[PATCH v5 03/18] riscv: Add RVV memcmp for multiarch and non-multiarch
Yao Zihong
zihong.plct@isrc.iscas.ac.cn
Tue Feb 3 15:05:27 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/memcmp-generic.c | 30 +++++++
sysdeps/riscv/multiarch/memcmp-vector.S | 30 +++++++
sysdeps/riscv/rvv/memcmp.S | 84 +++++++++++++++++++
.../unix/sysv/linux/riscv/multiarch/Makefile | 3 +
.../linux/riscv/multiarch/ifunc-impl-list.c | 5 ++
.../unix/sysv/linux/riscv/multiarch/memcmp.c | 60 +++++++++++++
6 files changed, 212 insertions(+)
create mode 100644 sysdeps/riscv/multiarch/memcmp-generic.c
create mode 100644 sysdeps/riscv/multiarch/memcmp-vector.S
create mode 100644 sysdeps/riscv/rvv/memcmp.S
create mode 100644 sysdeps/unix/sysv/linux/riscv/multiarch/memcmp.c
diff --git a/sysdeps/riscv/multiarch/memcmp-generic.c b/sysdeps/riscv/multiarch/memcmp-generic.c
new file mode 100644
index 0000000000..14f6752406
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memcmp-generic.c
@@ -0,0 +1,30 @@
+/* Re-include the default memcmp 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 MEMCMP __memcmp_generic
+# undef libc_hidden_def
+# define libc_hidden_def(x)
+# undef weak_alias
+# define weak_alias(x, x2)
+# undef strong_alias
+# define strong_alias(x, x2)
+# include <string/memcmp.c>
+#endif
diff --git a/sysdeps/riscv/multiarch/memcmp-vector.S b/sysdeps/riscv/multiarch/memcmp-vector.S
new file mode 100644
index 0000000000..b447e945a8
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memcmp-vector.S
@@ -0,0 +1,30 @@
+/* Re-include the RISC-V RVV based memcmp 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 MEMCMP __memcmp_vector
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(name)
+# undef libc_hidden_def
+# define libc_hidden_def(name)
+# undef weak_alias
+# define weak_alias(name, alias)
+# undef strong_alias
+# define strong_alias(name, alias)
+# include <sysdeps/riscv/rvv/memcmp.S>
+#endif
diff --git a/sysdeps/riscv/rvv/memcmp.S b/sysdeps/riscv/rvv/memcmp.S
new file mode 100644
index 0000000000..004bf538f0
--- /dev/null
+++ b/sysdeps/riscv/rvv/memcmp.S
@@ -0,0 +1,84 @@
+/* RISC-V RVV based memcmp.
+ 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 MEMCMP
+# define MEMCMP memcmp
+#endif
+
+#define result a0
+
+#define src1 a0
+#define src2 a1
+#define num a2
+
+#define ivl a3
+#define temp a4
+
+#define ELEM_LMUL_SETTING m8
+#define vdata1 v0
+#define vdata2 v8
+#define vmask v16
+#define vtemp1 v16
+#define vtemp2 v24
+
+ENTRY (MEMCMP)
+.option push
+.option arch, +v
+L(loop):
+ vsetvli ivl, num, e8, ELEM_LMUL_SETTING, ta, ma
+
+ vle8.v vdata1, (src1)
+ vle8.v vdata2, (src2)
+
+ vmsne.vv vmask, vdata1, vdata2
+ sub num, num, ivl
+ vfirst.m temp, vmask
+
+ bgez temp, L(found)
+
+ add src1, src1, ivl
+ add src2, src2, ivl
+
+ bnez num, L(loop)
+
+ li result, 0
+ ret
+L(found):
+ vrgather.vx vtemp1, vdata1, temp
+ vrgather.vx vtemp2, vdata2, temp
+ vmv.x.s result, vtemp1
+ vmv.x.s temp, vtemp2
+ andi result, result, 0xff
+ andi temp, temp, 0xff
+ sub result, result, temp
+ ret
+.option pop
+END (MEMCMP)
+libc_hidden_builtin_def(memcmp)
+#ifdef weak_alias
+#undef bcmp
+weak_alias (MEMCMP, bcmp)
+#endif
+
+#undef __memcmpeq
+strong_alias (MEMCMP, __memcmpeq)
+libc_hidden_builtin_def (MEMCMP)
+libc_hidden_def (__memcmpeq)
diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
index 4ad91c0744..0edc677874 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
@@ -6,6 +6,9 @@ sysdep_routines += \
memchr \
memchr-generic \
memchr-vector \
+ memcmp \
+ memcmp-generic \
+ memcmp-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 65a4b664b2..fe45e043e0 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
@@ -63,5 +63,10 @@ __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, memcmp,
+ IFUNC_IMPL_ADD (array, i, memcmp, rvv_enabled,
+ __memcmp_vector)
+ IFUNC_IMPL_ADD (array, i, memcmp, 1, __memcmp_generic))
+
return 0;
}
diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/memcmp.c b/sysdeps/unix/sysv/linux/riscv/multiarch/memcmp.c
new file mode 100644
index 0000000000..20e7b046ab
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/memcmp.c
@@ -0,0 +1,60 @@
+/* Multiple versions of memcmp.
+ 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 memcmp so that the compiler won't complain about the type
+ mismatch with the IFUNC selector in strong_alias, below. */
+# undef memcmp
+# define memcmp __redirect_memcmp
+# include <stdint.h>
+# include <string.h>
+# include <ifunc-init.h>
+# include <riscv-ifunc.h>
+# include <sys/hwprobe.h>
+
+extern __typeof (__redirect_memcmp) __libc_memcmp;
+
+extern __typeof (__redirect_memcmp) __memcmp_generic attribute_hidden;
+extern __typeof (__redirect_memcmp) __memcmp_vector attribute_hidden;
+
+static inline __typeof (__redirect_memcmp) *
+select_memcmp_ifunc (uint64_t dl_hwcap, __riscv_hwprobe_t hwprobe_func)
+{
+ unsigned long long 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 __memcmp_vector;
+
+ return __memcmp_generic;
+}
+
+riscv_libc_ifunc (__libc_memcmp, select_memcmp_ifunc);
+
+# undef memcmp
+# undef bcmp
+strong_alias (__libc_memcmp, memcmp);
+weak_alias (memcmp, bcmp);
+# ifdef SHARED
+__hidden_ver1 (memcmp, __GI_memcmp, __redirect_memcmp)
+ __attribute__ ((visibility ("hidden"))) __attribute_copy__ (memcmp);
+# endif
+#else
+# include <string/memcmp.c>
+#endif
--
2.47.3
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