[turbofan] Better and more sane support for tail calls

src/runtime/runtime-function.cc

 // Copyright 2014 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.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/compiler.h"
 #include "src/deoptimizer.h"
@@ skipping 510 matching lines @@
     argv[i] = args.at<Object>(2 + i);
   }
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Execution::Call(isolate, target, receiver, argc, argv.start()));
   return *result;
 }
 
 
+RUNTIME_FUNCTION(Runtime_TailCall) {
+  UNREACHABLE();

[Jarin, 2015/11/12 13:45:12]

Why do not we just do the same thing as Runtime_Call here? Ultimately, we would
want to fuzz this.

[danno, 2015/11/13 10:04:17]

Done.

+  return 0;
+}
+
+
 RUNTIME_FUNCTION(Runtime_Apply) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 5);
   CONVERT_ARG_HANDLE_CHECKED(JSReceiver, fun, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, receiver, 1);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, arguments, 2);
   CONVERT_INT32_ARG_CHECKED(offset, 3);
   CONVERT_INT32_ARG_CHECKED(argc, 4);
   RUNTIME_ASSERT(offset >= 0);
   // Loose upper bound to allow fuzzing. We'll most likely run out of
@@ skipping 67 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_ThrowStrongModeTooFewArguments) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 0);
   THROW_NEW_ERROR_RETURN_FAILURE(isolate,
                                  NewTypeError(MessageTemplate::kStrongArity));
 }
 
 }  // namespace internal
 }  // namespace v8