PR rtl-optimization/58997

	PR rtl-optimization/58997
	* loop-iv.c (iv_subreg): For IV_UNKNOWN_EXTEND, expect
	get_iv_value to be in iv->mode rather than iv->extend_mode.
	(iv_extend): Likewise.  Otherwise, if iv->extend != extend,
	use lowpart_subreg on get_iv_value before calling simplify_gen_unary.
	* loop-unswitch.c (may_unswitch_on): Make sure op[i] is in the right
	mode.

	* gcc.c-torture/compile/pr58997.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@204413 138bc75d-0d04-0410-961f-82ee72b054a4