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Make dataflow const-prop handle_switch_int monotonic.

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This commit is contained in:
Camille GILLOT 2023-05-29 10:29:54 +00:00
parent e9990ce89c
commit b8fed2f21c
1 changed files with 11 additions and 8 deletions
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19
compiler/rustc_mir_transform/src/dataflow_const_prop.rs
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@ -257,14 +257,17 @@ impl<'tcx> ValueAnalysis<'tcx> for ConstAnalysis<'_, 'tcx> {
ValueOrPlace::Value(value) => value,
ValueOrPlace::Place(place) => state.get_idx(place, self.map()),
};
let FlatSet::Elem(ScalarTy(scalar, _)) = value else {
// Do nothing if we don't know which branch will be taken.
return TerminatorEdges::SwitchInt { discr, targets };
};
let int = scalar.assert_int();
let choice = int.assert_bits(int.size());
TerminatorEdges::Single(targets.target_for_value(choice))
match value {
// We are branching on uninitialized data, this is UB, treat it as unreachable.
// This allows the set of visited edges to grow monotonically with the lattice.
FlatSet::Bottom => TerminatorEdges::None,
FlatSet::Elem(ScalarTy(scalar, _)) => {
let int = scalar.assert_int();
let choice = int.assert_bits(int.size());
TerminatorEdges::Single(targets.target_for_value(choice))
}
FlatSet::Top => TerminatorEdges::SwitchInt { discr, targets },
}
}
}