From df58389ef1fb8373d900975a6a66e4fbe0344f83 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 28 Dec 2009 09:32:10 +0000
Subject: [PATCH] avoid a completely unneeded linear walk.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92221 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/Metadata.h |  2 +-
 lib/VMCore/Metadata.cpp | 21 +++++++++------------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/include/llvm/Metadata.h b/include/llvm/Metadata.h
index 7cfaeafa8f1..1ece55935f9 100644
--- a/include/llvm/Metadata.h
+++ b/include/llvm/Metadata.h
@@ -102,7 +102,7 @@ class MDNode : public MetadataBase, public FoldingSetNode {
   };
   
   // Replace each instance of F from the element list of this node with T.
-  void replaceElement(Value *F, Value *T);
+  void replaceElement(MDNodeElement *Op, Value *NewVal);
 
 protected:
   explicit MDNode(LLVMContext &C, Value *const *Vals, unsigned NumVals,
diff --git a/lib/VMCore/Metadata.cpp b/lib/VMCore/Metadata.cpp
index eddd8b070a6..0a3ddcbbe1b 100644
--- a/lib/VMCore/Metadata.cpp
+++ b/lib/VMCore/Metadata.cpp
@@ -76,11 +76,11 @@ public:
 
 
 void MDNodeElement::deleted() {
-  Parent->replaceElement(this->operator Value*(), 0);
+  Parent->replaceElement(this, 0);
 }
 
 void MDNodeElement::allUsesReplacedWith(Value *NV) {
-  Parent->replaceElement(this->operator Value*(), NV);
+  Parent->replaceElement(this, NV);
 }
 
 
@@ -142,8 +142,10 @@ Value *MDNode::getElement(unsigned i) const {
 
 
 // Replace value from this node's element list.
-void MDNode::replaceElement(Value *From, Value *To) {
-  if (From == To || !getType())
+void MDNode::replaceElement(MDNodeElement *Op, Value *To) {
+  Value *From = *Op;
+  
+  if (From == To)
     return;
 
   LLVMContextImpl *pImpl = getType()->getContext().pImpl;
@@ -151,14 +153,9 @@ void MDNode::replaceElement(Value *From, Value *To) {
   // Remove "this" from the context map.  FoldingSet doesn't have to reprofile
   // this node to remove it, so we don't care what state the operands are in.
   pImpl->MDNodeSet.RemoveNode(this);
-  
-  // Find value. This is a linear search, do something if it consumes 
-  // lot of time. It is possible that to have multiple instances of
-  // From in this MDNode's element list.
-  for (unsigned i = 0, e = getNumElements(); i != e; ++i) {
-    if (Operands[i] == From)
-      Operands[i].set(To, this);
-  }
+
+  // Update the operand.
+  Op->set(To, this);
 
   // Insert updated "this" into the context's folding node set.
   // If a node with same element list already exist then before inserting 
-- 
2.34.1