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

src/compiler/linkage.cc

 // 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.
 
 #include "src/ast/scopes.h"
 #include "src/code-stubs.h"
 #include "src/compiler.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/frame.h"
 #include "src/compiler/linkage.h"
@@ skipping 412 matching lines @@
       "interpreter-dispatch");
 }
 
 
 // TODO(all): Add support for return representations/locations to
 // CallInterfaceDescriptor.
 // TODO(turbofan): cache call descriptors for code stub calls.
 CallDescriptor* Linkage::GetStubCallDescriptor(
     Isolate* isolate, Zone* zone, const CallInterfaceDescriptor& descriptor,
     int stack_parameter_count, CallDescriptor::Flags flags,
-    Operator::Properties properties, MachineType return_type) {
+    Operator::Properties properties, MachineType return_type,
+    size_t return_count) {
   const int register_parameter_count = descriptor.GetRegisterParameterCount();
   const int js_parameter_count =
       register_parameter_count + stack_parameter_count;
   const int context_count = 1;
-  const size_t return_count = 1;
   const size_t parameter_count =
       static_cast<size_t>(js_parameter_count + context_count);
 
   LocationSignature::Builder locations(zone, return_count, parameter_count);
   MachineSignature::Builder types(zone, return_count, parameter_count);
 
-  // Add return location.
-  locations.AddReturn(regloc(kReturnRegister0));
-  types.AddReturn(return_type);
+  // Add returns.
+  if (locations.return_count_ > 0) {
+    locations.AddReturn(regloc(kReturnRegister0));
+  }
+  if (locations.return_count_ > 1) {
+    locations.AddReturn(regloc(kReturnRegister1));
+  }
+  for (size_t i = 0; i < return_count; i++) {
+    types.AddReturn(return_type);
+  }
 
   // Add parameters in registers and on the stack.
   for (int i = 0; i < js_parameter_count; i++) {
     if (i < register_parameter_count) {
       // The first parameters go in registers.
       Register reg = descriptor.GetRegisterParameter(i);
       Representation rep =
           RepresentationFromType(descriptor.GetParameterType(i));
       locations.AddParam(regloc(reg));
       types.AddParam(reptyp(rep));
@@ skipping 66 matching lines @@
   } else {
     DCHECK(loc == regloc(kContextRegister));
     return LinkageLocation::ForCalleeFrameSlot(Frame::kContextSlot);
   }
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8