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

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.

diff --git a/sysdeps/x86_64/memcmp.S b/sysdeps/x86_64/memcmp.S
index b53f2c0..c245383 100644 (file)
--- a/sysdeps/x86_64/memcmp.S
+++ b/sysdeps/x86_64/memcmp.S
@@ -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):