`--enable-debuginfo` does not enable LLVM debug info

[nagisa]

According to this code we only enable LLVM debug-info when --disable-llvm-optimize is set. We should also enable LLVM debug info when --enable-debuginfo is set.

[KalitaAlexey]

What you suggest to do if I need rust debug info, but not need LLVM debug info?

[frewsxcv]

Sort of related #24840

[mrhota]

For future travelers, I came here after reading @nnethercote's blog post about perf testing and profiling: https://blog.mozilla.org/nnethercote/2016/10/14/how-to-speed-up-the-rust-compiler/

At the end he mentioned treating LLVM like a black box because he didn't yet know how to enable debuginfo in LLVM itself. Well, it looks like @nagisa's comment resolves that mystery. Except it looks like the option is actually called --disable-optimize-llvm.

[Mark-Simulacrum]

That option sounds like it disables optimizations, though...

[mrhota]

@Mark-Simulacrum Indeed. And in fact, you can --enable-optimize and --enable-debug for rustc

Perhaps bundling up LLVM debuginfo with LLVM de-optimization is no good.

Maybe --disable-optimize-llvm should merely disable optimized LLVM, and user should specify --enable-llvm-debuginfo independently if desired.

[mrhota]

In configure, it looks like CMAKE_BUILD_TYPE=RelWithDebInfo corresponds to --enable-optimize-llvm and the hypothetical --enable-llvm-debuginfo while CMAKE_BUILD_TYPE=Debug corresponds to --disable-optimize-llvm.

[nnethercote]

Should we file a new issue to make it easier to build LLVM with optimizations and debuginfo?

[mrhota]

@nnethercote I intended to issue a PR referring here, but I'll defer to your judgment.

[nnethercote]

Oh, if you have a PR there's no need for a separate issue. Thank you for doing it!

[mrhota]

Oh, I think I just misunderstood your intention, given the title of this issue is slightly broader in intent than the conclusion I came to with my PR. Well, I'm not sure how to dispose of the two issues. Close this one, maybe?

[mrhota]

@nagisa I added support for llvm debuginfo in a release build via a specific build option in #37742. This issue might be obsolete now. Want to close it?