The host/device split flow already runs device-region annotation,
host/device function extraction, and device-kernel launch lowering as
one consecutive pipeline. Keeping those stages exposed as separate
public passes makes the API surface larger than the actual execution
model and leaves the stage dependencies spread across multiple files.
This change makes `tirx.transform.SplitHostDevice` the single public
entry point for that flow, while preserving the existing stage order
internally.
Changes:
- Merge the annotation, splitting, and kernel-launch lowering
implementations into `src/tirx/transform/split_host_device.cc` as
private sections.
- Remove the old public C++ declarations, FFI registrations, and Python
wrappers for `AnnotateDeviceRegions` and `LowerDeviceKernelLaunch`.
- Replace pipeline call sites that previously invoked the three-stage
sequence with one `SplitHostDevice()` call.
- Update TIRx and S-TIR tests to exercise the consolidated pass and the
reduced public API surface.
Tianqi Chen
dea2bf933e