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533 lines
14 KiB
533 lines
14 KiB
From 7f3e7c262cab4e2401e4331a6ef29c428de02044 Mon Sep 17 00:00:00 2001
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From: Noah Goldstein <goldstein.w.n@gmail.com>
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Date: Fri, 23 Apr 2021 15:56:25 -0400
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Subject: [PATCH] x86: Optimize strchr-evex.S
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Content-type: text/plain; charset=UTF-8
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No bug. This commit optimizes strchr-evex.S. The optimizations are
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mostly small things such as save an ALU in the alignment process,
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saving a few instructions in the loop return. The one significant
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change is saving 2 instructions in the 4x loop. test-strchr,
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test-strchrnul, test-wcschr, and test-wcschrnul are all passing.
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Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
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---
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sysdeps/x86_64/multiarch/strchr-evex.S | 392 ++++++++++++++-----------
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1 file changed, 218 insertions(+), 174 deletions(-)
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diff --git a/sysdeps/x86_64/multiarch/strchr-evex.S b/sysdeps/x86_64/multiarch/strchr-evex.S
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index ddc86a70..7f9d4ee4 100644
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--- a/sysdeps/x86_64/multiarch/strchr-evex.S
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+++ b/sysdeps/x86_64/multiarch/strchr-evex.S
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@@ -32,13 +32,15 @@
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# define VPCMP vpcmpd
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# define VPMINU vpminud
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# define CHAR_REG esi
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-# define SHIFT_REG r8d
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+# define SHIFT_REG ecx
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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 VPCMP vpcmpb
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# define VPMINU vpminub
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# define CHAR_REG sil
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-# define SHIFT_REG ecx
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+# define SHIFT_REG edx
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+# define CHAR_SIZE 1
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# endif
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# define XMMZERO xmm16
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@@ -56,23 +58,20 @@
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# define VEC_SIZE 32
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# define PAGE_SIZE 4096
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+# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
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.section .text.evex,"ax",@progbits
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ENTRY (STRCHR)
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- movl %edi, %ecx
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-# ifndef USE_AS_STRCHRNUL
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- xorl %edx, %edx
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-# endif
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-
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/* Broadcast CHAR to YMM0. */
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- VPBROADCAST %esi, %YMM0
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-
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+ VPBROADCAST %esi, %YMM0
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+ movl %edi, %eax
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+ andl $(PAGE_SIZE - 1), %eax
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vpxorq %XMMZERO, %XMMZERO, %XMMZERO
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- /* Check if we cross page boundary with one vector load. */
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- andl $(PAGE_SIZE - 1), %ecx
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- cmpl $(PAGE_SIZE - VEC_SIZE), %ecx
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- ja L(cross_page_boundary)
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+ /* Check if we cross page boundary with one vector load.
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+ Otherwise it is safe to use an unaligned load. */
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+ cmpl $(PAGE_SIZE - VEC_SIZE), %eax
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+ ja L(cross_page_boundary)
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/* Check the first VEC_SIZE bytes. Search for both CHAR and the
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null bytes. */
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@@ -83,251 +82,296 @@ ENTRY (STRCHR)
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VPMINU %YMM2, %YMM1, %YMM2
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/* Each bit in K0 represents a CHAR or a null byte in YMM1. */
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VPCMP $0, %YMMZERO, %YMM2, %k0
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- ktestd %k0, %k0
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- jz L(more_vecs)
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kmovd %k0, %eax
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+ testl %eax, %eax
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+ jz L(aligned_more)
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tzcntl %eax, %eax
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- /* Found CHAR or the null byte. */
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# ifdef USE_AS_WCSCHR
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- /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
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- leaq (%rdi, %rax, 4), %rax
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+ /* NB: Multiply wchar_t count by 4 to get the number of bytes.
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+ */
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+ leaq (%rdi, %rax, CHAR_SIZE), %rax
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# else
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addq %rdi, %rax
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# endif
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# ifndef USE_AS_STRCHRNUL
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- cmp (%rax), %CHAR_REG
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- cmovne %rdx, %rax
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+ /* Found CHAR or the null byte. */
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+ cmp (%rax), %CHAR_REG
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+ jne L(zero)
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# endif
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ret
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- .p2align 4
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-L(more_vecs):
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- /* Align data for aligned loads in the loop. */
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- andq $-VEC_SIZE, %rdi
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-L(aligned_more):
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-
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- /* Check the next 4 * VEC_SIZE. Only one VEC_SIZE at a time
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- since data is only aligned to VEC_SIZE. */
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- VMOVA VEC_SIZE(%rdi), %YMM1
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- addq $VEC_SIZE, %rdi
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-
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- /* Leaves only CHARS matching esi as 0. */
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- vpxorq %YMM1, %YMM0, %YMM2
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- VPMINU %YMM2, %YMM1, %YMM2
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- /* Each bit in K0 represents a CHAR or a null byte in YMM1. */
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- VPCMP $0, %YMMZERO, %YMM2, %k0
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- kmovd %k0, %eax
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- testl %eax, %eax
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- jnz L(first_vec_x0)
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-
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- VMOVA VEC_SIZE(%rdi), %YMM1
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- /* Leaves only CHARS matching esi as 0. */
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- vpxorq %YMM1, %YMM0, %YMM2
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- VPMINU %YMM2, %YMM1, %YMM2
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- /* Each bit in K0 represents a CHAR or a null byte in YMM1. */
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- VPCMP $0, %YMMZERO, %YMM2, %k0
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- kmovd %k0, %eax
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- testl %eax, %eax
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- jnz L(first_vec_x1)
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-
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- VMOVA (VEC_SIZE * 2)(%rdi), %YMM1
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- /* Leaves only CHARS matching esi as 0. */
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- vpxorq %YMM1, %YMM0, %YMM2
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- VPMINU %YMM2, %YMM1, %YMM2
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- /* Each bit in K0 represents a CHAR or a null byte in YMM1. */
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- VPCMP $0, %YMMZERO, %YMM2, %k0
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- kmovd %k0, %eax
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- testl %eax, %eax
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- jnz L(first_vec_x2)
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-
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- VMOVA (VEC_SIZE * 3)(%rdi), %YMM1
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- /* Leaves only CHARS matching esi as 0. */
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- vpxorq %YMM1, %YMM0, %YMM2
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- VPMINU %YMM2, %YMM1, %YMM2
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- /* Each bit in K0 represents a CHAR or a null byte in YMM1. */
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- VPCMP $0, %YMMZERO, %YMM2, %k0
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- ktestd %k0, %k0
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- jz L(prep_loop_4x)
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-
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- kmovd %k0, %eax
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+ /* .p2align 5 helps keep performance more consistent if ENTRY()
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+ alignment % 32 was either 16 or 0. As well this makes the
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+ alignment % 32 of the loop_4x_vec fixed which makes tuning it
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+ easier. */
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+ .p2align 5
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+L(first_vec_x3):
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tzcntl %eax, %eax
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+# ifndef USE_AS_STRCHRNUL
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/* Found CHAR or the null byte. */
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-# ifdef USE_AS_WCSCHR
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- /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
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- leaq (VEC_SIZE * 3)(%rdi, %rax, 4), %rax
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-# else
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- leaq (VEC_SIZE * 3)(%rdi, %rax), %rax
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+ cmp (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %CHAR_REG
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+ jne L(zero)
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# endif
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+ /* NB: Multiply sizeof char type (1 or 4) to get the number of
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+ bytes. */
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+ leaq (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
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+ ret
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+
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# ifndef USE_AS_STRCHRNUL
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- cmp (%rax), %CHAR_REG
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- cmovne %rdx, %rax
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-# endif
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+L(zero):
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+ xorl %eax, %eax
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ret
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+# endif
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.p2align 4
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-L(first_vec_x0):
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+L(first_vec_x4):
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+# ifndef USE_AS_STRCHRNUL
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+ /* Check to see if first match was CHAR (k0) or null (k1). */
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+ kmovd %k0, %eax
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tzcntl %eax, %eax
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- /* Found CHAR or the null byte. */
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-# ifdef USE_AS_WCSCHR
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- /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
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- leaq (%rdi, %rax, 4), %rax
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+ kmovd %k1, %ecx
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+ /* bzhil will not be 0 if first match was null. */
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+ bzhil %eax, %ecx, %ecx
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+ jne L(zero)
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# else
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- addq %rdi, %rax
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-# endif
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-# ifndef USE_AS_STRCHRNUL
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- cmp (%rax), %CHAR_REG
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- cmovne %rdx, %rax
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+ /* Combine CHAR and null matches. */
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+ kord %k0, %k1, %k0
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+ kmovd %k0, %eax
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+ tzcntl %eax, %eax
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# endif
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+ /* NB: Multiply sizeof char type (1 or 4) to get the number of
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+ bytes. */
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+ leaq (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
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ret
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.p2align 4
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L(first_vec_x1):
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tzcntl %eax, %eax
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- /* Found CHAR or the null byte. */
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-# ifdef USE_AS_WCSCHR
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- /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
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- leaq VEC_SIZE(%rdi, %rax, 4), %rax
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-# else
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- leaq VEC_SIZE(%rdi, %rax), %rax
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-# endif
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# ifndef USE_AS_STRCHRNUL
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- cmp (%rax), %CHAR_REG
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- cmovne %rdx, %rax
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+ /* Found CHAR or the null byte. */
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+ cmp (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %CHAR_REG
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+ jne L(zero)
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+
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# endif
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+ /* NB: Multiply sizeof char type (1 or 4) to get the number of
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+ bytes. */
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+ leaq (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %rax
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ret
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.p2align 4
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L(first_vec_x2):
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+# ifndef USE_AS_STRCHRNUL
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+ /* Check to see if first match was CHAR (k0) or null (k1). */
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+ kmovd %k0, %eax
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tzcntl %eax, %eax
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- /* Found CHAR or the null byte. */
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-# ifdef USE_AS_WCSCHR
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- /* NB: Multiply wchar_t count by 4 to get the number of bytes. */
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- leaq (VEC_SIZE * 2)(%rdi, %rax, 4), %rax
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+ kmovd %k1, %ecx
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+ /* bzhil will not be 0 if first match was null. */
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+ bzhil %eax, %ecx, %ecx
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+ jne L(zero)
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# else
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- leaq (VEC_SIZE * 2)(%rdi, %rax), %rax
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-# endif
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-# ifndef USE_AS_STRCHRNUL
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- cmp (%rax), %CHAR_REG
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- cmovne %rdx, %rax
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+ /* Combine CHAR and null matches. */
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+ kord %k0, %k1, %k0
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+ kmovd %k0, %eax
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+ tzcntl %eax, %eax
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# endif
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+ /* NB: Multiply sizeof char type (1 or 4) to get the number of
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+ bytes. */
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+ leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
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ret
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-L(prep_loop_4x):
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- /* Align data to 4 * VEC_SIZE. */
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+ .p2align 4
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+L(aligned_more):
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+ /* Align data to VEC_SIZE. */
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+ andq $-VEC_SIZE, %rdi
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+L(cross_page_continue):
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+ /* Check the next 4 * VEC_SIZE. Only one VEC_SIZE at a time since
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+ data is only aligned to VEC_SIZE. Use two alternating methods
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+ for checking VEC to balance latency and port contention. */
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+
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+ /* This method has higher latency but has better port
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+ distribution. */
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+ VMOVA (VEC_SIZE)(%rdi), %YMM1
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+ /* Leaves only CHARS matching esi as 0. */
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+ vpxorq %YMM1, %YMM0, %YMM2
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+ VPMINU %YMM2, %YMM1, %YMM2
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+ /* Each bit in K0 represents a CHAR or a null byte in YMM1. */
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+ VPCMP $0, %YMMZERO, %YMM2, %k0
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+ kmovd %k0, %eax
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+ testl %eax, %eax
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+ jnz L(first_vec_x1)
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+
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+ /* This method has higher latency but has better port
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+ distribution. */
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+ VMOVA (VEC_SIZE * 2)(%rdi), %YMM1
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+ /* Each bit in K0 represents a CHAR in YMM1. */
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+ VPCMP $0, %YMM1, %YMM0, %k0
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+ /* Each bit in K1 represents a CHAR in YMM1. */
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+ VPCMP $0, %YMM1, %YMMZERO, %k1
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+ kortestd %k0, %k1
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+ jnz L(first_vec_x2)
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+
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+ VMOVA (VEC_SIZE * 3)(%rdi), %YMM1
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+ /* Leaves only CHARS matching esi as 0. */
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+ vpxorq %YMM1, %YMM0, %YMM2
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+ VPMINU %YMM2, %YMM1, %YMM2
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+ /* Each bit in K0 represents a CHAR or a null byte in YMM1. */
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+ VPCMP $0, %YMMZERO, %YMM2, %k0
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+ kmovd %k0, %eax
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+ testl %eax, %eax
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+ jnz L(first_vec_x3)
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+
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+ VMOVA (VEC_SIZE * 4)(%rdi), %YMM1
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+ /* Each bit in K0 represents a CHAR in YMM1. */
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+ VPCMP $0, %YMM1, %YMM0, %k0
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+ /* Each bit in K1 represents a CHAR in YMM1. */
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+ VPCMP $0, %YMM1, %YMMZERO, %k1
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+ kortestd %k0, %k1
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+ jnz L(first_vec_x4)
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+
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+ /* Align data to VEC_SIZE * 4 for the loop. */
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+ addq $VEC_SIZE, %rdi
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andq $-(VEC_SIZE * 4), %rdi
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.p2align 4
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L(loop_4x_vec):
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- /* Compare 4 * VEC at a time forward. */
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+ /* Check 4x VEC at a time. No penalty to imm32 offset with evex
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+ encoding. */
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VMOVA (VEC_SIZE * 4)(%rdi), %YMM1
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VMOVA (VEC_SIZE * 5)(%rdi), %YMM2
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VMOVA (VEC_SIZE * 6)(%rdi), %YMM3
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VMOVA (VEC_SIZE * 7)(%rdi), %YMM4
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- /* Leaves only CHARS matching esi as 0. */
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+ /* For YMM1 and YMM3 use xor to set the CHARs matching esi to
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+ zero. */
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vpxorq %YMM1, %YMM0, %YMM5
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- vpxorq %YMM2, %YMM0, %YMM6
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+ /* For YMM2 and YMM4 cmp not equals to CHAR and store result in
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+ k register. Its possible to save either 1 or 2 instructions
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+ using cmp no equals method for either YMM1 or YMM1 and YMM3
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+ respectively but bottleneck on p5 makes it not worth it. */
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+ VPCMP $4, %YMM0, %YMM2, %k2
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vpxorq %YMM3, %YMM0, %YMM7
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- vpxorq %YMM4, %YMM0, %YMM8
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-
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- VPMINU %YMM5, %YMM1, %YMM5
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- VPMINU %YMM6, %YMM2, %YMM6
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- VPMINU %YMM7, %YMM3, %YMM7
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- VPMINU %YMM8, %YMM4, %YMM8
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-
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- VPMINU %YMM5, %YMM6, %YMM1
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- VPMINU %YMM7, %YMM8, %YMM2
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-
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- VPMINU %YMM1, %YMM2, %YMM1
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-
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- /* Each bit in K0 represents a CHAR or a null byte. */
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- VPCMP $0, %YMMZERO, %YMM1, %k0
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-
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- addq $(VEC_SIZE * 4), %rdi
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-
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- ktestd %k0, %k0
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+ VPCMP $4, %YMM0, %YMM4, %k4
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+
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+ /* Use min to select all zeros from either xor or end of string).
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+ */
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+ VPMINU %YMM1, %YMM5, %YMM1
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+ VPMINU %YMM3, %YMM7, %YMM3
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+
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+ /* Use min + zeromask to select for zeros. Since k2 and k4 will
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+ have 0 as positions that matched with CHAR which will set
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+ zero in the corresponding destination bytes in YMM2 / YMM4.
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+ */
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+ VPMINU %YMM1, %YMM2, %YMM2{%k2}{z}
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+ VPMINU %YMM3, %YMM4, %YMM4
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+ VPMINU %YMM2, %YMM4, %YMM4{%k4}{z}
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+
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+ VPCMP $0, %YMMZERO, %YMM4, %k1
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+ kmovd %k1, %ecx
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+ subq $-(VEC_SIZE * 4), %rdi
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+ testl %ecx, %ecx
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jz L(loop_4x_vec)
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- /* Each bit in K0 represents a CHAR or a null byte in YMM1. */
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- VPCMP $0, %YMMZERO, %YMM5, %k0
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+ VPCMP $0, %YMMZERO, %YMM1, %k0
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kmovd %k0, %eax
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testl %eax, %eax
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- jnz L(first_vec_x0)
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+ jnz L(last_vec_x1)
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- /* Each bit in K1 represents a CHAR or a null byte in YMM2. */
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- VPCMP $0, %YMMZERO, %YMM6, %k1
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- kmovd %k1, %eax
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+ VPCMP $0, %YMMZERO, %YMM2, %k0
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+ kmovd %k0, %eax
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testl %eax, %eax
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- jnz L(first_vec_x1)
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-
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- /* Each bit in K2 represents a CHAR or a null byte in YMM3. */
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- VPCMP $0, %YMMZERO, %YMM7, %k2
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- /* Each bit in K3 represents a CHAR or a null byte in YMM4. */
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- VPCMP $0, %YMMZERO, %YMM8, %k3
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+ jnz L(last_vec_x2)
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+ VPCMP $0, %YMMZERO, %YMM3, %k0
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+ kmovd %k0, %eax
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+ /* Combine YMM3 matches (eax) with YMM4 matches (ecx). */
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# ifdef USE_AS_WCSCHR
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- /* NB: Each bit in K2/K3 represents 4-byte element. */
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- kshiftlw $8, %k3, %k1
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+ sall $8, %ecx
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+ orl %ecx, %eax
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+ tzcntl %eax, %eax
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# else
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- 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
|
|
|
|
--
|
|
GitLab
|
|
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