Control Independence in Trace Processors

Branch mispredictions are a major obstacle to exploiting instruction-level parallelism, at least in part because all instructions after a mispredicted branch are squashed. However, instructions that are control independent of the branch must be fetched regardless of the branch outcome, and do not necessarily have to be squashed and re-executed. Control independence exists when the two paths following a branch re-converge. A trace processor microarchitecture is developed to exploit control independence and thereby reduce branch misprediction penalties. There are three major contributions. 1) Trace-level re-convergence is not guaranteed despite re-convergence at the instruction-level. Novel trace selection techniques are developed to expose control independence at the trace-level. 2) Control independence's potential complexity stems from insertion and removal of instructions from the middle of the instruction window. Trace processors manage control flow hierarchically (traces are t...

• Type: Conference
• Year: 1999
• Where: MICRO
• Authors: Eric Rotenberg, James E. Smith
• Keywords: Control Flow, Control Independence, Hardware, MICRO 1999, Trace Processor