Peephole optimization examples.

Redundant loads and stores

. Consider the code sequence

Move R₀ , a Move a, R₀

. Instruction 2 can always be removed if it does not have a label.

Now, we will give some examples of program transformations that are characteristic of peephole optimization: Redundant loads and stores: If we see the instruction sequence

Move R₀ , a

Move a, R₀

We can delete instruction (2) because whenever (2) is executed, (1) will ensure that the value of a is already in register R0. Note that is (2) has a label, we could not be sure that (1) was always executed immediately before (2) and so we could not remove (2).