명령어의 컴퓨터 내부 표현

register - number Mapping rule

$S0 $S1 $S2 $S3 $S4 $S5 $S6 $S7
16 17 18 19 20 21 22 23
$t0 $t1 $t2 $t3 $t4 $t5 $t6 $t7
8 9 10 11 12 13 14 15

MIPS 명령어 인코딩

instruction format op rs rt rd shamt funct address
add R 0 reg reg reg 0 32 NA
sub R 0 reg reg reg 0 34 NA
addi I 8 reg reg NA NA NA constant
lw(load word) I 35 reg reg NA NA NA address
sw(store word) I 43 reg reg NA NA NA address
sll(shift left logic) R 0 0 reg reg amount 0 NA
srl(shift right logic) R 0 0 reg reg amount 2 NA
And R 0 reg reg reg 0 36 NA
or R 0 reg reg reg 0 37 NA
nor R 0 reg reg reg 0 39 NA

register type

op rs rt rd shamt funct
6bits 5bits 5bits 5bits 5bits 6bits
연산자 source source 목적지 shift function

Immedate type

op rs rt constant or address
6bits 5bits 5bits 16bits
연산자 source 목적지 상수or주소

연습 문제

  • add $t1, $S2, $S3 -> 0(6), 18(5), 19(5), 9(5), 0(5), 32(6)
  • sub $S1, $S2, $S3 -> 0(6), 18(5), 19(5), 17(5), 0(5), 34(6)
  • lw $S1, 8($S3) -> 35(6), 19(5), 17(5), 8(16)

첫번째 문제

  • addi $t1, $t2, 4

    8(6), 10(5), 9(5), 4(16)

  • sw $t1, 16($t2)

    43(6), 10(5), 9(5), 16(16)

두번째 문제

A[10] = f + g - B[5]

A = $S0, f = $t0, g = $t1, B = $S1

add $t0, $t1, $t0
lw $t1, 20($S1)
sub $t0, $t1, $t0
sw $t0, 40($S0)
//convert
0(6), 8(5), 9(5), 8(5), 0(5), 32(6)
35(6), 17(5), 9(5), 20(16)
0(6), 8(5), 9(5), 8(5), 0(5), 34(6)
43(6), 16(5), 8(5), 40(16)

B[8] = A[i - j];
B = $S4, A = $S3, i = $S0, j = $ S1

sub $S0, $S0, $S1
sll $S0, $S0, 2
add $S0, $S3, $S0
lw $S1, 0($S0)
sw $S1, 32($S4)

0(6)16(5)17(5)16(5)0(5)34(6)
0(6)0(5)16(5)16(5)2(5)0(6)
0(6)19(5)16(5)16(5)0(6)32(6)
43(6)16(5)17(5)0(16)
43(6)20(5)16(5)32(16)