[PATCH] AArch64: Add SVE2 strchr

Add an SVE2 strchr implementation and ifunc support.  Use MATCH to check for
both the input char and NUL.  Performance of bench-strchr improves ~28% on
Neoverse V2.

---

diff --git a/sysdeps/aarch64/multiarch/Makefile b/sysdeps/aarch64/multiarch/Makefile
index 38952655b1c14ac34a7bfdace01291e2802bd746..9f202512f1e32ddc0177d030bf295d3b7e202c1c 100644
--- a/sysdeps/aarch64/multiarch/Makefile
+++ b/sysdeps/aarch64/multiarch/Makefile
@@ -16,6 +16,8 @@ sysdep_routines += \
   memset_oryon1 \
   memset_sve_zva64 \
   memset_zva64 \
+  strchr_generic \
+  strchr_sve2 \
   strlen_asimd \
   strlen_generic \
 # sysdep_routines
diff --git a/sysdeps/aarch64/multiarch/dl-symbol-redir-ifunc.h b/sysdeps/aarch64/multiarch/dl-symbol-redir-ifunc.h
index 0910e321d24d84db951cf498c3e883c2cfdd01f5..50b2581455c94dc2bd38f8e5ba9a357d1b79e89f 100644
--- a/sysdeps/aarch64/multiarch/dl-symbol-redir-ifunc.h
+++ b/sysdeps/aarch64/multiarch/dl-symbol-redir-ifunc.h
@@ -22,6 +22,7 @@
 asm ("memset = __memset_generic");
 asm ("strlen = __strlen_generic");
 #ifndef SHARED
+asm ("strchr = __strchr_generic");
 asm ("memcpy = __memcpy_generic");
 asm ("memmove = __memmove_generic");
 asm ("memcmp = __memcmp_generic");
diff --git a/sysdeps/aarch64/multiarch/ifunc-impl-list.c b/sysdeps/aarch64/multiarch/ifunc-impl-list.c
index d43f6b58ee075c815b93ab2f42735e7e9f315d32..a0c93147c532d935d562a66ac67ebaa5326dd3bd 100644
--- a/sysdeps/aarch64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/aarch64/multiarch/ifunc-impl-list.c
@@ -33,7 +33,6 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 
   INIT_ARCH ();
 
-  /* Support sysdeps/aarch64/multiarch/memcmp.c, memcpy.c, memmove.c and memset.c.  */
   IFUNC_IMPL (i, name, memcmp,
 	      IFUNC_IMPL_ADD (array, i, memcmp, sve, __memcmp_kunpeng950)
 	      IFUNC_IMPL_ADD (array, i, memcmp, 1, __memcmp_generic))
@@ -61,6 +60,8 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   IFUNC_IMPL (i, name, strlen,
 	      IFUNC_IMPL_ADD (array, i, strlen, !mte, __strlen_asimd)
 	      IFUNC_IMPL_ADD (array, i, strlen, 1, __strlen_generic))
-
+  IFUNC_IMPL (i, name, strchr,
+	      IFUNC_IMPL_ADD (array, i, strchr, sve2 && !mte, __strchr_sve2)
+	      IFUNC_IMPL_ADD (array, i, strchr, 1, __strchr_generic))
   return 0;
 }
diff --git a/sysdeps/aarch64/multiarch/strchr.c b/sysdeps/aarch64/multiarch/strchr.c
new file mode 100644
index 0000000000000000000000000000000000000000..12f4e10bbe034ab462a4e578c69fd1d9b4afd9ed
--- /dev/null
+++ b/sysdeps/aarch64/multiarch/strchr.c
@@ -0,0 +1,38 @@
+/* Multiple versions of strchr. AArch64 version.
+   Copyright (C) 2026 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/>.  */
+
+/* Define multiple versions only for the definition in libc.  */
+
+#if IS_IN (libc)
+/* Redefine strchr so that the compiler won't complain about the type
+   mismatch with the IFUNC selector in strong_alias, below.  */
+# undef strchr
+# define strchr __redirect_strchr
+# include <string.h>
+# include <init-arch.h>
+
+extern __typeof (__redirect_strchr) __libc_strchr;
+
+extern __typeof (__redirect_strchr) __strchr_generic attribute_hidden;
+extern __typeof (__redirect_strchr) __strchr_sve2 attribute_hidden;
+
+libc_ifunc (__libc_strchr, (sve2 && !mte ? __strchr_sve2 : __strchr_generic));
+
+# undef strchr
+strong_alias (__libc_strchr, strchr);
+#endif
diff --git a/sysdeps/aarch64/multiarch/strchr_generic.S b/sysdeps/aarch64/multiarch/strchr_generic.S
new file mode 100644
index 0000000000000000000000000000000000000000..1fad64f9d98c5ec77346e1efa0d2bc6787c94420
--- /dev/null
+++ b/sysdeps/aarch64/multiarch/strchr_generic.S
@@ -0,0 +1,35 @@
+/* A Generic Optimized strchr implementation for AArch64.
+   Copyright (C) 2026 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 <sysdep.h>
+
+#if IS_IN (libc)
+
+# define STRCHR __strchr_generic
+
+/* Do not hide the generic version of strchr, we use it internally.  */
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(name)
+
+# ifdef SHARED
+/* It doesn't make sense to send libc-internal strchr calls through a PLT. */
+	.globl __GI_strchr; __GI_strchr = __strchr_generic
+# endif
+#endif
+
+#include "../strchr.S"
diff --git a/sysdeps/aarch64/multiarch/strchr_sve2.S b/sysdeps/aarch64/multiarch/strchr_sve2.S
new file mode 100644
index 0000000000000000000000000000000000000000..4f24c65e2915a14286a0ea922ae8325bde3561c1
--- /dev/null
+++ b/sysdeps/aarch64/multiarch/strchr_sve2.S
@@ -0,0 +1,116 @@
+/* Optimized strchr for SVE2.
+   Copyright (C) 2026 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 <sysdep.h>
+
+/* Assumptions:
+ *
+ * SVE2, unaligned accesses.
+ *
+ */
+
+.arch armv9-a+sve2
+
+#if defined (BUILD_STRCHRNUL)
+#define STRCHR  __strchrnul_sve2
+#else
+#define STRCHR  __strchr_sve2
+#endif
+
+#define chrin		w1		// int chr.
+#define result		x0		// Return.
+
+#define src		x0		// Current data pointer.
+#define	vlalign		x2		// Alignment mask.
+#define	tmp		x3
+
+#define zdata		z0		// Data.
+#define zchr_nul	z1		// chr and NUL data for search.
+
+#define pall		p0		// All active predicate.
+#define pchr_nul	p1		// chr and NUL search result.
+#define pchr		p2		// chr search result.
+#define psrc		p3		// Mask of chars before srcin.
+#define pfirst		p4		// First found.
+
+ENTRY (STRCHR)
+	ptrue	pall.b
+	and	chrin, chrin, 0xff	// Set zeros after first byte.
+	dup	zchr_nul.h, chrin	// Initialize chr and NUL for search.
+
+	and	tmp, src, 0xfff		// Check for pagecross of 2VL reads.
+	incb	tmp, all, mul #2
+	tbnz	tmp, 12, L(pagecross)
+
+	ld1b	{zdata.b}, pall/z, [src]
+	match	pchr_nul.b, pall/z, zdata.b, zchr_nul.b
+	b.any	L(firstmatch)
+	ld1b	{zdata.b}, pall/z, [src, 1, mul vl]
+	match	pchr_nul.b, pall/z, zdata.b, zchr_nul.b
+	b.none	L(loop_start)
+	incb	src
+L(firstmatch):
+	brkb	pfirst.b, pall/z, pchr_nul.b	// Find first element.
+	incp	src, pfirst.b			// Increment by element index.
+#if !defined (BUILD_STRCHRNUL)
+	cbz	chrin, 1f			// Special case NUL chrin.
+	cmpne	pchr.b, pchr_nul/z, zdata.b, 0	// Matched chrin?
+	csel	result, src, xzr, first		// If it is NUL, return null.
+1:	ret
+	nop
+#else
+	ret
+#endif
+L(loop_start):
+	mov	vlalign, 0
+	decb	vlalign
+	and	src, src, vlalign		// Align src to VL.
+L(loop):
+	ld1b	{zdata.b}, pall/z, [src, 2, mul vl]
+	incb	src, all, mul #2
+	match	pchr_nul.b, pall/z, zdata.b, zchr_nul.b
+	b.any	L(loop_end)
+L(loop2):
+	ld1b	{zdata.b}, pall/z, [src, 1, mul vl]
+	match	pchr_nul.b, pall/z, zdata.b, zchr_nul.b
+	b.none	L(loop)
+	incb	src
+L(loop_end):
+	brkb	pfirst.b, pall/z, pchr_nul.b	// Find first element.
+	incp	src, pfirst.b			// Increment by element index.
+#if !defined (BUILD_STRCHRNUL)
+	cbz	chrin, 2f			// Special case NUL chrin.
+	cmpne	pchr.b, pchr_nul/z, zdata.b, 0	// Matched chrin?
+	csel	result, src, xzr, first		// If it is NUL, return null.
+#endif
+2:	ret
+
+	.p2align 3
+L(pagecross):
+	mov	vlalign, 0
+	decb	vlalign
+	orn	tmp, src, vlalign		// Find end of VL aligned src.
+	whilels	psrc.b, src, tmp		// Mask off elements.
+	ld1b	{zdata.b}, psrc/z, [src]
+	match	pchr_nul.b, psrc/z, zdata.b, zchr_nul.b
+	b.any	L(firstmatch)
+	and	src, src, vlalign		// Align src to VL.
+	b	L(loop2)
+
+END (STRCHR)
diff --git a/sysdeps/aarch64/strchr.S b/sysdeps/aarch64/strchr.S
index e793fa92f15b63495eab94c83534c5830258bfec..daa28acbfc8b278897d47ec403dc945eb3ba3555 100644
--- a/sysdeps/aarch64/strchr.S
+++ b/sysdeps/aarch64/strchr.S
@@ -26,6 +26,10 @@
  * MTE compatible.
  */
 
+#ifndef STRCHR
+# define STRCHR strchr
+#endif
+
 #define srcin		x0
 #define chrin		w1
 #define result		x0
@@ -51,7 +55,7 @@
    zeroes gives the position of the matching byte if it is a multiple of 4.
    If it is not a multiple of 4, there was no match.  */
 
-ENTRY (strchr)
+ENTRY (STRCHR)
 	bic	src, srcin, 15
 	dup	vrepchr.16b, chrin
 	ld1	{vdata.16b}, [src]
@@ -109,6 +113,6 @@ L(end):
 	csel	result, result, xzr, eq
 	ret
 
-END (strchr)
-libc_hidden_builtin_def (strchr)
-weak_alias (strchr, index)
+END (STRCHR)
+libc_hidden_builtin_def (STRCHR)
+weak_alias (STRCHR, index)