[all-commits] [llvm/llvm-project] febece: [mlir][memref] Reject empty collapse_shape and exp...

[Wijkqwe via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: febece38855bf752ebc4b8cbce5d56adab78d1aa
      https://github.com/llvm/llvm-project/commit/febece38855bf752ebc4b8cbce5d56adab78d1aa
  Author: Wijkqwe <188143146+Wijkqwe at users.noreply.github.com>
  Date:   2026-09-23 (Wed, 23 Sep 2026)

  Changed paths:
    M mlir/lib/Dialect/MemRef/IR/MemRefOps.cpp
    M mlir/test/Dialect/MemRef/invalid.mlir

  Log Message:
  -----------
  [mlir][memref] Reject empty collapse_shape and expand_shape reassociation groups (#225348)

`memref.collapse_shape` and `memref.expand_shape` both accept an empty
reassociation group, which is not a valid reassociation: every group
must be a
non-empty, contiguous segment of dimensions.

* `memref.collapse_shape` with an empty group aborts the compiler for a
  non-identity source layout. `CollapseShapeOp::verify` forwards the
reassociation to `computeCollapsedLayoutMap`, which calls
`ArrayRef::back()`
  on each group and asserts on the empty one:

      mlir-opt: llvm/include/llvm/ADT/ArrayRef.h:151:
      const T& llvm::ArrayRef<T>::back() const [with T = long int]:
      Assertion `!empty()' failed.

  With an identity source layout the op is instead silently accepted.

* `memref.expand_shape` with an empty group is silently accepted: the
empty
group maps a source dimension to no result dimension, so a real
dimension is
  dropped without any diagnostic.

The tensor reshape verifiers already reject this input
(https://github.com/llvm/llvm-project/pull/173791,
https://github.com/llvm/llvm-project/issues/222602 /
https://github.com/llvm/llvm-project/pull/222648).
Extract the empty-group check into a helper shared by both memref
verifiers,
mirroring https://github.com/llvm/llvm-project/pull/222648, and invoke
it from `ExpandShapeOp::verify` and
`CollapseShapeOp::verify`.

Add regression tests to `mlir/test/Dialect/MemRef/invalid.mlir`.

Assisted-by: AI.



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