Lecture Notes for Computer Architecture II - St. Cloud State University

Translation of Procedures
Problem
HLL procedure MIPS
swap(int v[], int k)
{ int temp
temp = v[k];
v[k]=v[k+1];
v[k+1]=temp;
}
Page | 53
Complete Solution
- allocate registers to variables
- generate code for the body of the procedure
- reserve contents of registers across the procedure invocation
Step1 Assign variables to registers
temp v k
$t 0 $a 0 $a 1
Step 2 Do simple translations
mult $a 1 $a 1 4
add $t 1 $a 0 $a 1
lw $t 0 0($t 1 )
lw $t 2 4($t 1 )
sw $t 2 0($t 1 )
sw $t 0 4($t 1 )
jr $ra jump back to calling procedure
in MIPS – mult $a 1 $a 1 4
Adjust the stack to make room for 2 items
Sub $sp, $sp, 8
Step 3 save the content of registers on stack
sw $t 1 4($SP)
sw $t 2 0($SP)
Step 4 load the registers back after completion of the procedure
lw $t 2 0($sp)
lw $t 1 4($sp)
Adjust the stack to delete 2 items
Add $sp, $sp, 8