bootstrap: actually allow set debuginfo-level to "line-tables-only"

[klensy]

I've tried to set in config.toml rust.debuginfo-level = "line-tables-only", but ended with:

data did not match any variant of untagged enum StringOrInt for key `rust.debuginfo-level`

Also this PR allows to set line-directives-only for debuginfo in config.toml too.

1. Fixes this. Alternative is remove that Deserialize and use default one:
   

   rust/src/bootstrap/src/core/config/config.rs

   Lines 725 to 728 in 0e682e9

   	// The following is a trimmed version of what serde_derive generates. All parts not relevant
   	// for toml deserialization have been removed. This reduces the binary size and improves
   	// compile time of rustbuild.
   	impl<'de> Deserialize<'de> for $name {

2. Should line-directives-only be added too?

3. I've tried to add test to rust/src/bootstrap/src/core/config/tests.rs:

#[test]
fn rust_debuginfo() {
    assert!(matches!(
        parse("rust.debuginfo-level-rustc = 1").rust_debuginfo_level_rustc,
        DebuginfoLevel::Limited
    ));
    assert!(matches!(
        parse("rust.debuginfo-level-rustc = \"line-tables-only\"").rust_debuginfo_level_rustc,
        DebuginfoLevel::LineTablesOnly
    ));
}

But test passes before that PR too; looks like config parse tests checks something wrong? I mean, that tests check something which isn't actual bootstrap behavior.

[rustbot]

r? @albertlarsan68

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[rustbot]

This PR modifies src/bootstrap/src/core/config.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

[Noratrieb]

Can we make that the default in the compiler profile?

[klensy]

Can we make that the default in the compiler profile?

Maybe? I didn't use profiles.
Currently it's 0 for compiler profile, so changing it will make it slower but will give more debug info, for perf tools too.

[workingjubilee]

I do not think changing it will make the actual compiler that much slower for regular execution, as generally debuginfo is not even mapped in at the same time as most code, nevermind actually contending for cache.

[workingjubilee]

I think we can figure out the default in #123337 as what the compiler contributors think would be best as default is up to them but this part of the change is a matter of the bootstrap code per se.

[albertlarsan68]

LGTM, but I think that we should support all levels that are supported by the compilers that are used

[rustbot]

This PR modifies config.example.toml.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

[klensy]

@rustbot ready

[albertlarsan68]

Thanks for the PR!

[albertlarsan68]

@bors r+

[bors]

📌 Commit 1d929cf has been approved by albertlarsan68

It is now in the queue for this repository.

[bors]

⌛ Testing commit 1d929cf with merge 07d0d7c...

[bors]

☀️ Test successful - checks-actions
Approved by: albertlarsan68
Pushing 07d0d7c to master...

[rust-timer]

Finished benchmarking commit (07d0d7c): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 673.234s -> 672.208s (-0.15%)
Artifact size: 315.21 MiB -> 315.30 MiB (0.03%)