[Interpreter] Add support for calling runtime functions which return a pair.

src/compiler/linkage.h

 // Copyright 2014 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.
 
 #ifndef V8_COMPILER_LINKAGE_H_
 #define V8_COMPILER_LINKAGE_H_
 
 #include "src/base/flags.h"
 #include "src/compiler/frame.h"
 #include "src/compiler/operator.h"
@@ skipping 301 matching lines @@
   static CallDescriptor* GetRuntimeCallDescriptor(
       Zone* zone, Runtime::FunctionId function, int parameter_count,
       Operator::Properties properties, CallDescriptor::Flags flags);
 
   static CallDescriptor* GetLazyBailoutDescriptor(Zone* zone);
 
   static CallDescriptor* GetStubCallDescriptor(
       Isolate* isolate, Zone* zone, const CallInterfaceDescriptor& descriptor,
       int stack_parameter_count, CallDescriptor::Flags flags,
       Operator::Properties properties = Operator::kNoProperties,
-      MachineType return_type = MachineType::AnyTagged());
+      MachineType return_type = MachineType::AnyTagged(),
+      size_t return_count = 1);
 
   // Creates a call descriptor for simplified C calls that is appropriate
   // for the host platform. This simplified calling convention only supports
   // integers and pointers of one word size each, i.e. no floating point,
   // structs, pointers to members, etc.
   static CallDescriptor* GetSimplifiedCDescriptor(Zone* zone,
                                                   const MachineSignature* sig);
 
   // Creates a call descriptor for interpreter handler code stubs. These are not
   // intended to be called directly but are instead dispatched to by the
@@ skipping 62 matching lines @@
   CallDescriptor* const incoming_;
 
   DISALLOW_COPY_AND_ASSIGN(Linkage);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_LINKAGE_H_