Re: [PATCH] D13946: Shrink DynTypedNode by one pointer from 40 to 32 bytes (on x86_64).

[Benjamin Kramer via cfe-commits]

bkramer updated this revision to Diff 38023.
bkramer added a comment.

Update casts to avoid potential undefined behavior. Now every pointer goes 
through const void*.


http://reviews.llvm.org/D13946

Files:
  include/clang/AST/ASTTypeTraits.h
  unittests/ASTMatchers/Dynamic/RegistryTest.cpp


Index: unittests/ASTMatchers/Dynamic/RegistryTest.cpp
===================================================================
--- unittests/ASTMatchers/Dynamic/RegistryTest.cpp
+++ unittests/ASTMatchers/Dynamic/RegistryTest.cpp
@@ -455,8 +455,8 @@
   // Polymorphic.
   EXPECT_TRUE(hasCompletion(
       Comps, "hasDescendant(",
-      "Matcher<NestedNameSpecifier|NestedNameSpecifierLoc|QualType|...> "
-      "hasDescendant(Matcher<CXXCtorInitializer|NestedNameSpecifier|"
+      "Matcher<TemplateArgument|NestedNameSpecifier|NestedNameSpecifierLoc|...>"
+      " hasDescendant(Matcher<TemplateArgument|NestedNameSpecifier|"
       "NestedNameSpecifierLoc|...>)"));
 
   CompVector WhileComps = getCompletions("whileStmt", 0);
Index: include/clang/AST/ASTTypeTraits.h
===================================================================
--- include/clang/AST/ASTTypeTraits.h
+++ include/clang/AST/ASTTypeTraits.h
@@ -106,18 +106,25 @@
     }
   };
 
+  /// Check if the given ASTNodeKind identifies a type that offers pointer
+  /// identity. This is useful for the fast path in DynTypedNode.
+  bool hasPointerIdentity() const {
+    return KindId > NKI_LastKindWithoutPointerIdentity;
+  }
+
 private:
   /// \brief Kind ids.
   ///
   /// Includes all possible base and derived kinds.
   enum NodeKindId {
     NKI_None,
-    NKI_CXXCtorInitializer,
     NKI_TemplateArgument,
-    NKI_NestedNameSpecifier,
     NKI_NestedNameSpecifierLoc,
     NKI_QualType,
     NKI_TypeLoc,
+    NKI_LastKindWithoutPointerIdentity = NKI_TypeLoc,
+    NKI_CXXCtorInitializer,
+    NKI_NestedNameSpecifier,
     NKI_Decl,
 #define DECL(DERIVED, BASE) NKI_##DERIVED##Decl,
 #include "clang/AST/DeclNodes.inc"
@@ -238,7 +245,11 @@
   /// Note that this is not supported by all AST nodes. For AST nodes
   /// that don't have a pointer-defined identity inside the AST, this
   /// method returns NULL.
-  const void *getMemoizationData() const { return MemoizationData; }
+  const void *getMemoizationData() const {
+    return NodeKind.hasPointerIdentity()
+               ? *reinterpret_cast<void *const *>(Storage.buffer)
+               : nullptr;
+  }
 
   /// \brief Prints the node to the given output stream.
   void print(llvm::raw_ostream &OS, const PrintingPolicy &PP) const;
@@ -286,18 +297,19 @@
   template <typename T, typename BaseT> struct DynCastPtrConverter {
     static const T *get(ASTNodeKind NodeKind, const char Storage[]) {
       if (ASTNodeKind::getFromNodeKind<T>().isBaseOf(NodeKind))
-        return cast<T>(*reinterpret_cast<BaseT *const *>(Storage));
+        return cast<T>(static_cast<const BaseT *>(
+            *reinterpret_cast<const void *const *>(Storage)));
       return nullptr;
     }
     static const T &getUnchecked(ASTNodeKind NodeKind, const char Storage[]) {
       assert(ASTNodeKind::getFromNodeKind<T>().isBaseOf(NodeKind));
-      return *cast<T>(*reinterpret_cast<BaseT *const *>(Storage));
+      return *cast<T>(static_cast<const BaseT *>(
+          *reinterpret_cast<const void *const *>(Storage)));
     }
     static DynTypedNode create(const BaseT &Node) {
       DynTypedNode Result;
       Result.NodeKind = ASTNodeKind::getFromNode(Node);
-      Result.MemoizationData = &Node;
-      new (Result.Storage.buffer) const BaseT * (&Node);
+      new (Result.Storage.buffer) const void *(&Node);
       return Result;
     }
   };
@@ -311,13 +323,13 @@
     }
     static const T &getUnchecked(ASTNodeKind NodeKind, const char Storage[]) {
       assert(ASTNodeKind::getFromNodeKind<T>().isSame(NodeKind));
-      return **reinterpret_cast<T *const *>(Storage);
+      return *static_cast<const T *>(
+          *reinterpret_cast<const void *const *>(Storage));
     }
     static DynTypedNode create(const T &Node) {
       DynTypedNode Result;
       Result.NodeKind = ASTNodeKind::getFromNodeKind<T>();
-      Result.MemoizationData = &Node;
-      new (Result.Storage.buffer) const T * (&Node);
+      new (Result.Storage.buffer) const void *(&Node);
       return Result;
     }
   };
@@ -336,14 +348,12 @@
     static DynTypedNode create(const T &Node) {
       DynTypedNode Result;
       Result.NodeKind = ASTNodeKind::getFromNodeKind<T>();
-      Result.MemoizationData = nullptr;
       new (Result.Storage.buffer) T(Node);
       return Result;
     }
   };
 
   ASTNodeKind NodeKind;
-  const void *MemoizationData;
 
   /// \brief Stores the data of the node.
   ///
@@ -353,12 +363,9 @@
   /// \c QualTypes, \c NestedNameSpecifierLocs, \c TypeLocs and
   /// \c TemplateArguments on the other hand do not have storage or unique
   /// pointers and thus need to be stored by value.
-  typedef llvm::AlignedCharArrayUnion<
-      Decl *, Stmt *, Type *, NestedNameSpecifier *, CXXCtorInitializer *>
-      KindsByPointer;
-  llvm::AlignedCharArrayUnion<KindsByPointer, TemplateArgument,
-                              NestedNameSpecifierLoc, QualType, TypeLoc>
-      Storage;
+  llvm::AlignedCharArrayUnion<const void *, TemplateArgument,
+                              NestedNameSpecifierLoc, QualType,
+                              TypeLoc> Storage;
 };
 
 template <typename T>

_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits