--remap-path-prefix: Fix duplicated path components in debuginfo

[michaelwoerister]

This PR fixes an issue with --remap-path-prefix where path components could appear twice in the remapped version of the path (e.g. #78479). The underlying problem was that --remap-path-prefix is often used to map an absolute path to something that looks like a relative path, e.g.:

--remap-path-prefix=/home/calvin/.cargo/registry/src/github.com-1ecc6299db9ec823=crates.io",

and relative paths in debuginfo are interpreted as being relative to the compilation directory. So if Cargo invokes the compiler with /home/calvin/.cargo/registry/src/github.com-1ecc6299db9ec823/some_crate-0.1.0/src/lib.rs as input and /home/calvin/.cargo/registry/src/github.com-1ecc6299db9ec823/some_crate-0.1.0 as the compiler's working directory, then debuginfo will state that the working directory was crates.io/some_crate-0.1.0 and the file is question was crates.io/some_crate-0.1.0/src/lib.rs, which combined gives the path:

crates.io/some_crate-0.1.0/crates.io/some_crate-0.1.0/src/lib.rs

With this PR the compiler will detect this situation and set up debuginfo in LLVM in a way that makes it strip the duplicated path components when emitting DWARF.

The PR also extracts the logic for making remapped paths absolute into a common helper function that is now used by debuginfo too (instead of just during crate metadata generation).

[rust-highfive]

r? @nagisa

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[michaelwoerister]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit 0e4a86f545d8550091c07a262e64967fa3de70af with merge ba1281089ae9e873f5ff73dd7d8eac4a8f460404...

[bors]

☀️ Try build successful - checks-actions
Build commit: ba1281089ae9e873f5ff73dd7d8eac4a8f460404 (ba1281089ae9e873f5ff73dd7d8eac4a8f460404)

[rust-timer]

Queued ba1281089ae9e873f5ff73dd7d8eac4a8f460404 with parent e013f9e, future comparison URL.

[rust-timer]

Finished benchmarking commit (ba1281089ae9e873f5ff73dd7d8eac4a8f460404): comparison url.

Summary:

• Primary benchmarks: 🎉 relevant improvement found
• Secondary benchmarks: no relevant changes found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	0	0	1	0	1
mean2	N/A	N/A	-0.5%	N/A	-0.5%
max	N/A	N/A	-0.5%	N/A	-0.5%

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf -perf-regression

Footnotes

1. number of relevant changes ↩

2. the arithmetic mean of the percent change ↩

[michaelwoerister]

Perf looks good.

[nagisa]

r? rust-lang/compiler

I won't be able to get to reviewing things for the upcoming next couple weeks.

[compiler-errors]

not exactly my wheelhouse, so reassigning

r? rust-lang/compiler

[davidtwco]

@bors r+

[bors]

📌 Commit 0e4a86f545d8550091c07a262e64967fa3de70af has been approved by davidtwco

[bors]

⌛ Testing commit 0e4a86f545d8550091c07a262e64967fa3de70af with merge 5e5d0801988be7475a5df68a44b1ecde2bac7673...

[bors]

💔 Test failed - checks-actions

[michaelwoerister]

It looks like -Z simulate-remapped-rust-src-base does not have an effect if remap-debuginfo = true in config.toml, so the test that failed produces a different output on CI (/rustc/<sha>/foo.rs vs /rustc/<value from simulate-remapped-rust-src-base>/foo.rs). I reverted my changes to that test so that it accepts both versions again.

[michaelwoerister]

@bors r=davidtwco (assuming that test fix does not need a separate review)

[bors]

📌 Commit 6411fef has been approved by davidtwco

[bors]

⌛ Testing commit 6411fef with merge 936eba3...

[bors]

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing 936eba3 to master...

[rust-timer]

Finished benchmarking commit (936eba3): comparison url.

Summary:

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: 🎉 relevant improvements found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	0	0	2	6	2
mean2	N/A	N/A	-0.4%	-4.1%	-0.4%
max	N/A	N/A	-0.4%	-4.7%	-0.4%

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

1. number of relevant changes ↩

2. the arithmetic mean of the percent change ↩