[turbofan] extend escape analysis to reduce CheckMaps

src/compiler/escape-analysis.cc

Index: src/compiler/escape-analysis.cc
diff --git a/src/compiler/escape-analysis.cc b/src/compiler/escape-analysis.cc
index 867afd62017003684eeedb7638fccf9b7518647a..2e5e8bf01200b6be5ec83e1fa1ed9172bb9021d3 100644
--- a/src/compiler/escape-analysis.cc
+++ b/src/compiler/escape-analysis.cc
@@ -807,6 +807,7 @@ bool EscapeStatusAnalysis::CheckUsesForEscape(Node* uses, Node* rep,
       case IrOpcode::kStateValues:
       case IrOpcode::kReferenceEqual:
       case IrOpcode::kFinishRegion:
+      case IrOpcode::kCheckMaps:
         if (IsEscaped(use) && SetEscaped(rep)) {
           TRACE(
               "Setting #%d (%s) to escaped because of use by escaping node "
@@ -1124,6 +1125,9 @@ bool EscapeAnalysis::Process(Node* node) {
     case IrOpcode::kLoadElement:
       ProcessLoadElement(node);
       break;
+    case IrOpcode::kCheckMaps:
+      ProcessCheckMaps(node);
+      break;
     case IrOpcode::kStart:
       ProcessStart(node);
       break;
@@ -1161,6 +1165,10 @@ void EscapeAnalysis::ProcessAllocationUsers(Node* node) {
       case IrOpcode::kFinishRegion:
       case IrOpcode::kObjectIsSmi:
         break;
+      case IrOpcode::kCheckMaps: {
+        CheckMapsParameters params = CheckMapsParametersOf(node->op());
+        if (params.flags() == CheckMapsFlag::kNone) break;
+      }  // Fallthrough.
       default:
         VirtualState* state = virtual_states_[node->id()];
         if (VirtualObject* obj =
@@ -1514,6 +1522,46 @@ void EscapeAnalysis::ProcessLoadField(Node* node) {
   }
 }
 
+void EscapeAnalysis::ProcessCheckMaps(Node* node) {
+  DCHECK_EQ(node->opcode(), IrOpcode::kCheckMaps);
+  ForwardVirtualState(node);
+  Node* checked = ResolveReplacement(NodeProperties::GetValueInput(node, 0));
+  if (FLAG_turbo_experimental) {
+    VirtualState* state = virtual_states_[node->id()];
+    if (VirtualObject* object = GetVirtualObject(state, checked)) {
+      if (!object->IsTracked()) {
+        if (status_analysis_->SetEscaped(node)) {
+          TRACE(
+              "Setting #%d (%s) to escaped because checked object #%i is not "
+              "tracked\n",
+              node->id(), node->op()->mnemonic(), object->id());
+        }
+        return;
+      }
+      CheckMapsParameters params = CheckMapsParametersOf(node->op());
+
+      Node* value = object->GetField(HeapObject::kMapOffset / kPointerSize);
+      if (value) {
+        value = ResolveReplacement(value);
+        // TODO(tebbi): We want to extend this beyond constant folding with a
+        // CheckMapsValue operator that takes the load-eliminated map value as
+        // input.
+        if (value->opcode() == IrOpcode::kHeapConstant &&
+            params.maps().contains(ZoneHandleSet<Map>(
+                Handle<Map>::cast(OpParameter<Handle<HeapObject>>(value))))) {
+          TRACE("CheckMaps #%i seems to be redundant (until now).\n",
+                node->id());
+          return;
+        }
+      }
+    }
+  }
+  if (status_analysis_->SetEscaped(node)) {
+    TRACE("Setting #%d (%s) to escaped (checking #%i)\n", node->id(),
+          node->op()->mnemonic(), checked->id());
+  }
+}
+
 void EscapeAnalysis::ProcessLoadElement(Node* node) {
   DCHECK_EQ(node->opcode(), IrOpcode::kLoadElement);
   ForwardVirtualState(node);