[refactor] Separate generated builtins and C++ builtins into separate files

src/builtins/builtins-utils-gen.h

+// Copyright 2017 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_BUILTINS_BUILTINS_UTILS_GEN_H_
+#define V8_BUILTINS_BUILTINS_UTILS_GEN_H_
+
+namespace v8 {
+namespace internal {
+
+namespace compiler {
+class CodeAssemblerState;
+}  // namespace compiler
+
+// ----------------------------------------------------------------------------
+// Support macro for defining builtins with Turbofan.
+// ----------------------------------------------------------------------------
+//
+// A builtin function is defined by writing:
+//
+//   TF_BUILTIN(name, code_assember_base_class) {
+//     ...
+//   }
+//
+// In the body of the builtin function the arguments can be accessed
+// as "Parameter(n)".
+#define TF_BUILTIN(Name, AssemblerBase)                                 \
+  class Name##Assembler : public AssemblerBase {                        \
+   public:                                                              \
+    explicit Name##Assembler(compiler::CodeAssemblerState* state)       \
+        : AssemblerBase(state) {}                                       \
+    void Generate##Name##Impl();                                        \
+  };                                                                    \
+  void Builtins::Generate_##Name(compiler::CodeAssemblerState* state) { \
+    Name##Assembler assembler(state);                                   \
+    assembler.Generate##Name##Impl();                                   \
+  }                                                                     \
+  void Name##Assembler::Generate##Name##Impl()
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_BUILTINS_BUILTINS_UTILS_GEN_H_