Control-Flow Independence Reuse via Dynamic Vectorization

Current processors exploit out-of-order execution and branch prediction to improve instruction level parallelism. When a branch prediction is wrong, processors flush the pipeline and squash all the speculative work. However, control-flow independent instructions compute the same results when they re-enter the pipeline down the correct path. If these instructions are not squashed, branch misprediction penalty can significantly be reduced. In this paper we present a novel mechanism that detects control-flow independent instructions, executes them before the branch is resolved, and avoids their re-execution in the case of a branch misprediction. The mechanism can detect and exploit control-flow independence even for instructions that are far away from the corresponding branch and even out of the instruction window. Performance figures show that the proposed mechanism can exploit control-flow independence for nearly 50% of the mispredicted branches, which results in a performance improvem...

• Type: Conference
• Year: 2005
• Where: IPPS
• Authors: Alex Pajuelo, Antonio González, Mateo Valero
• Keywords: Branch Prediction, Control-flow Independent Instructions, Distributed And Parallel Computing, Instruction, IPPS 2005