Single-Instruction DEFLATE Decoding With CAM-Based Lookup
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Solution Overview
Problem
The complexity of the DEFLATE decoding process results in a high number of CPU instructions, leading to inefficient software execution.
Innovation Solution
A single-instruction DEFLATE decoder is designed to fetch and decode DEFLATE encoded symbols by referencing tabular information, including a literal/length table and a distance table, to efficiently process and return original information, incrementing the pointer to decode the entire stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional multi-instruction DEFLATE decoding is used, then decoding accuracy is maintained, but CPU instruction count increases and processing efficiency decreases
Solution Approach 1:
The patent combines multiple decoding operations (literal decoding, length decoding, distance decoding, and match generation) into a single unified instruction cycle. The execution unit processes complete DEFLATE symbols atomically, merging what traditionally required multiple sequential instructions into one consolidated operation, thereby improving throughput and reducing CPU overhead.
Solution Approach 2:
The patent introduces specialized execution units with dedicated decoding logic and lookup table interfaces as intermediary components between the CPU and the decompression stream. These execution units handle the complex decoding logic in hardware, freeing the main CPU from instruction-level complexity while maintaining accurate DEFLATE decoding.
2Productivity
If software-based DEFLATE decoding is used, then flexibility is maintained, but software footprint increases and execution efficiency decreases
Solution Approach 1:
The patent replaces software-based decoding logic with dedicated hardware execution units that implement DEFLATE decoding logic in circuitry. This substitution eliminates the need for large software footprints while achieving higher processing speeds through hardware-accelerated lookup table operations and parallel decoding paths.
Solution Approach 2:
The patent uses lookup tables that contain pre-computed decoding information for all possible DEFLATE symbol types. By copying decoded values directly from these tables during execution, the system avoids complex computational logic in software, reducing both software footprint and execution time while maintaining decoding accuracy.
3Reliability
If comprehensive DEFLATE decoding logic is implemented, then decoding accuracy is ensured, but CPU usage increases
Solution Approach 1:
The execution units are designed to autonomously handle the complete decoding process without requiring extensive CPU intervention. The units self-manage lookup table access, symbol type identification, and decoded value generation, ensuring accurate decoding while minimizing CPU cycle consumption through self-contained operation.
Solution Approach 2:
The patent pre-organizes decoding logic and lookup tables during system initialization or fabrication, preparing all necessary decoding information in advance. This preliminary action allows the execution units to perform accurate decoding operations without requiring complex real-time CPU processing, thereby reducing active CPU usage during decompression.
Data Source
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AI summary
A processor is described that includes an instruction execution pipeline having an instruction fetch unit to fetch and decode an instruction. The processor also has an execution unit to execute the instruction. The execution unit has a state machine and content addressable memory (CAM) circuitry. The state machine is to receive a pointer to a stream of DEFLATE encoded information, fetch a section of the DEFLATE encoded information and apply the section of the DEFLATE encoded information to the CAM to obtain decoded DEFLATE information