Save/restore only live registers in the generator suspend/resume.

src/interpreter/bytecode-register-optimizer.cc

Index: src/interpreter/bytecode-register-optimizer.cc
diff --git a/src/interpreter/bytecode-register-optimizer.cc b/src/interpreter/bytecode-register-optimizer.cc
index 859f0e18285bf86589ea731a5c56dfa7f08fd48c..850d4bd377eb380708bb7299e0eeb08ff957a522 100644
--- a/src/interpreter/bytecode-register-optimizer.cc
+++ b/src/interpreter/bytecode-register-optimizer.cc
@@ -246,6 +246,8 @@ void BytecodeRegisterOptimizer::Flush() {
         }
         equivalent->MoveToNewEquivalenceSet(NextEquivalenceId(), true);
       }
+    } else if (reg_info->GetEquivalent() == reg_info) {
+      reg_info->MoveToNewEquivalenceSet(NextEquivalenceId(), true);

[rmcilroy, 2017/06/01 10:44:44]

Why do these need moved here? If it's because they don't count as materialized,
could we instead initialize registers as being materialized in the constructor /
GrowRegisterMap? (Flush is already expensive, so I'd rather not do more work
here if possible)

[Jarin, 2017/06/01 12:48:22]

Yes, it's because they do not count as materialized. I had added this code
because it seemed to be the safest option. 

Now it is removed and the materialization is set in GrowRegisterMap.

Thanks for the suggestion!

     }
   }
 
@@ -304,6 +306,7 @@ BytecodeRegisterOptimizer::GetMaterializedEquivalentNotAccumulator(
 void BytecodeRegisterOptimizer::Materialize(RegisterInfo* info) {
   if (!info->materialized()) {
     RegisterInfo* materialized = info->GetMaterializedEquivalent();
+    DCHECK_NOT_NULL(materialized);
     OutputRegisterTransfer(materialized, info);
   }
 }