[all-commits] [llvm/llvm-project] 6479a5: [mlir][vector] Restrict DropInnerMostUnitDimsTrans...

[Andrzej Warzyński via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6479a5a438a9545dd8f449be96d4024d0a08beba
      https://github.com/llvm/llvm-project/commit/6479a5a438a9545dd8f449be96d4024d0a08beba
  Author: Andrzej Warzyński <andrzej.warzynski at arm.com>
  Date:   2024-07-12 (Fri, 12 Jul 2024)

  Changed paths:
    M mlir/lib/Dialect/Vector/Transforms/VectorTransforms.cpp
    M mlir/test/Dialect/Vector/vector-transfer-collapse-inner-most-dims.mlir

  Log Message:
  -----------
  [mlir][vector] Restrict DropInnerMostUnitDimsTransfer{Read|Write} (#96218)

Restrict `DropInnerMostUnitDimsTransfer{Read|Write}` so that it fails
when one of the indices to be dropped could be != 0 and "out of bounds":

```mlir
func.func @negative_example(%arg0: memref<16x1xf32>, %arg1: vector<8x1xf32>, %idx_1: index, %idx_2: index) {
  vector.transfer_write %arg1, %arg0[%idx_1, %idx_2] {in_bounds = [true, false]} : vector<8x1xf32>, memref<16x1xf32>
  return
}
```

This is an edge case that could represent an out-of-bounds access,
though that will depend on the actual value of %i. Importantly, without
this change it would be transformed as follows:

```mlir
func.func @negative_example(%arg0: memref<16x1xf32>, %arg1: vector<8x1xf32>, %arg2: index, %arg3: index) {
  %subview = memref.subview %arg0[0, 0] [16, 1] [1, 1] : memref<16x1xf32> to memref<16xf32, strided<[1]>>
  %0 = vector.shape_cast %arg1 : vector<8x1xf32> to vector<8xf32>
  vector.transfer_write %0, %subview[%arg2] {in_bounds = [true]} : vector<8xf32>, memref<16xf32, strided<[1]>>
  return
}
```

This is incorrect - `%idx_2` is ignored and the "out of bounds" flags is
not propagated. Hence the extra restriction to avoid such cases.

NOTE: This is a follow-up for: #94904



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