[RS6000] Allow saving of fixed regs.

[RS6000] Allow saving of fixed regs.

As I noted a long time ago in the comment on fixed_reg_p, the real
problem with saving fixed/global regs is that exception frame
unwinding might restore them.  So don't emit eh_frame info for any
such reg, and the unwinder won't restore them.

Also, tidy rs6000_savres_strategy.  Delaying some checks means we
won't iterate over regs quite so often.

	* config/rs6000/rs6000.c (rs6000_savres_strategy): Force inline
	restoring when fixed_reg_p, but allow out-of-line or stmw save.
	Check for user regs later to avoid unnecessary looping over regs.
	Merge user reg check with non-saved reg check.  Don't force
	inline VR restore when static chain used.
	(rs6000_frame_related): Omit eh_frame info for user regs when
	saving.
	(fixed_regs_p): Delete.

From-SVN: r235672