openmp: Don't reject some valid initializers or conditions of non-rectangular loops...

openmp: Don't reject some valid initializers or conditions of non-rectangular loops [PR102854]

In C++, if an iterator has or might have (e.g. dependent type) class type we
remember the original init expressions and check those separately for presence
of iterators, because for class iterators we turn those into expressions that
always do contain reference to the current iterator.  But this resulted in
rejecting valid non-rectangular loop where the dependent type is later instantiated
to an integral type.

Non-rectangular loops with class random access iterators remain broken, that is something
to be fixed incrementally.

2021-10-27  Jakub Jelinek  <jakub@redhat.com>

	PR c++/102854
gcc/c-family/
	* c-common.h (c_omp_check_loop_iv_exprs): Add enum tree_code argument.
	* c-omp.c (c_omp_check_loop_iv_r): For trees other than decls,
	TREE_VEC, PLUS_EXPR, MINUS_EXPR, MULT_EXPR, POINTER_PLUS_EXPR or
	conversions temporarily clear the 3rd bit from d->kind while walking
	subtrees.
	(c_omp_check_loop_iv_exprs): Add CODE argument.  Or in 4 into data.kind
	if possibly non-rectangular.
gcc/cp/
	* semantics.c (handle_omp_for_class_iterator,
	finish_omp_for): Adjust c_omp_check_loop_iv_exprs caller.
gcc/testsuite/
	* g++.dg/gomp/loop-3.C: Don't expect some errors.
	* g++.dg/gomp/loop-7.C: New test.