ref: 4dbb99f478d68eaeea4c043a839454cb807c2c7d
dir: /sys/src/libc/68020/memcpy.s/
TEXT memcpy(SB), $0 MOVL n+8(FP),R0 BEQ return BGT ok MOVL 0, R0 ok: MOVL s1+0(FP),A2 MOVL s2+4(FP),A1 CMPL A2,A1 BHI back /* * speed depends on source allignment * destination allignment is secondary * 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 /* * quad-long-at-a-time forward copy */ f2: SUBL $16, R0 BLT f3 MOVL (A1)+, (A2)+ MOVL (A1)+, (A2)+ MOVL (A1)+, (A2)+ MOVL (A1)+, (A2)+ BRA f2 /* * cleanup byte-at-a-time */ f3: ADDL $15, R0 BLT return f4: MOVB (A1)+, (A2)+ SUBL $1, R0 BGE f4 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 /* * quad-long-at-a-time backward copy */ b2: SUBL $16, R0 BLT b3 MOVL -(A1), -(A2) MOVL -(A1), -(A2) MOVL -(A1), -(A2) MOVL -(A1), -(A2) BRA b2 /* * cleanup byte-at-a-time backward */ b3: ADDL $15, R0 BLT return b4: MOVB -(A1), -(A2) SUBL $1, R0 BGE b4 BRA return