Introduce reference counting for statements and expressions, using it
to allow sharing of nodes. Simplifies some aspects of template
instantiation, and fixes both PR3444 and <rdar://problem/6757457>.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@78450 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Stmt.cpp b/lib/AST/Stmt.cpp
index 668f7ef..a0ef5a6 100644
--- a/lib/AST/Stmt.cpp
+++ b/lib/AST/Stmt.cpp
@@ -43,7 +43,7 @@
 }
 
 const char *Stmt::getStmtClassName() const {
-  return getStmtInfoTableEntry(sClass).Name;
+  return getStmtInfoTableEntry((StmtClass)sClass).Name;
 }
 
 void Stmt::DestroyChildren(ASTContext &C) {
@@ -104,6 +104,20 @@
   return new (C) BreakStmt(BreakLoc);
 }
 
+void SwitchStmt::DoDestroy(ASTContext &Ctx) {
+  // Destroy the SwitchCase statements in this switch. In the normal
+  // case, this loop will merely decrement the reference counts from 
+  // the Retain() calls in addSwitchCase();
+  SwitchCase *SC = FirstCase;
+  while (SC) {
+    SwitchCase *Next = SC->getNextSwitchCase();
+    SC->Destroy(Ctx);
+    SC = Next;
+  }
+  
+  Stmt::DoDestroy(Ctx);
+}
+
 void CompoundStmt::setStmts(ASTContext &C, Stmt **Stmts, unsigned NumStmts) {
   if (this->Body)
     C.Deallocate(Body);
diff --git a/lib/Frontend/PCHReaderStmt.cpp b/lib/Frontend/PCHReaderStmt.cpp
index 6b97e61..3040a52 100644
--- a/lib/Frontend/PCHReaderStmt.cpp
+++ b/lib/Frontend/PCHReaderStmt.cpp
@@ -194,6 +194,10 @@
       PrevSC->setNextSwitchCase(SC);
     else
       S->setSwitchCaseList(SC);
+    
+    // Retain this SwitchCase, since SwitchStmt::addSwitchCase() would
+    // normally retain it (but we aren't calling addSwitchCase).
+    SC->Retain();
     PrevSC = SC;
   }
   return 2;
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 6094e6d..295607b 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -2821,14 +2821,6 @@
 
   NamedDecl *InstantiateCurrentDeclRef(NamedDecl *D);
     
-  // Simple function for cloning expressions.
-  template<typename T> 
-  OwningExprResult Clone(T *E) {
-    assert(!E->isValueDependent() && !E->isTypeDependent() &&
-           "expression is value or type dependent!");
-    return Owned(E->Clone(Context));
-  }
-  
   // Objective-C declarations.
   virtual DeclPtrTy ActOnStartClassInterface(SourceLocation AtInterfaceLoc,
                                              IdentifierInfo *ClassName,
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 021a6ad..1c98fca 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -222,7 +222,8 @@
   if (InstantiatedAssertExpr.isInvalid())
     return 0;
 
-  OwningExprResult Message = SemaRef.Clone(D->getMessage());
+  OwningExprResult Message(SemaRef, D->getMessage());
+  D->getMessage()->Retain();
   Decl *StaticAssert 
     = SemaRef.ActOnStaticAssertDeclaration(D->getLocation(), 
                                            move(InstantiatedAssertExpr),
diff --git a/lib/Sema/SemaTemplateInstantiateExpr.cpp b/lib/Sema/SemaTemplateInstantiateExpr.cpp
index 2e7ed1a..1e97f5f 100644
--- a/lib/Sema/SemaTemplateInstantiateExpr.cpp
+++ b/lib/Sema/SemaTemplateInstantiateExpr.cpp
@@ -57,53 +57,53 @@
 
 Sema::OwningExprResult
 TemplateExprInstantiator::VisitPredefinedExpr(PredefinedExpr *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult
 TemplateExprInstantiator::VisitIntegerLiteral(IntegerLiteral *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult
 TemplateExprInstantiator::VisitFloatingLiteral(FloatingLiteral *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult
 TemplateExprInstantiator::VisitStringLiteral(StringLiteral *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult
 TemplateExprInstantiator::VisitCharacterLiteral(CharacterLiteral *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult 
 TemplateExprInstantiator::VisitImaginaryLiteral(ImaginaryLiteral *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult
 TemplateExprInstantiator::VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult
 TemplateExprInstantiator::VisitCXXNullPtrLiteralExpr(CXXNullPtrLiteralExpr *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult
 TemplateExprInstantiator::VisitGNUNullExpr(GNUNullExpr *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult 
 TemplateExprInstantiator::VisitUnresolvedFunctionNameExpr(
                                               UnresolvedFunctionNameExpr *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult
@@ -706,7 +706,8 @@
                                                   ImplicitValueInitExpr *E) {
   assert(!E->isTypeDependent() && !E->isValueDependent() &&
          "ImplicitValueInitExprs are never dependent");
-  return SemaRef.Clone(E);
+  E->Retain();
+  return SemaRef.Owned(E);
 }
 
 Sema::OwningExprResult 
@@ -1110,7 +1111,7 @@
 
 Sema::OwningExprResult 
 TemplateExprInstantiator::VisitCXXZeroInitValueExpr(CXXZeroInitValueExpr *E) {
-  return SemaRef.Clone(E);
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult 
@@ -1289,7 +1290,7 @@
 //----------------------------------------------------------------------------
 Sema::OwningExprResult 
 TemplateExprInstantiator::VisitObjCStringLiteral(ObjCStringLiteral *E) {
-  return SemaRef.Owned(E->Clone(SemaRef.Context));
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult 
@@ -1314,12 +1315,12 @@
 
 Sema::OwningExprResult 
 TemplateExprInstantiator::VisitObjCSelectorExpr(ObjCSelectorExpr *E) { 
-  return SemaRef.Owned(E->Clone(SemaRef.Context));
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult 
 TemplateExprInstantiator::VisitObjCProtocolExpr(ObjCProtocolExpr *E) { 
-  return SemaRef.Owned(E->Clone(SemaRef.Context));
+  return SemaRef.Owned(E->Retain());
 }
 
 Sema::OwningExprResult