I've only read a little bit in Optimizing Compilers for Modern Architectures, but it seems a pretty complete introduction: http://www.amazon.com/Optimizing-Compilers-Modern-Architectu...

Another space you can look for interesting things (not necessarily optimising compilation) is the compilation of functional programming languages. They usually take a slightly different approach compared to imperative languages, though there's clearly a lot of overlap. I really enjoy reading in an old book called The Implementation of Functional Programming Languages from 1987, which is available online: http://research.microsoft.com/en-us/um/people/simonpj/papers...