This is related to the RFC on llvm-dev visible at this link:
llvm-mca is an LLVM based performance analysis tool that can be used to
statically measure the performance of code, and to help triage potential
problems with target scheduling models.
llvm-mca uses information which is already 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 an out-of-order
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
Given an assembly code sequence, llvm-mca estimates the IPC (instructions per
cycle), as well as hardware resources pressure. The analysis and reporting style
were mostly inspired by the IACA tool from Intel.
There is an RFC about this tool on llvm-dev.
This review covers two patches:
A first (very small) patch that always enables the generation of processor
resource names in the SubtargetEmitter. Currently, the processor resource names
are only generated for debugging purposes, but are needed by the tool to
generate user friendly reports, so we would like to always generate them.
A second patch with the actual static analysis tool (in llvm/tools).
Once these first two patches are committed, the plan is to keep working on the
tool with the help of the community to address all of the limitations described
by the RFC (which should have been posted on llvm-dev), and find good
solutions/fixes for the design issues described by section "Known design problems".
We hope the community will find this tool useful like we have.
Special thanks to Simon Pilgrim, Filipe Cabecinhas and Greg Bedwell who really
helped me a lot by suggesting improvements and testing the tool.