[SPIR-V] Incorrect SPIR-V generated for `countbits` for non-32 bit type integers

[inbelic]

Description

Saw this error:

fatal error: generated SPIR-V is invalid: [VUID-StandaloneSpirv-Base-04781] Expected 32-bit int type for Base operand: BitCount
   %43 = OpBitCount %v4uint %42

when compiling this code:

StructuredBuffer<int16_t4> In : register(t0);
RWStructuredBuffer<uint4> Out : register(u2);

[numthreads(1,1,1)]
void main() {
  Out[0] = countbits(In[0]);
}

The same error occurs when using int64_t as well.

Steps to Reproduce https://godbolt.org/z/65fKP583e

Actual Behavior

From the validator specs, the validator doesn't allow OpBitCount to have non-32 bit integer types

Note: This is in contrast to the spir-v OpBitCount specification that denotes the Result and Base type can be a scalar or vector of integer type.

This will most likely require emulation of the non-32 bit types.

Environment DXC version 1.8.2403.2 Host Operating System N/A