[turbofan] Extend escape analysis to reduce certain CheckMaps.

Enable the experimental support in escape analysis to deal with
constant-foldable CheckMaps nodes and remove them from the effect
chain w/o blocking the scalar replacement of the object.

BUG=v8:4586,v8:5267
R=tebbi@chromium.org

Review-Url: https://codereview.chromium.org/2964473002
Cr-Commit-Position: refs/heads/master@{#46311}

src/compiler/escape-analysis.cc

@@ -1517,33 +1517,30 @@ 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;
+  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());
       }
-      CheckMapsParameters params = CheckMapsParametersOf(node->op());
+      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;
-        }
+    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;
       }
     }
   }