Simplify Hydrogen code stubs with variable argument count

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 0912661d7e3664e042938ca16ed603b732a9302a..9d95fc42639ac985980073f2040a08ce9d2cc3fb 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -176,14 +176,21 @@ static void InitializeArrayConstructorDescriptor(
   // rax -- number of arguments
   // rdi -- function
   // rbx -- type info cell with elements kind
-  static Register registers[] = { rdi, rbx };
-  descriptor->register_param_count_ = 2;
-  if (constant_stack_parameter_count != 0) {
+  static Register registers_variable_args[] = { rdi, rbx, rax };
+  static Register registers_no_args[] = { rdi, rbx };
+
+  if (constant_stack_parameter_count == 0) {
+    descriptor->register_param_count_ = 2;
+    descriptor->register_params_ = registers_no_args;
+  } else {
     // stack param count needs (constructor pointer, and single argument)
+    descriptor->handler_arguments_mode_ = PASS_ARGUMENTS;
     descriptor->stack_parameter_count_ = rax;
+    descriptor->register_param_count_ = 3;
+    descriptor->register_params_ = registers_variable_args;
   }
+
   descriptor->hint_stack_parameter_count_ = constant_stack_parameter_count;
-  descriptor->register_params_ = registers;
   descriptor->function_mode_ = JS_FUNCTION_STUB_MODE;
   descriptor->deoptimization_handler_ =
       Runtime::FunctionForId(Runtime::kArrayConstructor)->entry;
@@ -197,15 +204,21 @@ static void InitializeInternalArrayConstructorDescriptor(
   // register state
   // rax -- number of arguments
   // rdi -- constructor function
-  static Register registers[] = { rdi };
-  descriptor->register_param_count_ = 1;
+  static Register registers_variable_args[] = { rdi, rax };
+  static Register registers_no_args[] = { rdi };
 
-  if (constant_stack_parameter_count != 0) {
+  if (constant_stack_parameter_count == 0) {
+    descriptor->register_param_count_ = 1;
+    descriptor->register_params_ = registers_no_args;
+  } else {
     // stack param count needs (constructor pointer, and single argument)
+    descriptor->handler_arguments_mode_ = PASS_ARGUMENTS;
     descriptor->stack_parameter_count_ = rax;
+    descriptor->register_param_count_ = 2;
+    descriptor->register_params_ = registers_variable_args;
   }
+
   descriptor->hint_stack_parameter_count_ = constant_stack_parameter_count;
-  descriptor->register_params_ = registers;
   descriptor->function_mode_ = JS_FUNCTION_STUB_MODE;
   descriptor->deoptimization_handler_ =
       Runtime::FunctionForId(Runtime::kInternalArrayConstructor)->entry;