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

src/interpreter/bytecode-array-builder.cc

Index: src/interpreter/bytecode-array-builder.cc
diff --git a/src/interpreter/bytecode-array-builder.cc b/src/interpreter/bytecode-array-builder.cc
index b901916b60b16df9d5c24db492526e12109ad991..33c51a699eed27f6f19e32738242c0eada57fae3 100644
--- a/src/interpreter/bytecode-array-builder.cc
+++ b/src/interpreter/bytecode-array-builder.cc
@@ -989,6 +989,7 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::New(Register constructor,
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::CallRuntime(
     Runtime::FunctionId function_id, Register first_arg, size_t arg_count) {
+  DCHECK_EQ(1, Runtime::FunctionForId(function_id)->result_size);
   DCHECK(FitsInIdx16Operand(function_id));
   DCHECK(FitsInIdx8Operand(arg_count));
   if (!first_arg.is_valid()) {
@@ -1001,6 +1002,23 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::CallRuntime(
 }
 
 
+BytecodeArrayBuilder& BytecodeArrayBuilder::CallRuntimePair(

[oth, 2016/01/06 15:09:17]

This doesn't look like it's called except in tests. Is more required to hook it
up to the bytecode generator?

[rmcilroy, 2016/01/06 15:23:25]

Yup, as mentioned in the CL message, this is tested in the Eval CL:
https://codereview.chromium.org/1508293003/

+    Runtime::FunctionId function_id, Register first_arg, size_t arg_count,
+    Register first_return) {
+  DCHECK_EQ(2, Runtime::FunctionForId(function_id)->result_size);
+  DCHECK(FitsInIdx16Operand(function_id));
+  DCHECK(FitsInIdx8Operand(arg_count));
+  if (!first_arg.is_valid()) {
+    DCHECK_EQ(0u, arg_count);
+    first_arg = Register(0);
+  }
+  Output(Bytecode::kCallRuntimePair, static_cast<uint16_t>(function_id),
+         first_arg.ToOperand(), static_cast<uint8_t>(arg_count),
+         first_return.ToOperand());
+  return *this;
+}
+
+
 BytecodeArrayBuilder& BytecodeArrayBuilder::CallJSRuntime(int context_index,
                                                           Register receiver,
                                                           size_t arg_count) {