I saw this problem in C, then I tried on GDC and have the same problem:

int main() {
   for (uint a = 0, b = 0; a < 6; a += 1, b += 2){
        if (b < a){
            return 1;
        }
   }
   return 0;
}

The code above generates the wrong code when using: -O1, -O2 or -O3:

_Dmain:
        mov     eax, 1
        ret

Changing "uint" to "int" will that, or initializing with both "a" and "b" with a different value like "1" instead of "0" will work in -01, but will keep failing for -02 or -03.

Finally initializing with negative number will work for all 3 optimization level.

Matheus.

On Saturday, 9 October 2021 at 14:52:47 UTC, Matheus wrote:
> I saw this problem in C, then I tried on GDC and have the same problem:
>
> int main() {
>    for (uint a = 0, b = 0; a < 6; a += 1, b += 2){
>         if (b < a){
>             return 1;
>         }
>    }
>    return 0;
> }
>
> The code above generates the wrong code when using: -O1, -O2 or -O3:
>
> _Dmain:
>         mov     eax, 1
>         ret
>
> Changing "uint" to "int" will that, or initializing with both "a" and "b" with a different value like "1" instead of "0" will work in -01, but will keep failing for -02 or -03.
>
> Finally initializing with negative number will work for all 3 optimization level.
>

Nothing I can really do about that, it's occurring outside of the D front-end.

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100740