ifcvt: Punt if not onlyjump_p for find_if_case_{1,2} [PR104814]

ifcvt: Punt if not onlyjump_p for find_if_case_{1,2} [PR104814]

find_if_case_{1,2} implicitly assumes conditional jumps and rewrites them,
so if they have extra side-effects or are say asm goto, things don't work
well, either the side-effects are lost or we could ICE.
In particular, the testcase below on s390x has there a doloop instruction
that decrements a register in addition to testing it for non-zero and
conditionally jumping based on that.

The following patch fixes that by punting for !onlyjump_p case, i.e.
if there are side-effects in the jump instruction or it isn't a plain PC
setter.

Also, it assumes BB_END (test_bb) will be always non-NULL, because basic
blocks with 2 non-abnormal successor edges should always have some instruction
at the end that determines which edge to take.

2022-03-15  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/104814
	* ifcvt.cc (find_if_case_1, find_if_case_2): Punt if test_bb doesn't
	end with onlyjump_p.  Assume BB_END (test_bb) is always non-NULL.

	* gcc.c-torture/execute/pr104814.c: New test.