1 files changed, 122 insertions, 0 deletions
diff --git a/compiler/rustc_mir_dataflow/src/impls/init_locals.rs b/compiler/rustc_mir_dataflow/src/impls/init_locals.rs
new file mode 100644
index 000000000..83ce4c44b
--- /dev/null
+++ b/compiler/rustc_mir_dataflow/src/impls/init_locals.rs
@@ -0,0 +1,122 @@
+//! A less precise version of `MaybeInitializedPlaces` whose domain is entire locals.
+//!
+//! A local will be maybe initialized if *any* projections of that local might be initialized.
+
+use crate::{CallReturnPlaces, GenKill};
+
+use rustc_index::bit_set::BitSet;
+use rustc_middle::mir::visit::{PlaceContext, Visitor};
+use rustc_middle::mir::{self, BasicBlock, Local, Location};
+
+pub struct MaybeInitializedLocals;
+
+impl<'tcx> crate::AnalysisDomain<'tcx> for MaybeInitializedLocals {
+    type Domain = BitSet<Local>;
+
+    const NAME: &'static str = "maybe_init_locals";
+
+    fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
+        // bottom = uninit
+        BitSet::new_empty(body.local_decls.len())
+    }
+
+    fn initialize_start_block(&self, body: &mir::Body<'tcx>, entry_set: &mut Self::Domain) {
+        // Function arguments are initialized to begin with.
+        for arg in body.args_iter() {
+            entry_set.insert(arg);
+        }
+    }
+}
+
+impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeInitializedLocals {
+    type Idx = Local;
+
+    fn statement_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        statement: &mir::Statement<'tcx>,
+        loc: Location,
+    ) {
+        TransferFunction { trans }.visit_statement(statement, loc)
+    }
+
+    fn terminator_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        terminator: &mir::Terminator<'tcx>,
+        loc: Location,
+    ) {
+        TransferFunction { trans }.visit_terminator(terminator, loc)
+    }
+
+    fn call_return_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _block: BasicBlock,
+        return_places: CallReturnPlaces<'_, 'tcx>,
+    ) {
+        return_places.for_each(|place| trans.gen(place.local));
+    }
+
+    /// See `Analysis::apply_yield_resume_effect`.
+    fn yield_resume_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _resume_block: BasicBlock,
+        resume_place: mir::Place<'tcx>,
+    ) {
+        trans.gen(resume_place.local)
+    }
+}
+
+struct TransferFunction<'a, T> {
+    trans: &'a mut T,
+}
+
+impl<T> Visitor<'_> for TransferFunction<'_, T>
+where
+    T: GenKill<Local>,
+{
+    // FIXME: Using `visit_local` here is a bug. For example, on `move _5.field` we mark `_5` as
+    // deinitialized, although clearly it is only partially deinitialized. This analysis is not
+    // actually used anywhere at the moment, so this is not critical, but this does need to be fixed
+    // before it starts being used again.
+    fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
+        use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, NonUseContext};
+        match context {
+            // These are handled specially in `call_return_effect` and `yield_resume_effect`.
+            PlaceContext::MutatingUse(
+                MutatingUseContext::Call
+                | MutatingUseContext::AsmOutput
+                | MutatingUseContext::Yield,
+            ) => {}
+
+            // If it's deinitialized, it's no longer init
+            PlaceContext::MutatingUse(MutatingUseContext::Deinit) => self.trans.kill(local),
+
+            // Otherwise, when a place is mutated, we must consider it possibly initialized.
+            PlaceContext::MutatingUse(_) => self.trans.gen(local),
+
+            // If the local is moved out of, or if it gets marked `StorageDead`, consider it no
+            // longer initialized.
+            PlaceContext::NonUse(NonUseContext::StorageDead)
+            | PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) => self.trans.kill(local),
+
+            // All other uses do not affect this analysis.
+            PlaceContext::NonUse(
+                NonUseContext::StorageLive
+                | NonUseContext::AscribeUserTy
+                | NonUseContext::VarDebugInfo,
+            )
+            | PlaceContext::NonMutatingUse(
+                NonMutatingUseContext::Inspect
+                | NonMutatingUseContext::Copy
+                | NonMutatingUseContext::SharedBorrow
+                | NonMutatingUseContext::ShallowBorrow
+                | NonMutatingUseContext::UniqueBorrow
+                | NonMutatingUseContext::AddressOf
+                | NonMutatingUseContext::Projection,
+            ) => {}
+        }
+    }
+}