[generators] Make runtime functions more robust.

Only look at the --ignition-generators flag when determining whether to use
Ignition (in compiler.cc).  In generator runtime functions, instead of looking
at the flag, determine the generator kind based on whether the generator has a
bytecode array.  This allows compiling some generator function using
full-codegen and others using Ignition, e.g when using --ignition-filter.

R=mstarzinger@chromium.org
BUG=chromium:618657,v8:4907

Review-Url: https://codereview.chromium.org/2052873002
Cr-Commit-Position: refs/heads/master@{#36864}

src/runtime/runtime-generator.cc

@@ -21,11 +21,12 @@ RUNTIME_FUNCTION(Runtime_CreateJSGeneratorObject) {
   CHECK(function->shared()->is_resumable());
 
   Handle<FixedArray> operand_stack;
-  if (FLAG_ignition && FLAG_ignition_generators) {
+  if (function->shared()->HasBytecodeArray()) {
+    // New-style generators.
     int size = function->shared()->bytecode_array()->register_count();
     operand_stack = isolate->factory()->NewFixedArray(size);
   } else {
-    DCHECK(!function->shared()->HasBytecodeArray());
+    // Old-style generators.
     operand_stack = handle(isolate->heap()->empty_fixed_array());
   }
 
@@ -148,9 +149,8 @@ RUNTIME_FUNCTION(Runtime_GeneratorGetSourcePosition) {
 
   if (!generator->is_suspended()) return isolate->heap()->undefined_value();
 
-  if (FLAG_ignition && FLAG_ignition_generators) UNIMPLEMENTED();
+  if (generator->function()->shared()->HasBytecodeArray()) UNIMPLEMENTED();
 
-  DCHECK(!generator->function()->shared()->HasBytecodeArray());
   Handle<Code> code(generator->function()->code(), isolate);
   int offset = generator->continuation();
   CHECK(0 <= offset && offset < code->instruction_size());

test/mjsunit/regress/regress-618657.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --ignition --ignition-generators --ignition-filter=-foo
+
+function* foo() { yield 42 }
+var g = foo();
+assertEquals(42, g.next().value);
+assertEquals(true, g.next().done);