Move TableGen's parser and entry point into a library

This is the first step towards splitting LLVM and Clang's tblgen executables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140951 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/TableGen/TableGenAction.h

@@ -0,0 +1,34 @@
+//===- llvm/TableGen/TableGenAction.h - defines TableGenAction --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the TableGenAction base class to be derived from by
+// tblgen tools.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TABLEGEN_TABLEGENACTION_H
+#define LLVM_TABLEGEN_TABLEGENACTION_H
+
+namespace llvm {
+
+class raw_ostream;
+class RecordKeeper;
+
+class TableGenAction {
+public:
+  virtual ~TableGenAction() {}
+
+  /// Perform the action using Records, and write output to OS.
+  /// @returns true on error, false otherwise
+  virtual bool operator()(raw_ostream &OS, RecordKeeper &Records) = 0;
+};
+
+}
+
+#endif