diff --git a/src/string/x86_64/memset.s b/src/string/x86_64/memset.s
index 3cc8fcf6b718295f4c977da2d7957d7d53d9c421..2d3f5e52b8afe8d612c0fd0b04f4e8a01f078489 100644
--- a/src/string/x86_64/memset.s
+++ b/src/string/x86_64/memset.s
@@ -1,43 +1,72 @@
 .global memset
 .type memset,@function
 memset:
-	movzbl %sil,%esi
-	mov $0x101010101010101,%rax
-	# 64-bit imul has 3-7 cycles latency, launch early
-	imul %rsi,%rax
+	movzbq %sil,%rax
+	mov $0x101010101010101,%r8
+	imul %r8,%rax
 
-	cmp $16,%rdx
-	jb 1f
+	cmp $126,%rdx
+	ja 2f
 
-	lea -1(%rdx),%rcx
-	mov %rdi,%r8
-	shr $3,%rcx
-	mov %rax,-8(%rdi,%rdx)
-	rep
-	stosq
-	mov %r8,%rax
-	ret
-
-1:	test %edx,%edx
+	test %edx,%edx
 	jz 1f
 
-	mov %al,(%rdi)
-	mov %al,-1(%rdi,%rdx)
+	mov %sil,(%rdi)
+	mov %sil,-1(%rdi,%rdx)
 	cmp $2,%edx
 	jbe 1f
 
-	mov %al,1(%rdi)
-	mov %al,-2(%rdi,%rdx)
-	cmp $4,%edx
+	mov %ax,1(%rdi)
+	mov %ax,(-1-2)(%rdi,%rdx)
+	cmp $6,%edx
+	jbe 1f
+
+	mov %eax,(1+2)(%rdi)
+	mov %eax,(-1-2-4)(%rdi,%rdx)
+	cmp $14,%edx
+	jbe 1f
+
+	mov %rax,(1+2+4)(%rdi)
+	mov %rax,(-1-2-4-8)(%rdi,%rdx)
+	cmp $30,%edx
 	jbe 1f
 
-	mov %eax,(%rdi)
-	mov %eax,-4(%rdi,%rdx)
-	cmp $8,%edx
+	mov %rax,(1+2+4+8)(%rdi)
+	mov %rax,(1+2+4+8+8)(%rdi)
+	mov %rax,(-1-2-4-8-16)(%rdi,%rdx)
+	mov %rax,(-1-2-4-8-8)(%rdi,%rdx)
+	cmp $62,%edx
 	jbe 1f
 
-	mov %eax,4(%rdi)
-	mov %eax,-8(%rdi,%rdx)
+	mov %rax,(1+2+4+8+16)(%rdi)
+	mov %rax,(1+2+4+8+16+8)(%rdi)
+	mov %rax,(1+2+4+8+16+16)(%rdi)
+	mov %rax,(1+2+4+8+16+24)(%rdi)
+	mov %rax,(-1-2-4-8-16-32)(%rdi,%rdx)
+	mov %rax,(-1-2-4-8-16-24)(%rdi,%rdx)
+	mov %rax,(-1-2-4-8-16-16)(%rdi,%rdx)
+	mov %rax,(-1-2-4-8-16-8)(%rdi,%rdx)
 
 1:	mov %rdi,%rax
 	ret
+
+2:	test $15,%edi
+	mov %rdi,%r8
+	mov %rax,-8(%rdi,%rdx)
+	mov %rdx,%rcx
+	jnz 2f
+
+1:	shr $3,%rcx
+	rep
+	stosq
+	mov %r8,%rax
+	ret
+
+2:	xor %edx,%edx
+	sub %edi,%edx
+	and $15,%edx
+	mov %rax,(%rdi)
+	mov %rax,8(%rdi)
+	sub %rdx,%rcx
+	add %rdx,%rdi
+	jmp 1b