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

runtime/vm/intrinsifier.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Class for intrinsifying functions.
 
 #include "vm/assembler.h"
 #include "vm/compiler.h"
 #include "vm/cpu.h"
 #include "vm/flags.h"
 #include "vm/flow_graph.h"
@@ skipping 197 matching lines @@
     printer.PrintBlocks();
   }
   EmitCodeFor(compiler, graph);
   return true;
 #else
   return false;
 #endif  // !defined(TARGET_ARCH_DBC)
 }
 
 
-void Intrinsifier::Intrinsify(const ParsedFunction& parsed_function,
+// Returns true if fall-through code can be omitted.
+bool Intrinsifier::Intrinsify(const ParsedFunction& parsed_function,
                               FlowGraphCompiler* compiler) {
   const Function& function = parsed_function.function();
   if (!CanIntrinsify(function)) {
-    return;
+    return false;
   }
 
   ASSERT(!compiler->flow_graph().IsCompiledForOsr());
   if (GraphIntrinsify(parsed_function, compiler)) {
-    return;
+    return compiler->intrinsic_slow_path_label()->IsUnused();
   }
 
 #define EMIT_CASE(class_name, function_name, enum_name, type, fp)              \
     case MethodRecognizer::k##enum_name:                                       \
       compiler->assembler()->Comment("Intrinsic");                             \
       enum_name(compiler->assembler());                                        \
       break;
 
   switch (function.recognized_kind()) {
     ALL_INTRINSICS_NO_INTEGER_LIB_LIST(EMIT_CASE);
@@ skipping 10 matching lines @@
   // intrinsics.
 #if defined(TARGET_ARCH_DBC)
   switch (function.recognized_kind()) {
     GRAPH_INTRINSICS_LIST(EMIT_CASE)
     default:
       break;
   }
 #endif
 
 #undef EMIT_INTRINSIC
+  return false;
 }
 
 
 #if !defined(TARGET_ARCH_DBC)
 static intptr_t CidForRepresentation(Representation rep) {
   switch (rep) {
     case kUnboxedDouble:
       return kDoubleCid;
     case kUnboxedFloat32x4:
       return kFloat32x4Cid;
@@ skipping 999 matching lines @@
   TargetEntryInstr* normal_entry = graph_entry->normal_entry();
   BlockBuilder builder(flow_graph, normal_entry);
 
   return BuildInvokeMathCFunction(&builder,
                                   MethodRecognizer::kDoubleRound);
 }
 #endif  // !defined(TARGET_ARCH_DBC)
 
 
 }  // namespace dart