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

Lecture 8
Conditional Statements If Switch
- beq - branch equal
- bne - branch not equal
- slt - set less than
- j - jump
- jr - jump register
Page | 42
beq $S 1 $S 2 L
means if $S 1 = = $S 2 jump to L
= = means equal
bne $S1 $S2 L
means if ( $s1 = /= $s2) goto L
Problem
Translate the following HLL statement
if (i = = j) f = g+h; else f = g-h;
= means assignment
Solution
Step1 Assign variables to registers
f g h i j
$S 0 $S 1 $S 2 $S 3 $S 4
Step 2 Do simple translations
A. add $S 0 $S 1 $S 2 f = g+h
B. sub $S 0 $S 1 $S 2 f = g-h;
Now organize the translation
bne $S 3 $S 4 else
A
j exit
else: B
exit:
Completed code
bne $S 3 $S 4 else
add $S 0 $S 1 $S 2
j exit
else: sub $S 0 $S 1 $S 2
exit: