[runtime] Optimize and unify rest parameters.

src/compiler/js-call-reducer.cc

Index: src/compiler/js-call-reducer.cc
diff --git a/src/compiler/js-call-reducer.cc b/src/compiler/js-call-reducer.cc
index 22acbc66489e15f7402f6e2c77029b4dfaa6e68c..376ab113fed4d228c1a4aeb4d5f1fa2814db7698 100644
--- a/src/compiler/js-call-reducer.cc
+++ b/src/compiler/js-call-reducer.cc
@@ -129,8 +129,7 @@ Reduction JSCallReducer::ReduceFunctionPrototypeApply(Node* node) {
     // Get to the actual frame state from which to extract the arguments;
     // we can only optimize this in case the {node} was already inlined into
     // some other function (and same for the {arg_array}).
-    CreateArgumentsParameters const& p =
-        CreateArgumentsParametersOf(arg_array->op());
+    CreateArgumentsType type = CreateArgumentsTypeOf(arg_array->op());
     Node* frame_state = NodeProperties::GetFrameStateInput(arg_array, 0);
     Node* outer_state = frame_state->InputAt(kFrameStateOuterStateInput);
     if (outer_state->opcode() != IrOpcode::kFrameState) return NoChange();
@@ -140,17 +139,22 @@ Reduction JSCallReducer::ReduceFunctionPrototypeApply(Node* node) {
       frame_state = outer_state;
     }
     FrameStateInfo state_info = OpParameter<FrameStateInfo>(frame_state);
-    if (p.type() == CreateArgumentsParameters::kMappedArguments) {
+    int start_index = 0;
+    if (type == CreateArgumentsType::kMappedArguments) {
       // Mapped arguments (sloppy mode) cannot be handled if they are aliased.
       Handle<SharedFunctionInfo> shared;
       if (!state_info.shared_info().ToHandle(&shared)) return NoChange();
       if (shared->internal_formal_parameter_count() != 0) return NoChange();
+    } else if (type == CreateArgumentsType::kRestParameter) {
+      Handle<SharedFunctionInfo> shared;
+      if (!state_info.shared_info().ToHandle(&shared)) return NoChange();
+      start_index = shared->internal_formal_parameter_count();
     }
     // Remove the argArray input from the {node}.
     node->RemoveInput(static_cast<int>(--arity));
     // Add the actual parameters to the {node}, skipping the receiver.
     Node* const parameters = frame_state->InputAt(kFrameStateParametersInput);
-    for (int i = p.start_index() + 1; i < state_info.parameter_count(); ++i) {
+    for (int i = start_index + 1; i < state_info.parameter_count(); ++i) {
       node->InsertInput(graph()->zone(), static_cast<int>(arity),
                         parameters->InputAt(i));
       ++arity;