[mlir][vector] Fix crash in vector.extract folder (#95912)

Fix a bug in the `vector.extract` folder when the vector type is 0-d.

Author: matthias-springer

mlir/lib/Dialect/Vector/IR/VectorOps.cpp

@@ -1883,7 +1883,10 @@ static Value foldExtractStridedOpFromInsertChain(ExtractOp extractOp) {
 }
 
 OpFoldResult ExtractOp::fold(FoldAdaptor) {
-  if (getNumIndices() == 0)
+  // Fold "vector.extract %v[] : vector<2x2xf32> from vector<2x2xf32>" to %v.
+  // Note: Do not fold "vector.extract %v[] : f32 from vector<f32>" (type
+  // mismatch).
+  if (getNumIndices() == 0 && getVector().getType() == getResult().getType())
     return getVector();
   if (succeeded(foldExtractOpFromExtractChain(*this)))
     return getResult();

mlir/test/Dialect/Vector/canonicalize.mlir

@@ -2593,3 +2593,14 @@ func.func @rank_1_shuffle_to_interleave(%arg0: vector<6xi32>, %arg1: vector<6xi3
   %0 = vector.shuffle %arg0, %arg1 [0, 6, 1, 7, 2, 8, 3, 9, 4, 10, 5, 11] : vector<6xi32>, vector<6xi32>
   return %0 : vector<12xi32>
 }
+
+// -----
+
+// CHECK-LABEL: func @extract_from_0d_regression(
+//  CHECK-SAME:     %[[v:.*]]: vector<f32>)
+//       CHECK:   %[[extract:.*]] = vector.extract %[[v]][] : f32 from vector<f32>
+//       CHECK:   return %[[extract]]
+func.func @extract_from_0d_regression(%v: vector<f32>) -> f32 {
+  %0 = vector.extract %v[] : f32 from vector<f32>
+  return %0 : f32
+}