[llvm-dev] Improve hot cold splitting to aggressively outline small blocks

[Ruijie Fang via llvm-dev]

Hello,
I am Ruijie Fang, a GSoC student working on "Improve hot cold
splitting to aggressively outline small blocks." Over the course of
last week, I met with my mentor and co-mentor, Aditya Kumar, and
Rodrigo Rocha, and we made a preliminary plan on improving the
existing hot/cold splitting pass in LLVM through identifying patterns
of cold blocks in real-world workloads via block frequency information
(We have settled to use the PostgreSQL codebase as a workload first,
although if time permits, we will also target other large codebases).

Our project will involve identifying new cold block patterns via
static analysis in our workload,  implementing detection of these
patterns into the existing hot/cold splitting pass, and then
benchmarking hot/cold splitting in our workload to see if there are
improvements. Our eventual goal is to improve the ability of hot/cold
analysis to detect cold blocks in these real-world workloads.

Our plan is attached at
https://docs.google.com/document/d/1rGLcFpfVXnF7aS31dWnowd2y_BjJnRA-hj3cUt6MqZ8/edit?usp=sharing.

Any feedback, input, or suggestion is welcome and highly appreciated!

Best regards,
Ruijie

Ruijie Fang
Email: ruijief at princeton.edu