[Bug target/38629] target-specific parameters for inline heuristics not defined for AVR

[forwards dot from dot bugzilla at d81 dot de]

------- Comment #2 from forwards dot from dot bugzilla at d81 dot de  2008-12-26 21:29 -------
Steven, thanks for your explanation. My point of view was that gcc-4.3.3 did do
inlining code for "-Os", "-O1", "-O2" although the manual clearly states that
it would not do inlining for these optimization levels.

     "-O2 Optimize even more. GCC performs... The compiler does not perform
          loop unrolling or function inlining when you specify -O2..."

But for "-O/-O1" it is mentioned:
     "-O turns on the following optimization flags:
      ... -finline-small-functions ..."

So the manual is a little ambiguous in this point. So to tune the heuristics
for the AVR target, one needs to tell the compiler:
 1) what's a "small function"
 2) tell about the costs
 3) maybe do something more

Actually, in GCC-4.4, gcc/config/avr/avr.c, somebody did already some tuning as
it seems to me:

avr_override_options (void)
{
  const struct mcu_type_s *t;

  flag_delete_null_pointer_checks = 0;

  if (!PARAM_SET_P (PARAM_INLINE_CALL_COST))
    set_param_value ("inline-call-cost", 5);
    ....

I don't feel qualified enough to find well working values for all AVR
architectures since I do know the Attiny2313, Mega8 and Mega644 a little bit.
Maybe someone is willing to help me.


Wolfgang


PS: Steven, do you have got administrative rights to edit my initial post.
Could you please convert Till Harbaum's eMail address into something that
cannot be parsed by eMail harvesting robots ('@' -> "(at)").


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38629