llvm-project/llvm/utils/TableGen/llvm-min-tblgen.cpp

//===- llvm-min-tblgen.cpp ------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains the main function for LLVM's TableGen.
//
//===----------------------------------------------------------------------===//

#include "Basic/TableGen.h"

/// Command line parameters are shared between llvm-tblgen and llvm-min-tblgen.
/// The indirection to tblgen_main exists to ensure that the static variables
/// for the llvm::cl:: mechanism are linked into both executables.
int main(int argc, char **argv) { return tblgen_main(argc, argv); }
[llvm-(min-)tblgen] Avoid redundant source compilation (#114494) All the sources of `llvm-min-tblgen` are also used for `llvm-tblgen`, with identical compilation flags. Reuse the object files of `llvm-min-tblgen` for `llvm-tblgen` by applying the usual source structure of an executable: One file per executable which named after the executable name containing the (in this case trivial) main function, which just calls the tblgen_main in TableGen.cpp. This should also clear up any confusion (including mine) of where each executable's main function is. While this slightly reduces build time, the main motivation is ccache. Using the hard_link option, building the object files for `llvm-tblgen` will result in a hard link to the same object file already used for `llvm-min-tblgen`. To signal the build system that the file is new, ccache will update the file's time stamp. Unfortunately, time stamps are shared between all hard-linked files s.t. this will indirectly also update the time stamps for the object files used for `llvm-tblgen`. At the next run, Ninja will recognize this time stamp discrepancy to the expected stamp recorded in `.ninja_log` and rebuild those object files for `llvm-min-tblgen`, which again will also update the stamp for the `llvm-tblgen`... . This is especially annoying for tablegen because it means Ninja will re-run all tablegenning in every build. I am using the hard_link option because it reduces the cost of having multiple build-trees of the LLVM sources and reduces the wear to the SSD they are stored on. 2025-01-03 00:34:24 +01:00			`//===- llvm-min-tblgen.cpp ------------------------------------------------===//`
			`//`
			`// 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`
			`//`
			`//===----------------------------------------------------------------------===//`
			`//`
			`// This file contains the main function for LLVM's TableGen.`
			`//`
			`//===----------------------------------------------------------------------===//`

			`#include "Basic/TableGen.h"`

			`/// Command line parameters are shared between llvm-tblgen and llvm-min-tblgen.`
			`/// The indirection to tblgen_main exists to ensure that the static variables`
			`/// for the llvm::cl:: mechanism are linked into both executables.`
			`int main(int argc, char **argv) { return tblgen_main(argc, argv); }`