From: Noah Goldstein <goldstein.w.n@gmail.com>
To: Sunil K Pandey <skpgkp2@gmail.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH v3] x86_64: Implement evex512 version of strchrnul, strchr and wcschr
Date: Tue, 25 Oct 2022 20:35:22 -0500 [thread overview]
Message-ID: <CAFUsyfK7-VKj00S=E4zoP+5pciFLGqTtz+nwFKUvBnBvqb_t8w@mail.gmail.com> (raw)
In-Reply-To: <20221025233504.843025-1-skpgkp2@gmail.com>
On Tue, Oct 25, 2022 at 6:35 PM Sunil K Pandey via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> Changes from v2:
> - Replace 2x load with mask logic.
> Changes from v1:
> - Use VEC API.
> - Replace extra lea in align_more with add.
> - Restructure loop logic.
> - Create zero_2 to avoid long jmp.
> - Combine first, second and third vector return logic.
>
> 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.
>
> - strchrnul function using 512 bit vectors.
> - strchr function using 512 bit vectors.
> - wcschr function using 512 bit vectors.
>
> Code size data:
>
> strchrnul-evex.o 599 byte
> strchrnul-evex512.o 569 byte (-5%)
>
> strchr-evex.o 639 byte
> strchr-evex512.o 595 byte (-7%)
>
> wcschr-evex.o 644 byte
> wcschr-evex512.o 607 byte (-6%)
>
> 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 | 282 +++++++++++++++++++
> sysdeps/x86_64/multiarch/strchr-evex512.S | 8 +
> sysdeps/x86_64/multiarch/strchrnul-evex512.S | 8 +
> sysdeps/x86_64/multiarch/wcschr-evex512.S | 9 +
> 6 files changed, 322 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 e974b1ad97..597ac9d5e9 100644
> --- a/sysdeps/x86_64/multiarch/Makefile
> +++ b/sysdeps/x86_64/multiarch/Makefile
> @@ -62,11 +62,13 @@ 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 \
> @@ -131,6 +133,7 @@ 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 529c0b0ef0..c3d75a09f4 100644
> --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> @@ -544,6 +544,10 @@ __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)),
> @@ -569,6 +573,10 @@ __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)),
> @@ -793,6 +801,10 @@ __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..21a6bc5907
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/strchr-evex-base.S
> @@ -0,0 +1,282 @@
> +/* 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 VPCMPNE vpcmpneqd
> +# define VPMINU vpminud
> +# define VPTEST vptestmd
> +# define VPTESTN vptestnmd
> +# else
> +# define CHAR_REG sil
> +# define CHAR_SIZE 1
> +# define VPBROADCAST vpbroadcastb
> +# define VPCMP vpcmpb
> +# define VPCMPNE vpcmpneqb
> +# define VPMINU vpminub
> +# define VPTEST vptestmb
> +# define VPTESTN vptestnmb
> +# endif
> +
> +# define PAGE_SIZE 4096
> +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
> +# define VEC_MATCH_MASK ((1 << CHAR_PER_VEC) - 1)
> +
> + .section SECTION(.text), "ax", @progbits
> +/* Aligning entry point to 64 byte, provides better performance for
> + one vector length string. */
> +ENTRY_P2ALIGN (STRCHR, 6)
> +
> + /* Broadcast CHAR to VMM(0). */
> + VPBROADCAST %esi, %VMM(0)
> + movl %edi, %eax
> + sall $20,%eax
> + cmpl $((PAGE_SIZE - VEC_SIZE) << 20), %eax
> + ja L(page_cross)
> +
> + VMOVU (%rdi), %VMM(1)
> + VPCMPNE %VMM(1), %VMM(0), %k1
> + VPTEST %VMM(1), %VMM(1), %k0{%k1}
> + KMOV %k0, %VRAX
> + /* Compare [w]char for null, mask bit will be set for match. */
> +
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRAX
> +# else
> + inc %VRAX
> +# endif
> + jz L(align_more)
> +
> + bsf %VRAX, %VRAX
> +
> +# 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)
> + ret
> +L(zero):
> + xorl %eax, %eax
> +# endif
> + ret
> +
> +L(ret_vec_x3):
> + subq $-VEC_SIZE, %rdi
> +L(ret_vec_x2):
> + subq $-VEC_SIZE, %rdi
> +L(ret_vec_x1):
> + bsf %VRAX, %VRAX
> +# 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
> +
> +L(page_cross):
> + mov %rdi, %rax
> + movl %edi, %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. */
> + andq $-VEC_SIZE, %rax
> +
> + VMOVA (%rax), %VMM(1)
> + VPCMPNE %VMM(1), %VMM(0), %k1
> + VPTEST %VMM(1), %VMM(1), %k0{%k1}
> + KMOV %k0, %VRAX
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRAX
> +# else
> + inc %VRAX
> +# endif
> + /* Ignore number of character for alignment adjustment. */
> + shr %cl, %VRAX
> + jz L(align_more)
> +
> + bsf %VRAX, %VRAX
> +# 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
> +
> +L(align_more):
> + /* Align rax to VEC_SIZE. */
> + andq $-VEC_SIZE, %rdi
> +
> + /* Loop unroll 4 times for 4 vector loop. */
> + VMOVA VEC_SIZE(%rdi), %VMM(1)
> + VPCMPNE %VMM(1), %VMM(0), %k1
> + VPTEST %VMM(1), %VMM(1), %k0{%k1}
> +
> + /* Increment rdi by vector size for further comparison and
> + return. */
> + subq $-VEC_SIZE, %rdi
> + KMOV %k0, %VRAX
> +
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRAX
> +# else
> + inc %VRAX
> +# endif
> + jnz L(ret_vec_x1)
> +
> + VMOVA VEC_SIZE(%rdi), %VMM(1)
> + VPCMPNE %VMM(1), %VMM(0), %k1
> + VPTEST %VMM(1), %VMM(1), %k0{%k1}
> + KMOV %k0, %VRAX
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRAX
> +# else
> + inc %VRAX
> +# endif
> + jnz L(ret_vec_x2)
> +
> + VMOVA (VEC_SIZE * 2)(%rdi), %VMM(1)
> + VPCMPNE %VMM(1), %VMM(0), %k1
> + VPTEST %VMM(1), %VMM(1), %k0{%k1}
> + KMOV %k0, %VRAX
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRAX
> +# else
> + inc %VRAX
> +# endif
> + jnz L(ret_vec_x3)
> +
> + VMOVA (VEC_SIZE * 3)(%rdi), %VMM(1)
> + VPCMPNE %VMM(1), %VMM(0), %k1
> + VPTEST %VMM(1), %VMM(1), %k0{%k1}
> + KMOV %k0, %VRDX
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRDX
> +# else
> + inc %VRDX
> +# endif
> + jnz L(ret_vec_x4)
> +
> +
> + /* Align address to VEC_SIZE * 4 for loop. */
> + andq $-(VEC_SIZE * 4), %rdi
> +L(loop):
> + /* VPMINU and VPCMP combination provide better performance as
> + compared to alternative combinations. */
> + VMOVA (VEC_SIZE * 4)(%rdi), %VMM(1)
> + VMOVA (VEC_SIZE * 5)(%rdi), %VMM(2)
> + VMOVA (VEC_SIZE * 6)(%rdi), %VMM(3)
> + VMOVA (VEC_SIZE * 7)(%rdi), %VMM(4)
> +
> + VPCMPNE %VMM(1), %VMM(0), %k1
> + VPCMPNE %VMM(2), %VMM(0), %k2
> +
> + VPMINU %VMM(2), %VMM(1), %VMM(2)
> +
> + VPCMPNE %VMM(3), %VMM(0), %k3{%k1}
> + VPCMPNE %VMM(4), %VMM(0), %k4{%k2}
> +
> + VPMINU %VMM(4), %VMM(3), %VMM(4)
> + VPMINU %VMM(2), %VMM(4), %VMM(4){%k3}{z}
> +
> + VPTEST %VMM(4), %VMM(4), %k5{%k4}
> +
> + KMOV %k5, %VRDX
> + subq $-(VEC_SIZE * 4), %rdi
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRDX
> +# else
> + inc %VRDX
> +# endif
> + jz L(loop)
> +
> + VPTEST %VMM(1), %VMM(1), %k0{%k1}
> + KMOV %k0, %VRAX
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRAX
> +# else
> + inc %VRAX
> +# endif
> + jnz L(ret_vec_x1)
> +
> + VPTEST %VMM(2), %VMM(2), %k0{%k2}
> + KMOV %k0, %VRAX
> + /* At this point, if k1 is non zero, null char must be in the
> + second vector. */
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRAX
> +# else
> + inc %VRAX
> +# endif
> + jnz L(ret_vec_x2)
> +
> + VPTEST %VMM(3), %VMM(3), %k0{%k3}
> + KMOV %k0, %VRAX
> +# ifdef USE_AS_WCSCHR
> + sub $VEC_MATCH_MASK, %VRAX
> +# else
> + inc %VRAX
> +# endif
> + jnz L(ret_vec_x3)
> + /* At this point null [w]char must be in the fourth vector so no
> + need to check. */
> +
> +L(ret_vec_x4):
> + bsf %VRDX, %VRAX
> + leaq (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
Can you make this:
```
bsf %VRDX, %VRDX
leaq (VEC_SIZE * 3)(%rdi, %rdx, CHAR_SIZE), %rax
```
bsf has a false dependency on the destination register.
> +# ifndef USE_AS_STRCHRNUL
> + cmp (%rax), %CHAR_REG
> + jne L(zero_2)
> +# endif
> + ret
> +
> +# ifndef USE_AS_STRCHRNUL
> +L(zero_2):
> + xor %eax, %eax
> + ret
> +# endif
> +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..a4ac022952
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/strchr-evex512.S
> @@ -0,0 +1,8 @@
> +# ifndef STRCHR
> +# define STRCHR __strchr_evex512
> +# endif
> +
> +#include "x86-evex512-vecs.h"
> +#include "reg-macros.h"
> +
> +#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..3fe4e77a70
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/wcschr-evex512.S
> @@ -0,0 +1,9 @@
> +#ifndef WCSCHR
> +# define WCSCHR __wcschr_evex512
> +#endif
> +
> +#define STRCHR WCSCHR
> +#define USE_AS_WCSCHR 1
> +
> +#define USE_WIDE_CHAR 1
> +#include "strchr-evex512.S"
> --
> 2.36.1
>
next prev parent reply other threads:[~2022-10-26 1:35 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-22 0:16 [PATCH] " Sunil K Pandey
2022-09-22 0:50 ` Noah Goldstein
2022-09-23 3:57 ` Sunil Pandey
2022-09-29 3:41 ` Sunil Pandey
2022-09-29 4:07 ` Noah Goldstein
2022-10-21 21:23 ` [PATCH v2] " Sunil K Pandey
2022-10-25 23:35 ` [PATCH v3] " Sunil K Pandey
2022-10-26 1:35 ` Noah Goldstein [this message]
2022-10-26 2:06 ` [PATCH v4] " Sunil K Pandey
2022-10-26 4:11 ` Noah Goldstein
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