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

This patch adds an RVV-optimized implementation of memccpy 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 (__memccpy_vector) is added
alongside the generic fallback (__memccpy_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 memccpy().

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/memccpy-generic.c b/sysdeps/riscv/multiarch/memccpy-generic.c
new file mode 100644 (file)
index 0000000..d7e6e2d
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memccpy-generic.c
@@ -0,0 +1,26 @@
+/* Re-include the default memccpy 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 MEMCCPY __memccpy_generic
+# undef weak_alias
+# define weak_alias(x, x2)
+# include <string/memccpy.c>
+#endif

diff --git a/sysdeps/riscv/multiarch/memccpy-vector.S b/sysdeps/riscv/multiarch/memccpy-vector.S
new file mode 100644 (file)
index 0000000..8ea121e
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memccpy-vector.S
@@ -0,0 +1,24 @@
+/* Re-include the RISC-V RVV based memccpy 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 MEMCCPY __memccpy_vector
+# undef weak_alias
+# define weak_alias(name, alias)
+# include <sysdeps/riscv/rvv/memccpy.S>
+#endif

diff --git a/sysdeps/riscv/rvv/memccpy.S b/sysdeps/riscv/rvv/memccpy.S
new file mode 100644 (file)
index 0000000..5854d46
--- /dev/null
+++ b/sysdeps/riscv/rvv/memccpy.S
@@ -0,0 +1,67 @@
+/* RISC-V RVV based memccpy.
+   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 MEMCCPY
+# define MEMCCPY __memccpy
+#endif
+
+#define dst a0
+#define src a1
+#define c_val a2
+#define num a3
+
+#define ivl a4
+#define dst_ptr a5
+#define vfirst_idx a6
+
+#define ELEM_LMUL_SETTING m8
+#define vdata v0
+#define vmask v8
+
+ENTRY (MEMCCPY)
+.option push
+.option arch, +v
+    mv dst_ptr, dst
+L(loop):
+    vsetvli zero, num, e8, ELEM_LMUL_SETTING, ta, ma
+    vle8ff.v vdata, (src)
+
+    vmseq.vx vmask, vdata, c_val
+    vfirst.m vfirst_idx, vmask
+    csrr ivl, vl
+    bgez vfirst_idx, L(found)
+    vse8.v vdata, (dst_ptr)
+
+    sub num, num, ivl
+    add src, src, ivl
+    add dst_ptr, dst_ptr, ivl
+    bnez num, L(loop)
+    mv a0, zero
+    ret
+L(found):
+    addi vfirst_idx, vfirst_idx, 1
+    vsetvli zero, vfirst_idx, e8, ELEM_LMUL_SETTING, ta, ma
+    vse8.v vdata, (dst_ptr)
+    add a0, dst_ptr, vfirst_idx
+    ret
+.option pop
+END (MEMCCPY)
+weak_alias (MEMCCPY, memccpy)

diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
index 20ff2bdca2371d9baf6cd2b5a9179f6017b2c50c..52730cf01c3d6c02462875ae0c1dee917cb8c448 100644 (file)
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
@@ -1,5 +1,8 @@
 ifeq ($(subdir),string)
 sysdep_routines += \
+  memccpy \
+  memccpy-generic \
+  memccpy-vector \
   memcmp \
   memcmp-generic \
   memcmp-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 1d09cf27a3a12bcdb54810dc4ea7c121d17ceac4..a373de6c89eaf16f917f68a4bb66a93135338a2d 100644 (file)
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
@@ -80,6 +80,11 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
                              __strncmp_vector)
              IFUNC_IMPL_ADD (array, i, strncmp, 1, __strncmp_generic))
 
+  IFUNC_IMPL (i, name, memccpy,
+             IFUNC_IMPL_ADD (array, i, memccpy, rvv_enabled,
+                             __memccpy_vector)
+             IFUNC_IMPL_ADD (array, i, memccpy, 1, __memccpy_generic))
+
   IFUNC_IMPL (i, name, memcmp,
              IFUNC_IMPL_ADD (array, i, memcmp, rvv_enabled,
                              __memcmp_vector)

diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/memccpy.c b/sysdeps/unix/sysv/linux/riscv/multiarch/memccpy.c
new file mode 100644 (file)
index 0000000..84d300b
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/memccpy.c
@@ -0,0 +1,58 @@
+/* Multiple versions of memccpy.
+   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 memccpy so that the compiler won't complain about the type
+   mismatch with the IFUNC selector in strong_alias, below.  */
+# undef memccpy
+# define memccpy __redirect_memccpy
+# include <stdint.h>
+# include <string.h>
+# include <ifunc-init.h>
+# include <riscv-ifunc.h>
+# include <sys/hwprobe.h>
+
+extern __typeof (__redirect_memccpy) __libc_memccpy;
+
+extern __typeof (__redirect_memccpy) __memccpy_generic attribute_hidden;
+extern __typeof (__redirect_memccpy) __memccpy_vector attribute_hidden;
+
+static inline __typeof (__redirect_memccpy) *
+select_memccpy_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 __memccpy_vector;
+
+  return __memccpy_generic;
+}
+
+riscv_libc_ifunc (__libc_memccpy, select_memccpy_ifunc);
+
+# undef memccpy
+weak_alias (__libc_memccpy, memccpy);
+# ifdef SHARED
+__hidden_ver1 (memccpy, __GI_memccpy, __redirect_memccpy)
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (memccpy);
+# endif
+#else
+# include <string/memccpy.c>
+#endif