[PATCH] x86_64: Implement evex512 version of strchrnul, strchr and wcschr
Noah Goldstein
goldstein.w.n@gmail.com
Thu Sep 22 00:50:16 GMT 2022
On Wed, Sep 21, 2022 at 5:17 PM Sunil K Pandey via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> This patch implements following evex512 version of string functions.
> evex512 version takes up to 30% less cycle as compared to evex,
> depending on length and alignment.
Please attach benchmark numbers.
>
> - strchrnul function using 512 bit vectors.
> - strchr function using 512 bit vectors.
> - wcschr function using 512 bit vectors.
>
> Code size data:
>
> strchrnul-evex.o 615 byte
> strchrnul-evex512.o 573 byte (-7%)
>
> strchr-evex.o 670 byte
> strchr-evex512.o 616 byte (-8%)
>
> wcschr-evex.o 678 byte
> wcschr-evex512.o 620 byte (-9%)
>
> Placeholder function, not used by any processor at the moment.
> ---
> sysdeps/x86_64/multiarch/Makefile | 3 +
> sysdeps/x86_64/multiarch/ifunc-impl-list.c | 12 +
> sysdeps/x86_64/multiarch/strchr-evex-base.S | 294 +++++++++++++++++++
> sysdeps/x86_64/multiarch/strchr-evex512.S | 7 +
> sysdeps/x86_64/multiarch/strchrnul-evex512.S | 8 +
> sysdeps/x86_64/multiarch/wcschr-evex512.S | 8 +
> 6 files changed, 332 insertions(+)
> create mode 100644 sysdeps/x86_64/multiarch/strchr-evex-base.S
> create mode 100644 sysdeps/x86_64/multiarch/strchr-evex512.S
> create mode 100644 sysdeps/x86_64/multiarch/strchrnul-evex512.S
> create mode 100644 sysdeps/x86_64/multiarch/wcschr-evex512.S
>
> diff --git a/sysdeps/x86_64/multiarch/Makefile b/sysdeps/x86_64/multiarch/Makefile
> index df4601c294..89b58fa557 100644
> --- a/sysdeps/x86_64/multiarch/Makefile
> +++ b/sysdeps/x86_64/multiarch/Makefile
> @@ -60,11 +60,13 @@ sysdep_routines += \
> strchr-avx2 \
> strchr-avx2-rtm \
> strchr-evex \
> + strchr-evex512 \
> strchr-sse2 \
> strchr-sse2-no-bsf \
> strchrnul-avx2 \
> strchrnul-avx2-rtm \
> strchrnul-evex \
> + strchrnul-evex512 \
> strchrnul-sse2 \
> strcmp-avx2 \
> strcmp-avx2-rtm \
> @@ -129,6 +131,7 @@ sysdep_routines += \
> wcschr-avx2 \
> wcschr-avx2-rtm \
> wcschr-evex \
> + wcschr-evex512 \
> wcschr-sse2 \
> wcscmp-avx2 \
> wcscmp-avx2-rtm \
> diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> index a71444eccb..bce1d15171 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -518,6 +518,10 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> && CPU_FEATURE_USABLE (AVX512BW)
> && CPU_FEATURE_USABLE (BMI2)),
> __strchr_evex)
> + X86_IFUNC_IMPL_ADD_V4 (array, i, strchr,
> + (CPU_FEATURE_USABLE (AVX512VL)
> + && CPU_FEATURE_USABLE (AVX512BW)),
> + __strchr_evex512)
> X86_IFUNC_IMPL_ADD_V3 (array, i, strchr,
> (CPU_FEATURE_USABLE (AVX2)
> && CPU_FEATURE_USABLE (BMI2)),
> @@ -543,6 +547,10 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> && CPU_FEATURE_USABLE (AVX512BW)
> && CPU_FEATURE_USABLE (BMI2)),
> __strchrnul_evex)
> + X86_IFUNC_IMPL_ADD_V4 (array, i, strchrnul,
> + (CPU_FEATURE_USABLE (AVX512VL)
> + && CPU_FEATURE_USABLE (AVX512BW)),
> + __strchrnul_evex512)
> X86_IFUNC_IMPL_ADD_V3 (array, i, strchrnul,
> (CPU_FEATURE_USABLE (AVX2)
> && CPU_FEATURE_USABLE (BMI2)),
> @@ -753,6 +761,10 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> && CPU_FEATURE_USABLE (AVX512BW)
> && CPU_FEATURE_USABLE (BMI2)),
> __wcschr_evex)
> + X86_IFUNC_IMPL_ADD_V4 (array, i, wcschr,
> + (CPU_FEATURE_USABLE (AVX512VL)
> + && CPU_FEATURE_USABLE (AVX512BW)),
> + __wcschr_evex512)
> X86_IFUNC_IMPL_ADD_V3 (array, i, wcschr,
> (CPU_FEATURE_USABLE (AVX2)
> && CPU_FEATURE_USABLE (BMI2)),
> diff --git a/sysdeps/x86_64/multiarch/strchr-evex-base.S b/sysdeps/x86_64/multiarch/strchr-evex-base.S
> new file mode 100644
> index 0000000000..919dafc8b6
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/strchr-evex-base.S
> @@ -0,0 +1,294 @@
> +/* Placeholder function, not used by any processor at the moment.
> + 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/>. */
> +
> +/* UNUSED. Exists purely as reference implementation. */
> +
> +#include <isa-level.h>
> +
> +#if ISA_SHOULD_BUILD (4)
> +
> +# include <sysdep.h>
> +
> +# ifdef USE_AS_WCSCHR
> +# define CHAR_REG esi
> +# define CHAR_SIZE 4
> +# define VPBROADCAST vpbroadcastd
> +# define VPCMP vpcmpd
> +# define VPMINU vpminud
> +# define VPTESTN vptestnmd
> +# else
> +# define CHAR_REG sil
> +# define CHAR_SIZE 1
> +# define VPBROADCAST vpbroadcastb
> +# define VPCMP vpcmpb
> +# define VPMINU vpminub
> +# define VPTESTN vptestnmb
> +# endif
> +
> +# define PAGE_SIZE 4096
> +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
> +# define XMM1 xmm17
> +
> +# if VEC_SIZE == 64
> +# define KMOV kmovq
> +# define KORTEST kortestq
> +# define RAX rax
> +# define RCX rcx
> +# define RDX rdx
> +# define SHR shrq
> +# define TEXTSUFFIX evex512
> +# define VMM0 zmm16
> +# define VMM1 zmm17
> +# define VMM2 zmm18
> +# define VMM3 zmm19
> +# define VMM4 zmm20
> +# define VMM5 zmm21
> +# define VMOVA vmovdqa64
> +# define VMOVU vmovdqu64
> +
> +# elif VEC_SIZE == 32
> +/* Currently Unused. */
> +# define KMOV kmovd
> +# define KORTEST kortestd
> +# define RAX eax
> +# define RCX ecx
> +# define RDX edx
> +# define SHR shrl
> +# define TEXTSUFFIX evex256
> +# define VMM0 ymm16
> +# define VMM1 ymm17
> +# define VMM2 ymm18
> +# define VMM3 ymm19
> +# define VMM4 ymm20
> +# define VMM5 ymm21
> +# define VMOVA vmovdqa32
> +# define VMOVU vmovdqu32
> +# endif
> +
> + .section .text.TEXTSUFFIX, "ax", @progbits
> +/* Aligning entry point to 64 byte, provides better performance for
> + one vector length string. */
> +ENTRY_P2ALIGN (STRCHR, 6)
> +
> + /* Broadcast CHAR to VMM0. */
> + VPBROADCAST %esi, %VMM0
> + movl %edi, %eax
> + andl $(PAGE_SIZE - 1), %eax
> + cmpl $(PAGE_SIZE - VEC_SIZE), %eax
> + ja L(page_cross)
> +
> + /* Compare [w]char for null, mask bit will be set for match. */
> + VMOVU (%rdi), %VMM1
> +
> + vpxorq %VMM1, %VMM0, %VMM2
> + VPMINU %VMM2, %VMM1, %VMM2
> + VPTESTN %VMM2, %VMM2, %k0
> +
> + KMOV %k0, %RAX
> +# ifndef USE_AS_STRCHRNUL
> + test %RAX, %RAX
> + jz L(align_more)
> + bsf %RAX, %RAX
> +# else
> + /* For strchnul, using bsf, if string is less than 64 byte,
> + entire logic will fit in 64 byte cache line and offset
> + the perf gap as compared to evex version. Even though
> + using bsf as condition can save code size but it is not
> + preferred for conditional jump for 2 reason. 1) It's
> + latency is 3. 2) Unlike test, it can't be micro-fused
> + with jump. */
> + bsf %RAX, %RAX
> + jz L(align_more)
> +# endif
> +
> +# ifdef USE_AS_WCSCHR
> + leaq (%rdi, %rax, CHAR_SIZE), %rax
> +# else
> + add %rdi, %rax
> +# endif
> +# ifndef USE_AS_STRCHRNUL
> + cmp (%rax), %CHAR_REG
> + jne L(zero)
> +# endif
> + ret
> +
> +# ifndef USE_AS_STRCHRNUL
> +L(zero):
> + xorl %eax, %eax
> + ret
> +# endif
> +
> +L(ret_vec_x2):
> + subq $-VEC_SIZE, %rax
> +L(ret_vec_x1):
> + bsf %RCX, %RCX
> +# ifdef USE_AS_WCSCHR
> + leaq (%rax, %rcx, CHAR_SIZE), %rax
> +# else
> + add %rcx, %rax
> +# endif
> +
> +# ifndef USE_AS_STRCHRNUL
> + cmp (%rax), %CHAR_REG
> + jne L(zero)
> +# endif
> + ret
> +
> +L(align_more):
> + leaq VEC_SIZE(%rdi), %rax
> + /* Align rax to VEC_SIZE. */
> + andq $-VEC_SIZE, %rax
> +
> + /* Loop unroll 4 times for 4 vector loop. */
> + VMOVA (%rax), %VMM1
> + vpxorq %VMM1, %VMM0, %VMM2
> + VPMINU %VMM2, %VMM1, %VMM2
> + VPTESTN %VMM2, %VMM2, %k0
> +
> + KMOV %k0, %RCX
> + test %RCX, %RCX
> + jnz L(ret_vec_x1)
> +
> + VMOVA VEC_SIZE(%rax), %VMM1
> + vpxorq %VMM1, %VMM0, %VMM2
> + VPMINU %VMM2, %VMM1, %VMM2
> + VPTESTN %VMM2, %VMM2, %k0
> +
> + KMOV %k0, %RCX
> + test %RCX, %RCX
> + jnz L(ret_vec_x2)
> +
> + VMOVA (VEC_SIZE * 2)(%rax), %VMM1
> + vpxorq %VMM1, %VMM0, %VMM2
> + VPMINU %VMM2, %VMM1, %VMM2
> + VPTESTN %VMM2, %VMM2, %k0
> + KMOV %k0, %RCX
> + test %RCX, %RCX
> + jnz L(ret_vec_x3)
> +
> + VMOVA (VEC_SIZE * 3)(%rax), %VMM1
> + vpxorq %VMM1, %VMM0, %VMM2
> + VPMINU %VMM2, %VMM1, %VMM2
> + VPTESTN %VMM2, %VMM2, %k0
> + KMOV %k0, %RCX
> + test %RCX, %RCX
> + jnz L(ret_vec_x4)
> +
> + /* Align address to VEC_SIZE * 4 for loop. */
> + andq $-(VEC_SIZE * 4), %rax
> +
> + .p2align 4,,11
> +L(loop):
> + /* VPMINU and VPCMP combination provide better performance as
> + compared to alternative combinations. */
> + VMOVA (VEC_SIZE * 4)(%rax), %VMM1
> + VMOVA (VEC_SIZE * 5)(%rax), %VMM2
> + VMOVA (VEC_SIZE * 6)(%rax), %VMM3
> + VMOVA (VEC_SIZE * 7)(%rax), %VMM4
> +
> + vpxorq %VMM1, %VMM0, %VMM5
> + VPMINU %VMM5, %VMM1, %VMM1
> +
> + VPCMP $4, %VMM0, %VMM2, %k1
> + VPMINU %VMM1, %VMM2, %VMM2{%k1}{z}
> +
> + VPCMP $4, %VMM0, %VMM3, %k2
> + VPMINU %VMM2, %VMM3, %VMM3{%k2}{z}
> +
> + VPCMP $4, %VMM0, %VMM4, %k3
> + VPMINU %VMM3, %VMM4, %VMM4{%k3}{z}
> +
> + VPTESTN %VMM4, %VMM4, %k3
> +
> + subq $-(VEC_SIZE * 4), %rax
> + KORTEST %k3, %k3
> + jz L(loop)
> +
> + VPTESTN %VMM1, %VMM1, %k0
> + KMOV %k0, %RCX
> + test %RCX, %RCX
> + jnz L(ret_vec_x1)
> +
> + VPTESTN %VMM2, %VMM2, %k0
> + KMOV %k0, %RCX
> + /* At this point, if k1 is non zero, null char must be in the
> + second vector. */
> + test %RCX, %RCX
> + jnz L(ret_vec_x2)
> +
> + VPTESTN %VMM3, %VMM3, %k0
> + KMOV %k0, %RCX
> + test %RCX, %RCX
> + jnz L(ret_vec_x3)
> + /* At this point null [w]char must be in the fourth vector so no
> + need to check. */
> + KMOV %k3, %RCX
> +
> +L(ret_vec_x4):
> + bsf %RCX, %RCX
> + leaq (VEC_SIZE * 3)(%rax, %rcx, CHAR_SIZE), %rax
> +# ifndef USE_AS_STRCHRNUL
> + cmp (%rax), %CHAR_REG
> + jne L(zero)
> +# endif
> + ret
> +
> +L(ret_vec_x3):
> + bsf %RCX, %RCX
> + leaq (VEC_SIZE * 2)(%rax, %rcx, CHAR_SIZE), %rax
> +# ifndef USE_AS_STRCHRNUL
> + cmp (%rax), %CHAR_REG
> + jne L(zero)
> +# endif
> + ret
> +
> +L(page_cross):
> + movl %eax, %ecx
> +# ifdef USE_AS_WCSCHR
> + /* Calculate number of compare result bits to be skipped for
> + wide string alignment adjustment. */
> + andl $(VEC_SIZE - 1), %ecx
> + sarl $2, %ecx
> +# endif
> + /* ecx contains number of w[char] to be skipped as a result
> + of address alignment. */
> + xorq %rdi, %rax
> + VMOVA (PAGE_SIZE - VEC_SIZE)(%rax), %VMM1
> + vpxorq %VMM1, %VMM0, %VMM2
> + VPMINU %VMM2, %VMM1, %VMM2
> + VPTESTN %VMM2, %VMM2, %k0
> + KMOV %k0, %RAX
> + /* Ignore number of character for alignment adjustment. */
> + SHR %cl, %RAX
> + jz L(align_more)
> +
> + bsf %RAX, %RAX
> +# ifdef USE_AS_WCSCHR
> + leaq (%rdi, %rax, CHAR_SIZE), %rax
> +# else
> + addq %rdi, %rax
> +# endif
> +
> +# ifndef USE_AS_STRCHRNUL
> + cmp (%rax), %CHAR_REG
> + jne L(zero)
> +# endif
> + ret
> +
> +END (STRCHR)
> +#endif
> diff --git a/sysdeps/x86_64/multiarch/strchr-evex512.S b/sysdeps/x86_64/multiarch/strchr-evex512.S
> new file mode 100644
> index 0000000000..4079bf387d
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/strchr-evex512.S
> @@ -0,0 +1,7 @@
> +# ifndef STRCHR
> +# define STRCHR __strchr_evex512
> +# endif
> +
> +#define VEC_SIZE 64
> +
> +#include "strchr-evex-base.S"
> diff --git a/sysdeps/x86_64/multiarch/strchrnul-evex512.S b/sysdeps/x86_64/multiarch/strchrnul-evex512.S
> new file mode 100644
> index 0000000000..1be0b12f38
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/strchrnul-evex512.S
> @@ -0,0 +1,8 @@
> +#ifndef STRCHRNUL
> +# define STRCHRNUL __strchrnul_evex512
> +#endif
> +
> +#define STRCHR STRCHRNUL
> +#define USE_AS_STRCHRNUL 1
> +
> +#include "strchr-evex512.S"
> diff --git a/sysdeps/x86_64/multiarch/wcschr-evex512.S b/sysdeps/x86_64/multiarch/wcschr-evex512.S
> new file mode 100644
> index 0000000000..50c87ab1e5
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/wcschr-evex512.S
> @@ -0,0 +1,8 @@
> +#ifndef WCSCHR
> +# define WCSCHR __wcschr_evex512
> +#endif
> +
> +#define STRCHR WCSCHR
> +#define USE_AS_WCSCHR 1
> +
> +#include "strchr-evex512.S"
> --
> 2.36.1
>
More information about the Libc-alpha
mailing list