Re: [avr-gcc-list] Weird optimization issue with avr-gcc 4.5.3, re "naked."

[Bill Westfield]

Oops.  I have been forgeting to make sure to cc the list.  And using the wrong 
from address as well...  So I'm going to dump some of the older messages; they 
may be a repeat for some of you.

On Jan 27, 2012, at 3:23 AM, Georg-Johann Lay wrote:

>> 4.5.3 ?  Whatever this issue is, it apparently snuck in between 4.5.2 and 
>> 4.5.3.
> 
> The only remarkable difference between 4.5.2 and 4.5.3 is the fix of PR42240.

That looks exactly relevant.

"The patch implements target hook TARGET_CANNOT_MODIFY_JUMPS_P in order
to inhibit post-reload bb reorder for naked functions."

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42240

It looks like the patch to prevent reordering of instructions past the epilogue 
of naked functions prevents such reordering for the entire naked function.

Though I'm not sure I understand why the original complaint was considered a 
bug. They appear to have been counting on a naked C function to fall in at the 
top and fall out at the bottom, which seems like even more of an abuse of 
"naked" than I was using (though I guess allowing that behavior is useful, 
especially in init code.)

Thanks!

BillW