x86_64: Remove bzero optimization

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.

sysdeps/x86_64/bzero.S

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

sysdeps/x86_64/memset.S

@@ -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) 2002-2022 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)

sysdeps/x86_64/multiarch/Makefile

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

sysdeps/x86_64/multiarch/bzero.c

@@ -1,106 +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
-
-# 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

sysdeps/x86_64/multiarch/ifunc-impl-list.c

@@ -291,48 +291,6 @@ __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,

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

@@ -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"

sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S

@@ -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

sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S

@@ -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

sysdeps/x86_64/multiarch/memset-evex-unaligned-erms.S

@@ -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

sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S

@@ -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

sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S

@@ -1,4 +1,4 @@
-/* memset/bzero with unaligned store and rep stosb
+/* memset with unaligned store and rep stosb
    Copyright (C) 2016-2022 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -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)