[avr-libc-dev] [bug #12739] Gcc assumes that target libc provides ffs function

[anonymous]

Follow-up Comment #3, bug #12739 (project avr-libc):

I've had a look at your functions.

Very good! Most interesting for me has been that there is this
__builtin_constant_p () function! Very useful! 
Did not know that beforehand.

Suggestion from my side concerning the implementation is:

I'd try to make the function as efficient as a *real* builtin function of gcc
by defining 

char ffs inline (int param)
{ 
  inline asm stating in which registers to pass parameters
  and which registers are actually clobbered.
}

Possibly this way one could also remove things like the 
"clr r25" for the zero-extension that possibly is not necessary.

I'll think about that and send a more detailed suggestion.

Yours,

Björn

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