ref: a6ccb66d9c0748d44cd622d6a700d1ad6447cada
dir: /sys/src/libc/amd64/memccpy.s/
TEXT memccpy(SB),$0 MOVQ n+24(FP), CX CMPQ CX, $0 JEQ none MOVQ p2+8(FP), DI MOVBLZX c+16(FP), AX CLD /* * find the character in the second string */ REPN; SCASB JEQ found /* * if not found, set count to 'n' */ none: MOVL $0, AX MOVQ n+24(FP), BX JMP memcpy /* * if found, set count to bytes thru character */ found: MOVQ DI, AX SUBQ p2+8(FP), AX MOVQ AX, BX ADDQ RARG, AX /* * copy the memory */ memcpy: MOVQ RARG, DI MOVQ p2+8(FP), SI /* * copy whole longs, if aligned */ MOVQ DI, DX ORQ SI, DX ANDL $3, DX JNE c3 MOVQ BX, CX SHRQ $2, CX REP; MOVSL /* * copy the rest, by bytes */ ANDL $3, BX c3: MOVQ BX, CX REP; MOVSB RET