[PATCH RFC] Imporve 64bit memset performance for Haswell CPU with AVX2 instruction

[Marko Myllynen]

Hi,

On 2014-04-04 10:34, ling.ma.program@gmail.com wrote:
> From: Ling Ma <ling.ml@alibaba-inc.com>
> 
> In this patch we manage to reduce miss branch prediction by 
> avoid using branch instructions and force destination to be aligned
> with avx instruction. 
> 
> ---
>  In this version we removed prefetch and append vmovd.
> 
>  ChangeLog                              |   9 ++
>  sysdeps/x86_64/multiarch/Makefile      |   4 +-
>  sysdeps/x86_64/multiarch/memset-avx2.S | 192 +++++++++++++++++++++++++++++++++
>  sysdeps/x86_64/multiarch/memset.S      |  59 ++++++++++
>  sysdeps/x86_64/multiarch/memset_chk.S  |  44 ++++++++
>  5 files changed, 307 insertions(+), 1 deletion(-)
>  create mode 100644 sysdeps/x86_64/multiarch/memset-avx2.S
>  create mode 100644 sysdeps/x86_64/multiarch/memset.S
>  create mode 100644 sysdeps/x86_64/multiarch/memset_chk.S
> 
> diff --git a/sysdeps/x86_64/multiarch/memset-avx2.S b/sysdeps/x86_64/multiarch/memset-avx2.S
> new file mode 100644
> index 0000000..08e8ee8
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/memset-avx2.S
> @@ -0,0 +1,192 @@
> +/* memset with AVX2
> +   Copyright (C) 2014 Free Software Foundation, Inc.
> +   Contributed by Alibaba Group.
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <sysdep.h>
> +
> +#if !defined NOT_IN_libc
> +
> +#include "asm-syntax.h"
> +#ifndef ALIGN
> +# define ALIGN(n)	.p2align n
> +#endif
> +#ifndef MEMSET
> +# define MEMSET	__memset_avx2
> +# define MEMSET_CHK	__memset_chk_avx2
> +#endif
> +
> +	.section .text.avx2,"ax",@progbits
> +#if defined PIC
> +ENTRY (MEMSET_CHK)
> +	cmpq	%rdx, %rcx
> +	jb	HIDDEN_JUMPTARGET (__chk_fail)
> +END (MEMSET_CHK)
> +#endif
> +
> +ENTRY (MEMSET)
> +	vpxor	%xmm0, %xmm0, %xmm0
> +	vmovd %esi, %xmm1
> +	lea	(%rdi, %rdx), %r8
> +	vpshufb	%xmm0, %xmm1, %xmm0
> +	mov	%rdi, %rax
> +	cmp	$256, %rdx
> +	jae	L(256bytesormore)
> +	vmovd %xmm0, %rcx
> +	cmp	$128, %rdx
> +	jb	L(less_128bytes)
> +	vmovups %xmm0, (%rdi)
> +	vmovups %xmm0, 0x10(%rdi)
> +	vmovups %xmm0, 0x20(%rdi)
> +	vmovups %xmm0, 0x30(%rdi)
> +	vmovups %xmm0, 0x40(%rdi)
> +	vmovups %xmm0, 0x50(%rdi)
> +	vmovups %xmm0, 0x60(%rdi)
> +	vmovups %xmm0, 0x70(%rdi)
> +	vmovups %xmm0, -0x80(%r8)
> +	vmovups %xmm0, -0x70(%r8)
> +	vmovups %xmm0, -0x60(%r8)
> +	vmovups %xmm0, -0x50(%r8)
> +	vmovups %xmm0, -0x40(%r8)
> +	vmovups %xmm0, -0x30(%r8)
> +	vmovups %xmm0, -0x20(%r8)
> +	vmovups %xmm0, -0x10(%r8)
> +	ret
> +	ALIGN(4)
> +L(less_128bytes):
> +	cmp	$64, %edx
> +	jb	L(less_64bytes)
> +	vmovups %xmm0, (%rdi)
> +	vmovups %xmm0, 0x10(%rdi)
> +	vmovups %xmm0, 0x20(%rdi)
> +	vmovups %xmm0, 0x30(%rdi)
> +	vmovups %xmm0, -0x40(%r8)
> +	vmovups %xmm0, -0x30(%r8)
> +	vmovups %xmm0, -0x20(%r8)
> +	vmovups %xmm0, -0x10(%r8)
> +	ret
> +	ALIGN(4)
> +L(less_64bytes):
> +	cmp	$32, %edx
> +	jb	L(less_32bytes)
> +	vmovups %xmm0, (%rdi)
> +	vmovups %xmm0, 0x10(%rdi)
> +	vmovups %xmm0, -0x20(%r8)
> +	vmovups %xmm0, -0x10(%r8)
> +	ret
> +	ALIGN(4)
> +L(less_32bytes):
> +	cmp	$16, %edx
> +	jb	L(less_16bytes)
> +	vmovups %xmm0, (%rdi)
> +	vmovups %xmm0, -0x10(%r8)
> +	ret
> +	ALIGN(4)
> +L(less_16bytes):
> +	cmp	$8, %edx
> +	jb	L(less_8bytes)
> +	mov %rcx, (%rdi)
> +	mov %rcx, -0x08(%r8)
> +	ret
> +	ALIGN(4)
> +L(less_8bytes):
> +	cmp	$4, %edx
> +	jb	L(less_4bytes)
> +	mov %ecx, (%rdi)
> +	mov %ecx, -0x04(%r8)
> +	ALIGN(4)
> +L(less_4bytes):
> +	cmp	$2, %edx
> +	jb	L(less_2bytes)
> +	mov	%cx, (%rdi)
> +	mov	%cx, -0x02(%r8)
> +	ret
> +	ALIGN(4)
> +L(less_2bytes):
> +	cmp	$1, %edx
> +	jb	L(less_1bytes)
> +	mov	%cl, (%rdi)
> +L(less_1bytes):
> +	ret
> +
> +	ALIGN(4)
> +L(256bytesormore):
> +	vinserti128 $1, %xmm0, %ymm0, %ymm0

this breaks build on RHEL 6 x86_64:

../sysdeps/x86_64/multiarch/memset-avx2.S:
../sysdeps/x86_64/multiarch/memset-avx2.S: Assembler messages:
Assembler messages:
../sysdeps/x86_64/multiarch/memset-avx2.S:132:
../sysdeps/x86_64/multiarch/memset-avx2.S:132: Error: Error: no such
instruction: `vinserti128 $1,%xmm0,%ymm0,%ymm0'no such instruction:
`vinserti128 $1,%xmm0,%ymm0,%ymm0'

Cheers,

-- 
Marko Myllynen