Allow Turbofan optimization of Ignition generators

src/interpreter/interpreter-assembler.cc

Index: src/interpreter/interpreter-assembler.cc
diff --git a/src/interpreter/interpreter-assembler.cc b/src/interpreter/interpreter-assembler.cc
index db9b0cb3c0f3f557140524e373a31c0b651fd1d8..a32b4a63eeb8a8772ff4660eb4757789718442c1 100644
--- a/src/interpreter/interpreter-assembler.cc
+++ b/src/interpreter/interpreter-assembler.cc
@@ -726,6 +726,8 @@ Node* InterpreterAssembler::ExportRegisterFile(Node* array) {
   var_index.Bind(Int32Constant(0));
 
   // Iterate over register file and write values into array.
+  // The mapping of register to array index must match that used in
+  // BytecodeGraphBuilder::VisitResumeGenerator.
   Label loop(this, &var_index), done_loop(this);
   Goto(&loop);
   Bind(&loop);