Flang is a Fortran compiler targeting LLVM.
Please join us for a Flang meetup at SC 17 in Denver. NVIDIA has reserved a room for the meetup on Wednesday, November 15 at 6:30 PM at the Curtis Hotel in the Hopscotch room (3rd floor). The Curtis is a block from the convention center. Light refreshments will be provided! (And maybe snacks, too.) We are looking forward to seeing you all face-to-face.
We have mailing lists for announcements and developers. Here's the link with the sign-up information:
http://lists.flang-compiler.org/mailman/listinfo
We have a flang-compiler channel on Slack. Slack is invitation only but anyone can join. Here's the link:
https://join.slack.com/t/flang-compiler/shared_invite/MjExOTEyMzQ3MjIxLTE0OTk4NzQyNzUtODQzZWEyMjkwYw
We build Flang on Intel x86-64 and OpenPOWER hardware running either Ubuntu or Red Hat.
Building LLVM requires fairly modern compiler toolchain and CMake, check Getting started with LLVM and Building LLVM with CMake for the full list.
- LLVM
- openmp-llvm
- modified clang
The latest supported LLVM version is 4.0. Flang also supports LLVM version 5.0 and 3.9. To use 5.0, substitute 50 for 40 in the build instructions. To use 3.9, substitute 39 for 40 in the build instructions.
The command-line examples provided below will install everything into the default system location.
To specify a custom install location, add -DCMAKE_INSTALL_PREFIX=<INSTALL_PREFIX> to each of the CMake commands given below.
When using a custom install location, you must make sure that the bin directory is on your PATH when building and running flang.
Flang is developed outside of the llvm source tree.
-
Get LLVM 4.0, build and install it according to instructions
cd where/you/want/to/build git clone https://github.com/llvm-mirror/llvm.git cd llvm git checkout release_40 mkdir build && cd build cmake .. make sudo make install -
Get the modified clang for flang, build and install it (4.0)
cd where/you/want/to/build git clone https://github.com/flang-compiler/clang.git cd clang git checkout flang_release_40 mkdir build && cd build cmake .. make sudo make installIf you use
CMAKE_INSTALL_PREFIXin Step 1 and<INSTALL_PREFIX>/binis not in your path, you need to add-DLLVM_CONFIG=<INSTALL_PREFIX>/bin/llvm-configwhen invoking CMake, otherwise you will encounter an error related toLLVMConfig.cmakenot being found. -
Build and install openmp-llvm (4.0)
cd where/you/want/to/build git clone https://github.com/llvm-mirror/openmp.git cd openmp/runtime git checkout release_40 mkdir build && cd build cmake .. make sudo make install -
Build and install the flang components
cd where/you/want/to/build git clone https://github.com/flang-compiler/flang.git cd flang mkdir build && cd build cmake -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER=clang -DCMAKE_Fortran_COMPILER=flang .. make sudo make installIf you use
CMAKE_INSTALL_PREFIXin Step 1 and<INSTALL_PREFIX>/binis not in your path, you need to add-DLLVM_CONFIG=<INSTALL_PREFIX>/bin/llvm-configand set the explicit paths for the compilers (i.e.-DCMAKE_CXX_COMPILER=<INSTALL_PREFIX>/bin/clang++ -DCMAKE_C_COMPILER=<INSTALL_PREFIX>/bin/clang -DCMAKE_Fortran_COMPILER=<INSTALL_PREFIX>/bin/flang) when invoking CMake, otherwise you will encounter errors.
Spack is a flexible package manager for HPC system and can be used to build flang and its dependencies.
-
Get Spack
git clone https://github.com/llnl/spack.gitOn bash:
source spack/share/spack/setup-env.shor tcsh:
source spack/share/spack/setup-env.csh -
Build Flang and its depencencies:
spack install flangwatch out for the installation path, the flang wrapper script in there is ready to use.
-
(optional) setup Flang as a compiler inside spack if you want to build spack package with flang:
spack compiler add path/to/flang/binNow you might want to edit your
~/.spack/*/compilers.yamlto combineflangwith any c compiler of your choice.
To test your installation, create a simple "hello world" program, like the following:
program hello
print *, 'hello world'
end
Next, compile the program in the following manner. We will assume the program is called hello.f90
% flang hello.f90
If the build succeeds, then you can execute the program in the following manner:
% ./a.out
For a list of compiler options, enter
% flang -help
The Flang compiler supports accepts all clang 4.0 compiler options and supports many, as well as the following flang-specific compiler options:
-noFlangLibs Do not link against Flang libraries
-mp Enable OpenMP and link with with OpenMP library libomp
-nomp Do not link with OpenMP library libomp
-Mbackslash Treat backslash character like a C-style escape character
-Mno-backslash Treat backslash like any other character
-Mbyteswapio Swap byte-order for unformatted input/output
-Mfixed Assume fixed-format source
-Mextend Allow source lines up to 132 characters
-Mfreeform Assume free-format source
-Mpreprocess Run preprocessor for Fortran files
-Mrecursive Generate code to allow recursive subprograms
-Mstandard Check standard conformance
-Msave Assume all variables have SAVE attribute
-module path to module file (-I also works)
-Mallocatable=95 Select Fortran 95 semantics for assignments to allocatable objects (Default)
-Mallocatable=03 Select Fortran 03 semantics for assignments to allocatable objects
-static-flang-libs Link using static Flang libraries
-M[no]daz Treat denormalized numbers as zero
-M[no]flushz Set SSE to flush-to-zero mode
-Mcache_align Align large objects on cache-line boundaries
-M[no]fprelaxed This option is ignored
-fdefault-integer-8 Treat INTEGER and LOGICAL as INTEGER*8 and LOGICAL*8
-fdefault-real-8 Treat REAL as REAL*8
-i8 Treat INTEGER and LOGICAL as INTEGER*8 and LOGICAL*8
-r8 Treat REAL as REAL*8
-fno-fortran-main Don't link in Fortran main