[turbofan] Introduce JSCallForwardVarargs operator.

src/arm64/interface-descriptors-arm64.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.
 
 #include "src/arm64/interface-descriptors-arm64.h"
 
 #if V8_TARGET_ARCH_ARM64
 
 #include "src/interface-descriptors.h"
 
@@ skipping 182 matching lines @@
 
 
 void CallTrampolineDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   // x1: target
   // x0: number of arguments
   Register registers[] = {x1, x0};
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
+void CallForwardVarargsDescriptor::InitializePlatformSpecific(
+    CallInterfaceDescriptorData* data) {
+  // x1: target
+  // x2: start index (to supported rest parameters)
+  Register registers[] = {x1, x2};
+  data->InitializePlatformSpecific(arraysize(registers), registers);
+}
 
 void ConstructStubDescriptor::InitializePlatformSpecific(
     CallInterfaceDescriptorData* data) {
   // x3: new target
   // x1: target
   // x0: number of arguments
   // x2: allocation site or undefined
   Register registers[] = {x1, x3, x0, x2};
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
@@ skipping 245 matching lines @@
       x1,  // the JSGeneratorObject to resume
       x2   // the resume mode (tagged)
   };
   data->InitializePlatformSpecific(arraysize(registers), registers);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64