[PATCH v5 1/2] x86: Optimize strlen-evex.S
H.J. Lu
hjl.tools@gmail.com
Tue Apr 20 01:01:00 GMT 2021
On Mon, Apr 19, 2021 at 4:36 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> No bug. This commit optimizes strlen-evex.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/strlen-evex.S | 581 ++++++++++++++-----------
> 1 file changed, 317 insertions(+), 264 deletions(-)
>
> diff --git a/sysdeps/x86_64/multiarch/strlen-evex.S b/sysdeps/x86_64/multiarch/strlen-evex.S
> index 0583819078..4bf6874b82 100644
> --- a/sysdeps/x86_64/multiarch/strlen-evex.S
> +++ b/sysdeps/x86_64/multiarch/strlen-evex.S
> @@ -29,11 +29,13 @@
> # ifdef USE_AS_WCSLEN
> # define VPCMP vpcmpd
> # define VPMINU vpminud
> -# define SHIFT_REG r9d
> +# define SHIFT_REG ecx
> +# define CHAR_SIZE 4
> # else
> # define VPCMP vpcmpb
> # define VPMINU vpminub
> -# define SHIFT_REG ecx
> +# define SHIFT_REG edx
> +# define CHAR_SIZE 1
> # endif
>
> # define XMMZERO xmm16
> @@ -46,132 +48,165 @@
> # define YMM6 ymm22
>
> # define VEC_SIZE 32
> +# define PAGE_SIZE 4096
> +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
>
> .section .text.evex,"ax",@progbits
> ENTRY (STRLEN)
> # ifdef USE_AS_STRNLEN
> - /* Check for zero length. */
> + /* Check zero length. */
> test %RSI_LP, %RSI_LP
> jz L(zero)
> -# ifdef USE_AS_WCSLEN
> - shl $2, %RSI_LP
> -# elif defined __ILP32__
> +# ifdef __ILP32__
> /* Clear the upper 32 bits. */
> movl %esi, %esi
> # endif
> mov %RSI_LP, %R8_LP
> # endif
> - movl %edi, %ecx
> - movq %rdi, %rdx
> + movl %edi, %eax
> vpxorq %XMMZERO, %XMMZERO, %XMMZERO
> -
> + /* 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. Each bit in K0 represents a
> null byte. */
> VPCMP $0, (%rdi), %YMMZERO, %k0
> kmovd %k0, %eax
> - testl %eax, %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 < CHAR_PER_VEC handle special. */
> + cmpq $CHAR_PER_VEC, %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
> -
> + testl %eax, %eax
> + jz L(aligned_more)
> + tzcntl %eax, %eax
> + ret
> # 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
> + ret
> # endif
> - jmp L(more_4x_vec)
>
> .p2align 4
> -L(cros_page_boundary):
> - andl $(VEC_SIZE - 1), %ecx
> - andq $-VEC_SIZE, %rdi
> -
> -# ifdef USE_AS_WCSLEN
> - /* NB: Divide shift count by 4 since each bit in K0 represent 4
> - bytes. */
> - movl %ecx, %SHIFT_REG
> - sarl $2, %SHIFT_REG
> +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
> + /* Use ecx which was computed earlier to compute correct value.
> + */
> + leal -(CHAR_PER_VEC * 4 + 1)(%rcx, %rax), %eax
> +# else
> + subl %edx, %edi
> +# ifdef USE_AS_WCSLEN
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarl $2, %edi
> +# endif
> + leal CHAR_PER_VEC(%rdi, %rax), %eax
> # endif
> - VPCMP $0, (%rdi), %YMMZERO, %k0
> - kmovd %k0, %eax
> + ret
>
> - /* Remove the leading bytes. */
> - sarxl %SHIFT_REG, %eax, %eax
> - testl %eax, %eax
> - jz L(aligned_more)
> + .p2align 4
> +L(first_vec_x2):
> tzcntl %eax, %eax
> -# ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> + /* 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)
> -# endif
> - addq %rdi, %rax
> - addq %rcx, %rax
> - subq %rdx, %rax
> -# ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> + /* Use ecx which was computed earlier to compute correct value.
> + */
> + leal -(CHAR_PER_VEC * 3 + 1)(%rcx, %rax), %eax
> +# else
> + subl %edx, %edi
> +# ifdef USE_AS_WCSLEN
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarl $2, %edi
> +# endif
> + leal (CHAR_PER_VEC * 2)(%rdi, %rax), %eax
> # endif
> ret
>
> .p2align 4
> -L(aligned_more):
> +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
> - /* "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.
> + */
> + leal -(CHAR_PER_VEC * 2 + 1)(%rcx, %rax), %eax
> +# else
> + subl %edx, %edi
> +# ifdef USE_AS_WCSLEN
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarl $2, %edi
> +# endif
> + leal (CHAR_PER_VEC * 3)(%rdi, %rax), %eax
> # endif
> + ret
>
> - addq $VEC_SIZE, %rdi
> -
> + .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.
> + */
> + leal -(CHAR_PER_VEC + 1)(%rcx, %rax), %eax
> +# else
> + subl %edx, %edi
> +# ifdef USE_AS_WCSLEN
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarl $2, %edi
> +# endif
> + leal (CHAR_PER_VEC * 4)(%rdi, %rax), %eax
> # endif
> + ret
>
> -L(more_4x_vec):
> + .p2align 5
> +L(aligned_more):
> + movq %rdi, %rdx
> + /* Align data to VEC_SIZE. */
> + andq $-(VEC_SIZE), %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. */
> - VPCMP $0, (%rdi), %YMMZERO, %k0
> - kmovd %k0, %eax
> - testl %eax, %eax
> - jnz L(first_vec_x0)
> -
> +# ifdef USE_AS_STRNLEN
> + /* + CHAR_SIZE because it simplies the logic in
> + last_4x_vec_or_less. */
> + leaq (VEC_SIZE * 5 + CHAR_SIZE)(%rdi), %rcx
> + subq %rdx, %rcx
> +# ifdef USE_AS_WCSLEN
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarl $2, %ecx
> +# endif
> +# endif
> + /* Load first VEC regardless. */
> VPCMP $0, VEC_SIZE(%rdi), %YMMZERO, %k0
> +# ifdef USE_AS_STRNLEN
> + /* Adjust length. If near end handle specially. */
> + subq %rcx, %rsi
> + jb L(last_4x_vec_or_less)
> +# endif
> kmovd %k0, %eax
> testl %eax, %eax
> jnz L(first_vec_x1)
>
> VPCMP $0, (VEC_SIZE * 2)(%rdi), %YMMZERO, %k0
> kmovd %k0, %eax
> - testl %eax, %eax
> + test %eax, %eax
> jnz L(first_vec_x2)
>
> VPCMP $0, (VEC_SIZE * 3)(%rdi), %YMMZERO, %k0
> @@ -179,258 +214,276 @@ L(more_4x_vec):
> 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
> + VPCMP $0, (VEC_SIZE * 4)(%rdi), %YMMZERO, %k0
> + kmovd %k0, %eax
> + testl %eax, %eax
> + jnz L(first_vec_x4)
>
> + addq $VEC_SIZE, %rdi
> # ifdef USE_AS_STRNLEN
> - /* Adjust length. */
> + /* Check if at last VEC_SIZE * 4 length. */
> + cmpq $(CHAR_PER_VEC * 4 - 1), %rsi
> + jbe L(last_4x_vec_or_less_load)
> + movl %edi, %ecx
> + andl $(VEC_SIZE * 4 - 1), %ecx
> +# ifdef USE_AS_WCSLEN
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarl $2, %ecx
> +# endif
> + /* Readjust length. */
> addq %rcx, %rsi
> # endif
> + /* Align data to VEC_SIZE * 4. */
> + andq $-(VEC_SIZE * 4), %rdi
>
> + /* Compare 4 * VEC at a time forward. */
> .p2align 4
> L(loop_4x_vec):
> - /* Compare 4 * VEC at a time forward. */
> - VMOVA (%rdi), %YMM1
> - VMOVA VEC_SIZE(%rdi), %YMM2
> - VMOVA (VEC_SIZE * 2)(%rdi), %YMM3
> - VMOVA (VEC_SIZE * 3)(%rdi), %YMM4
> -
> - VPMINU %YMM1, %YMM2, %YMM5
> - VPMINU %YMM3, %YMM4, %YMM6
> + /* Load first VEC regardless. */
> + VMOVA (VEC_SIZE * 4)(%rdi), %YMM1
> +# ifdef USE_AS_STRNLEN
> + /* Break if at end of length. */
> + subq $(CHAR_PER_VEC * 4), %rsi
> + 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.
> + */
> + VPMINU (VEC_SIZE * 5)(%rdi), %YMM1, %YMM2
> + VMOVA (VEC_SIZE * 6)(%rdi), %YMM3
> + VPMINU (VEC_SIZE * 7)(%rdi), %YMM3, %YMM4
> +
> + VPCMP $0, %YMM2, %YMMZERO, %k0
> + VPCMP $0, %YMM4, %YMMZERO, %k1
> + subq $-(VEC_SIZE * 4), %rdi
> + kortestd %k0, %k1
> + jz L(loop_4x_vec)
> +
> + /* Check if end was in first half. */
> + kmovd %k0, %eax
> + subq %rdx, %rdi
> +# ifdef USE_AS_WCSLEN
> + shrq $2, %rdi
> +# endif
> + testl %eax, %eax
> + jz L(second_vec_return)
>
> - VPMINU %YMM5, %YMM6, %YMM5
> - VPCMP $0, %YMM5, %YMMZERO, %k0
> - ktestd %k0, %k0
> - jnz L(4x_vec_end)
> + VPCMP $0, %YMM1, %YMMZERO, %k2
> + kmovd %k2, %edx
> + /* Combine VEC1 matches (edx) with VEC2 matches (eax). */
> +# ifdef USE_AS_WCSLEN
> + sall $CHAR_PER_VEC, %eax
> + orl %edx, %eax
> + tzcntl %eax, %eax
> +# else
> + salq $CHAR_PER_VEC, %rax
> + orq %rdx, %rax
> + tzcntq %rax, %rax
> +# endif
> + addq %rdi, %rax
> + ret
>
> - addq $(VEC_SIZE * 4), %rdi
>
> -# ifndef USE_AS_STRNLEN
> - jmp L(loop_4x_vec)
> -# else
> - subq $(VEC_SIZE * 4), %rsi
> - ja L(loop_4x_vec)
> +# ifdef USE_AS_STRNLEN
>
> +L(last_4x_vec_or_less_load):
> + /* Depending on entry adjust rdi / prepare first VEC in YMM1. */
> + VMOVA (VEC_SIZE * 4)(%rdi), %YMM1
> +L(last_4x_vec_or_less_cmpeq):
> + VPCMP $0, %YMM1, %YMMZERO, %k0
> + addq $(VEC_SIZE * 3), %rdi
> 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)
> -
> - VPCMP $0, (%rdi), %YMMZERO, %k0
> kmovd %k0, %eax
> + /* If remaining length > VEC_SIZE * 2. This works if esi is off by
> + VEC_SIZE * 4. */
> + testl $(CHAR_PER_VEC * 2), %esi
> + jnz L(last_4x_vec)
> +
> + /* length may have been negative or positive by an offset of
> + CHAR_PER_VEC * 4 depending on where this was called from. This
> + fixes that. */
> + andl $(CHAR_PER_VEC * 4 - 1), %esi
> testl %eax, %eax
> - jnz L(first_vec_x0)
> + jnz L(last_vec_x1_check)
>
> - VPCMP $0, VEC_SIZE(%rdi), %YMMZERO, %k0
> - kmovd %k0, %eax
> - testl %eax, %eax
> - jnz L(first_vec_x1)
> + /* Check the end of data. */
> + subl $CHAR_PER_VEC, %esi
> + jb L(max)
>
> VPCMP $0, (VEC_SIZE * 2)(%rdi), %YMMZERO, %k0
> kmovd %k0, %eax
> - testl %eax, %eax
> - jnz L(first_vec_x2_check)
> - subl $VEC_SIZE, %esi
> - jle L(max)
> + tzcntl %eax, %eax
> + /* Check the end of data. */
> + cmpl %eax, %esi
> + jb L(max)
>
> - VPCMP $0, (VEC_SIZE * 3)(%rdi), %YMMZERO, %k0
> - kmovd %k0, %eax
> - testl %eax, %eax
> - jnz L(first_vec_x3_check)
> + subq %rdx, %rdi
> +# ifdef USE_AS_WCSLEN
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarq $2, %rdi
> +# endif
> + leaq (CHAR_PER_VEC * 2)(%rdi, %rax), %rax
> + ret
> +L(max):
> movq %r8, %rax
> + ret
> +# endif
> +
> + /* Placed here in strnlen so that the jcc L(last_4x_vec_or_less)
> + in the 4x VEC loop can use 2 byte encoding. */
> + .p2align 4
> +L(second_vec_return):
> + VPCMP $0, %YMM3, %YMMZERO, %k0
> + /* Combine YMM3 matches (k0) with YMM4 matches (k1). */
> +# ifdef USE_AS_WCSLEN
> + kunpckbw %k0, %k1, %k0
> + kmovd %k0, %eax
> + tzcntl %eax, %eax
> +# else
> + kunpckdq %k0, %k1, %k0
> + kmovq %k0, %rax
> + tzcntq %rax, %rax
> +# endif
> + leaq (CHAR_PER_VEC * 2)(%rdi, %rax), %rax
> + ret
> +
> +
> +# ifdef USE_AS_STRNLEN
> +L(last_vec_x1_check):
> + tzcntl %eax, %eax
> + /* Check the end of data. */
> + cmpl %eax, %esi
> + jb L(max)
> + subq %rdx, %rdi
> # ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarq $2, %rdi
> # endif
> + leaq (CHAR_PER_VEC)(%rdi, %rax), %rax
> ret
>
> .p2align 4
> -L(last_2x_vec):
> - addl $(VEC_SIZE * 2), %esi
> +L(last_4x_vec):
> + /* Test first 2x VEC normally. */
> + testl %eax, %eax
> + jnz L(last_vec_x1)
>
> - VPCMP $0, (%rdi), %YMMZERO, %k0
> + VPCMP $0, (VEC_SIZE * 2)(%rdi), %YMMZERO, %k0
> kmovd %k0, %eax
> testl %eax, %eax
> - jnz L(first_vec_x0_check)
> - subl $VEC_SIZE, %esi
> - jle L(max)
> + jnz L(last_vec_x2)
>
> - VPCMP $0, VEC_SIZE(%rdi), %YMMZERO, %k0
> + /* Normalize length. */
> + andl $(CHAR_PER_VEC * 4 - 1), %esi
> + VPCMP $0, (VEC_SIZE * 3)(%rdi), %YMMZERO, %k0
> kmovd %k0, %eax
> testl %eax, %eax
> - jnz L(first_vec_x1_check)
> - movq %r8, %rax
> -# ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> -# endif
> - ret
> + jnz L(last_vec_x3)
>
> - .p2align 4
> -L(first_vec_x0_check):
> + /* Check the end of data. */
> + subl $(CHAR_PER_VEC * 3), %esi
> + jb L(max)
> +
> + VPCMP $0, (VEC_SIZE * 4)(%rdi), %YMMZERO, %k0
> + kmovd %k0, %eax
> tzcntl %eax, %eax
> -# ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> /* Check the end of data. */
> - cmpq %rax, %rsi
> - jbe L(max)
> - addq %rdi, %rax
> - subq %rdx, %rax
> + cmpl %eax, %esi
> + jb L(max_end)
> +
> + subq %rdx, %rdi
> # ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarq $2, %rdi
> # endif
> + leaq (CHAR_PER_VEC * 4)(%rdi, %rax), %rax
> ret
>
> .p2align 4
> -L(first_vec_x1_check):
> +L(last_vec_x1):
> tzcntl %eax, %eax
> + subq %rdx, %rdi
> # ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> - /* Check the end of data. */
> - cmpq %rax, %rsi
> - jbe L(max)
> - addq $VEC_SIZE, %rax
> - addq %rdi, %rax
> - subq %rdx, %rax
> -# ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarq $2, %rdi
> # endif
> + leaq (CHAR_PER_VEC)(%rdi, %rax), %rax
> ret
>
> .p2align 4
> -L(first_vec_x2_check):
> +L(last_vec_x2):
> tzcntl %eax, %eax
> + subq %rdx, %rdi
> # ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> - /* Check the end of data. */
> - cmpq %rax, %rsi
> - jbe L(max)
> - addq $(VEC_SIZE * 2), %rax
> - addq %rdi, %rax
> - subq %rdx, %rax
> -# ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarq $2, %rdi
> # endif
> + leaq (CHAR_PER_VEC * 2)(%rdi, %rax), %rax
> ret
>
> .p2align 4
> -L(first_vec_x3_check):
> +L(last_vec_x3):
> tzcntl %eax, %eax
> -# ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> + subl $(CHAR_PER_VEC * 2), %esi
> /* Check the end of data. */
> - cmpq %rax, %rsi
> - jbe L(max)
> - addq $(VEC_SIZE * 3), %rax
> - addq %rdi, %rax
> - subq %rdx, %rax
> + cmpl %eax, %esi
> + jb L(max_end)
> + subq %rdx, %rdi
> # ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> + /* NB: Divide bytes by 4 to get the wchar_t count. */
> + sarq $2, %rdi
> # endif
> + leaq (CHAR_PER_VEC * 3)(%rdi, %rax), %rax
> ret
> -
> - .p2align 4
> -L(max):
> +L(max_end):
> movq %r8, %rax
> -# ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> -# endif
> - ret
> -
> - .p2align 4
> -L(zero):
> - xorl %eax, %eax
> ret
> # endif
>
> + /* Cold case for crossing page with first load. */
> .p2align 4
> -L(first_vec_x0):
> - tzcntl %eax, %eax
> -# ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> - addq %rdi, %rax
> - subq %rdx, %rax
> +L(cross_page_boundary):
> + movq %rdi, %rdx
> + /* Align data to VEC_SIZE. */
> + andq $-VEC_SIZE, %rdi
> + VPCMP $0, (%rdi), %YMMZERO, %k0
> + kmovd %k0, %eax
> + /* Remove the leading bytes. */
> # ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> + /* NB: Divide shift count by 4 since each bit in K0 represent 4
> + bytes. */
> + movl %edx, %ecx
> + shrl $2, %ecx
> + andl $(CHAR_PER_VEC - 1), %ecx
> # endif
> - ret
> -
> - .p2align 4
> -L(first_vec_x1):
> + /* SHIFT_REG is ecx for USE_AS_WCSLEN and edx otherwise. */
> + sarxl %SHIFT_REG, %eax, %eax
> + testl %eax, %eax
> +# ifndef USE_AS_STRNLEN
> + jz L(cross_page_continue)
> tzcntl %eax, %eax
> -# ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> - addq $VEC_SIZE, %rax
> - addq %rdi, %rax
> - subq %rdx, %rax
> -# ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> -# endif
> ret
> -
> - .p2align 4
> -L(first_vec_x2):
> - tzcntl %eax, %eax
> -# ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> - addq $(VEC_SIZE * 2), %rax
> - addq %rdi, %rax
> - subq %rdx, %rax
> -# ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> -# endif
> +# else
> + jnz L(cross_page_less_vec)
> +# ifndef USE_AS_WCSLEN
> + movl %edx, %ecx
> + andl $(CHAR_PER_VEC - 1), %ecx
> +# endif
> + movl $CHAR_PER_VEC, %eax
> + subl %ecx, %eax
> + /* Check the end of data. */
> + cmpq %rax, %rsi
> + ja L(cross_page_continue)
> + movl %esi, %eax
> ret
> -
> - .p2align 4
> -L(4x_vec_end):
> - VPCMP $0, %YMM1, %YMMZERO, %k0
> - kmovd %k0, %eax
> - testl %eax, %eax
> - jnz L(first_vec_x0)
> - VPCMP $0, %YMM2, %YMMZERO, %k1
> - kmovd %k1, %eax
> - testl %eax, %eax
> - jnz L(first_vec_x1)
> - VPCMP $0, %YMM3, %YMMZERO, %k2
> - kmovd %k2, %eax
> - testl %eax, %eax
> - jnz L(first_vec_x2)
> - VPCMP $0, %YMM4, %YMMZERO, %k3
> - kmovd %k3, %eax
> -L(first_vec_x3):
> +L(cross_page_less_vec):
> tzcntl %eax, %eax
> -# ifdef USE_AS_WCSLEN
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - sall $2, %eax
> -# endif
> - addq $(VEC_SIZE * 3), %rax
> - addq %rdi, %rax
> - subq %rdx, %rax
> -# ifdef USE_AS_WCSLEN
> - shrq $2, %rax
> -# endif
> + /* Select min of length and position of first null. */
> + cmpq %rax, %rsi
> + cmovb %esi, %eax
> ret
> +# endif
>
> END (STRLEN)
> #endif
> --
> 2.29.2
>
LGTM. I am checking it in for you.
Thanks.
--
H.J.
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