Multi-Mode Register Semantics for Lower Register Pressure
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Solution Overview
Problem
Conventional instruction set architectures (ISAs) are limited by the number of available architectural registers, which restricts software optimizations and instruction-level parallelism due to increased register pressure and memory latency, necessitating complex workarounds and additional overhead.
Innovation Solution
A data processing system with registers organized in multiple semantic modes (queue or stack behavior) that can be selectively enabled or disabled through a control interface, allowing efficient management without requiring specific management instructions, thereby enhancing parallelism and reducing memory latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of architectural registers is increased to reduce register pressure, then the effectiveness of software optimizations improves, but the encoding limitations and instruction format compatibility are violated
Solution Approach 1:
The patent introduces a new dimension to the register system by adding semantic mode attributes to existing registers. Instead of increasing the number of registers, it enriches the functionality of each register by allowing it to operate in different semantic modes (standard, queue, stack), effectively creating a multi-dimensional register space that resolves the contradiction between optimization effectiveness and encoding complexity
Solution Approach 2:
The patent changes the operational parameters of registers by introducing semantic mode switching. Each register can dynamically change its behavior based on its semantic mode, transforming from a simple storage location to a context-aware data structure. This parameter change allows the same physical register to serve multiple purposes without requiring additional register identifiers
2Device complexity
If conventional registers are used with limited availability, then the instruction format remains simple, but register pressure increases forcing frequent spilling to main memory
Solution Approach 1:
The patent enables registers to serve themselves by automatically managing their own data according to their semantic mode. Queue-mode registers automatically enqueue incoming values and dequeue values in FIFO order, while stack-mode registers automatically push and pop values in LIFO order. This self-service capability eliminates the need for explicit spilling and reloading operations, reducing memory overhead while maintaining simple instruction formats
Solution Approach 2:
The patent makes registers universal by enabling them to function in multiple modes (standard, queue, stack) depending on the computational needs. This multi-functionality allows the same limited set of registers to handle various data organization requirements without requiring additional registers or complex spilling mechanisms, thereby reducing memory access overhead
3Productivity
If out-of-order processing with register renaming is used to resolve WAW dependencies, then instruction-level parallelism improves, but the scope of optimizations such as unrolling, pipelining, and hoisting remains limited
Solution Approach 1:
The patent introduces dynamics to the register system by allowing semantic modes to be configured and changed based on optimization opportunities. Registers can dynamically switch between standard, queue, and stack modes to accommodate different optimization techniques such as unrolling, pipelining, and hoisting. This dynamic adaptability extends the scope of optimizations beyond what static register renaming can achieve
Data Source
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AI summary
The present disclosure provides a data processing system (100) and a method (200) carried out by the data processing system. The data processing system comprises a plurality of registers (102), wherein each register (RI, R2, up to Rn), has one or more storage locations organised according to one of a plurality of semantic modes, including a first semantic mode and a second semantic mode; and a control interface (104) configured to selectively enable or disable an extended semantic mode functionality for each of the plurality of registers, such that, when enabled, a corresponding register interprets instructions according to the first semantic mode, and when disabled, a corresponding register interprets instructions according to the second semantic mode.