>> Perhaps the two different reduction-mod-5 schemes should depend on
>> OPTIMIZE_SPEED?
> Doesn't really matter much. Since the library is pre-compiled, you
> cannot map it to the user's -Ox compiler option anyway.
Er... AFAICT, that option has nothing to do with -O compiler
flags, but is set as part of library compilation.
I assumed it was set based on the amount of flash on the target
processor. 4K flash? Turn off. 128K flash? Turn on. 32K
flash? Not sure.
> As Johann already explained, most AVR users care for saved flash
> and RAM more than for saving a few CPU cycles.
RAM, I understand, but flash is either "enough" or "not enough", and if
you have enough, spending a few bytes of it for speed isn't a horrible
thing.
To quote libc/string/memcpy.S:
#if OPTIMIZE_SPEED
; 15 words, (14 + len * 6 - (len & 1)) cycles
(Unrolled code, copies 2 bytes per loop iteration)
#else
; 11 words, (13 + len * 8) cycles
(Rolled code)
#endif
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