Index: llvm/trunk/include/llvm/CodeGen/LiveRangeEdit.h
===================================================================
--- llvm/trunk/include/llvm/CodeGen/LiveRangeEdit.h
+++ llvm/trunk/include/llvm/CodeGen/LiveRangeEdit.h
@@ -100,7 +100,8 @@
                     SmallVector<LiveInterval*, 8>,
                     SmallPtrSet<LiveInterval*, 8> > ToShrinkSet;
   /// Helper for eliminateDeadDefs.
-  void eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink);
+  void eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink,
+                        AliasAnalysis *AA);
 
   /// MachineRegisterInfo callback to notify when new virtual
   /// registers are created.
@@ -242,7 +243,8 @@
   /// allocator.  These registers should not be split into new intervals
   /// as currently those new intervals are not guaranteed to spill.
   void eliminateDeadDefs(SmallVectorImpl<MachineInstr *> &Dead,
-                         ArrayRef<unsigned> RegsBeingSpilled = None);
+                         ArrayRef<unsigned> RegsBeingSpilled = None,
+                         AliasAnalysis *AA = nullptr);
 
   /// calculateRegClassAndHint - Recompute register class and hint for each new
   /// register.
Index: llvm/trunk/lib/CodeGen/InlineSpiller.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/InlineSpiller.cpp
+++ llvm/trunk/lib/CodeGen/InlineSpiller.cpp
@@ -626,7 +626,7 @@
   if (DeadDefs.empty())
     return;
   DEBUG(dbgs() << "Remat created " << DeadDefs.size() << " dead defs.\n");
-  Edit->eliminateDeadDefs(DeadDefs, RegsToSpill);
+  Edit->eliminateDeadDefs(DeadDefs, RegsToSpill, AA);
 
   // LiveRangeEdit::eliminateDeadDef is used to remove dead define instructions
   // after rematerialization.  To remove a VNI for a vreg from its LiveInterval,
@@ -996,7 +996,7 @@
   // Hoisted spills may cause dead code.
   if (!DeadDefs.empty()) {
     DEBUG(dbgs() << "Eliminating " << DeadDefs.size() << " dead defs\n");
-    Edit->eliminateDeadDefs(DeadDefs, RegsToSpill);
+    Edit->eliminateDeadDefs(DeadDefs, RegsToSpill, AA);
   }
 
   // Finally delete the SnippetCopies.
@@ -1440,7 +1440,7 @@
           RMEnt->RemoveOperand(i - 1);
       }
     }
-    Edit.eliminateDeadDefs(SpillsToRm, None);
+    Edit.eliminateDeadDefs(SpillsToRm, None, AA);
   }
 }
 
Index: llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
+++ llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
@@ -234,7 +234,8 @@
 }
 
 /// Find all live intervals that need to shrink, then remove the instruction.
-void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink) {
+void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink,
+                                     AliasAnalysis *AA) {
   assert(MI->allDefsAreDead() && "Def isn't really dead");
   SlotIndex Idx = LIS.getInstructionIndex(*MI).getRegSlot();
 
@@ -327,11 +328,12 @@
     }
     DEBUG(dbgs() << "Converted physregs to:\t" << *MI);
   } else {
-    // If the dest of MI is an original reg, don't delete the inst. Replace
-    // the dest with a new reg, keep the inst for remat of other siblings.
-    // The inst is saved in LiveRangeEdit::DeadRemats and will be deleted
-    // after all the allocations of the func are done.
-    if (isOrigDef) {
+    // If the dest of MI is an original reg and MI is reMaterializable,
+    // don't delete the inst. Replace the dest with a new reg, and keep
+    // the inst for remat of other siblings. The inst is saved in
+    // LiveRangeEdit::DeadRemats and will be deleted after all the
+    // allocations of the func are done.
+    if (isOrigDef && DeadRemats && TII.isTriviallyReMaterializable(*MI, AA)) {
       LiveInterval &NewLI = createEmptyIntervalFrom(Dest);
       VNInfo *VNI = NewLI.getNextValue(Idx, LIS.getVNInfoAllocator());
       NewLI.addSegment(LiveInterval::Segment(Idx, Idx.getDeadSlot(), VNI));
@@ -361,13 +363,14 @@
 }
 
 void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr *> &Dead,
-                                      ArrayRef<unsigned> RegsBeingSpilled) {
+                                      ArrayRef<unsigned> RegsBeingSpilled,
+                                      AliasAnalysis *AA) {
   ToShrinkSet ToShrink;
 
   for (;;) {
     // Erase all dead defs.
     while (!Dead.empty())
-      eliminateDeadDef(Dead.pop_back_val(), ToShrink);
+      eliminateDeadDef(Dead.pop_back_val(), ToShrink, AA);
 
     if (ToShrink.empty())
       break;
Index: llvm/trunk/lib/CodeGen/RegAllocGreedy.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/RegAllocGreedy.cpp
+++ llvm/trunk/lib/CodeGen/RegAllocGreedy.cpp
@@ -129,6 +129,7 @@
   EdgeBundles *Bundles;
   SpillPlacement *SpillPlacer;
   LiveDebugVariables *DebugVars;
+  AliasAnalysis *AA;
 
   // state
   std::unique_ptr<Spiller> SpillerInstance;
@@ -2592,6 +2593,7 @@
   Bundles = &getAnalysis<EdgeBundles>();
   SpillPlacer = &getAnalysis<SpillPlacement>();
   DebugVars = &getAnalysis<LiveDebugVariables>();
+  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
 
   initializeCSRCost();
 
@@ -2600,7 +2602,7 @@
   DEBUG(LIS->dump());
 
   SA.reset(new SplitAnalysis(*VRM, *LIS, *Loops));
-  SE.reset(new SplitEditor(*SA, *LIS, *VRM, *DomTree, *MBFI));
+  SE.reset(new SplitEditor(*SA, *AA, *LIS, *VRM, *DomTree, *MBFI));
   ExtraRegInfo.clear();
   ExtraRegInfo.resize(MRI->getNumVirtRegs());
   NextCascade = 1;
Index: llvm/trunk/lib/CodeGen/SplitKit.h
===================================================================
--- llvm/trunk/lib/CodeGen/SplitKit.h
+++ llvm/trunk/lib/CodeGen/SplitKit.h
@@ -235,6 +235,7 @@
 ///
 class LLVM_LIBRARY_VISIBILITY SplitEditor {
   SplitAnalysis &SA;
+  AliasAnalysis &AA;
   LiveIntervals &LIS;
   VirtRegMap &VRM;
   MachineRegisterInfo &MRI;
@@ -380,8 +381,9 @@
 public:
   /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
   /// Newly created intervals will be appended to newIntervals.
-  SplitEditor(SplitAnalysis &SA, LiveIntervals&, VirtRegMap&,
-              MachineDominatorTree&, MachineBlockFrequencyInfo &);
+  SplitEditor(SplitAnalysis &SA, AliasAnalysis &AA, LiveIntervals&,
+              VirtRegMap&, MachineDominatorTree&,
+              MachineBlockFrequencyInfo &);
 
   /// reset - Prepare for a new split.
   void reset(LiveRangeEdit&, ComplementSpillMode = SM_Partition);
Index: llvm/trunk/lib/CodeGen/SplitKit.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SplitKit.cpp
+++ llvm/trunk/lib/CodeGen/SplitKit.cpp
@@ -338,11 +338,13 @@
 //===----------------------------------------------------------------------===//
 
 /// Create a new SplitEditor for editing the LiveInterval analyzed by SA.
-SplitEditor::SplitEditor(SplitAnalysis &sa, LiveIntervals &lis, VirtRegMap &vrm,
+SplitEditor::SplitEditor(SplitAnalysis &sa, AliasAnalysis &aa,
+                         LiveIntervals &lis, VirtRegMap &vrm,
                          MachineDominatorTree &mdt,
                          MachineBlockFrequencyInfo &mbfi)
-    : SA(sa), LIS(lis), VRM(vrm), MRI(vrm.getMachineFunction().getRegInfo()),
-      MDT(mdt), TII(*vrm.getMachineFunction().getSubtarget().getInstrInfo()),
+    : SA(sa), AA(aa), LIS(lis), VRM(vrm),
+      MRI(vrm.getMachineFunction().getRegInfo()), MDT(mdt),
+      TII(*vrm.getMachineFunction().getSubtarget().getInstrInfo()),
       TRI(*vrm.getMachineFunction().getSubtarget().getRegisterInfo()),
       MBFI(mbfi), Edit(nullptr), OpenIdx(0), SpillMode(SM_Partition),
       RegAssign(Allocator) {}
@@ -1130,7 +1132,7 @@
   if (Dead.empty())
     return;
 
-  Edit->eliminateDeadDefs(Dead);
+  Edit->eliminateDeadDefs(Dead, None, &AA);
 }
 
 void SplitEditor::finish(SmallVectorImpl<unsigned> *LRMap) {