ref: 8188b4f4f0e07b6669e6ae3c6c1099af917eaab4
dir: /sys/src/libc/amd64/strcpy.s/
TEXT strcpy(SB),$0 MOVL $0, AX MOVQ $-1, CX CLD /* * find end of second string */ MOVQ p2+8(FP), DI REPN; SCASB MOVQ DI, BX SUBQ p2+8(FP), BX /* * copy the memory */ MOVQ RARG, DI MOVQ p2+8(FP), SI /* * copy whole longs, if aligned */ MOVQ DI, CX ORQ SI, CX ANDL $3, CX JNE c3 MOVQ BX, CX SHRQ $2, CX REP; MOVSL /* * copy the rest, by bytes */ ANDL $3, BX c3: MOVL BX, CX REP; MOVSB MOVQ RARG, AX RET