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Faster strchr implementation.
This commit is contained in:
Ondřej Bílka
parent
b987c77672
commit
5905e7b3e2
11
ChangeLog
11
ChangeLog
@ -1,3 +1,12 @@
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2013-09-11 Ondřej Bílka <neleai@seznam.cz>
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* sysdeps/x86_64/multiarch/ifunc-impl-list.c
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(__libc_ifunc_impl_list): Remove: __strchr_sse42.
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* sysdeps/x86_64/multiarch/strchr.S (__strchr_sse42): Remove.
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(strchr): Remove __strchr_sse42 ifunc selection.
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* sysdeps/x86_64/strchr.S (strchr): Use optimized implementation.
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* sysdeps/x86_64/strchrnul.S: Include sysdeps/x86_64/strchr.S.
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2013-09-11 Will Newton <will.newton@linaro.org>
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* benchtests/bench-timing.h (TIMING_INIT): Rename ITERS
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@ -35,7 +44,7 @@
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* malloc/malloc.c (__libc_pvalloc): Check the value of bytes
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does not overflow.
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2013-09-10 Ondřej Bílka <neleai@seznam.cz>
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2013-09-10 Ondřej Bílka <neleai@seznam.cz>
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* sysdeps/ieee754/dbl-64/e_j0.c: Remove DO_NOT_USE_THIS conditionals.
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* sysdeps/ieee754/dbl-64/e_j1.c: Likewise.
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@ -110,7 +110,6 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
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/* Support sysdeps/x86_64/multiarch/strchr.S. */
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IFUNC_IMPL (i, name, strchr,
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IFUNC_IMPL_ADD (array, i, strchr, HAS_SSE4_2, __strchr_sse42)
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IFUNC_IMPL_ADD (array, i, strchr, 1, __strchr_sse2_no_bsf)
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IFUNC_IMPL_ADD (array, i, strchr, 1, __strchr_sse2))
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@ -29,12 +29,6 @@ ENTRY(strchr)
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jne 1f
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call __init_cpu_features
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1: leaq __strchr_sse2(%rip), %rax
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testl $bit_Slow_SSE4_2, __cpu_features+CPUID_OFFSET+index_Slow_SSE4_2(%rip)
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jnz 2f
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testl $bit_SSE4_2, __cpu_features+CPUID_OFFSET+index_SSE4_2(%rip)
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jz 2f
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leaq __strchr_sse42(%rip), %rax
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ret
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2: testl $bit_Slow_BSF, __cpu_features+FEATURE_OFFSET+index_Slow_BSF(%rip)
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jz 3f
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leaq __strchr_sse2_no_bsf(%rip), %rax
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@ -42,127 +36,6 @@ ENTRY(strchr)
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END(strchr)
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/*
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This implementation uses SSE4 instructions to compare up to 16 bytes
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at a time looking for the first occurrence of the character c in the
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string s:
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char *strchr (const char *s, int c);
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We use 0xa:
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_SIDD_SBYTE_OPS
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| _SIDD_CMP_EQUAL_EACH
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| _SIDD_LEAST_SIGNIFICANT
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on pcmpistri to compare xmm/mem128
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0 1 2 3 4 5 6 7 8 9 A B C D E F
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X X X X X X X X X X X X X X X X
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against xmm
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0 1 2 3 4 5 6 7 8 9 A B C D E F
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C C C C C C C C C C C C C C C C
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to find out if the first 16byte data element has a byte C and the
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offset of the first byte. There are 3 cases:
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1. The first 16byte data element has the byte C at the offset X.
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2. The first 16byte data element has EOS and doesn't have the byte C.
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3. The first 16byte data element is valid and doesn't have the byte C.
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Here is the table of ECX, CFlag, ZFlag and SFlag for 3 cases:
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case ECX CFlag ZFlag SFlag
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1 X 1 0/1 0
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2 16 0 1 0
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3 16 0 0 0
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We exit from the loop for cases 1 and 2 with jbe which branches
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when either CFlag or ZFlag is 1. If CFlag == 1, ECX has the offset
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X for case 1. */
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.section .text.sse4.2,"ax",@progbits
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.align 16
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.type __strchr_sse42, @function
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.globl __strchr_sse42
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.hidden __strchr_sse42
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__strchr_sse42:
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cfi_startproc
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CALL_MCOUNT
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testb %sil, %sil
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je __strend_sse4
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pxor %xmm2, %xmm2
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movd %esi, %xmm1
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movl %edi, %ecx
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pshufb %xmm2, %xmm1
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andl $15, %ecx
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movq %rdi, %r8
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je L(aligned_start)
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/* Handle unaligned string. */
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andq $-16, %r8
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movdqa (%r8), %xmm0
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pcmpeqb %xmm0, %xmm2
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pcmpeqb %xmm1, %xmm0
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/* Find where NULL is. */
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pmovmskb %xmm2, %edx
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/* Check if there is a match. */
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pmovmskb %xmm0, %esi
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/* Remove the leading bytes. */
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sarl %cl, %edx
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sarl %cl, %esi
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testl %esi, %esi
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je L(unaligned_no_match)
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/* Check which byte is a match. */
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bsfl %esi, %eax
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/* Is there a NULL? */
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testl %edx, %edx
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je L(unaligned_match)
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bsfl %edx, %esi
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cmpl %esi, %eax
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/* Return NULL if NULL comes first. */
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ja L(return_null)
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L(unaligned_match):
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addq %rdi, %rax
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ret
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.p2align 4
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L(unaligned_no_match):
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testl %edx, %edx
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jne L(return_null)
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/* Loop start on aligned string. */
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L(loop):
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addq $16, %r8
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L(aligned_start):
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pcmpistri $0x2, (%r8), %xmm1
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jbe L(wrap)
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addq $16, %r8
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pcmpistri $0x2, (%r8), %xmm1
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jbe L(wrap)
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addq $16, %r8
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pcmpistri $0x2, (%r8), %xmm1
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jbe L(wrap)
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addq $16, %r8
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pcmpistri $0x2, (%r8), %xmm1
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jbe L(wrap)
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jmp L(loop)
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L(wrap):
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jc L(loop_exit)
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/* Return NULL. */
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L(return_null):
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xorl %eax, %eax
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ret
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/* Loop exit. */
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.p2align 4
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L(loop_exit):
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leaq (%r8,%rcx), %rax
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ret
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cfi_endproc
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.size __strchr_sse42, .-__strchr_sse42
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# undef ENTRY
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# define ENTRY(name) \
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@ -19,51 +19,174 @@
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#include <sysdep.h>
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# ifndef ALIGN
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# define ALIGN(n) .p2align n
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# endif
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.text
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ENTRY (strchr)
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movd %esi, %xmm1
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movq %rdi, %rcx
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movl %edi, %eax
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andl $4095, %eax
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punpcklbw %xmm1, %xmm1
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andq $~15, %rdi
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pxor %xmm2, %xmm2
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punpcklbw %xmm1, %xmm1
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orl $0xffffffff, %esi
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movdqa (%rdi), %xmm0
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cmpl $4032, %eax
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punpcklwd %xmm1, %xmm1
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pshufd $0, %xmm1, %xmm1
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subq %rdi, %rcx
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movdqa %xmm0, %xmm3
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leaq 16(%rdi), %rdi
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jg L(cross_page)
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movdqu (%rdi), %xmm0
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pxor %xmm3, %xmm3
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movdqa %xmm0, %xmm4
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pcmpeqb %xmm1, %xmm0
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pcmpeqb %xmm2, %xmm3
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shl %cl, %esi
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pmovmskb %xmm0, %edx
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pmovmskb %xmm3, %ecx
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andl %esi, %edx
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andl %esi, %ecx
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orl %edx, %ecx
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jnz 1f
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pcmpeqb %xmm3, %xmm4
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por %xmm4, %xmm0
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pmovmskb %xmm0, %eax
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test %eax, %eax
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je L(next_48_bytes)
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bsf %eax, %eax
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#ifdef AS_STRCHRNUL
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leaq (%rdi,%rax), %rax
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#else
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movl $0, %edx
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leaq (%rdi,%rax), %rax
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cmpb %sil, (%rax)
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cmovne %rdx, %rax
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#endif
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ret
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2: movdqa (%rdi), %xmm0
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leaq 16(%rdi), %rdi
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movdqa %xmm0, %xmm3
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ALIGN(3)
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L(next_48_bytes):
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movdqu 16(%rdi), %xmm0
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movdqa %xmm0, %xmm4
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pcmpeqb %xmm1, %xmm0
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pcmpeqb %xmm2, %xmm3
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pmovmskb %xmm0, %edx
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pmovmskb %xmm3, %ecx
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orl %edx, %ecx
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jz 2b
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pcmpeqb %xmm3, %xmm4
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por %xmm4, %xmm0
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pmovmskb %xmm0, %ecx
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movdqu 32(%rdi), %xmm0
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movdqa %xmm0, %xmm4
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pcmpeqb %xmm1, %xmm0
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salq $16, %rcx
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pcmpeqb %xmm3, %xmm4
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por %xmm4, %xmm0
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pmovmskb %xmm0, %eax
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movdqu 48(%rdi), %xmm0
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pcmpeqb %xmm0, %xmm3
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salq $32, %rax
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pcmpeqb %xmm1, %xmm0
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orq %rcx, %rax
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por %xmm3, %xmm0
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pmovmskb %xmm0, %ecx
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salq $48, %rcx
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orq %rcx, %rax
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testq %rax, %rax
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jne L(return)
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L(loop_start):
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/* We use this alignment to force loop be aligned to 8 but not
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16 bytes. This gives better sheduling on AMD processors. */
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ALIGN(4)
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pxor %xmm6, %xmm6
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andq $-64, %rdi
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ALIGN(3)
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L(loop64):
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addq $64, %rdi
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movdqa (%rdi), %xmm5
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movdqa 16(%rdi), %xmm2
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movdqa 32(%rdi), %xmm3
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pxor %xmm1, %xmm5
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movdqa 48(%rdi), %xmm4
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pxor %xmm1, %xmm2
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pxor %xmm1, %xmm3
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pminub (%rdi), %xmm5
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pxor %xmm1, %xmm4
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pminub 16(%rdi), %xmm2
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pminub 32(%rdi), %xmm3
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pminub %xmm2, %xmm5
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pminub 48(%rdi), %xmm4
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pminub %xmm3, %xmm5
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pminub %xmm4, %xmm5
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pcmpeqb %xmm6, %xmm5
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pmovmskb %xmm5, %eax
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testl %eax, %eax
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je L(loop64)
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movdqa (%rdi), %xmm5
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movdqa %xmm5, %xmm0
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pcmpeqb %xmm1, %xmm5
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pcmpeqb %xmm6, %xmm0
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por %xmm0, %xmm5
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pcmpeqb %xmm6, %xmm2
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pcmpeqb %xmm6, %xmm3
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pcmpeqb %xmm6, %xmm4
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pmovmskb %xmm5, %ecx
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pmovmskb %xmm2, %eax
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salq $16, %rax
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pmovmskb %xmm3, %r8d
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pmovmskb %xmm4, %edx
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salq $32, %r8
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orq %r8, %rax
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orq %rcx, %rax
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salq $48, %rdx
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orq %rdx, %rax
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ALIGN(3)
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L(return):
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bsfq %rax, %rax
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#ifdef AS_STRCHRNUL
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leaq (%rdi,%rax), %rax
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#else
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movl $0, %edx
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leaq (%rdi,%rax), %rax
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cmpb %sil, (%rax)
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cmovne %rdx, %rax
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#endif
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ret
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ALIGN(4)
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L(cross_page):
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movq %rdi, %rdx
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pxor %xmm2, %xmm2
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andq $-64, %rdx
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movdqa %xmm1, %xmm0
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movdqa (%rdx), %xmm3
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movdqa %xmm3, %xmm4
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pcmpeqb %xmm1, %xmm3
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pcmpeqb %xmm2, %xmm4
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por %xmm4, %xmm3
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pmovmskb %xmm3, %r8d
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movdqa 16(%rdx), %xmm3
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movdqa %xmm3, %xmm4
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pcmpeqb %xmm1, %xmm3
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pcmpeqb %xmm2, %xmm4
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por %xmm4, %xmm3
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pmovmskb %xmm3, %eax
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movdqa 32(%rdx), %xmm3
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movdqa %xmm3, %xmm4
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pcmpeqb %xmm1, %xmm3
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salq $16, %rax
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pcmpeqb %xmm2, %xmm4
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por %xmm4, %xmm3
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pmovmskb %xmm3, %r9d
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movdqa 48(%rdx), %xmm3
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pcmpeqb %xmm3, %xmm2
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salq $32, %r9
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pcmpeqb %xmm3, %xmm0
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orq %r9, %rax
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orq %r8, %rax
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por %xmm2, %xmm0
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pmovmskb %xmm0, %ecx
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salq $48, %rcx
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orq %rcx, %rax
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movl %edi, %ecx
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subb %dl, %cl
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shrq %cl, %rax
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testq %rax, %rax
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jne L(return)
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jmp L(loop_start)
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1: bsfl %edx, %edx
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jz 4f
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bsfl %ecx, %ecx
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leaq -16(%rdi,%rdx), %rax
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cmpl %edx, %ecx
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je 5f
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4: xorl %eax, %eax
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5: ret
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END (strchr)
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#ifndef AS_STRCHRNUL
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weak_alias (strchr, index)
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libc_hidden_builtin_def (strchr)
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#endif
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@ -20,43 +20,8 @@
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#include <sysdep.h>
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.text
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ENTRY (__strchrnul)
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movd %esi, %xmm1
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movq %rdi, %rcx
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punpcklbw %xmm1, %xmm1
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andq $~15, %rdi
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pxor %xmm2, %xmm2
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punpcklbw %xmm1, %xmm1
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orl $0xffffffff, %esi
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movdqa (%rdi), %xmm0
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pshufd $0, %xmm1, %xmm1
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subq %rdi, %rcx
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movdqa %xmm0, %xmm3
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leaq 16(%rdi), %rdi
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pcmpeqb %xmm1, %xmm0
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pcmpeqb %xmm2, %xmm3
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shl %cl, %esi
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pmovmskb %xmm0, %edx
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pmovmskb %xmm3, %ecx
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orl %edx, %ecx
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andl %esi, %ecx
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jnz 1f
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2: movdqa (%rdi), %xmm0
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leaq 16(%rdi), %rdi
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movdqa %xmm0, %xmm3
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pcmpeqb %xmm1, %xmm0
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pcmpeqb %xmm2, %xmm3
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pmovmskb %xmm0, %edx
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pmovmskb %xmm3, %ecx
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orl %edx, %ecx
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jz 2b
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1: bsfl %ecx, %edx
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leaq -16(%rdi,%rdx), %rax
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ret
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END (__strchrnul)
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#define strchr __strchrnul
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#define AS_STRCHRNUL
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#include "strchr.S"
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weak_alias (__strchrnul, strchrnul)
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