Bitfields dependant on templates don't realize they're supposed to be one field

[devshgraphicsprogramming]

Description

The following struct

template<typename T, uint32_t OutputBits>
struct result_t
{
    static result_t invalid()
    {
        result_t retval;
        retval.exclusivePrefixSum = retval.outputIndex = ~0u;
        return retval;
    }

    T outputIndex : OutputBits;
    T exclusivePrefixSum : (sizeof(T)*8-OutputBits);
};

Steps to Reproduce

SPIR-V
https://godbolt.org/z/GTc3do6od

Its not a BDA only issue, for interpolants it also gets confused
https://godbolt.org/z/KK1G8czqq

I think the DXIL codegen is also wrong
https://godbolt.org/z/cPohsxvYa

Actual Behavior

The codegen results in

%result_t = OpTypeStruct %uint %uint

for the function definition, and

OpCompositeExtract %uint %20 1

for the access on exclusivePrefixSum.

The codegen treats the two bitfields as separate values.

The DXIL is also wrong

  %1 = call i32 @dx.op.loadInput.i32(i32 4, i32 1, i32 0, i8 0, i32 undef), !dbg !58
  %2 = call i32 @dx.op.loadInput.i32(i32 4, i32 0, i32 0, i8 0, i32 undef), !dbg !58

Declaring the struct as

    T outputIndex : 7;
    T exclusivePrefixSum : (32-7);

doesn't introduce this issue.

Environment

• DXC version
• Host Operating System <!--- Host operating system and version --->

[devshgraphicsprogramming]

SpIR-V tag should be removed