tqchen opened a new pull request, #20062:
URL: https://github.com/apache/tvm/pull/20062
This refactors TIRx buffers into ordinary `ir.Var` identities carrying an
immutable `BufferType`.
## Rationale
The old representation kept a standalone Buffer object, its logical metadata,
and a separate pointer-typed data Var. Generic Var substitution and
buffer-specific rebuilding could therefore let identity, metadata, and
pointer
type drift apart. In this change, `BufferType` is the single source of the
logical contract and `buffer_data(buffer)` is the explicit physical-pointer
projection; `DeclBuffer` records a view's binding.
## Simplification
- Generic Var scoping, substitution, undefined-variable analysis, and
identity
maps now apply directly to buffers.
- The pointer type is derived from `BufferType`, so the physical pointer and
buffer metadata cannot disagree.
- The common IR path no longer needs a second Buffer object, duplicate
constructor state, or a parallel buffer-only substitution mechanism.
- Metadata-changing transforms create a fresh typed Var and bind it
explicitly
at the replacing `AllocBuffer` or `DeclBuffer`.
Physical-root tracking remains deliberately local to the passes whose
correctness depends on allocation ownership:
1. Storage liveness/reuse attributes alias accesses to the owning allocation.
2. Pointer vector-type inference and rewriting aggregate evidence at that
root.
3. LowerTIRx cleanup projects aliases to the remapped physical allocation.
4. Thread-allreduce's deferred remapper replaces/removes the owning
allocation.
Each is a plain pass-local `Map<Var, Var>` flattened when a `DeclBuffer` is
visited. Parameters, `buffer_map`, and `AllocBuffer` seed roots; an alias
to an
unseen typed source is rejected rather than silently treated as a new root.
Simpler passes decode the one-step `buffer_data` projection locally.
## Migration guide
### C++
- Treat `BufferVar` as a checked view over an ordinary `Var`.
- Read logical metadata through `buffer->...`; use `buffer.var()` for
identity.
- Use `buffer.data()` or `builtin::buffer_data()` only when a physical
pointer
expression is required.
- To change metadata, rebuild `BufferType`, create a fresh Var, and bind it
at
the replacement definition site.
- A transformed `DeclBuffer` replaces its superseded declaration
consistently;
it must not leave a stale declaration beside the new binding.
### Python
- Buffer constructors return `tvm.ir.Var`; `.ty` contains `BufferType`.
- Use `tvm.tirx.is_buffer_var(value)` for runtime discrimination.
- `tvm.tirx.Buffer` remains an import/annotation compatibility alias for
`tvm.ir.Var`, so `isinstance(value, Buffer)` matches every Var.
- Importing `tvm.tirx` installs the legacy metadata properties on Var.
Non-buffer Vars raise `AttributeError`; buffer `.dtype` keeps its
historical
`DataType` result.
## Behavior-preserving follow-up
The second commit restores the original LowerTIRx, FlattenBuffer, and BF16
outputs; restores the alias-lifetime regression; replaces superseded
declarations; keeps ownership logic pass-local; and fixes tagged
shared-memory
children after their parent allocation is rebuilt.
## Validation
- C++ build (`USE_LLVM=OFF`): passed.
- Focused matrix: **239 passed, 3 skipped**.
- Complete unfiltered TIRx/S-TIR Python run:
**62 failed, 2248 passed, 1668 skipped, 11 xfailed, 1 xpassed,
1 warning, 10 collection errors** in 290.09s.
- The broad run exposed 12 genuine Python dtype-compatibility failures; those
were fixed and rerun green. The remaining failures and collection errors
require LLVM/target globals, CUDA, NKI, Torch, or
target-feature/target-build
support unavailable on this node.
- `git diff --check`: passed.
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