Instruction Cache Pre-Decoding Repair for Decode Timing
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Solution Overview
Problem
The uncertainty of instruction boundaries in variable-length instruction sets leads to timing issues during instruction decoding and prediction, resulting in long processor cycles and reduced performance.
Innovation Solution
A method involving an ICache with a pre-decoding circuit that determines and repairs pre-decoding information for instruction sub-blocks, ensuring accurate identification of instruction boundaries, thereby reducing timing pressures and improving processor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If pre-decoding is performed to determine instruction boundaries in advance, then timing pressures at decoding and prediction stages are reduced, but the complexity of the decoding system increases due to additional pre-decoding circuits and check/repair mechanisms
Solution Approach 1:
The patent applies preliminary action by performing pre-decoding of instruction boundaries before the main decoding process. The pre-decoding circuit determines whether each sub-block contains an instruction boundary in advance, and this information is stored in the ICache for later use during decoding and prediction stages, thereby reducing timing pressures without requiring complex real-time analysis during execution
Solution Approach 2:
The patent implements feedback through the pre-decoding check circuit that compares the pre-decoding information with the actual instruction boundaries detected during decoding. When discrepancies are found, the pre-decoding repair circuit uses the feedback to correct errors in the pre-decoded information, ensuring accuracy while maintaining the performance benefits of pre-decoding
2Productivity
If instruction boundary detection is performed during decoding stage, then system complexity is kept low, but the operation frequency is reduced due to long processor cycles
Solution Approach 1:
The patent performs instruction boundary detection in advance during the pre-decoding stage before the main decoding process. By determining boundary information beforehand and storing it in the ICache, the system can operate at higher frequencies without increasing the complexity of the main decoding circuit, as the boundary detection is shifted to a preliminary phase
3Speed
If pre-decoding information is stored in ICache to enable fast access, then operation frequency increases, but the reliability of instruction boundary detection decreases due to potential errors in pre-decoded information
Solution Approach 1:
The patent uses feedback mechanisms where the pre-decoding check circuit compares pre-decoded boundary information with actual boundaries detected during decoding. When errors are detected, the pre-decoding repair circuit uses feedback to correct the erroneous information in the ICache, thereby maintaining both high speed and reliability
Solution Approach 2:
The patent applies beforehand cushioning by implementing error correction capabilities in the pre-decoded information stored in the ICache. The pre-decoding repair circuit acts as a safety mechanism that anticipates and corrects potential errors before they affect instruction execution, ensuring reliability while maintaining the speed benefits of cached pre-decoded information
Data Source
AI summary
A method and device for data processing, and a storage medium are provided. The device includes: a pre-decoding circuit configured to: determine a first sub-block of an instruction block stored in an ICache based on a fetch instruction, determine first pre-decoding information of the first sub-block based on position information of the first sub-block; a pre-decoding check circuit configured to: acquire second pre-decoding information of the first sub-block from the ICache, determine a check result corresponding to the first sub-block based on the first pre-decoding information and the second pre-decoding information, when the check result is a first check result, transmit the first check result to a pre-decoding repair circuit; and the pre-decoding repair circuit configured to: repair second pre-decoding information of at least one target sub-block in the instruction block based on the first pre-decoding information, write the repaired second pre-decoding information back into the ICache.