Re: [PATCH v2 0/1] MR203: vkd3d-shader/hlsl: Fold constant integral abs().

[Ethan Lee (＠flibitijibibo)]

On Tue May  9 10:35:56 2023 +0000, Giovanni Mascellani wrote:
> This is undefined behavior on `INT_MIN`.
> Actually, this case is somewhat interesting, because `lower_int_abs()`
> runs before constant expression folding, and should get rid of all `int`
> absolute values. So in principle we could stick `vkd3d_unreachable()`
> here. However `lower_int_abs()` does not run when doing constant folding
> from `evaluate_static_expression_as_uint()`, so this is still reachable.
> I'm not sure of what the others think, but I think I would be in favor
> to stipulating that this is unreachable and add other passes to `evaluate_static_expression_as_uint()`.

I could see this getting hit again if fold_exprs got used elsewhere - if we can't fold abs(INT_MIN), would it make sense to leave the expression untouched and let the runtime deal with it instead? I can add a quick

```
/* abs(INT_MIN) is undefined, leave this expression alone */
if (src->value.u[k].i == INT_MIN)
    return false;
```

if so.