Do not emit line number entries for unknown debug values.
This fixes recent regression in store.exp from gdb testsuite.

llvm-svn: 104524
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 9af5256..145bf71 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -2195,6 +2195,9 @@
     if (!DV.Verify()) return;
     if (DV.getTag() != dwarf::DW_TAG_arg_variable)
       LocalVar = true;
+    // Ignore Undef values.
+    if (MI->getOperand(0).isReg() && !MI->getOperand(0).getReg())
+      LocalVar = false;
   }
 
   MCSymbol *Label = NULL;