regcprop: Avoid REG_CFA_REGISTER notes (PR85645)

regcprop: Avoid REG_CFA_REGISTER notes (PR85645)

Changing a SET that has a REG_CFA_REGISTER note is wrong if we are
changing the SET_DEST, or if the REG_CFA_REGISTER has nil as its
argument, and maybe some other cases.  It's never really useful to
propagate into such an instruction, so let's just bail whenever we
see such a note.

	PR rtl-optimization/85645
	*  regcprop.c (copyprop_hardreg_forward_1): Don't propagate into an
	insn that has a REG_CFA_REGISTER note.

From-SVN: r260074