Overhaul of Stmt allocation:
- Made allocation of Stmt objects using vanilla new/delete a *compiler
  error* by making this new/delete "protected" within class Stmt.
- Now the only way to allocate Stmt objects is by using the new
  operator that takes ASTContext& as an argument.  This ensures that
  all Stmt nodes are allocated from the same (pool) allocator.
- Naturally, these two changes required that *all* creation sites for
  AST nodes use new (ASTContext&).  This is a large patch, but the
  majority of the changes are just this mechanical adjustment.
- The above changes also mean that AST nodes can no longer be
  deallocated using 'delete'.  Instead, one most do
  StmtObject->Destroy(ASTContext&) or do
  ASTContextObject.Deallocate(StmtObject) (the latter not running the
  'Destroy' method).

Along the way I also...
- Made CompoundStmt allocate its array of Stmt* using the allocator in
  ASTContext (previously it used std::vector).  There are a whole
  bunch of other Stmt classes that need to be similarly changed to
  ensure that all memory allocated for ASTs comes from the allocator
  in ASTContext.
- Added a new smart pointer ExprOwningPtr to Sema.h.  This replaces
  the uses of llvm::OwningPtr within Sema, as llvm::OwningPtr used
  'delete' to free memory instead of a Stmt's 'Destroy' method.

Big thanks to Doug Gregor for helping with the acrobatics of making
'new/delete' private and the new smart pointer ExprOwningPtr!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@63997 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 89fdbe3..d686167 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -54,8 +54,8 @@
 }
 
 void StringLiteral::Destroy(ASTContext &C) {
-  C.Deallocate(const_cast<char*>(StrData));
   this->~StringLiteral();
+  C.Deallocate(const_cast<char*>(StrData));
 }
 
 bool UnaryOperator::isPostfix(Opcode Op) {
@@ -104,8 +104,8 @@
 // Postfix Operators.
 //===----------------------------------------------------------------------===//
 
-CallExpr::CallExpr(StmtClass SC, Expr *fn, Expr **args, unsigned numargs, 
-                   QualType t, SourceLocation rparenloc)
+CallExpr::CallExpr(StmtClass SC, Expr *fn, Expr **args,
+                   unsigned numargs, QualType t, SourceLocation rparenloc)
   : Expr(SC, t, 
          fn->isTypeDependent() || hasAnyTypeDependentArguments(args, numargs),
          fn->isValueDependent() || hasAnyValueDependentArguments(args, numargs)),
@@ -133,14 +133,14 @@
 /// setNumArgs - This changes the number of arguments present in this call.
 /// Any orphaned expressions are deleted by this, and any new operands are set
 /// to null.
-void CallExpr::setNumArgs(unsigned NumArgs) {
+void CallExpr::setNumArgs(ASTContext& C, unsigned NumArgs) {
   // No change, just return.
   if (NumArgs == getNumArgs()) return;
   
   // If shrinking # arguments, just delete the extras and forgot them.
   if (NumArgs < getNumArgs()) {
     for (unsigned i = NumArgs, e = getNumArgs(); i != e; ++i)
-      delete getArg(i);
+      getArg(i)->Destroy(C);
     this->NumArgs = NumArgs;
     return;
   }
@@ -154,7 +154,7 @@
   for (unsigned i = getNumArgs()+ARGS_START; i != NumArgs+ARGS_START; ++i)
     NewSubExprs[i] = 0;
   
-  delete[] SubExprs;
+  delete [] SubExprs;
   SubExprs = NewSubExprs;
   this->NumArgs = NumArgs;
 }
@@ -1391,10 +1391,10 @@
   // will iterate over the size expression. However, this expression belongs
   // to the type, not to this, so we don't want to delete it.
   // We still want to delete this expression.
-  // FIXME: Same as in Stmt::Destroy - will be eventually in ASTContext's
-  // pool allocator.
-  if (isArgumentType())
-    delete this;
+  if (isArgumentType()) {
+    this->~SizeOfAlignOfExpr();
+    C.Deallocate(this);
+  }
   else
     Expr::Destroy(C);
 }