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Implementation of Three Address Code Statements
There are three implementations used for three address code statements which are as follows −
- Quadruples
- Triples
- Indirect Triples
Quadruples
Quadruple is a structure that contains atmost four fields, i.e., operator, Argument 1, Argument 2, and Result.
| Operator | Argument 1 | Argument 2 | Result |
For a statement a = b + c, Quadruple Representation places + in the operator field, a in the Argument 1 field, b in Argument 2, and c in Result field.
For example− Consider the Statement
a = b + c * d
First, convert this statement into Three Address code
∴ Three Address code will be
t1 = c ∗ d
t2 = b + t1
a = t2.
After construction of the Three Address code, it will be changed to Quadruple representation as follows−
Quadruple
| Location | Operator | arg 1 | arg 2 | Result |
|---|---|---|---|---|
| (0) | * | c | d | t2 |
| (1) | + | b | t1 | t1 |
| (2) | = | t2 | A |
The content of fields arg 1, arg 2 and Result are pointers to symbol table entries for names represented by these entries.
Triples
This three address code representation contains three (3) fields, i.e., one for operator and two for arguments (i.e., Argument 1 and Argument 2)
| Operator | Argument 1 | Argument 2 |
In this representation, temporary variables are not used. Instead of temporary variables, we use a number in parenthesis to represent a pointer to that particular record of the symbol table.
For example, consider the statement
a = b + c * d
First of all, it will be converted to Three Address Code
∴ t1 = c ∗ d
t2 = b + t1
a = t2
Triple for this Three Address Code will be −
Triple
| Location | Operator | arg 1 | arg 2 |
|---|---|---|---|
| (0) | ∗ | C | d |
| (1) | + | B | (0) |
| (2) | = | A | (1) |
Here (0) represents a pointer that refers to the result c * d, which can be used in further statements, i.e., when c * d is added with b. This result will be saved at the position pointer by (1). Pointer (1) will be used further when it is assigned to a.
Indirect Triples
The indirect triple representation uses an extra array to list the pointers to the triples in the desired order. This is known as indirect triple representation.
Indirect Triple will be
In this, it can only need to refer to a pointer (0), (1), (2)which will further refer pointers(11), (12), (13) respectively & then pointers (11), (12), (13) point to triples that is why this representation is called indirect triple representation.
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