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//===- Main.cpp - Top-Level TableGen implementation -----------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// TableGen is a tool which can be used to build up a description of something,
// then invoke one or more "tablegen backends" to emit information about the
// description in some predefined format. In practice, this is used by the LLVM
// code generators to automate generation of a code generator through a
// high-level description of the target.
#include "llvm/TableGen/Main.h"
#include "TGParser.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/TableGen/Error.h"
#include "llvm/TableGen/Record.h"
#include <algorithm>
#include <cstdio>
#include <system_error>
using namespace llvm;
static cl::opt<std::string>
OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"),
static cl::opt<std::string>
cl::desc("Dependency filename"),
static cl::opt<std::string>
InputFilename(cl::Positional, cl::desc("<input file>"), cl::init("-"));
static cl::list<std::string>
IncludeDirs("I", cl::desc("Directory of include files"),
cl::value_desc("directory"), cl::Prefix);
static cl::list<std::string>
MacroNames("D", cl::desc("Name of the macro to be defined"),
cl::value_desc("macro name"), cl::Prefix);
static int reportError(const char *ProgName, Twine Msg) {
errs() << ProgName << ": " << Msg;
return 1;
/// Create a dependency file for `-d` option.
/// This functionality is really only for the benefit of the build system.
/// It is similar to GCC's `-M*` family of options.
static int createDependencyFile(const TGParser &Parser, const char *argv0) {
if (OutputFilename == "-")
return reportError(argv0, "the option -d must be used together with -o\n");
std::error_code EC;
ToolOutputFile DepOut(DependFilename, EC, sys::fs::F_Text);
if (EC)
return reportError(argv0, "error opening " + DependFilename + ":" +
EC.message() + "\n");
DepOut.os() << OutputFilename << ":";
for (const auto &Dep : Parser.getDependencies()) {
DepOut.os() << ' ' << Dep.first;
DepOut.os() << "\n";
return 0;
int llvm::TableGenMain(char *argv0, TableGenMainFn *MainFn) {
RecordKeeper Records;
// Parse the input file.
ErrorOr<std::unique_ptr<MemoryBuffer>> FileOrErr =
if (std::error_code EC = FileOrErr.getError())
return reportError(argv0, "Could not open input file '" + InputFilename +
"': " + EC.message() + "\n");
// Tell SrcMgr about this buffer, which is what TGParser will pick up.
SrcMgr.AddNewSourceBuffer(std::move(*FileOrErr), SMLoc());
// Record the location of the include directory so that the lexer can find
// it later.
TGParser Parser(SrcMgr, MacroNames, Records);
if (Parser.ParseFile())
return 1;
// Write output to memory.
std::string OutString;
raw_string_ostream Out(OutString);
if (MainFn(Out, Records))
return 1;
// Always write the depfile, even if the main output hasn't changed.
// If it's missing, Ninja considers the output dirty. If this was below
// the early exit below and someone deleted the .inc.d file but not the .inc
// file, tablegen would never write the depfile.
if (!DependFilename.empty()) {
if (int Ret = createDependencyFile(Parser, argv0))
return Ret;
// Only updates the real output file if there are any differences.
// This prevents recompilation of all the files depending on it if there
// aren't any.
if (auto ExistingOrErr = MemoryBuffer::getFile(OutputFilename))
if (std::move(ExistingOrErr.get())->getBuffer() == Out.str())
return 0;
std::error_code EC;
ToolOutputFile OutFile(OutputFilename, EC, sys::fs::F_Text);
if (EC)
return reportError(argv0, "error opening " + OutputFilename + ":" +
EC.message() + "\n");
OutFile.os() << Out.str();
if (ErrorsPrinted > 0)
return reportError(argv0, Twine(ErrorsPrinted) + " errors.\n");
// Declare success.
return 0;