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x86_64: Add sse2 optimized __memcmpeq in memcmp-sse2.S

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No bug. This commit does not modify any of the memcmp
implementation. It just adds __memcmpeq ifdefs to skip obvious cases
where computing the proper 1/-1 required by memcmp is not needed.
This commit is contained in:
Noah Goldstein 2021-09-30 15:32:50 -05:00
parent cf4fd28ea4
commit fa7f63d8d6
1 changed files with 51 additions and 4 deletions
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55
sysdeps/x86_64/memcmp.S
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@ -49,34 +49,63 @@ L(s2b):
movzwl (%rdi), %eax
movzwl (%rdi, %rsi), %edx
subq $2, %r10
#ifdef USE_AS_MEMCMPEQ
je L(finz1)
#else
je L(fin2_7)
#endif
addq $2, %rdi
cmpl %edx, %eax
#ifdef USE_AS_MEMCMPEQ
jnz L(neq_early)
#else
jnz L(fin2_7)
#endif
L(s4b):
testq $4, %r10
jz L(s8b)
movl (%rdi), %eax
movl (%rdi, %rsi), %edx
subq $4, %r10
#ifdef USE_AS_MEMCMPEQ
je L(finz1)
#else
je L(fin2_7)
#endif
addq $4, %rdi
cmpl %edx, %eax
#ifdef USE_AS_MEMCMPEQ
jnz L(neq_early)
#else
jnz L(fin2_7)
#endif
L(s8b):
testq $8, %r10
jz L(s16b)
movq (%rdi), %rax
movq (%rdi, %rsi), %rdx
subq $8, %r10
#ifdef USE_AS_MEMCMPEQ
je L(sub_return8)
#else
je L(fin2_7)
#endif
addq $8, %rdi
cmpq %rdx, %rax
#ifdef USE_AS_MEMCMPEQ
jnz L(neq_early)
#else
jnz L(fin2_7)
#endif
L(s16b):
movdqu (%rdi), %xmm1
movdqu (%rdi, %rsi), %xmm0
pcmpeqb %xmm0, %xmm1
#ifdef USE_AS_MEMCMPEQ
pmovmskb %xmm1, %eax
subl $0xffff, %eax
ret
#else
pmovmskb %xmm1, %edx
xorl %eax, %eax
subl $0xffff, %edx
@ -86,7 +115,7 @@ L(s16b):
movzbl (%rcx), %eax
movzbl (%rsi, %rcx), %edx
jmp L(finz1)
#endif
.p2align 4,, 4
L(finr1b):
movzbl (%rdi), %eax
@ -95,7 +124,15 @@ L(finz1):
subl %edx, %eax
L(exit):
ret
#ifdef USE_AS_MEMCMPEQ
.p2align 4,, 4
L(sub_return8):
subq %rdx, %rax
movl %eax, %edx
shrq $32, %rax
orl %edx, %eax
ret
#else
.p2align 4,, 4
L(fin2_7):
cmpq %rdx, %rax
@ -111,12 +148,17 @@ L(fin2_7):
movzbl %dl, %edx
subl %edx, %eax
ret
#endif
.p2align 4,, 4
L(finz):
xorl %eax, %eax
ret
#ifdef USE_AS_MEMCMPEQ
.p2align 4,, 4
L(neq_early):
movl $1, %eax
ret
#endif
/* For blocks bigger than 32 bytes
1. Advance one of the addr pointer to be 16B aligned.
2. Treat the case of both addr pointers aligned to 16B
@ -246,11 +288,16 @@ L(mt16):
.p2align 4,, 4
L(neq):
#ifdef USE_AS_MEMCMPEQ
movl $1, %eax
ret
#else
bsfl %edx, %ecx
movzbl (%rdi, %rcx), %eax
addq %rdi, %rsi
movzbl (%rsi,%rcx), %edx
jmp L(finz1)
#endif
.p2align 4,, 4
L(ATR):