Automatic Correction of Loop Transformations

Loop nest optimization is a combinatorial problem. Due to the growing complexity of modern architectures, it involves two increasingly difficult tasks: (1) analyzing the profitability of sequences of transformations to enhance parallelism, locality, and resource usage, which amounts to a hard problem on a non-linear objective function; (2) the construction and exploration of search space of legal transformation sequences. Practical optimizing and parallelizing compilers decouple these tasks, resorting to a predefined set of enabling transformations to eliminate all sorts of optimization-limiting semantical constraints. State-of-theart optimization heuristics face a hard decision problem on the selection of enabling transformations only remotely related to performance. We propose a new design where optimization heuristics first address the main performance anomalies, then correct potentially illegal loop transformations a posteriori, attempting to minimize the performance impact of...

• Type: Conference
• Year: 2007
• Where: IEEEPACT
• Authors: Nicolas Vasilache, Albert Cohen, Louis-Noël Pouchet
• Keywords: Hardware, IEEEPACT 2007, Illegal Loop Transformations, Loop Transformations, Optimization Heuristics