[turbofan] Introduce CheckUnless.

src/compiler/simplified-operator.cc

Index: src/compiler/simplified-operator.cc
diff --git a/src/compiler/simplified-operator.cc b/src/compiler/simplified-operator.cc
index 355f8748f5e1ee15cfc590eacc6d6e4beeb843d3..a339b21843faea3de319395f066d00b15b054b16 100644
--- a/src/compiler/simplified-operator.cc
+++ b/src/compiler/simplified-operator.cc
@@ -366,6 +366,13 @@ struct SimplifiedOperatorGlobalCache final {
   };
   CheckIfOperator kCheckIf;
 
+  struct CheckUnlessOperator final : public Operator {
+    CheckUnlessOperator()
+        : Operator(IrOpcode::kCheckUnless, Operator::kPure, "CheckUnless", 1, 1,
+                   1, 0, 1, 0) {}
+  };
+  CheckUnlessOperator kCheckUnless;
+
   template <PretenureFlag kPretenure>
   struct AllocateOperator final : public Operator1<PretenureFlag> {
     AllocateOperator()
@@ -442,6 +449,10 @@ const Operator* SimplifiedOperatorBuilder::CheckIf() {
   return &cache_.kCheckIf;
 }
 
+const Operator* SimplifiedOperatorBuilder::CheckUnless() {
+  return &cache_.kCheckUnless;
+}
+
 const Operator* SimplifiedOperatorBuilder::ReferenceEqual(Type* type) {
   return new (zone()) Operator(IrOpcode::kReferenceEqual,
                                Operator::kCommutative | Operator::kPure,