openmp: Avoid ICEs due to orphaned labels in OpenMP regions [PR99322]

openmp: Avoid ICEs due to orphaned labels in OpenMP regions [PR99322]

When performing cfg cleanup at the end of cfg pass, if there are any OpenMP
regions and some basic blocks are unreachable and contain forced labels,
remove_bb moves the labels to previous bb, but if the two bb belong to different
OpenMP regions, that means it will end up in a different function from where
it was assumed to be and checked e.g. during gimplification or OpenMP region
SESE checking.

The following patch will place the labels to some bb from the right OpenMP
region if the previous bb is not that.  I think it should happen very rarely,
normally the bbs from each OpenMP region should be from the before-cfg pass
adjacent and the problems will usually be only if the OpenMP regions are
no-return, so I hope it isn't fatal that it searches through all bbs on the miss.
If it turns out to be a problem, it can always lazily create some better data
structure and maintain it through bb removals when it reaches that case the
first time.

2021-03-05  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/99322
	* tree-cfg.c (bb_to_omp_idx): New variable.
	(execute_build_cfg): Release the bb_to_omp_idx vector after
	cleanup_tree_cfg returns.
	(handle_abnormal_edges): Remove bb_to_omp_idx argument, adjust
	for bb_to_omp_idx being a vec<int> instead of pointer to array
	of ints.
	(make_edges): Remove bb_to_omp_idx local variable, don't pass
	it to handle_abnormal_edges, adjust for bb_to_omp_idx being a
	vec<int> instead of pointer to array of ints and don't free/release
	it at the end.
	(remove_bb): When removing a bb and placing forced label somewhere
	else, ensure it is put into the same OpenMP region during cfg
	pass if possible or to entry successor as fallback.  Unregister
	bb from bb_to_omp_idx.

	* c-c++-common/gomp/pr99322.c: New test.