问题
I'm currently writing a toy compiler targeting Java bytecode in the translation.
I would like to know if there is some kind of catalog, maybe a summary, of various simple peephole optimizations that can be made in the emitted bytecode before writing the .class file. I actually am aware of some libraries that have this functionality, but I'd like to implement that myself.
回答1:
You are aware of Proguard? http://proguard.sourceforge.net/
This is a great bytecode optimizer which implements a lot of optimizations. See the FAQ for a list: http://proguard.sourceforge.net/FAQ.html
- Evaluate constant expressions.
- Remove unnecessary field accesses and method calls.
- Remove unnecessary branches.
- Remove unnecessary comparisons and instanceof tests.
- Remove unused code blocks.
- Merge identical code blocks.
- Reduce variable allocation.
- Remove write-only fields and unused method parameters.
- Inline constant fields, method parameters, and return values.
- Inline methods that are short or only called once.
- Simplify tail recursion calls.
- Merge classes and interfaces.
- Make methods private, static, and final when possible.
- Make classes static and final when possible.
- Replace interfaces that have single implementations.
- Perform over 200 peephole optimizations, like replacing ...*2 by ...<<1.
- Optionally remove logging code.
I'm sure you can further look into the source code to understand how they are implemented.
来源：https://stackoverflow.com/questions/1680024/compiler-optimization-java-bytecode