[machine-operator-reducer] fix float truncation

src/compiler/opcodes.h

 // Copyright 2013 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_OPCODES_H_
 #define V8_COMPILER_OPCODES_H_
 
 #include <iosfwd>
 
 // Opcodes for control operators.
@@ skipping 361 matching lines @@
   static bool IsIfProjectionOpcode(Value value) {
     return kIfTrue <= value && value <= kIfDefault;
   }
 
   // Returns true if opcode for comparison operator.
   static bool IsComparisonOpcode(Value value) {
     return (kJSEqual <= value && value <= kJSGreaterThanOrEqual) ||
            (kNumberEqual <= value && value <= kStringLessThanOrEqual) ||
            (kWord32Equal <= value && value <= kFloat64LessThanOrEqual);
   }
+
+  static bool Is64(Value value);
 };
 
 std::ostream& operator<<(std::ostream&, IrOpcode::Value);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPCODES_H_