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 v4 2/2] x86: Optimize strlen-avx2.S
Date: Mon, 19 Apr 2021 19:39:22 -0400 [thread overview]
Message-ID: <CAFUsyfLBiy9jcD3h4FMBk6ocHDM5jcezVWig7-ufpkN_JOw=Gw@mail.gmail.com> (raw)
In-Reply-To: <YH4BJ1XOcAQZJiaU@gmail.com>
On Mon, Apr 19, 2021 at 6:16 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Mon, Apr 19, 2021 at 02:43:45PM -0400, Noah Goldstein 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 | 535 +++++++++++++--------
> > 2 files changed, 337 insertions(+), 214 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > index 0b0927b124..4613bead7c 100644
> > --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > @@ -285,10 +285,12 @@ __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,
> > @@ -301,10 +303,12 @@ __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,
> > @@ -646,10 +650,12 @@ __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,
> > @@ -662,10 +668,12 @@ __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..eb92f587b4 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 +43,462 @@
> > # endif
> >
> > # define VEC_SIZE 32
> > +# define PAGE_SIZE 4096
> > +# define LOG_PAGE_SIZE 12
> >
> > .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
> > -
> > + /* Shift left eax to clear all bits not relevant to page cross
> > + check. This saves 2 bytes of code as opposed to using andl with
> > + PAGE_SIZE - 1. Then compare with PAGE_SIZE - VEC_SIZE shifted
> > + left by the same amount (an imm32 either way). */
> > + sall $(32 - LOG_PAGE_SIZE), %eax
>
> I prefer AND over SAL for better throughput.
Done.
>
> H.J.
> > /* 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) << (32 - LOG_PAGE_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
> > +# ifdef USE_AS_STRNLEN
> > testl %eax, %eax
> > - jnz L(first_vec_x1)
> > - VPCMPEQ %ymm3, %ymm0, %ymm3
> > - vpmovmskb %ymm3, %eax
> > + jnz L(cross_page_less_vec)
> > + leaq 1(%rdi), %rcx
> > + subq %rdx, %rcx
> > + /* Check length. */
> > + cmpq %rsi, %rcx
> > + jb L(cross_page_continue)
> > + movq %r8, %rax
> > +# else
> > testl %eax, %eax
> > - jnz L(first_vec_x2)
> > - VPCMPEQ %ymm4, %ymm0, %ymm4
> > - vpmovmskb %ymm4, %eax
> > -L(first_vec_x3):
> > + jz L(cross_page_continue)
> > tzcntl %eax, %eax
> > - addq $(VEC_SIZE * 3), %rax
> > - addq %rdi, %rax
> > - subq %rdx, %rax
> > -# ifdef USE_AS_WCSLEN
> > - shrq $2, %rax
> > +# ifdef USE_AS_WCSLEN
> > + shrl $2, %eax
> > +# endif
> > # endif
> > +L(return_vzeroupper):
> > + ZERO_UPPER_VEC_REGISTERS_RETURN
> > +
> > +# ifdef USE_AS_STRNLEN
> > + .p2align 4
> > +L(cross_page_less_vec):
> > + tzcntl %eax, %eax
> > + cmpq %rax, %rsi
> > + cmovb %esi, %eax
> > +# ifdef USE_AS_WCSLEN
> > + shrl $2, %eax
> > +# endif
> > VZEROUPPER_RETURN
> > +# endif
> >
> > END (STRLEN)
> > #endif
> > --
> > 2.29.2
> >
next prev parent reply other threads:[~2021-04-19 23:39 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 18:43 [PATCH v4 1/2] x86: Optimize strlen-evex.S Noah Goldstein
2021-04-19 18:43 ` [PATCH v4 2/2] x86: Optimize strlen-avx2.S Noah Goldstein
2021-04-19 22:16 ` H.J. Lu
2021-04-19 23:39 ` Noah Goldstein [this message]
2021-04-19 22:16 ` [PATCH v4 1/2] x86: Optimize strlen-evex.S H.J. Lu
2021-04-19 23:38 ` Noah Goldstein
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAFUsyfLBiy9jcD3h4FMBk6ocHDM5jcezVWig7-ufpkN_JOw=Gw@mail.gmail.com' \
--to=goldstein.w.n@gmail.com \
--cc=carlos@systemhalted.org \
--cc=hjl.tools@gmail.com \
--cc=libc-alpha@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).