From b6135a054d46c00e2ba604e8f509de48e6dcfde6 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Thu, 21 Aug 2008 17:31:45 +0000
Subject: [PATCH] Switch from an O(n) method to an O(1) method for changing
 non-constant operands.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55127 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Bitcode/Reader/BitcodeReader.cpp | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 1151496d1e2..79d863833dd 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -237,17 +237,18 @@ void BitcodeReaderValueList::ResolveConstantForwardRefs() {
     // new value.  If they reference more than one placeholder, update them all
     // at once.
     while (!Placeholder->use_empty()) {
-      User *U = Placeholder->use_back();
+      Value::use_iterator UI = Placeholder->use_begin();
+      
       // If the using object isn't uniqued, just update the operands.  This
       // handles instructions and initializers for global variables.
-      if (!isa<Constant>(U) || isa<GlobalValue>(U)) {
-        U->replaceUsesOfWith(Placeholder, RealVal);
+      if (!isa<Constant>(*UI) || isa<GlobalValue>(*UI)) {
+        UI.getUse().set(RealVal);
         continue;
       }
       
       // Otherwise, we have a constant that uses the placeholder.  Replace that
       // constant with a new constant that has *all* placeholder uses updated.
-      Constant *UserC = cast<Constant>(U);
+      Constant *UserC = cast<Constant>(*UI);
       for (User::op_iterator I = UserC->op_begin(), E = UserC->op_end();
            I != E; ++I) {
         Value *NewOp;