[PATCH v1 03/23] x86: Code cleanup in strchr-avx2 and comment justifying branch
H.J. Lu
hjl.tools@gmail.com
Thu Mar 24 18:53:07 GMT 2022
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.
> 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.
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