Create ConstantExpr class

A ConstantExpr class represents a full expression that's in a context where a
constant expression is required. This class reflects the path the evaluator
took to reach the expression rather than the syntactic context in which the
expression occurs.

In the future, the class will be expanded to cache the result of the evaluated
expression so that it's not needlessly re-evaluated

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D53475

llvm-svn: 345692

Author: isanbard

clang/include/clang/AST/Expr.h

@@ -868,6 +868,64 @@ class Expr : public Stmt {
   }
 };
 
+//===----------------------------------------------------------------------===//
+// Wrapper Expressions.
+//===----------------------------------------------------------------------===//
+
+/// FullExpr - Represents a "full-expression" node.
+class FullExpr : public Expr {
+protected:
+ Stmt *SubExpr;
+
+ FullExpr(StmtClass SC, Expr *subexpr)
+    : Expr(SC, subexpr->getType(),
+           subexpr->getValueKind(), subexpr->getObjectKind(),
+           subexpr->isTypeDependent(), subexpr->isValueDependent(),
+           subexpr->isInstantiationDependent(),
+           subexpr->containsUnexpandedParameterPack()), SubExpr(subexpr) {}
+  FullExpr(StmtClass SC, EmptyShell Empty)
+    : Expr(SC, Empty) {}
+public:
+  const Expr *getSubExpr() const { return cast<Expr>(SubExpr); }
+  Expr *getSubExpr() { return cast<Expr>(SubExpr); }
+
+  /// As with any mutator of the AST, be very careful when modifying an
+  /// existing AST to preserve its invariants.
+  void setSubExpr(Expr *E) { SubExpr = E; }
+
+  static bool classof(const Stmt *T) {
+    return T->getStmtClass() >= firstFullExprConstant &&
+           T->getStmtClass() <= lastFullExprConstant;
+  }
+};
+
+/// ConstantExpr - An expression that occurs in a constant context.
+struct ConstantExpr : public FullExpr {
+  ConstantExpr(Expr *subexpr)
+    : FullExpr(ConstantExprClass, subexpr) {}
+
+  /// Build an empty constant expression wrapper.
+  explicit ConstantExpr(EmptyShell Empty)
+    : FullExpr(ConstantExprClass, Empty) {}
+
+  SourceLocation getBeginLoc() const LLVM_READONLY {
+    return SubExpr->getBeginLoc();
+  }
+  SourceLocation getEndLoc() const LLVM_READONLY {
+    return SubExpr->getEndLoc();
+  }
+
+  static bool classof(const Stmt *T) {
+    return T->getStmtClass() == ConstantExprClass;
+  }
+
+  // Iterators
+  child_range children() { return child_range(&SubExpr, &SubExpr+1); }
+  const_child_range children() const {
+    return const_child_range(&SubExpr, &SubExpr + 1);
+  }
+};
+
 //===----------------------------------------------------------------------===//
 // Primary Expressions.
 //===----------------------------------------------------------------------===//

clang/include/clang/AST/ExprCXX.h

@@ -3031,7 +3031,7 @@ class DependentScopeDeclRefExpr final
 /// potentially-evaluated block literal.  The lifetime of a block
 /// literal is the extent of the enclosing scope.
 class ExprWithCleanups final
-    : public Expr,
+    : public FullExpr,
       private llvm::TrailingObjects<ExprWithCleanups, BlockDecl *> {
 public:
   /// The type of objects that are kept in the cleanup.
@@ -3044,8 +3044,6 @@ class ExprWithCleanups final
   friend class ASTStmtReader;
   friend TrailingObjects;
 
-  Stmt *SubExpr;
-
   ExprWithCleanups(EmptyShell, unsigned NumObjects);
   ExprWithCleanups(Expr *SubExpr, bool CleanupsHaveSideEffects,
                    ArrayRef<CleanupObject> Objects);
@@ -3070,17 +3068,10 @@ class ExprWithCleanups final
     return getObjects()[i];
   }
 
-  Expr *getSubExpr() { return cast<Expr>(SubExpr); }
-  const Expr *getSubExpr() const { return cast<Expr>(SubExpr); }
-
   bool cleanupsHaveSideEffects() const {
     return ExprWithCleanupsBits.CleanupsHaveSideEffects;
   }
 
-  /// As with any mutator of the AST, be very careful
-  /// when modifying an existing AST to preserve its invariants.
-  void setSubExpr(Expr *E) { SubExpr = E; }
-
   SourceLocation getBeginLoc() const LLVM_READONLY {
     return SubExpr->getBeginLoc();
   }

clang/include/clang/AST/RecursiveASTVisitor.h

@@ -2199,6 +2199,8 @@ DEF_TRAVERSE_STMT(ReturnStmt, {})
 DEF_TRAVERSE_STMT(SwitchStmt, {})
 DEF_TRAVERSE_STMT(WhileStmt, {})
 
+DEF_TRAVERSE_STMT(ConstantExpr, {})
+
 DEF_TRAVERSE_STMT(CXXDependentScopeMemberExpr, {
   TRY_TO(TraverseNestedNameSpecifierLoc(S->getQualifierLoc()));
   TRY_TO(TraverseDeclarationNameInfo(S->getMemberNameInfo()));

clang/include/clang/Basic/StmtNodes.td

@@ -93,6 +93,10 @@ def VAArgExpr : DStmt<Expr>;
 def GenericSelectionExpr : DStmt<Expr>;
 def PseudoObjectExpr : DStmt<Expr>;
 
+// Wrapper expressions
+def FullExpr : DStmt<Expr, 1>;
+def ConstantExpr : DStmt<FullExpr>;
+
 // Atomic expressions
 def AtomicExpr : DStmt<Expr>;
 
@@ -131,7 +135,7 @@ def DependentScopeDeclRefExpr : DStmt<Expr>;
 def CXXConstructExpr : DStmt<Expr>;
 def CXXInheritedCtorInitExpr : DStmt<Expr>;
 def CXXBindTemporaryExpr : DStmt<Expr>;
-def ExprWithCleanups : DStmt<Expr>;
+def ExprWithCleanups : DStmt<FullExpr>;
 def CXXTemporaryObjectExpr : DStmt<CXXConstructExpr>;
 def CXXUnresolvedConstructExpr : DStmt<Expr>;
 def CXXDependentScopeMemberExpr : DStmt<Expr>;

clang/include/clang/Serialization/ASTBitCodes.h

@@ -1618,6 +1618,9 @@ namespace serialization {
       /// A MS-style AsmStmt record.
       STMT_MSASM,
 
+      /// A constant expression context.
+      EXPR_CONSTANT,
+
       /// A PredefinedExpr record.
       EXPR_PREDEFINED,
 

clang/lib/ARCMigrate/TransAutoreleasePool.cpp

@@ -403,8 +403,8 @@ class AutoreleasePoolRewriter
     return cast<Expr>(getEssential((Stmt*)E));
   }
   static Stmt *getEssential(Stmt *S) {
-    if (ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(S))
-      S = EWC->getSubExpr();
+    if (FullExpr *FE = dyn_cast<FullExpr>(S))
+      S = FE->getSubExpr();
     if (Expr *E = dyn_cast<Expr>(S))
       S = E->IgnoreParenCasts();
     return S;

clang/lib/ARCMigrate/TransRetainReleaseDealloc.cpp

@@ -253,7 +253,7 @@ class RetainReleaseDeallocRemover :
     }
     while (OuterS && (isa<ParenExpr>(OuterS) ||
                       isa<CastExpr>(OuterS) ||
-                      isa<ExprWithCleanups>(OuterS)));
+                      isa<FullExpr>(OuterS)));
 
     if (!OuterS)
       return std::make_pair(prevStmt, nextStmt);
@@ -376,8 +376,8 @@ class RetainReleaseDeallocRemover :
 
     RecContainer = StmtE;
     Rec = Init->IgnoreParenImpCasts();
-    if (ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(Rec))
-      Rec = EWC->getSubExpr()->IgnoreParenImpCasts();
+    if (FullExpr *FE = dyn_cast<FullExpr>(Rec))
+      Rec = FE->getSubExpr()->IgnoreParenImpCasts();
     RecRange = Rec->getSourceRange();
     if (SM.isMacroArgExpansion(RecRange.getBegin()))
       RecRange.setBegin(SM.getImmediateSpellingLoc(RecRange.getBegin()));

clang/lib/ARCMigrate/TransUnbridgedCasts.cpp

@@ -372,7 +372,7 @@ class UnbridgedCastRewriter : public RecursiveASTVisitor<UnbridgedCastRewriter>{
       Stmt *parent = E;
       do {
         parent = StmtMap->getParentIgnoreParenImpCasts(parent);
-      } while (parent && isa<ExprWithCleanups>(parent));
+      } while (parent && isa<FullExpr>(parent));
 
       if (ReturnStmt *retS = dyn_cast_or_null<ReturnStmt>(parent)) {
         std::string note = "remove the cast and change return type of function "

clang/lib/ARCMigrate/Transforms.cpp

@@ -74,8 +74,8 @@ bool trans::isPlusOneAssign(const BinaryOperator *E) {
 bool trans::isPlusOne(const Expr *E) {
   if (!E)
     return false;
-  if (const ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(E))
-    E = EWC->getSubExpr();
+  if (const FullExpr *FE = dyn_cast<FullExpr>(E))
+    E = FE->getSubExpr();
 
   if (const ObjCMessageExpr *
         ME = dyn_cast<ObjCMessageExpr>(E->IgnoreParenCasts()))

clang/lib/AST/Decl.cpp

@@ -2576,7 +2576,7 @@ Expr *ParmVarDecl::getDefaultArg() {
          "Default argument is not yet instantiated!");
 
   Expr *Arg = getInit();
-  if (auto *E = dyn_cast_or_null<ExprWithCleanups>(Arg))
+  if (auto *E = dyn_cast_or_null<FullExpr>(Arg))
     return E->getSubExpr();
 
   return Arg;