[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..b658460b058144339965e16df19eb6f36ca0722f 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -851,7 +851,6 @@ void BytecodeGenerator::VisitForInAssignment(Expression* expr,
 
 void BytecodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   EffectResultScope statement_result_scope(this);
-
   if (stmt->subject()->IsNullLiteral() ||
       stmt->subject()->IsUndefinedLiteral(isolate())) {
     // ForIn generates lots of code, skip if it wouldn't produce any effects.
@@ -870,29 +869,26 @@ void BytecodeGenerator::VisitForInStatement(ForInStatement* stmt) {
   builder()->CastAccumulatorToJSObject();
   builder()->StoreAccumulatorInRegister(receiver);
   builder()->CallRuntime(Runtime::kGetPropertyNamesFast, receiver, 1);
-  builder()->ForInPrepare(receiver);
+  Register cache_type = execution_result()->NewRegister();
+  Register cache_array = execution_result()->NewRegister();
+  Register cache_length = execution_result()->NewRegister();
+  builder()->ForInPrepare(receiver, cache_type, cache_array, cache_length);
   loop_builder.BreakIfUndefined();

[Benedikt Meurer, 2015/12/16 20:00:14]

This looks wrong/unnecessary (now). As far as I can tell the ForInPrepare sets
the accumulator to the FixedArray returned by the interpreter wrapper for the
runtime call, so it's for sure never undefined.

 
-  Register for_in_state = execution_result()->NewRegister();
-  builder()->StoreAccumulatorInRegister(for_in_state);
-
   // Check loop termination (accumulator holds index).
-  Register index = receiver;  // Re-using register as receiver no longer used.
+  Register index = execution_result()->NewRegister();
   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, cache_type, cache_array, index);
   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();
 }