- Remove arguments definition test from the VM.

runtime/vm/flow_graph_compiler_x64.cc

Index: runtime/vm/flow_graph_compiler_x64.cc
===================================================================
--- runtime/vm/flow_graph_compiler_x64.cc	(revision 24537)
+++ runtime/vm/flow_graph_compiler_x64.cc	(working copy)
@@ -1113,8 +1113,6 @@
   // the presence of optional parameters.
   // No such checking code is generated if only fixed parameters are declared,
   // unless we are in debug mode or unless we are compiling a closure.
-  LocalVariable* saved_args_desc_var =
-      parsed_function().GetSavedArgumentsDescriptorVar();
   if (num_copied_params == 0) {
 #ifdef DEBUG
     ASSERT(!parsed_function().function().HasOptionalParameters());
@@ -1158,26 +1156,12 @@
       }
       __ Bind(&correct_num_arguments);
     }
-    // The arguments descriptor is never saved in the absence of optional
-    // parameters, since any argument definition test would always yield true.
-    ASSERT(saved_args_desc_var == NULL);
   } else if (!flow_graph().IsCompiledForOsr()) {
-    if (saved_args_desc_var != NULL) {
-      __ Comment("Save arguments descriptor");
-      const Register kArgumentsDescriptorReg = R10;
-      // The saved_args_desc_var is allocated one slot before the first local.
-      const intptr_t slot = parsed_function().first_stack_local_index() + 1;
-      // If the saved_args_desc_var is captured, it is first moved to the stack
-      // and later to the context, once the context is allocated.
-      ASSERT(saved_args_desc_var->is_captured() ||
-             (saved_args_desc_var->index() == slot));
-      __ movq(Address(RBP, slot * kWordSize), kArgumentsDescriptorReg);
-    }
     CopyParameters();
   }
 
   // In unoptimized code, initialize (non-argument) stack allocated slots to
-  // null. This does not cover the saved_args_desc_var slot.
+  // null.
   if (!is_optimizing() && (num_locals > 0)) {
     __ Comment("Initialize spill slots");
     const intptr_t slot_base = parsed_function().first_stack_local_index();