Forward Branch Processing to Avoid Pipeline Flushes
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Solution Overview
Problem
Computational inefficiencies and pipeline flushing occur when executing tasks with forward conditional branch instructions, particularly in AI-based tasks, leading to reduced performance and increased resource consumption.
Innovation Solution
Invalidating data elements associated with forward conditional branch instructions when the positive offset is less than or equal to an offset threshold value, thereby preventing pipeline flushing and improving computational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If forward conditional branch instructions are executed with full conditional code, then correctness is maintained, but pipeline flushing occurs causing computational inefficiency
Solution Approach 1:
The patent extracts and removes the conditional code portion from the forward conditional branch instruction, keeping only the unconditional branch. This extraction eliminates the source of pipeline misprediction while maintaining correct branch behavior, directly resolving the contradiction between correctness and pipeline efficiency
Solution Approach 2:
The patent changes the parameter of the branch instruction by removing the conditional aspect and converting it to an unconditional branch with a calculated target address. This parameter change transforms the instruction from potentially causing pipeline flush to being safely predictable, improving productivity without sacrificing correctness
2Productivity
If forward conditional branch instructions are executed with full conditional code, then accuracy is maintained, but code length increases
Solution Approach 1:
The conditional code is extracted and removed from the instruction sequence. The branch target address is pre-calculated based on the offset, eliminating the need to store and execute separate conditional logic, thereby reducing code size while maintaining execution speed
Solution Approach 2:
The branch target address is pre-calculated and prepared before execution by combining the current program counter with the offset. This preliminary action eliminates the need for conditional code during execution, reducing both code size and execution time
3Productivity
If forward conditional branch instructions are executed with full conditional code, then completeness is maintained, but power consumption increases
Solution Approach 1:
The conditional code is extracted and eliminated, removing the computational overhead associated with evaluating branch conditions. This reduction in executed instructions directly lowers power consumption while maintaining computational efficiency through the simplified unconditional branch
Solution Approach 2:
The unconditional branch enables continuous pipeline flow without the interruptions caused by conditional code evaluation and potential mispredictions. This continuous execution reduces wasted cycles and associated power consumption, maintaining productivity while improving energy efficiency
Data Source
AI summary
Various embodiments described herein control circuitry of a computing device to invalidate certain data elements associated with a forward conditional branch instruction (FCBI) to prevent computational inefficiencies, such pipeline flush. The data elements that are invalidated may correspond to conditional code associated with an FCBI. To make FCBIs more efficient, certain embodiments continue with a not-taken path that is invalidated if a branch resolves to be taken. This results in efficiencies because either the prediction was correct; or when the wrong path is taken, the wrong path is invalidated, thereby avoiding any resource utilization in redirection. In this manner, the FCBI may be executed more quickly or efficiently because certain data elements, such as the conditional code, are invalidated. Accordingly, certain embodiments improve computational inefficiencies, enhance performance of complex computational workloads with certain branches, and reduce or altogether eliminate pipeline stall and flushing for certain workloads.