bit_cast template

[llvm-beanz]

Is your feature request related to a problem? Please describe.
HLSL has a bunch of different casting builtins that are all spelled differently and not templated. That makes it difficult for template code to cast to the appropriate type if the type is a template parameter.

Describe the solution you'd like
It would be awesome to add a templated bit_cast operation. Such a casting operation was added as an implementation detail in:

llvm/llvm-project#107292

I suspect we could create a similar header-implemented interface for DXC as well using type traits.

[devshgraphicsprogramming]

OUr implementations https://github.com/Devsh-Graphics-Programming/Nabla/blob/edd7e6242a3f07bbed957cb9d7b8778c547037be/include/nbl/builtin/hlsl/bit.hlsl#L34

[damyanp]

(related to internal 30312655)

[devshgraphicsprogramming]

btw since then we've learned that SPIR-V is a bit "special" and you can't bit-cast everything, only between fundametal types (scalar, vector, matrix) and sometimes Physical Pointer and uint64_t.

One would need some special memcpy for this otherwise.