openmp, c++: Fix up OpenMP/OpenACC handling in C++ modules [PR119102]

openmp, c++: Fix up OpenMP/OpenACC handling in C++ modules [PR119102]

modules.cc has apparently support for extensions and attempts to ensure
that if a module is compiled with those extensions enabled, sources which
use the module are compiled with the same extensions.
The only extension supported is SE_OPENMP right now.
And the use of the extension is keyed on streaming out or in OMP_CLAUSE
tree.
This is undesirable for several reasons.
OMP_CLAUSE is the only tree which can appear in the IL even without
-fopenmp/-fopenmp-simd/-fopenacc (when simd ("notinbranch") or
simd ("inbranch") attributes are used), and it can appear also in all
the 3 modes mentioned above.  On the other side, with the exception of
arguments of attributes added e.g. for declare simd where no harm should
be done if -fopenmp/-fopenmp-simd isn't enabled later on, OMP_CLAUSE appears
in OMP_*_CLAUSES of OpenMP/OpenACC construct trees.  And those construct
trees often have no clauses at all, so keying the extension on OMP_CLAUSE
doesn't catch many cases that should be caught.
Furthermore, for OpenMP we have 2 modes, -fopenmp-simd which parses some
OpenMP but constructs from that mostly OMP_SIMD and a few other cases,
and -fopenmp which includes that and far more on top of that; and there is
also -fopenacc.

So, this patch stops setting/requesting the extension on OMP_CLAUSE,
introduces 3 extensions rather than one (SE_OPENMP_SIMD, SE_OPENMP and
SE_OPENACC) and keyes those on OpenMP constructs from the -fopenmp-simd
subset, other OpenMP constructs and OpenACC constructs.

2025-03-05  Jakub Jelinek  <jakub@redhat.com>

	PR c++/119102
gcc/cp/
	* module.cc (enum streamed_extensions): Add SE_OPENMP_SIMD
	and SE_OPENACC, change value of SE_OPENMP and SE_BITS.
	(CASE_OMP_SIMD_CODE, CASE_OMP_CODE, CASE_OACC_CODE): Define.
	(trees_out::start): Don't set SE_OPENMP extension for OMP_CLAUSE.
	Set SE_OPENMP_SIMD extension for CASE_OMP_SIMD_CODE, SE_OPENMP
	for CASE_OMP_CODE and SE_OPENACC for CASE_OACC_CODE.
	(trees_in::start): Don't fail for OMP_CLAUSE with missing
	SE_OPENMP extension.  Do fail for CASE_OMP_SIMD_CODE and missing
	SE_OPENMP_SIMD extension, or CASE_OMP_CODE and missing SE_OPENMP
	extension, or CASE_OACC_CODE and missing SE_OPENACC extension.
	(module_state::write_readme): Write all of SE_OPENMP_SIMD, SE_OPENMP
	and SE_OPENACC extensions.
	(module_state::read_config): Diagnose missing -fopenmp, -fopenmp-simd
	and/or -fopenacc depending on extensions used.
gcc/testsuite/
	* g++.dg/modules/pr119102_a.H: New test.
	* g++.dg/modules/pr119102_b.C: New test.
	* g++.dg/modules/omp-3_a.C: New test.
	* g++.dg/modules/omp-3_b.C: New test.
	* g++.dg/modules/omp-3_c.C: New test.
	* g++.dg/modules/omp-3_d.C: New test.
	* g++.dg/modules/oacc-1_a.C: New test.
	* g++.dg/modules/oacc-1_b.C: New test.
	* g++.dg/modules/oacc-1_c.C: New test.