Fix PR 110042: ifcvt regression due to paradoxical subregs

Fix PR 110042: ifcvt regression due to paradoxical subregs

After r14-1014-gc5df248509b489364c573e8, GCC started to emit
directly a zero_extract for `(t1&0x8)!=0`. This introduced
a small regression where ifcvt would not do the ifconversion
as there is now a paradoxical subreg in the dest which
was being rejected. Since paradoxical subreg set the whole
register, we can treat it as the same as a reg in the two places.

OK? Bootstrapped and tested on x86_64-linux-gnu and aarch64-linux-gnu.

gcc/ChangeLog:

	PR rtl-optimization/110042
	* ifcvt.cc (bbs_ok_for_cmove_arith): Allow paradoxical subregs.
	(bb_valid_for_noce_process_p): Strip the subreg for the SET_DEST.

gcc/testsuite/ChangeLog:

	PR rtl-optimization/110042
	* gcc.target/aarch64/csel_bfx_2.c: New test.