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Auto merge of #108175 - cjgillot:validate-storage, r=tmiasko

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MIR-Validate StorageLive.

`StorageLive` statements on a local which already has storage is banned by miri.

This check is easy enough, and can detect bugs in MIR opts.
This commit is contained in:
bors 2023-02-27 11:41:41 +00:00
commit 7d782b7ff4
3 changed files with 63 additions and 2 deletions
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22
compiler/rustc_const_eval/src/transform/validate.rs
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@ -755,8 +755,26 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
self.fail(location, format!("explicit `{:?}` is forbidden", kind));
}
}
StatementKind::StorageLive(..)
| StatementKind::StorageDead(..)
StatementKind::StorageLive(local) => {
// We check that the local is not live when entering a `StorageLive` for it.
// Technically, violating this restriction is only UB and not actually indicative
// of not well-formed MIR. This means that an optimization which turns MIR that
// already has UB into MIR that fails this check is not necessarily wrong. However,
// we have no such optimizations at the moment, and so we include this check anyway
// to help us catch bugs. If you happen to write an optimization that might cause
// this to incorrectly fire, feel free to remove this check.
if self.reachable_blocks.contains(location.block) {
self.storage_liveness.seek_before_primary_effect(location);
let locals_with_storage = self.storage_liveness.get();
if locals_with_storage.contains(*local) {
self.fail(
location,
format!("StorageLive({local:?}) which already has storage here"),
);
}
}
}
StatementKind::StorageDead(_)
| StatementKind::Coverage(_)
| StatementKind::ConstEvalCounter
| StatementKind::Nop => {}