[interpreter] Move temporary register allocator into own file.

src/interpreter/bytecode-array-iterator.cc

Index: src/interpreter/bytecode-array-iterator.cc
diff --git a/src/interpreter/bytecode-array-iterator.cc b/src/interpreter/bytecode-array-iterator.cc
index fc9e2f5e9037615a2d18c64dd78700a682bfc219..4bb112bc948a8214ce367b8b1344ecc9974e702b 100644
--- a/src/interpreter/bytecode-array-iterator.cc
+++ b/src/interpreter/bytecode-array-iterator.cc
@@ -89,15 +89,28 @@ Register BytecodeArrayIterator::GetRegisterOperand(int operand_index) const {
       Bytecodes::GetOperandType(current_bytecode(), operand_index);
   DCHECK(Bytecodes::IsRegisterOperandType(operand_type));
   uint32_t operand = GetRawOperand(operand_index, operand_type);
+  Register reg;
   switch (Bytecodes::GetOperandSize(current_bytecode(), operand_index)) {
     case OperandSize::kByte:
-      return Register::FromOperand(static_cast<uint8_t>(operand));
+      reg = Register::FromOperand(static_cast<uint8_t>(operand));
+      break;
     case OperandSize::kShort:
-      return Register::FromWideOperand(static_cast<uint16_t>(operand));
+      reg = Register::FromWideOperand(static_cast<uint16_t>(operand));
+      break;
     case OperandSize::kNone:
       UNREACHABLE();
+      reg = Register::invalid_value();

[rmcilroy, 2016/02/02 10:53:28]

break;

[oth, 2016/02/02 11:20:24]

Done.

   }
-  return Register();
+  DCHECK_GE(reg.index(),
+            Register::FromParameterIndex(0, bytecode_array()->parameter_count())
+                .index());
+  DCHECK(reg.index() < bytecode_array()->register_count() ||
+         (reg.index() == 0 &&
+          (Bytecodes::GetOperandType(current_bytecode(), operand_index) ==
+               OperandType::kMaybeReg8 ||
+           Bytecodes::GetOperandType(current_bytecode(), operand_index) ==
+               OperandType::kMaybeReg16)));

[rmcilroy, 2016/02/02 10:53:28]

nit - could you pull out a helper for IsMaybeRegisterOperandType for this check?

[oth, 2016/02/02 11:20:24]

Done. Also IsRegisterCountOperandType used just below.

+  return reg;
 }
 
 int BytecodeArrayIterator::GetRegisterOperandRange(int operand_index) const {