Register-Based Variable-Length Decoding With Single-Instruction Decompression
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Solution Overview
Problem
Decoding compressed data, particularly in variable length formats like VARINT, LEB128, and UTF-8, is resource-intensive and inefficient due to the need for numerous shift operations and external memory accesses, which hampers processor performance in multitasking environments.
Innovation Solution
A single machine instruction is introduced that uses onboard registers to decompress variable length data blocks, specifying the format and chunk size, allowing for efficient decoding and next block location determination without external memory references, utilizing multimedia extension registers to store data and decoding state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional decoding methods are used for variable length compressed data, then decoding can be performed, but processor resource usage is high and decoding efficiency is low due to numerous shift operations and external memory accesses
Solution Approach 1:
The patent segments the decoding process into distinct stages: loading compressed data blocks into register pairs, executing decode instructions that operate on these registers, and managing state information in separate registers. This segmentation allows the decoder to work with data in chunks rather than processing byte-by-byte, reducing the total number of operations required.
Solution Approach 2:
The patent introduces intermediary registers that hold compressed data blocks and state information during decoding. These registers act as intermediaries between the compressed data source and the decoding logic, allowing the processor to manipulate data in larger units and reduce frequent memory accesses. The register pairs serve as temporary storage that enables batch processing of variable-length fields.
2Speed
If compressed data is decoded using conventional techniques, then data can be decompressed, but external memory accesses are frequent which slows down the decoding process
Solution Approach 1:
The patent loads entire compressed data blocks into register pairs before decoding begins. This preliminary action of pre-loading data eliminates the need for frequent memory accesses during the actual decoding process. The data is prepared in advance in the register, where it can be manipulated quickly without external memory delays.
Solution Approach 2:
The register pairs serve multiple functions: they hold compressed data blocks, store intermediate decoding results, and manage state information. This multi-functionality reduces the need for additional memory operations, as the same registers are reused throughout the decoding process rather than requiring separate storage locations for each data element.
3Adaptability or versatility
If variable length data is decoded with frequent state saves and retrieves for multitasking, then task switching can occur, but processor resources are consumed and decoding is slowed
Solution Approach 1:
The patent extracts state information into dedicated registers that can be independently managed. By separating the state information from the main decoding logic and placing it in specific registers, the system can save and restore state more efficiently during task switches. This extraction allows the decoder to maintain its position and state without requiring complex memory operations when switching between tasks.
Data Source
AI summary
System and method for decompressing data. A compressed data stream including contiguous variable length data blocks is received, each variable length data block including multiple contiguous variable length data fields. A current data block of the contiguous variable length data blocks is stored in one or more registers of a processor. Decoding state information is stored in another register of the processor. A single machine instruction of the processor is loaded. The instruction includes one or more operands corresponding respectively to the one or more registers, and another operand corresponding to the other register, where the other register is further operable as a destination register to store a result of the machine instruction. The instruction is executed to decompress the current data block using the stored decoding state information, including storing the decompressed current data block in the other register. The decompression is repeated for subsequent blocks in the stream.