github.com/afumu/libc@v0.0.6/musl/src/string/x86_64/memcpy.s (about)

     1  .global memcpy
     2  .global __memcpy_fwd
     3  .hidden __memcpy_fwd
     4  .type memcpy,@function
     5  memcpy:
     6  __memcpy_fwd:
     7  	mov %rdi,%rax
     8  	cmp $8,%rdx
     9  	jc 1f
    10  	test $7,%edi
    11  	jz 1f
    12  2:	movsb
    13  	dec %rdx
    14  	test $7,%edi
    15  	jnz 2b
    16  1:	mov %rdx,%rcx
    17  	shr $3,%rcx
    18  	rep
    19  	movsq
    20  	and $7,%edx
    21  	jz 1f
    22  2:	movsb
    23  	dec %edx
    24  	jnz 2b
    25  1:	ret