Add the ability to "intern" FoldingSetNodeID data into a

BumpPtrAllocator-allocated region to allow it to be stored in a more
compact form and to avoid the need for a non-trivial destructor call.

Use this new mechanism in ScalarEvolution instead of
FastFoldingSetNode to avoid leaking memory in the case where a
FoldingSetNodeID uses heap storage, and to reduce overall memory
usage.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98829 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/ScalarEvolution.h

@@ -49,7 +49,11 @@ namespace llvm {
   /// are opaque objects that the client is not allowed to do much with
   /// directly.
   ///
-  class SCEV : public FastFoldingSetNode {
+  class SCEV : public FoldingSetNode {
+    /// FastID - A reference to an Interned FoldingSetNodeID for this node.
+    /// The ScalarEvolution's BumpPtrAllocator holds the data.
+    FoldingSetNodeIDRef FastID;
+
     // The SCEV baseclass this node corresponds to
     const unsigned short SCEVType;
 
@@ -64,11 +68,14 @@ namespace llvm {
   protected:
     virtual ~SCEV();
   public:
-    explicit SCEV(const FoldingSetNodeID &ID, unsigned SCEVTy) :
-      FastFoldingSetNode(ID), SCEVType(SCEVTy), SubclassData(0) {}
+    explicit SCEV(const FoldingSetNodeIDRef ID, unsigned SCEVTy) :
+      FastID(ID), SCEVType(SCEVTy), SubclassData(0) {}
 
     unsigned getSCEVType() const { return SCEVType; }
 
+    /// Profile - FoldingSet support.
+    void Profile(FoldingSetNodeID& ID) { ID = FastID; }
+
     /// isLoopInvariant - Return true if the value of this SCEV is unchanging in
     /// the specified loop.
     virtual bool isLoopInvariant(const Loop *L) const = 0;