This slide consists of a short introduction to three address code generation, different types of three address code generation such as assignment statements, assignment instructions, copy statements, Unconditional, Conditional, param x call p, n, indexed and address & pointer assignment statements.

1. Three Adress Code
Generation
Presented by:
Rabin BK

2. CONTENTS
01
02
03
INTRODUCTION
TYPES
EXAMPLE
04 REFERENCES

3. INTRODUCTION
● An intermediate code (machine independent code) used by the optimizing
compilers
● A sequence of statements of the general form x = y op z
● where x, y, z are names, constants
● op stands for any operator (such as fixed or floating point arithmetic
operator or a logical operator on boolean valued data)
● Eliminates the need of a new full compiler for every unique machine by
keeping the analysis portion same for all the compilers.
● Assumes to have unlimited number of memory storage (register) to
generate code

4. TYPES OF 3 ADDRESS STATEMENTS
● Assignment statements
– Having the form x := y op z
– op --> binary arithmetic or logical operation
● Assignment Instructions
– Having the form x := op y
– op --> unary operation (unary plus, unary minus shift etc)
● Copy statements
● Having the form x := y

5. TYPES OF 3 ADDRESS STATEMENTS CONTD...
● Unconditional (Jump goto L)
– The three address statement with label L is the next to be executed
● Conditional Jumps (such as if x relop y goto L)
– applies a relational operator (<,>,<=,>=) to x and y
– if (condition satisfied) { execute the statement with label L } else {
execute the statement following, if x relop y goto L }

6. TYPES OF 3 ADDRESS STATEMENTS CONTD...
● param x and call p, n
– Used for procedure calls and return y(represents returned value)
– generated as a part of the three address code for call of the
procedure p(x1,x2,x3,....xn) where n are the number of variables
being sent to the procedure
param x1
param x2
.
.
param xn
call p,n

7. TYPES OF 3 ADDRESS STATEMENTS CONTD...
● Indexed copy instructions
x = y[i]
x[i] = y
● Address and pointer assignments
x = &y
x = *y
*x = y

8. EXAMPLE
if (a < b + c)
a = a - c;
c = b * c;
_t1 = b + c;
_t2 = a < _t1;
If Z _t2 Goto _L0;
_t3 = a - c;
a = _t3;
_L0: _t4 = b * c;
c = _t4;
int foo(int a, int b){
return a + b;
}
void main() {
int c;
int d;
foo(c, d);
}
foo:
BeginFunc 4;
_t0 = a + b;
Return _t0;
EndFunc;
main:
BeginFunc 12;
PushParam d;
PushParam c;
_t1 = LCall _foo;
PopParams 8;
EndFunc;
Number of bytes
for a function
Stack operation

9. REFERENCES
● https://web.stanford.edu/class/archive/cs/cs143/cs143.1128/handouts/24
0%20TAC%20Examples.pdf
● https://web.stanford.edu/class/archive/cs/cs143/cs143.1128/lectures/13/S
lides13.pdf
● https://www.tutorialspoint.com/compiler_design/compiler_design_interme
diate_code_generations.htm
● https://www.javatpoint.com/three-address-code
● http://cic.puj.edu.co/wiki/lib/exe/fetch.php?media=materias:compi:comp_
sesion21_aux1.pdf

10. QUERIES