[mlir][Linalg] Allow folding to rank-zero tensor when using rank-reducing subtensors.
The pattern to convert subtensor ops to their rank-reduced versions
(by dropping unit-dims in the result) can also convert to a zero-rank
tensor. Handle that case.
This also fixes a OOB access bug in the existing pattern for such
cases.
Differential Revision: https://reviews.llvm.org/D101949
diff --git a/mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp b/mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp
index 47f490c..9c4d8af 100644
--- a/mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp
+++ b/mlir/lib/Dialect/Linalg/Transforms/DropUnitDims.cpp
@@ -459,7 +459,10 @@
reassociation.emplace_back(ReassociationIndices{});
std::swap(reassociation.back(), curr);
}
- if (!curr.empty())
+ // When the reassociations are not empty, then fold the remaining
+ // unit-dimensions into the last dimension. If the reassociations so far is
+ // empty, then leave it emtpy. This will fold everything to a rank-0 tensor.
+ if (!curr.empty() && !reassociation.empty())
reassociation.back().append(curr.begin(), curr.end());
return reassociation;
}
diff --git a/mlir/test/Dialect/Linalg/drop-unit-extent-dims.mlir b/mlir/test/Dialect/Linalg/drop-unit-extent-dims.mlir
index 2b8855a..808622b 100644
--- a/mlir/test/Dialect/Linalg/drop-unit-extent-dims.mlir
+++ b/mlir/test/Dialect/Linalg/drop-unit-extent-dims.mlir
@@ -496,3 +496,27 @@
// CHECK-SAME: outs(%[[FILL]] : tensor<?xf32>)
// CHECK: %[[RESULT_RESHAPE:.+]] = linalg.tensor_reshape %[[RESULT]] {{\[}}[0, 1]]
// CHECK: return %[[RESULT_RESHAPE]]
+
+// -----
+
+func @subtensor_unit_dims(%arg0: tensor<1x3xf32>) -> tensor<1x1xf32> {
+ %0 = subtensor %arg0[0, 2] [1, 1] [1, 1] : tensor<1x3xf32> to tensor<1x1xf32>
+ return %0 : tensor<1x1xf32>
+}
+// CHECK-LABEL: func @subtensor_unit_dims
+// CHECK: %[[SUBTENSOR:.+]] = subtensor
+// CHECK-SAME: tensor<1x3xf32> to tensor<f32>
+// CHECK: %[[RESULT:.+]] = linalg.tensor_reshape %[[SUBTENSOR]] []
+// CHECK: return %[[RESULT]]
+
+// -----
+
+func @subtensor_insert_unit_dims(%arg0: tensor<1x3xf32>, %arg1: tensor<1x1xf32>) -> tensor<1x3xf32> {
+ %0 = subtensor_insert %arg1 into %arg0[0, 2] [1, 1] [1, 1] : tensor<1x1xf32> into tensor<1x3xf32>
+ return %0 : tensor<1x3xf32>
+}
+// CHECK-LABEL: func @subtensor_insert_unit_dims
+// CHECK: %[[RESHAPE:.+]] = linalg.tensor_reshape %{{.+}} []
+// CHECK: %[[RESULT:.+]] = subtensor_insert %[[RESHAPE]]
+// CHECK-SAME: tensor<f32> into tensor<1x3xf32>
+// CHECK: return %[[RESULT]]
