From 7f3e7c262cab4e2401e4331a6ef29c428de02044 Mon Sep 17 00:00:00 2001 From: Noah Goldstein Date: Fri, 23 Apr 2021 15:56:25 -0400 Subject: [PATCH] x86: Optimize strchr-evex.S No bug. This commit optimizes strchr-evex.S. The optimizations are mostly small things such as save an ALU in the alignment process, saving a few instructions in the loop return. The one significant change is saving 2 instructions in the 4x loop. test-strchr, test-strchrnul, test-wcschr, and test-wcschrnul are all passing. Signed-off-by: Noah Goldstein --- sysdeps/x86_64/multiarch/strchr-evex.S | 392 ++++++++++++++----------- 1 file changed, 218 insertions(+), 174 deletions(-) diff --git a/sysdeps/x86_64/multiarch/strchr-evex.S b/sysdeps/x86_64/multiarch/strchr-evex.S index ddc86a7058..7f9d4ee48d 100644 --- a/sysdeps/x86_64/multiarch/strchr-evex.S +++ b/sysdeps/x86_64/multiarch/strchr-evex.S @@ -32,13 +32,15 @@ # define VPCMP vpcmpd # define VPMINU vpminud # define CHAR_REG esi -# define SHIFT_REG r8d +# define SHIFT_REG ecx +# define CHAR_SIZE 4 # else # define VPBROADCAST vpbroadcastb # define VPCMP vpcmpb # define VPMINU vpminub # define CHAR_REG sil -# define SHIFT_REG ecx +# define SHIFT_REG edx +# define CHAR_SIZE 1 # endif # define XMMZERO xmm16 @@ -56,23 +58,20 @@ # define VEC_SIZE 32 # define PAGE_SIZE 4096 +# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE) .section .text.evex,"ax",@progbits ENTRY (STRCHR) - movl %edi, %ecx -# ifndef USE_AS_STRCHRNUL - xorl %edx, %edx -# endif - /* Broadcast CHAR to YMM0. */ - VPBROADCAST %esi, %YMM0 - + VPBROADCAST %esi, %YMM0 + movl %edi, %eax + andl $(PAGE_SIZE - 1), %eax vpxorq %XMMZERO, %XMMZERO, %XMMZERO - /* Check if we cross page boundary with one vector load. */ - andl $(PAGE_SIZE - 1), %ecx - cmpl $(PAGE_SIZE - VEC_SIZE), %ecx - ja L(cross_page_boundary) + /* Check if we cross page boundary with one vector load. + Otherwise it is safe to use an unaligned load. */ + cmpl $(PAGE_SIZE - VEC_SIZE), %eax + ja L(cross_page_boundary) /* Check the first VEC_SIZE bytes. Search for both CHAR and the null bytes. */ @@ -83,251 +82,296 @@ ENTRY (STRCHR) VPMINU %YMM2, %YMM1, %YMM2 /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ VPCMP $0, %YMMZERO, %YMM2, %k0 - ktestd %k0, %k0 - jz L(more_vecs) kmovd %k0, %eax + testl %eax, %eax + jz L(aligned_more) tzcntl %eax, %eax - /* Found CHAR or the null byte. */ # ifdef USE_AS_WCSCHR - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ - leaq (%rdi, %rax, 4), %rax + /* NB: Multiply wchar_t count by 4 to get the number of bytes. + */ + leaq (%rdi, %rax, CHAR_SIZE), %rax # else addq %rdi, %rax # endif # ifndef USE_AS_STRCHRNUL - cmp (%rax), %CHAR_REG - cmovne %rdx, %rax + /* Found CHAR or the null byte. */ + cmp (%rax), %CHAR_REG + jne L(zero) # endif ret - .p2align 4 -L(more_vecs): - /* Align data for aligned loads in the loop. */ - andq $-VEC_SIZE, %rdi -L(aligned_more): - - /* Check the next 4 * VEC_SIZE. Only one VEC_SIZE at a time - since data is only aligned to VEC_SIZE. */ - VMOVA VEC_SIZE(%rdi), %YMM1 - addq $VEC_SIZE, %rdi - - /* Leaves only CHARS matching esi as 0. */ - vpxorq %YMM1, %YMM0, %YMM2 - VPMINU %YMM2, %YMM1, %YMM2 - /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ - VPCMP $0, %YMMZERO, %YMM2, %k0 - kmovd %k0, %eax - testl %eax, %eax - jnz L(first_vec_x0) - - VMOVA VEC_SIZE(%rdi), %YMM1 - /* Leaves only CHARS matching esi as 0. */ - vpxorq %YMM1, %YMM0, %YMM2 - VPMINU %YMM2, %YMM1, %YMM2 - /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ - VPCMP $0, %YMMZERO, %YMM2, %k0 - kmovd %k0, %eax - testl %eax, %eax - jnz L(first_vec_x1) - - VMOVA (VEC_SIZE * 2)(%rdi), %YMM1 - /* Leaves only CHARS matching esi as 0. */ - vpxorq %YMM1, %YMM0, %YMM2 - VPMINU %YMM2, %YMM1, %YMM2 - /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ - VPCMP $0, %YMMZERO, %YMM2, %k0 - kmovd %k0, %eax - testl %eax, %eax - jnz L(first_vec_x2) - - VMOVA (VEC_SIZE * 3)(%rdi), %YMM1 - /* Leaves only CHARS matching esi as 0. */ - vpxorq %YMM1, %YMM0, %YMM2 - VPMINU %YMM2, %YMM1, %YMM2 - /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ - VPCMP $0, %YMMZERO, %YMM2, %k0 - ktestd %k0, %k0 - jz L(prep_loop_4x) - - kmovd %k0, %eax + /* .p2align 5 helps keep performance more consistent if ENTRY() + alignment % 32 was either 16 or 0. As well this makes the + alignment % 32 of the loop_4x_vec fixed which makes tuning it + easier. */ + .p2align 5 +L(first_vec_x3): tzcntl %eax, %eax +# ifndef USE_AS_STRCHRNUL /* Found CHAR or the null byte. */ -# ifdef USE_AS_WCSCHR - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ - leaq (VEC_SIZE * 3)(%rdi, %rax, 4), %rax -# else - leaq (VEC_SIZE * 3)(%rdi, %rax), %rax + cmp (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %CHAR_REG + jne L(zero) # endif + /* NB: Multiply sizeof char type (1 or 4) to get the number of + bytes. */ + leaq (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax + ret + # ifndef USE_AS_STRCHRNUL - cmp (%rax), %CHAR_REG - cmovne %rdx, %rax -# endif +L(zero): + xorl %eax, %eax ret +# endif .p2align 4 -L(first_vec_x0): +L(first_vec_x4): +# ifndef USE_AS_STRCHRNUL + /* Check to see if first match was CHAR (k0) or null (k1). */ + kmovd %k0, %eax tzcntl %eax, %eax - /* Found CHAR or the null byte. */ -# ifdef USE_AS_WCSCHR - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ - leaq (%rdi, %rax, 4), %rax + kmovd %k1, %ecx + /* bzhil will not be 0 if first match was null. */ + bzhil %eax, %ecx, %ecx + jne L(zero) # else - addq %rdi, %rax -# endif -# ifndef USE_AS_STRCHRNUL - cmp (%rax), %CHAR_REG - cmovne %rdx, %rax + /* Combine CHAR and null matches. */ + kord %k0, %k1, %k0 + kmovd %k0, %eax + tzcntl %eax, %eax # endif + /* NB: Multiply sizeof char type (1 or 4) to get the number of + bytes. */ + leaq (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax ret .p2align 4 L(first_vec_x1): tzcntl %eax, %eax - /* Found CHAR or the null byte. */ -# ifdef USE_AS_WCSCHR - /* 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 # ifndef USE_AS_STRCHRNUL - cmp (%rax), %CHAR_REG - cmovne %rdx, %rax + /* Found CHAR or the null byte. */ + cmp (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %CHAR_REG + jne L(zero) + # endif + /* NB: Multiply sizeof char type (1 or 4) to get the number of + bytes. */ + leaq (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %rax ret .p2align 4 L(first_vec_x2): +# ifndef USE_AS_STRCHRNUL + /* Check to see if first match was CHAR (k0) or null (k1). */ + kmovd %k0, %eax tzcntl %eax, %eax - /* Found CHAR or the null byte. */ -# ifdef USE_AS_WCSCHR - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ - leaq (VEC_SIZE * 2)(%rdi, %rax, 4), %rax + kmovd %k1, %ecx + /* bzhil will not be 0 if first match was null. */ + bzhil %eax, %ecx, %ecx + jne L(zero) # else - leaq (VEC_SIZE * 2)(%rdi, %rax), %rax -# endif -# ifndef USE_AS_STRCHRNUL - cmp (%rax), %CHAR_REG - cmovne %rdx, %rax + /* Combine CHAR and null matches. */ + kord %k0, %k1, %k0 + kmovd %k0, %eax + tzcntl %eax, %eax # endif + /* NB: Multiply sizeof char type (1 or 4) to get the number of + bytes. */ + leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax ret -L(prep_loop_4x): - /* Align data to 4 * VEC_SIZE. */ + .p2align 4 +L(aligned_more): + /* Align data to VEC_SIZE. */ + andq $-VEC_SIZE, %rdi +L(cross_page_continue): + /* Check the next 4 * VEC_SIZE. Only one VEC_SIZE at a time since + data is only aligned to VEC_SIZE. Use two alternating methods + for checking VEC to balance latency and port contention. */ + + /* This method has higher latency but has better port + distribution. */ + VMOVA (VEC_SIZE)(%rdi), %YMM1 + /* Leaves only CHARS matching esi as 0. */ + vpxorq %YMM1, %YMM0, %YMM2 + VPMINU %YMM2, %YMM1, %YMM2 + /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ + VPCMP $0, %YMMZERO, %YMM2, %k0 + kmovd %k0, %eax + testl %eax, %eax + jnz L(first_vec_x1) + + /* This method has higher latency but has better port + distribution. */ + VMOVA (VEC_SIZE * 2)(%rdi), %YMM1 + /* Each bit in K0 represents a CHAR in YMM1. */ + VPCMP $0, %YMM1, %YMM0, %k0 + /* Each bit in K1 represents a CHAR in YMM1. */ + VPCMP $0, %YMM1, %YMMZERO, %k1 + kortestd %k0, %k1 + jnz L(first_vec_x2) + + VMOVA (VEC_SIZE * 3)(%rdi), %YMM1 + /* Leaves only CHARS matching esi as 0. */ + vpxorq %YMM1, %YMM0, %YMM2 + VPMINU %YMM2, %YMM1, %YMM2 + /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ + VPCMP $0, %YMMZERO, %YMM2, %k0 + kmovd %k0, %eax + testl %eax, %eax + jnz L(first_vec_x3) + + VMOVA (VEC_SIZE * 4)(%rdi), %YMM1 + /* Each bit in K0 represents a CHAR in YMM1. */ + VPCMP $0, %YMM1, %YMM0, %k0 + /* Each bit in K1 represents a CHAR in YMM1. */ + VPCMP $0, %YMM1, %YMMZERO, %k1 + kortestd %k0, %k1 + jnz L(first_vec_x4) + + /* Align data to VEC_SIZE * 4 for the loop. */ + addq $VEC_SIZE, %rdi andq $-(VEC_SIZE * 4), %rdi .p2align 4 L(loop_4x_vec): - /* Compare 4 * VEC at a time forward. */ + /* Check 4x VEC at a time. No penalty to imm32 offset with evex + encoding. */ VMOVA (VEC_SIZE * 4)(%rdi), %YMM1 VMOVA (VEC_SIZE * 5)(%rdi), %YMM2 VMOVA (VEC_SIZE * 6)(%rdi), %YMM3 VMOVA (VEC_SIZE * 7)(%rdi), %YMM4 - /* Leaves only CHARS matching esi as 0. */ + /* For YMM1 and YMM3 use xor to set the CHARs matching esi to + zero. */ vpxorq %YMM1, %YMM0, %YMM5 - vpxorq %YMM2, %YMM0, %YMM6 + /* For YMM2 and YMM4 cmp not equals to CHAR and store result in + k register. Its possible to save either 1 or 2 instructions + using cmp no equals method for either YMM1 or YMM1 and YMM3 + respectively but bottleneck on p5 makes it not worth it. */ + VPCMP $4, %YMM0, %YMM2, %k2 vpxorq %YMM3, %YMM0, %YMM7 - vpxorq %YMM4, %YMM0, %YMM8 - - VPMINU %YMM5, %YMM1, %YMM5 - VPMINU %YMM6, %YMM2, %YMM6 - VPMINU %YMM7, %YMM3, %YMM7 - VPMINU %YMM8, %YMM4, %YMM8 - - VPMINU %YMM5, %YMM6, %YMM1 - VPMINU %YMM7, %YMM8, %YMM2 - - VPMINU %YMM1, %YMM2, %YMM1 - - /* Each bit in K0 represents a CHAR or a null byte. */ - VPCMP $0, %YMMZERO, %YMM1, %k0 - - addq $(VEC_SIZE * 4), %rdi - - ktestd %k0, %k0 + VPCMP $4, %YMM0, %YMM4, %k4 + + /* Use min to select all zeros from either xor or end of string). + */ + VPMINU %YMM1, %YMM5, %YMM1 + VPMINU %YMM3, %YMM7, %YMM3 + + /* Use min + zeromask to select for zeros. Since k2 and k4 will + have 0 as positions that matched with CHAR which will set + zero in the corresponding destination bytes in YMM2 / YMM4. + */ + VPMINU %YMM1, %YMM2, %YMM2{%k2}{z} + VPMINU %YMM3, %YMM4, %YMM4 + VPMINU %YMM2, %YMM4, %YMM4{%k4}{z} + + VPCMP $0, %YMMZERO, %YMM4, %k1 + kmovd %k1, %ecx + subq $-(VEC_SIZE * 4), %rdi + testl %ecx, %ecx jz L(loop_4x_vec) - /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ - VPCMP $0, %YMMZERO, %YMM5, %k0 + VPCMP $0, %YMMZERO, %YMM1, %k0 kmovd %k0, %eax testl %eax, %eax - jnz L(first_vec_x0) + jnz L(last_vec_x1) - /* Each bit in K1 represents a CHAR or a null byte in YMM2. */ - VPCMP $0, %YMMZERO, %YMM6, %k1 - kmovd %k1, %eax + VPCMP $0, %YMMZERO, %YMM2, %k0 + kmovd %k0, %eax testl %eax, %eax - jnz L(first_vec_x1) - - /* Each bit in K2 represents a CHAR or a null byte in YMM3. */ - VPCMP $0, %YMMZERO, %YMM7, %k2 - /* Each bit in K3 represents a CHAR or a null byte in YMM4. */ - VPCMP $0, %YMMZERO, %YMM8, %k3 + jnz L(last_vec_x2) + VPCMP $0, %YMMZERO, %YMM3, %k0 + kmovd %k0, %eax + /* Combine YMM3 matches (eax) with YMM4 matches (ecx). */ # ifdef USE_AS_WCSCHR - /* NB: Each bit in K2/K3 represents 4-byte element. */ - kshiftlw $8, %k3, %k1 + sall $8, %ecx + orl %ecx, %eax + tzcntl %eax, %eax # else - kshiftlq $32, %k3, %k1 + salq $32, %rcx + orq %rcx, %rax + tzcntq %rax, %rax # endif +# ifndef USE_AS_STRCHRNUL + /* Check if match was CHAR or null. */ + cmp (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %CHAR_REG + jne L(zero_end) +# endif + /* NB: Multiply sizeof char type (1 or 4) to get the number of + bytes. */ + leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax + ret - /* Each bit in K1 represents a NULL or a mismatch. */ - korq %k1, %k2, %k1 - kmovq %k1, %rax +# ifndef USE_AS_STRCHRNUL +L(zero_end): + xorl %eax, %eax + ret +# endif - tzcntq %rax, %rax -# ifdef USE_AS_WCSCHR - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ - leaq (VEC_SIZE * 2)(%rdi, %rax, 4), %rax -# else - leaq (VEC_SIZE * 2)(%rdi, %rax), %rax + .p2align 4 +L(last_vec_x1): + tzcntl %eax, %eax +# ifndef USE_AS_STRCHRNUL + /* Check if match was null. */ + cmp (%rdi, %rax, CHAR_SIZE), %CHAR_REG + jne L(zero_end) # endif + /* NB: Multiply sizeof char type (1 or 4) to get the number of + bytes. */ + leaq (%rdi, %rax, CHAR_SIZE), %rax + ret + + .p2align 4 +L(last_vec_x2): + tzcntl %eax, %eax # ifndef USE_AS_STRCHRNUL - cmp (%rax), %CHAR_REG - cmovne %rdx, %rax + /* Check if match was null. */ + cmp (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %CHAR_REG + jne L(zero_end) # endif + /* NB: Multiply sizeof char type (1 or 4) to get the number of + bytes. */ + leaq (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %rax ret /* Cold case for crossing page with first load. */ .p2align 4 L(cross_page_boundary): + movq %rdi, %rdx + /* Align rdi. */ andq $-VEC_SIZE, %rdi - andl $(VEC_SIZE - 1), %ecx - VMOVA (%rdi), %YMM1 - /* Leaves only CHARS matching esi as 0. */ vpxorq %YMM1, %YMM0, %YMM2 VPMINU %YMM2, %YMM1, %YMM2 /* Each bit in K0 represents a CHAR or a null byte in YMM1. */ VPCMP $0, %YMMZERO, %YMM2, %k0 kmovd %k0, %eax - testl %eax, %eax - + /* Remove the leading bits. */ # ifdef USE_AS_WCSCHR + movl %edx, %SHIFT_REG /* NB: Divide shift count by 4 since each bit in K1 represent 4 bytes. */ - movl %ecx, %SHIFT_REG - sarl $2, %SHIFT_REG + sarl $2, %SHIFT_REG + andl $(CHAR_PER_VEC - 1), %SHIFT_REG # endif - - /* Remove the leading bits. */ sarxl %SHIFT_REG, %eax, %eax + /* If eax is zero continue. */ testl %eax, %eax - - jz L(aligned_more) + jz L(cross_page_continue) tzcntl %eax, %eax - addq %rcx, %rdi +# ifndef USE_AS_STRCHRNUL + /* Check to see if match was CHAR or null. */ + cmp (%rdx, %rax, CHAR_SIZE), %CHAR_REG + jne L(zero_end) +# endif # ifdef USE_AS_WCSCHR - /* NB: Multiply wchar_t count by 4 to get the number of bytes. */ - leaq (%rdi, %rax, 4), %rax + /* NB: Multiply wchar_t count by 4 to get the number of + bytes. */ + leaq (%rdx, %rax, CHAR_SIZE), %rax # else - addq %rdi, %rax -# endif -# ifndef USE_AS_STRCHRNUL - cmp (%rax), %CHAR_REG - cmovne %rdx, %rax + addq %rdx, %rax # endif ret -- 2.43.5