[all-commits] [llvm/llvm-project] d1fc59: [mlir][ArmSME] Rewrite illegal `shape_casts` to `v...

[Benjamin Maxwell via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d1fc59c3b5c5ce292a6060d7a5545094cdf1b5fc
      https://github.com/llvm/llvm-project/commit/d1fc59c3b5c5ce292a6060d7a5545094cdf1b5fc
  Author: Benjamin Maxwell <benjamin.maxwell at arm.com>
  Date:   2024-03-07 (Thu, 07 Mar 2024)

  Changed paths:
    M mlir/lib/Dialect/ArmSME/Transforms/VectorLegalization.cpp
    M mlir/test/Dialect/ArmSME/vector-legalization.mlir

  Log Message:
  -----------
  [mlir][ArmSME] Rewrite illegal `shape_casts` to `vector.transpose` ops (#82985)

This adds a rewrite that converts illegal 2D unit-dim `shape_casts` into
`vector.transpose` ops.

E.g.

```mlir
// Case 1:
%a = vector.shape_cast %0 : vector<[4]x1xf32> to vector<1x[4]xf32>
// Case 2:
%b = vector.shape_cast %1 : vector<[4]x1xf32> to vector<[4]xf32>
```

Becomes:

```mlir
// Case 1:
%a = vector.transpose %0 : [1, 0] vector<[4]x1xf32> to vector<1x[4]xf32>
// Case 2:
%t = vector.transpose %1 : [1, 0] vector<[4]x1xf32> to vector<1x[4]xf32>
%b = vector.shape_cast %t : vector<1x[4]xf32> to vector<[4]xf32>
```

Various lowerings and drop unit-dims patterns add such shape_casts,
however, if they do not cancel out (which they likely won't if we've
reached the vector-legalization pass) they will prevent lowering the IR.

Rewriting them as a transpose gives `LiftIllegalVectorTransposeToMemory`
a chance to eliminate the illegal types.



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications