SYZYGY - A Framework for Scalable Cross-Module IPO

Performing analysis across module boundariesfor an entire program is important for exploitingseveral runtime performance opportunities. However,due to scalability problems in existing full-programanalysis frameworks, such performance opportunitiesare only realized by paying tremendous compile-timecosts. Alternative solutions, such as partialcompilations or user assertions, are complicated orunsafe and as a result, not many commercialapplications are compiled today with cross-moduleoptimizations.This paper presents SYZYGY, a practicalframework for performing efficient, scalable,interprocedural optimizations. The framework isimplemented in the HP-UX Itanium® compilers andwe have successfully compiled many very largeapplications consisting of millions of lines of code. Weachieved performance improvements of up to 40%over optimization level two and compilation timeimprovements in the order of 100% and morecompared to a previous approach.