Auto merge of #97833 - tmiasko:borrowed-locals, r=nagisa

bors · bors · commit 4153a2ec45f7 · 2022-06-12T17:56:54.000Z
Remove duplicated implementations of borrowed locals analysis
diff --git a/compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs b/compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs
@@ -85,13 +85,7 @@ where
         self.super_rvalue(rvalue, location);
 
         match rvalue {
-            mir::Rvalue::AddressOf(_mt, borrowed_place) => {
-                if !borrowed_place.is_indirect() {
-                    self.trans.gen(borrowed_place.local);
-                }
-            }
-
-            mir::Rvalue::Ref(_, _kind, borrowed_place) => {
+            mir::Rvalue::AddressOf(_, borrowed_place) | mir::Rvalue::Ref(_, _, borrowed_place) => {
                 if !borrowed_place.is_indirect() {
                     self.trans.gen(borrowed_place.local);
                 }
@@ -145,3 +139,23 @@ where
         }
     }
 }
+
+/// The set of locals that are borrowed at some point in the MIR body.
+pub fn borrowed_locals(body: &Body<'_>) -> BitSet<Local> {
+    struct Borrowed(BitSet<Local>);
+
+    impl GenKill<Local> for Borrowed {
+        #[inline]
+        fn gen(&mut self, elem: Local) {
+            self.0.gen(elem)
+        }
+        #[inline]
+        fn kill(&mut self, _: Local) {
+            // Ignore borrow invalidation.
+        }
+    }
+
+    let mut borrowed = Borrowed(BitSet::new_empty(body.local_decls.len()));
+    TransferFunction { trans: &mut borrowed }.visit_body(body);
+    borrowed.0
+}
diff --git a/compiler/rustc_mir_dataflow/src/impls/mod.rs b/compiler/rustc_mir_dataflow/src/impls/mod.rs
@@ -23,6 +23,7 @@ mod init_locals;
 mod liveness;
 mod storage_liveness;
 
+pub use self::borrowed_locals::borrowed_locals;
 pub use self::borrowed_locals::MaybeBorrowedLocals;
 pub use self::init_locals::MaybeInitializedLocals;
 pub use self::liveness::MaybeLiveLocals;
diff --git a/compiler/rustc_mir_transform/src/dead_store_elimination.rs b/compiler/rustc_mir_transform/src/dead_store_elimination.rs
@@ -13,16 +13,15 @@
 //!
 
 use rustc_index::bit_set::BitSet;
-use rustc_middle::{
-    mir::{visit::Visitor, *},
-    ty::TyCtxt,
-};
-use rustc_mir_dataflow::{impls::MaybeTransitiveLiveLocals, Analysis};
+use rustc_middle::mir::*;
+use rustc_middle::ty::TyCtxt;
+use rustc_mir_dataflow::impls::{borrowed_locals, MaybeTransitiveLiveLocals};
+use rustc_mir_dataflow::Analysis;
 
 /// Performs the optimization on the body
 ///
 /// The `borrowed` set must be a `BitSet` of all the locals that are ever borrowed in this body. It
-/// can be generated via the [`get_borrowed_locals`] function.
+/// can be generated via the [`borrowed_locals`] function.
 pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, borrowed: &BitSet<Local>) {
     let mut live = MaybeTransitiveLiveLocals::new(borrowed)
         .into_engine(tcx, body)
@@ -73,67 +72,6 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, borrowed: &BitS
     }
 }
 
-pub fn get_borrowed_locals(body: &Body<'_>) -> BitSet<Local> {
-    let mut b = BorrowedLocals(BitSet::new_empty(body.local_decls.len()));
-    b.visit_body(body);
-    b.0
-}
-
-struct BorrowedLocals(BitSet<Local>);
-
-impl<'tcx> Visitor<'tcx> for BorrowedLocals {
-    fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, loc: Location) {
-        self.super_rvalue(rvalue, loc);
-        match rvalue {
-            Rvalue::AddressOf(_, borrowed_place) | Rvalue::Ref(_, _, borrowed_place) => {
-                if !borrowed_place.is_indirect() {
-                    self.0.insert(borrowed_place.local);
-                }
-            }
-
-            Rvalue::Cast(..)
-            | Rvalue::ShallowInitBox(..)
-            | Rvalue::Use(..)
-            | Rvalue::Repeat(..)
-            | Rvalue::Len(..)
-            | Rvalue::BinaryOp(..)
-            | Rvalue::CheckedBinaryOp(..)
-            | Rvalue::NullaryOp(..)
-            | Rvalue::UnaryOp(..)
-            | Rvalue::Discriminant(..)
-            | Rvalue::Aggregate(..)
-            | Rvalue::ThreadLocalRef(..) => {}
-        }
-    }
-
-    fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
-        self.super_terminator(terminator, location);
-
-        match terminator.kind {
-            TerminatorKind::Drop { place: dropped_place, .. } => {
-                if !dropped_place.is_indirect() {
-                    self.0.insert(dropped_place.local);
-                }
-            }
-
-            TerminatorKind::Abort
-            | TerminatorKind::DropAndReplace { .. }
-            | TerminatorKind::Assert { .. }
-            | TerminatorKind::Call { .. }
-            | TerminatorKind::FalseEdge { .. }
-            | TerminatorKind::FalseUnwind { .. }
-            | TerminatorKind::GeneratorDrop
-            | TerminatorKind::Goto { .. }
-            | TerminatorKind::Resume
-            | TerminatorKind::Return
-            | TerminatorKind::SwitchInt { .. }
-            | TerminatorKind::Unreachable
-            | TerminatorKind::Yield { .. }
-            | TerminatorKind::InlineAsm { .. } => {}
-        }
-    }
-}
-
 pub struct DeadStoreElimination;
 
 impl<'tcx> MirPass<'tcx> for DeadStoreElimination {
@@ -142,7 +80,7 @@ impl<'tcx> MirPass<'tcx> for DeadStoreElimination {
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        let borrowed = get_borrowed_locals(body);
+        let borrowed = borrowed_locals(body);
         eliminate(tcx, body, &borrowed);
     }
 }
diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs
@@ -104,7 +104,7 @@ use rustc_middle::mir::{
     Rvalue, Statement, StatementKind, Terminator, TerminatorKind,
 };
 use rustc_middle::ty::TyCtxt;
-use rustc_mir_dataflow::impls::{MaybeInitializedLocals, MaybeLiveLocals};
+use rustc_mir_dataflow::impls::{borrowed_locals, MaybeInitializedLocals, MaybeLiveLocals};
 use rustc_mir_dataflow::Analysis;
 
 // Empirical measurements have resulted in some observations:
@@ -805,7 +805,7 @@ fn find_candidates<'tcx>(body: &Body<'tcx>) -> Vec<CandidateAssignment<'tcx>> {
     let mut visitor = FindAssignments {
         body,
         candidates: Vec::new(),
-        ever_borrowed_locals: ever_borrowed_locals(body),
+        ever_borrowed_locals: borrowed_locals(body),
         locals_used_as_array_index: locals_used_as_array_index(body),
     };
     visitor.visit_body(body);
@@ -886,69 +886,6 @@ fn is_local_required(local: Local, body: &Body<'_>) -> bool {
     }
 }
 
-/// Walks MIR to find all locals that have their address taken anywhere.
-fn ever_borrowed_locals(body: &Body<'_>) -> BitSet<Local> {
-    let mut visitor = BorrowCollector { locals: BitSet::new_empty(body.local_decls.len()) };
-    visitor.visit_body(body);
-    visitor.locals
-}
-
-struct BorrowCollector {
-    locals: BitSet<Local>,
-}
-
-impl<'tcx> Visitor<'tcx> for BorrowCollector {
-    fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
-        self.super_rvalue(rvalue, location);
-
-        match rvalue {
-            Rvalue::AddressOf(_, borrowed_place) | Rvalue::Ref(_, _, borrowed_place) => {
-                if !borrowed_place.is_indirect() {
-                    self.locals.insert(borrowed_place.local);
-                }
-            }
-
-            Rvalue::Cast(..)
-            | Rvalue::ShallowInitBox(..)
-            | Rvalue::Use(..)
-            | Rvalue::Repeat(..)
-            | Rvalue::Len(..)
-            | Rvalue::BinaryOp(..)
-            | Rvalue::CheckedBinaryOp(..)
-            | Rvalue::NullaryOp(..)
-            | Rvalue::UnaryOp(..)
-            | Rvalue::Discriminant(..)
-            | Rvalue::Aggregate(..)
-            | Rvalue::ThreadLocalRef(..) => {}
-        }
-    }
-
-    fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
-        self.super_terminator(terminator, location);
-
-        match terminator.kind {
-            TerminatorKind::Drop { place: dropped_place, .. }
-            | TerminatorKind::DropAndReplace { place: dropped_place, .. } => {
-                self.locals.insert(dropped_place.local);
-            }
-
-            TerminatorKind::Abort
-            | TerminatorKind::Assert { .. }
-            | TerminatorKind::Call { .. }
-            | TerminatorKind::FalseEdge { .. }
-            | TerminatorKind::FalseUnwind { .. }
-            | TerminatorKind::GeneratorDrop
-            | TerminatorKind::Goto { .. }
-            | TerminatorKind::Resume
-            | TerminatorKind::Return
-            | TerminatorKind::SwitchInt { .. }
-            | TerminatorKind::Unreachable
-            | TerminatorKind::Yield { .. }
-            | TerminatorKind::InlineAsm { .. } => {}
-        }
-    }
-}
-
 /// `PlaceElem::Index` only stores a `Local`, so we can't replace that with a full `Place`.
 ///
 /// Collect locals used as indices so we don't generate candidates that are impossible to apply
