[Bug middle-end/101551] New: [offloading] Differences in diagnostics etc.

[Bug middle-end/101551] New: [offloading] Differences in diagnostics etc.

[tschwinge at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101551

            Bug ID: 101551
           Summary: [offloading] Differences in diagnostics etc.
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: openacc, openmp
          Severity: minor
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tschwinge at gcc dot gnu.org
                CC: burnus at gcc dot gnu.org, jakub at gcc dot gnu.org
  Target Milestone: ---

There are differences in diagnostics etc. depending on whether offloading is
disabled or enabled, as we already had found in
<http://mid.mail-archive.com/87pmyg4y9s.fsf@euler.schwinge.homeip.net>
"openacc: Warnings for strange partitioning choices for parallel regions" and
following.

Additionally, I just noticed that calling 'lang_hooks.decl_printable_name
(current_function_decl, 2)' in 'gcc/omp-offload.c:execute_oacc_device_lower'
for an OpenACC 'routine' 'void ROUTINE (float)', for C that returns 'ROUTINE',
for C++ 'ROUTINE(float)' for offloading enabled and 'void ROUTINE(float)'
otherwise (notice difference regarding return type), for corresponding Fortran
'routine_' for offloading enabled and 'routine' otherwise (notice difference in
'_' suffix).

Low priority certainly, but would be nice to fix/unify at some point, because
this occasionally necessitates special care when writing testcases.

[Bug middle-end/101551] [offloading] Differences in diagnostics etc.

[tschwinge at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101551

--- Comment #1 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
Similarly, when calling 'lang_hooks.decl_printable_name (current_function_decl,
2)' in 'gcc/omp-offload.c:execute_oacc_device_lower' for:

    #pragma acc routine
    template <typename T> T
    ROUTINE(int val)
    { [...] }

..., for 'ROUTINE<float>' instantiated that returns 'ROUTINE<float>(int)float'
for offloading enabled and 'T ROUTINE(int) [with T = float]' otherwise.

[Bug middle-end/101551] [offloading] Differences in diagnostics etc.

[tschwinge at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101551

--- Comment #2 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
I've noticed that with an offloading-enabled build of GCC we're losing "note:
in expansion of macro '[...]'" diagnostics.  (Effectively
'-ftrack-macro-expansion=0'?)

For example, 'libgomp.oacc-c-c++-common/vred2d-128.c' with '-fopenacc
-Wuninitialized' for a (default) GCC build without
'--enable-offload-targets=[...]':

    [...]
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c: In function ‘test1’:
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c:34:8: warning: ‘t1’ is used
uninitialized [-Wuninitialized]
       34 |          "acc loop vector reduction(+:t1) reduction(-:t2)")
          |        ^ ~
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c:11:14: note: ‘t1’ was declared
here
       11 |   long i, j, t1, t2, t3;                        \
          |              ^~
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c:33:1: note: in expansion of
macro ‘gentest’
       33 | gentest (test1, "acc parallel loop gang vector_length (128)
firstprivate (t1, t2)",
          | ^~~~~~~
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c:34:8: warning: ‘t2’ is used
uninitialized [-Wuninitialized]
    [...]

... vs. a GCC build with '--enable-offload-targets=[...]':

    [...]
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c: In function ‘test1’:
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c:34:8: warning: ‘t1’ is used
uninitialized [-Wuninitialized]
       34 |          "acc loop vector reduction(+:t1) reduction(-:t2)")
          |        ^ ~
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c:11:14: note: ‘t1’ was declared
here
       11 |   long i, j, t1, t2, t3;                        \
          |              ^~
    [...]/libgomp.oacc-c-c++-common/vred2d-128.c:34:8: warning: ‘t2’ is used
uninitialized [-Wuninitialized]
    [...]

Note that an explicit '-foffload=disable' does not cure this.

[Bug middle-end/101551] [offloading] Differences in diagnostics etc.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101551

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Thomas Schwinge <tschwinge@gcc.gnu.org>:

https://gcc.gnu.org/g:3723aedaad20a129741c2f6f3c22b3dd1220a3fc

commit r13-1611-g3723aedaad20a129741c2f6f3c22b3dd1220a3fc
Author: Thomas Schwinge <thomas@codesourcery.com>
Date:   Tue Jul 12 08:17:37 2022 +0200

    XFAIL 'offloading_enabled' diagnostics issue in
'libgomp.oacc-c-c++-common/reduction-5.c' [PR101551]

    Fix-up for recent commit 06b2a2abe26554c6f9365676683d67368cbba206
    "Enhance '_Pragma' diagnostics verification in OMP C/C++ test cases".
    Supposedly it's the same issue as in
    <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101551#c2>, where I'd
    noted that:

    | [...] with an offloading-enabled build of GCC we're losing
    | "note: in expansion of macro '[...]'" diagnostics.
    | (Effectively '-ftrack-macro-expansion=0'?)

            PR middle-end/101551
            libgomp/
            * testsuite/libgomp.oacc-c-c++-common/reduction-5.c: XFAIL
            'offloading_enabled' diagnostics issue.