Implement an abstraction to specify precise overload types supported by
DXIL ops. These overload types are typically a subset of LLVM
intrinsics.
Implement the corresponding changes in DXILEmitter backend.
Add tests to verify expected errors for unsupported overload types at
code generation time.
Add tests to check for correct overload error output.
* Leverage TableGen record descriptions of LLVM or DirectX intrinsics
that can be directly mapped in DXIL Ops TableGen description. As a
result, such DXIL Ops can be succinctly described without duplication.
DXILEmitter backend can derive the properties of DXIL Ops accordingly.
* Ensured that corresponding lit tests pass.
We have namespaces `DXIL` and `dxil`, which is just confusing. This
renames `DXIL` -> `dxil` making everything consistent.
While the LLVM coding standards don't have a clear direction here, I
chose lower case because by my current unscientific count there are
more places where we had the lowercase namespace than the uppercase.
A new helper class DXILOpBuilder is added to create DXIL op function calls.
TableGen backend for DXILOperation will create table for DXIL op function parameter types.
When create DXIL op function, these parameter types will used to create the function type.
Reviewed By: bogner
Differential Revision: https://reviews.llvm.org/D130291
