[PATCH v5 02/18] riscv: Add RVV memchr for multiarch and non-multiarch
Yao Zihong
zihong.plct@isrc.iscas.ac.cn
Tue Feb 3 15:05:26 GMT 2026
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>
---
sysdeps/riscv/multiarch/memchr-generic.c | 24 +++++++
sysdeps/riscv/multiarch/memchr-vector.S | 26 +++++++
sysdeps/riscv/rvv/memchr.S | 67 +++++++++++++++++++
.../unix/sysv/linux/riscv/multiarch/Makefile | 3 +
.../linux/riscv/multiarch/ifunc-impl-list.c | 5 ++
.../unix/sysv/linux/riscv/multiarch/memchr.c | 57 ++++++++++++++++
6 files changed, 182 insertions(+)
create mode 100644 sysdeps/riscv/multiarch/memchr-generic.c
create mode 100644 sysdeps/riscv/multiarch/memchr-vector.S
create mode 100644 sysdeps/riscv/rvv/memchr.S
create mode 100644 sysdeps/unix/sysv/linux/riscv/multiarch/memchr.c
diff --git a/sysdeps/riscv/multiarch/memchr-generic.c b/sysdeps/riscv/multiarch/memchr-generic.c
new file mode 100644
index 0000000000..a95e16ee51
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memchr-generic.c
@@ -0,0 +1,24 @@
+/* Re-include the default memchr 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 MEMCHR __memchr_generic
+# include <string/memchr.c>
+#endif
diff --git a/sysdeps/riscv/multiarch/memchr-vector.S b/sysdeps/riscv/multiarch/memchr-vector.S
new file mode 100644
index 0000000000..951f256245
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memchr-vector.S
@@ -0,0 +1,26 @@
+/* Re-include the RISC-V RVV based memchr 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 MEMCHR __memchr_vector
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(name)
+# undef weak_alias
+# define weak_alias(name, alias)
+# include <sysdeps/riscv/rvv/memchr.S>
+#endif
diff --git a/sysdeps/riscv/rvv/memchr.S b/sysdeps/riscv/rvv/memchr.S
new file mode 100644
index 0000000000..609b2f94c1
--- /dev/null
+++ b/sysdeps/riscv/rvv/memchr.S
@@ -0,0 +1,67 @@
+/* RISC-V RVV based memchr.
+ 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 MEMCHR
+# define MEMCHR __memchr
+#endif
+
+#define result a0
+
+#define src a0
+#define value a1
+#define num a2
+
+#define ivl a3
+#define temp a4
+
+#define ELEM_LMUL_SETTING m8
+#define vdata v0
+#define vmask v8
+
+ENTRY (MEMCHR)
+.option push
+.option arch, +v
+L(loop):
+ vsetvli zero, num, e8, ELEM_LMUL_SETTING, ta, ma
+
+ vle8ff.v vdata, (src)
+ /* Find the value inside the loaded data. */
+ vmseq.vx vmask, vdata, value
+ vfirst.m temp, vmask
+
+ /* Skip the loop if we find the matched value. */
+ bgez temp, L(found)
+
+ csrr ivl, vl
+ sub num, num, ivl
+ add src, src, ivl
+
+ bnez num, L(loop)
+
+ li result, 0
+ ret
+L(found):
+ add result, src, temp
+ ret
+.option pop
+END (MEMCHR)
+weak_alias (MEMCHR, memchr)
+libc_hidden_builtin_def (memchr)
diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
index 0c1c2b4467..4ad91c0744 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
@@ -3,6 +3,9 @@ sysdep_routines += \
memccpy \
memccpy-generic \
memccpy-vector \
+ memchr \
+ memchr-generic \
+ memchr-vector \
memcpy \
memcpy-generic \
memcpy_noalignment \
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 cd9460f57e..65a4b664b2 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
@@ -58,5 +58,10 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
__memccpy_vector)
IFUNC_IMPL_ADD (array, i, memccpy, 1, __memccpy_generic))
+ IFUNC_IMPL (i, name, memchr,
+ IFUNC_IMPL_ADD (array, i, memchr, rvv_enabled,
+ __memchr_vector)
+ IFUNC_IMPL_ADD (array, i, memchr, 1, __memchr_generic))
+
return 0;
}
diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/memchr.c b/sysdeps/unix/sysv/linux/riscv/multiarch/memchr.c
new file mode 100644
index 0000000000..0844a33760
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/memchr.c
@@ -0,0 +1,57 @@
+/* Multiple versions of memchr.
+ 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 memchr so that the compiler won't complain about the type
+ mismatch with the IFUNC selector in strong_alias, below. */
+# undef memchr
+# define memchr __redirect_memchr
+# include <stdint.h>
+# include <string.h>
+# include <ifunc-init.h>
+# include <riscv-ifunc.h>
+# include <sys/hwprobe.h>
+
+extern __typeof (__redirect_memchr) __libc_memchr;
+
+extern __typeof (__redirect_memchr) __memchr_generic attribute_hidden;
+extern __typeof (__redirect_memchr) __memchr_vector attribute_hidden;
+
+static inline __typeof (__redirect_memchr) *
+select_memchr_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 __memchr_vector;
+ return __memchr_generic;
+}
+
+riscv_libc_ifunc (__libc_memchr, select_memchr_ifunc);
+
+# undef memchr
+strong_alias (__libc_memchr, memchr);
+strong_alias (memchr, __memchr)
+# ifdef SHARED
+__hidden_ver1 (memchr, __GI_memchr, __redirect_memchr)
+ __attribute__ ((visibility ("hidden"))) __attribute_copy__ (memchr);
+# endif
+#else
+# include <string/memchr.c>
+#endif
--
2.47.3
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