Fix debug info with SafeStack.

llvm-svn: 248933
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 3c293c2..7ba51f6 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -496,6 +496,7 @@
   case dwarf::DW_OP_bit_piece:
     return 3;
   case dwarf::DW_OP_plus:
+  case dwarf::DW_OP_minus:
     return 2;
   default:
     return 1;
@@ -516,6 +517,7 @@
       // Piece expressions must be at the end.
       return I->get() + I->getSize() == E->get();
     case dwarf::DW_OP_plus:
+    case dwarf::DW_OP_minus:
     case dwarf::DW_OP_deref:
       break;
     }