ref: c3ba64f6935322f09b6de5c2285544fd471c605d
dir: /sys/src/libc/arm/strchr.s/
TEXT strchr(SB), $0 MOVBU c+4(FP), R1 CMP $0, R1 BEQ _null _strchr: /* not looking for a null, byte at a time */ MOVBU.P 1(R0), R2 CMP R1, R2 BEQ _sub1 CMP $0, R2 BNE _strchr _return0: /* character not found in string, return 0 */ MOVW $0, R0 RET _null: /* looking for null, align */ AND.S $3, R0, R2 BEQ _aligned MOVBU.P 1(R0), R4 CMP $0, R4 BEQ _sub1 B _null _aligned: MOVW $0xFF, R3 /* mask */ _loop: MOVW.P 4(R0), R4 /* 4 at a time */ TST R4, R3 /* AND.S R2, R3, Rx */ TST.NE R4>>8, R3 TST.NE R4>>16, R3 TST.NE R4>>24, R3 BNE _loop TST R4, R3 /* its somewhere, find it and correct */ BEQ _sub4 TST R4>>8, R3 BEQ _sub3 TST R4>>16, R3 BEQ _sub2 _sub1: /* compensate for pointer increment */ SUB $1, R0 RET _sub2: SUB $2, R0 RET _sub3: SUB $3, R0 RET _sub4: SUB $4, R0 RET