Editing Three-address code (section)

== Examples ==
In three-address code, this would be broken down into several separate instructions. These instructions translate more easily to [[assembly language]]. It is also easier to detect [[common subexpression elimination|common sub-expressions]] for shortening the code. In the following example, one calculation is composed of several smaller ones:

{{col-begin}}
{{col-2}}
<pre style="overflow: auto;">
# Calculate one solution to the [[Quadratic equation]].
x = (-b + sqrt(b^2 - 4*a*c)) / (2*a)
</pre>
{{col-2}}
<pre style="overflow: auto;">
t1 := b * b
t2 := 4 * a
t3 := t2 * c
t4 := t1 - t3
t5 := sqrt(t4)
t6 := 0 - b
t7 := t5 + t6
t8 := 2 * a
t9 := t7 / t8
x := t9
</pre>
{{col-end}}

Three-address code may have conditional and unconditional jumps and methods of accessing memory. It may also have methods of calling functions, or it may reduce these to jumps. In this way, three-address code may be useful in [[control-flow analysis]]. In the following C-like example, a loop stores the squares of the numbers between 0 and 9:

{{col-begin}}
{{col-2}}
<syntaxhighlight lang="c" style="margin-top: 1em;">
...

for (i = 0; i < 10; ++i) {
    b[i] = i*i; 
}

...
</syntaxhighlight>
{{col-2}}
<pre style="overflow: auto;">
     t1 := 0                ; initialize i
L1:  if t1 >= 10 goto L2    ; conditional jump
     t2 := t1 * t1          ; square of i
     t3 := t1 * 4           ; word-align address
     t4 := b + t3           ; address to store i*i
     *t4 := t2              ; store through pointer
     t1 := t1 + 1           ; increase i
     goto L1                ; repeat loop
L2:
</pre>
{{col-end}}