This patch fixes a small bug where the new flang runtime types for
Windows (static, static_dbg, etc) are not built when the FortranRuntime
is requested by adding the missing dependency.
Currently flang's runtime libraries are only built for the specific CRT
that LLVM itself was built against. This patch adds the cmake logic for
building a separate runtime for each CRT configuration and adds a flag
for selecting a CRT configuration to link against.
To accomplish this, this patch creates an optional list of environment
variable default values to be set by the runtime to allow directly using
the existing runtime implementation of FORT_CONVERT for I/O conversions.
Make sure that FortranDecimal, FortranRuntime and Fortran_main are
installed/packaged even when LLVM_INSTALL_TOOLCHAIN_ONLY is enabled.
They are used by flang to link executables, so they should be provided
even with minimal installs.
Differential Revision: https://reviews.llvm.org/D131670
This is compiled as C code, so it's a good idea to be explicit about the
prototype. Clang complains about this when -Wstrict-prototypes is used.
Differential Revision: https://reviews.llvm.org/D125672
At the moment the Fortran_main library is not installed, so it cannot be
found by the driver when run from an install directory. This patch fixes
the issue by replacing llvm_add_library with add_flang_library, which
already contains all the proper incantations for installing a library.
It also enhances add_flang_library to support a STATIC arg which forces
the library to be static even when BUILD_SHARED_LIBS is on.
Differential Revision: https://reviews.llvm.org/D124759
Co-authored-by: Dan Palermo <Dan.Palermo@amd.com>
This patch adds 2 missing items required for `flang-new` to be able to
generate executables:
1. The Fortran_main runtime library, which implements the main entry
point into Fortran's `PROGRAM` in Flang,
2. Extra linker flags to include Fortran runtime libraries (e.g.
Fortran_main).
Fortran_main is the bridge between object files generated by Flang and
the C runtime that takes care of program set-up at system-level. For
every Fortran `PROGRAM`, Flang generates the `_QQmain` function.
Fortran_main implements the C `main` function that simply calls
`_QQmain`.
Additionally, "<driver-path>/../lib" directory is added to the list of
search directories for libraries. This is where the required runtime
libraries are currently located. Note that this the case for the build
directory. We haven't considered installation directories/targets yet.
With this change, you can generate an executable that will print `hello,
world!` as follows:
```bash
$ cat hello.f95
PROGRAM HELLO
write(*, *) "hello, world!"
END PROGRAM HELLO
$ flang-new -flang-experimental-exec hello.f95
./a.out
hello, world!
```
NOTE 1: Fortran_main has to be a static library at all times. It invokes
`_QQmain`, which is the main entry point generated by Flang for the
given input file (you can check this with `flang-new -S hello.f95 -o - |
grep "Qmain"`). This means that Fortran_main has an unresolved
dependency at build time. The linker will allow this for a static
library. However, if Fortran_main was a shared object, then the linker
will produce an error: `undefined symbol: `_QQmain`.
NOTE 2: When Fortran runtime libraries are generated as shared libraries
(excluding Fortran_main, which is always static), you will need to
tell the dynamic linker (by e.g. tweaking LD_LIBRARY_PATH) where to look
for them when invoking the executables. For example:
```bash
LD_LIBRARY_PATH=$LD_LIBRARY_PATH:<flang-build-dir>/lib/ ./a.out
```
NOTE 3: This feature is considered experimental and currently guarded
with a flag: `-flang-experimental-exec`.
Differential Revision: https://reviews.llvm.org/D122008
[1] https://github.com/flang-compiler/f18-llvm-project
CREDITS: Fortran_main was originally written by Eric Schweitz, Jean
Perier, Peter Klausler and Steve Scalpone in the fir-dev` branch in [1].
Co-authored-by: Eric Schweitz <eschweitz@nvidia.com>
Co-authored-by: Peter Klausler <pklausler@nvidia.com>
Co-authored-by: Jean Perier <jperier@nvidia.com>
Co-authored-by: Steve Scalpone <sscalpone@nvidia.com
