ref: 6386a0391a11fd3c5216dfe1478fda08ae8bccbc
dir: /sys/src/libc/386/memmove.s/
TEXT memmove(SB), $0 MOVL p1+0(FP), DI MOVL DI, AX /* return value */ MOVL p2+4(FP), SI MOVL n+8(FP), BX CMPL BX, $0 JGT _ok JEQ _return /* nothing to do if n == 0 */ MOVL $0, SI /* fault if n < 0 */ /* * check and set for backwards: * (p2 < p1) && ((p2+n) > p1) */ _ok: CMPL SI, DI JGT _forward JEQ _return /* nothing to do if p2 == p1 */ MOVL SI, DX ADDL BX, DX CMPL DX, DI JGT _back /* * copy whole longs */ _forward: MOVL BX, CX CLD SHRL $2, CX ANDL $3, BX REP; MOVSL /* * copy the rest, by bytes */ JEQ _return /* flags set by above ANDL */ MOVL BX, CX REP; MOVSB RET /* * whole thing backwards has * adjusted addresses */ _back: ADDL BX, DI ADDL BX, SI STD SUBL $4, DI SUBL $4, SI /* * copy whole longs */ MOVL BX, CX SHRL $2, CX ANDL $3, BX REP; MOVSL /* * copy the rest, by bytes */ JEQ _return /* flags set by above ANDL */ ADDL $3, DI ADDL $3, SI MOVL BX, CX REP; MOVSB _return: RET