Add llvm debuginfo configure option

[mrhota]

CC @nnethercote @Mark-Simulacrum

We add a new configure option, --enable-llvm-debuginfo, to do exactly what you'd think.

Re: #31033

Fixes #37738

[rust-highfive]

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[nagisa]

There’s at least two things missing:

1. Corresponding changes to rustbuild (src/bootstrap) and build scripts (src/librustc_llvm/build.rs);
2. Possibly debug info generation for llvm wrapers (in src/rustllvm)

[TimNN]

Note that rustbuild already includes support for RelWithDebInfo (since a few days ago, actually).

So the only thing to be done for rustbuild (I think) is to add a line like

("LLVM_DEBUGINFO", self.llvm_release_debuginfo),

here: https://github.com/rust-lang/rust/blob/master/src/bootstrap/config.rs#L342

[mrhota]

@TimNN hmm, should I change the name of the --enable-llvm-debuginfo option? I didn't know anything about rustbuild until just now!

[TimNN]

@mrhota: I'm honestly not sure. When choosing the name for rustbuild, I went with llvm_release_debuginfo because it seemed more accurate: We already had llvm-optimize, which, if not enabled, always included debuginfo, so the new setting is really only applicable whenllvm-optimize is enabled.

So one could argue to use --enable-llvm-release-debuginfo for consistency & accuracy or for --enable-llvm-debuginfo since it's shorter / easier to remember. (Note that for rustbuild, we have a config.toml file and the option is present in the [llvm] section so it's only called release-debuginfo).

I think I would just stay with --enable-llvm-debuginfo.

[mrhota]

@nagisa After glancing through the code, I don't think rustllvm needs any changes. I wouldn't know how or where to make those changes, though, so maybe someone with more expertise should weigh in.

[mrhota]

@TimNN hehe too late! 😄 I decided to go with your name: I agree it's more accurate. Moreover, it seems like maybe we're moving toward deprecating the configure system, so option names there might be less important. /me shrugs.

[mrhota]

cc @alexcrichton I think this is complete, but I might have missed something (esp. in rustbuild). Thoughts?

[alexcrichton]

@bors: r+

Looks great to me, thanks @mrhota!

[bors]

📌 Commit d3574b8 has been approved by alexcrichton

[bors]

⌛ Testing commit d3574b8 with merge 43006fc...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild
Approved by: alexcrichton
Pushing 43006fc to master...

[nnethercote]

Note to anyone following along: the final name chosen for the configure option was --enable-llvm-release-debuginfo.

[nnethercote]

I just tried this option. I'm using configure/make to build, not rustbuild. It's not working, as far as I can tell. I did "make clean", configured with --enable-optimize --enable-debuginfo --enable--llvm-release-debuginfo, rebuilt the compiler. But my profiles of the compiler still lack filenames and line numbers for LLVM functions.

Is there some way I can check the resulting rustc binary for the debuginfo? I'm on Linux.

[TimNN]

@nnethercote: I haven't used the make based system in a long time, however I think that make clean may not clean llvm, so you may want to try and manually remove the llvm build dir.

[mrhota]

@TimNN @nnethercote there is a make clean-llvm command, too. But I don't know if it does what you'd think it does. I just deleted the build dir.

[nnethercote]

Deleting the build dir fixes the problem -- I'm now getting files and line numbers for LLVM in my profiling output. Thanks!