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coverage: Restrict ExpressionUsed simplification to Code mappings

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In the future, branch and MC/DC mappings might have expressions that don't
correspond to any single point in the control-flow graph. That makes it
trickier to keep track of which expressions should expect an `ExpressionUsed`
node.

We therefore sidestep that complexity by only performing `ExpressionUsed`
simplification for expressions associated directly with ordinary `Code`
mappings.
This commit is contained in:
Zalathar 2024-07-15 20:32:14 +10:00
parent 741ed01646
commit d4f1f92426
4 changed files with 27 additions and 19 deletions
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11
compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs
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@ -66,8 +66,15 @@ impl<'tcx> FunctionCoverageCollector<'tcx> {
// For each expression ID that is directly used by one or more mappings,
// mark it as not-yet-seen. This indicates that we expect to see a
// corresponding `ExpressionUsed` statement during MIR traversal.
for term in function_coverage_info.mappings.iter().flat_map(|m| m.kind.terms()) {
if let CovTerm::Expression(id) = term {
for mapping in function_coverage_info.mappings.iter() {
// Currently we only worry about ordinary code mappings.
// For branch and MC/DC mappings, expressions might not correspond
// to any particular point in the control-flow graph.
// (Keep this in sync with the injection of `ExpressionUsed`
// statements in the `InstrumentCoverage` MIR pass.)
if let MappingKind::Code(term) = mapping.kind
&& let CovTerm::Expression(id) = term
{
expressions_seen.remove(id);
}
}