ref: c8d87b22d50a17b8832019a93b9293fef19fbd02
dir: /sys/src/libc/arm/strcpy.s/
TEXT strcpy(SB), $0 MOVW R0, to+0(FP) /* need to save for return value */ MOVW from+4(FP), R1 MOVW $0xFF, R2 /* mask */ salign: /* align source on 4 */ AND.S $3, R1, R3 BEQ dalign MOVBU.P 1(R1), R3 /* implicit write back */ TST R3, R2 MOVBU.P R3, 1(R0) /* implicit write back */ BNE salign B return dalign: /* is destination now aligned? */ AND.S $3, R0, R3 BNE uloop aloop: MOVW.P 4(R1), R4 /* read 4, write 4 */ TST R4, R2 /* AND.S R3, R2, Rx */ TST.NE R4>>8, R2 TST.NE R4>>16, R2 TST.NE R4>>24, R2 BEQ tail MOVW.P R4, 4(R0) B aloop uloop: MOVW.P 4(R1), R4 /* read 4, write 1,1,1,1 */ tail: AND.S R4, R2, R3 MOVBU.NE.P R3, 1(R0) AND.NE.S R4>>8, R2, R3 MOVBU.NE.P R3, 1(R0) AND.NE.S R4>>16, R2, R3 MOVBU.NE.P R3, 1(R0) AND.NE.S R4>>24, R2, R3 MOVBU.P R3, 1(R0) BNE uloop B return return: MOVW to+0(FP), R0 RET