4/12/09
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CS 201
Compiler Construction
Lecture 5
Code Optimizations:
Copy Propagation & Elimination
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Global Code Optimizations
– Copy Propagation & Elimination: copy
assignments are eliminated by replacing lhs
variable with rhs variable.
– Constant Folding & Propagation: constant
assignments are exploited by substituting
constant values for variables; if all operands of
an expression are found to be constants, the
expression can be computed at compile time.
– Strength Reduction: replaces expensive
operations with cheaper ones – multiplaction
addition; exponentiation multiplication.
