Re: [avr-gcc-list] Speeding [u]ltoa by 35%

[Georg-Johann Lay]

Georg-Johann Lay schrieb:
> Reviewing the ltoa sources [0] shows that the implementation's
> speed is not award winning: it uses 32-bit div+mod.
>
> There was propose [1] to speed ltoa by means of LUT but that
> approach tries to use lookup tables for special radices.
>
> The new proposal inlines __divmodsi4 leading to an ~35% tick gain
> without increasing code size: [...]

With 5 more instructions an even more impressive speed gain of
40%..50% or even more can be worked out:

http://sourceforge.net/apps/mediawiki/mobilechessboar/nfs/project/m/mo/mobilechessboar/a/aa/Ltoa2.png

Plot is for the same 364 sample values as

> [2] Plot:
> http://sourceforge.net/apps/mediawiki/mobilechessboar/nfs/project/m/mo/mobilechessboar/4/48/Ltoa.png 
>
> [3] Plot Description
> http://sourceforge.net/apps/mediawiki/mobilechessboar/index.php?title=File:Ltoa.png#Description