x86_64: Remove redundant REX bytes from memrchr.S

By x86-64 specification, 32-bit destination registers are zero-extended
to 64 bits.  There is no need to use 64-bit registers when only the lower
32 bits are non-zero.  Also 2 instructions in:

	mov	%rdi, %rcx
	and	$15, %rcx
	jz	L(length_less16_offset0)

	mov	%rdi, %rcx		<<< redundant
	and	$15, %rcx		<<< redundant

are redundant.

	* sysdeps/x86_64/memrchr.S (__memrchr): Use 32-bit registers for
	the lower 32 bits.  Remove redundant instructions.

diff --git a/ChangeLog b/ChangeLog
index 1cbcf564e0bea7efcc9af08fa15c157a98852cf4..1549eb64226026b59dd2c014f3221faa2e89feae 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-06-05  H.J. Lu  <hongjiu.lu@intel.com>
+
+       * sysdeps/x86_64/memrchr.S (__memrchr): Use 32-bit registers for
+       the lower 32 bits.  Remove redundant instructions.
+
 2017-06-05  H.J. Lu  <hongjiu.lu@intel.com>
 
        * sysdeps/unix/sysv/linux/x86_64/sysdep.h (LO_HI_LONG): Pass

diff --git a/sysdeps/x86_64/memrchr.S b/sysdeps/x86_64/memrchr.S
index aab1a4a0c4b8ed2ee82eb0c0d39f881146bece30..5fa0fe9c1c5e42acae02b58fc1c42f0b1041fdcd 100644 (file)
--- a/sysdeps/x86_64/memrchr.S
+++ b/sysdeps/x86_64/memrchr.S
@@ -22,7 +22,7 @@
 
        .text
 ENTRY (__memrchr)
-       movd    %rsi, %xmm1
+       movd    %esi, %xmm1
 
        sub     $16, %rdx
        jbe     L(length_less16)
@@ -42,8 +42,8 @@ ENTRY (__memrchr)
        jnz     L(matches0)
 
        sub     $64, %rdi
-       mov     %rdi, %rcx
-       and     $15, %rcx
+       mov     %edi, %ecx
+       and     $15, %ecx
        jz      L(loop_prolog)
 
        add     $16, %rdi
@@ -108,8 +108,8 @@ L(loop_prolog):
        test    %eax, %eax
        jnz     L(matches0)
 
-       mov     %rdi, %rcx
-       and     $63, %rcx
+       mov     %edi, %ecx
+       and     $63, %ecx
        jz      L(align64_loop)
 
        add     $64, %rdi
@@ -166,8 +166,8 @@ L(align64_loop):
 
        .p2align 4
 L(exit_loop):
-       add     $64, %rdx
-       cmp     $32, %rdx
+       add     $64, %edx
+       cmp     $32, %edx
        jbe     L(exit_loop_32)
 
        movdqa  48(%rdi), %xmm0
@@ -187,7 +187,7 @@ L(exit_loop):
        pmovmskb        %xmm3, %eax
        test    %eax, %eax
        jnz     L(matches16_1)
-       cmp     $48, %rdx
+       cmp     $48, %edx
        jbe     L(return_null)
 
        pcmpeqb (%rdi), %xmm1
@@ -204,7 +204,7 @@ L(exit_loop_32):
        pmovmskb        %xmm0, %eax
        test    %eax, %eax
        jnz     L(matches48_1)
-       cmp     $16, %rdx
+       cmp     $16, %edx
        jbe     L(return_null)
 
        pcmpeqb 32(%rdi), %xmm1
@@ -276,7 +276,7 @@ L(matches48_1):
 
        .p2align 4
 L(return_null):
-       xor     %rax, %rax
+       xor     %eax, %eax
        ret
 
        .p2align 4
@@ -306,18 +306,16 @@ L(length_less16):
        punpcklbw       %xmm1, %xmm1
        punpcklbw       %xmm1, %xmm1
 
-       add     $16, %rdx
+       add     $16, %edx
 
        pshufd  $0, %xmm1, %xmm1
 
-       mov     %rdi, %rcx
-       and     $15, %rcx
+       mov     %edi, %ecx
+       and     $15, %ecx
        jz      L(length_less16_offset0)
 
-       mov     %rdi, %rcx
-       and     $15, %rcx
        mov     %cl, %dh
-       mov     %rcx, %r8
+       mov     %ecx, %esi
        add     %dl, %dh
        and     $-16, %rdi
 
@@ -340,7 +338,7 @@ L(length_less16):
 
        bsr     %eax, %eax
        add     %rdi, %rax
-       add     %r8, %rax
+       add     %rsi, %rax
        ret
 
        .p2align 4
@@ -362,14 +360,14 @@ L(length_less16_part2):
        pcmpeqb (%rdi), %xmm1
        pmovmskb        %xmm1, %eax
 
-       mov     %r8, %rcx
+       mov     %esi, %ecx
        sar     %cl, %eax
        test    %eax, %eax
        jz      L(return_null)
 
        bsr     %eax, %eax
        add     %rdi, %rax
-       add     %r8, %rax
+       add     %rsi, %rax
        ret
 
        .p2align 4