[turbofan] Also update the BranchHint when merging a BooleanNot.

src/compiler/common-operator.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_COMMON_OPERATOR_H_
 #define V8_COMPILER_COMMON_OPERATOR_H_
 
 #include "src/compiler/frame-states.h"
 #include "src/compiler/machine-type.h"
 #include "src/unique.h"
 
 namespace v8 {
 namespace internal {
 
 // Forward declarations.
 class ExternalReference;
 
 
 namespace compiler {
 
 // Forward declarations.
 class CallDescriptor;
 struct CommonOperatorGlobalCache;
 class Operator;
 
 
 // Prediction hint for branches.
 enum class BranchHint : uint8_t { kNone, kTrue, kFalse };
 
+inline BranchHint NegateBranchHint(BranchHint hint) {
+  switch (hint) {
+    case BranchHint::kNone:
+      return hint;
+    case BranchHint::kTrue:
+      return BranchHint::kFalse;
+    case BranchHint::kFalse:
+      return BranchHint::kTrue;
+  }
+  UNREACHABLE();
+  return hint;
+}
+
 inline size_t hash_value(BranchHint hint) { return static_cast<size_t>(hint); }
 
 std::ostream& operator<<(std::ostream&, BranchHint);
 
 BranchHint BranchHintOf(const Operator* const);
 
 
 // Prediction whether throw-site is surrounded by any local catch-scope.
 enum class IfExceptionHint { kLocallyUncaught, kLocallyCaught };
 
@@ skipping 119 matching lines @@
   Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(CommonOperatorBuilder);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_COMMON_OPERATOR_H_