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Re: Subject: [PATCH] Add x86-64 memset with unaligned store and rep stosb
- From: Carlos O'Donell <carlos at redhat dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Wed, 30 Mar 2016 19:18:38 -0400
- Subject: Re: Subject: [PATCH] Add x86-64 memset with unaligned store and rep stosb
- Authentication-results: sourceware.org; auth=none
- References: <CAMe9rOr9r5s8mTThYDomrJsBEk_zQLpMQYeQ6rJ41S3VXS-Bmg at mail dot gmail dot com>
On 03/29/2016 03:23 PM, H.J. Lu wrote:
> The goal of this patch is to replace SSE2 and AVX2 memset.S
> with faster and smaller alternatives, also support 64-byte vector
> register size. bench-memset data on various Intel and AMD
> processors is at
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=19881
>
> Any comments, feedbacks?
Caveats about Penryn being slower apply here, and I expect your answer
is the same: the selection of the ifunc will not change, and so Penryn
will not use the newer versions.
This looks good to me.
Again, same question about thresholding below.
> -- H.J.
>
>
> 0001-Add-x86-64-memset-with-unaligned-store-and-rep-stosb.patch
>
>
> From d0d3495951be16568656971dd2c825da68c2660c Mon Sep 17 00:00:00 2001
> From: "H.J. Lu" <hjl.tools@gmail.com>
> Date: Fri, 25 Mar 2016 08:20:17 -0700
> Subject: [PATCH] Add x86-64 memset with unaligned store and rep stosb
>
> Implement x86-64 memset with unaligned store and rep movsb. Support
> 16-byte, 32-byte and 64-byte vector register sizes. A single file
> provides 2 implementations of memset, one with rep stosb and the other
> without rep stosb. They share the same codes when size is between 2
> times of vector register size and REP_STOSB_THRESHOLD which is 1KB for
> 16-byte vector register size and scaled up by larger vector register
> size.
>
> Key features:
>
> 1. Use overlapping store to avoid branch.
> 2. For size <= 4 times of vector register size, fully unroll the loop.
> 3. For size > 4 times of vector register size, store 4 times of vector
> register size at a time.
>
> [BZ #19881]
> * sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add
> memset-sse2-unaligned-erms, memset-avx2-unaligned-erms and
> memset-avx512-unaligned-erms.
> * sysdeps/x86_64/multiarch/ifunc-impl-list.c
> (__libc_ifunc_impl_list): Test __memset_chk_sse2_unaligned,
> __memset_chk_sse2_unaligned_erms, __memset_chk_avx2_unaligned,
> __memset_chk_avx2_unaligned_erms, __memset_chk_avx512_unaligned,
> __memset_chk_avx512_unaligned_erms, __memset_sse2_unaligned,
> __memset_sse2_unaligned_erms, __memset_erms,
> __memset_avx2_unaligned, __memset_avx2_unaligned_erms,
> __memset_avx512_unaligned_erms and __memset_avx512_unaligned.
> * sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S: New
> file.
> * sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S:
> Likewise.
> * sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S:
> Likewise.
> * sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S:
> Likewise.
>
> Memset
> ---
> sysdeps/x86_64/multiarch/Makefile | 5 +-
> sysdeps/x86_64/multiarch/ifunc-impl-list.c | 33 +++
> .../x86_64/multiarch/memset-avx2-unaligned-erms.S | 14 ++
> .../multiarch/memset-avx512-unaligned-erms.S | 17 ++
> .../x86_64/multiarch/memset-sse2-unaligned-erms.S | 16 ++
> .../x86_64/multiarch/memset-vec-unaligned-erms.S | 246 +++++++++++++++++++++
> 6 files changed, 330 insertions(+), 1 deletion(-)
> create mode 100644 sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S
> create mode 100644 sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S
> create mode 100644 sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S
> create mode 100644 sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
>
> diff --git a/sysdeps/x86_64/multiarch/Makefile b/sysdeps/x86_64/multiarch/Makefile
> index ef4dbc0..8878efb 100644
> --- a/sysdeps/x86_64/multiarch/Makefile
> +++ b/sysdeps/x86_64/multiarch/Makefile
> @@ -23,7 +23,10 @@ sysdep_routines += strncat-c stpncpy-c strncpy-c strcmp-ssse3 \
> memset-avx512-no-vzeroupper \
> memmove-sse2-unaligned-erms \
> memmove-avx-unaligned-erms \
> - memmove-avx512-unaligned-erms
> + memmove-avx512-unaligned-erms \
> + memset-sse2-unaligned-erms \
> + memset-avx2-unaligned-erms \
> + memset-avx512-unaligned-erms
OK.
> CFLAGS-varshift.c += -msse4
> CFLAGS-strcspn-c.c += -msse4
> CFLAGS-strpbrk-c.c += -msse4
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index 9204da4..1e880f6 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -118,12 +118,28 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> IFUNC_IMPL (i, name, __memset_chk,
> IFUNC_IMPL_ADD (array, i, __memset_chk, 1,
> __memset_chk_sse2)
> + IFUNC_IMPL_ADD (array, i, __memset_chk, 1,
> + __memset_chk_sse2_unaligned)
> + IFUNC_IMPL_ADD (array, i, __memset_chk, 1,
> + __memset_chk_sse2_unaligned_erms)
> IFUNC_IMPL_ADD (array, i, __memset_chk,
> HAS_ARCH_FEATURE (AVX2_Usable),
> __memset_chk_avx2)
> + IFUNC_IMPL_ADD (array, i, __memset_chk,
> + HAS_ARCH_FEATURE (AVX2_Usable),
> + __memset_chk_avx2_unaligned)
> + IFUNC_IMPL_ADD (array, i, __memset_chk,
> + HAS_ARCH_FEATURE (AVX2_Usable),
> + __memset_chk_avx2_unaligned_erms)
> #ifdef HAVE_AVX512_ASM_SUPPORT
> IFUNC_IMPL_ADD (array, i, __memset_chk,
> HAS_ARCH_FEATURE (AVX512F_Usable),
> + __memset_chk_avx512_unaligned_erms)
> + IFUNC_IMPL_ADD (array, i, __memset_chk,
> + HAS_ARCH_FEATURE (AVX512F_Usable),
> + __memset_chk_avx512_unaligned)
> + IFUNC_IMPL_ADD (array, i, __memset_chk,
> + HAS_ARCH_FEATURE (AVX512F_Usable),
> __memset_chk_avx512_no_vzeroupper)
> #endif
> )
> @@ -131,12 +147,29 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> /* Support sysdeps/x86_64/multiarch/memset.S. */
> IFUNC_IMPL (i, name, memset,
> IFUNC_IMPL_ADD (array, i, memset, 1, __memset_sse2)
> + IFUNC_IMPL_ADD (array, i, memset, 1,
> + __memset_sse2_unaligned)
> + IFUNC_IMPL_ADD (array, i, memset, 1,
> + __memset_sse2_unaligned_erms)
> + IFUNC_IMPL_ADD (array, i, memset, 1, __memset_erms)
> IFUNC_IMPL_ADD (array, i, memset,
> HAS_ARCH_FEATURE (AVX2_Usable),
> __memset_avx2)
> + IFUNC_IMPL_ADD (array, i, memset,
> + HAS_ARCH_FEATURE (AVX2_Usable),
> + __memset_avx2_unaligned)
> + IFUNC_IMPL_ADD (array, i, memset,
> + HAS_ARCH_FEATURE (AVX2_Usable),
> + __memset_avx2_unaligned_erms)
> #ifdef HAVE_AVX512_ASM_SUPPORT
> IFUNC_IMPL_ADD (array, i, memset,
> HAS_ARCH_FEATURE (AVX512F_Usable),
> + __memset_avx512_unaligned_erms)
> + IFUNC_IMPL_ADD (array, i, memset,
> + HAS_ARCH_FEATURE (AVX512F_Usable),
> + __memset_avx512_unaligned)
> + IFUNC_IMPL_ADD (array, i, memset,
> + HAS_ARCH_FEATURE (AVX512F_Usable),
> __memset_avx512_no_vzeroupper)
> #endif
> )
> diff --git a/sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S
> new file mode 100644
> index 0000000..e0dc565
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/memset-avx2-unaligned-erms.S
> @@ -0,0 +1,14 @@
> +#define VEC_SIZE 32
> +#define VEC(i) ymm##i
> +#define VMOVU vmovdqu
> +#define VMOVA vmovdqa
> +
> +#define VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> + vmovd d, %xmm0; \
> + movq r, %rax; \
> + vpbroadcastb %xmm0, %ymm0
> +
> +#define SECTION(p) p##.avx
> +#define MEMSET_SYMBOL(p,s) p##_avx2_##s
OK.
> +
> +#include "memset-vec-unaligned-erms.S"
> diff --git a/sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S
> new file mode 100644
> index 0000000..72f4095
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S
> @@ -0,0 +1,17 @@
> +#ifdef HAVE_AVX512_ASM_SUPPORT
> +# define VEC_SIZE 64
> +# define VEC(i) zmm##i
> +# define VMOVU vmovdqu64
> +# define VMOVA vmovdqa64
> +
> +# define VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> + vmovd d, %xmm0; \
> + movq r, %rax; \
> + vpbroadcastb %xmm0, %xmm0; \
> + vpbroadcastq %xmm0, %zmm0
> +
> +# define SECTION(p) p##.avx512
> +# define MEMSET_SYMBOL(p,s) p##_avx512_##s
OK.
> +
> +# include "memset-vec-unaligned-erms.S"
> +#endif
> diff --git a/sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S
> new file mode 100644
> index 0000000..437a858
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/memset-sse2-unaligned-erms.S
> @@ -0,0 +1,16 @@
> +#define VEC_SIZE 16
> +#define VEC(i) xmm##i
> +#define VMOVU movdqu
> +#define VMOVA movdqa
> +
> +#define VDUP_TO_VEC0_AND_SET_RETURN(d, r) \
> + movd d, %xmm0; \
> + movq r, %rax; \
> + punpcklbw %xmm0, %xmm0; \
> + punpcklwd %xmm0, %xmm0; \
> + pshufd $0, %xmm0, %xmm0
> +
> +#define SECTION(p) p
> +#define MEMSET_SYMBOL(p,s) p##_sse2_##s
OK.
> +
> +#include "memset-vec-unaligned-erms.S"
> diff --git a/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
> new file mode 100644
> index 0000000..dd04789
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/memset-vec-unaligned-erms.S
> @@ -0,0 +1,246 @@
> +/* memset/bzero with unaligned store and rep stosb
> + Copyright (C) 2016 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
> + <http://www.gnu.org/licenses/>. */
> +
> +/* memset is implemented as:
> + 1. Use overlapping store to avoid branch.
> + 2. Force 32-bit displacement for branches to avoid long nop between
> + instructions.
> + 3. If size is less than VEC, use integer register stores.
> + 4. If size is from VEC_SIZE to 2 * VEC_SIZE, use 2 VEC stores.
> + 5. If size is from 2 * VEC_SIZE to 4 * VEC_SIZE, use 4 VEC stores.
> + 6. If size is more to 4 * VEC_SIZE, align to 4 * VEC_SIZE with
> + 4 VEC stores and store 4 * VEC at a time until done.
> + */
Use GNU formatting please.
e.g.
/* foo */
not
/* foo
*/
> +#include <sysdep.h>
> +
> +#ifndef VZEROUPPER
> +# if VEC_SIZE > 16
> +# define VZEROUPPER vzeroupper
> +# else
> +# define VZEROUPPER
> +# endif
> +#endif
> +
> +#ifndef VZEROUPPER_SHORT_RETURN
> +# if VEC_SIZE > 16
> +# define VZEROUPPER_SHORT_RETURN vzeroupper
> +# else
> +# define VZEROUPPER_SHORT_RETURN rep
> +# endif
> +#endif
> +
> +#ifndef MOVQ
> +# if VEC_SIZE > 16
> +# define MOVQ vmovq
> +# else
> +# define MOVQ movq
> +# endif
> +#endif
> +
> +/* Threshold to use Enhanced REP STOSB. */
> +#ifndef REP_STOSB_THRESHOLD
> +# define REP_STOSB_THRESHOLD (1024 * (VEC_SIZE / 16))
Same question as your other patch. How are we selecting this threshold?
> +#endif
> +
> +#ifndef SECTION
> +# error SECTION is not defined!
> +#endif
> +
> +#if !defined USE_MULTIARCH && IS_IN (libc)
> + .section SECTION(.text),"ax",@progbits
> +ENTRY (__bzero)
> + movq %rdi, %rax /* Set return value. */
> + movq %rsi, %rdx /* Set n. */
> + pxor %xmm0, %xmm0
> + jmp L(entry_from_bzero)
> +END (__bzero)
> +weak_alias (__bzero, bzero)
> +#endif
> +
> +#if defined SHARED && IS_IN (libc)
> +ENTRY_CHK (MEMSET_SYMBOL (__memset_chk, unaligned))
> + cmpq %rdx, %rcx
> + jb HIDDEN_JUMPTARGET (__chk_fail)
> +END_CHK (MEMSET_SYMBOL (__memset_chk, unaligned))
> +#endif
> +
> +ENTRY (MEMSET_SYMBOL (__memset, unaligned))
> +L(memset_entry):
> + VDUP_TO_VEC0_AND_SET_RETURN (%esi, %rdi)
> +L(entry_from_bzero):
> + cmpq $VEC_SIZE, %rdx
> + jb L(less_vec)
> + cmpq $(VEC_SIZE * 2), %rdx
> + ja L(more_2x_vec)
> + /* From VEC and to 2 * VEC. No branch when size == VEC_SIZE. */
> + VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx)
> + VMOVU %VEC(0), (%rdi)
> + VZEROUPPER
> + ret
> +END (MEMSET_SYMBOL (__memset, unaligned))
> +
> +#if VEC_SIZE == 16
> +/* Only used to measure performance of REP STOSB. */
> +ENTRY (__memset_erms)
> +#else
> +/* Provide a symbol to debugger. */
> +ENTRY (MEMSET_SYMBOL (__memset, erms))
> +#endif
> +L(stosb):
> + movq %rdx, %rcx
> + movzbl %sil, %eax
> + movq %rdi, %rdx
> + rep stosb
> + movq %rdx, %rax
> + ret
> +#if VEC_SIZE == 16
> +END (__memset_erms)
> +#else
> +END (MEMSET_SYMBOL (__memset, erms))
> +#endif
> +
> +#if defined SHARED && IS_IN (libc)
> +ENTRY_CHK (MEMSET_SYMBOL (__memset_chk, unaligned_erms))
> + cmpq %rdx, %rcx
> + jb HIDDEN_JUMPTARGET (__chk_fail)
> +END_CHK (MEMSET_SYMBOL (__memset_chk, unaligned_erms))
> +#endif
> +
> +ENTRY (MEMSET_SYMBOL (__memset, unaligned_erms))
> + VDUP_TO_VEC0_AND_SET_RETURN (%esi, %rdi)
> + cmpq $VEC_SIZE, %rdx
> + jb L(less_vec)
> + cmpq $(VEC_SIZE * 2), %rdx
> + ja L(stosb_more_2x_vec)
> + /* From VEC and to 2 * VEC. No branch when size == VEC_SIZE. */
> + VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx)
> + VMOVU %VEC(0), (%rdi)
> + VZEROUPPER
> + ret
> +
> + .p2align 4
> +L(stosb_more_2x_vec):
> + cmpq $REP_STOSB_THRESHOLD, %rdx
> + /* Force 32-bit displacement to avoid long nop between
> + instructions. */
> + ja.d32 L(stosb)
> + .p2align 4
> +L(more_2x_vec):
> + cmpq $(VEC_SIZE * 4), %rdx
> + ja L(loop_start)
> + VMOVU %VEC(0), (%rdi)
> + VMOVU %VEC(0), VEC_SIZE(%rdi)
> + VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx)
> + VMOVU %VEC(0), -(VEC_SIZE * 2)(%rdi,%rdx)
> +L(return):
> + VZEROUPPER
> + ret
> +
> + .p2align 4
> +L(loop_start):
> + leaq (VEC_SIZE * 4)(%rdi), %rcx
> + VMOVU %VEC(0), (%rdi)
> + andq $-(VEC_SIZE * 4), %rcx
> + VMOVU %VEC(0), -VEC_SIZE(%rdi,%rdx)
> + VMOVU %VEC(0), VEC_SIZE(%rdi)
> + VMOVU %VEC(0), -(VEC_SIZE * 2)(%rdi,%rdx)
> + VMOVU %VEC(0), (VEC_SIZE * 2)(%rdi)
> + VMOVU %VEC(0), -(VEC_SIZE * 3)(%rdi,%rdx)
> + VMOVU %VEC(0), (VEC_SIZE * 3)(%rdi)
> + VMOVU %VEC(0), -(VEC_SIZE * 4)(%rdi,%rdx)
> + addq %rdi, %rdx
> + andq $-(VEC_SIZE * 4), %rdx
> + cmpq %rdx, %rcx
> +# if VEC_SIZE == 32 || VEC_SIZE == 64
> + /* Force 32-bit displacement to avoid long nop between
> + instructions. */
> + je.d32 L(return)
> +# else
> + je L(return)
> +# endif
> + .p2align 4
> +L(loop):
> + VMOVA %VEC(0), (%rcx)
> + VMOVA %VEC(0), VEC_SIZE(%rcx)
> + VMOVA %VEC(0), (VEC_SIZE * 2)(%rcx)
> + VMOVA %VEC(0), (VEC_SIZE * 3)(%rcx)
> + addq $(VEC_SIZE * 4), %rcx
> + cmpq %rcx, %rdx
> + jne L(loop)
> + VZEROUPPER_SHORT_RETURN
> + ret
> +L(less_vec):
> + /* Less than 1 VEC. */
> +# if VEC_SIZE != 16 && VEC_SIZE != 32 && VEC_SIZE != 64
> +# error Unsupported VEC_SIZE!
> +# endif
> +# if VEC_SIZE > 32
> + cmpb $32, %dl
> + jae L(between_32_63)
> +# endif
> +# if VEC_SIZE > 16
> + cmpb $16, %dl
> + jae L(between_16_31)
> +# endif
> + MOVQ %xmm0, %rcx
> + cmpb $8, %dl
> + jae L(between_8_15)
> + cmpb $4, %dl
> + jae L(between_4_7)
> + cmpb $1, %dl
> + ja L(between_2_3)
> + jb 1f
> + movb %cl, (%rdi)
> +1:
> + VZEROUPPER
> + ret
> +# if VEC_SIZE > 32
> + /* From 32 to 63. No branch when size == 32. */
> +L(between_32_63):
> + vmovdqu %ymm0, -32(%rdi,%rdx)
> + vmovdqu %ymm0, (%rdi)
> + VZEROUPPER
> + ret
> +# endif
> +# if VEC_SIZE > 16
> + /* From 16 to 31. No branch when size == 16. */
> +L(between_16_31):
> + vmovdqu %xmm0, -16(%rdi,%rdx)
> + vmovdqu %xmm0, (%rdi)
> + VZEROUPPER
> + ret
> +# endif
> + /* From 8 to 15. No branch when size == 8. */
> +L(between_8_15):
> + movq %rcx, -8(%rdi,%rdx)
> + movq %rcx, (%rdi)
> + VZEROUPPER
> + ret
> +L(between_4_7):
> + /* From 4 to 7. No branch when size == 4. */
> + movl %ecx, -4(%rdi,%rdx)
> + movl %ecx, (%rdi)
> + VZEROUPPER
> + ret
> +L(between_2_3):
> + /* From 2 to 3. No branch when size == 2. */
> + movw %cx, -2(%rdi,%rdx)
> + movw %cx, (%rdi)
> + VZEROUPPER
> + ret
> +END (MEMSET_SYMBOL (__memset, unaligned_erms))
> -- 2.5.5
OK.
--
Cheers,
Carlos.