Easy Optimization Techniques

Some good optimization techniques include:

1. Generation of good code for common special cases, such as i = 0. These occur frequently enough to provide a good savings, and testing for them is easy.

2. Generation of good code for subscript expressions.
   • Code can be substantially shortened.

   • Subscript expressions occur often in code.

   • Subscript expressions occur inside loops.

3. Assigning variables to registers.
   • Much of code is loads and stores. A variable that is in a register does not have to be loaded or stored.

   • Easy case: assign a loop index variable to a register inside the loop.

   • General case: graph coloring for register assignment.

4. Reduction in strength: x * 8 → x << 3