[Bug debug/103836] New: '-fcompare-debug' failure (length) w/ -fopenacc --param openacc-kernels=decompose

["asolokha at gmx dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103836

            Bug ID: 103836
           Summary: '-fcompare-debug' failure (length) w/ -fopenacc
                    --param openacc-kernels=decompose
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: openacc
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

Created attachment 52061
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52061&action=edit
diff -u o5cia6mf.*.gkd

g++ 12.0.0 20211219 snapshot (g:fcbf94a5be9e0c1ecad92da773a6632b86b7f70a) fails
-fcompare-debug check when compiling the following testcase w/, extracted from
gcc/testsuite/c-c++-common/goacc/nesting-1.c, w/ -fopenacc --param
openacc-kernels=decompose:

extern int i;

void
f_acc_kernels (void)
{
#pragma acc kernels
  {
#pragma acc loop
    for (i = 0; i < 2; ++i)
      ;
  }
}

% x86_64-unknown-linux-gnu-g++-12.0.0 -O1 -fcompare-debug -fopenacc --param
openacc-kernels=decompose -c o5cia6mf.c
x86_64-unknown-linux-gnu-g++-12.0.0: error: o5cia6mf.c: '-fcompare-debug'
failure (length)

Diff between two gkd files attached. I can reproduce the issue only w/ C++
front-end.