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/* strrchr 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, see
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include <init-arch.h>
/* Define multiple versions only for the definition in libc and for
the DSO. In static binaries we need strrchr before the initialization
happened. */
#if defined SHARED && !defined NOT_IN_libc
.text
ENTRY(strrchr)
.type strrchr, @gnu_indirect_function
cmpl $0, __cpu_features+KIND_OFFSET(%rip)
jne 1f
call __init_cpu_features
1: leaq __strrchr_sse2(%rip), %rax
testl $bit_SSE4_2, __cpu_features+CPUID_OFFSET+index_SSE4_2(%rip)
jz 2f
leaq __strrchr_sse42(%rip), %rax
ret
2: testl $bit_Slow_BSF, __cpu_features+FEATURE_OFFSET+index_Slow_BSF(%rip)
jz 3f
leaq __strrchr_sse2_no_bsf(%rip), %rax
3: ret
END(strrchr)
/*
This implementation uses SSE4 instructions to compare up to 16 bytes
at a time looking for the last occurrence of the character c in the
string s:
char *strrchr (const char *s, int c);
We use 0x4a:
_SIDD_SBYTE_OPS
| _SIDD_CMP_EQUAL_EACH
| _SIDD_MOST_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
last offset. There are 4 cases:
1. The first 16byte data element has EOS and has the byte C at the
last offset X.
2. The first 16byte data element is valid and has the byte C at the
last offset X.
3. The first 16byte data element has EOS and doesn't have the byte C.
4. 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 1 0
2 X 1 0 0
3 16 0 1 0
4 16 0 0 0
We exit from the loop for cases 1 and 3 with jz which branches
when ZFlag is 1. If CFlag == 1, ECX has the offset X for case 1. */
.section .text.sse4.2,"ax",@progbits
.align 16
.type __strrchr_sse42, @function
__strrchr_sse42:
cfi_startproc
CALL_MCOUNT
testb %sil, %sil
je __strend_sse4
xor %eax,%eax /* RAX has the last occurrence of s. */
movd %esi, %xmm1
punpcklbw %xmm1, %xmm1
movl %edi, %esi
punpcklbw %xmm1, %xmm1
andl $15, %esi
pshufd $0, %xmm1, %xmm1
movq %rdi, %r8
je L(loop)
/* Handle unaligned string using psrldq. */
leaq L(psrldq_table)(%rip), %rdx
andq $-16, %r8
movslq (%rdx,%rsi,4),%r9
movdqa (%r8), %xmm0
addq %rdx, %r9
jmp *%r9
/* Handle unaligned string with offset 1 using psrldq. */
.p2align 4
L(psrldq_1):
psrldq $1, %xmm0
.p2align 4
L(unaligned_pcmpistri):
pcmpistri $0x4a, %xmm1, %xmm0
jnc L(unaligned_no_byte)
leaq (%rdi,%rcx), %rax
L(unaligned_no_byte):
/* Find the length of the unaligned string. */
pcmpistri $0x3a, %xmm0, %xmm0
movl $16, %edx
subl %esi, %edx
cmpl %ecx, %edx
/* Return RAX if the unaligned fragment to next 16B already
contain the NULL terminator. */
jg L(exit)
addq $16, %r8
/* Loop start on aligned string. */
.p2align 4
L(loop):
pcmpistri $0x4a, (%r8), %xmm1
jbe L(match_or_eos)
addq $16, %r8
jmp L(loop)
.p2align 4
L(match_or_eos):
je L(had_eos)
L(match_no_eos):
leaq (%r8,%rcx), %rax
addq $16, %r8
jmp L(loop)
.p2align 4
L(had_eos):
jnc L(exit)
leaq (%r8,%rcx), %rax
.p2align 4
L(exit):
ret
/* Handle unaligned string with offset 15 using psrldq. */
.p2align 4
L(psrldq_15):
psrldq $15, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 14 using psrldq. */
.p2align 4
L(psrldq_14):
psrldq $14, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 13 using psrldq. */
.p2align 4
L(psrldq_13):
psrldq $13, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 12 using psrldq. */
.p2align 4
L(psrldq_12):
psrldq $12, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 11 using psrldq. */
.p2align 4
L(psrldq_11):
psrldq $11, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 10 using psrldq. */
.p2align 4
L(psrldq_10):
psrldq $10, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 9 using psrldq. */
.p2align 4
L(psrldq_9):
psrldq $9, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 8 using psrldq. */
.p2align 4
L(psrldq_8):
psrldq $8, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 7 using psrldq. */
.p2align 4
L(psrldq_7):
psrldq $7, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 6 using psrldq. */
.p2align 4
L(psrldq_6):
psrldq $6, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 5 using psrldq. */
.p2align 4
L(psrldq_5):
psrldq $5, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 4 using psrldq. */
.p2align 4
L(psrldq_4):
psrldq $4, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 3 using psrldq. */
.p2align 4
L(psrldq_3):
psrldq $3, %xmm0
jmp L(unaligned_pcmpistri)
/* Handle unaligned string with offset 2 using psrldq. */
.p2align 4
L(psrldq_2):
psrldq $2, %xmm0
jmp L(unaligned_pcmpistri)
cfi_endproc
.size __strrchr_sse42, .-__strrchr_sse42
.section .rodata.sse4.2,"a",@progbits
.p2align 4
L(psrldq_table):
.int L(loop) - L(psrldq_table)
.int L(psrldq_1) - L(psrldq_table)
.int L(psrldq_2) - L(psrldq_table)
.int L(psrldq_3) - L(psrldq_table)
.int L(psrldq_4) - L(psrldq_table)
.int L(psrldq_5) - L(psrldq_table)
.int L(psrldq_6) - L(psrldq_table)
.int L(psrldq_7) - L(psrldq_table)
.int L(psrldq_8) - L(psrldq_table)
.int L(psrldq_9) - L(psrldq_table)
.int L(psrldq_10) - L(psrldq_table)
.int L(psrldq_11) - L(psrldq_table)
.int L(psrldq_12) - L(psrldq_table)
.int L(psrldq_13) - L(psrldq_table)
.int L(psrldq_14) - L(psrldq_table)
.int L(psrldq_15) - L(psrldq_table)
# undef ENTRY
# define ENTRY(name) \
.type __strrchr_sse2, @function; \
.align 16; \
__strrchr_sse2: cfi_startproc; \
CALL_MCOUNT
# undef END
# define END(name) \
cfi_endproc; .size __strrchr_sse2, .-__strrchr_sse2
# undef libc_hidden_builtin_def
/* It doesn't make sense to send libc-internal strrchr 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_strrchr; __GI_strrchr = __strrchr_sse2
#endif
#include "../strrchr.S"
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