[Interpreter] Implement ForIn in bytecode graph builder.

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index 22972537abcbccb0e72a702ba07e9e4eb12a011a..6c0faf7b349f1af6e4b5825b563379b6113c85f1 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -849,6 +849,16 @@ void BytecodeGenerator::VisitForInAssignment(Expression* expr,
 }
 
 
+void BytecodeGenerator::GetForInPreparedItem(Register destination, int index,
+                                             Register prepare_result,
+                                             Register scratch) {
+  builder()->LoadLiteral(Smi::FromInt(index));
+  builder()->StoreAccumulatorInRegister(scratch);
+  builder()->CallRuntime(Runtime::kFixedArrayGet, prepare_result, 2);
+  builder()->StoreAccumulatorInRegister(destination);
+}
+
+
 void BytecodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   EffectResultScope statement_result_scope(this);
 
@@ -873,26 +883,34 @@ void BytecodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   builder()->ForInPrepare(receiver);
   loop_builder.BreakIfUndefined();
 
-  Register for_in_state = execution_result()->NewRegister();
-  builder()->StoreAccumulatorInRegister(for_in_state);
+  // Ensure prepare_result and prepare_index are consecutive for CallRuntime.
+  execution_result()->PrepareForConsecutiveAllocations(2);
+  Register prepare_result = execution_result()->NewRegister();
+  Register prepare_index = execution_result()->NewRegister();
+  builder()->StoreAccumulatorInRegister(prepare_result);
+
+  // Spill the for_in_state to registers so we can de-opt.
+  Register cache_array = execution_result()->NewRegister();
+  GetForInPreparedItem(cache_array, 0, prepare_result, prepare_index);
+  Register cache_type = execution_result()->NewRegister();
+  GetForInPreparedItem(cache_type, 1, prepare_result, prepare_index);
+  Register cache_length = execution_result()->NewRegister();
+  GetForInPreparedItem(cache_length, 2, prepare_result, prepare_index);
 
   // Check loop termination (accumulator holds index).
-  Register index = receiver;  // Re-using register as receiver no longer used.
+  Register index = prepare_result;
   builder()->LoadLiteral(Smi::FromInt(0));
+  builder()->StoreAccumulatorInRegister(index);
   loop_builder.LoopHeader();
   loop_builder.Condition();
-  builder()->StoreAccumulatorInRegister(index).ForInDone(for_in_state);
+  builder()->ForInDone(index, cache_length);
   loop_builder.BreakIfTrue();
-  builder()->ForInNext(for_in_state, index);
+  builder()->ForInNext(receiver, index, cache_type, cache_array);
   loop_builder.ContinueIfUndefined();
-
   VisitForInAssignment(stmt->each(), stmt->EachFeedbackSlot());
   Visit(stmt->body());
-
-  // TODO(oth): replace CountOperation here with ForInStep.
   loop_builder.Next();
-  builder()->LoadAccumulatorWithRegister(index).CountOperation(
-      Token::Value::ADD, language_mode_strength());
+  builder()->ForInStep(index);
   loop_builder.JumpToHeader();
   loop_builder.LoopEnd();
 }