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

[Giovanni Mascellani (＠giomasce)]

Giovanni Mascellani (@giomasce) commented about libs/vkd3d-shader/hlsl_constant_ops.c:
> -
> - for (k = 0; k < 4; ++k)
> - {
> -
>    switch (type)
> -
>    {
> -
>        case HLSL_TYPE_FLOAT:
> -
>        case HLSL_TYPE_HALF:
> -
>            dst->value.u[k].f = fabsf(src->value.u[k].f);
> -
>            break;
> -
> -
>        case HLSL_TYPE_DOUBLE:
> -
>            dst->value.u[k].d = fabs(src->value.u[k].d);
> -
>            break;
> -
> -
>        case HLSL_TYPE_INT:
> -
>            dst->value.u[k].i = abs(src->value.u[k].i);

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()`.