x86_64/memset: simple optimizations

[musl] / src / string / x86_64 / memset.s

diff --git a/src/string/x86_64/memset.s b/src/string/x86_64/memset.s
index fc06eef..263336b 100644 (file)
--- a/src/string/x86_64/memset.s
+++ b/src/string/x86_64/memset.s
@@ -1,41 +1,43 @@
 .global memset
 .type memset,@function
 memset:
-       and $0xff,%esi
+       movzbl %sil,%esi
        mov $0x101010101010101,%rax
-       mov %rdx,%rcx
-       mov %rdi,%r8
+       # 64-bit imul has 3-7 cycles latency, launch early
        imul %rsi,%rax
-       cmp $16,%rcx
+
+       cmp $16,%rdx
        jb 1f
 
-       mov %rax,-8(%rdi,%rcx)
+       mov %rdx,%rcx
+       mov %rdi,%r8
        shr $3,%rcx
+       mov %rax,-8(%rdi,%rdx)
        rep
        stosq
        mov %r8,%rax
        ret
 
-1:     test %ecx,%ecx
+1:     test %edx,%edx
        jz 1f
 
        mov %al,(%rdi)
-       mov %al,-1(%rdi,%rcx)
-       cmp $2,%ecx
+       mov %al,-1(%rdi,%rdx)
+       cmp $2,%edx
        jbe 1f
 
        mov %al,1(%rdi)
-       mov %al,-2(%rdi,%rcx)
-       cmp $4,%ecx
+       mov %al,-2(%rdi,%rdx)
+       cmp $4,%edx
        jbe 1f
 
        mov %eax,(%rdi)
-       mov %eax,-4(%rdi,%rcx)
-       cmp $8,%ecx
+       mov %eax,-4(%rdi,%rdx)
+       cmp $8,%edx
        jbe 1f
 
        mov %eax,4(%rdi)
-       mov %eax,-8(%rdi,%rcx)
+       mov %eax,-8(%rdi,%rdx)
 
-1:     mov %r8,%rax
+1:     mov %rdi,%rax
        ret