llvm-mca - LLVM Machine Code Analyzer¶
llvm-mca is a performance analysis tool that uses information available in LLVM (e.g. scheduling models) to statically measure the performance of machine code in a specific CPU.
Performance is measured in terms of throughput as well as processor resource consumption. The tool currently works for processors with a backend for which there is a scheduling model available in LLVM.
The main goal of this tool is not just to predict the performance of the code when run on the target, but also help with diagnosing potential performance issues.
Given an assembly code sequence, llvm-mca estimates the Instructions Per Cycle (IPC), as well as hardware resource pressure. The analysis and reporting style were inspired by the IACA tool from Intel.
(llvm-mca detects Intel syntax by the presence of an .intel_syntax directive at the beginning of the input. By default its output syntax matches that of its input.)
Scheduling models are not just used to compute instruction latencies and throughput, but also to understand what processor resources are available and how to simulate them.
