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#include <string>
19
20// A TableGen backend is a function that looks like
21//
22// EmitFoo(RecordKeeper &RK, raw_ostream &OS /*, anything else you need */ )
23//
24// What you do inside of that function is up to you, but it will usually
25// involve generating C++ code to the provided raw_ostream.
26//
27// The RecordKeeper is just a top-level container for an in-memory
28// representation of the data encoded in the TableGen file. What a TableGen
29// backend does is walk around that in-memory representation and generate
30// stuff based on the information it contains.
31//
32// The in-memory representation is a node-graph (think of it like JSON but
33// with a richer ontology of types), where the nodes are subclasses of
34// Record. The methods `getClass`, `getDef` are the basic interface to
35// access the node-graph. RecordKeeper also provides a handy method
36// `getAllDerivedDefinitions`. Consult "include/llvm/TableGen/Record.h" for
37// the exact interfaces provided by Record's and RecordKeeper.
38//
39// A common pattern for TableGen backends is for the EmitFoo function to
40// instantiate a class which holds some context for the generation process,
41// and then have most of the work happen in that class's methods. This
42// pattern partly has historical roots in the previous TableGen backend API
43// that involved a class and an invocation like `FooEmitter(RK).run(OS)`.
44//
45// Remember to wrap private things in an anonymous namespace. For most
46// backends, this means that the EmitFoo function is the only thing not in
47// the anonymous namespace.
48
49// FIXME: Reorganize TableGen so that build dependencies can be more
50// accurately expressed. Currently, touching any of the emitters (or
51// anything that they transitively depend on) causes everything dependent
52// on TableGen to be rebuilt (this includes all the targets!). Perhaps have
53// a standalone TableGen binary and have the backends be loadable modules
54// of some sort; then the dependency could be expressed as being on the
55// module, and all the modules would have a common dependency on the
56// TableGen binary with as few dependencies as possible on the rest of
57// LLVM.
58
59namespace llvm {
60
61class raw_ostream;
62class RecordKeeper;
63
64void EmitMapTable(const RecordKeeper &RK, raw_ostream &OS);
65
66// Defined in DecoderEmitter.cpp
67void EmitDecoder(const RecordKeeper &RK, raw_ostream &OS,
68 StringRef PredicateNamespace);
69
70} // namespace llvm
71
72#endif
73