Main.cpp

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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 https://llvm.org/LICENSE.txt 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 "TGLexer.h"
#include "TGParser.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorOr.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SMLoc.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Support/VirtualFileSystem.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/TableGen/Error.h"
#include "llvm/TableGen/Record.h"
#include "llvm/TableGen/TGTimer.h"
#include "llvm/TableGen/TableGenBackend.h"
#include <memory>
#include <string>
#include <system_error>
#include <utility>
using namespace llvm;
 
static cl::opt<std::string>
OutputFilename("o", cl::desc("Output filename"), cl::value_desc("filename"),
               cl::init("-"));
 
static cl::opt<std::string>
DependFilename("d",
               cl::desc("Dependency filename"),
               cl::value_desc("filename"),
               cl::init(""));
 
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 cl::opt<bool>
WriteIfChanged("write-if-changed", cl::desc("Only write output if it changed"));
 
static cl::opt<bool>
TimePhases("time-phases", cl::desc("Time phases of parser and backend"));
 
cl::opt<bool> llvm::EmitLongStrLiterals(
    "long-string-literals",
    cl::desc("when emitting large string tables, prefer string literals over "
             "comma-separated char literals. This can be a readability and "
             "compile-time performance win, but upsets some compilers"),
    cl::Hidden, cl::init(true));
 
static cl::opt<bool> NoWarnOnUnusedTemplateArgs(
    "no-warn-on-unused-template-args",
    cl::desc("Disable unused template argument warnings."));
 
static cl::opt<bool> Preprocess("E", cl::desc("Write preprocessed output"));
 
static int reportError(const char *ProgName, Twine Msg) {
  errs() << ProgName << ": " << Msg;
  errs().flush();
  return 1;
}
 
namespace {
/// Encapsulate file, line and column numbers from SourceMgr.
struct SMCoords {
  unsigned Buf = 0;
  unsigned Line = 0;
  unsigned Col = 0;
  SMCoords() = default;
  SMCoords(const SourceMgr &Mgr, SMLoc Loc) {
    Buf = Mgr.FindBufferContainingLoc(Loc);
    // TODO: Find a faster way to do this. For example we don't need the column
    // number for every token, only the first token on each output line.
    std::tie(Line, Col) = Mgr.getLineAndColumn(Loc, Buf);
  }
};
} // end anonymous namespace
 
/// Create preprocessed output for `-E` option.
static int preprocessInput(TGLexer &Lex, raw_ostream &OS) {
  SMCoords Last;
  while (true) {
    Lex.Lex();
    if (Lex.getCode() == tgtok::Eof || Lex.getCode() == tgtok::Error)
      break;
    SMCoords This(SrcMgr, Lex.getLoc());
    if (This.Buf == Last.Buf && This.Line == Last.Line) {
      // Add a single space between tokens on the same line. This is overkill in
      // many cases but at least it will parse correctly.
      OS << ' ';
    } else {
      // Always start a new line when including a new file or popping back out
      // to the previous file. This is just a heuristic to make the output look
      // reasonably pretty.
      if (Last.Buf)
        OS << '\n';
      // Indent the first token on a line to its original indentation, to make
      // the output look pretty.
      OS.indent(This.Col - 1);
    }
 
    const char *Start = Lex.getLoc().getPointer();
    const char *End = Lex.getLocRange().End.getPointer();
    StringRef Text(Start, End - Start);
    OS << Text;
 
    Last = This;
    // A code block is the only kind of token that can span multiple lines.
    // Record the line it ends on, so that a following token on that line stays
    // on the same output line. Count '\n' characters to match how SourceMgr
    // counts lines.
    if (Lex.getCode() == tgtok::CodeFragment)
      Last.Line += Text.count('\n');
  }
  if (Last.Buf != 0)
    OS << '\n';
  return Lex.getCode() == tgtok::Error;
}
 
/// 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 TGLexer::DependenciesSetTy &Dependencies,
                                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::OF_Text);
  if (EC)
    return reportError(argv0, "error opening " + DependFilename + ":" +
                                  EC.message() + "\n");
  DepOut.os() << OutputFilename << ":";
 
  // Emit the primary input file as a dependency. This matches C compilers like
  // Clang and GCC. Without it, a .td file with no `include` directives would
  // produce a depfile listing zero dependencies. CMake's
  // `cmake_transform_depfile` then collapses that to a 0-byte file, which Ninja
  // treats as a missing depfile and re-runs the rule on every incremental
  // build.
  if (InputFilename != "-")
    DepOut.os() << ' ' << InputFilename;
 
  for (const auto &Dep : Dependencies) {
    DepOut.os() << ' ' << Dep;
  }
  DepOut.os() << "\n";
  DepOut.keep();
  return 0;
}
 
static int WriteOutput(const char *argv0, StringRef Filename,
                       StringRef Content) {
  if (WriteIfChanged) {
    // 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(Filename, /*IsText=*/true))
      if (std::move(ExistingOrErr.get())->getBuffer() == Content)
        return 0;
  }
  std::error_code EC;
  // On z/OS, text files default to IBM-1047, but generated files are UTF-8.
  // OF_ForceUTF8 has no effect on other platforms.
  ToolOutputFile OutFile(Filename, EC,
                         sys::fs::OF_Text | sys::fs::OF_ForceUTF8);
  if (EC)
    return reportError(argv0, "error opening " + Filename + ": " +
                                  EC.message() + "\n");
  OutFile.os() << Content;
  if (ErrorsPrinted == 0)
    OutFile.keep();
 
  return 0;
}
 
int llvm::TableGenMain(const char *argv0, MultiFileTableGenMainFn MainFn) {
  ErrorOr<std::unique_ptr<MemoryBuffer>> FileOrErr =
      MemoryBuffer::getFileOrSTDIN(InputFilename, /*IsText=*/true);
  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.
  SrcMgr.setIncludeDirs(IncludeDirs);
  SrcMgr.setVirtualFileSystem(vfs::getRealFileSystem());
 
  if (Preprocess) {
    TGLexer Lex(SrcMgr, MacroNames);
    std::string OutString;
    raw_string_ostream Out(OutString);
    if (int Ret = preprocessInput(Lex, Out))
      return Ret;
    // Return early if the lexer printed errors but still reached EOF (e.g., a
    // NUL character in the source).
    if (ErrorsPrinted > 0)
      return reportError(argv0, Twine(ErrorsPrinted) + " errors.\n");
    if (!DependFilename.empty()) {
      if (int Ret = createDependencyFile(Lex.getDependencies(), argv0))
        return Ret;
    }
    return WriteOutput(argv0, OutputFilename, OutString);
  }
 
  RecordKeeper Records;
  Records.saveInputFilename(InputFilename);
 
  TGTimer &Timer = Records.getTimer();
  if (TimePhases)
    Timer.startPhaseTiming();
 
  // Parse the input file.
 
  Timer.startTimer("Parse, build records");
 
  TGParser Parser(SrcMgr, MacroNames, Records, NoWarnOnUnusedTemplateArgs);
 
  if (Parser.ParseFile())
    return 1;
  Timer.stopTimer();
 
  // Return early if any other errors were generated during parsing
  // (e.g., assert failures).
  if (ErrorsPrinted > 0)
    return reportError(argv0, Twine(ErrorsPrinted) + " errors.\n");
 
  // Write output to memory.
  Timer.startBackendTimer("Backend overall");
  TableGenOutputFiles OutFiles;
  unsigned status = 0;
  // ApplyCallback will return true if it did not apply any callback. In that
  // case, attempt to apply the MainFn.
  StringRef FilenamePrefix(sys::path::stem(OutputFilename));
  if (TableGen::Emitter::ApplyCallback(Records, OutFiles, FilenamePrefix))
    status = MainFn ? MainFn(OutFiles, Records) : 1;
  Timer.stopBackendTimer();
  if (status)
    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.getDependencies(), argv0))
      return Ret;
  }
 
  Timer.startTimer("Write output");
  if (int Ret = WriteOutput(argv0, OutputFilename, OutFiles.MainFile))
    return Ret;
  for (auto [Suffix, Content] : OutFiles.AdditionalFiles) {
    SmallString<128> Filename(OutputFilename);
    // TODO: Format using the split-file convention when writing to stdout?
    if (Filename != "-") {
      sys::path::replace_extension(Filename, "");
      Filename.append(Suffix);
    }
    if (int Ret = WriteOutput(argv0, Filename, Content))
      return Ret;
  }
 
  Timer.stopTimer();
  Timer.stopPhaseTiming();
 
  if (ErrorsPrinted > 0)
    return reportError(argv0, Twine(ErrorsPrinted) + " errors.\n");
  return 0;
}
 
int llvm::TableGenMain(const char *argv0, TableGenMainFn MainFn) {
  return TableGenMain(argv0, [&MainFn](TableGenOutputFiles &OutFiles,
                                       const RecordKeeper &Records) {
    std::string S;
    raw_string_ostream OS(S);
    int Res = MainFn(OS, Records);
    OutFiles = {std::move(S), {}};
    return Res;
  });
}