[mlir][linalg] Fix for invalid IR in eliminate_empty_tensors (#73513)

The transform.structured.eliminate_empty_tensors can produce mis-typed
IR when traversing use-def chains past tensor reshaping operations for
sharing candidates. This results in Linalg operations whose output types
do not match their 'outs' arguments.

This patch filters out candidate tensor.empty operations when their
types do not match the candidate input operand.

mlir/lib/Dialect/Linalg/Transforms/EliminateEmptyTensors.cpp

@@ -60,7 +60,10 @@ LogicalResult linalg::linalgOpAnchoredEmptyTensorEliminationStep(
       config.alwaysIncludeLeaves = false;
       SetVector<Value> emptyTensors = state.findValueInReverseUseDefChain(
           in->get(), /*condition=*/
-          [&](Value val) { return val.getDefiningOp<tensor::EmptyOp>(); },
+          [&](Value val) {
+            return val.getDefiningOp<tensor::EmptyOp>() &&
+                   val.getType() == in->get().getType();
+          },
           config);
       if (emptyTensors.empty())
         continue;

mlir/test/Dialect/Linalg/one-shot-bufferize-empty-tensor-elimination.mlir

@@ -42,3 +42,89 @@ module attributes {transform.with_named_sequence} {
     transform.yield
   }
 }
+
+// -----
+
+#map = affine_map<(d0) -> (d0)>
+
+// This test is intended to check that the produced IR does not contain any
+// type errors from sharing empty tensor operations with different types.
+// The verifiers are sufficient to lock down the intended behavior.
+
+// CHECK-LABEL: func.func @collapse_shape_prevents_reuse(
+func.func @collapse_shape_prevents_reuse(%fill_value: f32) -> tensor<56xf32>
+{
+  %init0 = tensor.empty() : tensor<56xf32>
+  %init1 = tensor.empty() : tensor<56x1xf32>
+
+  %filled_tensor = linalg.fill
+    ins(%fill_value : f32)
+    outs(%init1 : tensor<56x1xf32>) -> tensor<56x1xf32>
+
+  // The collapse shape alters the tensor rank, so the %init1 tensor.empty cannot be
+  // pushed into the output of the linalg.generic.
+  %reshaped_tensor = tensor.collapse_shape %filled_tensor [[0, 1]]
+    : tensor<56x1xf32> into tensor<56xf32>
+
+  %bias = linalg.generic {
+    indexing_maps = [#map, #map],
+    iterator_types = ["parallel"]
+  } ins(%reshaped_tensor : tensor<56xf32>)
+    outs(%init0 : tensor<56xf32>) {
+    ^bb0(%in: f32, %out: f32):
+      linalg.yield %in : f32
+  } -> tensor<56xf32>
+
+  return %bias : tensor<56xf32>
+}
+
+module attributes {transform.with_named_sequence} {
+  transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
+    %0 = transform.structured.match ops{["func.func"]} in %arg1 : (!transform.any_op) -> !transform.any_op
+    transform.structured.eliminate_empty_tensors %0 : !transform.any_op
+    transform.yield
+  }
+}
+
+// -----
+
+#map = affine_map<(d0, d1) -> (d0, d1)>
+
+// This test is intended to check that the produced IR does not contain any
+// type errors from sharing empty tensor operations with different types.
+// The verifiers are sufficient to lock down the intended behavior.
+
+// CHECK-LABEL: func.func @collapse_cast_prevents_reuse(
+func.func @collapse_cast_prevents_reuse(%fill_value: f32) -> tensor<56x?xf32>
+{
+  %c1 = arith.constant 1 : index
+  %init0 = tensor.empty(%c1) : tensor<56x?xf32>
+  %init1 = tensor.empty() : tensor<56x1xf32>
+
+  %filled_tensor = linalg.fill
+    ins(%fill_value : f32)
+    outs(%init1 : tensor<56x1xf32>) -> tensor<56x1xf32>
+
+  // The cast alters the number of dynamic dims, so the %init1 tensor.empty cannot be
+  // pushed into the output of the linalg.generic.
+  %cast = tensor.cast %filled_tensor : tensor<56x1xf32> to tensor<56x?xf32>
+
+  %bias = linalg.generic {
+    indexing_maps = [#map, #map],
+    iterator_types = ["parallel", "parallel"]
+  } ins(%cast : tensor<56x?xf32>)
+    outs(%init0 : tensor<56x?xf32>) {
+    ^bb0(%in: f32, %out: f32):
+      linalg.yield %in : f32
+  } -> tensor<56x?xf32>
+
+  return %bias : tensor<56x?xf32>
+}
+
+module attributes {transform.with_named_sequence} {
+  transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
+    %0 = transform.structured.match ops{["func.func"]} in %arg1 : (!transform.any_op) -> !transform.any_op
+    transform.structured.eliminate_empty_tensors %0 : !transform.any_op
+    transform.yield
+  }
+}