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

src/interpreter/interpreter.cc

 // Copyright 2015 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/interpreter/interpreter.h"
 
 #include "src/code-factory.h"
 #include "src/compiler.h"
 #include "src/compiler/interpreter-assembler.h"
 #include "src/factory.h"
@@ skipping 1028 matching lines @@
   Node* function_id = __ BytecodeOperandIdx(0);
   Node* first_arg_reg = __ BytecodeOperandReg(1);
   Node* first_arg = __ RegisterLocation(first_arg_reg);
   Node* args_count = __ BytecodeOperandCount(2);
   Node* result = __ CallRuntime(function_id, first_arg, args_count);
   __ SetAccumulator(result);
   __ Dispatch();
 }
 
 
+// CallRuntimePair <function_id> <first_arg> <arg_count> <first_return>
+//
+// Call the runtime function |function_id| which returns a pair, with the
+// first argument in register |first_arg| and |arg_count| arguments in
+// subsequent registers.
+void Interpreter::DoCallRuntimePair(compiler::InterpreterAssembler* assembler) {
+  // Call the runtime function.
+  Node* function_id = __ BytecodeOperandIdx(0);
+  Node* first_arg_reg = __ BytecodeOperandReg(1);
+  Node* first_arg = __ RegisterLocation(first_arg_reg);
+  Node* args_count = __ BytecodeOperandCount(2);
+  Node* result_pair = __ CallRuntimePair(function_id, first_arg, args_count);
+
+  // Store the results in <first_return> and <first_return + 1>
+  Node* first_return_reg = __ BytecodeOperandReg(3);
+  Node* second_return_reg = __ NextRegister(first_return_reg);
+  Node* result_0 = __ Projection(0, result_pair);

[oth, 2016/01/06 16:26:07]

More widely used convention result0, result1, e.g. reg0, reg1, operand0,
operand1.

[rmcilroy, 2016/01/07 17:21:43]

Done.

+  Node* result_1 = __ Projection(1, result_pair);
+  __ StoreRegister(result_0, first_return_reg);
+  __ StoreRegister(result_1, second_return_reg);
+
+  __ Dispatch();
+}
+
+
 // CallJSRuntime <context_index> <receiver> <arg_count>
 //
 // Call the JS runtime function that has the |context_index| with the receiver
 // in register |receiver| and |arg_count| arguments in subsequent registers.
 void Interpreter::DoCallJSRuntime(compiler::InterpreterAssembler* assembler) {
   Node* context_index = __ BytecodeOperandIdx(0);
   Node* receiver_reg = __ BytecodeOperandReg(1);
   Node* first_arg = __ RegisterLocation(receiver_reg);
   Node* args_count = __ BytecodeOperandCount(2);
 
@@ skipping 555 matching lines @@
   Node* index_reg = __ BytecodeOperandReg(0);
   Node* index = __ LoadRegister(index_reg);
   Node* result = __ CallRuntime(Runtime::kForInStep, index);
   __ SetAccumulator(result);
   __ Dispatch();
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8