riscv: Add RVV strchr for both multiarch and non-multiarch builds

This patch adds an RVV-optimized implementation of strchr for RISC-V and
enables it for both multiarch (IFUNC) and non-multiarch builds.

The implementation integrates Hau Hsu's 2023 RVV work under a unified
ifunc-based framework. A vectorized version (__strchr_vector) is added
alongside the generic fallback (__strchr_generic). The runtime resolver
selects the RVV variant when RISCV_HWPROBE_KEY_IMA_EXT_0 reports vector
support (RVV).

Currently, the resolver still selects the RVV variant even when the RVV
extension is disabled via prctl(). As a consequence, any process that
has RVV disabled via prctl() will receive SIGILL when calling strchr().

Co-authored-by: Hau Hsu <hau.hsu@sifive.com>
Co-authored-by: Jerry Shih <jerry.shih@sifive.com>
Signed-off-by: Yao Zihong <zihong.plct@isrc.iscas.ac.cn>
Reviewed-by: Peter Bergner <bergner@tenstorrent.com>

diff --git a/sysdeps/riscv/multiarch/strchr-generic.c b/sysdeps/riscv/multiarch/strchr-generic.c
new file mode 100644 (file)
index 0000000..301b7dc
--- /dev/null
+++ b/sysdeps/riscv/multiarch/strchr-generic.c
@@ -0,0 +1,24 @@
+/* Re-include the default strchr implementation.
+   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 <string.h>
+
+#if IS_IN(libc)
+# define STRCHR __strchr_generic
+# include <string/strchr.c>
+#endif

diff --git a/sysdeps/riscv/multiarch/strchr-vector.S b/sysdeps/riscv/multiarch/strchr-vector.S
new file mode 100644 (file)
index 0000000..c55a1f9
--- /dev/null
+++ b/sysdeps/riscv/multiarch/strchr-vector.S
@@ -0,0 +1,26 @@
+/* Re-include the RISC-V RVV based strchr implementation.
+   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/>.  */
+
+#if IS_IN(libc)
+# define STRCHR __strchr_vector
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(name)
+# undef weak_alias
+# define weak_alias(name, alias)
+# include <sysdeps/riscv/rvv/strchr.S>
+#endif

diff --git a/sysdeps/riscv/rvv/strchr.S b/sysdeps/riscv/rvv/strchr.S
new file mode 100644 (file)
index 0000000..2fa95c3
--- /dev/null
+++ b/sysdeps/riscv/rvv/strchr.S
@@ -0,0 +1,65 @@
+/* RISC-V RVV based strchr.
+   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>
+#include <sys/asm.h>
+
+#ifndef STRCHR
+# define STRCHR strchr
+#endif
+
+#define str a0
+#define ch a1
+#define end_offset a2
+#define ch_offset a3
+#define temp1 a4
+#define temp2 a5
+#define cur_vl a6
+#define ivl t0
+
+#define ELEM_LMUL_SETTING m1
+#define vstr v0
+#define vmask_end v8
+#define vmask_ch v9
+
+ENTRY (STRCHR)
+.option push
+.option arch, +v
+L(strchr_loop):
+    vsetvli ivl, zero, e8, ELEM_LMUL_SETTING, ta, ma
+    vle8ff.v vstr, (str)
+    vmseq.vi vmask_end, vstr, 0
+    vmseq.vx vmask_ch, vstr, ch
+    vfirst.m end_offset, vmask_end /* first occurrence of \0 */
+    vfirst.m ch_offset, vmask_ch /* first occurrence of ch */
+    sltz temp1, ch_offset
+    sltu temp2, end_offset, ch_offset
+    or temp1, temp1, temp2
+    beqz temp1, L(found_ch) /* Found ch, not preceded by \0? */
+    csrr cur_vl, vl
+    add str, str, cur_vl
+    bltz end_offset, L(strchr_loop) /* Didn't find \0? */
+    li str, 0
+    ret
+L(found_ch):
+    add str, str, ch_offset
+    ret
+.option pop
+END (STRCHR)
+weak_alias (STRCHR, index)
+libc_hidden_builtin_def (strchr)

diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
index c74b470bd634cec58e1c0ae7a987c1f1becfbd03..2714b9e2d85cf778c8f71878d5c5147422cb5291 100644 (file)
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
@@ -19,6 +19,9 @@ sysdep_routines += \
   strcat \
   strcat-generic \
   strcat-vector \
+  strchr \
+  strchr-generic \
+  strchr-vector \
   strcmp \
   strcmp-generic \
   strcmp-vector \

diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c b/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
index caea83b7d761e0d6f454a7dda84b550c1c1efc69..f00001097b768d76f958f178fed0e62b4868dc9c 100644 (file)
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
@@ -95,5 +95,10 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
                              __memchr_vector)
              IFUNC_IMPL_ADD (array, i, memchr, 1, __memchr_generic))
 
+  IFUNC_IMPL (i, name, strchr,
+             IFUNC_IMPL_ADD (array, i, strchr, rvv_enabled,
+                             __strchr_vector)
+             IFUNC_IMPL_ADD (array, i, strchr, 1, __strchr_generic))
+
   return 0;
 }

diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/strchr.c b/sysdeps/unix/sysv/linux/riscv/multiarch/strchr.c
new file mode 100644 (file)
index 0000000..ef75a2b
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/strchr.c
@@ -0,0 +1,58 @@
+/* Multiple versions of strchr.
+   All versions must be listed in ifunc-impl-list.c.
+   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/>.  */
+
+#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 <stdint.h>
+# include <string.h>
+# include <ifunc-init.h>
+# include <riscv-ifunc.h>
+# include <sys/hwprobe.h>
+
+extern __typeof (__redirect_strchr) __libc_strchr;
+
+extern __typeof (__redirect_strchr) __strchr_generic attribute_hidden;
+extern __typeof (__redirect_strchr) __strchr_vector attribute_hidden;
+
+static inline __typeof (__redirect_strchr) *
+select_strchr_ifunc (uint64_t dl_hwcap, __riscv_hwprobe_t hwprobe_func)
+{
+  unsigned long long int v;
+  if (__riscv_hwprobe_one (hwprobe_func, RISCV_HWPROBE_KEY_IMA_EXT_0, &v) == 0
+      && (v & RISCV_HWPROBE_IMA_V) == RISCV_HWPROBE_IMA_V)
+    return __strchr_vector;
+  return __strchr_generic;
+}
+
+riscv_libc_ifunc (__libc_strchr, select_strchr_ifunc);
+
+# undef strchr
+# undef index
+strong_alias (__libc_strchr, strchr);
+weak_alias (strchr, index);
+# ifdef SHARED
+__hidden_ver1 (strchr, __GI_strchr, __redirect_strchr)
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (strchr);
+# endif
+#else
+# include <string/strchr.c>
+#endif