Local Common Subexpression Elimination

Local Common Strength Reduction

Local Constant Propagation and Folding

Algebraic Identities

An algebraic identity performs a substitution using algebraic laws. We list a few:

	1. X := A + 0		   X := A
 	2. X := 1 * A		   X := A
        3. Constant * Symbol       Symbol * Constant
 
 

Algebraic substitution can substitute one expression in a basic block with another as shown in Example 6.

EXAMPLE 6 Algebraic Substitution

        
          T1 := BB * J - 1           T1 := BB * J - 1
          ...                     ...
          T1 := T1 + 1               T7 := 4 * J