The Offload and Flang-RT had the ability to compile GTest themselves.
But in bootstrapping builds, LLVM_LIBRARY_OUTPUT_INTDIR points to the
same location as the stage1 build. If both are building GTest, they
everwrite each others `libllvm_gtest.a` and `libllvm_test_main.a` which
causes #143134.
This PR removes the ability for the Offload/Flang-RT runtimes to build
their own GTest and instead relies on the stage1 build of GTest. This
was already the case with LLVM_INSTALL_GTEST=ON configurations. For
LLVM_INSTALL_GTEST=OFF configurations, we now also export gtest into the
buildtree configuration. Ultimately, this reduces combinatorial
explosion of configurations in which unittests could be built
(LLVM_INSTALL_GTEST=ON, GTest built by Offload, GTest built by Flang-RT,
GTest built by Offload and also used by Flang-RT).
GTest and therefore Offload/Runtime unittests will not be available if
the runtimes are configured against an LLVM install tree. Since llvm-lit
isn't available in the install tree either, it doesn't matter.
Note that compiler-rt and libc also use GTest in non-default
configrations. libc also depends on LLVM's GTest build (and would
error-out if unavailable), but compiler-rt builds it completely
different.
Fixes#143134
When building Flang with Clang, we need to do the same quadmath.h
wrapping as we do for flang-rt. I extracted the CMake code
into FlangCommon.cmake, and cleaned up the arguments passing
to execute_process (note that `-###` was treated as `-` in the original
code, because `#` starts a comment). I believe the Clang command
does not require the input source file, so I removed it as well.
Summary:
This patch adds initial support for compiling `flang-rt` directly for
the GPU. The method used here matches what's already done for `libc` and
`libc++` for the GPU and builds off of those projects.
Mainly this requires setting up some flags and setting the sources that
currently work. This will deposit the resulting library in the
appropriate directory. These files are then intended to be linked via
`-Xoffload-linker` support in the offloading driver.
```
lib/clang/21/lib/nvptx64-nvidia-cuda/libflang_rt.runtime.a
lib/clang/21/lib/amdgcn-amd-amdhsa/libflang_rt.runtime.a
```
This is obviously missing a lot of functions, mainly the `io` support.
Most of what we cannot support is due to using POSIX things that just
don't make sense on the GPU. Stuff like `pthreads` or `sema`.
Getting unit tests to run on this will also be a challenge. We could run
tests the same way we do with `libc`, but the problem there is that the
`libc` test suite is freestanding while `gtest` currently doesn't
compile on the GPU bcause it uses a lot of weird stuff. If the unit
tests were simply `int main` then it would work.
I don't understand the actual runtime code very well, I'd appreciate
some guidance on how to actually support Fortran IO from this interface.
As I understand it, Fortran IO requires a stack-like operation, which
conflicts with the SIMT model GPUs use. Worst case scenario we could
burn some LDS to keep a stack, or serialize it somehow since we can
always just iterate over all the active lanes.
Building this right now looks like this, which depends on the arguments
added in https://github.com/llvm/llvm-project/pull/131695.
```
-DRUNTIMES_nvptx64-nvidia-cuda_LLVM_ENABLE_RUNTIMES=compiler-rt;libc;libcxx;libcxxabi;flang-rt \
-DRUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES=compiler-rt;libc;libcxx;libcxxabi;flang-rt \
-DRUNTIMES_nvptx64-nvidia-cuda_FLANG_RT_LIBC_PROVIDER=llvm \
-DRUNTIMES_nvptx64-nvidia-cuda_FLANG_RT_LIBCXX_PROVIDER=llvm \
-DRUNTIMES_amdgcn-amd-amdhsa_FLANG_RT_LIBC_PROVIDER=llvm \
-DRUNTIMES_amdgcn-amd-amdhsa_FLANG_RT_LIBCXX_PROVIDER=llvm
```
Summary:
This patch adds an interface that uses an in-tree build of LLVM's libc
and libc++.
This is done using the `-DFLANG_RT_LIBC_PROVIDER=llvm` and
`-DFLANG_RT_LIBCXX_PROVIDER=llvm` options. Using `libc` works in terms
of CMake, but the LLVM libc is not yet complete enough to compile all
the files.
I thought I guessed a fix in #130836, but I was wrong.
We actually had the same code in
`flang/cmake/modules/FlangCommon.cmake`.
The check does not pass in flang-rt bootstrap build, because
`-nostdinc++` is added for all `runtimes` checks.
I decided to make the check with the C header, though, I am still
unsure whether it is reliable with a clang that has not been
installed (it is taken from the build structure during flang-rt
configure step).
I verified that this PR enables REAL(16) math entries on aarch64.
When compiling Flang-RT with Clang, query Clang for the GCC installation
it uses. If found, create `quadmath_wrapper.h` that points to the
`quadmath.h` of that GCC installation.
`quadmath.h` is only available when compiling with gcc, and Clang has no
equivalent even though gcc's version compiles fine with Clang (at least
up to and including gcc 13). It is still available into gcc's
installation resource dir (in constrast to a system-wide indirectory
such as `/usr/include` or `/usr/local/include`) and therefore not
available to any compiler other than the gcc of that installation.
quadmath may also be a different OS package than gcc itself, so it is
not necessarily presesent.
Clang actually already appropriates a GCC installation for its libraries
such that `libquadmath.a` is already found, but it does not do so for
the include paths. Because adding that directory to the header search
path may have wide-reaching consquences, we create only a wrapper header
that points to the real `quadmath.h` in the same GCC installation that
Clang uses.
This patch is to explicitly link the pthread library when building
shared flang-rt.
On AIX, for example, it needs to link in `libpthread.a` explicitly in
order to resolve the references to those `pthread_*` functions in
`include/flang-rt/runtime/lock.h`
Make it possible to change the path used to install flang-rt library.
This is particularly necessary for standalone builds, where the CMake
script currently hardwires the default clang install path, and therefore
is incorrect for distributions that override it. However, for
consistency I have made it configurable unconditionally, preserving the
current defaults.
After commit b55f751, the flang-rt build on AIX is missing `-D_LARGE_FILE_API
-D_XOPEN_SOURCE=700` in compiling the source. This patch is to add the
compile definitions.
---------
Co-authored-by: Michael Kruse <github@meinersbur.de>
Under non-Windows platforms, also create a dynamic library version of
the runtime. Build of either version of the library can be switched on
using FLANG_RT_ENABLE_STATIC=ON respectively FLANG_RT_ENABLE_SHARED=ON.
Default is to build only the static library, consistent with previous
behaviour. This is because the way the flang driver invokes the linker,
most linkers choose the dynamic library by default, if available.
Building the dynamic library therefore causes flang-built executables to
depend on `libflang_rt.so`, unless explicitly told otherwise.
Extract Flang's runtime library to use the LLVM_ENABLE_RUNTIME
mechanism. It will only become active when
`LLVM_ENABLE_RUNTIMES=flang-rt` is used, which also changes the
`FLANG_INCLUDE_RUNTIME` to `OFF` so the old runtime build rules do not
conflict. This also means that unless `LLVM_ENABLE_RUNTIMES=flang-rt` is
passed, nothing changes with the current build process.
Motivation:
* Consistency with LLVM's other runtime libraries (compiler-rt, libc,
libcxx, openmp offload, ...)
* Allows compiling the runtime for multiple targets at once using the
LLVM_RUNTIME_TARGETS configuration options
* Installs the runtime into the compiler's per-target resource directory
so it can be automatically found even when cross-compiling
Also see RFC discussion at
https://discourse.llvm.org/t/rfc-use-llvm-enable-runtimes-for-flangs-runtime/80826
This reverts commit 6403287eff71a3d6f6c862346d6ed3f0f000eb70.
This is failing on all but 1 of Linaro's flang builders.
CMake Error at /home/tcwg-buildbot/worker/clang-aarch64-full-2stage/llvm/flang-rt/unittests/CMakeLists.txt:37 (message):
Target llvm_gtest not found.
See discourse thread https://discourse.llvm.org/t/rfc-support-cmake-option-to-control-link-type-built-for-flang-runtime-libraries/71602/18 for full details.
Flang-rt is the new library target for the flang runtime libraries. It builds the Flang-rt library (which contains the sources of FortranRuntime and FortranDecimal) and the Fortran_main library. See documentation in this patch for detailed description (flang-rt/docs/GettingStarted.md).
This patch aims to:
- integrate Flang's runtime into existing llvm infrasturcture so that Flang's runtime can be built similarly to other runtimes via the runtimes target or via the llvm target as an enabled runtime
- decouple the FortranDecimal library sources that were used by both compiler and runtime so that different build configurations can be applied for compiler vs runtime
- add support for running flang-rt testsuites, which were created by migrating relevant tests from `flang/test` and `flang/unittest` to `flang-rt/test` and `flang-rt/unittest`, using a new `check-flang-rt` target.
- provide documentation on how to build and use the new FlangRT runtime
Reviewed By: DanielCChen
Differential Revision: https://reviews.llvm.org/D154869
