[SER] Const correctness with HitObjects and payload

[Hengoo]

Description

You can write code that modifies const HitObject and const payload.
I would expect to get a compiler error instead.

Steps to Reproduce

RaytracingAccelerationStructure     gScene      : register(t0, space0); // acceleration structure
RWBuffer<float>                     output      : register(u0, space0);

struct [raypayload] Payload {
    float value : write(caller, closesthit, miss) : read(caller, closesthit, miss);
};

[shader("raygeneration")]
void BasicRayGen()
{
    RayDesc rayInit;
    rayInit.TMin = 0;
    rayInit.TMax = 1;
    rayInit.Origin = float3(1, 1, 1);
    rayInit.Direction = float3(1, 1, 1);
    const RayDesc ray = rayInit;
    Payload pInit;
    pInit.value = 0.0;
    const Payload p = pInit;
    // Anyhit shader could modify payload
    const dx::HitObject obj = dx::HitObject::TraceRay(gScene, 0, 0xff, 0, 0, 0, ray, p);
    // this modifies obj
    obj.SetShaderTableIndex(42);
    // Invoked shader could modifiy payload
    dx::HitObject::Invoke(obj, p);
    output[0] = p.value;
}

-T lib_6_9

See https://godbolt.org/z/fexT48588

Actual Behavior

This compiles without any issues / warning.

Environment

• DXC version: dxcompiler.dll: 1.9 - 1.8.2505.32 (b106a96); dxil.dll: 1.9(1.8.2505.32)

[Hengoo]

Sorry, spirv label was not intended, but I think I cannot remove it anymore

[damyanp]

@simoll - can you have first look at this one as well please?

[simoll]

@damyanp yup

[simoll]

There is two issues at play here:

1. Sema does not reject HLSL that feeds const values into [in]out params declared in gen_intrin_main.txt
   -> const payloads should be rejected during Sema as their Invoke param is declared inout. Fixable in Sema with additional diagnosis.
2. SetShaderTableIndex modifies the object but Sema does not validate that the object is mutable.. would need a new intrinsic attribute (eg const in gen_intrin_main.txt) and Sema validation.

[V-FEXrt]

The PR up for #7761 also resolves this issue.

bug3.hlsl:21:31: error: no matching function for call to 'TraceRay'
    const dx::HitObject obj = dx::HitObject::TraceRay(gScene, 0, 0xff, 0, 0, 0, ray, p);
                              ^~~~~~~~~~~~~~~~~~~~~~~
bug3.hlsl:25:5: error: no matching function for call to 'Invoke'
    dx::HitObject::Invoke(obj, p);