State-of-the-Art Question

Hello, I have a question about the comp-sci state-of-the-art:

I recently ran across the concept of a "software optimizer" in a work
of fiction. This was a piece of software that would take source code
in a given language and edit it in such a way that it would perform
more efficiently.

Now, I know that compilers can do this to some extent, but they're not
terribly good at it. Is there anything along those lines that is
better? (And no, I don't mean human beings or grad students, thank you
very much).

Please reply privately at:

mithrandir25-at-hotmail-dotcom (please no spam)

Thank you.