How to ensure ParameterBlock is assigned descriptor set 0 when passed as entry-point parameter

[sjb3d]

Hi, it seems that changing a parameter block from being global to being passed as an argument to the entry-point changes its binding from set 0 to set 1. Since there are no other bindings this seems like unexpected behaviour, but I am not sure, so I thought I would ask as a question here.

I used the following shader to reproduce this with the latest release (v2024.1.2):

struct Params {
    Sampler2D<float4> tex;
}

ParameterBlock<Params> params;

[shader("pixel")]
float4 main(float2 uv)
{
    return params.tex.Sample(uv);
}

Compiled with slangc repro.slang -o test.glsl -entry main this produces the expected binding (implicitly in set 0) in its output:

layout(binding = 0)
uniform sampler2D params_tex_0;

If I change the shader to avoid declaring the parameter block globally:

struct Params {
    Sampler2D<float4> tex;
}

[shader("pixel")]
float4 main(float2 uv, ParameterBlock<Params> params)
{
    return params.tex.Sample(uv);
}

Then the binding in the output changes to descriptor set 1:

layout(binding = 0, set = 1)
uniform sampler2D entryPointParams_params_tex_0;

My question is: is this expected behaviour? It would be useful to pass parameters blocks via the entry-point for files that contain multiple entry-points, but I would have expected these two cases to generate the same bindings.

(Interestingly if I just use the Sampler2D type directly, without wrapping in a parameter block, then globals and entry-point parameters do behave the same way and put the binding in set 0 for both cases.)

[sjb3d]

Resolved on issue #3829. (The two cases should now behave the same way and allocate set 0.)