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coverage: Explicitly test the coverage maps produced by codegen/LLVM #114843

Merged
merged 3 commits into from
Sep 5, 2023
Merged

coverage: Explicitly test the coverage maps produced by codegen/LLVM #114843

merged 3 commits into from
Sep 5, 2023
+6,395 −6

Commits on Sep 5, 2023

  1. Add tool src/tools/coverage-dump for use by some new coverage tests

    @Zalathar
    Zalathar committed Sep 5, 2023
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  2. Add test suite coverage-map to test coverage mappings emitted by LLVM 

    We compile each test file to LLVM IR assembly, and then pass that IR to a
dedicated program that can decode LLVM coverage maps and print them in a more
human-readable format. We can then check that output against known-good
snapshots.

This test suite has some advantages over the existing `run-coverage` tests:

- We can test coverage instrumentation without needing to run target binaries.

- We can observe subtle improvements/regressions in the underlying coverage
mappings that don't make a visible difference to coverage reports.
    @Zalathar
    Zalathar committed Sep 5, 2023
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  3. Copy most of tests/run-coverage into tests/coverage-map/status-quo 

    The output of these tests is too complicated to comfortably verify by hand, but
we can still use them to observe changes to the underlying mappings produced by
codegen/LLVM.

If these tests fail due to non-coverage changes (e.g. in HIR-to-MIR lowering or
MIR optimizations), it should usually be OK to just `--bless` them, as long as
the `run-coverage` test suite still works.
    @Zalathar
    Zalathar committed Sep 5, 2023
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