Re: [avr-libc-dev] Quick test of Björn Haase's relax patch

[Dmitry K.]

On Saturday 04 March 2006 20:23, you wrote:
> Björn and Dmitry,
> have you tried "program-at-once" compilation (avr-gcc -combine
> -fwhole-program *.c ..)? This may save some more bytes with recent gccs.

In result:

Options:                 rlx     cmb  cmb+rlx
---------------------------------------------
flash, bytes   11412   11056   11412   11104
call             198      24     198      46
rcall            143     316     143     294
jmp               34      10      34      14
rjmp             442     467     442     463

Where:
   rlx  is '--relax'
   cmb  is '-combine'
('-fwhole-program' is impossible to try a quick,
as the callback C functions called from asm are
broken --> unresolved links).

And another question about replacing '[r]call/ret' to
'[r]jmp/ret'. Whether this optimization is safe?
   For example, avr-libc: fplib.  Split function pops
two bytes from stack and returns into more high level
in error case. Similar tricks make such optimization
to be erroneous. On the other hand, the GCC x86 port
for a long time is able to optimize such tails. It also
does it more effectively as deletes not necessary
more 'ret'.
   Can be add an additional option for obvious inclusion
of this optimization?

Regards,
Dmitry.

P.S. In new fplib (preliminary patch to bug #1929) above
trick is not used.