DATE: Thursday, May 3, 2001
TIME: Noon - 1 pm
PLACE: Wean Hall 8220

Ras Bodik

University of Wisconsin

Towards Critical-Path Instruction Processing

Although some instructions hurt performance more than others, processors apply scheduling and speculation as if each instruction was equally costly. The natural method for understanding the costs of parallel instructions is the critical path: if we could predict it, we could replace egalitarian policies with cost-sensitive strategies that will grow increasingly effective as processors become more sophisticated.

This talk will present our technology for critical-path instruction processing. I will start by demystifying the critical path of a microexecution, and follow by describing a predictor that computes the critical path very efficiently, without actually building a dependence graph. I will then focus on the multiple uses of the critical-path predictor in a modern processor, and show that it can improve instruction scheduling by up to 20%, without requiring any major changes to the existing processor designs.

A recent Pitt graduate, Ras Bodik is returning to Pittsburgh (the Miami of the Midwest) after what must have been the longest winter in Wisconsin history. When not shoveling snow, he is applying his compiler-optimization tricks to microarchitecture, program profiling, and dynamic program optimization.

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