[Openmp-dev] Offloading application build with a Trunk Debug Clang is so slow

[Itaru Kitayama via Openmp-dev]

It isn't much exciting.
$ time clang++ -fuse-ld=gold -g -fopenmp -fopenmp-targets=nvptx64 test.cpp
^[[O^[[Iptxas /tmp/test-e95684.s, line 2715; warning : Instruction 'vote'
without '.sync' is deprecated since PTX ISA version 6.0 and will be
discontinued in a future PTX ISA version

real 0m19.138s
user 0m18.377s
sys 0m0.375s
[kitayama1 at juron1-adm pcp0151]$ time clang++ -fuse-ld=ld -g -fopenmp
-fopenmp-targets=nvptx64 test.cpp
^[[O^[[I^[[Optxas /tmp/test-498b51.s, line 2715; warning : Instruction
'vote' without '.sync' is deprecated since PTX ISA version 6.0 and will be
discontinued in a future PTX ISA version

real 0m19.373s
user 0m18.677s
sys 0m0.477s

On Fri, Dec 20, 2019 at 8:46 AM Alexey Bataev <a.bataev at hotmail.com> wrote:

> Try to use gold linker instead of default ld.
>
> Best regards,
> Alexey Bataev
>
> 19 дек. 2019 г., в 01:16, Itaru Kitayama via Openmp-dev <
> openmp-dev at lists.llvm.org> написал(а):
>
> 
> On POWER8, my app builds 40 minutes with the Debug Clang (40 times
> increase of time, when
> it is built with Release Clang), but on an x86 host, it just takes about
> 10 minutes and it is bearable.
>
> Could this be PowerPC specific, is it why most people aren't aware of the
> slowness?
>
>
> On Thu, Dec 19, 2019 at 1:38 PM Itaru Kitayama <itaru.kitayama at gmail.com>
> wrote:
>
>> Trunk Clang built with setting both variables to
>> -DCMAKE_BUILD_TYPE=Release -DLIBOMPTARGET_ENABLE_DEBUG=False
>> builds my application in a minute or so.
>>
>> On Thu, Dec 19, 2019 at 8:18 AM Itaru Kitayama <itaru.kitayama at gmail.com>
>> wrote:
>>
>>> The CMake was executed as below:
>>>
>>> cmake -GNinja -DCMAKE_BUILD_TYPE=Debug -DLIBOMPTARGET_ENABLE_DEBUG=True
>>> -DCMAKE_INSTALL_PREFIX=$SCRATCH/pcp0151/opt/clang/${today}
>>> -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
>>> -DGCC_INSTALL_PREFIX=/gpfs/software/opt/gcc/7.2.0/
>>> -DLLVM_ENABLE_PROJECTS="clang;openmp;libcxx;libcxxabi;lld"
>>> -DCLANG_OPENMP_NVPTX_DEFAULT_ARCH=sm_60
>>> -DLIBOMPTARGET_NVPTX_COMPUTE_CAPABILITIES=60
>>> -DLLVM_TARGETS_TO_BUILD="PowerPC;NVPTX"
>>> $SCRATCH/pcp0151/projects/llvm-project/llvm
>>>
>>> On Thu, Dec 19, 2019 at 7:57 AM Itaru Kitayama <itaru.kitayama at gmail.com>
>>> wrote:
>>>
>>>> The Clang at this commit:
>>>> commit 1c49553c19a7044fbbf4528b732926f19f210e54
>>>> Author: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
>>>> Date:   Thu Dec 12 20:51:13 2019 +0100
>>>> [kitayama1 at juron1-adm pcp0151]$ time clang++ -g -fopenmp
>>>> -fopenmp-targets=nvptx64 mini.cpp
>>>>
>>>> real 0m2.344s
>>>> user 0m2.231s
>>>> sys 0m0.049s
>>>> Release Clang 9
>>>> [[kitayama1 at juron1-adm pcp0151]$ time clang++ -g -fopenmp
>>>> -fopenmp-targets=nvptx64 mini.cpp
>>>>
>>>> real 0m0.693s
>>>> user 0m0.533s
>>>> sys 0m0.047s
>>>>
>>>> On Thu, Dec 19, 2019 at 5:32 AM Jon Chesterfield <
>>>> jonathanchesterfield at gmail.com> wrote:
>>>>
>>>>> Ah, OK. In that case I still suspect a regression in clang, as opposed
>>>>> to a change in the library. Does the compile time remain very slow if you
>>>>> roll deviceRTL back by a few days?
>>>>>
>>>>> On Wed, Dec 18, 2019 at 8:30 PM Itaru Kitayama <
>>>>> itaru.kitayama at gmail.com> wrote:
>>>>>
>>>>>> Sorry, of course it should include this #pragma
>>>>>> omp target parallel for for(;;) {}. My local Debug Clang is updated
>>>>>> daily, so the tool chain is pretty much up to date.
>>>>>>
>>>>>> On Thu, Dec 19, 2019 at 5:24 Jon Chesterfield <
>>>>>> jonathanchesterfield at gmail.com> wrote:
>>>>>>
>>>>>>> On Wed, Dec 18, 2019 at 8:13 PM Itaru Kitayama <
>>>>>>> itaru.kitayama at gmail.com> wrote:
>>>>>>>
>>>>>>>> The app build time increases can be reproduced with a simple int
>>>>>>>> main() {} code.
>>>>>>>>
>>>>>>>
>>>>>>> I thought the problem was with the compile time of deviceRTL.
>>>>>>>
>>>>>>> If you're compiling int main() {}, then there's no openmp involved,
>>>>>>> so that seems out of scope for this list.
>>>>>>>
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