From 69fcae91a4c46af5c13be1618c7592e95597b327 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Tue, 14 Jul 2009 14:34:04 +0000
Subject: [PATCH] Make SCEVCallbackVH::allUsesReplacedWith more thorough in
 removing users from the Scalars map.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75634 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/ScalarEvolution.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 457466f9de5..2b4623cd84f 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -4845,6 +4845,7 @@ void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *) {
   // so that future queries will recompute the expressions using the new
   // value.
   SmallVector<User *, 16> Worklist;
+  SmallPtrSet<User *, 8> Visited;
   Value *Old = getValPtr();
   bool DeleteOld = false;
   for (Value::use_iterator UI = Old->use_begin(), UE = Old->use_end();
@@ -4858,15 +4859,18 @@ void ScalarEvolution::SCEVCallbackVH::allUsesReplacedWith(Value *) {
       DeleteOld = true;
       continue;
     }
+    if (!Visited.insert(U))
+      continue;
     if (PHINode *PN = dyn_cast<PHINode>(U))
       SE->ConstantEvolutionLoopExitValue.erase(PN);
     if (Instruction *I = dyn_cast<Instruction>(U))
       SE->ValuesAtScopes.erase(I);
-    if (SE->Scalars.erase(U))
-      for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
-           UI != UE; ++UI)
-        Worklist.push_back(*UI);
+    SE->Scalars.erase(U);
+    for (Value::use_iterator UI = U->use_begin(), UE = U->use_end();
+         UI != UE; ++UI)
+      Worklist.push_back(*UI);
   }
+  // Delete the Old value if it (indirectly) references itself.
   if (DeleteOld) {
     if (PHINode *PN = dyn_cast<PHINode>(Old))
       SE->ConstantEvolutionLoopExitValue.erase(PN);