ref: 6b949925658e01e06a52c95d58d16bfc31d11912 dir: /builtins.amd64.s/
TEXT memcpyf(SB),1,$0 MOVQ RARG, DI MOVQ DI, AX MOVQ p2+8(FP), SI MOVL n+16(FP), CX CLD; REP; MOVSB RET