Question

Compiling C Programs into MIPS Assembly and Machine Code

sll $t1, $a1, 2

add $t1, $a0. $t1

lw $t0, 0($t1)

lw $t2, 4($t1)

sw $t2, 0($t1)

sw $t0, 4($t1)

1. From the assembly code, what machine code might a MIPS assembler produce?

2. What does this program do? Write the C code for this assembly program.

Answer 1

Answer 1:

Machine code for the given assembly code:

0x00054880 0x00094820 0x8d280000 0x8d2a0004 0xad2a0000 0xad280004

Explanation:

Line 1: 0x00000000:0x00054880 [sll $t1 $a1 2 => R(op:0(sll) rs:0(0) rt:5(a1) rd:9(t1) sh:2 func:0)] Line 2: 0x00000004:0x00094820 [add $t1 $a0. $t1 => R(op:0(add) rs:a0.(a0.) rt:9(t1) rd:9(t1) sh:0 func:32)] Line 3: 0x00000008:0x8d280000 [lw $t0 0($t1) => I(op:35(lw) rs:9(t1) rt:8(t0) immed:0x00000000)] Line 4: 0x0000000c:0x8d2a0004 [lw $t2 4($t1) => I(op:35(lw) rs:9(t1) rt:10(t2) immed:0x00000004)] Line 5: 0x00000010:0xad2a0000 [sw $t2 0($t1) => I(op:43(sw) rs:9(t1) rt:10(t2) immed:0x00000000)] Line 6: 0x00000014:0xad280004 [sw $t0 4($t1) => I(op:43(sw) rs:9(t1) rt:8(t0) immed:0x00000004)]

Answer 2:

Given code is doing swapping of array elements.

C code for this assembly program:

temp = v[k];

v[k] = v[k+1];

v[k+1] = temp;

Explanation:

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