diff --git a/include/llvm/CodeGen/LiveIntervalAnalysis.h b/include/llvm/CodeGen/LiveIntervalAnalysis.h
index b87214f5e2c..aec72858c83 100644
--- a/include/llvm/CodeGen/LiveIntervalAnalysis.h
+++ b/include/llvm/CodeGen/LiveIntervalAnalysis.h
@@ -282,6 +282,10 @@ namespace llvm {
         I = r2iMap_.insert(std::make_pair(reg, createInterval(reg))).first;
       return *I->second;
     }
+
+    /// dupInterval - Duplicate a live interval. The caller is responsible for
+    /// managing the allocated memory.
+    LiveInterval *dupInterval(LiveInterval *li);
     
     /// addLiveRangeToEndOfBlock - Given a register and an instruction,
     /// adds a live range from that instruction to the end of its MBB.
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 8e8e8ff6d0c..985a3fa1634 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -824,11 +824,18 @@ bool LiveIntervals::findReachableMBBs(unsigned Start, unsigned End,
 }
 
 LiveInterval* LiveIntervals::createInterval(unsigned reg) {
-  float Weight = TargetRegisterInfo::isPhysicalRegister(reg) ?
-                       HUGE_VALF : 0.0F;
+  float Weight = TargetRegisterInfo::isPhysicalRegister(reg) ? HUGE_VALF : 0.0F;
   return new LiveInterval(reg, Weight);
 }
 
+/// dupInterval - Duplicate a live interval. The caller is responsible for
+/// managing the allocated memory.
+LiveInterval* LiveIntervals::dupInterval(LiveInterval *li) {
+  LiveInterval *NewLI = createInterval(li->reg);
+  NewLI->Copy(*li, getVNInfoAllocator());
+  return NewLI;
+}
+
 /// getVNInfoSourceReg - Helper function that parses the specified VNInfo
 /// copy field and returns the source register that defines it.
 unsigned LiveIntervals::getVNInfoSourceReg(const VNInfo *VNI) const {
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index db7109e7a63..7a8ea6f6d8f 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -1354,6 +1354,15 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
   DOUT << " and "; DstInt.print(DOUT, tri_);
   DOUT << ": ";
 
+  // Save a copy of the virtual register live interval. We'll manually
+  // merge this into the "real" physical register live interval this is
+  // coalesced with.
+  LiveInterval *SavedLI = 0;
+  if (RealDstReg)
+    SavedLI = li_->dupInterval(&SrcInt);
+  else if (RealSrcReg)
+    SavedLI = li_->dupInterval(&DstInt);
+
   // Check if it is necessary to propagate "isDead" property.
   if (!isExtSubReg && !isInsSubReg) {
     MachineOperand *mopd = CopyMI->findRegisterDefOperand(DstReg, false);
@@ -1445,21 +1454,17 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
     if (RealDstReg || RealSrcReg) {
       LiveInterval &RealInt =
         li_->getOrCreateInterval(RealDstReg ? RealDstReg : RealSrcReg);
-      SmallSet<const VNInfo*, 4> CopiedValNos;
-      for (LiveInterval::Ranges::const_iterator I = ResSrcInt->ranges.begin(),
-             E = ResSrcInt->ranges.end(); I != E; ++I) {
-        const LiveRange *DstLR = ResDstInt->getLiveRangeContaining(I->start);
-        assert(DstLR  && "Invalid joined interval!");
-        const VNInfo *DstValNo = DstLR->valno;
-        if (CopiedValNos.insert(DstValNo)) {
-          VNInfo *ValNo = RealInt.getNextValue(DstValNo->def, DstValNo->copy,
-                                               li_->getVNInfoAllocator());
-          ValNo->hasPHIKill = DstValNo->hasPHIKill;
-          RealInt.addKills(ValNo, DstValNo->kills);
-          RealInt.MergeValueInAsValue(*ResDstInt, DstValNo, ValNo);
-        }
+      for (LiveInterval::const_vni_iterator I = SavedLI->vni_begin(),
+             E = SavedLI->vni_end(); I != E; ++I) {
+        const VNInfo *ValNo = *I;
+        VNInfo *NewValNo = RealInt.getNextValue(ValNo->def, ValNo->copy,
+                                                li_->getVNInfoAllocator());
+        NewValNo->hasPHIKill = ValNo->hasPHIKill;
+        NewValNo->redefByEC = ValNo->redefByEC;
+        RealInt.addKills(NewValNo, ValNo->kills);
+        RealInt.MergeValueInAsValue(*SavedLI, ValNo, NewValNo);
       }
-      
+      RealInt.weight += SavedLI->weight;      
       DstReg = RealDstReg ? RealDstReg : RealSrcReg;
     }
 
@@ -1529,6 +1534,12 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
   // being merged.
   li_->removeInterval(SrcReg);
 
+  // Manually deleted the live interval copy.
+  if (SavedLI) {
+    SavedLI->clear();
+    delete SavedLI;
+  }
+
   if (isEmpty) {
     // Now the copy is being coalesced away, the val# previously defined
     // by the copy is being defined by an IMPLICIT_DEF which defines a zero
diff --git a/test/CodeGen/X86/2009-02-08-CoalescerBug.ll b/test/CodeGen/X86/2009-02-08-CoalescerBug.ll
new file mode 100644
index 00000000000..cd30c1e7e40
--- /dev/null
+++ b/test/CodeGen/X86/2009-02-08-CoalescerBug.ll
@@ -0,0 +1,22 @@
+; RUN: llvm-as < %s | llc -march=x86
+; PR3486
+
+define i32 @foo(i8 signext %p_26) nounwind {
+entry:
+	%0 = icmp eq i8 %p_26, 0		; <i1> [#uses=2]
+	%or.cond = or i1 false, %0		; <i1> [#uses=2]
+	%iftmp.1.0 = zext i1 %or.cond to i16		; <i16> [#uses=1]
+	br i1 %0, label %bb.i, label %bar.exit
+
+bb.i:		; preds = %entry
+	%1 = zext i1 %or.cond to i32		; <i32> [#uses=1]
+	%2 = sdiv i32 %1, 0		; <i32> [#uses=1]
+	%3 = trunc i32 %2 to i16		; <i16> [#uses=1]
+	br label %bar.exit
+
+bar.exit:		; preds = %bb.i, %entry
+	%4 = phi i16 [ %3, %bb.i ], [ %iftmp.1.0, %entry ]		; <i16> [#uses=1]
+	%5 = trunc i16 %4 to i8		; <i8> [#uses=1]
+	%6 = sext i8 %5 to i32		; <i32> [#uses=1]
+	ret i32 %6
+}