Editing Optimizing compiler (section)

=== Peephole optimization ===
[[Peephole optimization]]s are usually performed late in the compilation process after [[machine code]] has been generated. This optimization examines a few adjacent instructions (similar to "looking through a peephole" at the code) to see whether they can be replaced by a single instruction or a shorter sequence of instructions.<ref name="aho-sethi-ullman" />{{rp|page=554}} For instance, a multiplication of a value by two might be more efficiently executed by [[Bit shift|left-shifting]] the value or by adding the value to itself (this example is also an instance of [[strength reduction]]).