| commit | c4e9714e7d858449d1db7adbb2b59f82eddf89e4 | [log] [tgz] |
|---|---|---|
| author | Peter Klausler <pklausler@nvidia.com> | Mon Jul 25 17:27:15 2022 -0700 |
| committer | Copybara-Service <copybara-worker@google.com> | Sun Aug 07 12:56:48 2022 -0700 |
| tree | 487ca08bf5d71c70cd83a81a0e4fd283d5df0e88 | |
| parent | b3244026810be0d5c77b1224916091264c581158 [diff] |
[flang][runtime] Catch & report attempts at recursive I/O When an I/O statement contains a function call that attempts to perform I/O on the same unit, detect the recursive I/O and terminate with a useful message rather than deadlocking in the threading library. Differential Revision: https://reviews.llvm.org/D131097 GitOrigin-RevId: 921316af6e6b34d57d5e8f26f86f2bce8d034c7f
Flang is a ground-up implementation of a Fortran front end written in modern C++. It started off as the f18 project (https://github.com/flang-compiler/f18) with an aim to replace the previous flang project (https://github.com/flang-compiler/flang) and address its various deficiencies. F18 was subsequently accepted into the LLVM project and rechristened as Flang.
Read more about flang in the docs directory. Start with the compiler overview.
To better understand Fortran as a language and the specific grammar accepted by flang, read Fortran For C Programmers and flang's specifications of the Fortran grammar and the OpenMP grammar.
Treatment of language extensions is covered in this document.
To understand the compilers handling of intrinsics, see the discussion of intrinsics.
To understand how a flang program communicates with libraries at runtime, see the discussion of runtime descriptors.
If you're interested in contributing to the compiler, read the style guide and also review how flang uses modern C++ features.
If you are interested in writing new documentation, follow LLVM's Markdown style guide.
There are two ways to build flang. The first method is to build it at the same time that you build all of the projects on which it depends. This is called building in tree. The second method is to first do an in tree build to create all of the projects on which flang depends, and then only build the flang code itself. This is called building standalone. Building standalone has the advantage of being smaller and faster. Once you create the base build and base install areas, you can create multiple standalone builds using them.
Note that instructions for building LLVM can be found at https://llvm.org/docs/GettingStarted.html.
Building flang in tree means building flang along with all of the projects on which it depends. These projects include mlir, clang, flang, and compiler-rt. Note that compiler-rt is only needed to access libraries that support 16 bit floating point numbers. It's not needed to run the automated tests.
Here's a complete set of commands to clone all of the necessary source and do the build.
First clone the source:
git clone https://github.com/llvm/llvm-project.git my-project
Once the clone is complete, execute the following commands:
cd my-project rm -rf build mkdir -p build cd build cmake \ -G Ninja \ ../llvm \ -DCMAKE_BUILD_TYPE=Release \ -DFLANG_ENABLE_WERROR=On \ -DLLVM_ENABLE_ASSERTIONS=ON \ -DLLVM_TARGETS_TO_BUILD=host \ -DCMAKE_INSTALL_PREFIX=$INSTALLDIR -DLLVM_LIT_ARGS=-v \ -DLLVM_ENABLE_PROJECTS="clang;mlir;flang" \ -DLLVM_ENABLE_RUNTIMES="compiler-rt" ninja
To run the flang tests on this build, execute the command in the “build” directory:
ninja check-flang
Note that these instructions specify flang as one of the projects to build in the in tree build. This is not strictly necessary for subsequent standalone builds, but doing so lets you run the flang tests to verify that the source code is in good shape.
To do the standalone build, start by building flang in tree as described above. This build is base build for subsequent standalone builds. Start each standalone build the same way by cloning the source for llvm-project:
git clone https://github.com/llvm/llvm-project.git standalone
Once the clone is complete, execute the following commands:
cd standalone base=<directory that contains the in tree build> cd flang rm -rf build mkdir build cd build cmake \ -G Ninja \ -DCMAKE_BUILD_TYPE=Release \ -DFLANG_ENABLE_WERROR=On \ -DLLVM_TARGETS_TO_BUILD=host \ -DLLVM_ENABLE_ASSERTIONS=On \ -DLLVM_BUILD_MAIN_SRC_DIR=$base/build/lib/cmake/llvm \ -DLLVM_LIT_ARGS=-v \ -DLLVM_DIR=$base/build/lib/cmake/llvm \ -DCLANG_DIR=$base/build/lib/cmake/clang \ -DMLIR_DIR=$base/build/lib/cmake/mlir \ .. ninja
To run the flang tests on this build, execute the command in the “flang/build” directory:
ninja check-flang
Flang is written in C++17.
The code has been compiled and tested with GCC versions from 7.2.0 to 9.3.0.
The code has been compiled and tested with clang version 7.0, 8.0, 9.0 and 10.0 using either GNU‘s libstdc++ or LLVM’s libc++.
The code has been compiled on AArch64, x86_64 and ppc64le servers with CentOS7, Ubuntu18.04, Rhel, MacOs, Mojave, XCode and Apple Clang version 10.0.1.
By default, cmake will search for g++ on your PATH. The g++ version must be one of the supported versions in order to build flang.
Or, cmake will use the variable CXX to find the C++ compiler. CXX should include the full path to the compiler or a name that will be found on your PATH, e.g. g++-8.3, assuming g++-8.3 is on your PATH.
export CXX=g++-8.3
or
CXX=/opt/gcc-8.3/bin/g++-8.3 cmake ...
To build flang with clang, cmake needs to know how to find clang++ and the GCC library and tools that were used to build clang++.
CXX should include the full path to clang++ or clang++ should be found on your PATH.
export CXX=clang++
To specify a custom install location, add -DCMAKE_INSTALL_PREFIX=<INSTALL_PREFIX> to the cmake command where <INSTALL_PREFIX> is the path where flang should be installed.
To create a debug build, add -DCMAKE_BUILD_TYPE=Debug to the cmake command. Debug builds execute slowly.
To create a release build, add -DCMAKE_BUILD_TYPE=Release to the cmake command. Release builds execute quickly.
Flang supports 2 different categories of tests
To run all tests:
cd ~/flang/build cmake -DLLVM_DIR=$LLVM -DMLIR_DIR=$MLIR ~/flang/src ninja check-all
To run individual regression tests llvm-lit needs to know the lit configuration for flang. The parameters in charge of this are: flang_site_config and flang_config. And they can be set as shown below:
<path-to-llvm-lit>/llvm-lit \ --param flang_site_config=<path-to-flang-build>/test-lit/lit.site.cfg.py \ --param flang_config=<path-to-flang-build>/test-lit/lit.cfg.py \ <path-to-fortran-test>
Unit tests:
If flang was built with -DFLANG_INCLUDE_TESTS=On (ON by default), it is possible to generate unittests. Note: Unit-tests will be skipped for LLVM install for an standalone build as it does not include googletest related headers and libraries.
There are various ways to run unit-tests.
1. ninja check-flang-unit 2. ninja check-all or ninja check-flang 3. <path-to-llvm-lit>/llvm-lit \ test/Unit 4. Invoking tests from <standalone flang build>/unittests/<respective unit test folder>
If flang was built with -DFLANG_INCLUDE_TESTS=On (On by default), it is possible to generate unittests.
To run all of the flang unit tests use the check-flang-unit target:
ninja check-flang-unit
To run all of the flang regression tests use the check-flang target:
ninja check-flang
If flang was built with -DLINK_WITH_FIR=On (On by default), it is possible to generate FIR language documentation by running ninja flang-doc. This will create docs/Dialect/FIRLangRef.md in flang build directory.
To generate doxygen-style documentation from source code
-DLLVM_ENABLE_DOXYGEN=ON -DFLANG_INCLUDE_DOCS=ON to the cmake command.cd ~/llvm-project/build cmake -DLLVM_ENABLE_DOXYGEN=ON -DFLANG_INCLUDE_DOCS=ON ../llvm ninja doxygen-flang
It will generate html in
<build-dir>/tools/flang/docs/doxygen/html # for flang docs
Flang documentation should preferably be written in markdown(.md) syntax (they can be in reStructuredText(.rst) format as well but markdown is recommended in first place), it is mostly meant to be processed by the Sphinx documentation generation system to create HTML pages which would be hosted on the webpage of flang and updated periodically.
If you would like to generate and view the HTML locally:
-DLLVM_ENABLE_SPHINX=ON -DSPHINX_WARNINGS_AS_ERRORS=OFF to the cmake command.cd ~/llvm-project/build cmake -DLLVM_ENABLE_SPHINX=ON -DSPHINX_WARNINGS_AS_ERRORS=OFF ../llvm ninja docs-flang-html
It will generate html in
$BROWSER <build-dir>/tools/flang/docs/html/