[turbofan] Add feedback to CheckMaps and Deoptimize nodes

Bug: v8:7127
Change-Id: I79be6acaa04623fe9a5d314de5cb10811724db5f
Reviewed-on: https://chromium-review.googlesource.com/814401
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49996}

src/compiler/branch-elimination.cc

@@ -103,8 +103,9 @@ Reduction BranchElimination::ReduceDeoptimizeConditional(Node* node) {
       // with the {control} node that already contains the right information.
       ReplaceWithValue(node, dead(), effect, control);
     } else {
-      control = graph()->NewNode(common()->Deoptimize(p.kind(), p.reason()),
-                                 frame_state, effect, control);
+      control = graph()->NewNode(
+          common()->Deoptimize(p.kind(), p.reason(), VectorSlotPair()),
+          frame_state, effect, control);
       // TODO(bmeurer): This should be on the AdvancedReducer somehow.
       NodeProperties::MergeControlToEnd(graph(), common(), control);
       Revisit(graph()->end());

src/compiler/common-operator-reducer.cc

@@ -138,9 +138,10 @@ Reduction CommonOperatorReducer::ReduceDeoptimizeConditional(Node* node) {
   if (condition->opcode() == IrOpcode::kBooleanNot) {
     NodeProperties::ReplaceValueInput(node, condition->InputAt(0), 0);
     NodeProperties::ChangeOp(
-        node, condition_is_true
-                  ? common()->DeoptimizeIf(p.kind(), p.reason())
-                  : common()->DeoptimizeUnless(p.kind(), p.reason()));
+        node, condition_is_true ? common()->DeoptimizeIf(p.kind(), p.reason(),
+                                                         VectorSlotPair())
+                                : common()->DeoptimizeUnless(
+                                      p.kind(), p.reason(), VectorSlotPair()));
     return Changed(node);
   }
   Decision const decision = DecideCondition(condition);
@@ -148,8 +149,9 @@ Reduction CommonOperatorReducer::ReduceDeoptimizeConditional(Node* node) {
   if (condition_is_true == (decision == Decision::kTrue)) {
     ReplaceWithValue(node, dead(), effect, control);
   } else {
-    control = graph()->NewNode(common()->Deoptimize(p.kind(), p.reason()),
-                               frame_state, effect, control);
+    control = graph()->NewNode(
+        common()->Deoptimize(p.kind(), p.reason(), VectorSlotPair()),
+        frame_state, effect, control);
     // TODO(bmeurer): This should be on the AdvancedReducer somehow.
     NodeProperties::MergeControlToEnd(graph(), common(), control);
     Revisit(graph()->end());

src/compiler/common-operator.cc

@@ -43,7 +43,8 @@ int ValueInputCountOfReturn(Operator const* const op) {
 }
 
 bool operator==(DeoptimizeParameters lhs, DeoptimizeParameters rhs) {
-  return lhs.kind() == rhs.kind() && lhs.reason() == rhs.reason();
+  return lhs.kind() == rhs.kind() && lhs.reason() == rhs.reason() &&
+         lhs.feedback() == rhs.feedback();
 }
 
 bool operator!=(DeoptimizeParameters lhs, DeoptimizeParameters rhs) {
@@ -51,11 +52,15 @@ bool operator!=(DeoptimizeParameters lhs, DeoptimizeParameters rhs) {
 }
 
 size_t hash_value(DeoptimizeParameters p) {
-  return base::hash_combine(p.kind(), p.reason());
+  return base::hash_combine(p.kind(), p.reason(), p.feedback());
 }
 
 std::ostream& operator<<(std::ostream& os, DeoptimizeParameters p) {
-  return os << p.kind() << ":" << p.reason();
+  os << p.kind() << ":" << p.reason();
+  if (p.feedback().IsValid()) {
+    os << "; " << p.feedback();
+  }
+  return os;
 }
 
 DeoptimizeParameters const& DeoptimizeParametersOf(Operator const* const op) {
@@ -606,7 +611,7 @@ struct CommonOperatorGlobalCache final {
               Operator::kFoldable | Operator::kNoThrow,  // properties
               "Deoptimize",                              // name
               1, 1, 1, 0, 0, 1,                          // counts
-              DeoptimizeParameters(kKind, kReason)) {}   // parameter
+              DeoptimizeParameters(kKind, kReason, VectorSlotPair())) {}
   };
 #define CACHED_DEOPTIMIZE(Kind, Reason)                                    \
   DeoptimizeOperator<DeoptimizeKind::k##Kind, DeoptimizeReason::k##Reason> \
@@ -622,7 +627,7 @@ struct CommonOperatorGlobalCache final {
               Operator::kFoldable | Operator::kNoThrow,  // properties
               "DeoptimizeIf",                            // name
               2, 1, 1, 0, 1, 1,                          // counts
-              DeoptimizeParameters(kKind, kReason)) {}   // parameter
+              DeoptimizeParameters(kKind, kReason, VectorSlotPair())) {}
   };
 #define CACHED_DEOPTIMIZE_IF(Kind, Reason)                                   \
   DeoptimizeIfOperator<DeoptimizeKind::k##Kind, DeoptimizeReason::k##Reason> \
@@ -639,7 +644,7 @@ struct CommonOperatorGlobalCache final {
               Operator::kFoldable | Operator::kNoThrow,  // properties
               "DeoptimizeUnless",                        // name
               2, 1, 1, 0, 1, 1,                          // counts
-              DeoptimizeParameters(kKind, kReason)) {}   // parameter
+              DeoptimizeParameters(kKind, kReason, VectorSlotPair())) {}
   };
 #define CACHED_DEOPTIMIZE_UNLESS(Kind, Reason)          \
   DeoptimizeUnlessOperator<DeoptimizeKind::k##Kind,     \
@@ -817,8 +822,9 @@ const Operator* CommonOperatorBuilder::Branch(BranchHint hint) {
   UNREACHABLE();
 }
 
-const Operator* CommonOperatorBuilder::Deoptimize(DeoptimizeKind kind,
-                                                  DeoptimizeReason reason) {
+const Operator* CommonOperatorBuilder::Deoptimize(
+    DeoptimizeKind kind, DeoptimizeReason reason,
+    VectorSlotPair const& feedback) {
 #define CACHED_DEOPTIMIZE(Kind, Reason)                 \
   if (kind == DeoptimizeKind::k##Kind &&                \
       reason == DeoptimizeReason::k##Reason) {          \
@@ -827,7 +833,7 @@ const Operator* CommonOperatorBuilder::Deoptimize(DeoptimizeKind kind,
   CACHED_DEOPTIMIZE_LIST(CACHED_DEOPTIMIZE)
 #undef CACHED_DEOPTIMIZE
   // Uncached
-  DeoptimizeParameters parameter(kind, reason);
+  DeoptimizeParameters parameter(kind, reason, feedback);
   return new (zone()) Operator1<DeoptimizeParameters>(  // --
       IrOpcode::kDeoptimize,                            // opcodes
       Operator::kFoldable | Operator::kNoThrow,         // properties
@@ -836,8 +842,9 @@ const Operator* CommonOperatorBuilder::Deoptimize(DeoptimizeKind kind,
       parameter);                                       // parameter
 }
 
-const Operator* CommonOperatorBuilder::DeoptimizeIf(DeoptimizeKind kind,
-                                                    DeoptimizeReason reason) {
+const Operator* CommonOperatorBuilder::DeoptimizeIf(
+    DeoptimizeKind kind, DeoptimizeReason reason,
+    VectorSlotPair const& feedback) {
 #define CACHED_DEOPTIMIZE_IF(Kind, Reason)                \
   if (kind == DeoptimizeKind::k##Kind &&                  \
       reason == DeoptimizeReason::k##Reason) {            \
@@ -846,7 +853,7 @@ const Operator* CommonOperatorBuilder::DeoptimizeIf(DeoptimizeKind kind,
   CACHED_DEOPTIMIZE_IF_LIST(CACHED_DEOPTIMIZE_IF)
 #undef CACHED_DEOPTIMIZE_IF
   // Uncached
-  DeoptimizeParameters parameter(kind, reason);
+  DeoptimizeParameters parameter(kind, reason, feedback);
   return new (zone()) Operator1<DeoptimizeParameters>(  // --
       IrOpcode::kDeoptimizeIf,                          // opcode
       Operator::kFoldable | Operator::kNoThrow,         // properties
@@ -856,7 +863,8 @@ const Operator* CommonOperatorBuilder::DeoptimizeIf(DeoptimizeKind kind,
 }
 
 const Operator* CommonOperatorBuilder::DeoptimizeUnless(
-    DeoptimizeKind kind, DeoptimizeReason reason) {
+    DeoptimizeKind kind, DeoptimizeReason reason,
+    VectorSlotPair const& feedback) {
 #define CACHED_DEOPTIMIZE_UNLESS(Kind, Reason)                \
   if (kind == DeoptimizeKind::k##Kind &&                      \
       reason == DeoptimizeReason::k##Reason) {                \
@@ -865,7 +873,7 @@ const Operator* CommonOperatorBuilder::DeoptimizeUnless(
   CACHED_DEOPTIMIZE_UNLESS_LIST(CACHED_DEOPTIMIZE_UNLESS)
 #undef CACHED_DEOPTIMIZE_UNLESS
   // Uncached
-  DeoptimizeParameters parameter(kind, reason);
+  DeoptimizeParameters parameter(kind, reason, feedback);
   return new (zone()) Operator1<DeoptimizeParameters>(  // --
       IrOpcode::kDeoptimizeUnless,                      // opcode
       Operator::kFoldable | Operator::kNoThrow,         // properties

src/compiler/common-operator.h

@@ -11,6 +11,7 @@
 #include "src/deoptimize-reason.h"
 #include "src/globals.h"
 #include "src/machine-type.h"
+#include "src/vector-slot-pair.h"
 #include "src/zone/zone-containers.h"
 #include "src/zone/zone-handle-set.h"
 
@@ -52,15 +53,18 @@ int ValueInputCountOfReturn(Operator const* const op);
 // Parameters for the {Deoptimize} operator.
 class DeoptimizeParameters final {
  public:
-  DeoptimizeParameters(DeoptimizeKind kind, DeoptimizeReason reason)
-      : kind_(kind), reason_(reason) {}
+  DeoptimizeParameters(DeoptimizeKind kind, DeoptimizeReason reason,
+                       VectorSlotPair const& feedback)
+      : kind_(kind), reason_(reason), feedback_(feedback) {}
 
   DeoptimizeKind kind() const { return kind_; }
   DeoptimizeReason reason() const { return reason_; }
+  const VectorSlotPair& feedback() const { return feedback_; }
 
  private:
   DeoptimizeKind const kind_;
   DeoptimizeReason const reason_;
+  VectorSlotPair const feedback_;
 };
 
 bool operator==(DeoptimizeParameters, DeoptimizeParameters);
@@ -358,10 +362,12 @@ class V8_EXPORT_PRIVATE CommonOperatorBuilder final
   const Operator* IfValue(int32_t value);
   const Operator* IfDefault();
   const Operator* Throw();
-  const Operator* Deoptimize(DeoptimizeKind kind, DeoptimizeReason reason);
-  const Operator* DeoptimizeIf(DeoptimizeKind kind, DeoptimizeReason reason);
-  const Operator* DeoptimizeUnless(DeoptimizeKind kind,
-                                   DeoptimizeReason reason);
+  const Operator* Deoptimize(DeoptimizeKind kind, DeoptimizeReason reason,
+                             VectorSlotPair const& feedback);
+  const Operator* DeoptimizeIf(DeoptimizeKind kind, DeoptimizeReason reason,
+                               VectorSlotPair const& feedback);
+  const Operator* DeoptimizeUnless(DeoptimizeKind kind, DeoptimizeReason reason,
+                                   VectorSlotPair const& feedback);
   const Operator* TrapIf(int32_t trap_id);
   const Operator* TrapUnless(int32_t trap_id);
   const Operator* Return(int value_input_count = 1);

src/compiler/effect-control-linearizer.cc

@@ -1355,7 +1355,7 @@ void EffectControlLinearizer::LowerCheckMaps(Node* node, Node* frame_state) {
                        __ Int32Constant(Map::IsDeprecatedBit::kMask)),
           __ Int32Constant(0));
       __ DeoptimizeIf(DeoptimizeReason::kWrongMap, if_not_deprecated,
-                      frame_state);
+                      frame_state, p.feedback());
 
       Operator::Properties properties = Operator::kNoDeopt | Operator::kNoThrow;
       Runtime::FunctionId id = Runtime::kTryMigrateInstance;
@@ -1367,7 +1367,7 @@ void EffectControlLinearizer::LowerCheckMaps(Node* node, Node* frame_state) {
                   __ Int32Constant(1), __ NoContextConstant());
       Node* check = ObjectIsSmi(result);
       __ DeoptimizeIf(DeoptimizeReason::kInstanceMigrationFailed, check,
-                      frame_state);
+                      frame_state, p.feedback());
     }
 
     // Reload the current map of the {value}.
@@ -1378,7 +1378,8 @@ void EffectControlLinearizer::LowerCheckMaps(Node* node, Node* frame_state) {
       Node* map = __ HeapConstant(maps[i]);
       Node* check = __ WordEqual(value_map, map);
       if (i == map_count - 1) {
-        __ DeoptimizeIfNot(DeoptimizeReason::kWrongMap, check, frame_state);
+        __ DeoptimizeIfNot(DeoptimizeReason::kWrongMap, check, frame_state,
+                           p.feedback());
       } else {
         __ GotoIf(check, &done);
       }
@@ -1396,7 +1397,8 @@ void EffectControlLinearizer::LowerCheckMaps(Node* node, Node* frame_state) {
       Node* map = __ HeapConstant(maps[i]);
       Node* check = __ WordEqual(value_map, map);
       if (i == map_count - 1) {
-        __ DeoptimizeIfNot(DeoptimizeReason::kWrongMap, check, frame_state);
+        __ DeoptimizeIfNot(DeoptimizeReason::kWrongMap, check, frame_state,
+                           p.feedback());
       } else {
         __ GotoIf(check, &done);
       }
@@ -1524,7 +1526,7 @@ Node* EffectControlLinearizer::LowerCheckInternalizedString(Node* node,
 void EffectControlLinearizer::LowerCheckIf(Node* node, Node* frame_state) {
   Node* value = node->InputAt(0);
   __ DeoptimizeIfNot(DeoptimizeKind::kEager, DeoptimizeReasonOf(node->op()),
-                     value, frame_state);
+                     value, frame_state, VectorSlotPair());
 }
 
 Node* EffectControlLinearizer::LowerCheckedInt32Add(Node* node,

src/compiler/graph-assembler.cc

@@ -165,24 +165,27 @@ Node* GraphAssembler::ToNumber(Node* value) {
 }
 
 Node* GraphAssembler::DeoptimizeIf(DeoptimizeReason reason, Node* condition,
-                                   Node* frame_state) {
+                                   Node* frame_state,
+                                   VectorSlotPair const& feedback) {
   return current_control_ = current_effect_ = graph()->NewNode(
-             common()->DeoptimizeIf(DeoptimizeKind::kEager, reason), condition,
-             frame_state, current_effect_, current_control_);
+             common()->DeoptimizeIf(DeoptimizeKind::kEager, reason, feedback),
+             condition, frame_state, current_effect_, current_control_);
 }
 
 Node* GraphAssembler::DeoptimizeIfNot(DeoptimizeKind kind,
                                       DeoptimizeReason reason, Node* condition,
-                                      Node* frame_state) {
+                                      Node* frame_state,
+                                      VectorSlotPair const& feedback) {
   return current_control_ = current_effect_ = graph()->NewNode(
-             common()->DeoptimizeUnless(kind, reason), condition, frame_state,
-             current_effect_, current_control_);
+             common()->DeoptimizeUnless(kind, reason, feedback), condition,
+             frame_state, current_effect_, current_control_);
 }
 
 Node* GraphAssembler::DeoptimizeIfNot(DeoptimizeReason reason, Node* condition,
-                                      Node* frame_state) {
-  return DeoptimizeIfNot(DeoptimizeKind::kEager, reason, condition,
-                         frame_state);
+                                      Node* frame_state,
+                                      VectorSlotPair const& feedback) {
+  return DeoptimizeIfNot(DeoptimizeKind::kEager, reason, condition, frame_state,
+                         feedback);
 }
 
 void GraphAssembler::Branch(Node* condition, GraphAssemblerLabel<0u>* if_true,

src/compiler/graph-assembler.h

@@ -8,6 +8,7 @@
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node.h"
 #include "src/compiler/simplified-operator.h"
+#include "src/vector-slot-pair.h"
 
 namespace v8 {
 namespace internal {
@@ -209,11 +210,14 @@ class GraphAssembler {
   Node* UnsafePointerAdd(Node* base, Node* external);
 
   Node* DeoptimizeIf(DeoptimizeReason reason, Node* condition,
-                     Node* frame_state);
+                     Node* frame_state,
+                     VectorSlotPair const& feedback = VectorSlotPair());
   Node* DeoptimizeIfNot(DeoptimizeKind kind, DeoptimizeReason reason,
-                        Node* condition, Node* frame_state);
+                        Node* condition, Node* frame_state,
+                        VectorSlotPair const& feedback);
   Node* DeoptimizeIfNot(DeoptimizeReason reason, Node* condition,
-                        Node* frame_state);
+                        Node* frame_state,
+                        VectorSlotPair const& feedback = VectorSlotPair());
   template <typename... Args>
   Node* Call(const CallDescriptor* desc, Args... args);
   template <typename... Args>

src/compiler/js-call-reducer.cc

@@ -2485,9 +2485,9 @@ Reduction JSCallReducer::ReduceSoftDeoptimize(Node* node,
   Node* effect = NodeProperties::GetEffectInput(node);
   Node* control = NodeProperties::GetControlInput(node);
   Node* frame_state = NodeProperties::FindFrameStateBefore(node);
-  Node* deoptimize =
-      graph()->NewNode(common()->Deoptimize(DeoptimizeKind::kSoft, reason),
-                       frame_state, effect, control);
+  Node* deoptimize = graph()->NewNode(
+      common()->Deoptimize(DeoptimizeKind::kSoft, reason, VectorSlotPair()),
+      frame_state, effect, control);
   // TODO(bmeurer): This should be on the AdvancedReducer somehow.
   NodeProperties::MergeControlToEnd(graph(), common(), deoptimize);
   Revisit(graph()->end());

src/compiler/js-intrinsic-lowering.cc

@@ -135,7 +135,8 @@ Reduction JSIntrinsicLowering::ReduceDeoptimizeNow(Node* node) {
 
   // TODO(bmeurer): Move MergeControlToEnd() to the AdvancedReducer.
   Node* deoptimize = graph()->NewNode(
-      common()->Deoptimize(DeoptimizeKind::kEager, DeoptimizeReason::kNoReason),
+      common()->Deoptimize(DeoptimizeKind::kEager, DeoptimizeReason::kNoReason,
+                           VectorSlotPair()),
       frame_state, effect, control);
   NodeProperties::MergeControlToEnd(graph(), common(), deoptimize);
   Revisit(graph()->end());

src/compiler/js-native-context-specialization.cc

@@ -1424,9 +1424,9 @@ Reduction JSNativeContextSpecialization::ReduceSoftDeoptimize(
   Node* effect = NodeProperties::GetEffectInput(node);
   Node* control = NodeProperties::GetControlInput(node);
   Node* frame_state = NodeProperties::FindFrameStateBefore(node);
-  Node* deoptimize =
-      graph()->NewNode(common()->Deoptimize(DeoptimizeKind::kSoft, reason),
-                       frame_state, effect, control);
+  Node* deoptimize = graph()->NewNode(
+      common()->Deoptimize(DeoptimizeKind::kSoft, reason, VectorSlotPair()),
+      frame_state, effect, control);
   // TODO(bmeurer): This should be on the AdvancedReducer somehow.
   NodeProperties::MergeControlToEnd(graph(), common(), deoptimize);
   Revisit(graph()->end());

src/compiler/js-type-hint-lowering.cc

@@ -493,7 +493,8 @@ Node* JSTypeHintLowering::TryBuildSoftDeopt(FeedbackNexus& nexus, Node* effect,
                                             DeoptimizeReason reason) const {
   if ((flags() & kBailoutOnUninitialized) && nexus.IsUninitialized()) {
     Node* deoptimize = jsgraph()->graph()->NewNode(
-        jsgraph()->common()->Deoptimize(DeoptimizeKind::kSoft, reason),
+        jsgraph()->common()->Deoptimize(DeoptimizeKind::kSoft, reason,
+                                        VectorSlotPair()),
         jsgraph()->Dead(), effect, control);
     Node* frame_state = NodeProperties::FindFrameStateBefore(deoptimize);
     deoptimize->ReplaceInput(0, frame_state);

src/compiler/simplified-operator.cc

@@ -215,15 +215,20 @@ size_t hash_value(MapsParameterInfo const& p) { return hash_value(p.maps()); }
 
 bool operator==(CheckMapsParameters const& lhs,
                 CheckMapsParameters const& rhs) {
-  return lhs.flags() == rhs.flags() && lhs.maps() == rhs.maps();
+  return lhs.flags() == rhs.flags() && lhs.maps() == rhs.maps() &&
+         lhs.feedback() == rhs.feedback();
 }
 
 size_t hash_value(CheckMapsParameters const& p) {
-  return base::hash_combine(p.flags(), p.maps());
+  return base::hash_combine(p.flags(), p.maps(), p.feedback());
 }
 
 std::ostream& operator<<(std::ostream& os, CheckMapsParameters const& p) {
-  return os << p.flags() << p.maps_info();
+  os << p.flags() << p.maps_info();
+  if (p.feedback().IsValid()) {
+    os << "; " << p.feedback();
+  }
+  return os;
 }
 
 CheckMapsParameters const& CheckMapsParametersOf(Operator const* op) {
@@ -1021,9 +1026,10 @@ const Operator* SimplifiedOperatorBuilder::CheckedTruncateTaggedToWord32(
   UNREACHABLE();
 }
 
-const Operator* SimplifiedOperatorBuilder::CheckMaps(CheckMapsFlags flags,
-                                                     ZoneHandleSet<Map> maps) {
-  CheckMapsParameters const parameters(flags, maps);
+const Operator* SimplifiedOperatorBuilder::CheckMaps(
+    CheckMapsFlags flags, ZoneHandleSet<Map> maps,
+    const VectorSlotPair& feedback) {
+  CheckMapsParameters const parameters(flags, maps, feedback);
   return new (zone()) Operator1<CheckMapsParameters>(  // --
       IrOpcode::kCheckMaps,                            // opcode
       Operator::kNoThrow | Operator::kNoWrite,         // flags

src/compiler/simplified-operator.h

@@ -16,6 +16,7 @@
 #include "src/machine-type.h"
 #include "src/objects.h"
 #include "src/type-hints.h"
+#include "src/vector-slot-pair.h"
 #include "src/zone/zone-handle-set.h"
 
 namespace v8 {
@@ -155,19 +156,24 @@ bool operator!=(MapsParameterInfo const&, MapsParameterInfo const&);
 
 size_t hash_value(MapsParameterInfo const&);
 
-// A descriptor for map checks.
+// A descriptor for map checks. The {feedback} parameter is optional.
+// If {feedback} references a valid CallIC slot and this MapCheck fails,
+// then speculation on that CallIC slot will be disabled.
 class CheckMapsParameters final {
  public:
-  CheckMapsParameters(CheckMapsFlags flags, ZoneHandleSet<Map> const& maps)
-      : flags_(flags), maps_info_(maps) {}
+  CheckMapsParameters(CheckMapsFlags flags, ZoneHandleSet<Map> const& maps,
+                      const VectorSlotPair& feedback)
+      : flags_(flags), maps_info_(maps), feedback_(feedback) {}
 
   CheckMapsFlags flags() const { return flags_; }
   ZoneHandleSet<Map> const& maps() const { return maps_info_.maps(); }
   MapsParameterInfo const& maps_info() const { return maps_info_; }
+  VectorSlotPair const& feedback() const { return feedback_; }
 
  private:
   CheckMapsFlags const flags_;
   MapsParameterInfo const maps_info_;
+  VectorSlotPair const feedback_;
 };
 
 bool operator==(CheckMapsParameters const&, CheckMapsParameters const&);
@@ -438,7 +444,8 @@ class V8_EXPORT_PRIVATE SimplifiedOperatorBuilder final
 
   const Operator* CheckIf(DeoptimizeReason deoptimize_reason);
   const Operator* CheckBounds();
-  const Operator* CheckMaps(CheckMapsFlags, ZoneHandleSet<Map>);
+  const Operator* CheckMaps(CheckMapsFlags, ZoneHandleSet<Map>,
+                            const VectorSlotPair& = VectorSlotPair());
   const Operator* CompareMaps(ZoneHandleSet<Map>);
   const Operator* MapGuard(ZoneHandleSet<Map> maps);