502 lines
12 KiB
Diff
502 lines
12 KiB
Diff
From df7e295d18ffa34f629578c0017a9881af7620f6 Mon Sep 17 00:00:00 2001
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From: Noah Goldstein <goldstein.w.n@gmail.com>
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Date: Thu, 21 Apr 2022 20:52:29 -0500
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Subject: [PATCH] x86: Optimize {str|wcs}rchr-avx2
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Content-type: text/plain; charset=UTF-8
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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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---
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sysdeps/x86_64/multiarch/strrchr-avx2.S | 426 +++++++++++++++---------
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1 file changed, 269 insertions(+), 157 deletions(-)
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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 c949410b..3d26fad4 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
|
|
+ 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
|
|
|
|
- .p2align 4
|
|
-L(return_null):
|
|
- xorl %eax, %eax
|
|
+ /* 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
|
|
|
|
-END (STRRCHR)
|
|
+ .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
|
|
--
|
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GitLab
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