In the DXIL CreateHandle and CreateHandleFromBinding ops, resource
bindings are
indexed from the beginning of the binding space, not from the binding
itself.
Translate from an index into the binding to one from the beginning of
the space
when lowering to these operations.
The `@llvm.dx.handle.fromBinding` intrinsic is lowered either to the
`CreateHandle` op or a pair of `CreateHandleFromBinding` and `AnnotateHandle`
ops, depending on the DXIL version. Regardless of the DXIL version we need to
emit metadata about the binding, but that's left to a separate change.
These DXIL ops all need to return the `%dx.types.Handle` type, but the llvm
intrinsic returns a target extension type. To facilitate changing the type of
the operation and all of its users, we introduce `%llvm.dx.cast.handle`, which
can cast between the two handle representations.
Pull Request: https://github.com/llvm/llvm-project/pull/104251
