3 files changed, 29 insertions, 0 deletions

diff --git a/llvm/include/llvm/Metadata.h b/llvm/include/llvm/Metadata.h
index 0d438522ab1..7f232a3c986 100644
--- a/llvm/include/llvm/Metadata.h
+++ b/llvm/include/llvm/Metadata.h
@@ -75,6 +75,10 @@ class MDNode : public Value, public FoldingSetNode {
   void operator=(const MDNode &);        // DO NOT IMPLEMENT
   friend class MDNodeOperand;
   friend class LLVMContextImpl;
+  friend struct FoldingSetTrait<MDNode>;
+
+  /// NumOperands - If the MDNode is uniqued cache the hash to speed up lookup.
+  unsigned Hash;
 
   /// NumOperands - This many 'MDNodeOperand' items are co-allocated onto the
   /// end of this MDNode.
diff --git a/llvm/lib/VMCore/LLVMContextImpl.h b/llvm/lib/VMCore/LLVMContextImpl.h
index 1a4bf6d7b44..2252028b156 100644
--- a/llvm/lib/VMCore/LLVMContextImpl.h
+++ b/llvm/lib/VMCore/LLVMContextImpl.h
@@ -194,6 +194,26 @@ struct FunctionTypeKeyInfo {
   }
 };
 
+// Provide a FoldingSetTrait::Equals specialization for MDNode that can use a
+// shortcut to avoid comparing all operands.
+template<> struct FoldingSetTrait<MDNode> : DefaultFoldingSetTrait<MDNode> {
+  static bool Equals(const MDNode &X, const FoldingSetNodeID &ID,
+                     unsigned IDHash, FoldingSetNodeID &TempID) {
+    assert(!X.isNotUniqued() && "Non-uniqued MDNode in FoldingSet?");
+    // First, check if the cached hashes match.  If they don't we can skip the
+    // expensive operand walk.
+    if (X.Hash != IDHash)
+      return false;
+
+    // If they match we have to compare the operands.
+    X.Profile(TempID);
+    return TempID == ID;
+  }
+  static unsigned ComputeHash(const MDNode &X, FoldingSetNodeID &) {
+    return X.Hash; // Return cached hash.
+  }
+};
+
 /// DebugRecVH - This is a CallbackVH used to keep the Scope -> index maps
 /// up to date as MDNodes mutate.  This class is implemented in DebugLoc.cpp.
 class DebugRecVH : public CallbackVH {
diff --git a/llvm/lib/VMCore/Metadata.cpp b/llvm/lib/VMCore/Metadata.cpp
index 55de0dc6515..090b09a4ccd 100644
--- a/llvm/lib/VMCore/Metadata.cpp
+++ b/llvm/lib/VMCore/Metadata.cpp
@@ -250,6 +250,9 @@ MDNode *MDNode::getMDNode(LLVMContext &Context, ArrayRef<Value*> Vals,
   void *Ptr = malloc(sizeof(MDNode)+Vals.size()*sizeof(MDNodeOperand));
   N = new (Ptr) MDNode(Context, Vals, isFunctionLocal);
 
+  // Cache the operand hash.
+  N->Hash = ID.ComputeHash();
+
   // InsertPoint will have been set by the FindNodeOrInsertPos call.
   pImpl->MDNodeSet.InsertNode(N, InsertPoint);
 
@@ -373,6 +376,8 @@ void MDNode::replaceOperand(MDNodeOperand *Op, Value *To) {
     return;
   }
 
+  // Cache the operand hash.
+  Hash = ID.ComputeHash();
   // InsertPoint will have been set by the FindNodeOrInsertPos call.
   pImpl->MDNodeSet.InsertNode(this, InsertPoint);