Detect simple tail calls

src/compiler/js-generic-lowering.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/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/js-generic-lowering.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/machine-operator.h"
@@ skipping 473 matching lines @@
 
   // TODO(titzer): total hack to share function context constants.
   // Remove this when the JSGraph canonicalizes heap constants.
   Node* context = node->InputAt(index);
   HeapObjectMatcher<Context> context_const(context);
   if (!context_const.HasValue() ||
       *(context_const.Value().handle()) != function->context()) {
     context = jsgraph()->HeapConstant(Handle<Context>(function->context()));
   }
   node->ReplaceInput(index, context);
-  CallDescriptor* desc = Linkage::GetJSCallDescriptor(
-      zone(), false, 1 + arg_count, FlagsForNode(node));
+  CallDescriptor::Flags flags = FlagsForNode(node);
+  if (is_strict(p.language_mode())) flags |= CallDescriptor::kSupportsTailCalls;
+  CallDescriptor* desc =
+      Linkage::GetJSCallDescriptor(zone(), false, 1 + arg_count, flags);
   node->set_op(common()->Call(desc));
   return true;
 }
 
 
 void JSGenericLowering::LowerJSCallFunction(Node* node) {
   // Fast case: call function directly.
   if (TryLowerDirectJSCall(node)) return;
 
   // General case: CallFunctionStub.
@@ skipping 64 matching lines @@
 }
 
 
 MachineOperatorBuilder* JSGenericLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8