VLIW Processor Compiled Data Cycle Synchronization
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Solution Overview
Problem
In VLIW processors, the limited instruction-level parallelism and long latency instructions lead to inefficiencies, particularly in applications with large amounts of invalid data, where existing techniques fail to effectively manage multi-cycle no-operation instructions, resulting in suboptimal processing speed.
Innovation Solution
An electronic apparatus and method that identifies multi-cycle no-operation instructions within a cycle corresponding to the latency of a VLIW instruction, updates the compiled data with information on the cycle difference between the end cycles of involved instructions, and synchronizes nop instructions to shorten cycles based on this information, allowing for improved processing speed by adjusting the latency and execution of VLIW instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compiler adds continuous nop instructions to wait for long-latency operations (mul, div) to complete, then the instruction scheduling maintains proper timing, but the processing speed decreases due to unnecessary waiting cycles
Solution Approach 1:
The compiler performs preliminary analysis of data dependencies and operation latencies during code generation, pre-calculating the optimal issue timing for each instruction. This allows the processor to execute instructions at the earliest possible moment without requiring runtime waiting cycles, as the scheduling is optimized in advance based on the instruction latency table and dependency graph analysis.
Solution Approach 2:
The system dynamically adjusts the issue timing of instructions based on real-time processor state and actual completion times of previous operations. The compiler generates flexible scheduling code that can adapt to varying execution conditions, allowing instructions to be issued as soon as their dependencies are satisfied rather than following rigid predetermined slots, thereby eliminating unnecessary nop instructions while maintaining correctness.
2Device complexity
If the processor executes instructions with fixed issue timing and predefined completion points, then the instruction pipeline remains simple and easy to control, but the instruction-level parallelism is limited
Solution Approach 1:
The instruction stream is segmented into multiple instruction packets, each containing a set of independently executable instructions with explicit timing and dependency information. This segmentation allows the processor to handle complex parallel execution patterns while maintaining simple control logic within each packet, as the compiler has already resolved dependencies and timing at the packet level during code generation.
Solution Approach 2:
The system adds a temporal dimension to instruction encoding by incorporating issue time and latency information directly into the instruction packet structure. This allows the processor to execute instructions out of strict sequential order while maintaining control simplicity, as the extended instruction format carries all necessary timing and dependency information needed for correct execution without requiring complex control logic.
3Productivity
If the compiler maximizes instruction-level parallelism through aggressive scheduling, then the processing throughput increases, but the compilation complexity and time increase
Solution Approach 1:
The compiler performs preliminary construction of a dependency graph and latency analysis table during code generation, organizing all instructions and their relationships in advance. This preliminary structuring enables efficient scheduling decisions to be made systematically rather than through complex iterative optimization, achieving high instruction-level parallelism through methodical pre-computation of timing and dependency information for all instructions.
Solution Approach 2:
The compiler applies scheduling optimization selectively to critical paths and long-latency operations (such as mul and div instructions) rather than attempting to optimize every instruction equally. By focusing computational effort on the instructions that most impact throughput, the system achieves high processing throughput without the excessive compilation complexity that would result from exhaustive optimization of all instructions.
Data Source
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AI summary
An electronic apparatus generating compiled data used in a very long instruction word (VLIW) processor including a plurality of function units is provided. The electronic apparatus includes a storage and a processor configured to control the storage to store the compiled data in which a plurality of VLIW instructions are compiled, identify a VLIW instruction from the compiled data; and update, if a multi-cycle no operation (nop) instruction for the plurality of function units is identified within a cycle corresponding to a latency of the identified VLIW instruction and if an end cycle of another VLIW instruction is within the cycle corresponding to the latency of the identified VLIW instruction, the compiled data by including information on a cycle difference between an end cycle of the identified VLIW instruction and the end cycle of the another VLIW instruction in the multi-cycle nop instruction.