[DebugInfo] Fix PR37395.

DbgLabelInst has no address as its operands.

Differential Revision: https://reviews.llvm.org/D46738

Patch by Hsiangkai Wang.

llvm-svn: 336176
diff --git a/llvm/lib/IR/IntrinsicInst.cpp b/llvm/lib/IR/IntrinsicInst.cpp
index 9ffcae1..7878899 100644
--- a/llvm/lib/IR/IntrinsicInst.cpp
+++ b/llvm/lib/IR/IntrinsicInst.cpp
@@ -45,7 +45,10 @@
     return V->getValue();
 
   // When the value goes to null, it gets replaced by an empty MDNode.
-  assert(!cast<MDNode>(MD)->getNumOperands() && "Expected an empty MDNode");
+  assert((isa<DbgLabelInst>(this)
+          || !cast<MDNode>(MD)->getNumOperands())
+	 && "DbgValueInst Expected an empty MDNode");
+
   return nullptr;
 }