Shuffle files around, use TableGen to register passes, and introduce
a `mlir-hlo-opt.cpp` file to hold the main entry point of the -opt tool
and stop relying on static registration for dialect/passes.
PiperOrigin-RevId: 323674455
The existing conversion no longer worked and was not save to undo. Furthermore, the pattern for mhlo.return had been removed.
Also adds some tests to ensure this does not degrade again.
PiperOrigin-RevId: 321542071
Following on the plan of isolating the compiler/mlir/hlo directory.
Another xla_lhlo dialect will be created under compiler/mlir/xla/ later.
PiperOrigin-RevId: 320210326