[turbofan] Introduce a dedicated CompareMaps operator.

Instead of introducing a lot of explicit branching in the
JSNativeContextSpecialization for polymorphic property accesses
that cannot be folded into a single LoadField/StoreField, and which
are mostly invisible and not optimizable for later passes, we now
have a single CompareMaps operator that takes a set of maps (like the
CheckMaps operator) and produces a boolean indicating the result of
the comparison.

R=jarin@chromium.org

Bug: v8:6761
Change-Id: Iee8788e915b762d542acb54feb9931346e442dc0
Reviewed-on: https://chromium-review.googlesource.com/636365Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47635}

src/compiler/effect-control-linearizer.cc

@@ -629,6 +629,9 @@ bool EffectControlLinearizer::TryWireInStateEffect(Node* node,
     case IrOpcode::kCheckMaps:
       result = LowerCheckMaps(node, frame_state);
       break;
+    case IrOpcode::kCompareMaps:
+      result = LowerCompareMaps(node);
+      break;
     case IrOpcode::kCheckMapValue:
       LowerCheckMapValue(node, frame_state);
       break;
@@ -1287,6 +1290,28 @@ Node* EffectControlLinearizer::LowerCheckMaps(Node* node, Node* frame_state) {
   return value;
 }
 
+Node* EffectControlLinearizer::LowerCompareMaps(Node* node) {
+  ZoneHandleSet<Map> const& maps = CompareMapsParametersOf(node->op());
+  size_t const map_count = maps.size();
+  Node* value = node->InputAt(0);
+
+  auto done = __ MakeLabelFor(GraphAssemblerLabelType::kNonDeferred,
+                              map_count + 1, MachineRepresentation::kBit);
+
+  // Load the current map of the {value}.
+  Node* value_map = __ LoadField(AccessBuilder::ForMap(), value);
+
+  for (size_t i = 0; i < map_count; ++i) {
+    Node* map = __ HeapConstant(maps[i]);
+    Node* check = __ WordEqual(value_map, map);
+    __ GotoIf(check, &done, __ Int32Constant(1));
+  }
+  __ Goto(&done, __ Int32Constant(0));
+
+  __ Bind(&done);
+  return done.PhiAt(0);
+}
+
 void EffectControlLinearizer::LowerCheckMapValue(Node* node,
                                                  Node* frame_state) {
   Node* value = node->InputAt(0);

src/compiler/effect-control-linearizer.h

@@ -55,6 +55,7 @@ class V8_EXPORT_PRIVATE EffectControlLinearizer {
   Node* LowerCheckBounds(Node* node, Node* frame_state);
   Node* LowerCheckInternalizedString(Node* node, Node* frame_state);
   Node* LowerCheckMaps(Node* node, Node* frame_state);
+  Node* LowerCompareMaps(Node* node);
   void LowerCheckMapValue(Node* node, Node* frame_state);
   Node* LowerCheckNumber(Node* node, Node* frame_state);
   Node* LowerCheckReceiver(Node* node, Node* frame_state);

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

@@ -765,12 +765,6 @@ Reduction JSNativeContextSpecialization::ReduceNamedAccess(
           access_builder.BuildCheckHeapObject(receiver, &effect, control);
     }
 
-    // Load the {receiver} map. The resulting effect is the dominating effect
-    // for all (polymorphic) branches.
-    Node* receiver_map = effect =
-        graph()->NewNode(simplified()->LoadField(AccessBuilder::ForMap()),
-                         receiver, effect, control);
-
     // Generate code for the various different property access patterns.
     Node* fallthrough_control = control;
     for (size_t j = 0; j < access_infos.size(); ++j) {
@@ -787,16 +781,12 @@ Reduction JSNativeContextSpecialization::ReduceNamedAccess(
         // effect to be able to learn from the control flow.
         bool insert_map_guard = true;
 
-        // Emit a (sequence of) map checks for other {receiver}s.
-        ZoneVector<Node*> this_controls(zone());
-        ZoneVector<Node*> this_effects(zone());
+        // Check maps for the {receiver}s.
         if (j == access_infos.size() - 1) {
           // Last map check on the fallthrough control path, do a
           // conditional eager deoptimization exit here.
           access_builder.BuildCheckMaps(receiver, &this_effect, this_control,
                                         receiver_maps);
-          this_effects.push_back(this_effect);
-          this_controls.push_back(fallthrough_control);
           fallthrough_control = nullptr;
 
           // Don't insert a MapGuard in this case, as the CheckMaps
@@ -804,17 +794,18 @@ Reduction JSNativeContextSpecialization::ReduceNamedAccess(
           // along the effect chain.
           insert_map_guard = false;
         } else {
-          for (auto map : receiver_maps) {
-            Node* check =
-                graph()->NewNode(simplified()->ReferenceEqual(), receiver_map,
-                                 jsgraph()->Constant(map));
-            Node* branch = graph()->NewNode(common()->Branch(), check,
-                                            fallthrough_control);
-            fallthrough_control = graph()->NewNode(common()->IfFalse(), branch);
-            this_controls.push_back(
-                graph()->NewNode(common()->IfTrue(), branch));
-            this_effects.push_back(this_effect);
+          // Explicitly branch on the {receiver_maps}.
+          ZoneHandleSet<Map> maps;
+          for (Handle<Map> map : receiver_maps) {
+            maps.insert(map, graph()->zone());
           }
+          Node* check = this_effect =
+              graph()->NewNode(simplified()->CompareMaps(maps), receiver,
+                               this_effect, this_control);
+          Node* branch =
+              graph()->NewNode(common()->Branch(), check, this_control);
+          fallthrough_control = graph()->NewNode(common()->IfFalse(), branch);
+          this_control = graph()->NewNode(common()->IfTrue(), branch);
         }
 
         // The Number case requires special treatment to also deal with Smis.
@@ -822,8 +813,10 @@ Reduction JSNativeContextSpecialization::ReduceNamedAccess(
           // Join this check with the "receiver is smi" check above.
           DCHECK_NOT_NULL(receiverissmi_effect);
           DCHECK_NOT_NULL(receiverissmi_control);
-          this_effects.push_back(receiverissmi_effect);
-          this_controls.push_back(receiverissmi_control);
+          this_control = graph()->NewNode(common()->Merge(2), this_control,
+                                          receiverissmi_control);
+          this_effect = graph()->NewNode(common()->EffectPhi(2), this_effect,
+                                         receiverissmi_effect, this_control);
           receiverissmi_effect = receiverissmi_control = nullptr;
 
           // The {receiver} can also be a Smi in this case, so
@@ -831,21 +824,6 @@ Reduction JSNativeContextSpecialization::ReduceNamedAccess(
           insert_map_guard = false;
         }
 
-        // Create single chokepoint for the control.
-        int const this_control_count = static_cast<int>(this_controls.size());
-        if (this_control_count == 1) {
-          this_control = this_controls.front();
-          this_effect = this_effects.front();
-        } else {
-          this_control =
-              graph()->NewNode(common()->Merge(this_control_count),
-                               this_control_count, &this_controls.front());
-          this_effects.push_back(this_control);
-          this_effect =
-              graph()->NewNode(common()->EffectPhi(this_control_count),
-                               this_control_count + 1, &this_effects.front());
-        }
-
         // Introduce a MapGuard to learn from this on the effect chain.
         if (insert_map_guard) {
           ZoneHandleSet<Map> maps;

src/compiler/load-elimination.cc

@@ -102,6 +102,8 @@ Reduction LoadElimination::Reduce(Node* node) {
       return ReduceMapGuard(node);
     case IrOpcode::kCheckMaps:
       return ReduceCheckMaps(node);
+    case IrOpcode::kCompareMaps:
+      return ReduceCompareMaps(node);
     case IrOpcode::kEnsureWritableFastElements:
       return ReduceEnsureWritableFastElements(node);
     case IrOpcode::kMaybeGrowFastElements:
@@ -695,6 +697,24 @@ Reduction LoadElimination::ReduceCheckMaps(Node* node) {
   return UpdateState(node, state);
 }
 
+Reduction LoadElimination::ReduceCompareMaps(Node* node) {
+  ZoneHandleSet<Map> const maps = CompareMapsParametersOf(node->op());
+  Node* const object = NodeProperties::GetValueInput(node, 0);
+  Node* const effect = NodeProperties::GetEffectInput(node);
+  AbstractState const* state = node_states_.Get(effect);
+  if (state == nullptr) return NoChange();
+  ZoneHandleSet<Map> object_maps;
+  if (state->LookupMaps(object, &object_maps)) {
+    if (maps.contains(object_maps)) {
+      Node* value = jsgraph()->TrueConstant();
+      ReplaceWithValue(node, value, effect);
+      return Replace(value);
+    }
+    // TODO(turbofan): Compute the intersection.
+  }
+  return UpdateState(node, state);
+}
+
 Reduction LoadElimination::ReduceEnsureWritableFastElements(Node* node) {
   Node* const object = NodeProperties::GetValueInput(node, 0);
   Node* const elements = NodeProperties::GetValueInput(node, 1);

src/compiler/load-elimination.h

@@ -266,6 +266,7 @@ class V8_EXPORT_PRIVATE LoadElimination final
 
   Reduction ReduceArrayBufferWasNeutered(Node* node);
   Reduction ReduceCheckMaps(Node* node);
+  Reduction ReduceCompareMaps(Node* node);
   Reduction ReduceMapGuard(Node* node);
   Reduction ReduceEnsureWritableFastElements(Node* node);
   Reduction ReduceMaybeGrowFastElements(Node* node);

src/compiler/opcodes.h

@@ -339,6 +339,7 @@
   V(CheckHeapObject)                \
   V(CheckFloat64Hole)               \
   V(CheckNotTaggedHole)             \
+  V(CompareMaps)                    \
   V(ConvertTaggedHoleToUndefined)   \
   V(Allocate)                       \
   V(LoadField)                      \

src/compiler/simplified-lowering.cc

@@ -2770,6 +2770,9 @@ class RepresentationSelector {
         VisitInputs(node);
         return SetOutput(node, MachineRepresentation::kNone);
       }
+      case IrOpcode::kCompareMaps:
+        return VisitUnop(node, UseInfo::AnyTagged(),
+                         MachineRepresentation::kBit);
       case IrOpcode::kEnsureWritableFastElements:
         return VisitBinop(node, UseInfo::AnyTagged(),
                           MachineRepresentation::kTaggedPointer);

src/compiler/simplified-operator.cc

@@ -8,6 +8,8 @@
 #include "src/compiler/opcodes.h"
 #include "src/compiler/operator.h"
 #include "src/compiler/types.h"
+#include "src/handles-inl.h"
+#include "src/objects-inl.h"
 #include "src/objects/map.h"
 #include "src/objects/name.h"
 
@@ -213,6 +215,11 @@ CheckMapsParameters const& CheckMapsParametersOf(Operator const* op) {
   return OpParameter<CheckMapsParameters>(op);
 }
 
+ZoneHandleSet<Map> const& CompareMapsParametersOf(Operator const* op) {
+  DCHECK_EQ(IrOpcode::kCompareMaps, op->opcode());
+  return OpParameter<ZoneHandleSet<Map>>(op);
+}
+
 size_t hash_value(CheckTaggedInputMode mode) {
   return static_cast<size_t>(mode);
 }
@@ -860,6 +867,16 @@ const Operator* SimplifiedOperatorBuilder::CheckMaps(CheckMapsFlags flags,
       parameters);                                     // parameter
 }
 
+const Operator* SimplifiedOperatorBuilder::CompareMaps(
+    ZoneHandleSet<Map> maps) {
+  return new (zone()) Operator1<ZoneHandleSet<Map>>(  // --
+      IrOpcode::kCompareMaps,                         // opcode
+      Operator::kEliminatable,                        // flags
+      "CompareMaps",                                  // name
+      1, 1, 1, 1, 1, 0,                               // counts
+      maps);                                          // parameter
+}
+
 const Operator* SimplifiedOperatorBuilder::CheckFloat64Hole(
     CheckFloat64HoleMode mode) {
   switch (mode) {

src/compiler/simplified-operator.h

@@ -157,6 +157,10 @@ std::ostream& operator<<(std::ostream&, CheckMapsParameters const&);
 CheckMapsParameters const& CheckMapsParametersOf(Operator const*)
     WARN_UNUSED_RESULT;
 
+// Parameters for CompareMaps operator.
+ZoneHandleSet<Map> const& CompareMapsParametersOf(Operator const*)
+    WARN_UNUSED_RESULT;
+
 // A descriptor for growing elements backing stores.
 enum class GrowFastElementsFlag : uint8_t {
   kNone = 0u,
@@ -396,6 +400,7 @@ class V8_EXPORT_PRIVATE SimplifiedOperatorBuilder final
   const Operator* CheckBounds();
   const Operator* CheckMaps(CheckMapsFlags, ZoneHandleSet<Map>);
   const Operator* CheckMapValue();
+  const Operator* CompareMaps(ZoneHandleSet<Map>);
 
   const Operator* CheckHeapObject();
   const Operator* CheckInternalizedString();

src/compiler/typer.cc

@@ -1862,9 +1862,10 @@ Type* Typer::Visitor::TypeCheckMaps(Node* node) {
   UNREACHABLE();
 }
 
+Type* Typer::Visitor::TypeCompareMaps(Node* node) { return Type::Boolean(); }
+
 Type* Typer::Visitor::TypeCheckMapValue(Node* node) {
   UNREACHABLE();
-  return nullptr;
 }
 
 Type* Typer::Visitor::TypeCheckNumber(Node* node) {

src/compiler/verifier.cc

@@ -1190,6 +1190,10 @@ void Verifier::Visitor::Check(Node* node) {
       CheckValueInputIs(node, 0, Type::Any());
       CheckNotTyped(node);
       break;
+    case IrOpcode::kCompareMaps:
+      CheckValueInputIs(node, 0, Type::Any());
+      CheckTypeIs(node, Type::Boolean());
+      break;
     case IrOpcode::kCheckMapValue:
       CheckValueInputIs(node, 0, Type::Any());
       CheckValueInputIs(node, 1, Type::Any());