] " Noah Goldstein
2022-03-24 21:26 ` H.J. Lu
2022-03-24 21:43 ` Noah Goldstein
2022-03-24 21:58 ` H.J. Lu
2022-05-04 6:05 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 13/23] benchtests: Use json-lib in bench-strcasecmp.c Noah Goldstein
2022-03-24 19:00 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 14/23] benchtests: Use json-lib in bench-strncasecmp.c Noah Goldstein
2022-03-24 19:00 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 15/23] string: Expand page cross tests in test-strcasecmp.c Noah Goldstein
2022-03-24 19:01 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 16/23] string: Expand page cross tests in test-strncasecmp.c Noah Goldstein
2022-03-24 19:01 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 17/23] x86: Optimize str{n}casecmp TOLOWER logic in strcmp.S Noah Goldstein
2022-03-24 19:02 ` H.J. Lu
2022-05-12 19:44 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 18/23] x86: Optimize str{n}casecmp TOLOWER logic in strcmp-sse42.S Noah Goldstein
2022-03-24 19:02 ` H.J. Lu
2022-05-12 19:45 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 19/23] string: Expand page cross test cases in test-strcmp.c Noah Goldstein
2022-03-24 19:02 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 20/23] string: Expand page cross test cases in test-strncmp.c Noah Goldstein
2022-03-24 19:02 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 21/23] x86: Add AVX2 optimized str{n}casecmp Noah Goldstein
2022-03-24 19:03 ` H.J. Lu
2022-03-24 22:41 ` [PATCH v3 " Noah Goldstein
2022-03-24 22:41 ` [PATCH v3 22/23] x86: Add EVEX " Noah Goldstein
2022-03-24 23:56 ` [PATCH v4 21/23] x86: Add AVX2 " Noah Goldstein
2022-03-24 23:56 ` [PATCH v4 22/23] x86: Add EVEX " Noah Goldstein
2022-03-25 18:15 ` H.J. Lu
2022-03-25 18:18 ` Noah Goldstein
2022-05-12 19:47 ` Sunil Pandey
2022-05-12 19:52 ` Sunil Pandey
2022-03-25 18:14 ` [PATCH v4 21/23] x86: Add AVX2 " H.J. Lu
2022-05-12 19:52 ` Sunil Pandey
2022-03-23 21:57 ` [PATCH v1 22/23] x86: Add EVEX " Noah Goldstein
2022-03-24 19:04 ` H.J. Lu
2022-03-23 21:57 ` [PATCH v1 23/23] x86: Remove AVX str{n}casecmp Noah Goldstein
2022-03-24 19:04 ` H.J. Lu
2022-05-12 19:54 ` Sunil Pandey
2022-03-24 18:43 ` [PATCH v1 01/23] benchtests: Use json-lib in bench-strchr.c H.J. Lu
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