[TIRx] Post-bringup follow-ups: op-dispatch, namespaces, launch bounds, gemm-async, backend reorg

[spectrometerHBH]

This PR batches several post-bringup TIRx follow-ups, rebased onto current main.

Changes

• op-dispatch: per-call exec scope via Tx.<scope>.op; remove ExecScopeStmt
• namespaces: split TIRx op namespaces; remove tile-primitive kind attrs
• codegen: support explicit CUDA launch bounds
• gemm-async: support contiguous-axis (K-major) operand slicing
• backend reorg: move in-tree GPU backends out of core into src/backend/<target>/ and python/tvm/backend/<target>/ (codegen/runtime/op), with the corresponding CMakeLists.txt / cmake/modules and include-path updates

Testing

• Builds with USE_CUDA=ON / USE_LLVM=ON
• The TIRx Python test suite (tests/python/tirx/) passes locally

[gemini-code-assist]

Code Review

This pull request restructures the TVM repository by moving target-specific backend codegen and runtime sources (such as CUDA, Hexagon, Metal, OpenCL, ROCm, Vulkan, and WebGPU) from src/target and src/runtime into a unified src/backend directory structure. It also reorganizes the corresponding Python bindings under python/tvm/backend and introduces a dynamic backend loading mechanism. The review feedback highlights a few critical issues: a missing analyzer variable instantiation in tcgen05.py that will cause a NameError at runtime, a bug in SMEMPool.commit where attr_frame.add_callback is incorrectly called on attr_frame itself instead of the parent frame (potentially causing a frame leak or deadlock), and an improvement opportunity in _AliasModule to override __setattr__ and __delattr__ to properly forward writes and deletes to the underlying aliased module.

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[gemini-code-assist]

The analyzer variable is used on line 614 but is not defined within the scope of compute_canonical_params, which will raise a NameError at runtime. Please instantiate analyzer = Analyzer() at the beginning of the function.

Suggested change

	region = list(buf_region.region)
	region = list(buf_region.region)
	analyzer = Analyzer()

[gemini-code-assist]

In SMEMPool.commit, attr_frame.add_callback is called on attr_frame itself before it is entered. Since attr_frame is never exited manually, its callbacks are never run, leading to a frame leak/deadlock. It should be added to parent_frame instead.

Suggested change

	if isinstance(attr_frame, frame_mod.AttrFrame):
	from functools import partial
	attr_frame.add_callback(partial(attr_frame.__exit__, None, None, None))
	attr_frame.__enter__()
	if isinstance(attr_frame, frame_mod.AttrFrame):
	from functools import partial
	parent_frame = frame_mod.current()
	parent_frame.add_callback(partial(attr_frame.__exit__, None, None, None))
	attr_frame.__enter__()

[gemini-code-assist]

_AliasModule does not override __setattr__ and __delattr__, which causes attributes set on the aliased module to not be reflected in the underlying module. Please override them to forward writes and deletes to the underlying module.

    def __getattr__(self, name: str):
        return getattr(self.__dict__["__tvm_backend_module__"], name)

    def __setattr__(self, name: str, value: Any):
        if name in ("__tvm_backend_module__", "__package__", "__all__", "__path__"):
            super().__setattr__(name, value)
        else:
            setattr(self.__dict__["__tvm_backend_module__"], name, value)

    def __delattr__(self, name: str):
        if name in ("__tvm_backend_module__", "__package__", "__all__", "__path__"):
            super().__delattr__(name)
        else:
            delattr(self.__dict__["__tvm_backend_module__"], name)

    def __dir__(self):
        return sorted(set(super().__dir__()) | set(dir(self.__dict__["__tvm_backend_module__"])))"