diff --git a/llvm/lib/Analysis/MemoryBuiltins.cpp b/llvm/lib/Analysis/MemoryBuiltins.cpp
index 1d27a83..0fc0550 100644
--- a/llvm/lib/Analysis/MemoryBuiltins.cpp
+++ b/llvm/lib/Analysis/MemoryBuiltins.cpp
@@ -385,23 +385,16 @@
 
 SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
   V = V->stripPointerCasts();
+  if (Instruction *I = dyn_cast<Instruction>(V)) {
+    // If we have already seen this instruction, bail out. Cycles can happen in
+    // unreachable code after constant propagation.
+    if (!SeenInsts.insert(I))
+      return unknown();
 
-  if (isa<Instruction>(V) || isa<GEPOperator>(V)) {
-    // return cached value or insert unknown in cache if size of V was not
-    // computed yet in order to avoid recursions in PHis
-    std::pair<CacheMapTy::iterator, bool> CacheVal =
-      CacheMap.insert(std::make_pair(V, unknown()));
-    if (!CacheVal.second)
-      return CacheVal.first->second;
-
-    SizeOffsetType Result;
     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
-      Result = visitGEPOperator(*GEP);
-    else
-      Result = visit(cast<Instruction>(*V));
-    return CacheMap[V] = Result;
+      return visitGEPOperator(*GEP);
+    return visit(*I);
   }
-
   if (Argument *A = dyn_cast<Argument>(V))
     return visitArgument(*A);
   if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
@@ -415,6 +408,8 @@
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
     if (CE->getOpcode() == Instruction::IntToPtr)
       return unknown(); // clueless
+    if (CE->getOpcode() == Instruction::GetElementPtr)
+      return visitGEPOperator(cast<GEPOperator>(*CE));
   }
 
   DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
@@ -548,21 +543,9 @@
   return unknown();
 }
 
-SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode &PHI) {
-  if (PHI.getNumIncomingValues() == 0)
-    return unknown();
-
-  SizeOffsetType Ret = compute(PHI.getIncomingValue(0));
-  if (!bothKnown(Ret))
-    return unknown();
-
-  // verify that all PHI incoming pointers have the same size and offset
-  for (unsigned i = 1, e = PHI.getNumIncomingValues(); i != e; ++i) {
-    SizeOffsetType EdgeData = compute(PHI.getIncomingValue(i));
-    if (!bothKnown(EdgeData) || EdgeData != Ret)
-      return unknown();
-  }
-  return Ret;
+SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
+  // too complex to analyze statically.
+  return unknown();
 }
 
 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {