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* [glibc/release/2.35/master] x86: Move and slightly improve memset_erms
@ 2022-07-18 20:59 Sunil Pandey
0 siblings, 0 replies; only message in thread
From: Sunil Pandey @ 2022-07-18 20:59 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=de6f7bb8737bc1b00541181364d6ccc98a3e1144
commit de6f7bb8737bc1b00541181364d6ccc98a3e1144
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Wed Jun 29 16:07:05 2022 -0700
x86: Move and slightly improve memset_erms
Implementation wise:
1. Remove the VZEROUPPER as memset_{impl}_unaligned_erms does not
use the L(stosb) label that was previously defined.
2. Don't give the hotpath (fallthrough) to zero size.
Code positioning wise:
Move memset_{chk}_erms to its own file. Leaving it in between the
memset_{impl}_unaligned both adds unnecessary complexity to the
file and wastes space in a relatively hot cache section.
(cherry picked from commit 4a3f29e7e475dd4e7cce2a24c187e6fb7b5b0a05)
Diff:
---
sysdeps/x86_64/multiarch/Makefile | 1 +
sysdeps/x86_64/multiarch/memset-erms.S | 44 ++++++++++++++++++++++
.../x86_64/multiarch/memset-vec-unaligned-erms.S | 31 ---------------
3 files changed, 45 insertions(+), 31 deletions(-)
diff --git a/sysdeps/x86_64/multiarch/Makefile b/sysdeps/x86_64/multiarch/Makefile
index 4aefe48129..23bd697eef 100644
--- a/sysdeps/x86_64/multiarch/Makefile
+++ b/sysdeps/x86_64/multiarch/Makefile
@@ -33,6 +33,7 @@ sysdep_routines += \
memset-avx2-unaligned-erms-rtm \
memset-avx512-no-vzeroupper \
memset-avx512-unaligned-erms \
+ memset-erms \
memset-evex-unaligned-erms \
memset-sse2-unaligned-erms \
rawmemchr-avx2 \
diff --git a/sysdeps/x86_64/multiarch/memset-erms.S b/sysdeps/x86_64/multiarch/memset-erms.S
new file mode 100644
index 0000000000..e83cccc731
--- /dev/null
+++ b/sysdeps/x86_64/multiarch/memset-erms.S
@@ -0,0 +1,44 @@
+/* memset implement with rep stosb
+ Copyright (C) 2022 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>
+
+#if defined USE_MULTIARCH && IS_IN (libc)
+ .text
+ENTRY (__memset_chk_erms)
+ cmp %RDX_LP, %RCX_LP
+ jb HIDDEN_JUMPTARGET (__chk_fail)
+END (__memset_chk_erms)
+
+/* Only used to measure performance of REP STOSB. */
+ENTRY (__memset_erms)
+ /* Skip zero length. */
+ test %RDX_LP, %RDX_LP
+ jz L(stosb_return_zero)
+ mov %RDX_LP, %RCX_LP
+ movzbl %sil, %eax
+ mov %RDI_LP, %RDX_LP
+ rep stosb
+ mov %RDX_LP, %RAX_LP
+ ret
+L(stosb_return_zero):
+ movq %rdi, %rax
+ ret
+END (__memset_erms)
+#endif
diff --git a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
index abc12d9cda..905d0fa464 100644
--- a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
+++ b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
@@ -156,37 +156,6 @@ L(entry_from_wmemset):
#if defined USE_MULTIARCH && IS_IN (libc)
END (MEMSET_SYMBOL (__memset, unaligned))
-# if VEC_SIZE == 16
-ENTRY (__memset_chk_erms)
- cmp %RDX_LP, %RCX_LP
- jb HIDDEN_JUMPTARGET (__chk_fail)
-END (__memset_chk_erms)
-
-/* Only used to measure performance of REP STOSB. */
-ENTRY (__memset_erms)
- /* Skip zero length. */
- test %RDX_LP, %RDX_LP
- jnz L(stosb)
- movq %rdi, %rax
- ret
-# else
-/* Provide a hidden symbol to debugger. */
- .hidden MEMSET_SYMBOL (__memset, erms)
-ENTRY (MEMSET_SYMBOL (__memset, erms))
-# endif
-L(stosb):
- mov %RDX_LP, %RCX_LP
- movzbl %sil, %eax
- mov %RDI_LP, %RDX_LP
- rep stosb
- mov %RDX_LP, %RAX_LP
- VZEROUPPER_RETURN
-# if VEC_SIZE == 16
-END (__memset_erms)
-# else
-END (MEMSET_SYMBOL (__memset, erms))
-# endif
-
# if defined SHARED && IS_IN (libc)
ENTRY_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned_erms))
cmp %RDX_LP, %RCX_LP
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