ref: becb89bae53e01785bfd843478737eeb77a9419f
dir: /sys/src/libc/68000/memcpy.s/
TEXT memcpy(SB), $0 MOVL n+8(FP), R0 /* count */ BEQ return BGT ok MOVL 0, R0 ok: MOVL s1+0(FP), A2 /* dest pointer */ MOVL s2+4(FP), A1 /* source pointer */ CMPL A2,A1 BHI back /* * byte-at-a-time foreward copy to * get source (A1) alligned. */ f1: MOVL A1, R1 ANDL $3, R1 BEQ f2 SUBL $1, R0 BLT return MOVB (A1)+, (A2)+ BRA f1 /* * check that dest is alligned * if not, just go byte-at-a-time */ f2: MOVL A2, R1 ANDL $3, R1 BEQ f3 SUBL $1, R0 BLT return BRA f5 /* * quad-long-at-a-time forward copy */ f3: SUBL $16, R0 BLT f4 MOVL (A1)+, (A2)+ MOVL (A1)+, (A2)+ MOVL (A1)+, (A2)+ MOVL (A1)+, (A2)+ BRA f3 /* * cleanup byte-at-a-time */ f4: ADDL $15, R0 BLT return f5: MOVB (A1)+, (A2)+ SUBL $1, R0 BGE f5 BRA return return: MOVL s1+0(FP),R0 RTS /* * everything the same, but * copy backwards */ back: ADDL R0, A1 ADDL R0, A2 /* * byte-at-a-time backward copy to * get source (A1) alligned. */ b1: MOVL A1, R1 ANDL $3, R1 BEQ b2 SUBL $1, R0 BLT return MOVB -(A1), -(A2) BRA b1 /* * check that dest is alligned * if not, just go byte-at-a-time */ b2: MOVL A2, R1 ANDL $3, R1 BEQ b3 SUBL $1, R0 BLT return BRA b5 /* * quad-long-at-a-time backward copy */ b3: SUBL $16, R0 BLT b4 MOVL -(A1), -(A2) MOVL -(A1), -(A2) MOVL -(A1), -(A2) MOVL -(A1), -(A2) BRA b3 /* * cleanup byte-at-a-time backward */ b4: ADDL $15, R0 BLT return b5: MOVB -(A1), -(A2) SUBL $1, R0 BGE b5 BRA return