Omit unreachable fall through code for graph intrinsics, e.g. Array.length.

runtime/vm/flow_graph_compiler.cc

Index: runtime/vm/flow_graph_compiler.cc
diff --git a/runtime/vm/flow_graph_compiler.cc b/runtime/vm/flow_graph_compiler.cc
index e668652800e57bd2b4e06f7f0cceb8cab3df0a59..0d4fdf38ed7225d4038b04c4d6e63aebff34e9bf 100644
--- a/runtime/vm/flow_graph_compiler.cc
+++ b/runtime/vm/flow_graph_compiler.cc
@@ -1172,9 +1172,10 @@ bool FlowGraphCompiler::TryIntrinsify() {
 
   EnterIntrinsicMode();
 
-  Intrinsifier::Intrinsify(parsed_function(), this);
+  bool complete = Intrinsifier::Intrinsify(parsed_function(), this);
 
   ExitIntrinsicMode();
+
   // "Deoptimization" from intrinsic continues here. All deoptimization
   // branches from intrinsic code redirect to here where the slow-path
   // (normal function body) starts.
@@ -1182,7 +1183,7 @@ bool FlowGraphCompiler::TryIntrinsify() {
   // before any deoptimization point.
   ASSERT(!intrinsic_slow_path_label_.IsBound());
   assembler()->Bind(&intrinsic_slow_path_label_);
-  return false;
+  return complete;
 }