[glibc] x86: Optimize strnlen-evex.S and implement with VMM headers

[glibc] x86: Optimize strnlen-evex.S and implement with VMM headers

[Noah Goldstein]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b79f8ff26aa6151d2d2167afcddcd1ec46cfbc81

commit b79f8ff26aa6151d2d2167afcddcd1ec46cfbc81
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date:   Tue Oct 18 17:44:05 2022 -0700

    x86: Optimize strnlen-evex.S and implement with VMM headers
    
    Optimizations are:
    1. Use the fact that bsf(0) leaves the destination unchanged to save a
       branch in short string case.
    2. Restructure code so that small strings are given the hot path.
            - This is a net-zero on the benchmark suite but in general makes
          sense as smaller sizes are far more common.
    3. Use more code-size efficient instructions.
            - tzcnt ...     -> bsf ...
            - vpcmpb $0 ... -> vpcmpeq ...
    4. Align labels less aggressively, especially if it doesn't save fetch
       blocks / causes the basic-block to span extra cache-lines.
    
    The optimizations (especially for point 2) make the strnlen and
    strlen code essentially incompatible so split strnlen-evex
    to a new file.
    
    Code Size Changes:
    strlen-evex.S       :  -23 bytes
    strnlen-evex.S      : -167 bytes
    
    Net perf changes:
    
    Reported as geometric mean of all improvements / regressions from N=10
    runs of the benchtests. Value as New Time / Old Time so < 1.0 is
    improvement and 1.0 is regression.
    
    strlen-evex.S       : 0.992 (No real change)
    strnlen-evex.S      : 0.947
    
    Full results attached in email.
    
    Full check passes on x86-64.

Diff:
---
 sysdeps/x86_64/multiarch/strlen-evex.S  | 544 +++++++++-----------------------
 sysdeps/x86_64/multiarch/strnlen-evex.S | 427 ++++++++++++++++++++++++-
 sysdeps/x86_64/multiarch/wcsnlen-evex.S |   5 +-
 3 files changed, 572 insertions(+), 404 deletions(-)

diff --git a/sysdeps/x86_64/multiarch/strlen-evex.S b/sysdeps/x86_64/multiarch/strlen-evex.S
index 2109ec2f7a..487846f098 100644
--- a/sysdeps/x86_64/multiarch/strlen-evex.S
+++ b/sysdeps/x86_64/multiarch/strlen-evex.S
@@ -26,466 +26,220 @@
 #  define STRLEN	__strlen_evex
 # endif
 
-# define VMOVA		vmovdqa64
+# ifndef VEC_SIZE
+#  include "x86-evex256-vecs.h"
+# endif
 
 # ifdef USE_AS_WCSLEN
-#  define VPCMP		vpcmpd
+#  define VPCMPEQ	vpcmpeqd
+#  define VPCMPNEQ	vpcmpneqd
+#  define VPTESTN	vptestnmd
+#  define VPTEST	vptestmd
 #  define VPMINU	vpminud
-#  define SHIFT_REG ecx
 #  define CHAR_SIZE	4
+#  define CHAR_SIZE_SHIFT_REG(reg)	sar $2, %reg
 # else
-#  define VPCMP		vpcmpb
+#  define VPCMPEQ	vpcmpeqb
+#  define VPCMPNEQ	vpcmpneqb
+#  define VPTESTN	vptestnmb
+#  define VPTEST	vptestmb
 #  define VPMINU	vpminub
-#  define SHIFT_REG edx
 #  define CHAR_SIZE	1
+#  define CHAR_SIZE_SHIFT_REG(reg)
+
+#  define REG_WIDTH	VEC_SIZE
 # endif
 
-# define XMMZERO	xmm16
-# define YMMZERO	ymm16
-# define YMM1		ymm17
-# define YMM2		ymm18
-# define YMM3		ymm19
-# define YMM4		ymm20
-# define YMM5		ymm21
-# 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 zero length.  */
-	test	%RSI_LP, %RSI_LP
-	jz	L(zero)
-#  ifdef __ILP32__
-	/* Clear the upper 32 bits.  */
-	movl	%esi, %esi
-#  endif
-	mov	%RSI_LP, %R8_LP
+# define CHAR_PER_VEC	(VEC_SIZE / CHAR_SIZE)
+
+# include "reg-macros.h"
+
+# if CHAR_PER_VEC == 64
+
+#  define TAIL_RETURN_LBL	first_vec_x2
+#  define TAIL_RETURN_OFFSET	(CHAR_PER_VEC * 2)
+
+#  define FALLTHROUGH_RETURN_LBL	first_vec_x3
+#  define FALLTHROUGH_RETURN_OFFSET	(CHAR_PER_VEC * 3)
+
+# else
+
+#  define TAIL_RETURN_LBL	first_vec_x3
+#  define TAIL_RETURN_OFFSET	(CHAR_PER_VEC * 3)
+
+#  define FALLTHROUGH_RETURN_LBL	first_vec_x2
+#  define FALLTHROUGH_RETURN_OFFSET	(CHAR_PER_VEC * 2)
 # endif
+
+# define XZERO	VMM_128(0)
+# define VZERO	VMM(0)
+# define PAGE_SIZE	4096
+
+	.section SECTION(.text), "ax", @progbits
+ENTRY_P2ALIGN (STRLEN, 6)
 	movl	%edi, %eax
-	vpxorq	%XMMZERO, %XMMZERO, %XMMZERO
-	/* Clear high bits from edi. Only keeping bits relevant to page
-	   cross check.  */
+	vpxorq	%XZERO, %XZERO, %XZERO
 	andl	$(PAGE_SIZE - 1), %eax
-	/* Check if we may cross page boundary with one vector load.  */
 	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
-# ifdef USE_AS_STRNLEN
-	/* If length < CHAR_PER_VEC handle special.  */
-	cmpq	$CHAR_PER_VEC, %rsi
-	jbe	L(first_vec_x0)
-# endif
-	testl	%eax, %eax
+	VPCMPEQ	(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRAX
+	test	%VRAX, %VRAX
 	jz	L(aligned_more)
-	tzcntl	%eax, %eax
-	ret
-# ifdef USE_AS_STRNLEN
-L(zero):
-	xorl	%eax, %eax
-	ret
-
-	.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
-
-	.p2align 4
-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
-	ret
-
-	.p2align 4
-L(first_vec_x2):
-	tzcntl	%eax, %eax
-	/* Safe to use 32 bit instructions as these are only called for
-	   size = [1, 159].  */
-# ifdef USE_AS_STRNLEN
-	/* 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
+	bsf	%VRAX, %VRAX
 	ret
 
-	.p2align 4
-L(first_vec_x3):
-	tzcntl	%eax, %eax
-	/* Safe to use 32 bit instructions as these are only called for
-	   size = [1, 159].  */
-# ifdef USE_AS_STRNLEN
-	/* Use ecx which was computed earlier to compute correct value.
-	 */
-	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
-
-	.p2align 4
+	.p2align 4,, 8
 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
-	/* 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
+	bsf	%VRAX, %VRAX
+	subl	%ecx, %edi
+	CHAR_SIZE_SHIFT_REG (edi)
 	leal	(CHAR_PER_VEC * 4)(%rdi, %rax), %eax
-# endif
 	ret
 
-	.p2align 5
+
+
+	/* Aligned more for strnlen compares remaining length vs 2 *
+	   CHAR_PER_VEC, 4 * CHAR_PER_VEC, and 8 * CHAR_PER_VEC before
+	   going to the loop.  */
+	.p2align 4,, 10
 L(aligned_more):
-	movq	%rdi, %rdx
-	/* Align data to VEC_SIZE.  */
-	andq	$-(VEC_SIZE), %rdi
+	movq	%rdi, %rcx
+	andq	$(VEC_SIZE * -1), %rdi
 L(cross_page_continue):
-	/* Check the first 4 * VEC_SIZE.  Only one VEC_SIZE at a time
-	   since data is only aligned to VEC_SIZE.  */
-# 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
+	/* Remaining length >= 2 * CHAR_PER_VEC so do VEC0/VEC1 without
+	   rechecking bounds.  */
+	VPCMPEQ	(VEC_SIZE * 1)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRAX
+	test	%VRAX, %VRAX
 	jnz	L(first_vec_x1)
 
-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMZERO, %k0
-	kmovd	%k0, %eax
-	test	%eax, %eax
+	VPCMPEQ	(VEC_SIZE * 2)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRAX
+	test	%VRAX, %VRAX
 	jnz	L(first_vec_x2)
 
-	VPCMP	$0, (VEC_SIZE * 3)(%rdi), %YMMZERO, %k0
-	kmovd	%k0, %eax
-	testl	%eax, %eax
+	VPCMPEQ	(VEC_SIZE * 3)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRAX
+	test	%VRAX, %VRAX
 	jnz	L(first_vec_x3)
 
-	VPCMP	$0, (VEC_SIZE * 4)(%rdi), %YMMZERO, %k0
-	kmovd	%k0, %eax
-	testl	%eax, %eax
+	VPCMPEQ	(VEC_SIZE * 4)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRAX
+	test	%VRAX, %VRAX
 	jnz	L(first_vec_x4)
 
-	addq	$VEC_SIZE, %rdi
-# ifdef USE_AS_STRNLEN
-	/* 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.  */
+	subq	$(VEC_SIZE * -1), %rdi
+
+# if CHAR_PER_VEC == 64
+	/* No partial register stalls on processors that we use evex512
+	   on and this saves code size.  */
+	xorb	%dil, %dil
+# else
 	andq	$-(VEC_SIZE * 4), %rdi
+# endif
+
+
 
 	/* Compare 4 * VEC at a time forward.  */
 	.p2align 4
 L(loop_4x_vec):
-	/* 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
+	VMOVA	(VEC_SIZE * 4)(%rdi), %VMM(1)
+	VPMINU	(VEC_SIZE * 5)(%rdi), %VMM(1), %VMM(2)
+	VMOVA	(VEC_SIZE * 6)(%rdi), %VMM(3)
+	VPMINU	(VEC_SIZE * 7)(%rdi), %VMM(3), %VMM(4)
+	VPTESTN	%VMM(2), %VMM(2), %k0
+	VPTESTN	%VMM(4), %VMM(4), %k2
 
-	VPCMP	$0, %YMM2, %YMMZERO, %k0
-	VPCMP	$0, %YMM4, %YMMZERO, %k1
 	subq	$-(VEC_SIZE * 4), %rdi
-	kortestd	%k0, %k1
+	KORTEST %k0, %k2
 	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)
+	VPTESTN	%VMM(1), %VMM(1), %k1
+	KMOV	%k1, %VRAX
+	test	%VRAX, %VRAX
+	jnz	L(first_vec_x0)
 
-	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
-
-
-# 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):
-	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(last_vec_x1_check)
+	KMOV	%k0, %VRAX
+	test	%VRAX, %VRAX
+	jnz	L(first_vec_x1)
 
-	/* Check the end of data.  */
-	subl	$CHAR_PER_VEC, %esi
-	jb	L(max)
+	VPTESTN	%VMM(3), %VMM(3), %k0
 
-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMZERO, %k0
-	kmovd	%k0, %eax
-	tzcntl	%eax, %eax
-	/* Check the end of data.  */
-	cmpl	%eax, %esi
-	jb	L(max)
-
-	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
+# if CHAR_PER_VEC == 64
+	KMOV	%k0, %VRAX
+	test	%VRAX, %VRAX
+	jnz	L(first_vec_x2)
+	KMOV	%k2, %VRAX
 # else
-	kunpckdq	%k0, %k1, %k0
-	kmovq	%k0, %rax
-	tzcntq	%rax, %rax
+	/* We can only combine last 2x VEC masks if CHAR_PER_VEC <= 32.
+	 */
+	kmovd	%k2, %edx
+	kmovd	%k0, %eax
+	salq	$CHAR_PER_VEC, %rdx
+	orq	%rdx, %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
-	/* NB: Divide bytes by 4 to get the wchar_t count.  */
-	sarq	$2, %rdi
-#  endif
-	leaq	(CHAR_PER_VEC)(%rdi, %rax), %rax
+	/* first_vec_x3 for strlen-ZMM and first_vec_x2 for strlen-YMM.
+	 */
+	.p2align 4,, 2
+L(FALLTHROUGH_RETURN_LBL):
+	bsfq	%rax, %rax
+	subq	%rcx, %rdi
+	CHAR_SIZE_SHIFT_REG (rdi)
+	leaq	(FALLTHROUGH_RETURN_OFFSET)(%rdi, %rax), %rax
 	ret
 
-	.p2align 4
-L(last_4x_vec):
-	/* Test first 2x VEC normally.  */
-	testl	%eax, %eax
-	jnz	L(last_vec_x1)
-
-	VPCMP	$0, (VEC_SIZE * 2)(%rdi), %YMMZERO, %k0
-	kmovd	%k0, %eax
-	testl	%eax, %eax
-	jnz	L(last_vec_x2)
-
-	/* 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(last_vec_x3)
-
-	/* 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
-	/* Check the end of data.  */
-	cmpl	%eax, %esi
-	jb	L(max_end)
-
-	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 * 4)(%rdi, %rax), %rax
+	.p2align 4,, 8
+L(first_vec_x0):
+	bsf	%VRAX, %VRAX
+	sub	%rcx, %rdi
+	CHAR_SIZE_SHIFT_REG (rdi)
+	addq	%rdi, %rax
 	ret
 
-	.p2align 4
-L(last_vec_x1):
-	tzcntl	%eax, %eax
-	subq	%rdx, %rdi
-#  ifdef USE_AS_WCSLEN
-	/* NB: Divide bytes by 4 to get the wchar_t count.  */
-	sarq	$2, %rdi
-#  endif
+	.p2align 4,, 10
+L(first_vec_x1):
+	bsf	%VRAX, %VRAX
+	sub	%rcx, %rdi
+	CHAR_SIZE_SHIFT_REG (rdi)
 	leaq	(CHAR_PER_VEC)(%rdi, %rax), %rax
 	ret
 
-	.p2align 4
-L(last_vec_x2):
-	tzcntl	%eax, %eax
-	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
-
-	.p2align 4
-L(last_vec_x3):
-	tzcntl	%eax, %eax
-	subl	$(CHAR_PER_VEC * 2), %esi
-	/* Check the end of data.  */
-	cmpl	%eax, %esi
-	jb	L(max_end)
-	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 * 3)(%rdi, %rax), %rax
-	ret
-L(max_end):
-	movq	%r8, %rax
+	.p2align 4,, 10
+	/* first_vec_x2 for strlen-ZMM and first_vec_x3 for strlen-YMM.
+	 */
+L(TAIL_RETURN_LBL):
+	bsf	%VRAX, %VRAX
+	sub	%VRCX, %VRDI
+	CHAR_SIZE_SHIFT_REG (VRDI)
+	lea	(TAIL_RETURN_OFFSET)(%rdi, %rax), %VRAX
 	ret
-# endif
 
-	/* Cold case for crossing page with first load.	 */
-	.p2align 4
+	.p2align 4,, 8
 L(cross_page_boundary):
-	movq	%rdi, %rdx
+	movq	%rdi, %rcx
 	/* Align data to VEC_SIZE.  */
 	andq	$-VEC_SIZE, %rdi
-	VPCMP	$0, (%rdi), %YMMZERO, %k0
-	kmovd	%k0, %eax
-	/* Remove the leading bytes.  */
+
+	VPCMPEQ	(%rdi), %VZERO, %k0
+
+	KMOV	%k0, %VRAX
 # ifdef USE_AS_WCSLEN
-	/* 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
-	/* SHIFT_REG is ecx for USE_AS_WCSLEN and edx otherwise.  */
-	sarxl	%SHIFT_REG, %eax, %eax
+	movl	%ecx, %edx
+	shrl	$2, %edx
+	andl	$(CHAR_PER_VEC - 1), %edx
+	shrx	%edx, %eax, %eax
 	testl	%eax, %eax
-# ifndef USE_AS_STRNLEN
-	jz	L(cross_page_continue)
-	tzcntl	%eax, %eax
-	ret
 # 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
-L(cross_page_less_vec):
-	tzcntl	%eax, %eax
-	/* Select min of length and position of first null.  */
-	cmpq	%rax, %rsi
-	cmovb	%esi, %eax
-	ret
+	shr	%cl, %VRAX
 # endif
+	jz	L(cross_page_continue)
+	bsf	%VRAX, %VRAX
+	ret
 
 END (STRLEN)
 #endif
diff --git a/sysdeps/x86_64/multiarch/strnlen-evex.S b/sysdeps/x86_64/multiarch/strnlen-evex.S
index 64a9fc2606..443a32a749 100644
--- a/sysdeps/x86_64/multiarch/strnlen-evex.S
+++ b/sysdeps/x86_64/multiarch/strnlen-evex.S
@@ -1,8 +1,423 @@
-#ifndef STRNLEN
-# define STRNLEN __strnlen_evex
-#endif
+/* strnlen/wcsnlen optimized with 256-bit EVEX instructions.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <isa-level.h>
+#include <sysdep.h>
+
+#if ISA_SHOULD_BUILD (4)
+
+# ifndef VEC_SIZE
+#  include "x86-evex256-vecs.h"
+# endif
+
+
+# ifndef STRNLEN
+#  define STRNLEN	__strnlen_evex
+# endif
+
+# ifdef USE_AS_WCSLEN
+#  define VPCMPEQ	vpcmpeqd
+#  define VPCMPNEQ	vpcmpneqd
+#  define VPTESTN	vptestnmd
+#  define VPTEST	vptestmd
+#  define VPMINU	vpminud
+#  define CHAR_SIZE	4
+
+# else
+#  define VPCMPEQ	vpcmpeqb
+#  define VPCMPNEQ	vpcmpneqb
+#  define VPTESTN	vptestnmb
+#  define VPTEST	vptestmb
+#  define VPMINU	vpminub
+#  define CHAR_SIZE	1
+
+#  define REG_WIDTH	VEC_SIZE
+# endif
+
+# define CHAR_PER_VEC	(VEC_SIZE / CHAR_SIZE)
+
+# include "reg-macros.h"
+
+# if CHAR_PER_VEC == 32
+#  define SUB_SHORT(imm, reg)	subb $(imm), %VGPR_SZ(reg, 8)
+# else
+#  define SUB_SHORT(imm, reg)	subl $(imm), %VGPR_SZ(reg, 32)
+# endif
+
+
+
+# if CHAR_PER_VEC == 64
+#  define FALLTHROUGH_RETURN_OFFSET	(CHAR_PER_VEC * 3)
+# else
+#  define FALLTHROUGH_RETURN_OFFSET	(CHAR_PER_VEC * 2)
+# endif
+
+
+# define XZERO	VMM_128(0)
+# define VZERO	VMM(0)
+# define PAGE_SIZE	4096
+
+	.section SECTION(.text), "ax", @progbits
+ENTRY_P2ALIGN (STRNLEN, 6)
+	/* Check zero length.  */
+	test	%RSI_LP, %RSI_LP
+	jz	L(zero)
+# ifdef __ILP32__
+	/* Clear the upper 32 bits.  */
+	movl	%esi, %esi
+# endif
+
+	movl	%edi, %eax
+	vpxorq	%XZERO, %XZERO, %XZERO
+	andl	$(PAGE_SIZE - 1), %eax
+	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.  */
+	VPCMPEQ	(%rdi), %VZERO, %k0
+
+	KMOV	%k0, %VRCX
+	movq	%rsi, %rax
+
+	/* If src (rcx) is zero, bsf does not change the result.  NB:
+	   Must use 64-bit bsf here so that upper bits of len are not
+	   cleared.  */
+	bsfq	%rcx, %rax
+	/* If rax > CHAR_PER_VEC then rcx must have been zero (no null
+	   CHAR) and rsi must be > CHAR_PER_VEC.  */
+	cmpq	$CHAR_PER_VEC, %rax
+	ja	L(more_1x_vec)
+	/* Check if first match in bounds.  */
+	cmpq	%rax, %rsi
+	cmovb	%esi, %eax
+	ret
+
+
+# if CHAR_PER_VEC != 32
+	.p2align 4,, 2
+L(zero):
+L(max_0):
+	movl	%esi, %eax
+	ret
+# endif
+
+	/* Aligned more for strnlen compares remaining length vs 2 *
+	   CHAR_PER_VEC, 4 * CHAR_PER_VEC, and 8 * CHAR_PER_VEC before
+	   going to the loop.  */
+	.p2align 4,, 10
+L(more_1x_vec):
+L(cross_page_continue):
+	/* Compute number of words checked after aligning.  */
+# ifdef USE_AS_WCSLEN
+	/* Need to compute directly for wcslen as CHAR_SIZE * rsi can
+	   overflow.  */
+	movq	%rdi, %rax
+	andq	$(VEC_SIZE * -1), %rdi
+	subq	%rdi, %rax
+	sarq	$2, %rax
+	leaq	-(CHAR_PER_VEC * 1)(%rax, %rsi), %rax
+# else
+	leaq	(VEC_SIZE * -1)(%rsi, %rdi), %rax
+	andq	$(VEC_SIZE * -1), %rdi
+	subq	%rdi, %rax
+# endif
+
+
+	VPCMPEQ	VEC_SIZE(%rdi), %VZERO, %k0
+
+	cmpq	$(CHAR_PER_VEC * 2), %rax
+	ja	L(more_2x_vec)
+
+L(last_2x_vec_or_less):
+	KMOV	%k0, %VRDX
+	test	%VRDX, %VRDX
+	jnz	L(last_vec_check)
+
+	/* Check the end of data.  */
+	SUB_SHORT (CHAR_PER_VEC, rax)
+	jbe	L(max_0)
+	VPCMPEQ	(VEC_SIZE * 2)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRDX
+	test	%VRDX, %VRDX
+	jz	L(max_0)
+	/* Best place for LAST_VEC_CHECK if ZMM.  */
+	.p2align 4,, 8
+L(last_vec_check):
+	bsf	%VRDX, %VRDX
+	sub	%eax, %edx
+	lea	(%rsi, %rdx), %eax
+	cmovae	%esi, %eax
+	ret
+
+# if CHAR_PER_VEC == 32
+	.p2align 4,, 2
+L(zero):
+L(max_0):
+	movl	%esi, %eax
+	ret
+# endif
+
+	.p2align 4,, 8
+L(last_4x_vec_or_less):
+	addl	$(CHAR_PER_VEC * -4), %eax
+	VPCMPEQ	(VEC_SIZE * 5)(%rdi), %VZERO, %k0
+	subq	$(VEC_SIZE * -4), %rdi
+	cmpl	$(CHAR_PER_VEC * 2), %eax
+	jbe	L(last_2x_vec_or_less)
+
+	.p2align 4,, 6
+L(more_2x_vec):
+	/* Remaining length >= 2 * CHAR_PER_VEC so do VEC0/VEC1 without
+	   rechecking bounds.  */
 
-#define USE_AS_STRNLEN 1
-#define STRLEN	STRNLEN
+	KMOV	%k0, %VRDX
 
-#include "strlen-evex.S"
+	test	%VRDX, %VRDX
+	jnz	L(first_vec_x1)
+
+	VPCMPEQ	(VEC_SIZE * 2)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRDX
+	test	%VRDX, %VRDX
+	jnz	L(first_vec_x2)
+
+	cmpq	$(CHAR_PER_VEC * 4), %rax
+	ja	L(more_4x_vec)
+
+
+	VPCMPEQ	(VEC_SIZE * 3)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRDX
+	addl	$(CHAR_PER_VEC * -2), %eax
+	test	%VRDX, %VRDX
+	jnz	L(last_vec_check)
+
+	subl	$(CHAR_PER_VEC), %eax
+	jbe	L(max_1)
+
+	VPCMPEQ	(VEC_SIZE * 4)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRDX
+
+	test	%VRDX, %VRDX
+	jnz	L(last_vec_check)
+L(max_1):
+	movl	%esi, %eax
+	ret
+
+	.p2align 4,, 3
+L(first_vec_x2):
+# if VEC_SIZE == 64
+	/* If VEC_SIZE == 64 we can fit logic for full return label in
+	   spare bytes before next cache line.  */
+	bsf	%VRDX, %VRDX
+	sub	%eax, %esi
+	leal	(CHAR_PER_VEC * 1)(%rsi, %rdx), %eax
+	ret
+	.p2align 4,, 6
+# else
+	addl	$CHAR_PER_VEC, %esi
+# endif
+L(first_vec_x1):
+	bsf	%VRDX, %VRDX
+	sub	%eax, %esi
+	leal	(CHAR_PER_VEC * 0)(%rsi, %rdx), %eax
+	ret
+
+
+	.p2align 4,, 6
+L(first_vec_x4):
+# if VEC_SIZE == 64
+	/* If VEC_SIZE == 64 we can fit logic for full return label in
+	   spare bytes before next cache line.  */
+	bsf	%VRDX, %VRDX
+	sub	%eax, %esi
+	leal	(CHAR_PER_VEC * 3)(%rsi, %rdx), %eax
+	ret
+	.p2align 4,, 6
+# else
+	addl	$CHAR_PER_VEC, %esi
+# endif
+L(first_vec_x3):
+	bsf	%VRDX, %VRDX
+	sub	%eax, %esi
+	leal	(CHAR_PER_VEC * 2)(%rsi, %rdx), %eax
+	ret
+
+	.p2align 4,, 5
+L(more_4x_vec):
+	VPCMPEQ	(VEC_SIZE * 3)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRDX
+	test	%VRDX, %VRDX
+	jnz	L(first_vec_x3)
+
+	VPCMPEQ	(VEC_SIZE * 4)(%rdi), %VZERO, %k0
+	KMOV	%k0, %VRDX
+	test	%VRDX, %VRDX
+	jnz	L(first_vec_x4)
+
+	/* Check if at last VEC_SIZE * 4 length before aligning for the
+	   loop.  */
+	cmpq	$(CHAR_PER_VEC * 8), %rax
+	jbe	L(last_4x_vec_or_less)
+
+
+	/* Compute number of words checked after aligning.  */
+# ifdef USE_AS_WCSLEN
+	/* Need to compute directly for wcslen as CHAR_SIZE * rsi can
+	   overflow.  */
+	leaq	(VEC_SIZE * -3)(%rdi), %rdx
+# else
+	leaq	(VEC_SIZE * -3)(%rdi, %rax), %rax
+# endif
+
+	subq	$(VEC_SIZE * -1), %rdi
+
+	/* Align data to VEC_SIZE * 4.  */
+# if VEC_SIZE == 64
+	/* Saves code size.  No evex512 processor has partial register
+	   stalls.  If that change this can be replaced with `andq
+	   $-(VEC_SIZE * 4), %rdi`.  */
+	xorb	%dil, %dil
+# else
+	andq	$-(VEC_SIZE * 4), %rdi
+# endif
+
+# ifdef USE_AS_WCSLEN
+	subq	%rdi, %rdx
+	sarq	$2, %rdx
+	addq	%rdx, %rax
+# else
+	subq	%rdi, %rax
+# endif
+	/* Compare 4 * VEC at a time forward.  */
+	.p2align 4,, 11
+L(loop_4x_vec):
+	VMOVA	(VEC_SIZE * 4)(%rdi), %VMM(1)
+	VPMINU	(VEC_SIZE * 5)(%rdi), %VMM(1), %VMM(2)
+	VMOVA	(VEC_SIZE * 6)(%rdi), %VMM(3)
+	VPMINU	(VEC_SIZE * 7)(%rdi), %VMM(3), %VMM(4)
+	VPTESTN	%VMM(2), %VMM(2), %k0
+	VPTESTN	%VMM(4), %VMM(4), %k2
+	subq	$-(VEC_SIZE * 4), %rdi
+	/* Break if at end of length.  */
+	subq	$(CHAR_PER_VEC * 4), %rax
+	jbe	L(loop_len_end)
+
+
+	KORTEST %k0, %k2
+	jz	L(loop_4x_vec)
+
+
+L(loop_last_4x_vec):
+	movq	%rsi, %rcx
+	subq	%rax, %rsi
+	VPTESTN	%VMM(1), %VMM(1), %k1
+	KMOV	%k1, %VRDX
+	test	%VRDX, %VRDX
+	jnz	L(last_vec_x0)
+
+	KMOV	%k0, %VRDX
+	test	%VRDX, %VRDX
+	jnz	L(last_vec_x1)
+
+	VPTESTN	%VMM(3), %VMM(3), %k0
+
+	/* Seperate logic for VEC_SIZE == 64 and VEC_SIZE == 32 for
+	   returning last 2x VEC. For VEC_SIZE == 64 we test each VEC
+	   individually, for VEC_SIZE == 32 we combine them in a single
+	   64-bit GPR.  */
+# if CHAR_PER_VEC == 64
+	KMOV	%k0, %VRDX
+	test	%VRDX, %VRDX
+	jnz	L(last_vec_x2)
+	KMOV	%k2, %VRDX
+# else
+	/* We can only combine last 2x VEC masks if CHAR_PER_VEC <= 32.
+	 */
+	kmovd	%k2, %edx
+	kmovd	%k0, %eax
+	salq	$CHAR_PER_VEC, %rdx
+	orq	%rax, %rdx
+# endif
+
+	/* first_vec_x3 for strlen-ZMM and first_vec_x2 for strlen-YMM.
+	 */
+	bsfq	%rdx, %rdx
+	leaq	(FALLTHROUGH_RETURN_OFFSET - CHAR_PER_VEC * 4)(%rsi, %rdx), %rax
+	cmpq	%rax, %rcx
+	cmovb	%rcx, %rax
+	ret
+
+	/* Handle last 4x VEC after loop. All VECs have been loaded.  */
+	.p2align 4,, 4
+L(loop_len_end):
+	KORTEST %k0, %k2
+	jnz	L(loop_last_4x_vec)
+	movq	%rsi, %rax
+	ret
+
+
+# if CHAR_PER_VEC == 64
+	/* Since we can't combine the last 2x VEC for VEC_SIZE == 64
+	   need return label for it.  */
+	.p2align 4,, 8
+L(last_vec_x2):
+	bsf	%VRDX, %VRDX
+	leaq	(CHAR_PER_VEC * -2)(%rsi, %rdx), %rax
+	cmpq	%rax, %rcx
+	cmovb	%rcx, %rax
+	ret
+# endif
+
+
+	.p2align 4,, 10
+L(last_vec_x1):
+	addq	$CHAR_PER_VEC, %rsi
+L(last_vec_x0):
+	bsf	%VRDX, %VRDX
+	leaq	(CHAR_PER_VEC * -4)(%rsi, %rdx), %rax
+	cmpq	%rax, %rcx
+	cmovb	%rcx, %rax
+	ret
+
+
+	.p2align 4,, 8
+L(cross_page_boundary):
+	/* Align data to VEC_SIZE.  */
+	movq	%rdi, %rcx
+	andq	$-VEC_SIZE, %rcx
+	VPCMPEQ	(%rcx), %VZERO, %k0
+
+	KMOV	%k0, %VRCX
+# ifdef USE_AS_WCSLEN
+	shrl	$2, %eax
+	andl	$(CHAR_PER_VEC - 1), %eax
+# endif
+	shrx	%VRAX, %VRCX, %VRCX
+
+	negl	%eax
+	andl	$(CHAR_PER_VEC - 1), %eax
+	movq	%rsi, %rdx
+	bsf	%VRCX, %VRDX
+	cmpq	%rax, %rdx
+	ja	L(cross_page_continue)
+	movl	%edx, %eax
+	cmpq	%rdx, %rsi
+	cmovb	%esi, %eax
+	ret
+END (STRNLEN)
+#endif
diff --git a/sysdeps/x86_64/multiarch/wcsnlen-evex.S b/sysdeps/x86_64/multiarch/wcsnlen-evex.S
index e2aad94c1e..57a7e93fbf 100644
--- a/sysdeps/x86_64/multiarch/wcsnlen-evex.S
+++ b/sysdeps/x86_64/multiarch/wcsnlen-evex.S
@@ -2,8 +2,7 @@
 # define WCSNLEN	__wcsnlen_evex
 #endif
 
-#define STRLEN	WCSNLEN
+#define STRNLEN	WCSNLEN
 #define USE_AS_WCSLEN 1
-#define USE_AS_STRNLEN 1
 
-#include "strlen-evex.S"
+#include "strnlen-evex.S"