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| Constant Propagation |
| -------------------- |
| Constant propagation is a code reduction technique in which values of variables |
| which are determined to be constants can be passed to expressions which use |
| these constants and can be computed at compile time. |
| |
| |
| Example: |
| |
| Consider the following segment of an original source program: |
| |
| x = 7; |
| y = 2 * x; |
| z = f (x, y); |
| |
| The value of variable x in the segment's last two lines is the constant number 7. |
| This is always true, because of the assignment to x in the segment's first line. |
| Therefore, the two instances of x can be substituted by the constant value 7 |
| (this value propagates through the next two lines). The reduced source program |
| is the following: |
| |
| x = 7; |
| y = 2 * 7; |
| z = f (7, y); |
