[MLIR][Linalg] improve silenceable failure msg for lower_pack (NFC)

Adjust the silenceable failure message as we lower `tensor.unpack` as a
combination of `linalg.transpose` + `tensor.collapse_shape` and
`tensor.extract_slice`.

Author: chelini

mlir/lib/Dialect/Linalg/TransformOps/LinalgTransformOps.cpp

@@ -1125,8 +1125,11 @@ DiagnosedSilenceableFailure transform::LowerUnPackOp::applyToOne(
   rewriter.setInsertionPoint(target);
   FailureOr<LowerUnPackOpResult> res = lowerUnPack(rewriter, target);
   if (failed(res)) {
-    return mlir::emitSilenceableFailure(target->getLoc())
-           << "cannot rewrite to pad + expand + transpose";
+    DiagnosedSilenceableFailure diag =
+        emitSilenceableError()
+        << "cannot lower to transpose + collapse + extract";
+    diag.attachNote(target->getLoc()) << "target payload op";
+    return diag;
   }
   transformResults.push_back(res->emptyOp);
   transformResults.push_back(res->transposeOp);

mlir/test/Dialect/Linalg/transform-lower-pack.mlir

@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s -transform-interpreter -cse --split-input-file | FileCheck %s
+// RUN: mlir-opt %s -transform-interpreter -cse -verify-diagnostics -split-input-file | FileCheck %s
 
   // CHECK-LABEL: func.func @pack(
 func.func @pack(%arg0: tensor<129x47x16x16xf32>, %arg1: tensor<17x2x16x16x32x8xf32>) -> tensor<17x2x16x16x32x8xf32> {
@@ -143,9 +143,9 @@ func.func @unpack(%arg0: tensor<17x2x16x16x32x8xf32>, %arg1: tensor<129x47x16x16
   // CHECK-SAME:   : tensor<136x64x16x16xf32> to tensor<129x47x16x16xf32>
   //      CHECK: linalg.copy ins(%[[SLICE]] : tensor<129x47x16x16xf32>)
   // CHECK-SAME:        outs(%[[ARG1]] : tensor<129x47x16x16xf32>)
-  %pack = tensor.unpack %arg0 inner_dims_pos = [1, 0] inner_tiles = [32, 8] into %arg1
+  %unpack = tensor.unpack %arg0 inner_dims_pos = [1, 0] inner_tiles = [32, 8] into %arg1
     : tensor<17x2x16x16x32x8xf32> -> tensor<129x47x16x16xf32>
-  return %pack : tensor<129x47x16x16xf32>
+  return %unpack : tensor<129x47x16x16xf32>
 }
 
 module attributes {transform.with_named_sequence} {
@@ -162,6 +162,7 @@ module attributes {transform.with_named_sequence} {
 }
 
 // -----
+
 // When an unpack is a plain 'unpad', lower it to a simple extract_slice.
 // CHECK-LABEL: func.func @unpack_as_pad(
 func.func @unpack_as_pad(%arg0: tensor<1x1x1x1x136x64x16x16xf32>, %arg1: tensor<129x47x16x16xf32>) -> tensor<129x47x16x16xf32> {
@@ -460,3 +461,27 @@ module attributes {transform.with_named_sequence} {
           transform.yield
   }
 }
+
+// -----
+
+// At the moment, we cannot lower tensor.unpack with outer_dims_perm.
+func.func @diagnostic_unpack(%arg0: tensor<32x64xf32>, %arg1: tensor<2x4x32x8xf32>) -> tensor<32x64xf32> {
+  // expected-note @below {{target payload op}}
+  %unpack = tensor.unpack %arg1 outer_dims_perm = [1, 0] 
+    inner_dims_pos = [1, 0] inner_tiles = [32, 8] into %arg0 : tensor<2x4x32x8xf32> -> tensor<32x64xf32>
+  return %unpack : tensor<32x64xf32>
+}
+
+module attributes {transform.with_named_sequence} {
+  transform.named_sequence @__transform_main(%module_op: !transform.any_op {transform.readonly}) {
+    %unpack = transform.structured.match ops{["tensor.unpack"]} in %module_op
+      : (!transform.any_op) -> !transform.op<"tensor.unpack">
+    // expected-error @below {{cannot lower to transpose + collapse + extract}} 
+    transform.structured.lower_unpack %unpack : (!transform.op<"tensor.unpack">)
+      -> (!transform.op<"tensor.empty">,
+          !transform.op<"linalg.transpose">,
+          !transform.op<"tensor.collapse_shape">,
+          !transform.op<"tensor.extract_slice">)
+          transform.yield
+  }
+}