[v2,2/3] x86: Optimize memchr-avx2.S

Message ID 20210503200655.2164487-1-goldstein.w.n@gmail.com
State Superseded
Headers show
Series
  • Untitled series #37435
Related show

Commit Message

Martin Sebor via Libc-alpha May 3, 2021, 8:06 p.m.
No bug. This commit optimizes memchr-avx2.S. The optimizations include
replacing some branches with cmovcc, avoiding some branches entirely
in the less_4x_vec case, making the page cross logic less strict,
asaving a few instructions the in loop return loop. test-memchr,
test-rawmemchr, and test-wmemchr are all passing.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>

---
 sysdeps/x86_64/multiarch/memchr-avx2.S | 426 ++++++++++++++-----------
 1 file changed, 247 insertions(+), 179 deletions(-)

-- 
2.29.2

Comments

Martin Sebor via Libc-alpha May 3, 2021, 10:25 p.m. | #1
On Mon, May 03, 2021 at 04:06:54PM -0400, Noah Goldstein wrote:
> No bug. This commit optimizes memchr-avx2.S. The optimizations include

> replacing some branches with cmovcc, avoiding some branches entirely

> in the less_4x_vec case, making the page cross logic less strict,

> asaving a few instructions the in loop return loop. test-memchr,

> test-rawmemchr, and test-wmemchr are all passing.

> 

> Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>

> ---

>  sysdeps/x86_64/multiarch/memchr-avx2.S | 426 ++++++++++++++-----------

>  1 file changed, 247 insertions(+), 179 deletions(-)

> 

> diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S

> index 1fcb1c350f..8b862fb9d1 100644

> --- a/sysdeps/x86_64/multiarch/memchr-avx2.S

> +++ b/sysdeps/x86_64/multiarch/memchr-avx2.S

> @@ -26,8 +26,22 @@

>  

>  # ifdef USE_AS_WMEMCHR

>  #  define VPCMPEQ	vpcmpeqd

> +#  define VPBROADCAST	vpbroadcastd

> +#  define CHAR_SIZE	4

>  # else

>  #  define VPCMPEQ	vpcmpeqb

> +#  define VPBROADCAST	vpbroadcastb

> +#  define CHAR_SIZE	1

> +# endif

> +

> +# ifdef USE_AS_RAWMEMCHR

> +#  define ERAW_PTR_REG	ecx

> +#  define RRAW_PTR_REG	rcx

> +#  define ALGN_PTR_REG	rdi

> +# else

> +#  define ERAW_PTR_REG	edi

> +#  define RRAW_PTR_REG	rdi

> +#  define ALGN_PTR_REG	rcx

>  # endif

>  

>  # ifndef VZEROUPPER

> @@ -39,6 +53,7 @@

>  # endif

>  

>  # define VEC_SIZE 32

> +# define PAGE_SIZE 4096

>  

>  	.section SECTION(.text),"ax",@progbits

>  ENTRY (MEMCHR)

> @@ -47,295 +62,348 @@ ENTRY (MEMCHR)

>  	test	%RDX_LP, %RDX_LP

>  	jz	L(null)

>  # endif

> -	movl	%edi, %ecx

> -	/* Broadcast CHAR to YMM0.  */

> -	vmovd	%esi, %xmm0

>  # ifdef USE_AS_WMEMCHR

>  	shl	$2, %RDX_LP

> -	vpbroadcastd %xmm0, %ymm0

>  # else

>  #  ifdef __ILP32__

>  	/* Clear the upper 32 bits.  */

>  	movl	%edx, %edx

>  #  endif

> -	vpbroadcastb %xmm0, %ymm0

>  # endif

> +	/* Broadcast CHAR to YMMMATCH.  */

> +	vmovd	%esi, %xmm0

> +	VPBROADCAST %xmm0, %ymm0

>  	/* 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)

> +	movl	%edi, %eax

> +	andl	$(PAGE_SIZE - 1), %eax

> +	cmpl	$(PAGE_SIZE - VEC_SIZE), %eax

> +	ja	L(cross_page_boundary)

>  

>  	/* Check the first VEC_SIZE bytes.  */

> -	VPCMPEQ (%rdi), %ymm0, %ymm1

> +	VPCMPEQ	(%rdi), %ymm0, %ymm1

>  	vpmovmskb %ymm1, %eax

> -	testl	%eax, %eax

> -

>  # ifndef USE_AS_RAWMEMCHR

> -	jnz	L(first_vec_x0_check)

> -	/* Adjust length and check the end of data.  */

> -	subq	$VEC_SIZE, %rdx

> -	jbe	L(zero)

> -# else

> -	jnz	L(first_vec_x0)

> +	/* If length < CHAR_PER_VEC handle special.  */

> +	cmpq	$VEC_SIZE, %rdx

> +	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

> +	addq	%rdi, %rax

> +	VZEROUPPER_RETURN

>  

>  # ifndef USE_AS_RAWMEMCHR

> -	/* Adjust length.  */

> -	addq	%rcx, %rdx

> -

> -	subq	$(VEC_SIZE * 4), %rdx

> -	jbe	L(last_4x_vec_or_less)

> +	.p2align 5

> +L(first_vec_x0):

> +	/* Check if first match was before length.  */

> +	tzcntl	%eax, %eax

> +	xorl	%ecx, %ecx

> +	cmpl	%eax, %edx

> +	leaq	(%rdi, %rax), %rax

> +	cmovle	%rcx, %rax

> +	VZEROUPPER_RETURN


Please add a blank line here to indicate this begin a new block.
OK with this change.  You should be able to push it yourself now.

Thanks.

> +L(null):

> +	xorl	%eax, %eax

> +	ret

>  # 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

> +L(cross_page_boundary):

> +	/* Save pointer before aligning as its original value is necessary

> +	   for computer return address if byte is found or adjusting length

> +	   if it is not and this is memchr.  */

> +	movq	%rdi, %rcx

> +	/* Align data to VEC_SIZE - 1. ALGN_PTR_REG is rcx for memchr and

> +	   rdi for rawmemchr.  */

> +	orq	$(VEC_SIZE - 1), %ALGN_PTR_REG

> +	VPCMPEQ	-(VEC_SIZE - 1)(%ALGN_PTR_REG), %ymm0, %ymm1

>  	vpmovmskb %ymm1, %eax

> +# ifndef USE_AS_RAWMEMCHR

> +	/* Calculate length until end of page (length checked for a

> +	   match).  */

> +	leaq	1(%ALGN_PTR_REG), %rsi

> +	subq	%RRAW_PTR_REG, %rsi

> +# endif

>  	/* Remove the leading bytes.  */

> -	sarl	%cl, %eax

> -	testl	%eax, %eax

> -	jz	L(aligned_more)

> -	tzcntl	%eax, %eax

> +	sarxl	%ERAW_PTR_REG, %eax, %eax

>  # ifndef USE_AS_RAWMEMCHR

>  	/* Check the end of data.  */

> -	cmpq	%rax, %rdx

> -	jbe	L(zero)

> +	cmpq	%rsi, %rdx

> +	jbe	L(first_vec_x0)

>  # endif

> -	addq	%rdi, %rax

> -	addq	%rcx, %rax

> +	testl	%eax, %eax

> +	jz	L(cross_page_continue)

> +	tzcntl	%eax, %eax

> +	addq	%RRAW_PTR_REG, %rax

>  L(return_vzeroupper):

>  	ZERO_UPPER_VEC_REGISTERS_RETURN

>  

>  	.p2align 4

> -L(aligned_more):

> -# ifndef USE_AS_RAWMEMCHR

> -        /* 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

> +L(first_vec_x1):

> +	tzcntl	%eax, %eax

> +	incq	%rdi

> +	addq	%rdi, %rax

> +	VZEROUPPER_RETURN

>  

> -	/* Check the end of data.  */

> -	subq	%rcx, %rdx

> -	jbe	L(zero)

> -# endif

> +	.p2align 4

> +L(first_vec_x2):

> +	tzcntl	%eax, %eax

> +	addq	$(VEC_SIZE + 1), %rdi

> +	addq	%rdi, %rax

> +	VZEROUPPER_RETURN

>  

> -	addq	$VEC_SIZE, %rdi

> +	.p2align 4

> +L(first_vec_x3):

> +	tzcntl	%eax, %eax

> +	addq	$(VEC_SIZE * 2 + 1), %rdi

> +	addq	%rdi, %rax

> +	VZEROUPPER_RETURN

>  

> -# ifndef USE_AS_RAWMEMCHR

> -	subq	$(VEC_SIZE * 4), %rdx

> -	jbe	L(last_4x_vec_or_less)

> -# endif

>  

> -L(more_4x_vec):

> +	.p2align 4

> +L(first_vec_x4):

> +	tzcntl	%eax, %eax

> +	addq	$(VEC_SIZE * 3 + 1), %rdi

> +	addq	%rdi, %rax

> +	VZEROUPPER_RETURN

> +

> +	.p2align 4

> +L(aligned_more):

>  	/* 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

> +# ifndef USE_AS_RAWMEMCHR

> +L(cross_page_continue):

> +	/* Align data to VEC_SIZE - 1.  */

> +	xorl	%ecx, %ecx

> +	subl	%edi, %ecx

> +	orq	$(VEC_SIZE - 1), %rdi

> +	/* esi is for adjusting length to see if near the end.  */

> +	leal	(VEC_SIZE * 4 + 1)(%rdi, %rcx), %esi

> +# else

> +	orq	$(VEC_SIZE - 1), %rdi

> +L(cross_page_continue):

> +# endif

> +	/* Load first VEC regardless.  */

> +	VPCMPEQ	1(%rdi), %ymm0, %ymm1

>  	vpmovmskb %ymm1, %eax

> +# ifndef USE_AS_RAWMEMCHR

> +	/* Adjust length. If near end handle specially.  */

> +	subq	%rsi, %rdx

> +	jbe	L(last_4x_vec_or_less)

> +# endif

>  	testl	%eax, %eax

>  	jnz	L(first_vec_x1)

>  

> -	VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1

> +	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

> +	VPCMPEQ	(VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1

>  	vpmovmskb %ymm1, %eax

>  	testl	%eax, %eax

>  	jnz	L(first_vec_x3)

>  

> -	addq	$(VEC_SIZE * 4), %rdi

> +	VPCMPEQ	(VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1

> +	vpmovmskb %ymm1, %eax

> +	testl	%eax, %eax

> +	jnz	L(first_vec_x4)

>  

>  # ifndef USE_AS_RAWMEMCHR

> +	/* Check if at last VEC_SIZE * 4 length.  */

>  	subq	$(VEC_SIZE * 4), %rdx

> -	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

> -

> -# ifndef USE_AS_RAWMEMCHR

> -	/* Adjust length.  */

> +	jbe	L(last_4x_vec_or_less_cmpeq)

> +	/* Align data to VEC_SIZE * 4 - 1 for the loop and readjust

> +	   length.  */

> +	incq	%rdi

> +	movl	%edi, %ecx

> +	orq	$(VEC_SIZE * 4 - 1), %rdi

> +	andl	$(VEC_SIZE * 4 - 1), %ecx

>  	addq	%rcx, %rdx

> +# else

> +	/* Align data to VEC_SIZE * 4 - 1 for loop.  */

> +	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.  */

> -	VPCMPEQ (%rdi), %ymm0, %ymm1

> -	VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm2

> -	VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm3

> -	VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm4

> -

> +	VPCMPEQ	1(%rdi), %ymm0, %ymm1

> +	VPCMPEQ	(VEC_SIZE + 1)(%rdi), %ymm0, %ymm2

> +	VPCMPEQ	(VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm3

> +	VPCMPEQ	(VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm4

>  	vpor	%ymm1, %ymm2, %ymm5

>  	vpor	%ymm3, %ymm4, %ymm6

>  	vpor	%ymm5, %ymm6, %ymm5

>  

> -	vpmovmskb %ymm5, %eax

> -	testl	%eax, %eax

> -	jnz	L(4x_vec_end)

> -

> -	addq	$(VEC_SIZE * 4), %rdi

> -

> +	vpmovmskb %ymm5, %ecx

>  # ifdef USE_AS_RAWMEMCHR

> -	jmp	L(loop_4x_vec)

> +	subq	$-(VEC_SIZE * 4), %rdi

> +	testl	%ecx, %ecx

> +	jz	L(loop_4x_vec)

>  # else

> -	subq	$(VEC_SIZE * 4), %rdx

> -	ja	L(loop_4x_vec)

> +	testl	%ecx, %ecx

> +	jnz	L(loop_4x_vec_end)

>  

> -L(last_4x_vec_or_less):

> -	/* Less than 4 * VEC and aligned to VEC_SIZE.  */

> -	addl	$(VEC_SIZE * 2), %edx

> -	jle	L(last_2x_vec)

> +	subq	$-(VEC_SIZE * 4), %rdi

>  

> -	VPCMPEQ (%rdi), %ymm0, %ymm1

> -	vpmovmskb %ymm1, %eax

> -	testl	%eax, %eax

> -	jnz	L(first_vec_x0)

> +	subq	$(VEC_SIZE * 4), %rdx

> +	ja	L(loop_4x_vec)

>  

> -	VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1

> +	/* Fall through into less than 4 remaining vectors of length case.

> +	 */

> +	VPCMPEQ	(VEC_SIZE * 0 + 1)(%rdi), %ymm0, %ymm1

>  	vpmovmskb %ymm1, %eax

> +	.p2align 4

> +L(last_4x_vec_or_less):

> +	/* Check if first VEC contained match.  */

>  	testl	%eax, %eax

> -	jnz	L(first_vec_x1)

> +	jnz	L(first_vec_x1_check)

>  

> -	VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1

> -	vpmovmskb %ymm1, %eax

> -	testl	%eax, %eax

> +	/* If remaining length > VEC_SIZE * 2.  */

> +	addl	$(VEC_SIZE * 2), %edx

> +	jg	L(last_4x_vec)

>  

> -	jnz	L(first_vec_x2_check)

> -	subl	$VEC_SIZE, %edx

> -	jle	L(zero)

> +L(last_2x_vec):

> +	/* If remaining length < VEC_SIZE.  */

> +	addl	$VEC_SIZE, %edx

> +	jle	L(zero_end)

>  

> -	VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1

> +	/* Check VEC2 and compare any match with remaining length.  */

> +	VPCMPEQ	(VEC_SIZE + 1)(%rdi), %ymm0, %ymm1

>  	vpmovmskb %ymm1, %eax

> -	testl	%eax, %eax

> -

> -	jnz	L(first_vec_x3_check)

> -	xorl	%eax, %eax

> +	tzcntl	%eax, %eax

> +	cmpl	%eax, %edx

> +	jbe	L(set_zero_end)

> +	addq	$(VEC_SIZE + 1), %rdi

> +	addq	%rdi, %rax

> +L(zero_end):

>  	VZEROUPPER_RETURN

>  

>  	.p2align 4

> -L(last_2x_vec):

> -	addl	$(VEC_SIZE * 2), %edx

> -	VPCMPEQ (%rdi), %ymm0, %ymm1

> +L(loop_4x_vec_end):

> +# endif

> +	/* rawmemchr will fall through into this if match was found in

> +	   loop.  */

> +

>  	vpmovmskb %ymm1, %eax

>  	testl	%eax, %eax

> +	jnz	L(last_vec_x1_return)

>  

> -	jnz	L(first_vec_x0_check)

> -	subl	$VEC_SIZE, %edx

> -	jle	L(zero)

> -

> -	VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1

> -	vpmovmskb %ymm1, %eax

> +	vpmovmskb %ymm2, %eax

>  	testl	%eax, %eax

> -	jnz	L(first_vec_x1_check)

> -	xorl	%eax, %eax

> -	VZEROUPPER_RETURN

> +	jnz	L(last_vec_x2_return)

>  

> -	.p2align 4

> -L(first_vec_x0_check):

> -	tzcntl	%eax, %eax

> -	/* Check the end of data.  */

> -	cmpq	%rax, %rdx

> -	jbe	L(zero)

> +	vpmovmskb %ymm3, %eax

> +	/* Combine VEC3 matches (eax) with VEC4 matches (ecx).  */

> +	salq	$32, %rcx

> +	orq	%rcx, %rax

> +	tzcntq	%rax, %rax

> +# ifdef USE_AS_RAWMEMCHR

> +	subq	$(VEC_SIZE * 2 - 1), %rdi

> +# else

> +	subq	$-(VEC_SIZE * 2 + 1), %rdi

> +# endif

>  	addq	%rdi, %rax

>  	VZEROUPPER_RETURN

> +# ifndef USE_AS_RAWMEMCHR

>  

>  	.p2align 4

>  L(first_vec_x1_check):

>  	tzcntl	%eax, %eax

> -	/* Check the end of data.  */

> -	cmpq	%rax, %rdx

> -	jbe	L(zero)

> -	addq	$VEC_SIZE, %rax

> +	/* Adjust length.  */

> +	subl	$-(VEC_SIZE * 4), %edx

> +	/* Check if match within remaining length.  */

> +	cmpl	%eax, %edx

> +	jbe	L(set_zero_end)

> +	incq	%rdi

>  	addq	%rdi, %rax

>  	VZEROUPPER_RETURN

> +	.p2align 4

> +L(set_zero_end):

> +	xorl	%eax, %eax

> +	VZEROUPPER_RETURN

> +# endif

>  

>  	.p2align 4

> -L(first_vec_x2_check):

> +L(last_vec_x1_return):

>  	tzcntl	%eax, %eax

> -	/* Check the end of data.  */

> -	cmpq	%rax, %rdx

> -	jbe	L(zero)

> -	addq	$(VEC_SIZE * 2), %rax

> +# ifdef USE_AS_RAWMEMCHR

> +	subq	$(VEC_SIZE * 4 - 1), %rdi

> +# else

> +	incq	%rdi

> +# endif

>  	addq	%rdi, %rax

>  	VZEROUPPER_RETURN

>  

>  	.p2align 4

> -L(first_vec_x3_check):

> +L(last_vec_x2_return):

>  	tzcntl	%eax, %eax

> -	/* Check the end of data.  */

> -	cmpq	%rax, %rdx

> -	jbe	L(zero)

> -	addq	$(VEC_SIZE * 3), %rax

> +# ifdef USE_AS_RAWMEMCHR

> +	subq	$(VEC_SIZE * 3 - 1), %rdi

> +# else

> +	subq	$-(VEC_SIZE + 1), %rdi

> +# endif

>  	addq	%rdi, %rax

>  	VZEROUPPER_RETURN

>  

> +# ifndef USE_AS_RAWMEMCHR

>  	.p2align 4

> -L(zero):

> -	xorl	%eax, %eax

> -	jmp     L(return_vzeroupper)

> +L(last_4x_vec_or_less_cmpeq):

> +	VPCMPEQ	(VEC_SIZE * 4 + 1)(%rdi), %ymm0, %ymm1

> +	vpmovmskb %ymm1, %eax

> +	subq	$-(VEC_SIZE * 4), %rdi

> +	/* Check first VEC regardless.  */

> +	testl	%eax, %eax

> +	jnz	L(first_vec_x1_check)

>  

> +	/* If remaining length <= CHAR_PER_VEC * 2.  */

> +	addl	$(VEC_SIZE * 2), %edx

> +	jle	L(last_2x_vec)

>  	.p2align 4

> -L(null):

> -	xorl	%eax, %eax

> -	ret

> -# endif

> +L(last_4x_vec):

> +	VPCMPEQ	(VEC_SIZE + 1)(%rdi), %ymm0, %ymm1

> +	vpmovmskb %ymm1, %eax

> +	testl	%eax, %eax

> +	jnz	L(last_vec_x2_return)

>  

> -	.p2align 4

> -L(first_vec_x0):

> -	tzcntl	%eax, %eax

> -	addq	%rdi, %rax

> -	VZEROUPPER_RETURN

> +	VPCMPEQ	(VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1

> +	vpmovmskb %ymm1, %eax

>  

> -	.p2align 4

> -L(first_vec_x1):

> -	tzcntl	%eax, %eax

> -	addq	$VEC_SIZE, %rax

> -	addq	%rdi, %rax

> -	VZEROUPPER_RETURN

> +	/* Create mask for possible matches within remaining length.  */

> +	movq	$-1, %rcx

> +	bzhiq	%rdx, %rcx, %rcx

>  

> -	.p2align 4

> -L(first_vec_x2):

> +	/* Test matches in data against length match.  */

> +	andl	%ecx, %eax

> +	jnz	L(last_vec_x3)

> +

> +	/* if remaining length <= VEC_SIZE * 3 (Note this is after

> +	   remaining length was found to be > VEC_SIZE * 2.  */

> +	subl	$VEC_SIZE, %edx

> +	jbe	L(zero_end2)

> +

> +	VPCMPEQ	(VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1

> +	vpmovmskb %ymm1, %eax

> +	/* Shift remaining length mask for last VEC.  */

> +	shrq	$32, %rcx

> +	andl	%ecx, %eax

> +	jz	L(zero_end2)

>  	tzcntl	%eax, %eax

> -	addq	$(VEC_SIZE * 2), %rax

> +	addq	$(VEC_SIZE * 3 + 1), %rdi

>  	addq	%rdi, %rax

> +L(zero_end2):

>  	VZEROUPPER_RETURN

>  

>  	.p2align 4

> -L(4x_vec_end):

> -	vpmovmskb %ymm1, %eax

> -	testl	%eax, %eax

> -	jnz	L(first_vec_x0)

> -	vpmovmskb %ymm2, %eax

> -	testl	%eax, %eax

> -	jnz	L(first_vec_x1)

> -	vpmovmskb %ymm3, %eax

> -	testl	%eax, %eax

> -	jnz	L(first_vec_x2)

> -	vpmovmskb %ymm4, %eax

> -	testl	%eax, %eax

> -L(first_vec_x3):

> +L(last_vec_x3):

>  	tzcntl	%eax, %eax

> -	addq	$(VEC_SIZE * 3), %rax

> +	subq	$-(VEC_SIZE * 2 + 1), %rdi

>  	addq	%rdi, %rax

>  	VZEROUPPER_RETURN

> +# endif

>  

>  END (MEMCHR)

>  #endif

> -- 

> 2.29.2

>
Martin Sebor via Libc-alpha May 3, 2021, 10:58 p.m. | #2
On Mon, May 3, 2021 at 6:25 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>

> On Mon, May 03, 2021 at 04:06:54PM -0400, Noah Goldstein wrote:

> > No bug. This commit optimizes memchr-avx2.S. The optimizations include

> > replacing some branches with cmovcc, avoiding some branches entirely

> > in the less_4x_vec case, making the page cross logic less strict,

> > asaving a few instructions the in loop return loop. test-memchr,

> > test-rawmemchr, and test-wmemchr are all passing.

> >

> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>

> > ---

> >  sysdeps/x86_64/multiarch/memchr-avx2.S | 426 ++++++++++++++-----------

> >  1 file changed, 247 insertions(+), 179 deletions(-)

> >

> > diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S

> > index 1fcb1c350f..8b862fb9d1 100644

> > --- a/sysdeps/x86_64/multiarch/memchr-avx2.S

> > +++ b/sysdeps/x86_64/multiarch/memchr-avx2.S

> > @@ -26,8 +26,22 @@

> >

> >  # ifdef USE_AS_WMEMCHR

> >  #  define VPCMPEQ    vpcmpeqd

> > +#  define VPBROADCAST        vpbroadcastd

> > +#  define CHAR_SIZE  4

> >  # else

> >  #  define VPCMPEQ    vpcmpeqb

> > +#  define VPBROADCAST        vpbroadcastb

> > +#  define CHAR_SIZE  1

> > +# endif

> > +

> > +# ifdef USE_AS_RAWMEMCHR

> > +#  define ERAW_PTR_REG       ecx

> > +#  define RRAW_PTR_REG       rcx

> > +#  define ALGN_PTR_REG       rdi

> > +# else

> > +#  define ERAW_PTR_REG       edi

> > +#  define RRAW_PTR_REG       rdi

> > +#  define ALGN_PTR_REG       rcx

> >  # endif

> >

> >  # ifndef VZEROUPPER

> > @@ -39,6 +53,7 @@

> >  # endif

> >

> >  # define VEC_SIZE 32

> > +# define PAGE_SIZE 4096

> >

> >       .section SECTION(.text),"ax",@progbits

> >  ENTRY (MEMCHR)

> > @@ -47,295 +62,348 @@ ENTRY (MEMCHR)

> >       test    %RDX_LP, %RDX_LP

> >       jz      L(null)

> >  # endif

> > -     movl    %edi, %ecx

> > -     /* Broadcast CHAR to YMM0.  */

> > -     vmovd   %esi, %xmm0

> >  # ifdef USE_AS_WMEMCHR

> >       shl     $2, %RDX_LP

> > -     vpbroadcastd %xmm0, %ymm0

> >  # else

> >  #  ifdef __ILP32__

> >       /* Clear the upper 32 bits.  */

> >       movl    %edx, %edx

> >  #  endif

> > -     vpbroadcastb %xmm0, %ymm0

> >  # endif

> > +     /* Broadcast CHAR to YMMMATCH.  */

> > +     vmovd   %esi, %xmm0

> > +     VPBROADCAST %xmm0, %ymm0

> >       /* 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)

> > +     movl    %edi, %eax

> > +     andl    $(PAGE_SIZE - 1), %eax

> > +     cmpl    $(PAGE_SIZE - VEC_SIZE), %eax

> > +     ja      L(cross_page_boundary)

> >

> >       /* Check the first VEC_SIZE bytes.  */

> > -     VPCMPEQ (%rdi), %ymm0, %ymm1

> > +     VPCMPEQ (%rdi), %ymm0, %ymm1

> >       vpmovmskb %ymm1, %eax

> > -     testl   %eax, %eax

> > -

> >  # ifndef USE_AS_RAWMEMCHR

> > -     jnz     L(first_vec_x0_check)

> > -     /* Adjust length and check the end of data.  */

> > -     subq    $VEC_SIZE, %rdx

> > -     jbe     L(zero)

> > -# else

> > -     jnz     L(first_vec_x0)

> > +     /* If length < CHAR_PER_VEC handle special.  */

> > +     cmpq    $VEC_SIZE, %rdx

> > +     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

> > +     addq    %rdi, %rax

> > +     VZEROUPPER_RETURN

> >

> >  # ifndef USE_AS_RAWMEMCHR

> > -     /* Adjust length.  */

> > -     addq    %rcx, %rdx

> > -

> > -     subq    $(VEC_SIZE * 4), %rdx

> > -     jbe     L(last_4x_vec_or_less)

> > +     .p2align 5

> > +L(first_vec_x0):

> > +     /* Check if first match was before length.  */

> > +     tzcntl  %eax, %eax

> > +     xorl    %ecx, %ecx

> > +     cmpl    %eax, %edx

> > +     leaq    (%rdi, %rax), %rax

> > +     cmovle  %rcx, %rax

> > +     VZEROUPPER_RETURN

>

> Please add a blank line here to indicate this begin a new block.


Done.

> OK with this change.  You should be able to push it yourself now.


Will do. Thanks!


>

> Thanks.

>

> > +L(null):

> > +     xorl    %eax, %eax

> > +     ret

> >  # 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

> > +L(cross_page_boundary):

> > +     /* Save pointer before aligning as its original value is necessary

> > +        for computer return address if byte is found or adjusting length

> > +        if it is not and this is memchr.  */

> > +     movq    %rdi, %rcx

> > +     /* Align data to VEC_SIZE - 1. ALGN_PTR_REG is rcx for memchr and

> > +        rdi for rawmemchr.  */

> > +     orq     $(VEC_SIZE - 1), %ALGN_PTR_REG

> > +     VPCMPEQ -(VEC_SIZE - 1)(%ALGN_PTR_REG), %ymm0, %ymm1

> >       vpmovmskb %ymm1, %eax

> > +# ifndef USE_AS_RAWMEMCHR

> > +     /* Calculate length until end of page (length checked for a

> > +        match).  */

> > +     leaq    1(%ALGN_PTR_REG), %rsi

> > +     subq    %RRAW_PTR_REG, %rsi

> > +# endif

> >       /* Remove the leading bytes.  */

> > -     sarl    %cl, %eax

> > -     testl   %eax, %eax

> > -     jz      L(aligned_more)

> > -     tzcntl  %eax, %eax

> > +     sarxl   %ERAW_PTR_REG, %eax, %eax

> >  # ifndef USE_AS_RAWMEMCHR

> >       /* Check the end of data.  */

> > -     cmpq    %rax, %rdx

> > -     jbe     L(zero)

> > +     cmpq    %rsi, %rdx

> > +     jbe     L(first_vec_x0)

> >  # endif

> > -     addq    %rdi, %rax

> > -     addq    %rcx, %rax

> > +     testl   %eax, %eax

> > +     jz      L(cross_page_continue)

> > +     tzcntl  %eax, %eax

> > +     addq    %RRAW_PTR_REG, %rax

> >  L(return_vzeroupper):

> >       ZERO_UPPER_VEC_REGISTERS_RETURN

> >

> >       .p2align 4

> > -L(aligned_more):

> > -# ifndef USE_AS_RAWMEMCHR

> > -        /* 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

> > +L(first_vec_x1):

> > +     tzcntl  %eax, %eax

> > +     incq    %rdi

> > +     addq    %rdi, %rax

> > +     VZEROUPPER_RETURN

> >

> > -     /* Check the end of data.  */

> > -     subq    %rcx, %rdx

> > -     jbe     L(zero)

> > -# endif

> > +     .p2align 4

> > +L(first_vec_x2):

> > +     tzcntl  %eax, %eax

> > +     addq    $(VEC_SIZE + 1), %rdi

> > +     addq    %rdi, %rax

> > +     VZEROUPPER_RETURN

> >

> > -     addq    $VEC_SIZE, %rdi

> > +     .p2align 4

> > +L(first_vec_x3):

> > +     tzcntl  %eax, %eax

> > +     addq    $(VEC_SIZE * 2 + 1), %rdi

> > +     addq    %rdi, %rax

> > +     VZEROUPPER_RETURN

> >

> > -# ifndef USE_AS_RAWMEMCHR

> > -     subq    $(VEC_SIZE * 4), %rdx

> > -     jbe     L(last_4x_vec_or_less)

> > -# endif

> >

> > -L(more_4x_vec):

> > +     .p2align 4

> > +L(first_vec_x4):

> > +     tzcntl  %eax, %eax

> > +     addq    $(VEC_SIZE * 3 + 1), %rdi

> > +     addq    %rdi, %rax

> > +     VZEROUPPER_RETURN

> > +

> > +     .p2align 4

> > +L(aligned_more):

> >       /* 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

> > +# ifndef USE_AS_RAWMEMCHR

> > +L(cross_page_continue):

> > +     /* Align data to VEC_SIZE - 1.  */

> > +     xorl    %ecx, %ecx

> > +     subl    %edi, %ecx

> > +     orq     $(VEC_SIZE - 1), %rdi

> > +     /* esi is for adjusting length to see if near the end.  */

> > +     leal    (VEC_SIZE * 4 + 1)(%rdi, %rcx), %esi

> > +# else

> > +     orq     $(VEC_SIZE - 1), %rdi

> > +L(cross_page_continue):

> > +# endif

> > +     /* Load first VEC regardless.  */

> > +     VPCMPEQ 1(%rdi), %ymm0, %ymm1

> >       vpmovmskb %ymm1, %eax

> > +# ifndef USE_AS_RAWMEMCHR

> > +     /* Adjust length. If near end handle specially.  */

> > +     subq    %rsi, %rdx

> > +     jbe     L(last_4x_vec_or_less)

> > +# endif

> >       testl   %eax, %eax

> >       jnz     L(first_vec_x1)

> >

> > -     VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1

> > +     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

> > +     VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1

> >       vpmovmskb %ymm1, %eax

> >       testl   %eax, %eax

> >       jnz     L(first_vec_x3)

> >

> > -     addq    $(VEC_SIZE * 4), %rdi

> > +     VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1

> > +     vpmovmskb %ymm1, %eax

> > +     testl   %eax, %eax

> > +     jnz     L(first_vec_x4)

> >

> >  # ifndef USE_AS_RAWMEMCHR

> > +     /* Check if at last VEC_SIZE * 4 length.  */

> >       subq    $(VEC_SIZE * 4), %rdx

> > -     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

> > -

> > -# ifndef USE_AS_RAWMEMCHR

> > -     /* Adjust length.  */

> > +     jbe     L(last_4x_vec_or_less_cmpeq)

> > +     /* Align data to VEC_SIZE * 4 - 1 for the loop and readjust

> > +        length.  */

> > +     incq    %rdi

> > +     movl    %edi, %ecx

> > +     orq     $(VEC_SIZE * 4 - 1), %rdi

> > +     andl    $(VEC_SIZE * 4 - 1), %ecx

> >       addq    %rcx, %rdx

> > +# else

> > +     /* Align data to VEC_SIZE * 4 - 1 for loop.  */

> > +     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.  */

> > -     VPCMPEQ (%rdi), %ymm0, %ymm1

> > -     VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm2

> > -     VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm3

> > -     VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm4

> > -

> > +     VPCMPEQ 1(%rdi), %ymm0, %ymm1

> > +     VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm2

> > +     VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm3

> > +     VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm4

> >       vpor    %ymm1, %ymm2, %ymm5

> >       vpor    %ymm3, %ymm4, %ymm6

> >       vpor    %ymm5, %ymm6, %ymm5

> >

> > -     vpmovmskb %ymm5, %eax

> > -     testl   %eax, %eax

> > -     jnz     L(4x_vec_end)

> > -

> > -     addq    $(VEC_SIZE * 4), %rdi

> > -

> > +     vpmovmskb %ymm5, %ecx

> >  # ifdef USE_AS_RAWMEMCHR

> > -     jmp     L(loop_4x_vec)

> > +     subq    $-(VEC_SIZE * 4), %rdi

> > +     testl   %ecx, %ecx

> > +     jz      L(loop_4x_vec)

> >  # else

> > -     subq    $(VEC_SIZE * 4), %rdx

> > -     ja      L(loop_4x_vec)

> > +     testl   %ecx, %ecx

> > +     jnz     L(loop_4x_vec_end)

> >

> > -L(last_4x_vec_or_less):

> > -     /* Less than 4 * VEC and aligned to VEC_SIZE.  */

> > -     addl    $(VEC_SIZE * 2), %edx

> > -     jle     L(last_2x_vec)

> > +     subq    $-(VEC_SIZE * 4), %rdi

> >

> > -     VPCMPEQ (%rdi), %ymm0, %ymm1

> > -     vpmovmskb %ymm1, %eax

> > -     testl   %eax, %eax

> > -     jnz     L(first_vec_x0)

> > +     subq    $(VEC_SIZE * 4), %rdx

> > +     ja      L(loop_4x_vec)

> >

> > -     VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1

> > +     /* Fall through into less than 4 remaining vectors of length case.

> > +      */

> > +     VPCMPEQ (VEC_SIZE * 0 + 1)(%rdi), %ymm0, %ymm1

> >       vpmovmskb %ymm1, %eax

> > +     .p2align 4

> > +L(last_4x_vec_or_less):

> > +     /* Check if first VEC contained match.  */

> >       testl   %eax, %eax

> > -     jnz     L(first_vec_x1)

> > +     jnz     L(first_vec_x1_check)

> >

> > -     VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1

> > -     vpmovmskb %ymm1, %eax

> > -     testl   %eax, %eax

> > +     /* If remaining length > VEC_SIZE * 2.  */

> > +     addl    $(VEC_SIZE * 2), %edx

> > +     jg      L(last_4x_vec)

> >

> > -     jnz     L(first_vec_x2_check)

> > -     subl    $VEC_SIZE, %edx

> > -     jle     L(zero)

> > +L(last_2x_vec):

> > +     /* If remaining length < VEC_SIZE.  */

> > +     addl    $VEC_SIZE, %edx

> > +     jle     L(zero_end)

> >

> > -     VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1

> > +     /* Check VEC2 and compare any match with remaining length.  */

> > +     VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1

> >       vpmovmskb %ymm1, %eax

> > -     testl   %eax, %eax

> > -

> > -     jnz     L(first_vec_x3_check)

> > -     xorl    %eax, %eax

> > +     tzcntl  %eax, %eax

> > +     cmpl    %eax, %edx

> > +     jbe     L(set_zero_end)

> > +     addq    $(VEC_SIZE + 1), %rdi

> > +     addq    %rdi, %rax

> > +L(zero_end):

> >       VZEROUPPER_RETURN

> >

> >       .p2align 4

> > -L(last_2x_vec):

> > -     addl    $(VEC_SIZE * 2), %edx

> > -     VPCMPEQ (%rdi), %ymm0, %ymm1

> > +L(loop_4x_vec_end):

> > +# endif

> > +     /* rawmemchr will fall through into this if match was found in

> > +        loop.  */

> > +

> >       vpmovmskb %ymm1, %eax

> >       testl   %eax, %eax

> > +     jnz     L(last_vec_x1_return)

> >

> > -     jnz     L(first_vec_x0_check)

> > -     subl    $VEC_SIZE, %edx

> > -     jle     L(zero)

> > -

> > -     VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1

> > -     vpmovmskb %ymm1, %eax

> > +     vpmovmskb %ymm2, %eax

> >       testl   %eax, %eax

> > -     jnz     L(first_vec_x1_check)

> > -     xorl    %eax, %eax

> > -     VZEROUPPER_RETURN

> > +     jnz     L(last_vec_x2_return)

> >

> > -     .p2align 4

> > -L(first_vec_x0_check):

> > -     tzcntl  %eax, %eax

> > -     /* Check the end of data.  */

> > -     cmpq    %rax, %rdx

> > -     jbe     L(zero)

> > +     vpmovmskb %ymm3, %eax

> > +     /* Combine VEC3 matches (eax) with VEC4 matches (ecx).  */

> > +     salq    $32, %rcx

> > +     orq     %rcx, %rax

> > +     tzcntq  %rax, %rax

> > +# ifdef USE_AS_RAWMEMCHR

> > +     subq    $(VEC_SIZE * 2 - 1), %rdi

> > +# else

> > +     subq    $-(VEC_SIZE * 2 + 1), %rdi

> > +# endif

> >       addq    %rdi, %rax

> >       VZEROUPPER_RETURN

> > +# ifndef USE_AS_RAWMEMCHR

> >

> >       .p2align 4

> >  L(first_vec_x1_check):

> >       tzcntl  %eax, %eax

> > -     /* Check the end of data.  */

> > -     cmpq    %rax, %rdx

> > -     jbe     L(zero)

> > -     addq    $VEC_SIZE, %rax

> > +     /* Adjust length.  */

> > +     subl    $-(VEC_SIZE * 4), %edx

> > +     /* Check if match within remaining length.  */

> > +     cmpl    %eax, %edx

> > +     jbe     L(set_zero_end)

> > +     incq    %rdi

> >       addq    %rdi, %rax

> >       VZEROUPPER_RETURN

> > +     .p2align 4

> > +L(set_zero_end):

> > +     xorl    %eax, %eax

> > +     VZEROUPPER_RETURN

> > +# endif

> >

> >       .p2align 4

> > -L(first_vec_x2_check):

> > +L(last_vec_x1_return):

> >       tzcntl  %eax, %eax

> > -     /* Check the end of data.  */

> > -     cmpq    %rax, %rdx

> > -     jbe     L(zero)

> > -     addq    $(VEC_SIZE * 2), %rax

> > +# ifdef USE_AS_RAWMEMCHR

> > +     subq    $(VEC_SIZE * 4 - 1), %rdi

> > +# else

> > +     incq    %rdi

> > +# endif

> >       addq    %rdi, %rax

> >       VZEROUPPER_RETURN

> >

> >       .p2align 4

> > -L(first_vec_x3_check):

> > +L(last_vec_x2_return):

> >       tzcntl  %eax, %eax

> > -     /* Check the end of data.  */

> > -     cmpq    %rax, %rdx

> > -     jbe     L(zero)

> > -     addq    $(VEC_SIZE * 3), %rax

> > +# ifdef USE_AS_RAWMEMCHR

> > +     subq    $(VEC_SIZE * 3 - 1), %rdi

> > +# else

> > +     subq    $-(VEC_SIZE + 1), %rdi

> > +# endif

> >       addq    %rdi, %rax

> >       VZEROUPPER_RETURN

> >

> > +# ifndef USE_AS_RAWMEMCHR

> >       .p2align 4

> > -L(zero):

> > -     xorl    %eax, %eax

> > -     jmp     L(return_vzeroupper)

> > +L(last_4x_vec_or_less_cmpeq):

> > +     VPCMPEQ (VEC_SIZE * 4 + 1)(%rdi), %ymm0, %ymm1

> > +     vpmovmskb %ymm1, %eax

> > +     subq    $-(VEC_SIZE * 4), %rdi

> > +     /* Check first VEC regardless.  */

> > +     testl   %eax, %eax

> > +     jnz     L(first_vec_x1_check)

> >

> > +     /* If remaining length <= CHAR_PER_VEC * 2.  */

> > +     addl    $(VEC_SIZE * 2), %edx

> > +     jle     L(last_2x_vec)

> >       .p2align 4

> > -L(null):

> > -     xorl    %eax, %eax

> > -     ret

> > -# endif

> > +L(last_4x_vec):

> > +     VPCMPEQ (VEC_SIZE + 1)(%rdi), %ymm0, %ymm1

> > +     vpmovmskb %ymm1, %eax

> > +     testl   %eax, %eax

> > +     jnz     L(last_vec_x2_return)

> >

> > -     .p2align 4

> > -L(first_vec_x0):

> > -     tzcntl  %eax, %eax

> > -     addq    %rdi, %rax

> > -     VZEROUPPER_RETURN

> > +     VPCMPEQ (VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1

> > +     vpmovmskb %ymm1, %eax

> >

> > -     .p2align 4

> > -L(first_vec_x1):

> > -     tzcntl  %eax, %eax

> > -     addq    $VEC_SIZE, %rax

> > -     addq    %rdi, %rax

> > -     VZEROUPPER_RETURN

> > +     /* Create mask for possible matches within remaining length.  */

> > +     movq    $-1, %rcx

> > +     bzhiq   %rdx, %rcx, %rcx

> >

> > -     .p2align 4

> > -L(first_vec_x2):

> > +     /* Test matches in data against length match.  */

> > +     andl    %ecx, %eax

> > +     jnz     L(last_vec_x3)

> > +

> > +     /* if remaining length <= VEC_SIZE * 3 (Note this is after

> > +        remaining length was found to be > VEC_SIZE * 2.  */

> > +     subl    $VEC_SIZE, %edx

> > +     jbe     L(zero_end2)

> > +

> > +     VPCMPEQ (VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1

> > +     vpmovmskb %ymm1, %eax

> > +     /* Shift remaining length mask for last VEC.  */

> > +     shrq    $32, %rcx

> > +     andl    %ecx, %eax

> > +     jz      L(zero_end2)

> >       tzcntl  %eax, %eax

> > -     addq    $(VEC_SIZE * 2), %rax

> > +     addq    $(VEC_SIZE * 3 + 1), %rdi

> >       addq    %rdi, %rax

> > +L(zero_end2):

> >       VZEROUPPER_RETURN

> >

> >       .p2align 4

> > -L(4x_vec_end):

> > -     vpmovmskb %ymm1, %eax

> > -     testl   %eax, %eax

> > -     jnz     L(first_vec_x0)

> > -     vpmovmskb %ymm2, %eax

> > -     testl   %eax, %eax

> > -     jnz     L(first_vec_x1)

> > -     vpmovmskb %ymm3, %eax

> > -     testl   %eax, %eax

> > -     jnz     L(first_vec_x2)

> > -     vpmovmskb %ymm4, %eax

> > -     testl   %eax, %eax

> > -L(first_vec_x3):

> > +L(last_vec_x3):

> >       tzcntl  %eax, %eax

> > -     addq    $(VEC_SIZE * 3), %rax

> > +     subq    $-(VEC_SIZE * 2 + 1), %rdi

> >       addq    %rdi, %rax

> >       VZEROUPPER_RETURN

> > +# endif

> >

> >  END (MEMCHR)

> >  #endif

> > --

> > 2.29.2

> >

Patch

diff --git a/sysdeps/x86_64/multiarch/memchr-avx2.S b/sysdeps/x86_64/multiarch/memchr-avx2.S
index 1fcb1c350f..8b862fb9d1 100644
--- a/sysdeps/x86_64/multiarch/memchr-avx2.S
+++ b/sysdeps/x86_64/multiarch/memchr-avx2.S
@@ -26,8 +26,22 @@ 
 
 # ifdef USE_AS_WMEMCHR
 #  define VPCMPEQ	vpcmpeqd
+#  define VPBROADCAST	vpbroadcastd
+#  define CHAR_SIZE	4
 # else
 #  define VPCMPEQ	vpcmpeqb
+#  define VPBROADCAST	vpbroadcastb
+#  define CHAR_SIZE	1
+# endif
+
+# ifdef USE_AS_RAWMEMCHR
+#  define ERAW_PTR_REG	ecx
+#  define RRAW_PTR_REG	rcx
+#  define ALGN_PTR_REG	rdi
+# else
+#  define ERAW_PTR_REG	edi
+#  define RRAW_PTR_REG	rdi
+#  define ALGN_PTR_REG	rcx
 # endif
 
 # ifndef VZEROUPPER
@@ -39,6 +53,7 @@ 
 # endif
 
 # define VEC_SIZE 32
+# define PAGE_SIZE 4096
 
 	.section SECTION(.text),"ax",@progbits
 ENTRY (MEMCHR)
@@ -47,295 +62,348 @@  ENTRY (MEMCHR)
 	test	%RDX_LP, %RDX_LP
 	jz	L(null)
 # endif
-	movl	%edi, %ecx
-	/* Broadcast CHAR to YMM0.  */
-	vmovd	%esi, %xmm0
 # ifdef USE_AS_WMEMCHR
 	shl	$2, %RDX_LP
-	vpbroadcastd %xmm0, %ymm0
 # else
 #  ifdef __ILP32__
 	/* Clear the upper 32 bits.  */
 	movl	%edx, %edx
 #  endif
-	vpbroadcastb %xmm0, %ymm0
 # endif
+	/* Broadcast CHAR to YMMMATCH.  */
+	vmovd	%esi, %xmm0
+	VPBROADCAST %xmm0, %ymm0
 	/* 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)
+	movl	%edi, %eax
+	andl	$(PAGE_SIZE - 1), %eax
+	cmpl	$(PAGE_SIZE - VEC_SIZE), %eax
+	ja	L(cross_page_boundary)
 
 	/* Check the first VEC_SIZE bytes.  */
-	VPCMPEQ (%rdi), %ymm0, %ymm1
+	VPCMPEQ	(%rdi), %ymm0, %ymm1
 	vpmovmskb %ymm1, %eax
-	testl	%eax, %eax
-
 # ifndef USE_AS_RAWMEMCHR
-	jnz	L(first_vec_x0_check)
-	/* Adjust length and check the end of data.  */
-	subq	$VEC_SIZE, %rdx
-	jbe	L(zero)
-# else
-	jnz	L(first_vec_x0)
+	/* If length < CHAR_PER_VEC handle special.  */
+	cmpq	$VEC_SIZE, %rdx
+	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
+	addq	%rdi, %rax
+	VZEROUPPER_RETURN
 
 # ifndef USE_AS_RAWMEMCHR
-	/* Adjust length.  */
-	addq	%rcx, %rdx
-
-	subq	$(VEC_SIZE * 4), %rdx
-	jbe	L(last_4x_vec_or_less)
+	.p2align 5
+L(first_vec_x0):
+	/* Check if first match was before length.  */
+	tzcntl	%eax, %eax
+	xorl	%ecx, %ecx
+	cmpl	%eax, %edx
+	leaq	(%rdi, %rax), %rax
+	cmovle	%rcx, %rax
+	VZEROUPPER_RETURN
+L(null):
+	xorl	%eax, %eax
+	ret
 # 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
+L(cross_page_boundary):
+	/* Save pointer before aligning as its original value is necessary
+	   for computer return address if byte is found or adjusting length
+	   if it is not and this is memchr.  */
+	movq	%rdi, %rcx
+	/* Align data to VEC_SIZE - 1. ALGN_PTR_REG is rcx for memchr and
+	   rdi for rawmemchr.  */
+	orq	$(VEC_SIZE - 1), %ALGN_PTR_REG
+	VPCMPEQ	-(VEC_SIZE - 1)(%ALGN_PTR_REG), %ymm0, %ymm1
 	vpmovmskb %ymm1, %eax
+# ifndef USE_AS_RAWMEMCHR
+	/* Calculate length until end of page (length checked for a
+	   match).  */
+	leaq	1(%ALGN_PTR_REG), %rsi
+	subq	%RRAW_PTR_REG, %rsi
+# endif
 	/* Remove the leading bytes.  */
-	sarl	%cl, %eax
-	testl	%eax, %eax
-	jz	L(aligned_more)
-	tzcntl	%eax, %eax
+	sarxl	%ERAW_PTR_REG, %eax, %eax
 # ifndef USE_AS_RAWMEMCHR
 	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
+	cmpq	%rsi, %rdx
+	jbe	L(first_vec_x0)
 # endif
-	addq	%rdi, %rax
-	addq	%rcx, %rax
+	testl	%eax, %eax
+	jz	L(cross_page_continue)
+	tzcntl	%eax, %eax
+	addq	%RRAW_PTR_REG, %rax
 L(return_vzeroupper):
 	ZERO_UPPER_VEC_REGISTERS_RETURN
 
 	.p2align 4
-L(aligned_more):
-# ifndef USE_AS_RAWMEMCHR
-        /* 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
+L(first_vec_x1):
+	tzcntl	%eax, %eax
+	incq	%rdi
+	addq	%rdi, %rax
+	VZEROUPPER_RETURN
 
-	/* Check the end of data.  */
-	subq	%rcx, %rdx
-	jbe	L(zero)
-# endif
+	.p2align 4
+L(first_vec_x2):
+	tzcntl	%eax, %eax
+	addq	$(VEC_SIZE + 1), %rdi
+	addq	%rdi, %rax
+	VZEROUPPER_RETURN
 
-	addq	$VEC_SIZE, %rdi
+	.p2align 4
+L(first_vec_x3):
+	tzcntl	%eax, %eax
+	addq	$(VEC_SIZE * 2 + 1), %rdi
+	addq	%rdi, %rax
+	VZEROUPPER_RETURN
 
-# ifndef USE_AS_RAWMEMCHR
-	subq	$(VEC_SIZE * 4), %rdx
-	jbe	L(last_4x_vec_or_less)
-# endif
 
-L(more_4x_vec):
+	.p2align 4
+L(first_vec_x4):
+	tzcntl	%eax, %eax
+	addq	$(VEC_SIZE * 3 + 1), %rdi
+	addq	%rdi, %rax
+	VZEROUPPER_RETURN
+
+	.p2align 4
+L(aligned_more):
 	/* 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
+# ifndef USE_AS_RAWMEMCHR
+L(cross_page_continue):
+	/* Align data to VEC_SIZE - 1.  */
+	xorl	%ecx, %ecx
+	subl	%edi, %ecx
+	orq	$(VEC_SIZE - 1), %rdi
+	/* esi is for adjusting length to see if near the end.  */
+	leal	(VEC_SIZE * 4 + 1)(%rdi, %rcx), %esi
+# else
+	orq	$(VEC_SIZE - 1), %rdi
+L(cross_page_continue):
+# endif
+	/* Load first VEC regardless.  */
+	VPCMPEQ	1(%rdi), %ymm0, %ymm1
 	vpmovmskb %ymm1, %eax
+# ifndef USE_AS_RAWMEMCHR
+	/* Adjust length. If near end handle specially.  */
+	subq	%rsi, %rdx
+	jbe	L(last_4x_vec_or_less)
+# endif
 	testl	%eax, %eax
 	jnz	L(first_vec_x1)
 
-	VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1
+	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
+	VPCMPEQ	(VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1
 	vpmovmskb %ymm1, %eax
 	testl	%eax, %eax
 	jnz	L(first_vec_x3)
 
-	addq	$(VEC_SIZE * 4), %rdi
+	VPCMPEQ	(VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1
+	vpmovmskb %ymm1, %eax
+	testl	%eax, %eax
+	jnz	L(first_vec_x4)
 
 # ifndef USE_AS_RAWMEMCHR
+	/* Check if at last VEC_SIZE * 4 length.  */
 	subq	$(VEC_SIZE * 4), %rdx
-	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
-
-# ifndef USE_AS_RAWMEMCHR
-	/* Adjust length.  */
+	jbe	L(last_4x_vec_or_less_cmpeq)
+	/* Align data to VEC_SIZE * 4 - 1 for the loop and readjust
+	   length.  */
+	incq	%rdi
+	movl	%edi, %ecx
+	orq	$(VEC_SIZE * 4 - 1), %rdi
+	andl	$(VEC_SIZE * 4 - 1), %ecx
 	addq	%rcx, %rdx
+# else
+	/* Align data to VEC_SIZE * 4 - 1 for loop.  */
+	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.  */
-	VPCMPEQ (%rdi), %ymm0, %ymm1
-	VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm2
-	VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm3
-	VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm4
-
+	VPCMPEQ	1(%rdi), %ymm0, %ymm1
+	VPCMPEQ	(VEC_SIZE + 1)(%rdi), %ymm0, %ymm2
+	VPCMPEQ	(VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm3
+	VPCMPEQ	(VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm4
 	vpor	%ymm1, %ymm2, %ymm5
 	vpor	%ymm3, %ymm4, %ymm6
 	vpor	%ymm5, %ymm6, %ymm5
 
-	vpmovmskb %ymm5, %eax
-	testl	%eax, %eax
-	jnz	L(4x_vec_end)
-
-	addq	$(VEC_SIZE * 4), %rdi
-
+	vpmovmskb %ymm5, %ecx
 # ifdef USE_AS_RAWMEMCHR
-	jmp	L(loop_4x_vec)
+	subq	$-(VEC_SIZE * 4), %rdi
+	testl	%ecx, %ecx
+	jz	L(loop_4x_vec)
 # else
-	subq	$(VEC_SIZE * 4), %rdx
-	ja	L(loop_4x_vec)
+	testl	%ecx, %ecx
+	jnz	L(loop_4x_vec_end)
 
-L(last_4x_vec_or_less):
-	/* Less than 4 * VEC and aligned to VEC_SIZE.  */
-	addl	$(VEC_SIZE * 2), %edx
-	jle	L(last_2x_vec)
+	subq	$-(VEC_SIZE * 4), %rdi
 
-	VPCMPEQ (%rdi), %ymm0, %ymm1
-	vpmovmskb %ymm1, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x0)
+	subq	$(VEC_SIZE * 4), %rdx
+	ja	L(loop_4x_vec)
 
-	VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
+	/* Fall through into less than 4 remaining vectors of length case.
+	 */
+	VPCMPEQ	(VEC_SIZE * 0 + 1)(%rdi), %ymm0, %ymm1
 	vpmovmskb %ymm1, %eax
+	.p2align 4
+L(last_4x_vec_or_less):
+	/* Check if first VEC contained match.  */
 	testl	%eax, %eax
-	jnz	L(first_vec_x1)
+	jnz	L(first_vec_x1_check)
 
-	VPCMPEQ (VEC_SIZE * 2)(%rdi), %ymm0, %ymm1
-	vpmovmskb %ymm1, %eax
-	testl	%eax, %eax
+	/* If remaining length > VEC_SIZE * 2.  */
+	addl	$(VEC_SIZE * 2), %edx
+	jg	L(last_4x_vec)
 
-	jnz	L(first_vec_x2_check)
-	subl	$VEC_SIZE, %edx
-	jle	L(zero)
+L(last_2x_vec):
+	/* If remaining length < VEC_SIZE.  */
+	addl	$VEC_SIZE, %edx
+	jle	L(zero_end)
 
-	VPCMPEQ (VEC_SIZE * 3)(%rdi), %ymm0, %ymm1
+	/* Check VEC2 and compare any match with remaining length.  */
+	VPCMPEQ	(VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
 	vpmovmskb %ymm1, %eax
-	testl	%eax, %eax
-
-	jnz	L(first_vec_x3_check)
-	xorl	%eax, %eax
+	tzcntl	%eax, %eax
+	cmpl	%eax, %edx
+	jbe	L(set_zero_end)
+	addq	$(VEC_SIZE + 1), %rdi
+	addq	%rdi, %rax
+L(zero_end):
 	VZEROUPPER_RETURN
 
 	.p2align 4
-L(last_2x_vec):
-	addl	$(VEC_SIZE * 2), %edx
-	VPCMPEQ (%rdi), %ymm0, %ymm1
+L(loop_4x_vec_end):
+# endif
+	/* rawmemchr will fall through into this if match was found in
+	   loop.  */
+
 	vpmovmskb %ymm1, %eax
 	testl	%eax, %eax
+	jnz	L(last_vec_x1_return)
 
-	jnz	L(first_vec_x0_check)
-	subl	$VEC_SIZE, %edx
-	jle	L(zero)
-
-	VPCMPEQ VEC_SIZE(%rdi), %ymm0, %ymm1
-	vpmovmskb %ymm1, %eax
+	vpmovmskb %ymm2, %eax
 	testl	%eax, %eax
-	jnz	L(first_vec_x1_check)
-	xorl	%eax, %eax
-	VZEROUPPER_RETURN
+	jnz	L(last_vec_x2_return)
 
-	.p2align 4
-L(first_vec_x0_check):
-	tzcntl	%eax, %eax
-	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
+	vpmovmskb %ymm3, %eax
+	/* Combine VEC3 matches (eax) with VEC4 matches (ecx).  */
+	salq	$32, %rcx
+	orq	%rcx, %rax
+	tzcntq	%rax, %rax
+# ifdef USE_AS_RAWMEMCHR
+	subq	$(VEC_SIZE * 2 - 1), %rdi
+# else
+	subq	$-(VEC_SIZE * 2 + 1), %rdi
+# endif
 	addq	%rdi, %rax
 	VZEROUPPER_RETURN
+# ifndef USE_AS_RAWMEMCHR
 
 	.p2align 4
 L(first_vec_x1_check):
 	tzcntl	%eax, %eax
-	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
-	addq	$VEC_SIZE, %rax
+	/* Adjust length.  */
+	subl	$-(VEC_SIZE * 4), %edx
+	/* Check if match within remaining length.  */
+	cmpl	%eax, %edx
+	jbe	L(set_zero_end)
+	incq	%rdi
 	addq	%rdi, %rax
 	VZEROUPPER_RETURN
+	.p2align 4
+L(set_zero_end):
+	xorl	%eax, %eax
+	VZEROUPPER_RETURN
+# endif
 
 	.p2align 4
-L(first_vec_x2_check):
+L(last_vec_x1_return):
 	tzcntl	%eax, %eax
-	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
-	addq	$(VEC_SIZE * 2), %rax
+# ifdef USE_AS_RAWMEMCHR
+	subq	$(VEC_SIZE * 4 - 1), %rdi
+# else
+	incq	%rdi
+# endif
 	addq	%rdi, %rax
 	VZEROUPPER_RETURN
 
 	.p2align 4
-L(first_vec_x3_check):
+L(last_vec_x2_return):
 	tzcntl	%eax, %eax
-	/* Check the end of data.  */
-	cmpq	%rax, %rdx
-	jbe	L(zero)
-	addq	$(VEC_SIZE * 3), %rax
+# ifdef USE_AS_RAWMEMCHR
+	subq	$(VEC_SIZE * 3 - 1), %rdi
+# else
+	subq	$-(VEC_SIZE + 1), %rdi
+# endif
 	addq	%rdi, %rax
 	VZEROUPPER_RETURN
 
+# ifndef USE_AS_RAWMEMCHR
 	.p2align 4
-L(zero):
-	xorl	%eax, %eax
-	jmp     L(return_vzeroupper)
+L(last_4x_vec_or_less_cmpeq):
+	VPCMPEQ	(VEC_SIZE * 4 + 1)(%rdi), %ymm0, %ymm1
+	vpmovmskb %ymm1, %eax
+	subq	$-(VEC_SIZE * 4), %rdi
+	/* Check first VEC regardless.  */
+	testl	%eax, %eax
+	jnz	L(first_vec_x1_check)
 
+	/* If remaining length <= CHAR_PER_VEC * 2.  */
+	addl	$(VEC_SIZE * 2), %edx
+	jle	L(last_2x_vec)
 	.p2align 4
-L(null):
-	xorl	%eax, %eax
-	ret
-# endif
+L(last_4x_vec):
+	VPCMPEQ	(VEC_SIZE + 1)(%rdi), %ymm0, %ymm1
+	vpmovmskb %ymm1, %eax
+	testl	%eax, %eax
+	jnz	L(last_vec_x2_return)
 
-	.p2align 4
-L(first_vec_x0):
-	tzcntl	%eax, %eax
-	addq	%rdi, %rax
-	VZEROUPPER_RETURN
+	VPCMPEQ	(VEC_SIZE * 2 + 1)(%rdi), %ymm0, %ymm1
+	vpmovmskb %ymm1, %eax
 
-	.p2align 4
-L(first_vec_x1):
-	tzcntl	%eax, %eax
-	addq	$VEC_SIZE, %rax
-	addq	%rdi, %rax
-	VZEROUPPER_RETURN
+	/* Create mask for possible matches within remaining length.  */
+	movq	$-1, %rcx
+	bzhiq	%rdx, %rcx, %rcx
 
-	.p2align 4
-L(first_vec_x2):
+	/* Test matches in data against length match.  */
+	andl	%ecx, %eax
+	jnz	L(last_vec_x3)
+
+	/* if remaining length <= VEC_SIZE * 3 (Note this is after
+	   remaining length was found to be > VEC_SIZE * 2.  */
+	subl	$VEC_SIZE, %edx
+	jbe	L(zero_end2)
+
+	VPCMPEQ	(VEC_SIZE * 3 + 1)(%rdi), %ymm0, %ymm1
+	vpmovmskb %ymm1, %eax
+	/* Shift remaining length mask for last VEC.  */
+	shrq	$32, %rcx
+	andl	%ecx, %eax
+	jz	L(zero_end2)
 	tzcntl	%eax, %eax
-	addq	$(VEC_SIZE * 2), %rax
+	addq	$(VEC_SIZE * 3 + 1), %rdi
 	addq	%rdi, %rax
+L(zero_end2):
 	VZEROUPPER_RETURN
 
 	.p2align 4
-L(4x_vec_end):
-	vpmovmskb %ymm1, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x0)
-	vpmovmskb %ymm2, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x1)
-	vpmovmskb %ymm3, %eax
-	testl	%eax, %eax
-	jnz	L(first_vec_x2)
-	vpmovmskb %ymm4, %eax
-	testl	%eax, %eax
-L(first_vec_x3):
+L(last_vec_x3):
 	tzcntl	%eax, %eax
-	addq	$(VEC_SIZE * 3), %rax
+	subq	$-(VEC_SIZE * 2 + 1), %rdi
 	addq	%rdi, %rax
 	VZEROUPPER_RETURN
+# endif
 
 END (MEMCHR)
 #endif