Processor Preloading Instructions Across Instruction Sets
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Solution Overview
Problem
Conventional processors face inefficiencies when preloading instructions from a different instruction set, requiring mode switches that incur delays and waste cache space, as they incorrectly pre-decode and re-fetch instructions, leading to reduced cache hit rates and performance.
Innovation Solution
A processor executes a preload instruction in one instruction set while pre-decoding the pre-loaded instructions according to a different instruction set using an instruction set preload indicator (ISPI), allowing correct pre-decoding and caching of instructions from a distinct instruction set without switching modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the processor switches instruction set mode to pre-decode instructions, then pre-decoding accuracy is improved, but execution delay increases due to mode switching
Solution Approach 1:
The processor performs pre-decoding of instructions into a target instruction set before actual execution is needed. By pre-decoding instructions into the correct instruction set format in advance, the processor eliminates the need for mode switching during execution, thus maintaining pre-decoding accuracy while avoiding execution delays.
Solution Approach 2:
The patent introduces an instruction set translation mechanism that acts as an intermediary between the current instruction set mode and the target instruction set. This translator converts instructions from the current mode to the target mode without requiring a full mode switch, thereby maintaining decoding accuracy while minimizing execution delay.
2Productivity
If the processor pre-loads instructions from a different instruction set, then cache hit rate is improved, but cache space waste occurs due to incorrect pre-decoding
Solution Approach 1:
The processor pre-loads instructions from a different instruction set into the instruction cache before they are needed for execution. By performing the pre-decoding into the correct target instruction set in advance and storing it in the cache, the processor ensures that when these instructions are fetched, they are already in the correct format, thus improving cache hit rate while preventing cache space waste from incorrect pre-decoding.
3Ease of operation
If the processor executes preload instruction in current mode, then simplicity of operation is maintained, but pre-decoding correctness deteriorates for different instruction sets
Solution Approach 1:
The patent introduces an instruction set translation mechanism that acts as an intermediary between the current instruction set mode and the target instruction set. This translator converts instructions from the current mode to the target mode without requiring a full mode switch, thereby maintaining decoding accuracy while minimizing execution delay.
Solution Approach 2:
The processor dynamically changes the decoding parameters or configuration based on the target instruction set identified in the preload instruction. Instead of switching the entire instruction set mode, the processor adjusts only the necessary decoding parameters to correctly interpret and decode the pre-loaded instructions from the different instruction set, thus maintaining operational simplicity while improving pre-decoding correctness.
Data Source
AI summary
A preload instruction in a first instruction set is executed at a processor. The preload instruction causes the processor to preload one or more instructions into an instruction cache. The pre-loaded instructions are pre-decoded according to a second instruction set that is different from the first instruction set. The preloaded instructions are pre-decoded according to the second instruction set in response to an instruction set preload indicator (ISPI).