We design an algorithm for solving the given problem using high-level pseudocode containing constructs similar to a high-level language like python or java. For example,

input a
input b
if a < b then
    output a
else
    output b

We then translate the pseudocode into SLIM assembly language.

read 0
read 1
li 3 7
slt 2 0 1
jeqz 2 3
write 0
halt
write 1
halt 

Expressions and assignment statements are implemented using SLIM’s arithmetic, comparison, and data movement commands. The tricky part is in dividing the high-level expressions into a much larger number of SLIM instructions. E.g., a python statement

a = b*b + c*c

becomes

mul b2 b b
mul c2 c c
add a b2 c2

in SLIM assembly instructions, where b, b2, c, c2, and a are register numbers with register b containing the variable b and register c containing the variable c.

A python if statement like

if a < b:
    <st1>
    <st2>
<st3>

gets translated into

    li  after afterL
    slt testResult a b
    jeqz testResult after
    <st1>
    <st2>
afterL:
    <st3>

A python if..else statement like

if a < b:
    <st1>
    <st2>
else:
    <st3>
    <st4>
<st5>

gets translated into

    li else elseL
    li after afterL
    slt testResult a b
    jeqz testResult else
    <st1>
    <st2>
    j after
elseL:
    <st3>
    <st4>
afterL:
    <st5>

A python while statement like

while a < b:
    <st1>
    <st2>
<st3>

gets translated into

    li loop loopL
    li end endL
loopL:
    slt testResult a b
    jeqz testResult end
    <st1>
    <st2>
    j loop
endL:
    <st3>

A python for statement like

for x in range(a, b):
    <st1>
    <st2>

gets translated into the while statement

x = a
while x < b:
    <st1>
    <st2>
    x += 1

and then we can translate the while statement like in the previous slide.