diff --git a/include/llvm/CodeGen/RegisterPressure.h b/include/llvm/CodeGen/RegisterPressure.h
index 30326d0..cc9b1c4 100644
--- a/include/llvm/CodeGen/RegisterPressure.h
+++ b/include/llvm/CodeGen/RegisterPressure.h
@@ -150,7 +150,8 @@
   bool RequireIntervals;
 
   /// Register pressure corresponds to liveness before this instruction
-  /// iterator. It may point to the end of the block rather than an instruction.
+  /// iterator. It may point to the end of the block or a DebugValue rather than
+  /// an instruction.
   MachineBasicBlock::const_iterator CurrPos;
 
   /// Pressure map indexed by pressure set ID, not class ID.
@@ -184,6 +185,10 @@
   // position changes while pressure does not.
   void setPos(MachineBasicBlock::const_iterator Pos) { CurrPos = Pos; }
 
+  /// \brief Get the SlotIndex for the first nondebug instruction including or
+  /// after the current position.
+  SlotIndex getCurrSlot() const;
+
   /// Recede across the previous instruction.
   bool recede();
 
diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index cc7aabd..0789a74 100644
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -603,7 +603,11 @@
 
   SchedImpl->registerRoots();
 
+  // Advance past initial DebugValues.
+  assert(TopRPTracker.getPos() == RegionBegin && "bad initial Top tracker");
   CurrentTop = nextIfDebug(RegionBegin, RegionEnd);
+  TopRPTracker.setPos(CurrentTop);
+
   CurrentBottom = RegionEnd;
 }
 
diff --git a/lib/CodeGen/RegisterPressure.cpp b/lib/CodeGen/RegisterPressure.cpp
index 543c426..c7763dc 100644
--- a/lib/CodeGen/RegisterPressure.cpp
+++ b/lib/CodeGen/RegisterPressure.cpp
@@ -181,9 +181,6 @@
   }
 
   CurrPos = pos;
-  while (CurrPos != MBB->end() && CurrPos->isDebugValue())
-    ++CurrPos;
-
   CurrSetPressure.assign(TRI->getNumRegPressureSets(), 0);
 
   if (RequireIntervals)
@@ -214,11 +211,20 @@
           MachineBasicBlock::const_iterator());
 }
 
+
+SlotIndex RegPressureTracker::getCurrSlot() const {
+  MachineBasicBlock::const_iterator IdxPos = CurrPos;
+  while (IdxPos != MBB->end() && IdxPos->isDebugValue())
+    ++IdxPos;
+  if (IdxPos == MBB->end())
+    return LIS->getMBBEndIdx(MBB);
+  return LIS->getInstructionIndex(IdxPos).getRegSlot();
+}
+
 /// Set the boundary for the top of the region and summarize live ins.
 void RegPressureTracker::closeTop() {
   if (RequireIntervals)
-    static_cast<IntervalPressure&>(P).TopIdx =
-      LIS->getInstructionIndex(CurrPos).getRegSlot();
+    static_cast<IntervalPressure&>(P).TopIdx = getCurrSlot();
   else
     static_cast<RegionPressure&>(P).TopPos = CurrPos;
 
@@ -236,11 +242,7 @@
 /// Set the boundary for the bottom of the region and summarize live outs.
 void RegPressureTracker::closeBottom() {
   if (RequireIntervals)
-    if (CurrPos == MBB->end())
-      static_cast<IntervalPressure&>(P).BottomIdx = LIS->getMBBEndIdx(MBB);
-    else
-      static_cast<IntervalPressure&>(P).BottomIdx =
-        LIS->getInstructionIndex(CurrPos).getRegSlot();
+    static_cast<IntervalPressure&>(P).BottomIdx = getCurrSlot();
   else
     static_cast<RegionPressure&>(P).BottomPos = CurrPos;
 
@@ -510,7 +512,7 @@
 
   SlotIndex SlotIdx;
   if (RequireIntervals)
-    SlotIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
+    SlotIdx = getCurrSlot();
 
   // Open the bottom of the region using slot indexes.
   if (isBottomClosed()) {
@@ -769,7 +771,7 @@
       const LiveInterval *LI = &LIS->getInterval(Reg);
       // FIXME: allow the caller to pass in the list of vreg uses that remain to
       // be bottom-scheduled to avoid searching uses at each query.
-      SlotIndex CurrIdx = LIS->getInstructionIndex(CurrPos).getRegSlot();
+      SlotIndex CurrIdx = getCurrSlot();
       if (LI->killedAt(SlotIdx)
           && !findUseBetween(Reg, CurrIdx, SlotIdx, MRI, LIS)) {
         decreaseVirtRegPressure(Reg);
diff --git a/lib/CodeGen/ScheduleDAGInstrs.cpp b/lib/CodeGen/ScheduleDAGInstrs.cpp
index fd75576..2a41293 100644
--- a/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -713,17 +713,17 @@
   addSchedBarrierDeps();
 
   // Walk the list of instructions, from bottom moving up.
-  MachineInstr *PrevMI = NULL;
+  MachineInstr *DbgMI = NULL;
   for (MachineBasicBlock::iterator MII = RegionEnd, MIE = RegionBegin;
        MII != MIE; --MII) {
     MachineInstr *MI = prior(MII);
-    if (MI && PrevMI) {
-      DbgValues.push_back(std::make_pair(PrevMI, MI));
-      PrevMI = NULL;
+    if (MI && DbgMI) {
+      DbgValues.push_back(std::make_pair(DbgMI, MI));
+      DbgMI = NULL;
     }
 
     if (MI->isDebugValue()) {
-      PrevMI = MI;
+      DbgMI = MI;
       continue;
     }
     if (RPTracker) {
@@ -917,8 +917,8 @@
       }
     }
   }
-  if (PrevMI)
-    FirstDbgValue = PrevMI;
+  if (DbgMI)
+    FirstDbgValue = DbgMI;
 
   Defs.clear();
   Uses.clear();
diff --git a/test/CodeGen/X86/2012-11-30-regpres-dbg.ll b/test/CodeGen/X86/2012-11-30-regpres-dbg.ll
new file mode 100644
index 0000000..d290d51
--- /dev/null
+++ b/test/CodeGen/X86/2012-11-30-regpres-dbg.ll
@@ -0,0 +1,43 @@
+; RUN: llc < %s -mtriple=x86_64-apple-macosx -enable-misched \
+; RUN:          -verify-machineinstrs | FileCheck %s
+;
+; Test RegisterPressure handling of DBG_VALUE.
+;
+; CHECK: %entry
+; CHECK: DEBUG_VALUE: callback
+; CHECK: ret
+
+%struct.btCompoundLeafCallback = type { i32, i32 }
+
+declare void @llvm.dbg.declare(metadata, metadata) nounwind readnone
+
+define void @test() unnamed_addr uwtable ssp align 2 {
+entry:
+  %callback = alloca %struct.btCompoundLeafCallback, align 8
+  br i1 undef, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  unreachable
+
+if.end:                                           ; preds = %entry
+  call void @llvm.dbg.declare(metadata !{%struct.btCompoundLeafCallback* %callback}, metadata !3)
+  %m = getelementptr inbounds %struct.btCompoundLeafCallback* %callback, i64 0, i32 1
+  store i32 0, i32* undef, align 8
+  %cmp12447 = icmp sgt i32 undef, 0
+  br i1 %cmp12447, label %for.body.lr.ph, label %invoke.cont44
+
+for.body.lr.ph:                                   ; preds = %if.end
+  unreachable
+
+invoke.cont44:                                    ; preds = %if.end
+  ret void
+}
+
+!llvm.dbg.cu = !{!0}
+
+!0 = metadata !{i32 786449, i32 0, i32 4, metadata !"MultiSource/Benchmarks/Bullet/btCompoundCollisionAlgorithm.cpp", metadata !"MultiSource/Benchmarks/Bullet", metadata !"clang version 3.3 (trunk 168984) (llvm/trunk 168983)", i1 true, i1 true, metadata !"", i32 0, metadata !1, null, null, null} ; [ DW_TAG_compile_unit ] [MultiSource/Benchmarks/Bullet/MultiSource/Benchmarks/Bullet/btCompoundCollisionAlgorithm.cpp] [DW_LANG_C_plus_plus]
+!1 = metadata !{metadata !2}
+!2 = metadata !{null, null}
+!3 = metadata !{i32 786688, null, metadata !"callback", null, i32 214, metadata !4, i32 0, i32 0} ; [ DW_TAG_auto_variable ] [callback] [line 214]
+!4 = metadata !{i32 786451, null, metadata !"btCompoundLeafCallback", metadata !5, i32 90, i64 512, i64 64, i32 0, i32 0, null, null, i32 0, null, null} ; [ DW_TAG_structure_type ] [btCompoundLeafCallback] [line 90, size 512, align 64, offset 0] [from ]
+!5 = metadata !{i32 786473, metadata !"MultiSource/Benchmarks/Bullet/btCompoundCollisionAlgorithm.cpp", metadata !"MultiSource/Benchmarks/Bullet", null} ; [ DW_TAG_file_type ]