Advanced Micro Devices, Inc.
COLLAPSING BUBBLES IN A PROCESSING UNIT PIPELINE

Abstract:

An arithmetic logic unit (ALU) pipeline of a processing unit collapses execution bubbles in response to a stall at a stage of the ALU pipeline. An execution bubble occurs at the pipeline in response to an invalid instruction being placed in the pipeline for execution. The invalid instruction thus consumes an available "slot" in the pipeline, and proceeds through the pipeline until a stall in a subsequent stage (that is, a stage after the stage executing the invalid instruction) is detected. In response to detecting the stall, the ALU continues to execute instructions that are behind the invalid instruction in the pipeline, thereby collapsing the execution bubble and conserving resources of the ALU.in response to a stall at a stage of the ALU pipeline.