Re: XFAIL 'offloading_enabled' diagnostics issue in 'libgomp.oacc-c-c++-common/reduction-5.c' [PR101551] (was: Enhance '_Pragma' diagnostics verification in OMP C/C++ test cases)

[Tobias Burnus <tobias@codesourcery.com>]

Hi,

On 12.07.22 13:50, Lewis Hyatt via Gcc-patches wrote:
> On Tue, Jul 12, 2022 at 2:33 AM Thomas Schwinge <thomas@codesourcery.com> wrote:
>> On 2022-07-11T11:27:12+0200, I wrote:
>>> Oh my, PR101551 "[offloading] Differences in diagnostics etc."
>>> strikes again...  The latter two 'note' diagnostics are currently
>>> only emitted in non-offloading configurations.  I've now pushed to
>>> master branch commit 3723aedaad20a129741c2f6f3c22b3dd1220a3fc
>>> "XFAIL 'offloading_enabled' diagnostics issue in
>>> 'libgomp.oacc-c-c++-common/reduction-5.c' [PR101551]", see attached.
> Would you mind please confirming how I need to run configure in order
> to get this configuration? Then I can look into why the difference in
> location information there. Thanks.

I think the simplest to replicate it without much effort is to run:

cd ${GCC-SRC}/gcc
sed -e 's/ENABLE_OFFLOADING/true/' *.cc */*.cc

I think that covers all cases, which do not need the target lto1.
If they do do - then it becomes more difficult as you need an
offloading compiler. (But that is rather about: diagnostic or
no diagostic and not about having a different diagnostic.)

I think the different diagnostic has the reason stated in
commit r12-135-gbd7ebe9da745a62184052dd1b15f4dd10fbdc9f4

Namely:
----cut---
     It turned out that a compiler built without offloading support
     and one with can produce slightly different diagnostic.

     Offloading support implies ENABLE_OFFLOAD which implies that
     g->have_offload is set when offloading is actually needed.
     In cgraphunit.c, the latter causes flag_generate_offload = 1,
     which in turn affects tree.c's free_lang_data.

     The result is that the front-end specific diagnostic gets reset
     ('tree_diagnostics_defaults (global_dc)'), which affects in this
     case 'Warning' vs. 'warning' via the Fortran frontend.

     Result: 'Warning:' vs. 'warning:'.
     Side note: Other FE also override the diagnostic, leading to
     similar differences, e.g. the C++ FE outputs mangled function
     names differently
----cut------

If the message is from the offload-device's lto1 compiler, it
becomes more difficult to configure+build GCC. See
https://gcc.gnu.org/wiki/Offloading under
"How to build an offloading-enabled GCC"

I hope it helps.

Tobias

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