diff --git a/include/llvm/CodeGen/FunctionLoweringInfo.h b/include/llvm/CodeGen/FunctionLoweringInfo.h
index c49d1ed..f17fe5a 100644
--- a/include/llvm/CodeGen/FunctionLoweringInfo.h
+++ b/include/llvm/CodeGen/FunctionLoweringInfo.h
@@ -77,6 +77,9 @@
   /// anywhere in the function.
   DenseMap<const AllocaInst*, int> StaticAllocaMap;
 
+  /// ByValArgFrameIndexMap - Keep track of frame indices for byval arguments.
+  DenseMap<const Argument*, int> ByValArgFrameIndexMap;
+
   /// ArgDbgValues - A list of DBG_VALUE instructions created during isel for
   /// function arguments that are inserted after scheduling is completed.
   SmallVector<MachineInstr*, 8> ArgDbgValues;
@@ -138,6 +141,13 @@
     assert(R == 0 && "Already initialized this value register!");
     return R = CreateRegs(V->getType());
   }
+
+  /// setByValArgumentFrameIndex - Record frame index for the byval
+  /// argument.
+  void setByValArgumentFrameIndex(const Argument *A, int FI);
+  
+  /// getByValArgumentFrameIndex - Get frame index for the byval argument.
+  int getByValArgumentFrameIndex(const Argument *A);
 };
 
 /// AddCatchInfo - Extract the personality and type infos from an eh.selector
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index eaa12d4..eeae8a3 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1629,9 +1629,16 @@
     bool updated = false;
     // FIXME : Handle getNumOperands != 3
     if (DVInsn->getNumOperands() == 3) {
-      if (DVInsn->getOperand(0).isReg())
-        updated =
-          addRegisterAddress(VariableDie, DVLabel, DVInsn->getOperand(0));
+      if (DVInsn->getOperand(0).isReg()) {
+        const MachineOperand RegOp = DVInsn->getOperand(0);
+        const TargetRegisterInfo *TRI = Asm->TM.getRegisterInfo();
+        if (DVInsn->getOperand(1).isImm() &&
+            TRI->getFrameRegister(*Asm->MF) == RegOp.getReg()) {
+          addVariableAddress(DV, VariableDie, DVInsn->getOperand(1).getImm());
+          updated = true;
+        } else
+          updated = addRegisterAddress(VariableDie, DVLabel, RegOp);
+      }
       else if (DVInsn->getOperand(0).isImm())
         updated = addConstantValue(VariableDie, DVLabel, DVInsn->getOperand(0));
       else if (DVInsn->getOperand(0).isFPImm())
diff --git a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index 77a2c86..5ef6404 100644
--- a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -221,6 +221,7 @@
 #endif
   LiveOutRegInfo.clear();
   ArgDbgValues.clear();
+  ByValArgFrameIndexMap.clear();
   RegFixups.clear();
 }
 
@@ -254,6 +255,28 @@
   return FirstReg;
 }
 
+/// setByValArgumentFrameIndex - Record frame index for the byval
+/// argument. This overrides previous frame index entry for this argument,
+/// if any.
+void FunctionLoweringInfo::setByValArgumentFrameIndex(const Argument *A, 
+                                                      int FI) {
+  assert (A->hasByValAttr() && "Argument does not have byval attribute!");
+  ByValArgFrameIndexMap[A] = FI;
+}
+  
+/// getByValArgumentFrameIndex - Get frame index for the byval argument.
+/// If the argument does not have any assigned frame index then 0 is
+/// returned.
+int FunctionLoweringInfo::getByValArgumentFrameIndex(const Argument *A) {
+  assert (A->hasByValAttr() && "Argument does not have byval attribute!");
+  DenseMap<const Argument *, int>::iterator I = 
+    ByValArgFrameIndexMap.find(A);
+  if (I != ByValArgFrameIndexMap.end())
+    return I->second;
+  DEBUG(dbgs() << "Argument does not have assigned frame index!");
+  return 0;
+}
+
 /// AddCatchInfo - Extract the personality and type infos from an eh.selector
 /// call, and add them to the specified machine basic block.
 void llvm::AddCatchInfo(const CallInst &I, MachineModuleInfo *MMI,
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index b70bfea..a773335 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3917,7 +3917,8 @@
 SelectionDAGBuilder::EmitFuncArgumentDbgValue(const Value *V, MDNode *Variable,
                                               int64_t Offset, 
                                               const SDValue &N) {
-  if (!isa<Argument>(V))
+  const Argument *Arg = dyn_cast<Argument>(V);
+  if (!Arg)
     return false;
 
   MachineFunction &MF = DAG.getMachineFunction();
@@ -3931,6 +3932,14 @@
     return false;
 
   unsigned Reg = 0;
+  if (Arg->hasByValAttr()) {
+    // Byval arguments' frame index is recorded during argument lowering.
+    // Use this info directly.
+    const TargetRegisterInfo *TRI = DAG.getTarget().getRegisterInfo();
+    Reg = TRI->getFrameRegister(MF);
+    Offset = FuncInfo.getByValArgumentFrameIndex(Arg);
+  }
+
   if (N.getNode() && N.getOpcode() == ISD::CopyFromReg) {
     Reg = cast<RegisterSDNode>(N.getOperand(1))->getReg();
     if (Reg && TargetRegisterInfo::isVirtualRegister(Reg)) {
@@ -4075,6 +4084,9 @@
     // debug info exists.
     ++SDNodeOrder;
     SDValue &N = NodeMap[Address];
+    if (!N.getNode() && isa<Argument>(Address))
+      // Check unused arguments map.
+      N = UnusedArgNodeMap[Address];
     SDDbgValue *SDV;
     if (N.getNode()) {
       if (isParameter && !AI) {
@@ -6131,6 +6143,12 @@
       i += NumParts;
     }
 
+    // Note down frame index for byval arguments.
+    if (I->hasByValAttr() && !ArgValues.empty())
+      if (FrameIndexSDNode *FI = 
+          dyn_cast<FrameIndexSDNode>(ArgValues[0].getNode()))
+        FuncInfo->setByValArgumentFrameIndex(I, FI->getIndex());
+
     if (!I->use_empty()) {
       SDValue Res;
       if (!ArgValues.empty())
diff --git a/test/FrontendC++/2010-08-31-ByValArg.cpp b/test/FrontendC++/2010-08-31-ByValArg.cpp
new file mode 100644
index 0000000..be0d354
--- /dev/null
+++ b/test/FrontendC++/2010-08-31-ByValArg.cpp
@@ -0,0 +1,53 @@
+// This regression test checks byval arguments' debug info.
+// Radar 8367011
+// RUN: %llvmgcc -S -O0 -g %s -o - | \
+// RUN:    llc --disable-fp-elim -o %t.s -O0 -relocation-model=pic
+// RUN: %compile_c %t.s -o %t.o
+// RUN: %link %t.o -o %t.exe
+// RUN: echo {break get\nrun\np missing_arg.b} > %t.in 
+// RUN: gdb -q -batch -n -x %t.in %t.exe | tee %t.out | \
+// RUN:   grep {1 = 4242}
+
+// XTARGET: x86_64-apple-darwin
+
+class EVT {
+public:
+  int a;
+  int b;
+  int c;
+};
+
+class VAL {
+public:
+  int x;
+  int y;
+};
+void foo(EVT e);
+EVT bar();
+
+void get(int *i, unsigned dl, VAL v, VAL *p, unsigned n, EVT missing_arg) {
+//CHECK: .ascii "missing_arg"
+  EVT e = bar();
+  if (dl == n)
+    foo(missing_arg);
+}
+
+
+EVT bar() {
+	EVT e;
+	return e;
+}
+
+void foo(EVT e) {}
+
+int main(){
+	VAL v;
+	EVT ma;
+	ma.a = 1;
+	ma.b = 4242;
+	ma.c = 3;
+	int i = 42;	
+	get (&i, 1, v, &v, 2, ma);
+	return 0;
+}
+