The situation is different, because a CPU is by definition an interpreter. It does't perform code transformation, at least not at a higher level as a compiler.

The situation is different, because a CPU is by definition an interpreter. It does't perform code transformation, at least not at a higher level as a compiler. The CPU only looks at the next few instructions and perform them. A compiler, however, is responsible for taking a large coding unit and produce a transformation that is efficient. That process requires thinking about what is invalid code and operate on that.