[Bug c++/98862] New: Complex reduction support in offload region

[Bug c++/98862] New: Complex reduction support in offload region

[xw111luoye at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98862

            Bug ID: 98862
           Summary: Complex reduction support in offload region
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: xw111luoye at gmail dot com
  Target Milestone: ---

Using std::complex type in offload region is highly desired.

$ g++ -fopenmp complex_reduction.cpp
ptxas /tmp/cceLNaYr.o, line 484; error   : Label expected for argument 0 of
instruction 'call'
ptxas /tmp/cceLNaYr.o, line 484; error   : Function '_ZNSt7complexIfEC1Eff' not
declared in this scope
ptxas /tmp/cceLNaYr.o, line 484; fatal   : Call target not recognized
ptxas fatal   : Ptx assembly aborted due to errors
nvptx-as: ptxas returned 255 exit status
mkoffload: fatal error: x86_64-pc-linux-gnu-accel-nvptx-none-gcc returned 1
exit status
compilation terminated.
lto-wrapper: fatal error:
/soft/gcc/gcc-11-dev-2021-01-27/bin/../libexec/gcc/x86_64-pc-linux-gnu/11.0.0//accel/nvptx-none/mkoffload
returned 1 exit status
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status

$ g++ -fopenmp -O2 complex_reduction.cpp
unresolved symbol __atomic_compare_exchange_16
collect2: error: ld returned 1 exit status
mkoffload: fatal error: x86_64-pc-linux-gnu-accel-nvptx-none-gcc returned 1
exit status
compilation terminated.
lto-wrapper: fatal error:
/soft/gcc/gcc-11-dev-2021-01-27/bin/../libexec/gcc/x86_64-pc-linux-gnu/11.0.0//accel/nvptx-none/mkoffload
returned 1 exit status
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status

The -O2 is more useful for production. Fixing both are desired.

source code:
https://github.com/ye-luo/openmp-target/blob/master/hands-on/tests/complex/complex_reduction.cpp

[Bug target/98862] Complex reduction support in offload region

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98862

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |burnus at gcc dot gnu.org,
                   |                            |jakub at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
libstdc++-v3 isn't supported ATM on either nvptx* or amdgcn* offloading, so if
one needs anything from libstdc++, it will not work.
As for the 16 byte atomics, I thought this was meant to be solved through
-latomic, but I might misremember.

[Bug target/98862] Complex reduction support in offload region

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98862

--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #1)
> libstdc++-v3 isn't supported ATM on either nvptx* or amdgcn* offloading, so
> if one needs anything from libstdc++, it will not work.

I can confirm that it does not work with '-O0', showing that the
symbol
   _ZNSt7complexIfEC1Eff
alias
   std::complex<float>::complex(float, float)
is missing.

But:

> As for the 16 byte atomics, I thought this was meant to be solved through
> -latomic, but I might misremember.

Yes,
  $ g++ -fopenmp -O2 complex_reduction.cpp -foffload=-latomic
works – both compiling and running (on nvptx).

Note the added '-foffload=-latomic' (and -O2).
See also: https://gcc.gnu.org/wiki/Offloading#Compilation_options

[Bug target/98862] Complex reduction support in offload region

[xw111luoye at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98862

--- Comment #3 from Ye Luo <xw111luoye at gmail dot com> ---
Cool. -foffload=-latomic resolved my problem.

[Bug target/98862] Complex reduction support in offload region

[xw111luoye at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98862

Ye Luo <xw111luoye at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Ye Luo <xw111luoye at gmail dot com> ---
No fix needed.