[PATCH v2] RISC-V: add multiarch RVV support for memcpy using FMV IFUNC

[daichengrong@iscas.ac.cn]

> On Thu, Jan 16, 2025 at 1:31 AM 戴成荣 <daichengrong@iscas.ac.cn> wrote:
> >
> > With RISC-V GCC Function multi-versioning IFUNC support,glibc could utilize some new RISC-V CPUs with new extensions such as Vector to re-realize or speed up some functions like memcpy.
> > +
> > +ENTRY (__memcpy_vector)
> > +    beq     a2, zero, L(ret)
> 
> This branch should be deleted; the strip-mine loop below does the
> correct thing for a2=0.  Including the branch is an anti-optimization:
> it speeds up the uncommon case of size-0 memcpy at the expense of the
> common case.
> 
thanks! This branch has been deleted.
> >
> > +    mv     a6, a0
> > +L(loop):
> > +    vsetvli a3,a2,e8,m8,ta,mu
> > +    vle8.v  v8,(a1)
> > +    vse8.v  v8,(a6)
> > +    add     a1,a1,a3
> > +    sub     a2,a2,a3
> > +    add     a6,a6,a3
> > +    bnez    a2,L(loop)
> > +L(ret):
> > +    ret
> > +END (__memcpy_vector)

Signed-off-by: daichengrong <daichengrong@iscas.ac.cn>
---
 sysdeps/riscv/multiarch/memcpy_vector.S       | 35 +++++++++++++++++++
 .../unix/sysv/linux/riscv/multiarch/Makefile  |  2 ++
 .../unix/sysv/linux/riscv/multiarch/memcpy.c  |  5 +++
 3 files changed, 42 insertions(+)
 create mode 100644 sysdeps/riscv/multiarch/memcpy_vector.S

diff --git a/sysdeps/riscv/multiarch/memcpy_vector.S b/sysdeps/riscv/multiarch/memcpy_vector.S
new file mode 100644
index 0000000000..8fddab8432
--- /dev/null
+++ b/sysdeps/riscv/multiarch/memcpy_vector.S
@@ -0,0 +1,35 @@
+/* memcpy for RISC-V Vector.
+   Copyright (C) 2024-2025 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=""></https:>.  */
+
+
+#include <sysdep.h>
+#include <sys asm.h="">
+
+ENTRY (__memcpy_vector)
+    mv	    a6, a0
+L(loop):
+    vsetvli a3,a2,e8,m8,ta,mu
+    vle8.v  v8,(a1)
+    vse8.v  v8,(a6)
+    add     a1,a1,a3
+    sub     a2,a2,a3
+    add     a6,a6,a3
+    bnez    a2,L(loop)
+L(ret):
+    ret
+END (__memcpy_vector)
diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
index fcef5659d4..a8b6c22af1 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/Makefile
@@ -3,7 +3,9 @@ sysdep_routines += \
   memcpy \
   memcpy-generic \
   memcpy_noalignment \
+  memcpy_vector \
   # sysdep_routines
 
 CFLAGS-memcpy_noalignment.c += -mno-strict-align
+ASFLAGS-memcpy_vector.S += -march=rv64gcv
 endif
diff --git a/sysdeps/unix/sysv/linux/riscv/multiarch/memcpy.c b/sysdeps/unix/sysv/linux/riscv/multiarch/memcpy.c
index 8544f5402a..c9879762f6 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/memcpy.c
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/memcpy.c
@@ -32,11 +32,16 @@ extern __typeof (__redirect_memcpy) __libc_memcpy;
 
 extern __typeof (__redirect_memcpy) __memcpy_generic attribute_hidden;
 extern __typeof (__redirect_memcpy) __memcpy_noalignment attribute_hidden;
+extern __typeof (__redirect_memcpy)  __memcpy_vector attribute_hidden;
 
 static inline __typeof (__redirect_memcpy) *
 select_memcpy_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 __memcpy_vector;
+
   if (__riscv_hwprobe_one (hwprobe_func, RISCV_HWPROBE_KEY_CPUPERF_0, &v) == 0
       && (v & RISCV_HWPROBE_MISALIGNED_MASK) == RISCV_HWPROBE_MISALIGNED_FAST)
     return __memcpy_noalignment;
-- 
2.25.1</sys></sysdep.h></daichengrong@iscas.ac.cn></daichengrong@iscas.ac.cn>