[Mlir-commits] [mlir] [mlir][vector] Add vector.transpose with unit-dim to vector.shape_cast pattern (PR #72105)

[Cullen Rhodes]

================
@@ -336,6 +336,27 @@ class TransposeOpLowering : public OpRewritePattern<vector::TransposeOp> {
       return rewriter.notifyMatchFailure(
           op, "Options specifies lowering to shuffle");
 
+    // Replace:
+    //   vector.transpose %0, [1, 0] : vector<nx1x<eltty>> to
+    //                                 vector<1xnxelty>
+    // with:
+    //   vector.shape_cast %0 : vector<nx1x<eltty>> to vector<1xnxelty>
+    //
+    // Source with leading unit dim (inverse) is also replaced. Unit dim must
+    // be fixed. Non-unit can be scalable.
+    if (resType.getRank() == 2 &&
+        ((resType.getShape().front() == 1 &&
+          !resType.getScalableDims().front()) ||
+         (resType.getShape().back() == 1 &&
----------------
c-rhodes wrote:

sorry I meant the inverse case, e.g.
```
%0 = vector.transpose %arg0, [1, 0] : vector<1x4xf32> to vector<4x1xf32>
->
%0 = vector.shape_cast %arg0 : vector<1x4xf32> to vector<4x1xf32>
```

https://github.com/llvm/llvm-project/pull/72105