mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-13 06:40:09 +00:00
dd6d3a0bbc
Small code cleanup for size: -81 bytes.
Add comment justifying using a branch to do NULL/non-null return.
All string/memory tests pass and no regressions in benchtests.
geometric_mean(N=20) of all benchmarks New / Original: .985
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit ec285ea904)
394 lines
10 KiB
ArmAsm
394 lines
10 KiB
ArmAsm
/* strchr/strchrnul optimized with 256-bit EVEX instructions.
|
|
Copyright (C) 2021 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#if IS_IN (libc)
|
|
|
|
# include <sysdep.h>
|
|
|
|
# ifndef STRCHR
|
|
# define STRCHR __strchr_evex
|
|
# endif
|
|
|
|
# define VMOVU vmovdqu64
|
|
# define VMOVA vmovdqa64
|
|
|
|
# ifdef USE_AS_WCSCHR
|
|
# define VPBROADCAST vpbroadcastd
|
|
# define VPCMP vpcmpd
|
|
# define VPTESTN vptestnmd
|
|
# define VPMINU vpminud
|
|
# define CHAR_REG esi
|
|
# define SHIFT_REG ecx
|
|
# define CHAR_SIZE 4
|
|
# else
|
|
# define VPBROADCAST vpbroadcastb
|
|
# define VPCMP vpcmpb
|
|
# define VPTESTN vptestnmb
|
|
# define VPMINU vpminub
|
|
# define CHAR_REG sil
|
|
# define SHIFT_REG edx
|
|
# define CHAR_SIZE 1
|
|
# endif
|
|
|
|
# define XMMZERO xmm16
|
|
|
|
# define YMMZERO ymm16
|
|
# define YMM0 ymm17
|
|
# define YMM1 ymm18
|
|
# define YMM2 ymm19
|
|
# define YMM3 ymm20
|
|
# define YMM4 ymm21
|
|
# define YMM5 ymm22
|
|
# define YMM6 ymm23
|
|
# define YMM7 ymm24
|
|
# define YMM8 ymm25
|
|
|
|
# define VEC_SIZE 32
|
|
# define PAGE_SIZE 4096
|
|
# define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE)
|
|
|
|
.section .text.evex,"ax",@progbits
|
|
ENTRY_P2ALIGN (STRCHR, 5)
|
|
/* Broadcast CHAR to YMM0. */
|
|
VPBROADCAST %esi, %YMM0
|
|
movl %edi, %eax
|
|
andl $(PAGE_SIZE - 1), %eax
|
|
/* Check if we cross page boundary with one vector load.
|
|
Otherwise it is safe to use an unaligned load. */
|
|
cmpl $(PAGE_SIZE - VEC_SIZE), %eax
|
|
ja L(cross_page_boundary)
|
|
|
|
/* Check the first VEC_SIZE bytes. Search for both CHAR and the
|
|
null bytes. */
|
|
VMOVU (%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. */
|
|
VPTESTN %YMM2, %YMM2, %k0
|
|
kmovd %k0, %eax
|
|
testl %eax, %eax
|
|
jz L(aligned_more)
|
|
tzcntl %eax, %eax
|
|
# ifndef USE_AS_STRCHRNUL
|
|
/* Found CHAR or the null byte. */
|
|
cmp (%rdi, %rax, CHAR_SIZE), %CHAR_REG
|
|
/* NB: Use a branch instead of cmovcc here. The expectation is
|
|
that with strchr the user will branch based on input being
|
|
null. Since this branch will be 100% predictive of the user
|
|
branch a branch miss here should save what otherwise would
|
|
be branch miss in the user code. Otherwise using a branch 1)
|
|
saves code size and 2) is faster in highly predictable
|
|
environments. */
|
|
jne L(zero)
|
|
# endif
|
|
# ifdef USE_AS_WCSCHR
|
|
/* NB: Multiply wchar_t count by 4 to get the number of bytes.
|
|
*/
|
|
leaq (%rdi, %rax, CHAR_SIZE), %rax
|
|
# else
|
|
addq %rdi, %rax
|
|
# endif
|
|
ret
|
|
|
|
|
|
|
|
.p2align 4,, 10
|
|
L(first_vec_x4):
|
|
# ifndef USE_AS_STRCHRNUL
|
|
/* Check to see if first match was CHAR (k0) or null (k1). */
|
|
kmovd %k0, %eax
|
|
tzcntl %eax, %eax
|
|
kmovd %k1, %ecx
|
|
/* bzhil will not be 0 if first match was null. */
|
|
bzhil %eax, %ecx, %ecx
|
|
jne L(zero)
|
|
# else
|
|
/* Combine CHAR and null matches. */
|
|
kord %k0, %k1, %k0
|
|
kmovd %k0, %eax
|
|
tzcntl %eax, %eax
|
|
# endif
|
|
/* NB: Multiply sizeof char type (1 or 4) to get the number of
|
|
bytes. */
|
|
leaq (VEC_SIZE * 4)(%rdi, %rax, CHAR_SIZE), %rax
|
|
ret
|
|
|
|
# ifndef USE_AS_STRCHRNUL
|
|
L(zero):
|
|
xorl %eax, %eax
|
|
ret
|
|
# endif
|
|
|
|
|
|
.p2align 4
|
|
L(first_vec_x1):
|
|
/* Use bsf here to save 1-byte keeping keeping the block in 1x
|
|
fetch block. eax guranteed non-zero. */
|
|
bsfl %eax, %eax
|
|
# ifndef USE_AS_STRCHRNUL
|
|
/* Found CHAR or the null byte. */
|
|
cmp (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %CHAR_REG
|
|
jne L(zero)
|
|
|
|
# endif
|
|
/* NB: Multiply sizeof char type (1 or 4) to get the number of
|
|
bytes. */
|
|
leaq (VEC_SIZE)(%rdi, %rax, CHAR_SIZE), %rax
|
|
ret
|
|
|
|
.p2align 4,, 10
|
|
L(first_vec_x2):
|
|
# ifndef USE_AS_STRCHRNUL
|
|
/* Check to see if first match was CHAR (k0) or null (k1). */
|
|
kmovd %k0, %eax
|
|
tzcntl %eax, %eax
|
|
kmovd %k1, %ecx
|
|
/* bzhil will not be 0 if first match was null. */
|
|
bzhil %eax, %ecx, %ecx
|
|
jne L(zero)
|
|
# else
|
|
/* Combine CHAR and null matches. */
|
|
kord %k0, %k1, %k0
|
|
kmovd %k0, %eax
|
|
tzcntl %eax, %eax
|
|
# endif
|
|
/* NB: Multiply sizeof char type (1 or 4) to get the number of
|
|
bytes. */
|
|
leaq (VEC_SIZE * 2)(%rdi, %rax, CHAR_SIZE), %rax
|
|
ret
|
|
|
|
.p2align 4,, 10
|
|
L(first_vec_x3):
|
|
/* Use bsf here to save 1-byte keeping keeping the block in 1x
|
|
fetch block. eax guranteed non-zero. */
|
|
bsfl %eax, %eax
|
|
# ifndef USE_AS_STRCHRNUL
|
|
/* Found CHAR or the null byte. */
|
|
cmp (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %CHAR_REG
|
|
jne L(zero)
|
|
# endif
|
|
/* NB: Multiply sizeof char type (1 or 4) to get the number of
|
|
bytes. */
|
|
leaq (VEC_SIZE * 3)(%rdi, %rax, CHAR_SIZE), %rax
|
|
ret
|
|
|
|
.p2align 4
|
|
L(aligned_more):
|
|
/* Align data to VEC_SIZE. */
|
|
andq $-VEC_SIZE, %rdi
|
|
L(cross_page_continue):
|
|
/* Check the next 4 * VEC_SIZE. Only one VEC_SIZE at a time since
|
|
data is only aligned to VEC_SIZE. Use two alternating methods
|
|
for checking VEC to balance latency and port contention. */
|
|
|
|
/* This method has higher latency but has better port
|
|
distribution. */
|
|
VMOVA (VEC_SIZE)(%rdi), %YMM1
|
|
/* Leaves only CHARS matching esi as 0. */
|
|
vpxorq %YMM1, %YMM0, %YMM2
|
|
VPMINU %YMM2, %YMM1, %YMM2
|
|
/* Each bit in K0 represents a CHAR or a null byte in YMM1. */
|
|
VPTESTN %YMM2, %YMM2, %k0
|
|
kmovd %k0, %eax
|
|
testl %eax, %eax
|
|
jnz L(first_vec_x1)
|
|
|
|
/* This method has higher latency but has better port
|
|
distribution. */
|
|
VMOVA (VEC_SIZE * 2)(%rdi), %YMM1
|
|
/* Each bit in K0 represents a CHAR in YMM1. */
|
|
VPCMP $0, %YMM1, %YMM0, %k0
|
|
/* Each bit in K1 represents a CHAR in YMM1. */
|
|
VPTESTN %YMM1, %YMM1, %k1
|
|
kortestd %k0, %k1
|
|
jnz L(first_vec_x2)
|
|
|
|
VMOVA (VEC_SIZE * 3)(%rdi), %YMM1
|
|
/* Leaves only CHARS matching esi as 0. */
|
|
vpxorq %YMM1, %YMM0, %YMM2
|
|
VPMINU %YMM2, %YMM1, %YMM2
|
|
/* Each bit in K0 represents a CHAR or a null byte in YMM1. */
|
|
VPTESTN %YMM2, %YMM2, %k0
|
|
kmovd %k0, %eax
|
|
testl %eax, %eax
|
|
jnz L(first_vec_x3)
|
|
|
|
VMOVA (VEC_SIZE * 4)(%rdi), %YMM1
|
|
/* Each bit in K0 represents a CHAR in YMM1. */
|
|
VPCMP $0, %YMM1, %YMM0, %k0
|
|
/* Each bit in K1 represents a CHAR in YMM1. */
|
|
VPTESTN %YMM1, %YMM1, %k1
|
|
kortestd %k0, %k1
|
|
jnz L(first_vec_x4)
|
|
|
|
/* Align data to VEC_SIZE * 4 for the loop. */
|
|
addq $VEC_SIZE, %rdi
|
|
andq $-(VEC_SIZE * 4), %rdi
|
|
|
|
.p2align 4
|
|
L(loop_4x_vec):
|
|
/* Check 4x VEC at a time. No penalty to imm32 offset with evex
|
|
encoding. */
|
|
VMOVA (VEC_SIZE * 4)(%rdi), %YMM1
|
|
VMOVA (VEC_SIZE * 5)(%rdi), %YMM2
|
|
VMOVA (VEC_SIZE * 6)(%rdi), %YMM3
|
|
VMOVA (VEC_SIZE * 7)(%rdi), %YMM4
|
|
|
|
/* For YMM1 and YMM3 use xor to set the CHARs matching esi to
|
|
zero. */
|
|
vpxorq %YMM1, %YMM0, %YMM5
|
|
/* For YMM2 and YMM4 cmp not equals to CHAR and store result in
|
|
k register. Its possible to save either 1 or 2 instructions
|
|
using cmp no equals method for either YMM1 or YMM1 and YMM3
|
|
respectively but bottleneck on p5 makes it not worth it. */
|
|
VPCMP $4, %YMM0, %YMM2, %k2
|
|
vpxorq %YMM3, %YMM0, %YMM7
|
|
VPCMP $4, %YMM0, %YMM4, %k4
|
|
|
|
/* Use min to select all zeros from either xor or end of string).
|
|
*/
|
|
VPMINU %YMM1, %YMM5, %YMM1
|
|
VPMINU %YMM3, %YMM7, %YMM3
|
|
|
|
/* Use min + zeromask to select for zeros. Since k2 and k4 will
|
|
have 0 as positions that matched with CHAR which will set
|
|
zero in the corresponding destination bytes in YMM2 / YMM4.
|
|
*/
|
|
VPMINU %YMM1, %YMM2, %YMM2{%k2}{z}
|
|
VPMINU %YMM3, %YMM4, %YMM4
|
|
VPMINU %YMM2, %YMM4, %YMM4{%k4}{z}
|
|
|
|
VPTESTN %YMM4, %YMM4, %k1
|
|
kmovd %k1, %ecx
|
|
subq $-(VEC_SIZE * 4), %rdi
|
|
testl %ecx, %ecx
|
|
jz L(loop_4x_vec)
|
|
|
|
VPTESTN %YMM1, %YMM1, %k0
|
|
kmovd %k0, %eax
|
|
testl %eax, %eax
|
|
jnz L(last_vec_x1)
|
|
|
|
VPTESTN %YMM2, %YMM2, %k0
|
|
kmovd %k0, %eax
|
|
testl %eax, %eax
|
|
jnz L(last_vec_x2)
|
|
|
|
VPTESTN %YMM3, %YMM3, %k0
|
|
kmovd %k0, %eax
|
|
/* Combine YMM3 matches (eax) with YMM4 matches (ecx). */
|
|
# ifdef USE_AS_WCSCHR
|
|
sall $8, %ecx
|
|
orl %ecx, %eax
|
|
bsfl %eax, %eax
|
|
# else
|
|
salq $32, %rcx
|
|
orq %rcx, %rax
|
|
bsfq %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
|
|
|
|
.p2align 4,, 8
|
|
L(last_vec_x1):
|
|
bsfl %eax, %eax
|
|
# ifdef USE_AS_WCSCHR
|
|
/* NB: Multiply wchar_t count by 4 to get the number of bytes.
|
|
*/
|
|
leaq (%rdi, %rax, CHAR_SIZE), %rax
|
|
# else
|
|
addq %rdi, %rax
|
|
# endif
|
|
|
|
# ifndef USE_AS_STRCHRNUL
|
|
/* Check if match was null. */
|
|
cmp (%rax), %CHAR_REG
|
|
jne L(zero_end)
|
|
# endif
|
|
|
|
ret
|
|
|
|
.p2align 4,, 8
|
|
L(last_vec_x2):
|
|
bsfl %eax, %eax
|
|
# ifndef USE_AS_STRCHRNUL
|
|
/* 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,, 8
|
|
L(cross_page_boundary):
|
|
movq %rdi, %rdx
|
|
/* Align rdi. */
|
|
andq $-VEC_SIZE, %rdi
|
|
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. */
|
|
VPTESTN %YMM2, %YMM2, %k0
|
|
kmovd %k0, %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. */
|
|
sarl $2, %SHIFT_REG
|
|
andl $(CHAR_PER_VEC - 1), %SHIFT_REG
|
|
# endif
|
|
sarxl %SHIFT_REG, %eax, %eax
|
|
/* If eax is zero continue. */
|
|
testl %eax, %eax
|
|
jz L(cross_page_continue)
|
|
bsfl %eax, %eax
|
|
|
|
# ifdef USE_AS_WCSCHR
|
|
/* NB: Multiply wchar_t count by 4 to get the number of
|
|
bytes. */
|
|
leaq (%rdx, %rax, CHAR_SIZE), %rax
|
|
# else
|
|
addq %rdx, %rax
|
|
# endif
|
|
# ifndef USE_AS_STRCHRNUL
|
|
/* Check to see if match was CHAR or null. */
|
|
cmp (%rax), %CHAR_REG
|
|
je L(cross_page_ret)
|
|
L(zero_end):
|
|
xorl %eax, %eax
|
|
L(cross_page_ret):
|
|
# endif
|
|
ret
|
|
|
|
END (STRCHR)
|
|
#endif
|