Load Instruction Sequence Tracking for Redundant Load Elimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing computer processors face performance limitations due to structural and data hazards from unresolved technical issues in the field of computer processors. Specifically, they fail to efficiently handle redundant tasks such as branch instructions, data hazards, and structural hazards in the field of computer processors. The focus of microarchitectural optimization for memory instructions has been primarily around the faster resolution of data hazards through caching and prefetching. Existing compilers cannot remove such loads because of programmatic limitations such as runtime constants or memory dependence that can't be resolved statically and architectural constraints including program variables far exceeding the number of architectural registers. The execution of such stable loads is redundant, given that both the data and the address are the same, but are necessary to preserve functional correctness in current OoO cores.
Innovation Solution
A vector friendly instruction format is an instruction format that is suited for vector instructions, supporting vector operations with fields specific to vector operations. This format includes fields for specifying the operation and operands, and allows for the elimination of redundant load instructions by detecting stable loads and optimizing their execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If load instructions are executed to preserve functional correctness, then program correctness is maintained, but structural hazards increase due to consumption of Reservation Station entries, AGUs, and Load/Store Buffer entries
Solution Approach 1:
The patent extracts and eliminates redundant load instructions from the instruction sequence by detecting stable loads through tracking data values and addresses. When a load instruction is identified as redundant (same address and data value as previous load), it is removed from execution, thereby reducing structural hazards while preserving program correctness for non-redundant loads
Solution Approach 2:
The patent changes the execution parameter of load instructions by introducing a stability detection mechanism that monitors data values and addresses. Based on this detection, the processor dynamically adjusts whether to execute or eliminate load instructions, transforming the fixed execution behavior into a conditional one that optimizes resource utilization
2Productivity
If stable load instructions are eliminated, then structural hazards are reduced and processor performance improves, but functional correctness may be compromised if elimination is incorrect
Solution Approach 1:
The patent implements feedback mechanisms through tracking structures that monitor data values and addresses of load instructions. The system continuously compares current load parameters with previously executed loads and uses this feedback to accurately determine whether elimination is safe, ensuring functional correctness while enabling performance optimization
Solution Approach 2:
The patent performs preliminary detection and tracking of load instruction characteristics (addresses and data values) before execution decisions are made. By pre-analyzing and recording these parameters in tracking structures, the system ensures that elimination decisions are based on complete information, preventing incorrect elimination that would compromise correctness
3Productivity
If compilers attempt to remove redundant load instructions, then execution efficiency improves, but programmatic limitations prevent removal of runtime constants and memory dependences
Solution Approach 1:
The patent introduces hardware tracking structures as an intermediary between the compiler and the execution units. These tracking structures capture runtime information (data values, addresses) that compilers cannot access statically, enabling the elimination of redundant loads with runtime constants and memory dependences while maintaining compatibility with existing compilation approaches
Data Source
AI summary
An apparatus and method for improving the efficiency of sequences of load instructions. For example, one embodiment of a method comprises: storing, in one or more tracking structures of a memory operations circuit, information related to executed instances of a load instruction, including a loaded data value, a physical address from which the loaded data value was accessed, and a flag to be set to a first value when new instances of the load instruction are to be excluded from execution; detecting a first instance of the load instruction when the flag is set to the first value; and responsively replacing the first instance of the load instruction with a move instruction which, when executed, is to move the loaded data value from a first register to a destination architectural register indicated by the new load instruction.