David and Hanspeter,
The deprecation of Boost support, in favor of OpenMP, in the gromacs
2016 release motivated me to enhance the llvm39 and future llvmXY packaging
so that fink package maintainers can use the LLVM.org clang compilers for
OpenMP support in a more transparent manner. The proposed changes for
llvm39-3.9.0-2 cover the following...
1) Back ported the upstream changes to clang which cause the compiler
unconditionally emit -lto_library to assist the linker in locating the
correct libLTO.dylib for -flto. This eliminates the need for the previous
local ld shell script hack. The new changes also allow clang to find the
correct location even when the compiler is invoked through a symlink.
2) Copy libomp.dylib as well as the libgomp.dylib and libiomp5.dylib
symlinks to %p/lib/libomp for a new common libomp-shlibs split-off package.
Note that libomp shared library is an odd duck in that it exists without an
explicit so version by design so there is no libomp.dylib for the new
common libomp-dev split-off. Each clangXY package will run against the
latest libomp-dev and libomp-shlibs just as it does with the common
libcxx1-dev and libcxx1-shlibs packages.
3) Since the initial llvm39-3.9.0-1 release still had libomp.dylib located
at %p/opt/llvm-$brv/lib, a copy is retained there for legacy binaries. This
legacy copy will be dropped in the llvm40 packaging as that will never have
libomp.dylib in %p/opt/llvm-$brv/lib.
4) Move the omp.h header into a new common libomp-dev split-off package at
%p/include/libomp with the existing copy in the clang39 package
at %p/opt/llvm-$brv/lib/clang/%v/include replaced by a symlink pointing at
the common copy from libomp-dev at %p/include/libomp/omp.h. The new
libomp-dev package is BuildDependsOnly: false as it has to remain present
for multiple clangXY packages.
5) Add a new common llvm-clang split-off package containing symlinks to the
clang compilers as llvm-clang and llvm-clang++.
This packaging is posted on fink tracker at
https://sourceforge.net/p/fink/package-submissions/4831/ and its use
demonstrated for the new gromacs 2016 release at
https://sourceforge.net/p/fink/package-submissions/4827/.
This redesign of the llvm39 and future packages means that all any
maintainer who wants to use OpenMP has to add is...
BuildDepends: llvm-clang, libomp-dev
Depends: libomp-shlibs
SetCC: llvm-clang
SetCXX: llvm-clang++
which will decouple the builds from any specific release of llvmXY as long
as it provides llvm-clang.
Jack
ps David, at some point we may want to add a cctools package back to fink
built like MacPorts against the latest llvm.org release. The -flto option
requires an ar and ranlib compiled against the newest llvm release in order
to create library archives as previously noted in the DescUsage of the
clang39 split-off...
To use LTO, make sure builds set AR=%p/opt/llvm-3.9/bin/llvm-ar
and RANLIB=%p/opt/llvm-3.9/bin/llvm-ranlib.
pps I really doubt we will ever see Apple add libomp to Xcode as there is
no marketing reason to do it as the OpenMP parallel programing standard
competes with Blocks.
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