PR tree-optimization/42963

	PR tree-optimization/42963
	* tree-cfg.c (touched_switch_bbs): New static variable.
	(group_case_labels_stmt): New function broken out from ...
	(group_case_labels): ... here, use the above.
	(start_recording_case_labels): Allocate touched_switch_bbs.
	(end_recording_case_labels): Deallocate it, call
	group_case_labels_stmt.
	(gimple_redirect_edge_and_branch): Remember index of affected BB.

testsuite/
	* testsuite/gcc.dg/pr42963.c: New testcase.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@158345 138bc75d-0d04-0410-961f-82ee72b054a4