Guarded execution and branch prediction in dynamic ILP processors

Evaluates the effects of guarded (or conditional, or predicated) execution on the performance of an instruction level parallel processor employing dynamic branch prediction. First, the authors assess the utility of guarded execution, both qualitatively and quantitatively, using a variety of application programs. The assessment shows that guarded execution significantly increases the opportunities, for both compiler and dynamic hardware, to extract and exploit parallelism. However, existing methods of specifying guarded execution have several drawbacks that limit its use. Second, the authors study the interaction of guarded execution and dynamic branch prediction and show that the use of guarded execution significantly increases the number of instructions between mispredicted branches. Third, they propose a new method of specifying guarded execution. The proposed method uses special GUARD instructions, which can be used to incorporate guarded execution into existing instruction sets. GUARD instructions realize the full power of guarded execution, without the drawbacks of existing methods of specifying guarded execution