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.

diff --git a/sysdeps/x86_64/multiarch/Makefile b/sysdeps/x86_64/multiarch/Makefile
index 666ee4d5d6326d4cd5246c99ff165b3f2448c5ac..0525cef3fea9d60e6d0c8934f74a3d0770bce01b 100644 (file)
--- a/sysdeps/x86_64/multiarch/Makefile
+++ b/sysdeps/x86_64/multiarch/Makefile
@@ -29,6 +29,7 @@ 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 (file)
index 0000000..e83cccc
--- /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 abc12d9cda1b3843bc1aa515949253ee8630bb62..905d0fa4643d57684460bb0c0d8138aa89f02ff7 100644 (file)
--- 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