[PR 91579] Avoid creating redundant PHI nodes in tail-call pass

[PR 91579] Avoid creating redundant PHI nodes in tail-call pass

2019-08-30  Martin Jambor  <mjambor@suse.cz>

	tree-optimization/91579
	* tree-tailcall.c (tailr_arg_needs_copy): New variable.
	(find_tail_calls): Allocate tailr_arg_needs_copy and set its bits as
	appropriate.
	(arg_needs_copy_p): Removed.
	(eliminate_tail_call): Test tailr_arg_needs_copy instead of calling
	arg_needs_copy_p.
	(tree_optimize_tail_calls_1): Likewise.  Free tailr_arg_needs_copy.

	testsuite/
	* gcc.dg/tree-ssa/pr91579.c: New test.

From-SVN: r275062