[turbofan] Add Symbol feedback to Equal/StrictEqual.

src/compiler/effect-control-linearizer.cc

Index: src/compiler/effect-control-linearizer.cc
diff --git a/src/compiler/effect-control-linearizer.cc b/src/compiler/effect-control-linearizer.cc
index 6a75e8cff234aa519a7f413e4befa7f1af09e597..546a45e4f8ea8f171692421f69ade61dcfdfb312 100644
--- a/src/compiler/effect-control-linearizer.cc
+++ b/src/compiler/effect-control-linearizer.cc
@@ -641,6 +641,9 @@ bool EffectControlLinearizer::TryWireInStateEffect(Node* node,
     case IrOpcode::kCheckReceiver:
       result = LowerCheckReceiver(node, frame_state);
       break;
+    case IrOpcode::kCheckSymbol:
+      result = LowerCheckSymbol(node, frame_state);
+      break;
     case IrOpcode::kCheckString:
       result = LowerCheckString(node, frame_state);
       break;
@@ -1300,6 +1303,17 @@ Node* EffectControlLinearizer::LowerCheckReceiver(Node* node,
   return value;
 }
 
+Node* EffectControlLinearizer::LowerCheckSymbol(Node* node, Node* frame_state) {
+  Node* value = node->InputAt(0);
+
+  Node* value_map = __ LoadField(AccessBuilder::ForMap(), value);
+
+  Node* check =
+      __ WordEqual(value_map, __ HeapConstant(factory()->symbol_map()));
+  __ DeoptimizeUnless(DeoptimizeReason::kNotASymbol, check, frame_state);
+  return value;
+}
+
 Node* EffectControlLinearizer::LowerCheckString(Node* node, Node* frame_state) {
   Node* value = node->InputAt(0);