[LLVMdev] doc about llvm JIT

[Shukang Zhou]

Hi,

I am interested in the JIT compiler of llvm, namely, lli. I want to know
more about it, but I found little documentation about it. There are a few
paragraphs about JIT in the CGO paper, a list of options dumped from "lli
--help-hidden", and a short webpage of lli in the website. But many issues
are not clearly described. For example,

1. When JIT is available (-force-interpreter=false), under what condition
the JIT compilation will be applied? (Is it applied to any code that is
executed, or just to hot code like Dynamo?)
2. What algorithms are used to identify hot loop regions and hot paths for
runtime reoptimization?
3. How to relate identified executing native code (of hot loops and
regions) back to original LLVM bytecode?
4. What runtime optimizations are applied in the current version?

Would it be possible to provide a more detailed document? If not
convenient, please give us a brief description of files which are in
charge of these functions. I appreciate your effort and time. Thanks.

Shukang Zhou