diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 9a24919..12b0b12 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -362,7 +362,10 @@
         const TargetInstrDesc &II = TII.get(TargetInstrInfo::DBG_LABEL);
         ID = DW->RecordInlinedFnEnd(Subprogram);
         if (ID)
-          // If ID is 0 then this was not an end of inlined region.
+          // Returned ID is 0 if this is unbalanced "end of inlined
+          // scope". This could happen if optimizer eats dbg intrinsics
+          // or "beginning of inlined scope" is not recoginized due to
+          // missing location info. In such cases, do ignore this region.end.
           BuildMI(MBB, DL, II).addImm(ID);
       } else {
         const TargetInstrDesc &II = TII.get(TargetInstrInfo::DBG_LABEL);
@@ -387,9 +390,14 @@
       unsigned SrcFile = DW->getOrCreateSourceID(CompileUnit.getDirectory(Dir),
                                                  CompileUnit.getFilename(FN));
 
-      if (!Subprogram.describes(MF.getFunction()) && !PrevLoc.isUnknown()) {
+      if (!Subprogram.describes(MF.getFunction())) {
         // This is a beginning of an inlined function.
         
+        // If llvm.dbg.func.start is seen in a new block before any
+        // llvm.dbg.stoppoint intrinsic then the location info is unknown.
+        // FIXME : Why DebugLoc is reset at the beginning of each block ?
+        if (PrevLoc.isUnknown())
+          return true;
         // Record the source line.
         unsigned Line = Subprogram.getLineNumber();
         unsigned LabelID = DW->RecordSourceLine(Line, 0, SrcFile);
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
index 832ad7e..5204113 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
@@ -3966,6 +3966,10 @@
         if (Fast) {
           unsigned ID = DW->RecordInlinedFnEnd(Subprogram);
           if (ID != 0)
+            // Returned ID is 0 if this is unbalanced "end of inlined
+            // scope". This could happen if optimizer eats dbg intrinsics
+            // or "beginning of inlined scope" is not recoginized due to
+            // missing location info. In such cases, do ignore this region.end.
             DAG.setRoot(DAG.getLabel(ISD::DBG_LABEL, getCurDebugLoc(), 
                                      getRoot(), ID));
         }
@@ -4000,6 +4004,12 @@
         if (!Subprogram.describes(MF.getFunction())) {
           // This is a beginning of an inlined function.
 
+          // If llvm.dbg.func.start is seen in a new block before any
+          // llvm.dbg.stoppoint intrinsic then the location info is unknown.
+          // FIXME : Why DebugLoc is reset at the beginning of each block ?
+          if (PrevLoc.isUnknown())
+            return 0;
+
           // Record the source line.
           unsigned Line = Subprogram.getLineNumber();
           unsigned LabelID = DW->RecordSourceLine(Line, 0, SrcFile);