[Interpreter] Enable assignments in expressions.

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 e34c6337b18db291a2c44ac3ad54dd0c1cf22617..64d828305e65a1e29a69d3b1ee5984375a3caaa8 100644
--- a/src/interpreter/bytecode-array-builder.cc
+++ b/src/interpreter/bytecode-array-builder.cc
@@ -276,11 +276,23 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::StoreAccumulatorInRegister(
     Register reg) {
   // TODO(oth): Avoid storing the accumulator in the register if the
   // previous bytecode loaded the accumulator with the same register.
+  //
+  // TODO(oth): If the previous bytecode is a MOV into this register,
+  // the previous instruction can be removed. The logic for determining
+  // these redundant MOVs appears complex.
   Output(Bytecode::kStar, reg.ToOperand());
   return *this;
 }
 
 
+BytecodeArrayBuilder& BytecodeArrayBuilder::MoveRegister(Register from,
+                                                         Register to) {
+  DCHECK(from != to);
+  Output(Bytecode::kMov, from.ToOperand(), to.ToOperand());
+  return *this;
+}
+
+
 BytecodeArrayBuilder& BytecodeArrayBuilder::LoadGlobal(
     size_t name_index, int feedback_slot, LanguageMode language_mode) {
   Bytecode bytecode = BytecodeForLoadGlobal(language_mode);