This is a proposed API change in 946, which won't make it into this release.
The intent is to allow slightly larger constants to be specified in the updated
vkd3d_shader_parameter1 structure. In particular, this is large enough to pass
4-dimensional integer or float vectors inline, which the proposed clip plane
implementation will use, as well as other Direct3D FFP parameters.
We could also simply add vkd3d_shader_immediate_constant1 as a separate union
member in vkd3d_shader_parameter1, but this API is a bit cleaner and simpler.
As the newly added documentation describes, this reroll serves two purposes:
* to allow shader parameters to be used for any target type (which allows using
parameters for things like Direct3D 8-9 alpha test),
* to allow the union in struct vkd3d_shader_parameter to contain types larger
than 32 bits (by specifying them indirectly through a pointer).
An incoming can be undefined if the PHI result is not used if the
incoming's path was taken, or if the undefined value is consumed by
an instruction (dxc will compile such code without errors).
