From 8bb82fd62bdb2d8741998a5a1be38388890452da Mon Sep 17 00:00:00 2001

From: Noah Goldstein <goldstein.w.n@gmail.com>

Date: Mon, 3 May 2021 03:03:19 -0400

Subject: [PATCH] x86: Optimize memchr-evex.S

No bug. This commit optimizes memchr-evex.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,

saving some ALU in the alignment process, and most importantly

increasing ILP in the 4x loop. test-memchr, test-rawmemchr, and

test-wmemchr are all passing.

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

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

(cherry picked from commit 2a76821c3081d2c0231ecd2618f52662cb48fccd)

---

 sysdeps/x86_64/multiarch/memchr-evex.S | 547 +++++++++++++++----------

 1 file changed, 322 insertions(+), 225 deletions(-)

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

index 6dd5d67b..81d5cd64 100644

--- a/sysdeps/x86_64/multiarch/memchr-evex.S

+++ b/sysdeps/x86_64/multiarch/memchr-evex.S

@@ -26,14 +26,28 @@

 # ifdef USE_AS_WMEMCHR

 #  define VPBROADCAST	vpbroadcastd

-#  define VPCMP		vpcmpd

-#  define SHIFT_REG	r8d

+#  define VPMINU	vpminud

+#  define VPCMP	vpcmpd

+#  define VPCMPEQ	vpcmpeqd

+#  define CHAR_SIZE	4

 # else

 #  define VPBROADCAST	vpbroadcastb

-#  define VPCMP		vpcmpb

-#  define SHIFT_REG	ecx

+#  define VPMINU	vpminub

+#  define VPCMP	vpcmpb

+#  define VPCMPEQ	vpcmpeqb

+#  define CHAR_SIZE	1

 # endif

+# ifdef USE_AS_RAWMEMCHR

+#  define RAW_PTR_REG	rcx

+#  define ALGN_PTR_REG	rdi

+# else

+#  define RAW_PTR_REG	rdi

+#  define ALGN_PTR_REG	rcx

+# endif

+

+# define XMMZERO	xmm23

+# define YMMZERO	ymm23

 # define XMMMATCH	xmm16

 # define YMMMATCH	ymm16

 # define YMM1		ymm17

@@ -44,6 +58,8 @@

 # define YMM6		ymm22

 # define VEC_SIZE 32

+# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)

+# define PAGE_SIZE 4096

 	.section .text.evex,"ax",@progbits

 ENTRY (MEMCHR)

@@ -51,11 +67,7 @@ ENTRY (MEMCHR)

 	/* Check for zero length.  */

 	test	%RDX_LP, %RDX_LP

 	jz	L(zero)

-# endif

-	movl	%edi, %ecx

-# ifdef USE_AS_WMEMCHR

-	shl	$2, %RDX_LP

-# else

+

 #  ifdef __ILP32__

 	/* Clear the upper 32 bits.  */

 	movl	%edx, %edx

@@ -64,318 +76,403 @@ ENTRY (MEMCHR)

 	/* Broadcast CHAR to YMMMATCH.  */

 	VPBROADCAST %esi, %YMMMATCH

 	/* 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.  */

-	VPCMP	$0, (%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

-	testl	%eax, %eax

-

+	VPCMP	$0, (%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %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)

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

+	cmpq	$CHAR_PER_VEC, %rdx

+	jbe	L(first_vec_x0)

+# endif

+	testl	%eax, %eax

+	jz	L(aligned_more)

+	tzcntl	%eax, %eax

+# ifdef USE_AS_WMEMCHR

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

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

 # else

-	jnz	L(first_vec_x0)

+	addq	%rdi, %rax

 # endif

-

-	/* Align data for aligned loads in the loop.  */

-	addq	$VEC_SIZE, %rdi

-	andl	$(VEC_SIZE - 1), %ecx

-	andq	$-VEC_SIZE, %rdi

+	ret

 # ifndef USE_AS_RAWMEMCHR

-	/* Adjust length.  */

-	addq	%rcx, %rdx

-

-	subq	$(VEC_SIZE * 4), %rdx

-	jbe	L(last_4x_vec_or_less)

-# endif

-	jmp	L(more_4x_vec)

+L(zero):

+	xorl	%eax, %eax

+	ret

+	.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, CHAR_SIZE), %rax

+	cmovle	%rcx, %rax

+	ret

+# else

+	/* NB: first_vec_x0 is 17 bytes which will leave

+	   cross_page_boundary (which is relatively cold) close enough

+	   to ideal alignment. So only realign L(cross_page_boundary) if

+	   rawmemchr.  */

 	.p2align 4

-L(cros_page_boundary):

-	andl	$(VEC_SIZE - 1), %ecx

+# endif

+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. ALGN_PTR_REG is rcx for memchr and rdi

+	   for rawmemchr.  */

+	andq	$-VEC_SIZE, %ALGN_PTR_REG

+	VPCMP	$0, (%ALGN_PTR_REG), %YMMMATCH, %k0

+	kmovd	%k0, %r8d

 # ifdef USE_AS_WMEMCHR

-	/* NB: Divide shift count by 4 since each bit in K1 represent 4

+	/* NB: Divide shift count by 4 since each bit in K0 represent 4

 	   bytes.  */

-	movl	%ecx, %SHIFT_REG

-	sarl	$2, %SHIFT_REG

+	sarl	$2, %eax

+# endif

+# ifndef USE_AS_RAWMEMCHR

+	movl	$(PAGE_SIZE / CHAR_SIZE), %esi

+	subl	%eax, %esi

 # endif

-	andq	$-VEC_SIZE, %rdi

-	VPCMP	$0, (%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

-	/* Remove the leading bytes.  */

-	sarxl	%SHIFT_REG, %eax, %eax

-	testl	%eax, %eax

-	jz	L(aligned_more)

-	tzcntl	%eax, %eax

 # ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	sall	$2, %eax

+	andl	$(CHAR_PER_VEC - 1), %eax

 # endif

+	/* Remove the leading bytes.  */

+	sarxl	%eax, %r8d, %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

+	testl	%eax, %eax

+	jz	L(cross_page_continue)

+	tzcntl	%eax, %eax

+# ifdef USE_AS_WMEMCHR

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

+	leaq	(%RAW_PTR_REG, %rax, CHAR_SIZE), %rax

+# else

+	addq	%RAW_PTR_REG, %rax

 # endif

-	addq	%rdi, %rax

-	addq	%rcx, %rax

 	ret

 	.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

+	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax

+	ret

-	/* Check the end of data.  */

-	subq	%rcx, %rdx

-	jbe	L(zero)

-# endif

+	.p2align 4

+L(first_vec_x2):

+	tzcntl	%eax, %eax

+	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax

+	ret

-	addq	$VEC_SIZE, %rdi

+	.p2align 4

+L(first_vec_x3):

+	tzcntl	%eax, %eax

+	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax

+	ret

-# ifndef USE_AS_RAWMEMCHR

-	subq	$(VEC_SIZE * 4), %rdx

-	jbe	L(last_4x_vec_or_less)

-# endif

+	.p2align 4

+L(first_vec_x4):

+	tzcntl	%eax, %eax

+	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax

+	ret

-L(more_4x_vec):

+	.p2align 5

+L(aligned_more):

 	/* Check the first 4 * VEC_SIZE.  Only one VEC_SIZE at a time

 	   since data is only aligned to VEC_SIZE.  */

-	VPCMP	$0, (%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

-	testl	%eax, %eax

-	jnz	L(first_vec_x0)

-	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

+# ifndef USE_AS_RAWMEMCHR

+	/* Align data to VEC_SIZE.  */

+L(cross_page_continue):

+	xorl	%ecx, %ecx

+	subl	%edi, %ecx

+	andq	$-VEC_SIZE, %rdi

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

+	leal	(VEC_SIZE * 5)(%rdi, %rcx), %esi

+#  ifdef USE_AS_WMEMCHR

+	/* NB: Divide bytes by 4 to get the wchar_t count.  */

+	sarl	$2, %esi

+#  endif

+# else

+	andq	$-VEC_SIZE, %rdi

+L(cross_page_continue):

+# endif

+	/* Load first VEC regardless.  */

+	VPCMP	$0, (VEC_SIZE)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %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)

-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

+	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %eax

 	testl	%eax, %eax

 	jnz	L(first_vec_x2)

-	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

+	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %eax

 	testl	%eax, %eax

 	jnz	L(first_vec_x3)

-	addq	$(VEC_SIZE * 4), %rdi

+	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %eax

+	testl	%eax, %eax

+	jnz	L(first_vec_x4)

+

 # ifndef USE_AS_RAWMEMCHR

-	subq	$(VEC_SIZE * 4), %rdx

-	jbe	L(last_4x_vec_or_less)

-# endif

+	/* Check if at last CHAR_PER_VEC * 4 length.  */

+	subq	$(CHAR_PER_VEC * 4), %rdx

+	jbe	L(last_4x_vec_or_less_cmpeq)

+	addq	$VEC_SIZE, %rdi

-	/* Align data to 4 * VEC_SIZE.  */

-	movq	%rdi, %rcx

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

+	/* Align data to VEC_SIZE * 4 for the loop and readjust length.

+	 */

+#  ifdef USE_AS_WMEMCHR

+	movl	%edi, %ecx

 	andq	$-(4 * VEC_SIZE), %rdi

-

-# ifndef USE_AS_RAWMEMCHR

-	/* Adjust length.  */

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

+	/* NB: Divide bytes by 4 to get the wchar_t count.  */

+	sarl	$2, %ecx

 	addq	%rcx, %rdx

+#  else

+	addq	%rdi, %rdx

+	andq	$-(4 * VEC_SIZE), %rdi

+	subq	%rdi, %rdx

+#  endif

+# else

+	addq	$VEC_SIZE, %rdi

+	andq	$-(4 * VEC_SIZE), %rdi

 # endif

+	vpxorq	%XMMZERO, %XMMZERO, %XMMZERO

+

+	/* Compare 4 * VEC at a time forward.  */

 	.p2align 4

 L(loop_4x_vec):

-	/* Compare 4 * VEC at a time forward.  */

-	VPCMP	$0, (%rdi), %YMMMATCH, %k1

-	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k2

-	kord	%k1, %k2, %k5

-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k3

-	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k4

-

-	kord	%k3, %k4, %k6

-	kortestd %k5, %k6

-	jnz	L(4x_vec_end)

-

-	addq	$(VEC_SIZE * 4), %rdi

-

+	/* It would be possible to save some instructions using 4x VPCMP

+	   but bottleneck on port 5 makes it not woth it.  */

+	VPCMP	$4, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k1

+	/* xor will set bytes match esi to zero.  */

+	vpxorq	(VEC_SIZE * 5)(%rdi), %YMMMATCH, %YMM2

+	vpxorq	(VEC_SIZE * 6)(%rdi), %YMMMATCH, %YMM3

+	VPCMP	$0, (VEC_SIZE * 7)(%rdi), %YMMMATCH, %k3

+	/* Reduce VEC2 / VEC3 with min and VEC1 with zero mask.  */

+	VPMINU	%YMM2, %YMM3, %YMM3 {%k1} {z}

+	VPCMP	$0, %YMM3, %YMMZERO, %k2

 # ifdef USE_AS_RAWMEMCHR

-	jmp	L(loop_4x_vec)

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

+	kortestd %k2, %k3

+	jz	L(loop_4x_vec)

 # else

-	subq	$(VEC_SIZE * 4), %rdx

+	kortestd %k2, %k3

+	jnz	L(loop_4x_vec_end)

+

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

+

+	subq	$(CHAR_PER_VEC * 4), %rdx

 	ja	L(loop_4x_vec)

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

+	 */

+	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %eax

+	addq	$(VEC_SIZE * 3), %rdi

+	.p2align 4

 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)

-

-	VPCMP	$0, (%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

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

 	testl	%eax, %eax

-	jnz	L(first_vec_x0)

+	jnz	L(first_vec_x1_check)

-	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

-	testl	%eax, %eax

-	jnz	L(first_vec_x1)

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

+	addl	$(CHAR_PER_VEC * 2), %edx

+	jg	L(last_4x_vec)

-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

-	testl	%eax, %eax

+L(last_2x_vec):

+	/* If remaining length < CHAR_PER_VEC.  */

+	addl	$CHAR_PER_VEC, %edx

+	jle	L(zero_end)

-	jnz	L(first_vec_x2_check)

-	subl	$VEC_SIZE, %edx

-	jle	L(zero)

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

+	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %eax

+	tzcntl	%eax, %eax

+	cmpl	%eax, %edx

+	jbe	L(set_zero_end)

+	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax

+L(zero_end):

+	ret

-	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

-	testl	%eax, %eax

-	jnz	L(first_vec_x3_check)

+	.p2align 4

+L(first_vec_x1_check):

+	tzcntl	%eax, %eax

+	/* Adjust length.  */

+	subl	$-(CHAR_PER_VEC * 4), %edx

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

+	cmpl	%eax, %edx

+	jbe	L(set_zero_end)

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

+	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax

+	ret

+L(set_zero_end):

 	xorl	%eax, %eax

 	ret

 	.p2align 4

-L(last_2x_vec):

-	addl	$(VEC_SIZE * 2), %edx

-	VPCMP	$0, (%rdi), %YMMMATCH, %k1

+L(loop_4x_vec_end):

+# endif

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

+	   loop.  */

+

+	/* k1 has not of matches with VEC1.  */

 	kmovd	%k1, %eax

-	testl	%eax, %eax

+# ifdef USE_AS_WMEMCHR

+	subl	$((1 << CHAR_PER_VEC) - 1), %eax

+# else

+	incl	%eax

+# endif

+	jnz	L(last_vec_x1_return)

-	jnz	L(first_vec_x0_check)

-	subl	$VEC_SIZE, %edx

-	jle	L(zero)

+	VPCMP	$0, %YMM2, %YMMZERO, %k0

+	kmovd	%k0, %eax

+	testl	%eax, %eax

+	jnz	L(last_vec_x2_return)

-	VPCMP	$0, VEC_SIZE(%rdi), %YMMMATCH, %k1

-	kmovd	%k1, %eax

+	kmovd	%k2, %eax

 	testl	%eax, %eax

-	jnz	L(first_vec_x1_check)

-	xorl	%eax, %eax

-	ret

+	jnz	L(last_vec_x3_return)

-	.p2align 4

-L(first_vec_x0_check):

+	kmovd	%k3, %eax

 	tzcntl	%eax, %eax

-# ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	sall	$2, %eax

+# ifdef USE_AS_RAWMEMCHR

+	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax

+# else

+	leaq	(VEC_SIZE * 7)(%rdi, %rax, CHAR_SIZE), %rax

 # endif

-	/* Check the end of data.  */

-	cmpq	%rax, %rdx

-	jbe	L(zero)

-	addq	%rdi, %rax

 	ret

 	.p2align 4

-L(first_vec_x1_check):

+L(last_vec_x1_return):

 	tzcntl	%eax, %eax

-# ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	sall	$2, %eax

-# endif

-	/* Check the end of data.  */

-	cmpq	%rax, %rdx

-	jbe	L(zero)

-	addq	$VEC_SIZE, %rax

+# ifdef USE_AS_RAWMEMCHR

+#  ifdef USE_AS_WMEMCHR

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

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

+#  else

 	addq	%rdi, %rax

-	ret

-

-	.p2align 4

-L(first_vec_x2_check):

-	tzcntl	%eax, %eax

-# ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	sall	$2, %eax

+#  endif

+# else

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

+	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax

 # endif

-	/* Check the end of data.  */

-	cmpq	%rax, %rdx

-	jbe	L(zero)

-	addq	$(VEC_SIZE * 2), %rax

-	addq	%rdi, %rax

 	ret

 	.p2align 4

-L(first_vec_x3_check):

+L(last_vec_x2_return):

 	tzcntl	%eax, %eax

-# ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	sall	$2, %eax

+# ifdef USE_AS_RAWMEMCHR

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

+	leaq	VEC_SIZE(%rdi, %rax, CHAR_SIZE), %rax

+# else

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

+	leaq	(VEC_SIZE * 5)(%rdi, %rax, CHAR_SIZE), %rax

 # endif

-	/* Check the end of data.  */

-	cmpq	%rax, %rdx

-	jbe	L(zero)

-	addq	$(VEC_SIZE * 3), %rax

-	addq	%rdi, %rax

 	ret

 	.p2align 4

-L(zero):

-	xorl	%eax, %eax

-	ret

-# endif

-

-	.p2align 4

-L(first_vec_x0):

+L(last_vec_x3_return):

 	tzcntl	%eax, %eax

-# ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	leaq	(%rdi, %rax, 4), %rax

+# ifdef USE_AS_RAWMEMCHR

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

+	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax

 # else

-	addq	%rdi, %rax

+	/* NB: Multiply bytes by CHAR_SIZE to get the wchar_t count.  */

+	leaq	(VEC_SIZE * 6)(%rdi, %rax, CHAR_SIZE), %rax

 # endif

 	ret

+

+# ifndef USE_AS_RAWMEMCHR

+L(last_4x_vec_or_less_cmpeq):

+	VPCMP	$0, (VEC_SIZE * 5)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %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	$(CHAR_PER_VEC * 2), %edx

+	jle	L(last_2x_vec)

+

 	.p2align 4

-L(first_vec_x1):

+L(last_4x_vec):

+	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %eax

+	testl	%eax, %eax

+	jnz	L(last_vec_x2)

+

+

+	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %eax

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

+#  ifdef USE_AS_WMEMCHR

+	movl	$((1 << (CHAR_PER_VEC * 2)) - 1), %ecx

+	bzhil	%edx, %ecx, %ecx

+#  else

+	movq	$-1, %rcx

+	bzhiq	%rdx, %rcx, %rcx

+#  endif

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

+	andl	%ecx, %eax

+	jnz	L(last_vec_x3)

+

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

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

+	subl	$CHAR_PER_VEC, %edx

+	jbe	L(zero_end2)

+

+

+	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMMATCH, %k0

+	kmovd	%k0, %eax

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

+#  ifdef USE_AS_WMEMCHR

+	shrl	$CHAR_PER_VEC, %ecx

+#  else

+	shrq	$CHAR_PER_VEC, %rcx

+#  endif

+	andl	%ecx, %eax

+	jz	L(zero_end2)

 	tzcntl	%eax, %eax

-# ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	leaq	VEC_SIZE(%rdi, %rax, 4), %rax

-# else

-	addq	$VEC_SIZE, %rax

-	addq	%rdi, %rax

-# endif

+	leaq	(VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax

+L(zero_end2):

 	ret

-	.p2align 4

-L(first_vec_x2):

+L(last_vec_x2):

 	tzcntl	%eax, %eax

-# ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	leaq	(VEC_SIZE * 2)(%rdi, %rax, 4), %rax

-# else

-	addq	$(VEC_SIZE * 2), %rax

-	addq	%rdi, %rax

-# endif

+	leaq	(VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax

 	ret

 	.p2align 4

-L(4x_vec_end):

-	kmovd	%k1, %eax

-	testl	%eax, %eax

-	jnz	L(first_vec_x0)

-	kmovd	%k2, %eax

-	testl	%eax, %eax

-	jnz	L(first_vec_x1)

-	kmovd	%k3, %eax

-	testl	%eax, %eax

-	jnz	L(first_vec_x2)

-	kmovd	%k4, %eax

-	testl	%eax, %eax

-L(first_vec_x3):

+L(last_vec_x3):

 	tzcntl	%eax, %eax

-# ifdef USE_AS_WMEMCHR

-	/* NB: Multiply wchar_t count by 4 to get the number of bytes.  */

-	leaq	(VEC_SIZE * 3)(%rdi, %rax, 4), %rax

-# else

-	addq	$(VEC_SIZE * 3), %rax

-	addq	%rdi, %rax

-# endif

+	leaq	(VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax

 	ret

+# endif

 END (MEMCHR)

 #endif

-- 

GitLab