[clang][dataflow][NFC] Eliminate `getStorageLocation()` / `setStorageLocation()` in `DataflowAnalysisContext`.

[mboehme]

Summary

Instead, inline them into the getStableStorageLocation() overloads, which is the only place they were called from (and should be called from).

getStorageLocation() / setStorageLocation() were confusing because neither their name nor their documentation made reference to the fact that the storage location is stable.

It didn't make sense to keep these as private member functions either. The code for the two getStableStorageLocation() overloads has become only marginally more complex by inlining these functions, and the Expr version is actually more efficient because we only call ignoreCFGOmittedNodes() once instead of twice.

[ymandel]

I love this! (specifically, that it simplifies the API surface)

clang/include/clang/Analysis/FlowSensitive/DataflowAnalysisContext.h

public:
   StorageLocation &createStorageLocation(QualType Type);
 
   /// Returns a stable storage location for `D`.
   StorageLocation &getStableStorageLocation(const VarDecl &D);
 
   /// Returns a stable storage location for `E`.
   StorageLocation &getStableStorageLocation(const Expr &E);
 
-  /// Assigns `Loc` as the storage location of `D`.
-  ///
-  /// Requirements:
-  ///
-  ///  `D` must not be assigned a storage location.
-  void setStorageLocation(const ValueDecl &D, StorageLocation &Loc) {
-    assert(!DeclToLoc.contains(&D));
-    DeclToLoc[&D] = &Loc;
-  }
-
-  /// Returns the storage location assigned to `D` or null if `D` has no
-  /// assigned storage location.
-  StorageLocation *getStorageLocation(const ValueDecl &D) const {
-    return DeclToLoc.lookup(&D);
-  }
-
-  /// Assigns `Loc` as the storage location of `E`.
-  ///
-  /// Requirements:
-  ///
-  ///  `E` must not be assigned a storage location.
-  void setStorageLocation(const Expr &E, StorageLocation &Loc) {
-    const Expr &CanonE = ignoreCFGOmittedNodes(E);
-    assert(!ExprToLoc.contains(&CanonE));
-    ExprToLoc[&CanonE] = &Loc;
-  }
-
-  /// Returns the storage location assigned to `E` or null if `E` has no
-  /// assigned storage location.
-  StorageLocation *getStorageLocation(const Expr &E) const {
-    return ExprToLoc.lookup(&ignoreCFGOmittedNodes(E));
-  }
-
   /// Returns a pointer value that represents a null pointer. Calls with
   /// `PointeeType` that are canonically equivalent will return the same result.
   /// A null `PointeeType` can be used for the pointee of `std::nullptr_t`.
   PointerValue &getOrCreateNullPointerValue(QualType PointeeType);
 
   /// Adds `Constraint` to the flow condition identified by `Token`.
   void addFlowConditionConstraint(Atom Token, const Formula &Constraint);
 

clang/lib/Analysis/FlowSensitive/DataflowAnalysisContext.cpp

for (const FieldDecl *Field : getModeledFields(Type))
                                      Field->getType().getNonReferenceType())});
     return arena().create<RecordStorageLocation>(Type, std::move(FieldLocs));
   }
   return arena().create<ScalarStorageLocation>(Type);
 }
 
 StorageLocation &
 DataflowAnalysisContext::getStableStorageLocation(const VarDecl &D) {
-  if (auto *Loc = getStorageLocation(D))
+  if (auto *Loc = DeclToLoc.lookup(&D))
     return *Loc;
   auto &Loc = createStorageLocation(D.getType().getNonReferenceType());
-  setStorageLocation(D, Loc);
+  DeclToLoc[&D] = &Loc;
   return Loc;
 }
 
 StorageLocation &
 DataflowAnalysisContext::getStableStorageLocation(const Expr &E) {
-  if (auto *Loc = getStorageLocation(E))
+  const Expr &CanonE = ignoreCFGOmittedNodes(E);
+
+  if (auto *Loc = ExprToLoc.lookup(&CanonE))
     return *Loc;
-  auto &Loc = createStorageLocation(E.getType());
-  setStorageLocation(E, Loc);
+  auto &Loc = createStorageLocation(CanonE.getType());
+  ExprToLoc[&CanonE] = &Loc;
   return Loc;
 }
 
 PointerValue &
 DataflowAnalysisContext::getOrCreateNullPointerValue(QualType PointeeType) {
   auto CanonicalPointeeType =
       PointeeType.isNull() ? PointeeType : PointeeType.getCanonicalType();
   auto Res = NullPointerVals.try_emplace(CanonicalPointeeType, nullptr);