From df7e295d18ffa34f629578c0017a9881af7620f6 Mon Sep 17 00:00:00 2001 From: Noah Goldstein Date: Thu, 21 Apr 2022 20:52:29 -0500 Subject: [PATCH] x86: Optimize {str|wcs}rchr-avx2 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: 0.832 See email for all results. Full xcheck passes on x86_64 with and without multiarch enabled. Reviewed-by: H.J. Lu --- sysdeps/x86_64/multiarch/strrchr-avx2.S | 446 +++++++++++++++--------- 1 file changed, 279 insertions(+), 167 deletions(-) diff --git a/sysdeps/x86_64/multiarch/strrchr-avx2.S b/sysdeps/x86_64/multiarch/strrchr-avx2.S index 1df2adfad0..bd26ba80d5 100644 --- a/sysdeps/x86_64/multiarch/strrchr-avx2.S +++ b/sysdeps/x86_64/multiarch/strrchr-avx2.S @@ -27,9 +27,13 @@ # ifdef USE_AS_WCSRCHR # define VPBROADCAST vpbroadcastd # define VPCMPEQ vpcmpeqd +# define VPMIN vpminud +# define CHAR_SIZE 4 # else # define VPBROADCAST vpbroadcastb # define VPCMPEQ vpcmpeqb +# define VPMIN vpminub +# define CHAR_SIZE 1 # endif # ifndef VZEROUPPER @@ -41,196 +45,304 @@ # endif # define VEC_SIZE 32 +# define PAGE_SIZE 4096 - .section SECTION(.text),"ax",@progbits -ENTRY (STRRCHR) - movd %esi, %xmm4 - movl %edi, %ecx + .section SECTION(.text), "ax", @progbits +ENTRY(STRRCHR) + movd %esi, %xmm7 + movl %edi, %eax /* Broadcast CHAR to YMM4. */ - VPBROADCAST %xmm4, %ymm4 + VPBROADCAST %xmm7, %ymm7 vpxor %xmm0, %xmm0, %xmm0 - /* 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) + /* Shift here instead of `andl` to save code size (saves a fetch + block). */ + sall $20, %eax + cmpl $((PAGE_SIZE - VEC_SIZE) << 20), %eax + ja L(cross_page) +L(page_cross_continue): vmovdqu (%rdi), %ymm1 - VPCMPEQ %ymm1, %ymm0, %ymm2 - VPCMPEQ %ymm1, %ymm4, %ymm3 - vpmovmskb %ymm2, %ecx - vpmovmskb %ymm3, %eax - addq $VEC_SIZE, %rdi - - testl %eax, %eax - jnz L(first_vec) - + /* Check end of string match. */ + VPCMPEQ %ymm1, %ymm0, %ymm6 + vpmovmskb %ymm6, %ecx testl %ecx, %ecx - jnz L(return_null) + jz L(aligned_more) - andq $-VEC_SIZE, %rdi - xorl %edx, %edx - jmp L(aligned_loop) - - .p2align 4 -L(first_vec): - /* Check if there is a nul CHAR. */ - 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 - vmovdqa (%rdi), %ymm1 - VPCMPEQ %ymm1, %ymm0, %ymm2 - VPCMPEQ %ymm1, %ymm4, %ymm3 - vpmovmskb %ymm2, %edx - vpmovmskb %ymm3, %eax - shrl %cl, %edx - shrl %cl, %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 - - .p2align 4 -L(aligned_loop): - vmovdqa (%rdi), %ymm1 - VPCMPEQ %ymm1, %ymm0, %ymm2 - addq $VEC_SIZE, %rdi - VPCMPEQ %ymm1, %ymm4, %ymm3 - vpmovmskb %ymm2, %ecx - vpmovmskb %ymm3, %eax - orl %eax, %ecx - jnz L(char_nor_null) - - vmovdqa (%rdi), %ymm1 - VPCMPEQ %ymm1, %ymm0, %ymm2 - add $VEC_SIZE, %rdi - VPCMPEQ %ymm1, %ymm4, %ymm3 - vpmovmskb %ymm2, %ecx - vpmovmskb %ymm3, %eax - orl %eax, %ecx - jnz L(char_nor_null) - - vmovdqa (%rdi), %ymm1 - VPCMPEQ %ymm1, %ymm0, %ymm2 - addq $VEC_SIZE, %rdi - VPCMPEQ %ymm1, %ymm4, %ymm3 - vpmovmskb %ymm2, %ecx - vpmovmskb %ymm3, %eax - orl %eax, %ecx - jnz L(char_nor_null) - - vmovdqa (%rdi), %ymm1 - VPCMPEQ %ymm1, %ymm0, %ymm2 - addq $VEC_SIZE, %rdi - VPCMPEQ %ymm1, %ymm4, %ymm3 - vpmovmskb %ymm2, %ecx - vpmovmskb %ymm3, %eax - orl %eax, %ecx - jz L(aligned_loop) - - .p2align 4 -L(char_nor_null): - /* Find a CHAR or a nul CHAR in a loop. */ - testl %eax, %eax - jnz L(match) -L(return_value): - testl %edx, %edx - jz L(return_null) - movl %edx, %eax - movq %rsi, %rdi - -# ifdef USE_AS_WCSRCHR - /* Keep the first bit for each matching CHAR for bsr. */ - andl $0x11111111, %eax -# endif + /* Only check match with search CHAR if needed. */ + VPCMPEQ %ymm1, %ymm7, %ymm1 + vpmovmskb %ymm1, %eax + /* Check if match before first zero. */ + blsmskl %ecx, %ecx + andl %ecx, %eax + jz L(ret0) bsrl %eax, %eax - leaq -VEC_SIZE(%rdi, %rax), %rax + addq %rdi, %rax + /* We are off by 3 for wcsrchr if search CHAR is non-zero. If + search CHAR is zero we are correct. Either way `andq + -CHAR_SIZE, %rax` gets the correct result. */ +# ifdef USE_AS_WCSRCHR + andq $-CHAR_SIZE, %rax +# endif +L(ret0): L(return_vzeroupper): ZERO_UPPER_VEC_REGISTERS_RETURN + /* Returns for first vec x1/x2 have hard coded backward search + path for earlier matches. */ + .p2align 4,, 10 +L(first_vec_x1): + VPCMPEQ %ymm2, %ymm7, %ymm6 + vpmovmskb %ymm6, %eax + blsmskl %ecx, %ecx + andl %ecx, %eax + jnz L(first_vec_x1_return) + + .p2align 4,, 4 +L(first_vec_x0_test): + VPCMPEQ %ymm1, %ymm7, %ymm6 + vpmovmskb %ymm6, %eax + testl %eax, %eax + jz L(ret1) + bsrl %eax, %eax + addq %r8, %rax +# ifdef USE_AS_WCSRCHR + andq $-CHAR_SIZE, %rax +# endif +L(ret1): + VZEROUPPER_RETURN + + .p2align 4,, 10 +L(first_vec_x0_x1_test): + VPCMPEQ %ymm2, %ymm7, %ymm6 + vpmovmskb %ymm6, %eax + /* Check ymm2 for search CHAR match. If no match then check ymm1 + before returning. */ + testl %eax, %eax + jz L(first_vec_x0_test) + .p2align 4,, 4 +L(first_vec_x1_return): + bsrl %eax, %eax + leaq 1(%rdi, %rax), %rax +# ifdef USE_AS_WCSRCHR + andq $-CHAR_SIZE, %rax +# endif + VZEROUPPER_RETURN + + + .p2align 4,, 10 +L(first_vec_x2): + VPCMPEQ %ymm3, %ymm7, %ymm6 + vpmovmskb %ymm6, %eax + blsmskl %ecx, %ecx + /* If no in-range search CHAR match in ymm3 then need to check + ymm1/ymm2 for an earlier match (we delay checking search + CHAR matches until needed). */ + andl %ecx, %eax + jz L(first_vec_x0_x1_test) + bsrl %eax, %eax + leaq (VEC_SIZE + 1)(%rdi, %rax), %rax +# ifdef USE_AS_WCSRCHR + andq $-CHAR_SIZE, %rax +# endif + VZEROUPPER_RETURN + + .p2align 4 -L(match): - /* Find a CHAR. Check if there is a nul CHAR. */ - vpmovmskb %ymm2, %ecx +L(aligned_more): + /* Save original pointer if match was in VEC 0. */ + movq %rdi, %r8 + + /* Align src. */ + orq $(VEC_SIZE - 1), %rdi + vmovdqu 1(%rdi), %ymm2 + VPCMPEQ %ymm2, %ymm0, %ymm6 + vpmovmskb %ymm6, %ecx testl %ecx, %ecx - jnz L(find_nul) + jnz L(first_vec_x1) - /* Remember the match and keep searching. */ - movl %eax, %edx + vmovdqu (VEC_SIZE + 1)(%rdi), %ymm3 + VPCMPEQ %ymm3, %ymm0, %ymm6 + vpmovmskb %ymm6, %ecx + testl %ecx, %ecx + jnz L(first_vec_x2) + + /* Save pointer again before realigning. */ movq %rdi, %rsi - jmp L(aligned_loop) - + addq $(VEC_SIZE + 1), %rdi + andq $-(VEC_SIZE * 2), %rdi .p2align 4 -L(find_nul): -# ifdef USE_AS_WCSRCHR - /* Keep the first bit for each matching CHAR for bsr. */ - andl $0x11111111, %ecx - andl $0x11111111, %eax -# endif - /* Mask out any matching bits after the nul CHAR. */ - movl %ecx, %r8d - subl $1, %r8d - xorl %ecx, %r8d - andl %r8d, %eax +L(first_aligned_loop): + /* Do 2x VEC at a time. Any more and the cost of finding the + match outweights loop benefit. */ + vmovdqa (VEC_SIZE * 0)(%rdi), %ymm4 + vmovdqa (VEC_SIZE * 1)(%rdi), %ymm5 + + VPCMPEQ %ymm4, %ymm7, %ymm6 + VPMIN %ymm4, %ymm5, %ymm8 + VPCMPEQ %ymm5, %ymm7, %ymm10 + vpor %ymm6, %ymm10, %ymm5 + VPCMPEQ %ymm8, %ymm0, %ymm8 + vpor %ymm5, %ymm8, %ymm9 + + vpmovmskb %ymm9, %eax + addq $(VEC_SIZE * 2), %rdi + /* No zero or search CHAR. */ testl %eax, %eax - /* If there is no CHAR here, return the remembered one. */ - jz L(return_value) - bsrl %eax, %eax - leaq -VEC_SIZE(%rdi, %rax), %rax - VZEROUPPER_RETURN + jz L(first_aligned_loop) - .p2align 4 -L(char_and_nul): - /* Find both a CHAR and a nul CHAR. */ - addq %rcx, %rdi - movl %edx, %ecx -L(char_and_nul_in_first_vec): -# ifdef USE_AS_WCSRCHR - /* Keep the first bit for each matching CHAR for bsr. */ - andl $0x11111111, %ecx - andl $0x11111111, %eax -# endif - /* Mask out any matching bits after the nul CHAR. */ - movl %ecx, %r8d - subl $1, %r8d - xorl %ecx, %r8d - andl %r8d, %eax + /* If no zero CHAR then go to second loop (this allows us to + throw away all prior work). */ + vpmovmskb %ymm8, %ecx + testl %ecx, %ecx + jz L(second_aligned_loop_prep) + + /* Search char could be zero so we need to get the true match. + */ + vpmovmskb %ymm5, %eax testl %eax, %eax - /* Return null pointer if the nul CHAR comes first. */ - jz L(return_null) - bsrl %eax, %eax - leaq -VEC_SIZE(%rdi, %rax), %rax + jnz L(first_aligned_loop_return) + + .p2align 4,, 4 +L(first_vec_x1_or_x2): + VPCMPEQ %ymm3, %ymm7, %ymm3 + VPCMPEQ %ymm2, %ymm7, %ymm2 + vpmovmskb %ymm3, %eax + vpmovmskb %ymm2, %edx + /* Use add for macro-fusion. */ + addq %rax, %rdx + jz L(first_vec_x0_test) + /* NB: We could move this shift to before the branch and save a + bit of code size / performance on the fall through. The + branch leads to the null case which generally seems hotter + than char in first 3x VEC. */ + salq $32, %rax + addq %rdx, %rax + bsrq %rax, %rax + leaq 1(%rsi, %rax), %rax +# ifdef USE_AS_WCSRCHR + andq $-CHAR_SIZE, %rax +# endif VZEROUPPER_RETURN + .p2align 4,, 8 +L(first_aligned_loop_return): + VPCMPEQ %ymm4, %ymm0, %ymm4 + vpmovmskb %ymm4, %edx + salq $32, %rcx + orq %rdx, %rcx + + vpmovmskb %ymm10, %eax + vpmovmskb %ymm6, %edx + salq $32, %rax + orq %rdx, %rax + blsmskq %rcx, %rcx + andq %rcx, %rax + jz L(first_vec_x1_or_x2) + + bsrq %rax, %rax + leaq -(VEC_SIZE * 2)(%rdi, %rax), %rax +# ifdef USE_AS_WCSRCHR + andq $-CHAR_SIZE, %rax +# endif + VZEROUPPER_RETURN + + /* Search char cannot be zero. */ + .p2align 4 +L(second_aligned_loop_set_furthest_match): + /* Save VEC and pointer from most recent match. */ +L(second_aligned_loop_prep): + movq %rdi, %rsi + vmovdqu %ymm6, %ymm2 + vmovdqu %ymm10, %ymm3 + .p2align 4 -L(return_null): - xorl %eax, %eax +L(second_aligned_loop): + /* Search 2x at at time. */ + vmovdqa (VEC_SIZE * 0)(%rdi), %ymm4 + vmovdqa (VEC_SIZE * 1)(%rdi), %ymm5 + + VPCMPEQ %ymm4, %ymm7, %ymm6 + VPMIN %ymm4, %ymm5, %ymm1 + VPCMPEQ %ymm5, %ymm7, %ymm10 + vpor %ymm6, %ymm10, %ymm5 + VPCMPEQ %ymm1, %ymm0, %ymm1 + vpor %ymm5, %ymm1, %ymm9 + + vpmovmskb %ymm9, %eax + addq $(VEC_SIZE * 2), %rdi + testl %eax, %eax + jz L(second_aligned_loop) + vpmovmskb %ymm1, %ecx + testl %ecx, %ecx + jz L(second_aligned_loop_set_furthest_match) + vpmovmskb %ymm5, %eax + testl %eax, %eax + jnz L(return_new_match) + + /* This is the hot patch. We know CHAR is inbounds and that + ymm3/ymm2 have latest match. */ + .p2align 4,, 4 +L(return_old_match): + vpmovmskb %ymm3, %eax + vpmovmskb %ymm2, %edx + salq $32, %rax + orq %rdx, %rax + bsrq %rax, %rax + /* Search char cannot be zero so safe to just use lea for + wcsrchr. */ + leaq (VEC_SIZE * -2 -(CHAR_SIZE - 1))(%rsi, %rax), %rax VZEROUPPER_RETURN -END (STRRCHR) + /* Last iteration also potentially has a match. */ + .p2align 4,, 8 +L(return_new_match): + VPCMPEQ %ymm4, %ymm0, %ymm4 + vpmovmskb %ymm4, %edx + salq $32, %rcx + orq %rdx, %rcx + + vpmovmskb %ymm10, %eax + vpmovmskb %ymm6, %edx + salq $32, %rax + orq %rdx, %rax + blsmskq %rcx, %rcx + andq %rcx, %rax + jz L(return_old_match) + bsrq %rax, %rax + /* Search char cannot be zero so safe to just use lea for + wcsrchr. */ + leaq (VEC_SIZE * -2 -(CHAR_SIZE - 1))(%rdi, %rax), %rax + VZEROUPPER_RETURN + + .p2align 4,, 4 +L(cross_page): + movq %rdi, %rsi + andq $-VEC_SIZE, %rsi + vmovdqu (%rsi), %ymm1 + VPCMPEQ %ymm1, %ymm0, %ymm6 + vpmovmskb %ymm6, %ecx + /* Shift out zero CHAR matches that are before the begining of + src (rdi). */ + shrxl %edi, %ecx, %ecx + testl %ecx, %ecx + jz L(page_cross_continue) + VPCMPEQ %ymm1, %ymm7, %ymm1 + vpmovmskb %ymm1, %eax + + /* Shift out search CHAR matches that are before the begining of + src (rdi). */ + shrxl %edi, %eax, %eax + blsmskl %ecx, %ecx + /* Check if any search CHAR match in range. */ + andl %ecx, %eax + jz L(ret2) + bsrl %eax, %eax + addq %rdi, %rax +# ifdef USE_AS_WCSRCHR + andq $-CHAR_SIZE, %rax +# endif +L(ret2): + VZEROUPPER_RETURN +END(STRRCHR) #endif