From: "H.J. Lu" <hjl.tools@gmail.com>
To: Noah Goldstein <goldstein.w.n@gmail.com>
Cc: GNU C Library <libc-alpha@sourceware.org>,
"Carlos O'Donell" <carlos@systemhalted.org>
Subject: Re: [PATCH v2 4/4] x86: Optimize {str|wcs}rchr-evex
Date: Thu, 21 Apr 2022 16:59:46 -0700 [thread overview]
Message-ID: <CAMe9rOoAT0M5DhPVfbCxhih9Jp=o6QODJ=kovaCeyTea_MjGPQ@mail.gmail.com> (raw)
In-Reply-To: <20220421222204.3093130-4-goldstein.w.n@gmail.com>
On Thu, Apr 21, 2022 at 3:22 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> The new code unrolls the main loop slightly without adding too much
> overhead and minimizes the comparisons for the search CHAR.
>
> Geometric Mean of all benchmarks New / Old: 0.755
> See email for all results.
>
> Full xcheck passes on x86_64 with and without multiarch enabled.
> ---
> sysdeps/x86_64/multiarch/strrchr-evex.S | 441 ++++++++++++++----------
> 1 file changed, 259 insertions(+), 182 deletions(-)
>
> diff --git a/sysdeps/x86_64/multiarch/strrchr-evex.S b/sysdeps/x86_64/multiarch/strrchr-evex.S
> index adeddaed32..5cf9a8315b 100644
> --- a/sysdeps/x86_64/multiarch/strrchr-evex.S
> +++ b/sysdeps/x86_64/multiarch/strrchr-evex.S
> @@ -24,242 +24,319 @@
> # define STRRCHR __strrchr_evex
> # endif
>
> -# define VMOVU vmovdqu64
> -# define VMOVA vmovdqa64
> +# define VMOVU vmovdqu64
> +# define VMOVA vmovdqa64
>
> # ifdef USE_AS_WCSRCHR
> +# define SHIFT_REG esi
> +
> +# define kunpck kunpckbw
> +# define kmov_2x kmovd
> +# define maskz_2x ecx
> +# define maskm_2x eax
> +# define CHAR_SIZE 4
> +# define VPMIN vpminud
> +# define VPTESTN vptestnmd
> # define VPBROADCAST vpbroadcastd
> -# define VPCMP vpcmpd
> -# define SHIFT_REG r8d
> +# define VPCMP vpcmpd
> # else
> +# define SHIFT_REG edi
> +
> +# define kunpck kunpckdq
> +# define kmov_2x kmovq
> +# define maskz_2x rcx
> +# define maskm_2x rax
> +
> +# define CHAR_SIZE 1
> +# define VPMIN vpminub
> +# define VPTESTN vptestnmb
> # define VPBROADCAST vpbroadcastb
> -# define VPCMP vpcmpb
> -# define SHIFT_REG ecx
> +# define VPCMP vpcmpb
> # endif
>
> # define XMMZERO xmm16
> # define YMMZERO ymm16
> # define YMMMATCH ymm17
> -# define YMM1 ymm18
> +# define YMMSAVE ymm18
> +
> +# define YMM1 ymm19
> +# define YMM2 ymm20
> +# define YMM3 ymm21
> +# define YMM4 ymm22
> +# define YMM5 ymm23
> +# define YMM6 ymm24
> +# define YMM7 ymm25
> +# define YMM8 ymm26
>
> -# define VEC_SIZE 32
>
> - .section .text.evex,"ax",@progbits
> -ENTRY (STRRCHR)
> - movl %edi, %ecx
> +# define VEC_SIZE 32
> +# define PAGE_SIZE 4096
> + .section .text.evex, "ax", @progbits
> +ENTRY(STRRCHR)
> + movl %edi, %eax
> /* Broadcast CHAR to YMMMATCH. */
> VPBROADCAST %esi, %YMMMATCH
>
> - vpxorq %XMMZERO, %XMMZERO, %XMMZERO
> -
> - /* Check if we may cross page boundary with one vector load. */
> - andl $(2 * VEC_SIZE - 1), %ecx
> - cmpl $VEC_SIZE, %ecx
> - ja L(cros_page_boundary)
> + andl $(PAGE_SIZE - 1), %eax
> + cmpl $(PAGE_SIZE - VEC_SIZE), %eax
> + jg L(cross_page_boundary)
>
> +L(page_cross_continue):
> VMOVU (%rdi), %YMM1
> -
> - /* Each bit in K0 represents a null byte in YMM1. */
> - VPCMP $0, %YMMZERO, %YMM1, %k0
> - /* Each bit in K1 represents a CHAR in YMM1. */
> - VPCMP $0, %YMMMATCH, %YMM1, %k1
> + VPTESTN %YMM1, %YMM1, %k0
Please add some comments for mask register on VPTESTN tests.
> kmovd %k0, %ecx
> - kmovd %k1, %eax
> -
> - addq $VEC_SIZE, %rdi
> -
> - testl %eax, %eax
> - jnz L(first_vec)
> -
> testl %ecx, %ecx
> - jnz L(return_null)
> -
> - andq $-VEC_SIZE, %rdi
> - xorl %edx, %edx
> - jmp L(aligned_loop)
> -
> - .p2align 4
> -L(first_vec):
> - /* Check if there is a null byte. */
> - testl %ecx, %ecx
> - jnz L(char_and_nul_in_first_vec)
> -
> - /* Remember the match and keep searching. */
> - movl %eax, %edx
> - movq %rdi, %rsi
> - andq $-VEC_SIZE, %rdi
> - jmp L(aligned_loop)
> -
> - .p2align 4
> -L(cros_page_boundary):
> - andl $(VEC_SIZE - 1), %ecx
> - andq $-VEC_SIZE, %rdi
> -
> + jz L(aligned_more)
> + VPCMP $0, %YMMMATCH, %YMM1, %k1
Please add some comments.
> + kmovd %k1, %eax
> + blsmskl %ecx, %ecx
> + andl %ecx, %eax
> + jz L(ret0)
> + bsrl %eax, %eax
> # ifdef USE_AS_WCSRCHR
> - /* NB: Divide shift count by 4 since each bit in K1 represent 4
> - bytes. */
> - movl %ecx, %SHIFT_REG
> - sarl $2, %SHIFT_REG
> + leaq (%rdi, %rax, CHAR_SIZE), %rax
> +# else
> + addq %rdi, %rax
> # endif
> +L(ret0):
> + ret
>
> - VMOVA (%rdi), %YMM1
> -
> - /* Each bit in K0 represents a null byte in YMM1. */
> - VPCMP $0, %YMMZERO, %YMM1, %k0
> - /* Each bit in K1 represents a CHAR in YMM1. */
> + /* Returns for first vec x1/x2/x3 have hard coded backward
> + search path for earlier matches. */
> + .p2align 4,, 6
> +L(first_vec_x1):
> + VPCMP $0, %YMMMATCH, %YMM2, %k1
> + kmovd %k1, %eax
> + blsmskl %ecx, %ecx
> + andl %ecx, %eax
> + jnz L(first_vec_x1_return)
> + .p2align 4,, 4
> +L(first_vec_x0_test):
> VPCMP $0, %YMMMATCH, %YMM1, %k1
> - kmovd %k0, %edx
> kmovd %k1, %eax
> -
> - shrxl %SHIFT_REG, %edx, %edx
> - shrxl %SHIFT_REG, %eax, %eax
> - addq $VEC_SIZE, %rdi
> -
> - /* Check if there is a CHAR. */
> testl %eax, %eax
> - jnz L(found_char)
> -
> - testl %edx, %edx
> - jnz L(return_null)
> -
> - jmp L(aligned_loop)
> -
> - .p2align 4
> -L(found_char):
> - testl %edx, %edx
> - jnz L(char_and_nul)
> -
> - /* Remember the match and keep searching. */
> - movl %eax, %edx
> - leaq (%rdi, %rcx), %rsi
> + jz L(ret1)
> + bsrl %eax, %eax
> +# ifdef USE_AS_WCSRCHR
> + leaq (%rsi, %rax, CHAR_SIZE), %rax
> +# else
> + addq %rsi, %rax
> +# endif
> +L(ret1):
> + ret
>
> - .p2align 4
> -L(aligned_loop):
> - VMOVA (%rdi), %YMM1
> - addq $VEC_SIZE, %rdi
> + .p2align 4,, 10
> +L(first_vec_x1_or_x2):
> + VPCMP $0, %YMM3, %YMMMATCH, %k3
> + VPCMP $0, %YMM2, %YMMMATCH, %k2
> + kortestd %k2, %k3
> + jz L(first_vec_x0_test)
> +
> + kunpck %k2, %k3, %k3
> + kmovq %k3, %rax
> + bsrq %rax, %rax
> + leaq (VEC_SIZE)(%r8, %rax, CHAR_SIZE), %rax
> + ret
>
> - /* Each bit in K0 represents a null byte in YMM1. */
> - VPCMP $0, %YMMZERO, %YMM1, %k0
> - /* Each bit in K1 represents a CHAR in YMM1. */
> - VPCMP $0, %YMMMATCH, %YMM1, %k1
> - kmovd %k0, %ecx
> + .p2align 4,, 6
> +L(first_vec_x3):
> + VPCMP $0, %YMMMATCH, %YMM4, %k1
> kmovd %k1, %eax
> - orl %eax, %ecx
> - jnz L(char_nor_null)
> + blsmskl %ecx, %ecx
> + andl %ecx, %eax
> + jz L(first_vec_x1_or_x2)
> + bsrl %eax, %eax
> + leaq (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
> + ret
>
> - VMOVA (%rdi), %YMM1
> - add $VEC_SIZE, %rdi
> + .p2align 4,, 6
> +L(first_vec_x0_x1_test):
> + VPCMP $0, %YMMMATCH, %YMM2, %k1
> + kmovd %k1, %eax
> + testl %eax, %eax
> + jz L(first_vec_x0_test)
> + .p2align 4,, 4
> +L(first_vec_x1_return):
> + bsrl %eax, %eax
> + leaq (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %rax
> + ret
>
> - /* Each bit in K0 represents a null byte in YMM1. */
> - VPCMP $0, %YMMZERO, %YMM1, %k0
> - /* Each bit in K1 represents a CHAR in YMM1. */
> - VPCMP $0, %YMMMATCH, %YMM1, %k1
> - kmovd %k0, %ecx
> + .p2align 4,, 10
> +L(first_vec_x2):
> + VPCMP $0, %YMMMATCH, %YMM3, %k1
> kmovd %k1, %eax
> - orl %eax, %ecx
> - jnz L(char_nor_null)
> + blsmskl %ecx, %ecx
> + andl %ecx, %eax
> + jz L(first_vec_x0_x1_test)
> + bsrl %eax, %eax
> + leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> + ret
>
> - VMOVA (%rdi), %YMM1
> - addq $VEC_SIZE, %rdi
>
> - /* Each bit in K0 represents a null byte in YMM1. */
> - VPCMP $0, %YMMZERO, %YMM1, %k0
> - /* Each bit in K1 represents a CHAR in YMM1. */
> - VPCMP $0, %YMMMATCH, %YMM1, %k1
> + .p2align 4
> +L(aligned_more):
> + /* Need to keep original pointer incase YMM1 has last match. */
> + movq %rdi, %rsi
> + andq $-VEC_SIZE, %rdi
> + VMOVU VEC_SIZE(%rdi), %YMM2
> + VPTESTN %YMM2, %YMM2, %k0
> kmovd %k0, %ecx
> - kmovd %k1, %eax
> - orl %eax, %ecx
> - jnz L(char_nor_null)
> + testl %ecx, %ecx
> + jnz L(first_vec_x1)
>
> - VMOVA (%rdi), %YMM1
> - addq $VEC_SIZE, %rdi
> + VMOVU (VEC_SIZE * 2)(%rdi), %YMM3
> + VPTESTN %YMM3, %YMM3, %k0
> + kmovd %k0, %ecx
> + testl %ecx, %ecx
> + jnz L(first_vec_x2)
>
> - /* Each bit in K0 represents a null byte in YMM1. */
> - VPCMP $0, %YMMZERO, %YMM1, %k0
> - /* Each bit in K1 represents a CHAR in YMM1. */
> - VPCMP $0, %YMMMATCH, %YMM1, %k1
> + VMOVU (VEC_SIZE * 3)(%rdi), %YMM4
> + VPTESTN %YMM4, %YMM4, %k0
> kmovd %k0, %ecx
> - kmovd %k1, %eax
> - orl %eax, %ecx
> - jz L(aligned_loop)
> + movq %rdi, %r8
> + testl %ecx, %ecx
> + jnz L(first_vec_x3)
>
> + andq $-(VEC_SIZE * 2), %rdi
> .p2align 4
> -L(char_nor_null):
> - /* Find a CHAR or a null byte in a loop. */
> +L(first_aligned_loop):
> + /* Preserve YMM1, YMM2, YMM3, and YMM4 until we can gurantee
> + they don't store a match. */
> + VMOVA (VEC_SIZE * 4)(%rdi), %YMM5
> + VMOVA (VEC_SIZE * 5)(%rdi), %YMM6
> +
> + VPCMP $0, %YMM5, %YMMMATCH, %k2
> + vpxord %YMM6, %YMMMATCH, %YMM7
> +
> + VPMIN %YMM5, %YMM6, %YMM8
> + VPMIN %YMM8, %YMM7, %YMM7
> +
> + VPTESTN %YMM7, %YMM7, %k1
> + subq $(VEC_SIZE * -2), %rdi
> + kortestd %k1, %k2
> + jz L(first_aligned_loop)
> +
> + VPCMP $0, %YMM6, %YMMMATCH, %k3
> + VPTESTN %YMM8, %YMM8, %k1
> + ktestd %k1, %k1
> + jz L(second_aligned_loop_prep)
> +
> + kortestd %k2, %k3
> + jnz L(return_first_aligned_loop)
> +
> + .p2align 4,, 6
> +L(first_vec_x1_or_x2_or_x3):
> + VPCMP $0, %YMM4, %YMMMATCH, %k4
> + kmovd %k4, %eax
> testl %eax, %eax
> - jnz L(match)
> -L(return_value):
> - testl %edx, %edx
> - jz L(return_null)
> - movl %edx, %eax
> - movq %rsi, %rdi
> + jz L(first_vec_x1_or_x2)
> bsrl %eax, %eax
> -# ifdef USE_AS_WCSRCHR
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - leaq -VEC_SIZE(%rdi, %rax, 4), %rax
> -# else
> - leaq -VEC_SIZE(%rdi, %rax), %rax
> -# endif
> + leaq (VEC_SIZE * 3)(%r8, %rax, CHAR_SIZE), %rax
> ret
>
> - .p2align 4
> -L(match):
> - /* Find a CHAR. Check if there is a null byte. */
> - kmovd %k0, %ecx
> - testl %ecx, %ecx
> - jnz L(find_nul)
> + .p2align 4,, 8
> +L(return_first_aligned_loop):
> + VPTESTN %YMM5, %YMM5, %k0
> + kunpck %k0, %k1, %k0
> + kmov_2x %k0, %maskz_2x
> +
> + blsmsk %maskz_2x, %maskz_2x
> + kunpck %k2, %k3, %k3
> + kmov_2x %k3, %maskm_2x
> + and %maskz_2x, %maskm_2x
> + jz L(first_vec_x1_or_x2_or_x3)
> +
> + bsr %maskm_2x, %maskm_2x
> + leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> + ret
>
> - /* Remember the match and keep searching. */
> - movl %eax, %edx
> + .p2align 4
> + /* We can throw away the work done for the first 4x checks here
> + as we have a later match. This is the 'fast' path persay.
> + */
> +L(second_aligned_loop_prep):
> +L(second_aligned_loop_set_furthest_match):
> movq %rdi, %rsi
> - jmp L(aligned_loop)
> + kunpck %k2, %k3, %k4
>
> .p2align 4
> -L(find_nul):
> - /* Mask out any matching bits after the null byte. */
> - movl %ecx, %r8d
> - subl $1, %r8d
> - xorl %ecx, %r8d
> - andl %r8d, %eax
> - testl %eax, %eax
> - /* If there is no CHAR here, return the remembered one. */
> - jz L(return_value)
> - bsrl %eax, %eax
> +L(second_aligned_loop):
> + VMOVU (VEC_SIZE * 4)(%rdi), %YMM1
> + VMOVU (VEC_SIZE * 5)(%rdi), %YMM2
> +
> + VPCMP $0, %YMM1, %YMMMATCH, %k2
> + vpxord %YMM2, %YMMMATCH, %YMM3
> +
> + VPMIN %YMM1, %YMM2, %YMM4
> + VPMIN %YMM3, %YMM4, %YMM3
> +
> + VPTESTN %YMM3, %YMM3, %k1
> + subq $(VEC_SIZE * -2), %rdi
> + kortestd %k1, %k2
> + jz L(second_aligned_loop)
> +
> + VPCMP $0, %YMM2, %YMMMATCH, %k3
> + VPTESTN %YMM4, %YMM4, %k1
> + ktestd %k1, %k1
> + jz L(second_aligned_loop_set_furthest_match)
> +
> + kortestd %k2, %k3
> + /* branch here because there is a significant advantage interms
> + of output dependency chance in using edx. */
> + jnz L(return_new_match)
> +L(return_old_match):
> + kmovq %k4, %rax
> + bsrq %rax, %rax
> + leaq (VEC_SIZE * 2)(%rsi, %rax, CHAR_SIZE), %rax
> + ret
> +
> +L(return_new_match):
> + VPTESTN %YMM1, %YMM1, %k0
> + kunpck %k0, %k1, %k0
> + kmov_2x %k0, %maskz_2x
> +
> + blsmsk %maskz_2x, %maskz_2x
> + kunpck %k2, %k3, %k3
> + kmov_2x %k3, %maskm_2x
> + and %maskz_2x, %maskm_2x
> + jz L(return_old_match)
> +
> + bsr %maskm_2x, %maskm_2x
> + leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
> + ret
> +
> + /* This block is horribly aligned (% 16 == 15). This is
> + intentional. The L(cross_page_boundary) block is exactly
> + 32-bytes of code size. Ultimately this is a cold case so
> + save the code size by leaving misaligned. */
> +L(cross_page_boundary):
> + xorq %rdi, %rax
> + VMOVU (PAGE_SIZE - VEC_SIZE)(%rax), %YMM1
> + VPTESTN %YMM1, %YMM1, %k0
> + kmovd %k0, %ecx
> # ifdef USE_AS_WCSRCHR
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - leaq -VEC_SIZE(%rdi, %rax, 4), %rax
> -# else
> - leaq -VEC_SIZE(%rdi, %rax), %rax
> + movl %edi, %esi
> + andl $(VEC_SIZE - 1), %esi
> + shrl $2, %esi
> # endif
> - ret
> + shrxl %SHIFT_REG, %ecx, %ecx
>
> - .p2align 4
> -L(char_and_nul):
> - /* Find both a CHAR and a null byte. */
> - addq %rcx, %rdi
> - movl %edx, %ecx
> -L(char_and_nul_in_first_vec):
> - /* Mask out any matching bits after the null byte. */
> - movl %ecx, %r8d
> - subl $1, %r8d
> - xorl %ecx, %r8d
> - andl %r8d, %eax
> - testl %eax, %eax
> - /* Return null pointer if the null byte comes first. */
> - jz L(return_null)
> + testl %ecx, %ecx
> + jz L(page_cross_continue)
> + VPCMP $0, %YMMMATCH, %YMM1, %k1
> + kmovd %k1, %eax
> + shrxl %SHIFT_REG, %eax, %eax
> + blsmskl %ecx, %ecx
> + andl %ecx, %eax
> + jz L(ret3)
> bsrl %eax, %eax
> # ifdef USE_AS_WCSRCHR
> - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
> - leaq -VEC_SIZE(%rdi, %rax, 4), %rax
> + leaq (%rdi, %rax, CHAR_SIZE), %rax
> # else
> - leaq -VEC_SIZE(%rdi, %rax), %rax
> + addq %rdi, %rax
> # endif
> +L(ret3):
> ret
>
> - .p2align 4
> -L(return_null):
> - xorl %eax, %eax
> - ret
> -
> -END (STRRCHR)
> +END(STRRCHR)
> #endif
> --
> 2.25.1
>
--
H.J.
next prev parent reply other threads:[~2022-04-22 0:00 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-21 3:14 [PATCH v1 1/5] benchtests: Improve bench-strrchr Noah Goldstein
2022-04-21 3:14 ` [PATCH v1 2/5] x86: Optimize {str|wcs}rchr-sse2 Noah Goldstein
2022-04-21 20:26 ` H.J. Lu
2022-04-21 20:57 ` Noah Goldstein
2022-04-21 21:48 ` H.J. Lu
2022-04-21 22:23 ` Noah Goldstein
2022-04-21 3:14 ` [PATCH v1 3/5] x86: Add wcsrchr optimized with SSE4_1 in wcsrchr-sse4_1.S Noah Goldstein
2022-04-21 3:14 ` [PATCH v1 4/5] x86: Optimize {str|wcs}rchr-avx2 Noah Goldstein
2022-04-21 3:14 ` [PATCH v1 5/5] x86: Optimize {str|wcs}rchr-evex Noah Goldstein
2022-04-21 20:12 ` [PATCH v1 1/5] benchtests: Improve bench-strrchr H.J. Lu
2022-04-21 22:07 ` Noah Goldstein
2022-04-21 23:49 ` H.J. Lu
2022-04-22 1:11 ` Noah Goldstein
2022-04-21 22:22 ` [PATCH v2 1/4] " Noah Goldstein
2022-04-21 22:22 ` [PATCH v2 2/4] x86: Optimize {str|wcs}rchr-sse2 Noah Goldstein
2022-04-21 23:46 ` H.J. Lu
2022-04-22 1:54 ` Noah Goldstein
2022-04-21 22:22 ` [PATCH v2 3/4] x86: Optimize {str|wcs}rchr-avx2 Noah Goldstein
2022-04-21 22:22 ` [PATCH v2 4/4] x86: Optimize {str|wcs}rchr-evex Noah Goldstein
2022-04-21 23:59 ` H.J. Lu [this message]
2022-04-22 1:53 ` Noah Goldstein
2022-04-22 1:52 ` [PATCH v3 1/4] benchtests: Improve bench-strrchr Noah Goldstein
2022-04-22 1:52 ` [PATCH v3 2/4] x86: Optimize {str|wcs}rchr-sse2 Noah Goldstein
2022-04-22 19:06 ` H.J. Lu
2022-05-12 20:13 ` Sunil Pandey
2022-04-22 1:52 ` [PATCH v3 3/4] x86: Optimize {str|wcs}rchr-avx2 Noah Goldstein
2022-04-22 19:03 ` H.J. Lu
2022-05-12 20:14 ` Sunil Pandey
2022-07-20 15:33 ` Noah Goldstein
2022-04-22 1:52 ` [PATCH v3 4/4] x86: Optimize {str|wcs}rchr-evex Noah Goldstein
2022-04-22 19:04 ` H.J. Lu
2022-05-12 20:16 ` Sunil Pandey
2022-04-22 18:29 ` [PATCH v3 1/4] benchtests: Improve bench-strrchr H.J. Lu
2022-04-22 19:12 ` Noah Goldstein
2022-04-22 19:11 ` [PATCH v4 " Noah Goldstein
2022-04-23 1:53 ` H.J. Lu
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