Processor Trace Cache for Control Flow Integrity
Solution Overview
Problem
Modern processors face challenges in optimizing the execution of complex instructions, such as floating-point operations and load/store operations, which require more resources and time, impacting overall throughput and performance, especially in applications like internet, text, and multimedia processing.
Innovation Solution
The implementation of an instruction set architecture that includes packed data instructions and out-of-order execution units, allowing for the execution of multiple data elements in parallel using SIMD technology, and the use of register renaming mechanisms to optimize resource allocation and execution efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If out-of-order execution is employed to execute instructions as input is made available, then instruction throughput is improved, but tracking execution of instructions becomes more complex
Solution Approach 1:
A trace cache is introduced as an intermediary structure between the instruction fetch unit and the execution units. The trace cache stores traces (sequences of instructions) and provides trace information to execution units, enabling out-of-order execution while maintaining simplified tracking through the trace cache's organized structure.
Solution Approach 2:
The system implements feedback mechanisms where execution units provide status information back to the trace cache, which then adjusts the fetching and storage of trace information. This feedback loop enables dynamic adaptation to execution progress while maintaining orderly tracking despite out-of-order execution.
2Productivity
If packed data instructions with SIMD technology are used to execute multiple data elements in parallel, then processing efficiency is improved, but resource allocation becomes more complex
Solution Approach 1:
Multiple data elements are merged into packed data structures that can be processed simultaneously by execution units. The trace cache organizes these packed instructions and manages their execution, consolidating resource management tasks while enabling parallel processing of multiple data elements through SIMD technology.
3Productivity
If register renaming mechanisms are implemented to optimize resource allocation, then execution efficiency is improved, but device complexity increases
Solution Approach 1:
The register file is segmented into multiple parts with different renaming capabilities. The trace cache works with specific register segments, dividing the complex register renaming task into manageable portions that can be handled efficiently without requiring complete renaming of all registers, thus reducing overall complexity while maintaining execution efficiency.
Data Source
AI summary
A processor includes a front end to decode an instruction and pass the instruction to execution units with branch suffix information. The processor further includes execution units to execute the instruction and a retirement unit to retire the instruction. The instruction is to specify an operation to be conditionally executed based upon a branch suffix to identify previous execution. The processor further includes logic to, upon retirement of the instruction, determine the result of a series of branch operations preceding execution of the instruction, compare the result to the branch suffix information, allow execution and retirement of the instruction based on a determination that the result matches the branch suffix information, and generate a fault based on a determination that the result does not match the branch suffix information.