[PATCH vkd3d 02/17] vkd3d-shader/hlsl: Handle branches in copy propagation.

[Giovanni Mascellani]

Hi,

On 01/12/21 17:14, Matteo Bruni wrote:
> changelog: Continue copy propagation after encountering an IF, rework to
> store the copy_propagation_state structs on the stack and search
> recursively

I still don't like these changes, they make the code more complicated 
than it should be, but I'll live with them.

However, I think you're introducing some missed optimizations with this 
specific patch. For example, take this code:

float2 a;
a.x = 1.0;
if (condition)
{
     a.y = 2.0;
     do_something(a.x);
}

You would expect a.x replaced with 1.0 in do_something(), but I don't 
think that's happening in you implementation: inside the conditional a 
new copy_propagation_var_def is created for variable a, which masks the 
previous knowledge about a.x being 1.0. This can probably be fixed in 
copy_propagation_create_var_def in the missing entry case by first doing 
a lookup on the lower frames and using that result, if it exists, to 
initialize the new copy_propagation_var_def.

Giovanni.