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x86_64: Remove bzero optimization

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Both symbols are marked as legacy in POSIX.1-2001 and removed on
POSIX.1-2008, although the prototypes are defined for _GNU_SOURCE
or _DEFAULT_SOURCE.

GCC also replaces bcopy with a memmove and bzero with memset on default
configuration (to actually get a bzero libc call the code requires
to omit string.h inclusion and built with -fno-builtin), so it is
highly unlikely programs are actually calling libc bzero symbol.

On a recent Linux distro (Ubuntu 22.04), there is no bzero calls
by the installed binaries.

  $ cat count_bstring.sh
  #!/bin/bash

  files=`IFS=':';for i in $PATH; do test -d "$i" && find "$i" -maxdepth 1 -executable -type f; done`
  total=0
  for file in $files; do
    symbols=`objdump -R $file 2>&1`
    if [ $? -eq 0 ]; then
      ncalls=`echo $symbols | grep -w $1 | wc -l`
      ((total=total+ncalls))
      if [ $ncalls -gt 0 ]; then
        echo "$file: $ncalls"
      fi
    fi
  done
  echo "TOTAL=$total"
  $ ./count_bstring.sh bzero
  TOTAL=0

Checked on x86_64-linux-gnu.

(cherry picked from commit 9403b71ae9)
This commit is contained in:
Adhemerval Zanella 2022-05-13 09:33:30 -03:00 committed by Sunil K Pandey
parent 8d324019e6
commit eb9aa96fac
11 changed files with 3 additions and 238 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
sysdeps/x86_64/bzero.S
View File

@ -1 +0,0 @@
/* Implemented in memset.S. */

10
sysdeps/x86_64/memset.S
View File

@ -1,4 +1,4 @@
/* memset/bzero -- set memory area to CH/0
/* memset -- set memory area to CH/0
Optimized version for x86-64.
Copyright (C) 2002-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
@ -35,9 +35,6 @@
punpcklwd %xmm0, %xmm0; \
pshufd $0, %xmm0, %xmm0
# define BZERO_ZERO_VEC0() \
pxor %xmm0, %xmm0
# define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
movd d, %xmm0; \
pshufd $0, %xmm0, %xmm0; \
@ -56,10 +53,6 @@
# define MEMSET_SYMBOL(p,s) memset
#endif
#ifndef BZERO_SYMBOL
# define BZERO_SYMBOL(p,s) __bzero
#endif
#ifndef WMEMSET_SYMBOL
# define WMEMSET_CHK_SYMBOL(p,s) p
# define WMEMSET_SYMBOL(p,s) __wmemset
@ -70,7 +63,6 @@
libc_hidden_builtin_def (memset)
#if IS_IN (libc)
weak_alias (__bzero, bzero)
libc_hidden_def (__wmemset)
weak_alias (__wmemset, wmemset)
libc_hidden_weak (wmemset)

1
sysdeps/x86_64/multiarch/Makefile
View File

@ -1,7 +1,6 @@
ifeq ($(subdir),string)
sysdep_routines += \
bzero \
memchr-avx2 \
memchr-avx2-rtm \
memchr-evex \

108
sysdeps/x86_64/multiarch/bzero.c
View File

@ -1,108 +0,0 @@
/* Multiple versions of bzero.
All versions must be listed in ifunc-impl-list.c.
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/>. */
/* Define multiple versions only for the definition in libc. */
#if IS_IN (libc)
# define __bzero __redirect___bzero
# include <string.h>
# undef __bzero
/* OPTIMIZE1 definition required for bzero patch. */
# define OPTIMIZE1(name) EVALUATOR1 (SYMBOL_NAME, name)
# define SYMBOL_NAME __bzero
# include <init-arch.h>
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (sse2_unaligned)
attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (sse2_unaligned_erms)
attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (avx2_unaligned) attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (avx2_unaligned_erms)
attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (avx2_unaligned_rtm)
attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (avx2_unaligned_erms_rtm)
attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (evex_unaligned)
attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (evex_unaligned_erms)
attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (avx512_unaligned)
attribute_hidden;
extern __typeof (REDIRECT_NAME) OPTIMIZE1 (avx512_unaligned_erms)
attribute_hidden;
static inline void *
IFUNC_SELECTOR (void)
{
const struct cpu_features* cpu_features = __get_cpu_features ();
if (CPU_FEATURE_USABLE_P (cpu_features, AVX512F)
&& !CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_AVX512))
{
if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
&& CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)
&& CPU_FEATURE_USABLE_P (cpu_features, BMI2))
{
if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
return OPTIMIZE1 (avx512_unaligned_erms);
return OPTIMIZE1 (avx512_unaligned);
}
}
if (CPU_FEATURE_USABLE_P (cpu_features, AVX2))
{
if (CPU_FEATURE_USABLE_P (cpu_features, AVX512VL)
&& CPU_FEATURE_USABLE_P (cpu_features, AVX512BW)
&& CPU_FEATURE_USABLE_P (cpu_features, BMI2))
{
if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
return OPTIMIZE1 (evex_unaligned_erms);
return OPTIMIZE1 (evex_unaligned);
}
if (CPU_FEATURE_USABLE_P (cpu_features, RTM))
{
if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
return OPTIMIZE1 (avx2_unaligned_erms_rtm);
return OPTIMIZE1 (avx2_unaligned_rtm);
}
if (!CPU_FEATURES_ARCH_P (cpu_features, Prefer_No_VZEROUPPER))
{
if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
return OPTIMIZE1 (avx2_unaligned_erms);
return OPTIMIZE1 (avx2_unaligned);
}
}
if (CPU_FEATURE_USABLE_P (cpu_features, ERMS))
return OPTIMIZE1 (sse2_unaligned_erms);
return OPTIMIZE1 (sse2_unaligned);
}
libc_ifunc_redirected (__redirect___bzero, __bzero, IFUNC_SELECTOR ());
weak_alias (__bzero, bzero)
#endif

42
sysdeps/x86_64/multiarch/ifunc-impl-list.c
View File

@ -280,48 +280,6 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
__memset_avx512_no_vzeroupper)
)
/* Support sysdeps/x86_64/multiarch/bzero.c. */
IFUNC_IMPL (i, name, bzero,
IFUNC_IMPL_ADD (array, i, bzero, 1,
__bzero_sse2_unaligned)
IFUNC_IMPL_ADD (array, i, bzero, 1,
__bzero_sse2_unaligned_erms)
IFUNC_IMPL_ADD (array, i, bzero,
CPU_FEATURE_USABLE (AVX2),
__bzero_avx2_unaligned)
IFUNC_IMPL_ADD (array, i, bzero,
CPU_FEATURE_USABLE (AVX2),
__bzero_avx2_unaligned_erms)
IFUNC_IMPL_ADD (array, i, bzero,
(CPU_FEATURE_USABLE (AVX2)
&& CPU_FEATURE_USABLE (RTM)),
__bzero_avx2_unaligned_rtm)
IFUNC_IMPL_ADD (array, i, bzero,
(CPU_FEATURE_USABLE (AVX2)
&& CPU_FEATURE_USABLE (RTM)),
__bzero_avx2_unaligned_erms_rtm)
IFUNC_IMPL_ADD (array, i, bzero,
(CPU_FEATURE_USABLE (AVX512VL)
&& CPU_FEATURE_USABLE (AVX512BW)
&& CPU_FEATURE_USABLE (BMI2)),
__bzero_evex_unaligned)
IFUNC_IMPL_ADD (array, i, bzero,
(CPU_FEATURE_USABLE (AVX512VL)
&& CPU_FEATURE_USABLE (AVX512BW)
&& CPU_FEATURE_USABLE (BMI2)),
__bzero_evex_unaligned_erms)
IFUNC_IMPL_ADD (array, i, bzero,
(CPU_FEATURE_USABLE (AVX512VL)
&& CPU_FEATURE_USABLE (AVX512BW)
&& CPU_FEATURE_USABLE (BMI2)),
__bzero_avx512_unaligned_erms)
IFUNC_IMPL_ADD (array, i, bzero,
(CPU_FEATURE_USABLE (AVX512VL)
&& CPU_FEATURE_USABLE (AVX512BW)
&& CPU_FEATURE_USABLE (BMI2)),
__bzero_avx512_unaligned)
)
/* Support sysdeps/x86_64/multiarch/rawmemchr.c. */
IFUNC_IMPL (i, name, rawmemchr,
IFUNC_IMPL_ADD (array, i, rawmemchr,

1
sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms-rtm.S
View File

@ -5,7 +5,6 @@
#define SECTION(p) p##.avx.rtm
#define MEMSET_SYMBOL(p,s) p##_avx2_##s##_rtm
#define BZERO_SYMBOL(p,s) p##_avx2_##s##_rtm
#define WMEMSET_SYMBOL(p,s) p##_avx2_##s##_rtm
#include "memset-avx2-unaligned-erms.S"

6
sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S
View File

@ -14,9 +14,6 @@
vmovd d, %xmm0; \
movq r, %rax;
# define BZERO_ZERO_VEC0() \
vpxor %xmm0, %xmm0, %xmm0
# define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
MEMSET_SET_VEC0_AND_SET_RETURN(d, r)
@ -32,9 +29,6 @@
# ifndef MEMSET_SYMBOL
# define MEMSET_SYMBOL(p,s) p##_avx2_##s
# endif
# ifndef BZERO_SYMBOL
# define BZERO_SYMBOL(p,s) p##_avx2_##s
# endif
# ifndef WMEMSET_SYMBOL
# define WMEMSET_SYMBOL(p,s) p##_avx2_##s
# endif

3
sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S
View File

@ -19,9 +19,6 @@
vpbroadcastb d, %VEC0; \
movq r, %rax
# define BZERO_ZERO_VEC0() \
vpxorq %XMM0, %XMM0, %XMM0
# define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
vpbroadcastd d, %VEC0; \
movq r, %rax

3
sysdeps/x86_64/multiarch/memset-evex-unaligned-erms.S
View File

@ -19,9 +19,6 @@
vpbroadcastb d, %VEC0; \
movq r, %rax
# define BZERO_ZERO_VEC0() \
vpxorq %XMM0, %XMM0, %XMM0
# define WMEMSET_SET_VEC0_AND_SET_RETURN(d, r) \
vpbroadcastd d, %VEC0; \
movq r, %rax

1
sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S
View File

@ -22,7 +22,6 @@
#if IS_IN (libc)
# define MEMSET_SYMBOL(p,s) p##_sse2_##s
# define BZERO_SYMBOL(p,s) MEMSET_SYMBOL (p, s)
# define WMEMSET_SYMBOL(p,s) p##_sse2_##s
# ifdef SHARED

65
sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
View File

@ -1,5 +1,5 @@
/* memset/bzero with unaligned store and rep stosb
Copyright (C) 2016-2021 Free Software Foundation, Inc.
/* memset with unaligned store and rep stosb
Copyright (C) 2016-2022 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
@ -26,10 +26,6 @@
#include <sysdep.h>
#ifndef BZERO_SYMBOL
# define BZERO_SYMBOL(p,s) MEMSET_SYMBOL (p, s)
#endif
#ifndef MEMSET_CHK_SYMBOL
# define MEMSET_CHK_SYMBOL(p,s) MEMSET_SYMBOL(p, s)
#endif
@ -134,31 +130,6 @@ ENTRY (WMEMSET_SYMBOL (__wmemset, unaligned))
END (WMEMSET_SYMBOL (__wmemset, unaligned))
#endif
ENTRY (BZERO_SYMBOL(__bzero, unaligned))
#if VEC_SIZE > 16
BZERO_ZERO_VEC0 ()
#endif
mov %RDI_LP, %RAX_LP
mov %RSI_LP, %RDX_LP
#ifndef USE_LESS_VEC_MASK_STORE
xorl %esi, %esi
#endif
cmp $VEC_SIZE, %RDX_LP
jb L(less_vec_no_vdup)
#ifdef USE_LESS_VEC_MASK_STORE
xorl %esi, %esi
#endif
#if VEC_SIZE <= 16
BZERO_ZERO_VEC0 ()
#endif
cmp $(VEC_SIZE * 2), %RDX_LP
ja L(more_2x_vec)
/* From VEC and to 2 * VEC. No branch when size == VEC_SIZE. */
VMOVU %VEC(0), (%rdi)
VMOVU %VEC(0), (VEC_SIZE * -1)(%rdi, %rdx)
VZEROUPPER_RETURN
END (BZERO_SYMBOL(__bzero, unaligned))
#if defined SHARED && IS_IN (libc)
ENTRY_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned))
cmp %RDX_LP, %RCX_LP
@ -216,31 +187,6 @@ END (__memset_erms)
END (MEMSET_SYMBOL (__memset, erms))
# endif
ENTRY_P2ALIGN (BZERO_SYMBOL(__bzero, unaligned_erms), 6)
# if VEC_SIZE > 16
BZERO_ZERO_VEC0 ()
# endif
mov %RDI_LP, %RAX_LP
mov %RSI_LP, %RDX_LP
# ifndef USE_LESS_VEC_MASK_STORE
xorl %esi, %esi
# endif
cmp $VEC_SIZE, %RDX_LP
jb L(less_vec_no_vdup)
# ifdef USE_LESS_VEC_MASK_STORE
xorl %esi, %esi
# endif
# if VEC_SIZE <= 16
BZERO_ZERO_VEC0 ()
# endif
cmp $(VEC_SIZE * 2), %RDX_LP
ja L(stosb_more_2x_vec)
/* From VEC and to 2 * VEC. No branch when size == VEC_SIZE. */
VMOVU %VEC(0), (%rdi)
VMOVU %VEC(0), (VEC_SIZE * -1)(%rdi, %rdx)
VZEROUPPER_RETURN
END (BZERO_SYMBOL(__bzero, unaligned_erms))
# if defined SHARED && IS_IN (libc)
ENTRY_CHK (MEMSET_CHK_SYMBOL (__memset_chk, unaligned_erms))
cmp %RDX_LP, %RCX_LP
@ -282,7 +228,6 @@ L(last_2x_vec):
#ifdef USE_LESS_VEC_MASK_STORE
.p2align 4,, 10
L(less_vec):
L(less_vec_no_vdup):
L(less_vec_from_wmemset):
/* Less than 1 VEC. */
# if VEC_SIZE != 16 && VEC_SIZE != 32 && VEC_SIZE != 64
@ -430,9 +375,6 @@ L(less_vec):
xmm). This is only does anything for AVX2. */
MEMSET_VDUP_TO_VEC0_LOW ()
L(less_vec_from_wmemset):
#if VEC_SIZE > 16
L(less_vec_no_vdup):
#endif
#endif
L(cross_page):
#if VEC_SIZE > 32
@ -445,9 +387,6 @@ L(cross_page):
#endif
#ifndef USE_XMM_LESS_VEC
MOVQ %XMM0, %SET_REG64
#endif
#if VEC_SIZE <= 16
L(less_vec_no_vdup):
#endif
cmpl $8, %edx
jge L(between_8_15)