backport: re PR tree-optimization/87895 (ICE in purge_dead_edges, at cfgrtl.c:3246)

backport: re PR tree-optimization/87895 (ICE in purge_dead_edges, at cfgrtl.c:3246)

	Backported from mainline
	2018-11-20  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/87895
	* omp-simd-clone.c (ipa_simd_modify_function_body): When removing
	or replacing GIMPLE_RETURN, set EDGE_FALLTHRU on the edge to EXIT.
	(simd_clone_adjust): Don't set EDGE_FALLTHRU here. In a loop that
	redirects edges to EXIT to edges to incr_bb, iterate while EXIT
	has any preds and always use EDGE_PRED (, 0).

	* gcc.dg/gomp/pr87895-1.c: New test.
	* gcc.dg/gomp/pr87895-2.c: New test.
	* gcc.dg/gomp/pr87895-3.c: New test.

From-SVN: r275070