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CGU reuse tracking used by incr. comp. testing is inaccurate wrt ThinLTO CGU reuse #119076

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michaelwoerister opened this issue Dec 18, 2023 · 0 comments
Open

CGU reuse tracking used by incr. comp. testing is inaccurate wrt ThinLTO CGU reuse #119076

michaelwoerister opened this issue Dec 18, 2023 · 0 comments
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A-incr-comp Area: Incremental compilation A-testsuite Area: The testsuite used to check the correctness of rustc C-cleanup Category: PRs that clean code up or issues documenting cleanup. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@michaelwoerister
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Since #115964, CGU reuse tracking does not report "post-lto" reuse when the compiler discovers that the cached post-LTO version of a CGU can be re-used during the ThinLTO phase in the LLVM backend.

Due to this some tests in https://github.com/rust-lang/rust/tree/cda4736f1eaad8af6f49388baa9b7e480df8e329/tests/incremental/thinlto state "pre-lto" even though we actually expect the "post-lto" artifacts to be reusable. We should look into

  • restoring accurate reporting for the LLVM backend, and
  • trying to make the tests in question compatible with other backends that don't have ThinLTO.
@michaelwoerister michaelwoerister added C-cleanup Category: PRs that clean code up or issues documenting cleanup. A-testsuite Area: The testsuite used to check the correctness of rustc T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. A-incr-comp Area: Incremental compilation labels Dec 18, 2023
@rustbot rustbot added the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Dec 18, 2023
@michaelwoerister michaelwoerister mentioned this issue Dec 18, 2023
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@saethlin saethlin removed the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Dec 19, 2023
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A-incr-comp Area: Incremental compilation A-testsuite Area: The testsuite used to check the correctness of rustc C-cleanup Category: PRs that clean code up or issues documenting cleanup. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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