Index: llvm/trunk/include/llvm/Analysis/MemorySSA.h
===================================================================
--- llvm/trunk/include/llvm/Analysis/MemorySSA.h
+++ llvm/trunk/include/llvm/Analysis/MemorySSA.h
@@ -703,6 +703,7 @@
   ~MemorySSA();
 
   MemorySSAWalker *getWalker();
+  MemorySSAWalker *getSkipSelfWalker();
 
   /// Given a memory Mod/Ref'ing instruction, get the MemorySSA
   /// access associated with it. If passed a basic block gets the memory phi
@@ -830,6 +831,7 @@
 private:
   class ClobberWalkerBase;
   class CachingWalker;
+  class SkipSelfWalker;
   class OptimizeUses;
 
   CachingWalker *getWalkerImpl();
@@ -885,6 +887,7 @@
   // Memory SSA building info
   std::unique_ptr<ClobberWalkerBase> WalkerBase;
   std::unique_ptr<CachingWalker> Walker;
+  std::unique_ptr<SkipSelfWalker> SkipWalker;
   unsigned NextID;
 };
 
Index: llvm/trunk/lib/Analysis/MemorySSA.cpp
===================================================================
--- llvm/trunk/lib/Analysis/MemorySSA.cpp
+++ llvm/trunk/lib/Analysis/MemorySSA.cpp
@@ -994,6 +994,31 @@
   }
 };
 
+class MemorySSA::SkipSelfWalker final : public MemorySSAWalker {
+  ClobberWalkerBase *Walker;
+
+public:
+  SkipSelfWalker(MemorySSA *M, ClobberWalkerBase *W)
+      : MemorySSAWalker(M), Walker(W) {}
+  ~SkipSelfWalker() override = default;
+
+  using MemorySSAWalker::getClobberingMemoryAccess;
+
+  MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA) override;
+  MemoryAccess *getClobberingMemoryAccess(MemoryAccess *MA,
+                                          const MemoryLocation &Loc) override;
+
+  void invalidateInfo(MemoryAccess *MA) override {
+    if (auto *MUD = dyn_cast<MemoryUseOrDef>(MA))
+      MUD->resetOptimized();
+  }
+
+  void verify(const MemorySSA *MSSA) override {
+    MemorySSAWalker::verify(MSSA);
+    Walker->verify(MSSA);
+  }
+};
+
 } // end namespace llvm
 
 void MemorySSA::renameSuccessorPhis(BasicBlock *BB, MemoryAccess *IncomingVal,
@@ -1129,7 +1154,7 @@
 
 MemorySSA::MemorySSA(Function &Func, AliasAnalysis *AA, DominatorTree *DT)
     : AA(AA), DT(DT), F(Func), LiveOnEntryDef(nullptr), Walker(nullptr),
-      NextID(0) {
+      SkipWalker(nullptr), NextID(0) {
   buildMemorySSA();
 }
 
@@ -1467,6 +1492,18 @@
   return Walker.get();
 }
 
+MemorySSAWalker *MemorySSA::getSkipSelfWalker() {
+  if (SkipWalker)
+    return SkipWalker.get();
+
+  if (!WalkerBase)
+    WalkerBase = llvm::make_unique<ClobberWalkerBase>(this, AA, DT);
+
+  SkipWalker = llvm::make_unique<SkipSelfWalker>(this, WalkerBase.get());
+  return SkipWalker.get();
+ }
+
+
 // This is a helper function used by the creation routines. It places NewAccess
 // into the access and defs lists for a given basic block, at the given
 // insertion point.
@@ -2298,6 +2335,17 @@
 }
 
 MemoryAccess *
+MemorySSA::SkipSelfWalker::getClobberingMemoryAccess(MemoryAccess *MA) {
+  return Walker->getClobberingMemoryAccessBase(MA, true);
+}
+
+MemoryAccess *
+MemorySSA::SkipSelfWalker::getClobberingMemoryAccess(MemoryAccess *MA,
+                                                    const MemoryLocation &Loc) {
+  return Walker->getClobberingMemoryAccessBase(MA, Loc);
+}
+
+MemoryAccess *
 DoNothingMemorySSAWalker::getClobberingMemoryAccess(MemoryAccess *MA) {
   if (auto *Use = dyn_cast<MemoryUseOrDef>(MA))
     return Use->getDefiningAccess();