Load Mechanism for Vector Processor Memory Access Optimization
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Solution Overview
Problem
Vector processors face inefficiencies in executing full vector length instructions due to mismatched data paths, requiring operations to be broken into subsets and resulting in suboptimal execution of vector lengths not equal to the maximum vector length, leading to increased memory accesses for aligned and unaligned load operations.
Innovation Solution
The mechanism involves a CPU architecture with a fetch/decode unit that decodes VSSE instructions into micro-operations suitable for 256-bit or smaller operations, utilizing a dispatch/execution unit and memory execution unit to perform aligned and unaligned loads efficiently by generating addresses and accessing memory in optimal quantities, with the aid of a Vector Split Register for unaligned operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If VSSE instructions are broken into multiple micro operations for execution on 256-bit data paths, then the processor can execute operations on full vector length instructions, but the number of memory accesses increases and execution efficiency decreases
Solution Approach 1:
The patent segments the 512-bit vector length instruction into two 256-bit micro-operations that can be executed on the existing 256-bit data path. The instruction decoder divides the full vector length instruction into multiple smaller operations, each fitting the execution unit's data path width, thereby enabling execution on hardware with smaller data paths while maintaining support for full vector length instructions.
Solution Approach 2:
The patent executes only the necessary portion of the vector operation based on the actual vector length. When the vector length is less than the maximum, the processor executes a suitably smaller set of operations rather than always executing the full set, optimizing performance by avoiding unnecessary operations while still supporting the full vector length capability.
2Adaptability or versatility
If the processor executes operations on vector lengths not equal to the maximum vector length, then flexibility is improved, but the number of memory accesses increases leading to performance degradation
Solution Approach 1:
The instruction decoder determines the actual vector length and executes only the necessary number of micro-operations corresponding to that length. This partial action approach avoids executing unnecessary operations when the vector length is less than maximum, reducing memory access overhead and improving performance while maintaining flexibility.
3Adaptability or versatility
If aligned and unaligned load operations are performed with traditional decoding, then support for various load types is provided, but the number of memory accesses is suboptimal
Solution Approach 1:
The patent segments load operations into aligned and unaligned categories and applies different decoding strategies for each. Aligned loads are decoded to optimize for their regular memory access patterns, while unaligned loads are decoded to handle their irregular access patterns efficiently, thereby improving overall memory access efficiency while maintaining support for both types.
Data Source
AI summary
A method is disclosed. The method includes scheduling a load operation at least twice the size of a maximum access supported by a memory device, dividing the load operation into a plurality of separate load operation segments having a size equivalent to the maximum access supported by the memory device, and performing each of the plurality of load operation segments. A further method is disclosed where a temporary register is used to minimize the number of memory accesses to support unaligned accesses.