[runtime] Optimize and unify rest parameters.

src/full-codegen/mips/full-codegen-mips.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_MIPS
 
 // Note on Mips implementation:
 //
 // The result_register() for mips is the 'v0' register, which is defined
 // by the ABI to contain function return values. However, the first
@@ skipping 256 matching lines @@
   if (new_target_var != nullptr) {
     Comment cmnt(masm_, "[ new.target");
     SetVar(new_target_var, a3, a0, a2);
   }
 
   // Possibly allocate RestParameters
   int rest_index;
   Variable* rest_param = scope()->rest_parameter(&rest_index);
   if (rest_param) {
     Comment cmnt(masm_, "[ Allocate rest parameter array");
-
-    int num_parameters = info->scope()->num_parameters();
-    int offset = num_parameters * kPointerSize;
-
-    __ li(RestParamAccessDescriptor::parameter_count(),
-          Operand(Smi::FromInt(num_parameters)));
-    __ Addu(RestParamAccessDescriptor::parameter_pointer(), fp,
-            Operand(StandardFrameConstants::kCallerSPOffset + offset));
-    __ li(RestParamAccessDescriptor::rest_parameter_index(),
-          Operand(Smi::FromInt(rest_index)));
-    DCHECK(a1.is(RestParamAccessDescriptor::rest_parameter_index()));
+    if (!function_in_register_a1) {
+      __ lw(a1, MemOperand(fp, JavaScriptFrameConstants::kFunctionOffset));
+    }
+    FastNewRestParameterStub stub(isolate());
+    __ CallStub(&stub);
     function_in_register_a1 = false;
-
-    RestParamAccessStub stub(isolate());
-    __ CallStub(&stub);
-
     SetVar(rest_param, v0, a1, a2);
   }
 
   Variable* arguments = scope()->arguments();
   if (arguments != NULL) {
     // Function uses arguments object.
     Comment cmnt(masm_, "[ Allocate arguments object");
     DCHECK(a1.is(ArgumentsAccessNewDescriptor::function()));
     if (!function_in_register_a1) {
       // Load this again, if it's used by the local context below.
@@ skipping 4396 matching lines @@
          reinterpret_cast<uint32_t>(
              isolate->builtins()->OsrAfterStackCheck()->entry()));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS