coverage: Store coverage source regions as Span until codegen (take 2)
#134497
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This will avoid confusion with actual `Span` spans.
In codegen, a used function with `FunctionCoverageInfo` but no mappings has historically indicated a bug. However, that will no longer be the case after moving some fallible span-processing steps into codegen.
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Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
jieyouxu
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The implementation looks good to me, and I'm in favoring of making this change. Not having a regression test makes me a bit nervous, but unless we are able to minimize an example that we can use as a regression test (i.e. not a full-blown giant project), I don't think that is super actionable. I think we'll need to find out in nightly if anyone runs into the original problem again, because regardless of making this change or not, I think we do want an MCVE for the original ICE. Furthermore, I think the only way we might be able to minimize one is from more examples. EDIT: we now have a synthetic test example.
Just one question.
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Span until codegen (take 2)
jieyouxu
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Dec 19, 2024
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I can confirm that if I backport the new test to the point just after #133418 was merged, and do (We don't know for sure that it's the same error, because llvm-cov's error reporting for malformed data is really bad, but it's good enough to convince me that the test is doing its job.) |
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It's as good as we're going to get, without nudging llvm-cov to produce better diagnostics. |
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🟩 @bors r=jieyouxu |
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…iaskrgr Rollup of 5 pull requests Successful merges: - rust-lang#134463 (compiletest: don't register predefined `MSVC`/`NONMSVC` FileCheck prefixes) - rust-lang#134487 (Add reference annotations for the `coverage` attribute) - rust-lang#134497 (coverage: Store coverage source regions as `Span` until codegen (take 2)) - rust-lang#134502 (Update std libc version to 0.2.169) - rust-lang#134506 (Remove a duplicated check that doesn't do anything anymore.) r? `@ghost` `@rustbot` modify labels: rollup
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…iaskrgr Rollup of 5 pull requests Successful merges: - rust-lang#134463 (compiletest: don't register predefined `MSVC`/`NONMSVC` FileCheck prefixes) - rust-lang#134487 (Add reference annotations for the `coverage` attribute) - rust-lang#134497 (coverage: Store coverage source regions as `Span` until codegen (take 2)) - rust-lang#134502 (Update std libc version to 0.2.169) - rust-lang#134506 (Remove a duplicated check that doesn't do anything anymore.) r? `@ghost` `@rustbot` modify labels: rollup
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…iaskrgr Rollup of 5 pull requests Successful merges: - rust-lang#134463 (compiletest: don't register predefined `MSVC`/`NONMSVC` FileCheck prefixes) - rust-lang#134487 (Add reference annotations for the `coverage` attribute) - rust-lang#134497 (coverage: Store coverage source regions as `Span` until codegen (take 2)) - rust-lang#134502 (Update std libc version to 0.2.169) - rust-lang#134506 (Remove a duplicated check that doesn't do anything anymore.) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#134497 - Zalathar:spans, r=jieyouxu coverage: Store coverage source regions as `Span` until codegen (take 2) This is an attempt to re-land rust-lang#133418: > Historically, coverage spans were converted into line/column coordinates during the MIR instrumentation pass. > This PR moves that conversion step into codegen, so that coverage spans spend most of their time stored as Span instead. > In addition to being conceptually nicer, this also reduces the size of coverage mappings in MIR, because Span is smaller than 4x u32. That PR was reverted by rust-lang#133608, because in some circumstances not covered by our test suite we were emitting coverage metadata that was causing `llvm-cov` to exit with an error (rust-lang#133606). --- The implementation here is *mostly* the same, but adapted for subsequent changes in the relevant code (e.g. rust-lang#134163). I believe that the changes in rust-lang#134163 should be sufficient to prevent the problem that required the original PR to be reverted. But I haven't been able to reproduce the original breakage in a regression test, and the `llvm-cov` error message is extremely unhelpful, so I can't completely rule out the possibility of this breaking again. r? jieyouxu (reviewer of the original PR)
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The original SourceRegion was moved to the llvm backend and made private by rust-lang/rust#134497. We implement our own local version of it to maintain our handling of SourceRegion for coverage properties.
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The original SourceRegion was moved to the llvm backend and made private by rust-lang/rust#134497. We implement our own local version of it to maintain our handling of SourceRegion for coverage properties.
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The original SourceRegion was moved to the llvm backend and made private by rust-lang/rust#134497. We implement our own local version of it to maintain our handling of SourceRegion for coverage properties.
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This is an attempt to re-land #133418:
That PR was reverted by #133608, because in some circumstances not covered by our test suite we were emitting coverage metadata that was causing
llvm-covto exit with an error (#133606).The implementation here is mostly the same, but adapted for subsequent changes in the relevant code (e.g. #134163).
I believe that the changes in #134163 should be sufficient to prevent the problem that required the original PR to be reverted. But I haven't been able to reproduce the original breakage in a regression test, and the
llvm-coverror message is extremely unhelpful, so I can't completely rule out the possibility of this breaking again.r? jieyouxu (reviewer of the original PR)