[PATCH] [Revised] Initial cmake support

Runtimes OpenMP
1

Attached is the revised initial implementation of cmake support for openmp in llvm.org with the following requested changes implemented.

  1. Indentations normalized to 2 spaces.
  2. The test for APPLE moved above UNIX in setting OS_GEN and fatal error condition added.
  3. Implemented used CMAKE_SHARED_LIBRARY_SUFFIX to set OMP_SHLIBEXT.
  4. Added comment explaining the rational for temporary forcing of…

set(CMAKE_CXX_COMPILER “clang++”)

to insure that the build of ‘make compiler=clang’ is always used, regardless of the actual system compiler, until the openmp build is wired into the llvm bootstrap and can be certain to use its clang compilers. Also note that the warnings added to the COMMON_FLAGS may be compiler-specific. Tested as before on x86_64-apple-darwin12 against the clang compilers from Xcode 5.1.1 and on x86_64 Fedora 15 using current clang-omp 3.4.
Jack
ps We also probably want to add a fatal error message for unsupported arches but first I intend to adjust this file to support powerpc as soon as my clang-omp bootstrap completes on ppc darwin9.

initial_cmake_support_v2.patch (5.56 KB)

2

Below is what I had in mind for the installation commands of CMakelists.txt once we have the cmake build
of openmp hooked up to the llvm bootstrap…

install(
FILES omp.h
PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
DESTINATION lib${LLVM_LIBDIR_SUFFIX}/clang/${CLANG_VERSION}/include
)
install(
FILES libiomp5.${OMP_SHLIBEXT}
PERMISSIONS OWNER_READ OWNER_WRITE OWNER_EXECUTE GROUP_READ GROUP_EXECUTE WORLD_READ WORLD_EXECUTE
DESTINATION lib${LLVM_LIBDIR_SUFFIX}
)

This mimics what we have been doing in fink. Placing the omp.h header in lib${LLVM_LIBDIR_SUFFIX}/clang/${CLANG_VERSION}/include automatically allows the compiler to find it. In fink, we have been installing libiomp5.${OMP_SHLIBEXT} in lib${LLVM_LIBDIR_SUFFIX} and using a patch…

— cfe-3.4.1.src/lib/Driver/Tools.cpp.orig 2014-05-20 16:54:39.000000000 -0400
+++ cfe-3.4.1.src/lib/Driver/Tools.cpp 2014-05-20 17:01:28.000000000 -0400
@@ -5123,9 +5123,12 @@

Args.AddAllArgs(CmdArgs, options::OPT_L);

  • if (Args.hasArg(options::OPT_fopenmp))
  • if (Args.hasArg(options::OPT_fopenmp)) {
  • // Help clang find libiomp5.dylib
  • CmdArgs.push_back(“-L@FINK_PREFIX@/opt/llvm-3.4/lib”);
    // This is more complicated in gcc…
    CmdArgs.push_back(“-liomp5”);
  • }

AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs);

@@ -6690,7 +6693,9 @@

bool OpenMP = Args.hasArg(options::OPT_fopenmp);
if (OpenMP) {

  • CmdArgs.push_back(“-liomp5”);
  • // Help clang find libiomp5.dylib
  • CmdArgs.push_back(“-L@FINK_PREFIX@/opt/llvm-3.4/lib”);
  • CmdArgs.push_back(“-liomp5”);
    }

AddLibgcc(ToolChain.getTriple(), D, CmdArgs, Args);

to help clang find it there. So we would change @FINK_PREFIX@ to the
complete path to the installed lib${LLVM_LIBDIR_SUFFIX}. The alternative
would be to change the patch above to replace -liomp5 with a the full
path to the installed lib${LLVM_LIBDIR_SUFFIX}/libomp5.${OMP_SHLIBEXT}
instead.

This brings up several questions…

  1. Where do you intend to place libomp5.${OMP_SHLIBEXT}?

  2. If it is installed outside of lib${LLVM_LIBDIR_SUFFIX}, how do
    you plan on handling having multiple versions of llvm/clang installed
    on the same machine which will all claim to ownership of libomp5.${OMP_SHLIBEXT}?

My proposal for solving the issue of co-existing libomp5.${OMP_SHLIBEXT} would be…

Create libomp5.${VERSION}.${SOVERSION}.${OMP_SHLIBEXT}, where SOVERSION
is set to the release number of the llvm/clang/openmp release and create a symlink
for libomp5.${OMP_SHLIBEXT} pointing at libomp5.${VERSION}.${SOVERSION}.${OMP_SHLIBEXT}.
Install these two files in lib${LLVM_LIBDIR_SUFFIX} and use additional symlinks to them
in an exposed directory like /usr/lib. These two symlinks in the exposed directory would be
swapped out when a particular releases of llvm/clang/openmp was designated as the system
one (i.e. they would end up in a conflicting clang34-dev or clang35-dev packaging).

I think this would allow binaries to be compiled against a specific release of openmp and
insure that the resulting executables would find the original copy of libiomp5 for that
release of llvm/clang/openmp as installed in lib${LLVM_LIBDIR_SUFFIX} as
libomp5.${VERSION}.${SOVERSION}.${OMP_SHLIBEXT}…

Sorry if that wasn’t as clear as I intended but hopefully you will all get the idea.

3

Please do not do this even as a temp hack.

set(CMAKE_CXX_COMPILER “clang++”)

ATT001.txt (172 Bytes)

4

On further reflection, I guess ${SOVERSION} can be avoided entirely by just bumping the compatibility version on each major llvm/clang/openmp release. Was the soversioning meant to be achieved through through the shared library name? That is, when we have an ABI change in openmp which normally requires a soverson bump, the shared library name would be changed instead (e.g. libiomp5 to libiomp6)? In any case, we still have to consider the installation location of libomp5.${OMP_SHLIBEXT} and how relates to having multiple llvm/clang/openmp releases being installed simultaneously on the same machine.