[Bug testsuite/80092] New: Add effective-target keywords for unsupported nvptx features

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80092

            Bug ID: 80092
           Summary: Add effective-target keywords for unsupported nvptx
                    features
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: testsuite
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

Atm, when running for target nvptx, we run into unsupported features in the
tests.

F.i. in the g++ testsuite:
...
$ grep -c "sorry, unimplemented:" g++.log 
12693
...

more in detail:
...
$ grep "sorry, unimplemented:" g++.log | sed 's/.*sorry, unimplemented://' |
dos2unix | sort -u 
 converting lambda which uses '...' to function pointer
 global constructors not supported on this target
 global destructors not supported on this target
 indirect jumps are not available on this target
 mangling __underlying_type
 non-trivial designated initializers not supported
 passing arguments to ellipsis of inherited constructor 'B::B(int, ...)
[inherited from A]'
 target cannot support alloca.
 target cannot support nonlocal goto.
...

All those tests are FAILs, while they should be UNSUPPORTED.

In principle, having those as FAILs is not a problem when regression testing.
We can compare tests results, and only look at changes.

But it's better to introduce effective-target keywords for those features, and
mark the tests as such. That will reduce the noise rate because of unsupported
features being used or not due to code generation changes.