[turbofan] Sparse representation for state values

src/compiler/instruction-selector.cc

Index: src/compiler/instruction-selector.cc
diff --git a/src/compiler/instruction-selector.cc b/src/compiler/instruction-selector.cc
index 8f899f3c8cb9b9549770281fbb5cac3cd67b8647..3333b643ea4f27e6b3e503f445177183c4cefc93 100644
--- a/src/compiler/instruction-selector.cc
+++ b/src/compiler/instruction-selector.cc
@@ -485,6 +485,13 @@ size_t AddOperandToStateValueDescriptor(StateValueDescriptor* descriptor,
                                         StateObjectDeduplicator* deduplicator,
                                         Node* input, MachineType type,
                                         FrameStateInputKind kind, Zone* zone) {
+  if (input == nullptr) {
+    inputs->push_back(g->TempImmediate(FrameStateDescriptor::kImpossibleValue));

[Jarin, 2016/11/16 15:32:42]

This should be the optimized_out value, no?

[Leszek Swirski, 2016/11/17 09:23:04]

Yeah, I had a problem here that the jsgraph isn't available, so I couldn't get
at that node. I figured that any value here would be sufficiently valid (if not
a great marker) for testing, so that I don't have to wire the jsgraph through
into here.

+    descriptor->fields().push_back(
+        StateValueDescriptor::Plain(zone, MachineType::None()));

[Jarin, 2016/11/16 15:32:42]

MachineType::AnyTagged()

[Leszek Swirski, 2016/11/17 09:23:04]

As above.

+    return 1;
+  }
+
   switch (input->opcode()) {
     case IrOpcode::kObjectState: {
       UNREACHABLE();