Update TableGen specification of DXIL Op records in DXIL.td per the
current design document.
- Facilitate specification of overloads, shader stage and attributes
predicated on DXIL Ops predicated DXIL version.
Implement functionality to consume in TableGen backend, DXILEmitter, the
above specification enhancements, and generate C++ code (in
(DXILOperations.inc) that represents properties of DXIL Ops, associated
type declarations and corresponding accessor functions.
Changes to DXIL Op Lowering pass to consume the DXIL Op representation
generated by the TableGen back end.
Add mtriple with the required shader model version to commandline of
tests.
