riscv: add RVV-optimized memcmp

Message ID 20260508080623.21107-1-daichengrong@iscas.ac.cn (mailing list archive)
State New
Headers
Series riscv: add RVV-optimized memcmp |

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Context Check Description
redhat-pt-bot/TryBot-apply_patch success Patch applied to master at the time it was sent
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redhat-pt-bot/TryBot-still_applies warning Patch no longer applies to master

Commit Message

daichengrong May 8, 2026, 8:06 a.m. UTC
  This patch introduces an RVV based implementation of memcmp, 
leveraging vector instructions to improve data-level parallelism.

Signed-off-by: daichengrong <daichengrong@iscas.ac.cn>
---
 sysdeps/riscv/multiarch/memcmp-generic.c      |  30 ++++
 sysdeps/riscv/multiarch/memcmp-vector.S       |  30 ++++
 sysdeps/riscv/rvv/memcmp.S                    | 132 ++++++++++++++++++
 .../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, 260 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
  

Patch

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..c7ee412d67
--- /dev/null
+++ b/sysdeps/riscv/rvv/memcmp.S
@@ -0,0 +1,132 @@ 
+/* 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 cnt     a2
+
+#define cnt_rem		a2
+#define cnt_rem_2   a5
+#define new_vl      t6
+
+#define temp    t0
+
+#define src1_2  a6
+#define src2_2  t3
+
+#define vdata1  v0
+#define vdata2  v16
+
+#define vdata1_2 v8
+#define vdata2_2 v24
+
+#define vmask1 v0
+#define vmask2 v8
+
+#define vfirst_index    a4
+#define vfirst_index_2  t1
+
+#define chr1    a0
+#define chr2    a1
+
+ENTRY (MEMCMP)
+.option push
+.option arch, +v
+    beqz        cnt, L(ret)
+    and         temp, cnt, 0x7F
+    beqz        temp, L(loop_pre)
+    vsetvli     new_vl, temp, e8, m8, ta, ma
+    vle8.v      vdata1, (src1)
+    vle8.v      vdata2, (src2)
+
+    vmsne.vv    vmask1, vdata1, v16
+    vfirst.m    vfirst_index, vmask1
+    bgez        vfirst_index, L(found)
+
+    beq         new_vl, cnt, L(ret)
+
+    add         src1, src1, new_vl
+    add         src2, src2, new_vl
+    sub         cnt_rem, cnt, new_vl
+
+L(loop_pre):
+    srli        cnt_rem_2, cnt_rem, 1
+L(loop):
+    vsetvli     new_vl, cnt_rem_2, e8, m8, ta, ma
+
+    vle8.v      vdata1, (src1)
+    add         src1_2, src1, new_vl
+    vle8.v      vdata2, (src2)
+    add         src2_2, src2, new_vl
+
+    vle8.v      vdata1_2, (src1_2)
+    vle8.v      vdata2_2, (src2_2)
+
+    vmsne.vv    vmask1, vdata1, vdata2
+    vmsne.vv    vmask2, vdata1_2, vdata2_2
+
+    vfirst.m    vfirst_index, vmask1
+    vfirst.m    vfirst_index_2, vmask2
+
+    bgez        vfirst_index, L(found1)
+    bgez        vfirst_index_2, L(found2)
+
+    add         src1, src1_2, new_vl
+    add         src2, src2_2, new_vl
+
+    sub         cnt_rem_2, cnt_rem_2, new_vl
+    bnez        cnt_rem_2, L(loop)
+L(ret):
+    li          result, 0
+    ret
+L(found):
+L(found1):
+    add         src1, src1, vfirst_index
+    add         src2, src2, vfirst_index
+    lbu         chr1, (src1)
+    lbu         chr2, (src2)
+    sub         result, chr1, chr2
+    ret
+L(found2):
+    add         src1_2, src1_2, vfirst_index_2
+    add         src2_2, src2_2, vfirst_index_2
+    lbu         chr1, (src1_2)
+    lbu         chr2, (src2_2)
+    sub         result, chr1, chr2
+    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 2a2b90960f..86b045ad45 100644
--- 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 += \
+  memcmp \
+  memcmp-generic \
+  memcmp-vector \
   memcpy \
   memcpy-generic \
   memcpy-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 2501546665..eb5d376fe9 100644
--- a/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
+++ b/sysdeps/unix/sysv/linux/riscv/multiarch/ifunc-impl-list.c
@@ -43,6 +43,11 @@  __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
       rvv_enabled = true;
   }
 
+  IFUNC_IMPL (i, name, memcmp,
+	      IFUNC_IMPL_ADD (array, i, memcmp, rvv_enabled,
+			      __memcmp_vector)
+	      IFUNC_IMPL_ADD (array, i, memcmp, 1, __memcmp_generic))
+
   IFUNC_IMPL (i, name, memcpy,
 	      IFUNC_IMPL_ADD (array, i, memcpy, rvv_enabled,
 			      __memcpy_vector)
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