Re: [patch] AVR: Tweak reg == const and reg != const compares if const = 0 mod 256

чт, 13 авг. 2026 г. в 22:03, Georg-Johann Lay <[email protected]>:
>
> This patch tweaks the EQ and NE comparison of a register against
> a const_int or const_fixed by one instruction in the case where
> the constant is 0 mod 256.  For example, take the comparison in
>
> _Accum cmp (_Accum x)
> {
>     if (x != 1.0k)
>        x += 2.0k;
>     return x;
> }
>
> which improves from
>
>     cpi r22,0
>     ldi r18,-128
>     cpc r23,r18
>     cpc r24,r22
>     cpc r25,r22
>
> to
>
>     cpi r23,-128
>     cpc r22,__zero_reg__
>     cpc r24,__zero_reg__
>     cpc r25,__zero_reg__
>
> One unsolved problem is that the latter sequence doesn't need
> a scratch reg but is still allocating one.
>
> Ok for trunk?

Ok. Please apply.
>
> p.s.: There are also some Binutils patches which seems to have sneaked
> past your attention:
> https://sourceware.org/pipermail/binutils/2026-July/149967.html
> https://sourceware.org/pipermail/binutils/2026-August/150739.html

You can apply both.

Denis.