[turbofan] Introduce CallDescriptorOf helper for safety.

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/assembler.h"
 #include "src/compiler/frame-states.h"
 #include "src/machine-type.h"
@@ skipping 70 matching lines @@
 
 bool operator==(SelectParameters const&, SelectParameters const&);
 bool operator!=(SelectParameters const&, SelectParameters const&);
 
 size_t hash_value(SelectParameters const& p);
 
 std::ostream& operator<<(std::ostream&, SelectParameters const& p);
 
 SelectParameters const& SelectParametersOf(const Operator* const);
 
+CallDescriptor const* CallDescriptorOf(const Operator* const);
 
 size_t ProjectionIndexOf(const Operator* const);
 
 MachineRepresentation PhiRepresentationOf(const Operator* const);
 
 
 // The {IrOpcode::kParameter} opcode represents an incoming parameter to the
 // function. This class bundles the index and a debug name for such operators.
 class ParameterInfo final {
  public:
@@ skipping 112 matching lines @@
   Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(CommonOperatorBuilder);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_COMMON_OPERATOR_H_