1//===- TableGenBackends.h - Declarations for LLVM TableGen Backends -------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains the declarations for all of the LLVM TableGen
10// backends. A "TableGen backend" is just a function. See below for a
11// precise description.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_UTILS_TABLEGEN_TABLEGENBACKENDS_H
16#define LLVM_UTILS_TABLEGEN_TABLEGENBACKENDS_H
17
18// A TableGen backend is a function that looks like
19//
20// EmitFoo(RecordKeeper &RK, raw_ostream &OS /*, anything else you need */ )
21//
22// What you do inside of that function is up to you, but it will usually
23// involve generating C++ code to the provided raw_ostream.
24//
25// The RecordKeeper is just a top-level container for an in-memory
26// representation of the data encoded in the TableGen file. What a TableGen
27// backend does is walk around that in-memory representation and generate
28// stuff based on the information it contains.
29//
30// The in-memory representation is a node-graph (think of it like JSON but
31// with a richer ontology of types), where the nodes are subclasses of
32// Record. The methods `getClass`, `getDef` are the basic interface to
33// access the node-graph. RecordKeeper also provides a handy method
34// `getAllDerivedDefinitions`. Consult "include/llvm/TableGen/Record.h" for
35// the exact interfaces provided by Record's and RecordKeeper.
36//
37// A common pattern for TableGen backends is for the EmitFoo function to
38// instantiate a class which holds some context for the generation process,
39// and then have most of the work happen in that class's methods. This
40// pattern partly has historical roots in the previous TableGen backend API
41// that involved a class and an invocation like `FooEmitter(RK).run(OS)`.
42//
43// Remember to wrap private things in an anonymous namespace. For most
44// backends, this means that the EmitFoo function is the only thing not in
45// the anonymous namespace.
46
47// FIXME: Reorganize TableGen so that build dependencies can be more
48// accurately expressed. Currently, touching any of the emitters (or
49// anything that they transitively depend on) causes everything dependent
50// on TableGen to be rebuilt (this includes all the targets!). Perhaps have
51// a standalone TableGen binary and have the backends be loadable modules
52// of some sort; then the dependency could be expressed as being on the
53// module, and all the modules would have a common dependency on the
54// TableGen binary with as few dependencies as possible on the rest of
55// LLVM.
56
57namespace llvm {
58
59class raw_ostream;
60class RecordKeeper;
61
62void EmitMapTable(const RecordKeeper &RK, raw_ostream &OS);
63
64// Defined in DecoderEmitter.cpp
65void EmitDecoder(const RecordKeeper &RK, raw_ostream &OS);
66
67} // namespace llvm
68
69#endif
70