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

This patch adds an RVV-optimized implementation of memset 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 (__memset_vector) is added
alongside the generic fallback (__memset_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 memset().

Co-authored-by: Jerry Shih <jerry.shih@sifive.com>
Co-authored-by: Jeff Law <jeffreyalaw@gmail.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/dl-symbol-redir-ifunc.h b/sysdeps/riscv/multiarch/dl-symbol-redir-ifunc.h
new file mode 100644 (file)
index 0000000..2ff7369
--- /dev/null
+++ b/sysdeps/riscv/multiarch/dl-symbol-redir-ifunc.h
@@ -0,0 +1,26 @@
+/* Symbol redirection for loader/static initialization code.
+   Copyright (C) 2025 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/>.  */
+
+#ifndef _DL_IFUNC_GENERIC_H
+#define _DL_IFUNC_GENERIC_H
+
+#ifndef SHARED
+asm ("memset = __memset_generic");
+#endif
+
+#endif

diff --git a/sysdeps/riscv/multiarch/memset-generic.c b/sysdeps/riscv/multiarch/memset-generic.c
new file mode 100644 (file)
index 0000000..c93bb43
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memset-generic.c
@@ -0,0 +1,26 @@
+/* Re-include the default memset implementation.
+   Copyright (C) 2025 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 MEMSET __memset_generic
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(x)
+#endif
+#include <string/memset.c>

diff --git a/sysdeps/riscv/multiarch/memset-vector.S b/sysdeps/riscv/multiarch/memset-vector.S
new file mode 100644 (file)
index 0000000..83d8c20
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memset-vector.S
@@ -0,0 +1,25 @@
+
+/* RISC-V RVV based memset.
+   Copyright (C) 2025 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
+   <http://www.gnu.org/licenses/>.  */
+
+#if IS_IN(libc)
+# define MEMSET __memset_vector
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(name)
+#include <sysdeps/riscv/rvv/memset.S>
+#endif

diff --git a/sysdeps/riscv/preconfigure b/sysdeps/riscv/preconfigure
index a96cd0d7f87c7fbfa1138ca6387ebe49ee2520ac..92ffa1ac026f2ac0a7a13eeb1d1c151118e0fe4e 100644 (file)
--- a/sysdeps/riscv/preconfigure
+++ b/sysdeps/riscv/preconfigure
@@ -60,6 +60,7 @@ riscv*)
        version=`$CC $CFLAGS $CPPFLAGS -E -dM -xc /dev/null | sed -n 's/^#define __GNUC__ \(.*\)/\1/p'`
        test $version -lt 15 && as_fn_error 1 "glibc requires GCC 15 or later for the V extension" "$LINENO" 5
        test $vector -lt "1000000" && as_fn_error 1 "glibc requires at least RVV 1.0 for the V extension" "$LINENO" 5
+       float_machine=rvv
     fi
 
     base_machine=riscv

diff --git a/sysdeps/riscv/preconfigure.ac b/sysdeps/riscv/preconfigure.ac
index f95ffe83fb76d113fe4fbc8a2d3936894d809069..99fbb0c9c94163871c33f49779ab27c0df42e357 100644 (file)
--- a/sysdeps/riscv/preconfigure.ac
+++ b/sysdeps/riscv/preconfigure.ac
@@ -60,6 +60,7 @@ riscv*)
        version=`$CC $CFLAGS $CPPFLAGS -E -dM -xc /dev/null | sed -n 's/^#define __GNUC__ \(.*\)/\1/p'`
        test $version -lt 15 && AC_MSG_ERROR([glibc requires GCC 15 or later for the V extension], [1])
        test $vector -lt "1000000" && AC_MSG_ERROR([glibc requires at least RVV 1.0 for the V extension], [1])
+       float_machine=rvv
     fi
 
     base_machine=riscv

diff --git a/sysdeps/riscv/rv32/rvv/Implies b/sysdeps/riscv/rv32/rvv/Implies
new file mode 100644 (file)
index 0000000..25ce1df
--- /dev/null
+++ b/sysdeps/riscv/rv32/rvv/Implies
@@ -0,0 +1,2 @@
+riscv/rv32/rvd
+riscv/rvv

diff --git a/sysdeps/riscv/rv64/rvv/Implies b/sysdeps/riscv/rv64/rvv/Implies
new file mode 100644 (file)
index 0000000..9993bb3
--- /dev/null
+++ b/sysdeps/riscv/rv64/rvv/Implies
@@ -0,0 +1,2 @@
+riscv/rv64/rvd
+riscv/rvv

diff --git a/sysdeps/riscv/rvv/memset.S b/sysdeps/riscv/rvv/memset.S
new file mode 100644 (file)
index 0000000..2b81a93
--- /dev/null
+++ b/sysdeps/riscv/rvv/memset.S
@@ -0,0 +1,53 @@
+/* RISC-V RVV based memset.
+   Copyright (C) 2025 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include <sys/asm.h>
+
+#ifndef MEMSET
+# define MEMSET memset
+#endif
+
+#define dst a0
+#define value a1
+#define num a2
+
+#define ivl a3
+#define dst_ptr a5
+
+#define ELEM_LMUL_SETTING m8
+#define vdata v0
+
+ENTRY (MEMSET)
+.option push
+.option arch, +v
+    mv dst_ptr, dst
+
+    vsetvli ivl, num, e8, ELEM_LMUL_SETTING, ta, ma
+    vmv.v.x vdata, value
+L(loop):
+    vse8.v vdata, (dst_ptr)
+    sub num, num, ivl
+    add dst_ptr, dst_ptr, ivl
+    vsetvli ivl, num, e8, ELEM_LMUL_SETTING, ta, ma
+    bnez num, L(loop)
+
+    ret
+.option pop
+END (MEMSET)
+libc_hidden_builtin_def (memset)

diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
index fcef5659d442526ab4edf4c9815d6d569ad2dc10..1d26966dedf6749a18d0f01ae730d7d6f3af7314 100644 (file)
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
@@ -3,6 +3,9 @@ sysdep_routines += \
   memcpy \
   memcpy-generic \
   memcpy_noalignment \
+  memset \
+  memset-generic \
+  memset-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 1c1deca8f664cab9726895d723b3a3f11e3b3f14..87456f3370841d240fe034d6da39451e3a66b368 100644 (file)
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
@@ -27,17 +27,31 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   size_t i = max;
 
   bool fast_unaligned = false;
+  bool rvv_enabled = false;
 
-  struct riscv_hwprobe pair = { .key = RISCV_HWPROBE_KEY_CPUPERF_0 };
-  if (__riscv_hwprobe (&pair, 1, 0, NULL, 0) == 0
-      && (pair.value & RISCV_HWPROBE_MISALIGNED_MASK)
+  struct riscv_hwprobe pairs[2] = {
+    {.key = RISCV_HWPROBE_KEY_CPUPERF_0},
+    {.key = RISCV_HWPROBE_KEY_IMA_EXT_0}
+  };
+
+  if (__riscv_hwprobe (pairs, 2, 0, NULL, 0) == 0) {
+    if ((pairs[0].value & RISCV_HWPROBE_MISALIGNED_MASK)
           == RISCV_HWPROBE_MISALIGNED_FAST)
-    fast_unaligned = true;
+      fast_unaligned = true;
+
+    if (pairs[1].value & RISCV_HWPROBE_IMA_V)
+      rvv_enabled = true;
+  }
 
   IFUNC_IMPL (i, name, memcpy,
              IFUNC_IMPL_ADD (array, i, memcpy, fast_unaligned,
                              __memcpy_noalignment)
              IFUNC_IMPL_ADD (array, i, memcpy, 1, __memcpy_generic))
 
+  IFUNC_IMPL (i, name, memset,
+             IFUNC_IMPL_ADD (array, i, memset, rvv_enabled,
+                             __memset_vector)
+             IFUNC_IMPL_ADD (array, i, memset, 1, __memset_generic))
+
   return 0;
 }

diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/memset.c b/sysdeps/unix/sysv/linux/riscv/multiarch/memset.c
new file mode 100644 (file)
index 0000000..166427b
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/memset.c
@@ -0,0 +1,58 @@
+/* Multiple versions of memset.
+   All versions must be listed in ifunc-impl-list.c.
+   Copyright (C) 2025 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 memset so that the compiler won't complain about the type
+   mismatch with the IFUNC selector in strong_alias, below.  */
+# undef memset
+# define memset __redirect_memset
+# include <stdint.h>
+# include <string.h>
+# include <ifunc-init.h>
+# include <riscv-ifunc.h>
+# include <sys/hwprobe.h>
+
+extern __typeof (__redirect_memset) __libc_memset;
+
+extern __typeof (__redirect_memset) __memset_generic attribute_hidden;
+extern __typeof (__redirect_memset) __memset_vector attribute_hidden;
+
+static inline __typeof (__redirect_memset) *
+select_memset_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 __memset_vector;
+
+  return __memset_generic;
+}
+
+riscv_libc_ifunc (__libc_memset, select_memset_ifunc);
+
+# undef memset
+strong_alias (__libc_memset, memset);
+# ifdef SHARED
+__hidden_ver1 (memset, __GI_memset, __redirect_memset)
+  __attribute__ ((visibility ("hidden"))) __attribute_copy__ (memset);
+# endif
+#else
+# include <string/memset.c>
+#endif