Procedures classification for optimizing strategy assignment

Optimizing compilers make significant contribution to the performance of modern computer systems. Among them VLIW architecture processors are the most compiler-dependent, since their performance is ensured by effective compile time scheduling of multiple commands in a single clock. This leads to an eventual complication of VLIW compilers. Taking as an example optimizing compiler developed for the Elbrus family processors, it runs consequently over 300 stages of code optimization in basic mode. Such an amount of stages is needed to obtain decent performance, but it also makes compilation quite time consuming. It turns out that the main reason for compilation time increase when using high level compilation is applying some aggressive unreversable code transformations, which eventually leads to code size increase that is also unwanted. In addition, there remains the problem of using a number of optimizations that are useful for rare contexts. To reach the objectives, namely increasing performance, decreasing compilation time and code size, it is reasonable to choose an appropriate strategy on an early compilation stage according to some procedure specific characteristics. This paper discusses the procedures classification problems for this task and suggests several possible solutions.