From aadb5f5adbdb650c5cdc5ece939aaa30af91b3bc Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Mon, 16 Aug 2010 15:31:45 +0000
Subject: [PATCH] Specialize FoldingSetTrait<SCEV>, providing implementations
 of node comparison and hash computation which don't require constructing
 temporary ID values.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111131 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/Analysis/ScalarEvolution.h | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index b0848491901..c2cfd385ce1 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -45,12 +45,16 @@ namespace llvm {
   class LoopInfo;
   class Operator;
   class SCEVUnknown;
+  class SCEV;
+  template<> class FoldingSetTrait<SCEV>;
 
   /// SCEV - This class represents an analyzed expression in the program.  These
   /// are opaque objects that the client is not allowed to do much with
   /// directly.
   ///
   class SCEV : public FoldingSetNode {
+    friend class FoldingSetTrait<SCEV>;
+
     /// FastID - A reference to an Interned FoldingSetNodeID for this node.
     /// The ScalarEvolution's BumpPtrAllocator holds the data.
     FoldingSetNodeIDRef FastID;
@@ -74,9 +78,6 @@ namespace llvm {
 
     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;
@@ -126,6 +127,21 @@ namespace llvm {
     void dump() const;
   };
 
+  // Specialize FoldingSetTrait for SCEV to avoid needing to compute
+  // temporary FoldingSetNodeID values.
+  template<> struct FoldingSetTrait<SCEV> : DefaultFoldingSetTrait<SCEV> {
+    static void Profile(const SCEV &X, FoldingSetNodeID& ID) {
+      ID = X.FastID;
+    }
+    static bool Equals(const SCEV &X, const FoldingSetNodeID &ID,
+                       FoldingSetNodeID &TempID) {
+      return ID == X.FastID;
+    }
+    static unsigned ComputeHash(const SCEV &X, FoldingSetNodeID &TempID) {
+      return X.FastID.ComputeHash();
+    }
+  };
+
   inline raw_ostream &operator<<(raw_ostream &OS, const SCEV &S) {
     S.print(OS);
     return OS;
-- 
2.34.1