Re: OpenMP for both clang and GCC, part II

On 2019-06-05 17:59, Brian Callahan wrote:
> On 6/5/19 7:42 PM, j@bitminer.ca wrote:
>> TLDR: Multi-core is a thing. Let's do it the OpenMP way. My diffs to
>> come.
>>
>> I know some devs have thought about this before. I'm looking for
>> comments
>> or advice on how I can help this along.
>>
>> The clang in base (and flang in ports) currently support OpenMP
>> directives
>> with the -fopenmp option. They are missing the runtime. The LLVM
>> OpenMP
>> runtime could be supplied as a port.
>>
>> The GNU C, C++ and Fortran in ports (gcc version 8.3) currently
>> support
>> OpenMP directives and with a small patch can add OpenMP support to
>> their
>> runtime libraries (gcc-libs). The two OpenMP runtimes (GCC and LLVM)
>> can coexist this way.
>>
>> Example ports, compiler, build system, and status/issues:
>>
>> devel/boost (base-clang gcc-ports, unique build, uncertain
>> support)
>> devel/cmake (base-clang gcc-ports, simple, fails to correctly
>> find OpenMP)
>> graphics/lensfun (base-clang gcc-ports, cmake, unswitchable OpenMP)
>> graphics/GraphicsMagick (base-clang gcc-ports, gnu configure, OpenMP
>> disabled)
>>
>> Proposed changes:
>> - identify ports with embedded (hidden) OpenMP support and patch to
>> disable it
>> (I guess from 10 to 40 such ports aside from the 7 that turn it off
>> now)
>> - fix cmake (and other build systems) to detect both OpenMP
>> implementations
>> - add a new port devel/libomp containing the LLVM OpenMP runtime for
>> clang/flang
>> - patch gcc-libs package to deliver OpenMP runtime support for GNU
>> c/c++/fortran
>> - help port maintainers build with OpenMP flavors if they want it
>>
>> (I have patches for cmake, gcc-libs, and a proposed new devel/libomp
>> package).
>>
>> Eventually ports maintaners will migrate to OpenMP as they can or want
>> to.
>> Users will adopt flavors such as -withopenmp, or -noopenmp, as they
>> become
>> available.
>>
>> Some issues and questions:
>>
>> - this will work for amd64, but will it work for arm64, sparc? Others?
>> - should the flavors be -withopenmp or -noopenmp?
>> - how to successfully detect 90% or more of ports with hidden OpenMP
>> support?
>> I will do this and am looking for advice on how best to approach
>> it.
>> Any pre-existing info would be very welcome.
>>
>> Does anyone have comments? I'll be submitting diffs as I can.
>>
>>
>>
>> --John
>>
>
> On LLVM OpenMP:
> https://marc.info/?l=openbsd-ports&m=155642976702196&w=2
>
> ~Brian

Yes, and also I saw some of your posts to ports from a couple of years
ago
regarding checking for openmp use.

https://marc.info/?l=openbsd-ports&m=151051634223013&w=2

Did you get further that what is stated in the post? I'm thinking math/
and geo/ and graphics/ as the most likely.

--John