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commit 83d776f979342f923b5c3d2a5b43afab841c6086
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Author: Andrew Senkevich <andrew.senkevich@intel.com>
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Date:   Sat Dec 19 02:47:28 2015 +0300
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    Added memset optimized with AVX512 for KNL hardware.
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    It shows improvement up to 28% over AVX2 memset (performance results
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    attached at <https://sourceware.org/ml/libc-alpha/2015-12/msg00052.html>).
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        * sysdeps/x86_64/multiarch/memset-avx512-no-vzeroupper.S: New file.
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        * sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Added new file.
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        * sysdeps/x86_64/multiarch/ifunc-impl-list.c: Added new tests.
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        * sysdeps/x86_64/multiarch/memset.S: Added new IFUNC branch.
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        * sysdeps/x86_64/multiarch/memset_chk.S: Likewise.
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        * sysdeps/x86/cpu-features.h (bit_Prefer_No_VZEROUPPER,
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        index_Prefer_No_VZEROUPPER): New.
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        * sysdeps/x86/cpu-features.c (init_cpu_features): Set the
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        Prefer_No_VZEROUPPER for Knights Landing.
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Index: glibc-2.17-c758a686/sysdeps/x86/cpu-features.c
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===================================================================
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--- glibc-2.17-c758a686.orig/sysdeps/x86/cpu-features.c
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+++ glibc-2.17-c758a686/sysdeps/x86/cpu-features.c
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@@ -76,6 +76,8 @@ init_cpu_features (struct cpu_features *
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 	    case 0x57:
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 	      /* Knights Landing.  Enable Silvermont optimizations.  */
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+	      cpu_features->feature[index_Prefer_No_VZEROUPPER]
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+		|= bit_Prefer_No_VZEROUPPER;
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 	    case 0x37:
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 	    case 0x4a:
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Index: glibc-2.17-c758a686/sysdeps/x86/cpu-features.h
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===================================================================
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--- glibc-2.17-c758a686.orig/sysdeps/x86/cpu-features.h
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+++ glibc-2.17-c758a686/sysdeps/x86/cpu-features.h
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@@ -33,6 +33,7 @@
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 #define bit_AVX512F_Usable		(1 << 12)
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 #define bit_AVX512DQ_Usable		(1 << 13)
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 #define bit_Prefer_MAP_32BIT_EXEC	(1 << 16)
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+#define bit_Prefer_No_VZEROUPPER	(1 << 17)
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 /* CPUID Feature flags.  */
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@@ -93,6 +94,7 @@
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 # define index_AVX512F_Usable		FEATURE_INDEX_1*FEATURE_SIZE
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 # define index_AVX512DQ_Usable		FEATURE_INDEX_1*FEATURE_SIZE
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 # define index_Prefer_MAP_32BIT_EXEC	FEATURE_INDEX_1*FEATURE_SIZE
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+# define index_Prefer_No_VZEROUPPER	FEATURE_INDEX_1*FEATURE_SIZE
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 # if defined (_LIBC) && !IS_IN (nonlib)
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 #  ifdef __x86_64__
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@@ -270,6 +272,7 @@ extern const struct cpu_features *__get_
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 # define index_AVX512F_Usable		FEATURE_INDEX_1
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 # define index_AVX512DQ_Usable		FEATURE_INDEX_1
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 # define index_Prefer_MAP_32BIT_EXEC	FEATURE_INDEX_1
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+# define index_Prefer_No_VZEROUPPER     FEATURE_INDEX_1
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 #endif	/* !__ASSEMBLER__ */
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Index: glibc-2.17-c758a686/sysdeps/x86_64/multiarch/Makefile
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===================================================================
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--- glibc-2.17-c758a686.orig/sysdeps/x86_64/multiarch/Makefile
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+++ glibc-2.17-c758a686/sysdeps/x86_64/multiarch/Makefile
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@@ -16,7 +16,8 @@ sysdep_routines += strncat-c stpncpy-c s
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 		   strcat-sse2-unaligned strncat-sse2-unaligned \
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 		   strcat-ssse3 strncat-ssse3 strlen-sse2-pminub \
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 		   strnlen-sse2-no-bsf strrchr-sse2-no-bsf strchr-sse2-no-bsf \
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-		   memcmp-ssse3 strstr-sse2-unaligned
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+		   memcmp-ssse3 strstr-sse2-unaligned \
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+		   memset-avx512-no-vzeroupper
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 ifeq (yes,$(config-cflags-sse4))
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 sysdep_routines += strcspn-c strpbrk-c strspn-c strstr-c strcasestr-c varshift
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 CFLAGS-varshift.c += -msse4
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Index: glibc-2.17-c758a686/sysdeps/x86_64/multiarch/ifunc-impl-list.c
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===================================================================
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--- glibc-2.17-c758a686.orig/sysdeps/x86_64/multiarch/ifunc-impl-list.c
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+++ glibc-2.17-c758a686/sysdeps/x86_64/multiarch/ifunc-impl-list.c
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@@ -20,6 +20,7 @@
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 #include <string.h>
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 #include <wchar.h>
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 #include <ifunc-impl-list.h>
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+#include <sysdep.h>
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 #include "init-arch.h"
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 /* Maximum number of IFUNC implementations.  */
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@@ -66,12 +67,24 @@ __libc_ifunc_impl_list (const char *name
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   IFUNC_IMPL (i, name, __memset_chk,
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 	      IFUNC_IMPL_ADD (array, i, __memset_chk, 1, __memset_chk_sse2)
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 	      IFUNC_IMPL_ADD (array, i, __memset_chk, 1,
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-			      __memset_chk_x86_64))
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+			      __memset_chk_x86_64)
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+#ifdef HAVE_AVX512_ASM_SUPPORT
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+	      IFUNC_IMPL_ADD (array, i, __memset_chk,
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+			      HAS_ARCH_FEATURE (AVX512F_Usable),
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+			      __memset_chk_avx512_no_vzeroupper)
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+#endif
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+	      )
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   /* Support sysdeps/x86_64/multiarch/memset.S.  */
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   IFUNC_IMPL (i, name, memset,
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 	      IFUNC_IMPL_ADD (array, i, memset, 1, __memset_sse2)
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-	      IFUNC_IMPL_ADD (array, i, memset, 1, __memset_x86_64))
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+	      IFUNC_IMPL_ADD (array, i, memset, 1, __memset_x86_64)
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+#ifdef HAVE_AVX512_ASM_SUPPORT
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+	      IFUNC_IMPL_ADD (array, i, memset,
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+			      HAS_ARCH_FEATURE (AVX512F_Usable),
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+			      __memset_avx512_no_vzeroupper)
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+#endif
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+	     )
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   /* Support sysdeps/x86_64/multiarch/rawmemchr.S.  */
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   IFUNC_IMPL (i, name, rawmemchr,
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Index: glibc-2.17-c758a686/sysdeps/x86_64/multiarch/memset-avx512-no-vzeroupper.S
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===================================================================
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--- /dev/null
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+++ glibc-2.17-c758a686/sysdeps/x86_64/multiarch/memset-avx512-no-vzeroupper.S
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@@ -0,0 +1,194 @@
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+/* memset optimized with AVX512 for KNL hardware.
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+   Copyright (C) 2015 Free Software Foundation, Inc.
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+   This file is part of the GNU C Library.
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+
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+   The GNU C Library is free software; you can redistribute it and/or
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+   modify it under the terms of the GNU Lesser General Public
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+   License as published by the Free Software Foundation; either
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+   version 2.1 of the License, or (at your option) any later version.
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+
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+   The GNU C Library is distributed in the hope that it will be useful,
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+   but WITHOUT ANY WARRANTY; without even the implied warranty of
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+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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+   Lesser General Public License for more details.
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+
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+   You should have received a copy of the GNU Lesser General Public
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+   License along with the GNU C Library; if not, see
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+   <http://www.gnu.org/licenses/>.  */
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+
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+#include <sysdep.h>
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+
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+#if defined HAVE_AVX512_ASM_SUPPORT && IS_IN (libc)
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+
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+#include "asm-syntax.h"
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+#ifndef MEMSET
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+# define MEMSET __memset_avx512_no_vzeroupper
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+# define MEMSET_CHK __memset_chk_avx512_no_vzeroupper
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+#endif
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+
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+	.section .text,"ax",@progbits
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+#if defined PIC
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+ENTRY (MEMSET_CHK)
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+	cmpq	%rdx, %rcx
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+	jb	HIDDEN_JUMPTARGET (__chk_fail)
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+END (MEMSET_CHK)
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+#endif
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+
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+ENTRY (MEMSET)
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+	vpxor	%xmm0, %xmm0, %xmm0
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+	vmovd	%esi, %xmm1
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+	lea	(%rdi, %rdx), %rsi
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+	mov	%rdi, %rax
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+	vpshufb	%xmm0, %xmm1, %xmm0
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+	cmp	$16, %rdx
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+	jb	L(less_16bytes)
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+	cmp	$512, %rdx
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+	vbroadcastss	%xmm0, %zmm2
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+	ja	L(512bytesormore)
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+	cmp	$256, %rdx
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+	jb	L(less_256bytes)
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+	vmovups	%zmm2, (%rdi)
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+	vmovups %zmm2, 0x40(%rdi)
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+	vmovups %zmm2, 0x80(%rdi)
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+	vmovups %zmm2, 0xC0(%rdi)
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+	vmovups %zmm2, -0x100(%rsi)
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+	vmovups %zmm2, -0xC0(%rsi)
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+	vmovups %zmm2, -0x80(%rsi)
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+	vmovups %zmm2, -0x40(%rsi)
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+	ret
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+
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+L(less_256bytes):
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+	cmp	$128, %dl
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+	jb	L(less_128bytes)
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+	vmovups	%zmm2, (%rdi)
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+	vmovups %zmm2, 0x40(%rdi)
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+	vmovups %zmm2, -0x80(%rsi)
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+	vmovups %zmm2, -0x40(%rsi)
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+	ret
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+
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+L(less_128bytes):
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+	cmp	$64, %dl
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+	jb	L(less_64bytes)
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+	vmovups	%zmm2, (%rdi)
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+	vmovups	%zmm2, -0x40(%rsi)
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+	ret
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+
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+L(less_64bytes):
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+	cmp	$32, %dl
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+	jb	L(less_32bytes)
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+	vmovdqu	%ymm2, (%rdi)
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+	vmovdqu %ymm2, -0x20(%rsi)
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+	ret
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+
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+L(less_32bytes):
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+	vmovdqu %xmm0, (%rdi)
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+	vmovdqu %xmm0, -0x10(%rsi)
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+	ret
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+
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+L(less_16bytes):
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+	cmp	$8, %dl
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+	jb	L(less_8bytes)
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+	vmovq	%xmm0, (%rdi)
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+	vmovq	%xmm0, -0x08(%rsi)
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+	ret
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+
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+L(less_8bytes):
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+	vmovd	%xmm0, %ecx
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+	cmp	$4, %dl
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+	jb	L(less_4bytes)
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+	mov	%ecx, (%rdi)
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+	mov	%ecx, -0x04(%rsi)
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+	ret
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+
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+L(less_4bytes):
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+	cmp	$2, %dl
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+	jb	L(less_2bytes)
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+	mov	%cx, (%rdi)
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+	mov	%cx, -0x02(%rsi)
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+	ret
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+
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+L(less_2bytes):
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+	cmp	$1, %dl
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+	jb	L(less_1bytes)
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+	mov	%cl, (%rdi)
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+L(less_1bytes):
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+	ret
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+
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+L(512bytesormore):
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+	mov	__x86_64_shared_cache_size_half(%rip), %rcx
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+	cmp	%rcx, %rdx
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+	ja	L(preloop_large)
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+	cmp	$1024, %rdx
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+	ja	L(1024bytesormore)
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+
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+	vmovups	%zmm2, (%rdi)
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+	vmovups	%zmm2, 0x40(%rdi)
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+	vmovups	%zmm2, 0x80(%rdi)
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+	vmovups	%zmm2, 0xC0(%rdi)
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+	vmovups	%zmm2, 0x100(%rdi)
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+	vmovups	%zmm2, 0x140(%rdi)
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+	vmovups	%zmm2, 0x180(%rdi)
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+	vmovups	%zmm2, 0x1C0(%rdi)
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+	vmovups %zmm2, -0x200(%rsi)
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+	vmovups %zmm2, -0x1C0(%rsi)
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+	vmovups %zmm2, -0x180(%rsi)
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+	vmovups %zmm2, -0x140(%rsi)
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+	vmovups %zmm2, -0x100(%rsi)
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+	vmovups %zmm2, -0xC0(%rsi)
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+	vmovups %zmm2, -0x80(%rsi)
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+	vmovups %zmm2, -0x40(%rsi)
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+	ret
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+
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+/* Align on 64 and loop with aligned stores.  */
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+L(1024bytesormore):
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+	sub	$0x100, %rsi
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+	vmovups	%zmm2, (%rax)
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+	and	$-0x40, %rdi
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+	add	$0x40, %rdi
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+
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+L(gobble_256bytes_loop):
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+	vmovaps	%zmm2, (%rdi)
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+	vmovaps	%zmm2, 0x40(%rdi)
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+	vmovaps	%zmm2, 0x80(%rdi)
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+	vmovaps	%zmm2, 0xC0(%rdi)
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+	add	$0x100, %rdi
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+	cmp	%rsi, %rdi
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+	jb	L(gobble_256bytes_loop)
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+	vmovups %zmm2, (%rsi)
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+	vmovups %zmm2, 0x40(%rsi)
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+	vmovups %zmm2, 0x80(%rsi)
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+	vmovups %zmm2, 0xC0(%rsi)
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+	ret
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+
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+/* Align on 128 and loop with non-temporal stores.  */
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+L(preloop_large):
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+	and	$-0x80, %rdi
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+	add	$0x80, %rdi
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+	vmovups	%zmm2, (%rax)
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+	vmovups	%zmm2, 0x40(%rax)
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+	sub	$0x200, %rsi
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+
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+L(gobble_512bytes_nt_loop):
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+	vmovntdq %zmm2, (%rdi)
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+	vmovntdq %zmm2, 0x40(%rdi)
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+	vmovntdq %zmm2, 0x80(%rdi)
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+	vmovntdq %zmm2, 0xC0(%rdi)
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+	vmovntdq %zmm2, 0x100(%rdi)
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+	vmovntdq %zmm2, 0x140(%rdi)
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+	vmovntdq %zmm2, 0x180(%rdi)
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+	vmovntdq %zmm2, 0x1C0(%rdi)
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+	add	$0x200, %rdi
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+	cmp	%rsi, %rdi
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+	jb	L(gobble_512bytes_nt_loop)
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+	sfence
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+	vmovups %zmm2, (%rsi)
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+	vmovups %zmm2, 0x40(%rsi)
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+	vmovups %zmm2, 0x80(%rsi)
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+	vmovups %zmm2, 0xC0(%rsi)
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+	vmovups	%zmm2, 0x100(%rsi)
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+	vmovups	%zmm2, 0x140(%rsi)
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+	vmovups	%zmm2, 0x180(%rsi)
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+	vmovups	%zmm2, 0x1C0(%rsi)
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+	ret
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+END (MEMSET)
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+#endif
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Index: glibc-2.17-c758a686/sysdeps/x86_64/multiarch/memset.S
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===================================================================
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--- glibc-2.17-c758a686.orig/sysdeps/x86_64/multiarch/memset.S
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+++ glibc-2.17-c758a686/sysdeps/x86_64/multiarch/memset.S
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@@ -29,6 +29,13 @@ ENTRY(memset)
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 	HAS_ARCH_FEATURE (Prefer_SSE_for_memop)
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 	jz	2f
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 	leaq	__memset_sse2(%rip), %rax
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+#ifdef HAVE_AVX512_ASM_SUPPORT
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+	HAS_ARCH_FEATURE (AVX512F_Usable)
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+	jz	2f
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+	HAS_ARCH_FEATURE (Prefer_No_VZEROUPPER)
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+	jz	2f
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+	leaq	__memset_avx512_no_vzeroupper(%rip), %rax
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+#endif
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 2:	ret
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 END(memset)
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Index: glibc-2.17-c758a686/sysdeps/x86_64/multiarch/memset_chk.S
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===================================================================
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--- glibc-2.17-c758a686.orig/sysdeps/x86_64/multiarch/memset_chk.S
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+++ glibc-2.17-c758a686/sysdeps/x86_64/multiarch/memset_chk.S
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@@ -30,6 +30,13 @@ ENTRY(__memset_chk)
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 	HAS_ARCH_FEATURE (Prefer_SSE_for_memop)
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 	jz	2f
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 	leaq	__memset_chk_sse2(%rip), %rax
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+#ifdef HAVE_AVX512_ASM_SUPPORT
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+	HAS_ARCH_FEATURE (AVX512F_Usable)
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+	jz	2f
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+	HAS_ARCH_FEATURE (Prefer_No_VZEROUPPER)
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+	jz	2f
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+	leaq	__memset_chk_avx512_no_vzeroupper(%rip), %rax
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+#endif
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 2:	ret
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 END(__memset_chk)
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