[PATCH vkd3d v8 2/4] vkd3d-shader/hlsl: Handle conditionals in copy propagation.

[Matteo Bruni]

On Tue, Nov 30, 2021 at 7:10 PM Zebediah Figura <zfigura at codeweavers.com> wrote:
>
> So this is failing to optimize the following program, and I can't see why:
>
> uniform int i;
>
> float main() : sv_target
> {
>      float x = 0;
>      if (0){}
>      return x;
> }
>
> It generates the following code:
>
>   2:      float | 0.00000000e+00
>   3:            | = (x.x @2)
>   4:        int | 0
>   5:            | if (@4) {
>                   } else {
>                   }
>   6:      float | x
>   7:            | = (<retval-0x5620633a6280>.x @6)
>   8:            | return
>   9:       uint | 0
> 10:      float | <retval-0x5620633a6280>[@9]
> 11:            | = (<output-sv_target0>.x @10)
>
> I'd expect @6 to be rewritten to @2.x, but that doesn't happen. Do you
> know why?

Good catch. It's caused by the return in the HLSL_IR_IF case in
copy_propagation_transform_block(), we want to turn that to a break.
I'll make that change, among others, before resending.