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497 lines
12 KiB
497 lines
12 KiB
commit 00f09a14d2818f438959e764834abb3913f2b20a |
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Author: Noah Goldstein <goldstein.w.n@gmail.com> |
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Date: Thu Apr 21 20:52:29 2022 -0500 |
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x86: Optimize {str|wcs}rchr-avx2 |
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The new code unrolls the main loop slightly without adding too much |
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overhead and minimizes the comparisons for the search CHAR. |
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Geometric Mean of all benchmarks New / Old: 0.832 |
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See email for all results. |
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Full xcheck passes on x86_64 with and without multiarch enabled. |
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Reviewed-by: H.J. Lu <hjl.tools@gmail.com> |
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(cherry picked from commit df7e295d18ffa34f629578c0017a9881af7620f6) |
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diff --git a/sysdeps/x86_64/multiarch/strrchr-avx2.S b/sysdeps/x86_64/multiarch/strrchr-avx2.S |
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index 0deba97114d3b83d..b8dec737d5213b25 100644 |
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--- a/sysdeps/x86_64/multiarch/strrchr-avx2.S |
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+++ b/sysdeps/x86_64/multiarch/strrchr-avx2.S |
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@@ -27,9 +27,13 @@ |
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# ifdef USE_AS_WCSRCHR |
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# define VPBROADCAST vpbroadcastd |
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# define VPCMPEQ vpcmpeqd |
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+# define VPMIN vpminud |
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+# define CHAR_SIZE 4 |
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# else |
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# define VPBROADCAST vpbroadcastb |
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# define VPCMPEQ vpcmpeqb |
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+# define VPMIN vpminub |
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+# define CHAR_SIZE 1 |
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# endif |
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# ifndef VZEROUPPER |
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@@ -41,196 +45,304 @@ |
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# endif |
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# define VEC_SIZE 32 |
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+# define PAGE_SIZE 4096 |
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- .section SECTION(.text),"ax",@progbits |
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-ENTRY (STRRCHR) |
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- movd %esi, %xmm4 |
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- movl %edi, %ecx |
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+ .section SECTION(.text), "ax", @progbits |
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+ENTRY(STRRCHR) |
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+ movd %esi, %xmm7 |
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+ movl %edi, %eax |
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/* Broadcast CHAR to YMM4. */ |
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- VPBROADCAST %xmm4, %ymm4 |
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+ VPBROADCAST %xmm7, %ymm7 |
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vpxor %xmm0, %xmm0, %xmm0 |
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- /* Check if we may cross page boundary with one vector load. */ |
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- andl $(2 * VEC_SIZE - 1), %ecx |
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- cmpl $VEC_SIZE, %ecx |
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- ja L(cros_page_boundary) |
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+ /* Shift here instead of `andl` to save code size (saves a fetch |
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+ block). */ |
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+ sall $20, %eax |
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+ cmpl $((PAGE_SIZE - VEC_SIZE) << 20), %eax |
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+ ja L(cross_page) |
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+L(page_cross_continue): |
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vmovdqu (%rdi), %ymm1 |
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- VPCMPEQ %ymm1, %ymm0, %ymm2 |
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- VPCMPEQ %ymm1, %ymm4, %ymm3 |
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- vpmovmskb %ymm2, %ecx |
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- vpmovmskb %ymm3, %eax |
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- addq $VEC_SIZE, %rdi |
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+ /* Check end of string match. */ |
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+ VPCMPEQ %ymm1, %ymm0, %ymm6 |
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+ vpmovmskb %ymm6, %ecx |
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+ testl %ecx, %ecx |
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+ jz L(aligned_more) |
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+ |
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+ /* Only check match with search CHAR if needed. */ |
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+ VPCMPEQ %ymm1, %ymm7, %ymm1 |
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+ vpmovmskb %ymm1, %eax |
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+ /* Check if match before first zero. */ |
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+ blsmskl %ecx, %ecx |
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+ andl %ecx, %eax |
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+ jz L(ret0) |
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+ bsrl %eax, %eax |
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+ addq %rdi, %rax |
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+ /* We are off by 3 for wcsrchr if search CHAR is non-zero. If |
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+ search CHAR is zero we are correct. Either way `andq |
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+ -CHAR_SIZE, %rax` gets the correct result. */ |
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+# ifdef USE_AS_WCSRCHR |
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+ andq $-CHAR_SIZE, %rax |
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+# endif |
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+L(ret0): |
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+L(return_vzeroupper): |
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+ ZERO_UPPER_VEC_REGISTERS_RETURN |
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+ |
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+ /* Returns for first vec x1/x2 have hard coded backward search |
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+ path for earlier matches. */ |
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+ .p2align 4,, 10 |
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+L(first_vec_x1): |
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+ VPCMPEQ %ymm2, %ymm7, %ymm6 |
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+ vpmovmskb %ymm6, %eax |
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+ blsmskl %ecx, %ecx |
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+ andl %ecx, %eax |
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+ jnz L(first_vec_x1_return) |
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+ |
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+ .p2align 4,, 4 |
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+L(first_vec_x0_test): |
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+ VPCMPEQ %ymm1, %ymm7, %ymm6 |
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+ vpmovmskb %ymm6, %eax |
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+ testl %eax, %eax |
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+ jz L(ret1) |
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+ bsrl %eax, %eax |
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+ addq %r8, %rax |
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+# ifdef USE_AS_WCSRCHR |
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+ andq $-CHAR_SIZE, %rax |
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+# endif |
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+L(ret1): |
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+ VZEROUPPER_RETURN |
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+ .p2align 4,, 10 |
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+L(first_vec_x0_x1_test): |
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+ VPCMPEQ %ymm2, %ymm7, %ymm6 |
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+ vpmovmskb %ymm6, %eax |
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+ /* Check ymm2 for search CHAR match. If no match then check ymm1 |
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+ before returning. */ |
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testl %eax, %eax |
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- jnz L(first_vec) |
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+ jz L(first_vec_x0_test) |
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+ .p2align 4,, 4 |
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+L(first_vec_x1_return): |
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+ bsrl %eax, %eax |
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+ leaq 1(%rdi, %rax), %rax |
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+# ifdef USE_AS_WCSRCHR |
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+ andq $-CHAR_SIZE, %rax |
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+# endif |
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+ VZEROUPPER_RETURN |
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- testl %ecx, %ecx |
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- jnz L(return_null) |
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- andq $-VEC_SIZE, %rdi |
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- xorl %edx, %edx |
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- jmp L(aligned_loop) |
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+ .p2align 4,, 10 |
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+L(first_vec_x2): |
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+ VPCMPEQ %ymm3, %ymm7, %ymm6 |
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+ vpmovmskb %ymm6, %eax |
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+ blsmskl %ecx, %ecx |
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+ /* If no in-range search CHAR match in ymm3 then need to check |
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+ ymm1/ymm2 for an earlier match (we delay checking search |
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+ CHAR matches until needed). */ |
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+ andl %ecx, %eax |
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+ jz L(first_vec_x0_x1_test) |
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+ bsrl %eax, %eax |
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+ leaq (VEC_SIZE + 1)(%rdi, %rax), %rax |
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+# ifdef USE_AS_WCSRCHR |
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+ andq $-CHAR_SIZE, %rax |
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+# endif |
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+ VZEROUPPER_RETURN |
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+ |
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.p2align 4 |
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-L(first_vec): |
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- /* Check if there is a nul CHAR. */ |
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+L(aligned_more): |
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+ /* Save original pointer if match was in VEC 0. */ |
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+ movq %rdi, %r8 |
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+ |
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+ /* Align src. */ |
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+ orq $(VEC_SIZE - 1), %rdi |
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+ vmovdqu 1(%rdi), %ymm2 |
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+ VPCMPEQ %ymm2, %ymm0, %ymm6 |
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+ vpmovmskb %ymm6, %ecx |
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testl %ecx, %ecx |
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- jnz L(char_and_nul_in_first_vec) |
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+ jnz L(first_vec_x1) |
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- /* Remember the match and keep searching. */ |
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- movl %eax, %edx |
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- movq %rdi, %rsi |
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- andq $-VEC_SIZE, %rdi |
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- jmp L(aligned_loop) |
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+ vmovdqu (VEC_SIZE + 1)(%rdi), %ymm3 |
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+ VPCMPEQ %ymm3, %ymm0, %ymm6 |
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+ vpmovmskb %ymm6, %ecx |
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+ testl %ecx, %ecx |
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+ jnz L(first_vec_x2) |
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+ /* Save pointer again before realigning. */ |
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+ movq %rdi, %rsi |
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+ addq $(VEC_SIZE + 1), %rdi |
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+ andq $-(VEC_SIZE * 2), %rdi |
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.p2align 4 |
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-L(cros_page_boundary): |
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- andl $(VEC_SIZE - 1), %ecx |
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- andq $-VEC_SIZE, %rdi |
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- vmovdqa (%rdi), %ymm1 |
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- VPCMPEQ %ymm1, %ymm0, %ymm2 |
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- VPCMPEQ %ymm1, %ymm4, %ymm3 |
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- vpmovmskb %ymm2, %edx |
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- vpmovmskb %ymm3, %eax |
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- shrl %cl, %edx |
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- shrl %cl, %eax |
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- addq $VEC_SIZE, %rdi |
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- |
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- /* Check if there is a CHAR. */ |
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+L(first_aligned_loop): |
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+ /* Do 2x VEC at a time. Any more and the cost of finding the |
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+ match outweights loop benefit. */ |
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+ vmovdqa (VEC_SIZE * 0)(%rdi), %ymm4 |
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+ vmovdqa (VEC_SIZE * 1)(%rdi), %ymm5 |
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+ |
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+ VPCMPEQ %ymm4, %ymm7, %ymm6 |
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+ VPMIN %ymm4, %ymm5, %ymm8 |
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+ VPCMPEQ %ymm5, %ymm7, %ymm10 |
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+ vpor %ymm6, %ymm10, %ymm5 |
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+ VPCMPEQ %ymm8, %ymm0, %ymm8 |
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+ vpor %ymm5, %ymm8, %ymm9 |
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+ |
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+ vpmovmskb %ymm9, %eax |
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+ addq $(VEC_SIZE * 2), %rdi |
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+ /* No zero or search CHAR. */ |
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testl %eax, %eax |
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- jnz L(found_char) |
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- |
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- testl %edx, %edx |
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- jnz L(return_null) |
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+ jz L(first_aligned_loop) |
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- jmp L(aligned_loop) |
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- |
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- .p2align 4 |
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-L(found_char): |
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- testl %edx, %edx |
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- jnz L(char_and_nul) |
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+ /* If no zero CHAR then go to second loop (this allows us to |
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+ throw away all prior work). */ |
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+ vpmovmskb %ymm8, %ecx |
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+ testl %ecx, %ecx |
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+ jz L(second_aligned_loop_prep) |
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- /* Remember the match and keep searching. */ |
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- movl %eax, %edx |
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- leaq (%rdi, %rcx), %rsi |
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+ /* Search char could be zero so we need to get the true match. |
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+ */ |
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+ vpmovmskb %ymm5, %eax |
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+ testl %eax, %eax |
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+ jnz L(first_aligned_loop_return) |
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- .p2align 4 |
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-L(aligned_loop): |
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- vmovdqa (%rdi), %ymm1 |
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- VPCMPEQ %ymm1, %ymm0, %ymm2 |
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- addq $VEC_SIZE, %rdi |
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- VPCMPEQ %ymm1, %ymm4, %ymm3 |
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- vpmovmskb %ymm2, %ecx |
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- vpmovmskb %ymm3, %eax |
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- orl %eax, %ecx |
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- jnz L(char_nor_null) |
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- |
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- vmovdqa (%rdi), %ymm1 |
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- VPCMPEQ %ymm1, %ymm0, %ymm2 |
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- add $VEC_SIZE, %rdi |
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- VPCMPEQ %ymm1, %ymm4, %ymm3 |
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- vpmovmskb %ymm2, %ecx |
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+ .p2align 4,, 4 |
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+L(first_vec_x1_or_x2): |
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+ VPCMPEQ %ymm3, %ymm7, %ymm3 |
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+ VPCMPEQ %ymm2, %ymm7, %ymm2 |
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vpmovmskb %ymm3, %eax |
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- orl %eax, %ecx |
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- jnz L(char_nor_null) |
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- |
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- vmovdqa (%rdi), %ymm1 |
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- VPCMPEQ %ymm1, %ymm0, %ymm2 |
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- addq $VEC_SIZE, %rdi |
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- VPCMPEQ %ymm1, %ymm4, %ymm3 |
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- vpmovmskb %ymm2, %ecx |
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- vpmovmskb %ymm3, %eax |
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- orl %eax, %ecx |
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- jnz L(char_nor_null) |
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- |
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- vmovdqa (%rdi), %ymm1 |
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- VPCMPEQ %ymm1, %ymm0, %ymm2 |
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- addq $VEC_SIZE, %rdi |
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- VPCMPEQ %ymm1, %ymm4, %ymm3 |
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- vpmovmskb %ymm2, %ecx |
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- vpmovmskb %ymm3, %eax |
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- orl %eax, %ecx |
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- jz L(aligned_loop) |
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- |
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- .p2align 4 |
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-L(char_nor_null): |
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- /* Find a CHAR or a nul CHAR in a loop. */ |
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- testl %eax, %eax |
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- jnz L(match) |
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-L(return_value): |
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- testl %edx, %edx |
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- jz L(return_null) |
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- movl %edx, %eax |
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- movq %rsi, %rdi |
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+ vpmovmskb %ymm2, %edx |
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+ /* Use add for macro-fusion. */ |
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+ addq %rax, %rdx |
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+ jz L(first_vec_x0_test) |
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+ /* NB: We could move this shift to before the branch and save a |
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+ bit of code size / performance on the fall through. The |
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+ branch leads to the null case which generally seems hotter |
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+ than char in first 3x VEC. */ |
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+ salq $32, %rax |
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+ addq %rdx, %rax |
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+ bsrq %rax, %rax |
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+ leaq 1(%rsi, %rax), %rax |
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+# ifdef USE_AS_WCSRCHR |
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+ andq $-CHAR_SIZE, %rax |
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+# endif |
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+ VZEROUPPER_RETURN |
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+ .p2align 4,, 8 |
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+L(first_aligned_loop_return): |
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+ VPCMPEQ %ymm4, %ymm0, %ymm4 |
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+ vpmovmskb %ymm4, %edx |
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+ salq $32, %rcx |
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+ orq %rdx, %rcx |
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+ |
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+ vpmovmskb %ymm10, %eax |
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+ vpmovmskb %ymm6, %edx |
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+ salq $32, %rax |
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+ orq %rdx, %rax |
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+ blsmskq %rcx, %rcx |
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+ andq %rcx, %rax |
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+ jz L(first_vec_x1_or_x2) |
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+ |
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+ bsrq %rax, %rax |
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+ leaq -(VEC_SIZE * 2)(%rdi, %rax), %rax |
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# ifdef USE_AS_WCSRCHR |
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- /* Keep the first bit for each matching CHAR for bsr. */ |
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- andl $0x11111111, %eax |
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+ andq $-CHAR_SIZE, %rax |
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# endif |
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- bsrl %eax, %eax |
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- leaq -VEC_SIZE(%rdi, %rax), %rax |
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-L(return_vzeroupper): |
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- ZERO_UPPER_VEC_REGISTERS_RETURN |
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+ VZEROUPPER_RETURN |
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+ /* Search char cannot be zero. */ |
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.p2align 4 |
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-L(match): |
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- /* Find a CHAR. Check if there is a nul CHAR. */ |
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- vpmovmskb %ymm2, %ecx |
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- testl %ecx, %ecx |
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- jnz L(find_nul) |
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- |
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- /* Remember the match and keep searching. */ |
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- movl %eax, %edx |
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+L(second_aligned_loop_set_furthest_match): |
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+ /* Save VEC and pointer from most recent match. */ |
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+L(second_aligned_loop_prep): |
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movq %rdi, %rsi |
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- jmp L(aligned_loop) |
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+ vmovdqu %ymm6, %ymm2 |
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+ vmovdqu %ymm10, %ymm3 |
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.p2align 4 |
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-L(find_nul): |
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-# ifdef USE_AS_WCSRCHR |
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- /* Keep the first bit for each matching CHAR for bsr. */ |
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- andl $0x11111111, %ecx |
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- andl $0x11111111, %eax |
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-# endif |
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- /* Mask out any matching bits after the nul CHAR. */ |
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- movl %ecx, %r8d |
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- subl $1, %r8d |
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- xorl %ecx, %r8d |
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- andl %r8d, %eax |
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+L(second_aligned_loop): |
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+ /* Search 2x at at time. */ |
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+ vmovdqa (VEC_SIZE * 0)(%rdi), %ymm4 |
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+ vmovdqa (VEC_SIZE * 1)(%rdi), %ymm5 |
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+ |
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+ VPCMPEQ %ymm4, %ymm7, %ymm6 |
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+ VPMIN %ymm4, %ymm5, %ymm1 |
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+ VPCMPEQ %ymm5, %ymm7, %ymm10 |
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+ vpor %ymm6, %ymm10, %ymm5 |
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+ VPCMPEQ %ymm1, %ymm0, %ymm1 |
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+ vpor %ymm5, %ymm1, %ymm9 |
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+ |
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+ vpmovmskb %ymm9, %eax |
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+ addq $(VEC_SIZE * 2), %rdi |
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testl %eax, %eax |
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- /* If there is no CHAR here, return the remembered one. */ |
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- jz L(return_value) |
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- bsrl %eax, %eax |
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- leaq -VEC_SIZE(%rdi, %rax), %rax |
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- VZEROUPPER_RETURN |
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- |
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- .p2align 4 |
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-L(char_and_nul): |
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- /* Find both a CHAR and a nul CHAR. */ |
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- addq %rcx, %rdi |
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- movl %edx, %ecx |
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-L(char_and_nul_in_first_vec): |
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-# ifdef USE_AS_WCSRCHR |
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- /* Keep the first bit for each matching CHAR for bsr. */ |
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- andl $0x11111111, %ecx |
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- andl $0x11111111, %eax |
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-# endif |
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- /* Mask out any matching bits after the nul CHAR. */ |
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- movl %ecx, %r8d |
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- subl $1, %r8d |
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- xorl %ecx, %r8d |
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- andl %r8d, %eax |
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+ jz L(second_aligned_loop) |
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+ vpmovmskb %ymm1, %ecx |
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+ testl %ecx, %ecx |
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+ jz L(second_aligned_loop_set_furthest_match) |
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+ vpmovmskb %ymm5, %eax |
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testl %eax, %eax |
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- /* Return null pointer if the nul CHAR comes first. */ |
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- jz L(return_null) |
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- bsrl %eax, %eax |
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- leaq -VEC_SIZE(%rdi, %rax), %rax |
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+ jnz L(return_new_match) |
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+ |
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+ /* This is the hot patch. We know CHAR is inbounds and that |
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+ ymm3/ymm2 have latest match. */ |
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+ .p2align 4,, 4 |
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+L(return_old_match): |
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+ vpmovmskb %ymm3, %eax |
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+ vpmovmskb %ymm2, %edx |
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+ salq $32, %rax |
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+ orq %rdx, %rax |
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+ bsrq %rax, %rax |
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+ /* Search char cannot be zero so safe to just use lea for |
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+ wcsrchr. */ |
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+ leaq (VEC_SIZE * -2 -(CHAR_SIZE - 1))(%rsi, %rax), %rax |
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VZEROUPPER_RETURN |
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- .p2align 4 |
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-L(return_null): |
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- xorl %eax, %eax |
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+ /* Last iteration also potentially has a match. */ |
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+ .p2align 4,, 8 |
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+L(return_new_match): |
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+ VPCMPEQ %ymm4, %ymm0, %ymm4 |
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+ vpmovmskb %ymm4, %edx |
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+ salq $32, %rcx |
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+ orq %rdx, %rcx |
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+ |
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+ vpmovmskb %ymm10, %eax |
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+ vpmovmskb %ymm6, %edx |
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+ salq $32, %rax |
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+ orq %rdx, %rax |
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+ blsmskq %rcx, %rcx |
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+ andq %rcx, %rax |
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+ jz L(return_old_match) |
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+ bsrq %rax, %rax |
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+ /* Search char cannot be zero so safe to just use lea for |
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+ wcsrchr. */ |
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+ leaq (VEC_SIZE * -2 -(CHAR_SIZE - 1))(%rdi, %rax), %rax |
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VZEROUPPER_RETURN |
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-END (STRRCHR) |
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+ .p2align 4,, 4 |
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+L(cross_page): |
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+ movq %rdi, %rsi |
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+ andq $-VEC_SIZE, %rsi |
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+ vmovdqu (%rsi), %ymm1 |
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+ VPCMPEQ %ymm1, %ymm0, %ymm6 |
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+ vpmovmskb %ymm6, %ecx |
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+ /* Shift out zero CHAR matches that are before the begining of |
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+ src (rdi). */ |
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+ shrxl %edi, %ecx, %ecx |
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+ testl %ecx, %ecx |
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+ jz L(page_cross_continue) |
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+ VPCMPEQ %ymm1, %ymm7, %ymm1 |
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+ vpmovmskb %ymm1, %eax |
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+ |
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+ /* Shift out search CHAR matches that are before the begining of |
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+ src (rdi). */ |
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+ 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
|
|
|