UW PLSE

John Regehr

visitor-photo

Superoptimizing LLVM

December 2, 2014 at 3:30pm
EEB 105

Abstract

Compilers are caught in a tug-of-war between increasingly exotic architectures and instruction set extensions on one hand, and our desire for advanced programming languages and PL features on the other. A multi-language, multi-target compiler infrastructure such as LLVM ameliorates the situation somewhat, but engineering fast, effective, and correct optimizations for LLVM is challenging. Even after a decade of intense development, there is a long tail of unimplemented optimizations.

This talk will present Souper, a superoptimizer that gives us a look at some of the optimizations that are missing from LLVM while also avoiding the bugs that are often found in hand-written optimization passes. Souper works by turning LLVM code into queries for an automated theorem prover. When Souper is run on LLVM itself, it identifies thousands of uncaught optimizations and also ranks them according to the likely improvement in code size or code speed that would result from implementing each one.

Bio

John has been on the Utah faculty since 2003. When he isn’t working, he likes to spend time outdoors.

Talk