[turbofan] Sparse representation for state values

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index 5dcb37fae83f3b098278c203a7d4823c6d259314..f5bcab1617bfe291fab5c1fb7a41457e5d7fb517 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -1010,8 +1010,9 @@ class RepresentationSelector {
                machine_type.semantic() == MachineSemantic::kUint32);
         (*types)[i] = machine_type;
       }
-      NodeProperties::ChangeOp(node,
-                               jsgraph_->common()->TypedStateValues(types));
+      uint32_t mask = OpParameter<uint32_t>(node);

[Jarin, 2016/12/07 08:56:20]

Descriptive name, please.

You should not use OpParameter directly, please, define an accessor in
common-operator.*.

OpParamater is very dangerous because if you decide to change the parameter type
(in CommonOperatorBuilder::StateValues), compiler will not complain about type
mismatch and you will start seeing random "mask". We already had serious bugs
here.

[Leszek Swirski, 2016/12/08 15:44:30]

Done, throughout. Interesting point about the type mismatch, I'm not sure I see
how the accessors in common-operator (which are just wrappers around
OpParameter) help with this?

+      NodeProperties::ChangeOp(
+          node, jsgraph_->common()->TypedStateValues(types, mask));
     }
     SetOutput(node, MachineRepresentation::kTagged);
   }