mirror of
git://sourceware.org/git/glibc.git
synced 2024-12-27 04:41:02 +08:00
51ddd2c01e
This patch defines bit_XXX and index_XXX and use them to check processor feature in assembly code. It can prevent typos in processor feature check.
178 lines
4.4 KiB
ArmAsm
178 lines
4.4 KiB
ArmAsm
/* strchr with SSE4.2
|
|
Copyright (C) 2009 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, write to the Free
|
|
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA. */
|
|
|
|
#include <sysdep.h>
|
|
#include <init-arch.h>
|
|
|
|
|
|
/* Define multiple versions only for the definition in libc. */
|
|
#ifndef NOT_IN_libc
|
|
.text
|
|
ENTRY(strchr)
|
|
.type strchr, @gnu_indirect_function
|
|
cmpl $0, __cpu_features+KIND_OFFSET(%rip)
|
|
jne 1f
|
|
call __init_cpu_features
|
|
1: leaq __strchr_sse2(%rip), %rax
|
|
testl $bit_SSE4_2, __cpu_features+CPUID_OFFSET+index_SSE4_2(%rip)
|
|
jz 2f
|
|
leaq __strchr_sse42(%rip), %rax
|
|
2: ret
|
|
END(strchr)
|
|
|
|
|
|
/*
|
|
This implementation uses SSE4 instructions to compare up to 16 bytes
|
|
at a time looking for the first occurrence of the character c in the
|
|
string s:
|
|
|
|
char *strchr (const char *s, int c);
|
|
|
|
We use 0xa:
|
|
_SIDD_SBYTE_OPS
|
|
| _SIDD_CMP_EQUAL_EACH
|
|
| _SIDD_LEAST_SIGNIFICANT
|
|
on pcmpistri to compare xmm/mem128
|
|
|
|
0 1 2 3 4 5 6 7 8 9 A B C D E F
|
|
X X X X X X X X X X X X X X X X
|
|
|
|
against xmm
|
|
|
|
0 1 2 3 4 5 6 7 8 9 A B C D E F
|
|
C C C C C C C C C C C C C C C C
|
|
|
|
to find out if the first 16byte data element has a byte C and the
|
|
offset of the first byte. There are 3 cases:
|
|
|
|
1. The first 16byte data element has the byte C at the offset X.
|
|
2. The first 16byte data element has EOS and doesn't have the byte C.
|
|
3. The first 16byte data element is valid and doesn't have the byte C.
|
|
|
|
Here is the table of ECX, CFlag, ZFlag and SFlag for 3 cases:
|
|
|
|
case ECX CFlag ZFlag SFlag
|
|
1 X 1 0/1 0
|
|
2 16 0 1 0
|
|
3 16 0 0 0
|
|
|
|
We exit from the loop for cases 1 and 2 with jbe which branches
|
|
when either CFlag or ZFlag is 1. If CFlag == 1, ECX has the offset
|
|
X for case 1. */
|
|
|
|
.section .text.sse4.2,"ax",@progbits
|
|
.align 16
|
|
.type __strchr_sse42, @function
|
|
__strchr_sse42:
|
|
cfi_startproc
|
|
CALL_MCOUNT
|
|
testb %sil, %sil
|
|
je __strend_sse4
|
|
pxor %xmm2, %xmm2
|
|
movd %esi, %xmm1
|
|
movl %edi, %ecx
|
|
andl $15, %ecx
|
|
movq %rdi, %r8
|
|
je L(aligned_start)
|
|
|
|
/* Handle unaligned string. */
|
|
andq $-16, %r8
|
|
pshufb %xmm2, %xmm1
|
|
movdqa (%r8), %xmm0
|
|
pcmpeqb %xmm0, %xmm2
|
|
pcmpeqb %xmm1, %xmm0
|
|
/* Find where NULL is. */
|
|
pmovmskb %xmm2, %edx
|
|
/* Check if there is a match. */
|
|
pmovmskb %xmm0, %esi
|
|
/* Remove the leading bytes. */
|
|
sarl %cl, %edx
|
|
sarl %cl, %esi
|
|
testl %esi, %esi
|
|
je L(unaligned_no_match)
|
|
/* Check which byte is a match. */
|
|
bsfl %esi, %eax
|
|
/* Is there a NULL? */
|
|
testl %edx, %edx
|
|
je L(unaligned_match)
|
|
bsfl %edx, %esi
|
|
cmpl %esi, %eax
|
|
/* Return NULL if NULL comes first. */
|
|
ja L(return_null)
|
|
L(unaligned_match):
|
|
addq %rdi, %rax
|
|
ret
|
|
|
|
.p2align 4
|
|
L(unaligned_no_match):
|
|
testl %edx, %edx
|
|
jne L(return_null)
|
|
|
|
/* Loop start on aligned string. */
|
|
L(loop):
|
|
addq $16, %r8
|
|
L(aligned_start):
|
|
pcmpistri $0x2, (%r8), %xmm1
|
|
jbe L(wrap)
|
|
addq $16, %r8
|
|
pcmpistri $0x2, (%r8), %xmm1
|
|
jbe L(wrap)
|
|
addq $16, %r8
|
|
pcmpistri $0x2, (%r8), %xmm1
|
|
jbe L(wrap)
|
|
addq $16, %r8
|
|
pcmpistri $0x2, (%r8), %xmm1
|
|
jbe L(wrap)
|
|
jmp L(loop)
|
|
L(wrap):
|
|
jc L(loop_exit)
|
|
|
|
/* Return NULL. */
|
|
L(return_null):
|
|
xorl %eax, %eax
|
|
ret
|
|
|
|
/* Loop exit. */
|
|
.p2align 4
|
|
L(loop_exit):
|
|
leaq (%r8,%rcx), %rax
|
|
ret
|
|
cfi_endproc
|
|
.size __strchr_sse42, .-__strchr_sse42
|
|
|
|
|
|
# undef ENTRY
|
|
# define ENTRY(name) \
|
|
.type __strchr_sse2, @function; \
|
|
.align 16; \
|
|
__strchr_sse2: cfi_startproc; \
|
|
CALL_MCOUNT
|
|
# undef END
|
|
# define END(name) \
|
|
cfi_endproc; .size __strchr_sse2, .-__strchr_sse2
|
|
# undef libc_hidden_builtin_def
|
|
/* It doesn't make sense to send libc-internal strchr calls through a PLT.
|
|
The speedup we get from using SSE4.2 instruction is likely eaten away
|
|
by the indirect call in the PLT. */
|
|
# define libc_hidden_builtin_def(name) \
|
|
.globl __GI_strchr; __GI_strchr = __strchr_sse2
|
|
#endif
|
|
|
|
#include "../strchr.S"
|