PR60580: Fix frame pointer option magic

PR60580: Fix frame pointer option magic

To fix PR60580 simplify the logic in aarch64_override_options_after_change_1 ().
If the frame pointer is enabled, set it to a special value that behaves similar
to frame pointer omission.  If we don't do this all leaf functions will get a
frame pointer even if flag_omit_leaf_frame_pointer is set.

If flag_omit_frame_pointer has this special value, we must force the frame
pointer if not in a leaf function.  We also need to force it in a leaf function
if flag_omit_frame_pointer is not set or if LR is used.

Doing this allows both -fomit-frame-pointer and -fomit-leaf-frame-pointer to be
independently set and changed in each function with the expected behaviour.

    gcc/
	PR middle-end/60580
	* config/aarch64/aarch64.c (aarch64_frame_pointer_required)
	Check special value of flag_omit_frame_pointer.
	(aarch64_can_eliminate): Likewise.
	(aarch64_override_options_after_change_1): Simplify handling of
	-fomit-frame-pointer and -fomit-leaf-frame-pointer.

From-SVN: r254052