8033215: clang: node.cpp:284 IDX_INIT macro use uninitialized field _out

Reviewed-by: twisti, kvn

src/share/vm/opto/node.cpp

@@ -286,6 +286,10 @@ void DUIterator_Last::verify_step(uint num_edges) {
 #ifdef _MSC_VER // the IDX_INIT hack falls foul of warning C4355
 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 #endif
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma GCC diagnostic ignored "-Wuninitialized"
+#endif
 
 // Out-of-line code from node constructors.
 // Executed only when extra debug info. is being passed around.
@@ -493,6 +497,10 @@ Node::Node(Node *n0, Node *n1, Node *n2, Node *n3,
   _in[6] = n6; if (n6 != NULL) n6->add_out((Node *)this);
 }
 
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
 
 //------------------------------clone------------------------------------------
 // Clone a Node.