diff --git a/include/llvm/CodeGen/LiveInterval.h b/include/llvm/CodeGen/LiveInterval.h
index aec21f8..7c44462 100644
--- a/include/llvm/CodeGen/LiveInterval.h
+++ b/include/llvm/CodeGen/LiveInterval.h
@@ -39,25 +39,13 @@
   /// This class holds information about a machine level values, including
   /// definition and use points.
   ///
-  /// Care must be taken in interpreting the def index of the value. The
-  /// following rules apply:
-  ///
-  /// If the isDefAccurate() method returns false then def does not contain the
-  /// index of the defining MachineInstr, or even (necessarily) to a
-  /// MachineInstr at all. In general such a def index is not meaningful
-  /// and should not be used. The exception is that, for values originally
-  /// defined by PHI instructions, after PHI elimination def will contain the
-  /// index of the MBB in which the PHI originally existed. This can be used
-  /// to insert code (spills or copies) which deals with the value, which will
-  /// be live in to the block.
   class VNInfo {
   private:
     enum {
       HAS_PHI_KILL    = 1,
       REDEF_BY_EC     = 1 << 1,
       IS_PHI_DEF      = 1 << 2,
-      IS_UNUSED       = 1 << 3,
-      IS_DEF_ACCURATE = 1 << 4
+      IS_UNUSED       = 1 << 3
     };
 
     MachineInstr *copy;
@@ -73,10 +61,8 @@
     SlotIndex def;
 
     /// VNInfo constructor.
-    /// d is presumed to point to the actual defining instr. If it doesn't
-    /// setIsDefAccurate(false) should be called after construction.
     VNInfo(unsigned i, SlotIndex d, MachineInstr *c)
-      : copy(c), flags(IS_DEF_ACCURATE), id(i), def(d)
+      : copy(c), flags(0), id(i), def(d)
     { }
 
     /// VNInfo construtor, copies values from orig, except for the value number.
@@ -145,16 +131,6 @@
       else
         flags &= ~IS_UNUSED;
     }
-
-    /// Returns true if the def is accurate.
-    bool isDefAccurate() const { return flags & IS_DEF_ACCURATE; }
-    /// Set the "is def accurate" flag on this value.
-    void setIsDefAccurate(bool defAccurate) {
-      if (defAccurate)
-        flags |= IS_DEF_ACCURATE;
-      else
-        flags &= ~IS_DEF_ACCURATE;
-    }
   };
 
   /// LiveRange structure - This represents a simple register range in the
@@ -320,10 +296,9 @@
     /// getNextValue - Create a new value number and return it.  MIIdx specifies
     /// the instruction that defines the value number.
     VNInfo *getNextValue(SlotIndex def, MachineInstr *CopyMI,
-                       bool isDefAccurate, VNInfo::Allocator &VNInfoAllocator) {
+                         VNInfo::Allocator &VNInfoAllocator) {
       VNInfo *VNI =
         new (VNInfoAllocator) VNInfo((unsigned)valnos.size(), def, CopyMI);
-      VNI->setIsDefAccurate(isDefAccurate);
       valnos.push_back(VNI);
       return VNI;
     }
diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp
index b965bfd..12f6d07 100644
--- a/lib/CodeGen/InlineSpiller.cpp
+++ b/lib/CodeGen/InlineSpiller.cpp
@@ -233,8 +233,7 @@
   }
   DEBUG(dbgs() << "\t        " << UseIdx << '\t' << *MI);
 
-  VNInfo *DefVNI = NewLI.getNextValue(DefIdx, 0, true,
-                                       lis_.getVNInfoAllocator());
+  VNInfo *DefVNI = NewLI.getNextValue(DefIdx, 0, lis_.getVNInfoAllocator());
   NewLI.addRange(LiveRange(DefIdx, UseIdx.getDefIndex(), DefVNI));
   DEBUG(dbgs() << "\tinterval: " << NewLI << '\n');
   return true;
@@ -249,7 +248,7 @@
   for (LiveInterval::const_vni_iterator I = li_->vni_begin(),
        E = li_->vni_end(); I != E; ++I) {
     VNInfo *VNI = *I;
-    if (VNI->isUnused() || !VNI->isDefAccurate())
+    if (VNI->isUnused())
       continue;
     MachineInstr *DefMI = lis_.getInstructionFromIndex(VNI->def);
     if (!DefMI || !tii_.isTriviallyReMaterializable(DefMI))
@@ -283,7 +282,7 @@
     lis_.RemoveMachineInstrFromMaps(DefMI);
     vrm_.RemoveMachineInstrFromMaps(DefMI);
     DefMI->eraseFromParent();
-    VNI->setIsDefAccurate(false);
+    VNI->def = lis_.getZeroIndex();
     anyRemoved = true;
   }
 
@@ -366,7 +365,7 @@
   SlotIndex LoadIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
   vrm_.addSpillSlotUse(stackSlot_, MI);
   DEBUG(dbgs() << "\treload:  " << LoadIdx << '\t' << *MI);
-  VNInfo *LoadVNI = NewLI.getNextValue(LoadIdx, 0, true,
+  VNInfo *LoadVNI = NewLI.getNextValue(LoadIdx, 0,
                                        lis_.getVNInfoAllocator());
   NewLI.addRange(LiveRange(LoadIdx, Idx, LoadVNI));
 }
@@ -381,8 +380,7 @@
   SlotIndex StoreIdx = lis_.InsertMachineInstrInMaps(MI).getDefIndex();
   vrm_.addSpillSlotUse(stackSlot_, MI);
   DEBUG(dbgs() << "\tspilled: " << StoreIdx << '\t' << *MI);
-  VNInfo *StoreVNI = NewLI.getNextValue(Idx, 0, true,
-                                        lis_.getVNInfoAllocator());
+  VNInfo *StoreVNI = NewLI.getNextValue(Idx, 0, lis_.getVNInfoAllocator());
   NewLI.addRange(LiveRange(Idx, StoreIdx, StoreVNI));
 }
 
diff --git a/lib/CodeGen/LiveInterval.cpp b/lib/CodeGen/LiveInterval.cpp
index 44101ff..b4f0a94 100644
--- a/lib/CodeGen/LiveInterval.cpp
+++ b/lib/CodeGen/LiveInterval.cpp
@@ -678,10 +678,7 @@
       if (vni->isUnused()) {
         OS << "x";
       } else {
-        if (!vni->isDefAccurate() && !vni->isPHIDef())
-          OS << "?";
-        else
-          OS << vni->def;
+        OS << vni->def;
         if (vni->hasPHIKill())
           OS << "-phikill";
         if (vni->hasRedefByEC())
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index d30596a..c1e8ce5 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -285,8 +285,8 @@
   SlotIndex RedefIndex = MIIdx.getDefIndex();
   const LiveRange *OldLR =
     interval.getLiveRangeContaining(RedefIndex.getUseIndex());
-  if (OldLR->valno->isDefAccurate()) {
-    MachineInstr *DefMI = getInstructionFromIndex(OldLR->valno->def);
+  MachineInstr *DefMI = getInstructionFromIndex(OldLR->valno->def);
+  if (DefMI != 0) {
     return DefMI->findRegisterDefOperandIdx(interval.reg) != -1;
   }
   return false;
@@ -326,8 +326,7 @@
       CopyMI = mi;
     }
 
-    VNInfo *ValNo = interval.getNextValue(defIndex, CopyMI, true,
-                                          VNInfoAllocator);
+    VNInfo *ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator);
     assert(ValNo->id == 0 && "First value in interval is not 0?");
 
     // Loop over all of the blocks that the vreg is defined in.  There are
@@ -393,7 +392,9 @@
       // Create interval with one of a NEW value number.  Note that this value
       // number isn't actually defined by an instruction, weird huh? :)
       if (PHIJoin) {
-        ValNo = interval.getNextValue(Start, 0, false, VNInfoAllocator);
+        assert(getInstructionFromIndex(Start) == 0 &&
+               "PHI def index points at actual instruction.");
+        ValNo = interval.getNextValue(Start, 0, VNInfoAllocator);
         ValNo->setIsPHIDef(true);
       }
       LiveRange LR(Start, killIdx, ValNo);
@@ -439,10 +440,7 @@
 
       // The new value number (#1) is defined by the instruction we claimed
       // defined value #0.
-      VNInfo *ValNo = interval.getNextValue(OldValNo->def, OldValNo->getCopy(),
-                                            false, // update at *
-                                            VNInfoAllocator);
-      ValNo->setFlags(OldValNo->getFlags()); // * <- updating here
+      VNInfo *ValNo = interval.createValueCopy(OldValNo, VNInfoAllocator);
 
       // Value#0 is now defined by the 2-addr instruction.
       OldValNo->def  = RedefIndex;
@@ -480,7 +478,7 @@
       MachineInstr *CopyMI = NULL;
       if (mi->isCopyLike())
         CopyMI = mi;
-      ValNo = interval.getNextValue(defIndex, CopyMI, true, VNInfoAllocator);
+      ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator);
 
       SlotIndex killIndex = getMBBEndIdx(mbb);
       LiveRange LR(defIndex, killIndex, ValNo);
@@ -575,7 +573,7 @@
   LiveInterval::iterator OldLR = interval.FindLiveRangeContaining(start);
   bool Extend = OldLR != interval.end();
   VNInfo *ValNo = Extend
-    ? OldLR->valno : interval.getNextValue(start, CopyMI, true, VNInfoAllocator);
+    ? OldLR->valno : interval.getNextValue(start, CopyMI, VNInfoAllocator);
   if (MO.isEarlyClobber() && Extend)
     ValNo->setHasRedefByEC(true);
   LiveRange LR(start, end, ValNo);
@@ -671,8 +669,11 @@
     }
   }
 
+  SlotIndex defIdx = getMBBStartIdx(MBB);
+  assert(getInstructionFromIndex(defIdx) == 0 &&
+         "PHI def index points at actual instruction.");
   VNInfo *vni =
-    interval.getNextValue(getMBBStartIdx(MBB), 0, false, VNInfoAllocator);
+    interval.getNextValue(defIdx, 0, VNInfoAllocator);
   vni->setIsPHIDef(true);
   LiveRange LR(start, end, vni);
 
@@ -863,9 +864,9 @@
     if (VNI->isUnused())
       continue; // Dead val#.
     // Is the def for the val# rematerializable?
-    if (!VNI->isDefAccurate())
-      return false;
     MachineInstr *ReMatDefMI = getInstructionFromIndex(VNI->def);
+    if (!ReMatDefMI)
+      return false;
     bool DefIsLoad = false;
     if (!ReMatDefMI ||
         !isReMaterializable(li, VNI, ReMatDefMI, SpillIs, DefIsLoad))
@@ -1188,7 +1189,7 @@
     if (HasUse) {
       if (CreatedNewVReg) {
         LiveRange LR(index.getLoadIndex(), index.getDefIndex(),
-                     nI.getNextValue(SlotIndex(), 0, false, VNInfoAllocator));
+                     nI.getNextValue(SlotIndex(), 0, VNInfoAllocator));
         DEBUG(dbgs() << " +" << LR);
         nI.addRange(LR);
       } else {
@@ -1202,7 +1203,7 @@
     }
     if (HasDef) {
       LiveRange LR(index.getDefIndex(), index.getStoreIndex(),
-                   nI.getNextValue(SlotIndex(), 0, false, VNInfoAllocator));
+                   nI.getNextValue(SlotIndex(), 0, VNInfoAllocator));
       DEBUG(dbgs() << " +" << LR);
       nI.addRange(LR);
     }
@@ -1651,8 +1652,7 @@
     if (VNI->isUnused())
       continue; // Dead val#.
     // Is the def for the val# rematerializable?
-    MachineInstr *ReMatDefMI = VNI->isDefAccurate()
-      ? getInstructionFromIndex(VNI->def) : 0;
+    MachineInstr *ReMatDefMI = getInstructionFromIndex(VNI->def);
     bool dummy;
     if (ReMatDefMI && isReMaterializable(li, VNI, ReMatDefMI, SpillIs, dummy)) {
       // Remember how to remat the def of this val#.
@@ -1994,7 +1994,7 @@
   LiveInterval& Interval = getOrCreateInterval(reg);
   VNInfo* VN = Interval.getNextValue(
     SlotIndex(getInstructionIndex(startInst).getDefIndex()),
-    startInst, true, getVNInfoAllocator());
+    startInst, getVNInfoAllocator());
   VN->setHasPHIKill(true);
   LiveRange LR(
      SlotIndex(getInstructionIndex(startInst).getDefIndex()),
diff --git a/lib/CodeGen/PreAllocSplitting.cpp b/lib/CodeGen/PreAllocSplitting.cpp
index cd9d83e..ee228a9 100644
--- a/lib/CodeGen/PreAllocSplitting.cpp
+++ b/lib/CodeGen/PreAllocSplitting.cpp
@@ -324,7 +324,7 @@
   if (CurrSLI->hasAtLeastOneValue())
     CurrSValNo = CurrSLI->getValNumInfo(0);
   else
-    CurrSValNo = CurrSLI->getNextValue(SlotIndex(), 0, false,
+    CurrSValNo = CurrSLI->getNextValue(SlotIndex(), 0,
                                        LSs->getVNInfoAllocator());
   return SS;
 }
@@ -585,7 +585,7 @@
 
   SlotIndex StartIndex = LIs->getMBBStartIdx(MBB);
   VNInfo *RetVNI = Phis[MBB] =
-    LI->getNextValue(SlotIndex(), /*FIXME*/ 0, false,
+    LI->getNextValue(SlotIndex(), /*FIXME*/ 0,
                      LIs->getVNInfoAllocator());
 
   if (!IsIntraBlock) LiveOut[MBB] = RetVNI;
@@ -674,7 +674,7 @@
     DefIdx = DefIdx.getDefIndex();
     
     assert(!DI->isPHI() && "PHI instr in code during pre-alloc splitting.");
-    VNInfo* NewVN = LI->getNextValue(DefIdx, 0, true, Alloc);
+    VNInfo* NewVN = LI->getNextValue(DefIdx, 0, Alloc);
     
     // If the def is a move, set the copy field.
     if (DI->isCopyLike() && DI->getOperand(0).getReg() == LI->reg)
@@ -807,7 +807,8 @@
   MachineBasicBlock& MBB = *RestorePt->getParent();
   
   MachineBasicBlock::iterator KillPt = BarrierMBB->end();
-  if (!ValNo->isDefAccurate() || DefMI->getParent() == BarrierMBB)
+  if (LIs->getInstructionFromIndex(ValNo->def) == 0 ||
+      DefMI->getParent() == BarrierMBB)
     KillPt = findSpillPoint(BarrierMBB, Barrier, NULL, RefsInMBB);
   else
     KillPt = llvm::next(MachineBasicBlock::iterator(DefMI));
@@ -872,7 +873,7 @@
     if (CurrSLI->hasAtLeastOneValue())
       CurrSValNo = CurrSLI->getValNumInfo(0);
     else
-      CurrSValNo = CurrSLI->getNextValue(SlotIndex(), 0, false,
+      CurrSValNo = CurrSLI->getNextValue(SlotIndex(), 0,
                                          LSs->getVNInfoAllocator());
   }
   
@@ -967,8 +968,7 @@
 
   assert(!ValNo->isUnused() && "Val# is defined by a dead def?");
 
-  MachineInstr *DefMI = ValNo->isDefAccurate()
-    ? LIs->getInstructionFromIndex(ValNo->def) : NULL;
+  MachineInstr *DefMI = LIs->getInstructionFromIndex(ValNo->def);
 
   // If this would create a new join point, do not split.
   if (DefMI && createsNewJoin(LR, DefMI->getParent(), Barrier->getParent())) {
@@ -1005,7 +1005,7 @@
   SlotIndex SpillIndex;
   MachineInstr *SpillMI = NULL;
   int SS = -1;
-  if (!ValNo->isDefAccurate()) {
+  if (LIs->getInstructionFromIndex(ValNo->def) == 0) {
     // If we don't know where the def is we must split just before the barrier.
     if ((SpillMI = FoldSpill(LI->reg, RC, 0, Barrier,
                             BarrierMBB, SS, RefsInMBB))) {
@@ -1199,12 +1199,12 @@
       
       // We also don't try to handle the results of PHI joins, since there's
       // no defining instruction to analyze.
-      if (!CurrVN->isDefAccurate() || CurrVN->isUnused()) continue;
+      MachineInstr* DefMI = LIs->getInstructionFromIndex(CurrVN->def);
+      if (!DefMI || CurrVN->isUnused()) continue;
     
       // We're only interested in eliminating cruft introduced by the splitter,
       // is of the form load-use or load-use-store.  First, check that the
       // definition is a load, and remember what stack slot we loaded it from.
-      MachineInstr* DefMI = LIs->getInstructionFromIndex(CurrVN->def);
       int FrameIndex;
       if (!TII->isLoadFromStackSlot(DefMI, FrameIndex)) continue;
       
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index 5c62354..a4fdcfa 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -431,8 +431,7 @@
   unsigned CandReg;
   {
     MachineInstr *CopyMI;
-    if (vni->def != SlotIndex() && vni->isDefAccurate() &&
-        (CopyMI = li_->getInstructionFromIndex(vni->def)) && CopyMI->isCopy())
+    if ((CopyMI = li_->getInstructionFromIndex(vni->def)) && CopyMI->isCopy())
       // Defined by a copy, try to extend SrcReg forward
       CandReg = CopyMI->getOperand(1).getReg();
     else if (TrivCoalesceEnds &&
@@ -800,7 +799,7 @@
   if (SI.hasAtLeastOneValue())
     VNI = SI.getValNumInfo(0);
   else
-    VNI = SI.getNextValue(SlotIndex(), 0, false,
+    VNI = SI.getNextValue(SlotIndex(), 0,
                           ls_->getVNInfoAllocator());
 
   LiveInterval &RI = li_->getInterval(cur->reg);
@@ -984,8 +983,7 @@
   // one, e.g. X86::mov32to32_. These move instructions are not coalescable.
   if (!vrm_->getRegAllocPref(cur->reg) && cur->hasAtLeastOneValue()) {
     VNInfo *vni = cur->begin()->valno;
-    if ((vni->def != SlotIndex()) && !vni->isUnused() &&
-         vni->isDefAccurate()) {
+    if (!vni->isUnused()) {
       MachineInstr *CopyMI = li_->getInstructionFromIndex(vni->def);
       if (CopyMI && CopyMI->isCopy()) {
         unsigned DstSubReg = CopyMI->getOperand(0).getSubReg();
diff --git a/lib/CodeGen/RegAllocPBQP.cpp b/lib/CodeGen/RegAllocPBQP.cpp
index 0db5053..a45ead8 100644
--- a/lib/CodeGen/RegAllocPBQP.cpp
+++ b/lib/CodeGen/RegAllocPBQP.cpp
@@ -1014,7 +1014,7 @@
     vni = stackInterval.getValNumInfo(0);
   else
     vni = stackInterval.getNextValue(
-      SlotIndex(), 0, false, lss->getVNInfoAllocator());
+      SlotIndex(), 0, lss->getVNInfoAllocator());
 
   LiveInterval &rhsInterval = lis->getInterval(spilled->reg);
   stackInterval.MergeRangesInAsValue(rhsInterval, vni);
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index b29ea19..65e21ed 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -218,7 +218,7 @@
         continue;
       LiveInterval &SRLI = li_->getInterval(*SR);
       SRLI.addRange(LiveRange(FillerStart, FillerEnd,
-                              SRLI.getNextValue(FillerStart, 0, true,
+                              SRLI.getNextValue(FillerStart, 0,
                                                 li_->getVNInfoAllocator())));
     }
   }
@@ -267,7 +267,8 @@
       if (BI->valno == BValNo)
         continue;
       // When BValNo is null, we're looking for a dummy clobber-value for a subreg.
-      if (!BValNo && !BI->valno->isDefAccurate() && !BI->valno->getCopy())
+      if (!BValNo && li_->getInstructionFromIndex(BI->valno->def) == 0 &&
+          !BI->valno->getCopy())
         continue;
       if (BI->start <= AI->start && BI->end > AI->start)
         return true;
@@ -351,12 +352,11 @@
   assert(ALR != IntA.end() && "Live range not found!");
   VNInfo *AValNo = ALR->valno;
   // If other defs can reach uses of this def, then it's not safe to perform
-  // the optimization. FIXME: Do isPHIDef and isDefAccurate both need to be
-  // tested?
-  if (AValNo->isPHIDef() || !AValNo->isDefAccurate() ||
-      AValNo->isUnused() || AValNo->hasPHIKill())
-    return false;
+  // the optimization.
   MachineInstr *DefMI = li_->getInstructionFromIndex(AValNo->def);
+  if (AValNo->isPHIDef() || DefMI == 0 || AValNo->isUnused() ||
+      AValNo->hasPHIKill())
+    return false;
   if (!DefMI)
     return false;
   const TargetInstrDesc &TID = DefMI->getDesc();
@@ -652,9 +652,8 @@
   assert(SrcLR != SrcInt.end() && "Live range not found!");
   VNInfo *ValNo = SrcLR->valno;
   // If other defs can reach uses of this def, then it's not safe to perform
-  // the optimization. FIXME: Do isPHIDef and isDefAccurate both need to be
-  // tested?
-  if (ValNo->isPHIDef() || !ValNo->isDefAccurate() ||
+  // the optimization.
+  if (ValNo->isPHIDef() || li_->getInstructionFromIndex(ValNo->def)==0 ||
       ValNo->isUnused() || ValNo->hasPHIKill())
     return false;
   MachineInstr *DefMI = li_->getInstructionFromIndex(ValNo->def);
diff --git a/lib/CodeGen/Spiller.cpp b/lib/CodeGen/Spiller.cpp
index 40bb386..661b79c 100644
--- a/lib/CodeGen/Spiller.cpp
+++ b/lib/CodeGen/Spiller.cpp
@@ -144,7 +144,7 @@
         vrm->addSpillSlotUse(ss, loadInstr);
         SlotIndex endIndex = loadIndex.getNextIndex();
         VNInfo *loadVNI =
-          newLI->getNextValue(loadIndex, 0, true, lis->getVNInfoAllocator());
+          newLI->getNextValue(loadIndex, 0, lis->getVNInfoAllocator());
         newLI->addRange(LiveRange(loadIndex, endIndex, loadVNI));
       }
 
@@ -158,7 +158,7 @@
         vrm->addSpillSlotUse(ss, storeInstr);
         SlotIndex beginIndex = storeIndex.getPrevIndex();
         VNInfo *storeVNI =
-          newLI->getNextValue(beginIndex, 0, true, lis->getVNInfoAllocator());
+          newLI->getNextValue(beginIndex, 0, lis->getVNInfoAllocator());
         newLI->addRange(LiveRange(beginIndex, storeIndex, storeVNI));
       }
 
@@ -297,7 +297,8 @@
 
   /// Extract the given value number from the interval.
   LiveInterval* extractVNI(LiveInterval *li, VNInfo *vni) const {
-    assert(vni->isDefAccurate() || vni->isPHIDef());
+    assert((lis->getInstructionFromIndex(vni->def) != 0 || vni->isPHIDef()) &&
+           "Def index not sane?");
 
     // Create a new vreg and live interval, copy VNI ranges over.
     const TargetRegisterClass *trc = mri->getRegClass(li->reg);
@@ -335,8 +336,11 @@
                                      tii->get(TargetOpcode::COPY), newVReg)
                                .addReg(li->reg, RegState::Kill);
       SlotIndex copyIdx = lis->InsertMachineInstrInMaps(copyMI);
-      VNInfo *phiDefVNI = li->getNextValue(lis->getMBBStartIdx(defMBB),
-                                           0, false, lis->getVNInfoAllocator());
+      SlotIndex phiDefIdx = lis->getMBBStartIdx(defMBB);
+      assert(lis->getInstructionFromIndex(phiDefIdx) == 0 &&
+             "PHI def index points at actual instruction.");
+      VNInfo *phiDefVNI = li->getNextValue(phiDefIdx,
+                                           0, lis->getVNInfoAllocator());
       phiDefVNI->setIsPHIDef(true);
       li->addRange(LiveRange(phiDefVNI->def, copyIdx.getDefIndex(), phiDefVNI));
       LiveRange *oldPHIDefRange =
@@ -358,7 +362,6 @@
       newVNI->def = copyIdx.getDefIndex();
       newVNI->setCopy(copyMI);
       newVNI->setIsPHIDef(false); // not a PHI def anymore.
-      newVNI->setIsDefAccurate(true);
     } else {
       // non-PHI def. Rename the def. If it's two-addr that means renaming the
       // use and inserting a new copy too.
@@ -391,7 +394,7 @@
           li->getLiveRangeContaining(newVNI->def.getUseIndex());
         origUseRange->end = copyIdx.getDefIndex();
         VNInfo *copyVNI = newLI->getNextValue(copyIdx.getDefIndex(), copyMI,
-                                              true, lis->getVNInfoAllocator());
+                                              lis->getVNInfoAllocator());
         LiveRange copyRange(copyIdx.getDefIndex(),defIdx.getDefIndex(),copyVNI);
         newLI->addRange(copyRange);
       }
@@ -448,7 +451,7 @@
         // Insert a new range & vni for the two-address-to-copy value. This
         // will be attached to the new live interval.
         VNInfo *copyVNI =
-          newLI->getNextValue(useIdx.getDefIndex(), 0, true,
+          newLI->getNextValue(useIdx.getDefIndex(), 0,
                               lis->getVNInfoAllocator());
         LiveRange copyRange(useIdx.getDefIndex(),copyIdx.getDefIndex(),copyVNI);
         newLI->addRange(copyRange);
@@ -481,8 +484,7 @@
       }
 
       VNInfo *newKillVNI = li->getNextValue(copyIdx.getDefIndex(),
-                                            copyMI, true,
-                                            lis->getVNInfoAllocator());
+                                            copyMI, lis->getVNInfoAllocator());
       newKillVNI->setHasPHIKill(true);
       li->addRange(LiveRange(copyIdx.getDefIndex(),
                              lis->getMBBEndIdx(killMBB),
diff --git a/lib/CodeGen/SplitKit.cpp b/lib/CodeGen/SplitKit.cpp
index da85b42..048f6ab 100644
--- a/lib/CodeGen/SplitKit.cpp
+++ b/lib/CodeGen/SplitKit.cpp
@@ -365,7 +365,7 @@
   assert(parentli_.getVNInfoAt(Idx) == ParentVNI && "Bad ParentVNI");
 
   // Create a new value.
-  VNInfo *VNI = li_->getNextValue(Idx, 0, true, lis_.getVNInfoAllocator());
+  VNInfo *VNI = li_->getNextValue(Idx, 0, lis_.getVNInfoAllocator());
 
   // Use insert for lookup, so we can add missing values with a second lookup.
   std::pair<ValueMap::iterator,bool> InsP =
@@ -468,7 +468,7 @@
 
       // We have a collision between the old and new VNI at Succ. That means
       // neither dominates and we need a new phi-def.
-      VNI = li_->getNextValue(Start, 0, true, lis_.getVNInfoAllocator());
+      VNI = li_->getNextValue(Start, 0, lis_.getVNInfoAllocator());
       VNI->setIsPHIDef(true);
       InsP.first->second = VNI;
 
diff --git a/lib/CodeGen/Splitter.cpp b/lib/CodeGen/Splitter.cpp
index 1cb2f62..825782d 100644
--- a/lib/CodeGen/Splitter.cpp
+++ b/lib/CodeGen/Splitter.cpp
@@ -140,7 +140,6 @@
       VNInfo *newVal = getNewVNI(preHeaderRange->valno);
       newVal->def = copyDefIdx;
       newVal->setCopy(copy);
-      newVal->setIsDefAccurate(true);
       li.removeRange(copyDefIdx, ls.lis->getMBBEndIdx(preHeader), true);
 
       getNewLI()->addRange(LiveRange(copyDefIdx,
@@ -174,12 +173,13 @@
         
         // Blow away output range definition.
         outRange->valno->def = ls.lis->getInvalidIndex();
-        outRange->valno->setIsDefAccurate(false);
         li.removeRange(ls.lis->getMBBStartIdx(outBlock), copyDefIdx);
 
+        SlotIndex newDefIdx = ls.lis->getMBBStartIdx(outBlock);
+        assert(ls.lis->getInstructionFromIndex(newDefIdx) == 0 &&
+               "PHI def index points at actual instruction.");
         VNInfo *newVal =
-          getNewLI()->getNextValue(ls.lis->getMBBStartIdx(outBlock),
-                                   0, false, ls.lis->getVNInfoAllocator());
+          getNewLI()->getNextValue(newDefIdx, 0, ls.lis->getVNInfoAllocator());
 
         getNewLI()->addRange(LiveRange(ls.lis->getMBBStartIdx(outBlock),
                                        copyDefIdx, newVal));
@@ -513,8 +513,10 @@
       if (!insertRange)
         continue;
 
-      VNInfo *newVal = li.getNextValue(lis->getMBBStartIdx(preHeader),
-                                       0, false, lis->getVNInfoAllocator());
+      SlotIndex newDefIdx = lis->getMBBStartIdx(preHeader);
+      assert(lis->getInstructionFromIndex(newDefIdx) == 0 &&
+             "PHI def index points at actual instruction.");
+      VNInfo *newVal = li.getNextValue(newDefIdx, 0, lis->getVNInfoAllocator());
       li.addRange(LiveRange(lis->getMBBStartIdx(preHeader),
                             lis->getMBBEndIdx(preHeader),
                             newVal));
@@ -611,8 +613,11 @@
                          lis->getMBBEndIdx(splitBlock), true);
         }
       } else if (intersects) {
-        VNInfo *newVal = li.getNextValue(lis->getMBBStartIdx(splitBlock),
-                                         0, false, lis->getVNInfoAllocator());
+        SlotIndex newDefIdx = lis->getMBBStartIdx(splitBlock);
+        assert(lis->getInstructionFromIndex(newDefIdx) == 0 &&
+               "PHI def index points at actual instruction.");
+        VNInfo *newVal = li.getNextValue(newDefIdx, 0,
+                                         lis->getVNInfoAllocator());
         li.addRange(LiveRange(lis->getMBBStartIdx(splitBlock),
                               lis->getMBBEndIdx(splitBlock),
                               newVal));