[PATCH v4 14/18] riscv: Add RVV strncat for multiarch and non-multiarch
Yao Zihong
zihong.plct@isrc.iscas.ac.cn
Mon Jan 19 07:03:21 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/strncat-generic.c | 26 ++++++
sysdeps/riscv/multiarch/strncat-vector.S | 24 ++++++
sysdeps/riscv/rvv/strncat.S | 81 +++++++++++++++++++
.../unix/sysv/linux/riscv/multiarch/Makefile | 3 +
.../linux/riscv/multiarch/ifunc-impl-list.c | 5 ++
.../unix/sysv/linux/riscv/multiarch/strncat.c | 52 ++++++++++++
6 files changed, 191 insertions(+)
create mode 100644 sysdeps/riscv/multiarch/strncat-generic.c
create mode 100644 sysdeps/riscv/multiarch/strncat-vector.S
create mode 100644 sysdeps/riscv/rvv/strncat.S
create mode 100644 sysdeps/unix/sysv/linux/riscv/multiarch/strncat.c
diff --git a/sysdeps/riscv/multiarch/strncat-generic.c b/sysdeps/riscv/multiarch/strncat-generic.c
new file mode 100644
index 0000000000..66d7a17695
--- /dev/null
+++ b/sysdeps/riscv/multiarch/strncat-generic.c
@@ -0,0 +1,26 @@
+/* Re-include the default strncat 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 STRNCAT __strncat_generic
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(x)
+#endif
+#include <string/strncat.c>
diff --git a/sysdeps/riscv/multiarch/strncat-vector.S b/sysdeps/riscv/multiarch/strncat-vector.S
new file mode 100644
index 0000000000..c98820d7cd
--- /dev/null
+++ b/sysdeps/riscv/multiarch/strncat-vector.S
@@ -0,0 +1,24 @@
+/* Re-include the RISC-V RVV based strncat 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 STRNCAT __strncat_vector
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(name)
+# include <sysdeps/riscv/rvv/strncat.S>
+#endif
diff --git a/sysdeps/riscv/rvv/strncat.S b/sysdeps/riscv/rvv/strncat.S
new file mode 100644
index 0000000000..12fe9aa8d8
--- /dev/null
+++ b/sysdeps/riscv/rvv/strncat.S
@@ -0,0 +1,81 @@
+/* RISC-V RVV based strncat.
+ 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 STRNCAT
+# define STRNCAT strncat
+#endif
+
+#define dst a0
+#define src a1
+#define length a2
+#define dst_ptr a3
+#define cur_vl a4
+#define activate_elem_pos a5
+
+#define ELEM_LMUL_SETTING m1
+#define vmask1 v0
+#define vmask2 v1
+#define vstr1 v8
+#define vstr2 v16
+
+ENTRY (STRNCAT)
+.option push
+.option arch, +v
+ mv dst_ptr, dst
+ /* the strlen of dst. */
+L(strlen_loop):
+ vsetvli cur_vl, zero, e8, ELEM_LMUL_SETTING, ta, ma
+
+ vle8ff.v vstr1, (dst_ptr)
+ /* find the '\0'. */
+ vmseq.vx vmask1, vstr1, zero
+ csrr cur_vl, vl
+ vfirst.m activate_elem_pos, vmask1
+ add dst_ptr, dst_ptr, cur_vl
+ bltz activate_elem_pos, L(strlen_loop)
+
+ sub dst_ptr, dst_ptr, cur_vl
+ add dst_ptr, dst_ptr, activate_elem_pos
+
+ /* copy src to dst_ptr. */
+L(strcpy_loop):
+ vsetvli zero, length, e8, ELEM_LMUL_SETTING, ta, ma
+
+ vle8ff.v vstr1, (src)
+ vmseq.vx vmask2, vstr1, zero
+ csrr cur_vl, vl
+ vfirst.m activate_elem_pos, vmask2
+ vmsif.m vmask1, vmask2
+ add src, src, cur_vl
+ sub length, length, cur_vl
+ vse8.v vstr1, (dst_ptr), vmask1.t
+ add dst_ptr, dst_ptr, cur_vl
+ beqz length, L(fill_zero)
+ bltz activate_elem_pos, L(strcpy_loop)
+ ret
+L(fill_zero):
+ bgez activate_elem_pos, L(fill_zero_end)
+ sb zero, (dst_ptr)
+L(fill_zero_end):
+ ret
+.option pop
+END (STRNCAT)
+libc_hidden_builtin_def (strncat)
diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
index 47e16078c1..1b568bd3de 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
@@ -43,6 +43,9 @@ sysdep_routines += \
strlen \
strlen-generic \
strlen-vector \
+ strncat \
+ strncat-generic \
+ strncat-vector \
# sysdep_routines
CFLAGS-memcpy_noalignment.c += -mno-strict-align
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 fa5692a074..370d59d4c5 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
@@ -115,5 +115,10 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
__strlen_vector)
IFUNC_IMPL_ADD (array, i, strlen, 1, __strlen_generic))
+ IFUNC_IMPL (i, name, strncat,
+ IFUNC_IMPL_ADD (array, i, strncat, rvv_enabled,
+ __strncat_vector)
+ IFUNC_IMPL_ADD (array, i, strncat, 1, __strncat_generic))
+
return 0;
}
diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/strncat.c b/sysdeps/unix/sysv/linux/riscv/multiarch/strncat.c
new file mode 100644
index 0000000000..a7acfdfe54
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/strncat.c
@@ -0,0 +1,52 @@
+/* Multiple versions of strncat.
+ 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 strncat so that the compiler won't complain about the type
+ mismatch with the IFUNC selector in strong_alias, below. */
+# define strncat __redirect_strncat
+# include <stdint.h>
+# include <string.h>
+# undef strncat
+# include <ifunc-init.h>
+# include <riscv-ifunc.h>
+# include <sys/hwprobe.h>
+
+extern __typeof (__redirect_strncat) __strncat_generic attribute_hidden;
+extern __typeof (__redirect_strncat) __strncat_vector attribute_hidden;
+
+static inline __typeof (__redirect_strncat) *
+select_strncat_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 __strncat_vector;
+ return __strncat_generic;
+}
+
+riscv_libc_ifunc_redirected (__redirect_strncat, strncat, select_strncat_ifunc);
+strong_alias (strncat, __strncat);
+# ifdef SHARED
+__hidden_ver1 (strncat, __GI___strncat, __redirect_strncat)
+ __attribute__((visibility ("hidden"))) __attribute_copy__ (strncat);
+# endif
+#else
+# include <string/strncat.c>
+#endif
--
2.47.2
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