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From: Sunil Pandey <skpgkp2@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/release/2.35/master] x86: Move and slightly improve memset_erms Date: Mon, 18 Jul 2022 20:59:03 +0000 (GMT) [thread overview] Message-ID: <20220718205903.5378F385274F@sourceware.org> (raw) 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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