[mlir][linalg] Fix canonicalizer crash for `linalg.generic` with mixed semantics

[Hardcode84]

Summary

EraseIdentityGenericOp for !hasBufferSemantics() assumed fully tensor semantics and tried to access non-existent return values.

mlir/lib/Dialect/Linalg/IR/LinalgOps.cpp

if (genericOp.hasBufferSemantics()) {
           genericOp.getInputOperand(0)->get() ==
               genericOp.getOutputOperand(0)->get()) {
         rewriter.eraseOp(genericOp);
         return success();
       }
       return failure();
     }
 
+    // Mixed semantics is not supported yet.
+    if (!genericOp.hasTensorSemantics())
+      return failure();
+
     // Get the argument number of the returned values. That is the operand
     // number to use for replacing uses of this operation.
     SmallVector<Value> returnedArgs;
     for (const auto &yieldVal : llvm::enumerate(yieldOp.getValues())) {
       auto yieldArg = yieldVal.value().dyn_cast<BlockArgument>();
       if (!yieldArg || yieldArg.getOwner() != &body)
         return failure();
       unsigned argumentNumber = yieldArg.getArgNumber();

mlir/test/Dialect/Linalg/canonicalize.mlir

 //   CHECK-DAG:   %[[INIT1:.+]] = tensor.empty() : tensor<2x3x4xf32>
 //   CHECK-DAG:   %[[CAST:.+]] = tensor.cast %[[ARG0]] : tensor<?x?x?xf32> to tensor<4x3x2xf32>
 //   CHECK-DAG:   %[[INIT2:.+]] = tensor.empty() : tensor<3x2x4xf32>
 //       CHECK:   %[[GENERIC:.+]]:2 = linalg.generic
 //  CHECK-SAME:       ins(%[[CAST]] :
 //  CHECK-SAME:       outs(%[[INIT2]], %[[INIT1]] :
 //       CHECK:   %[[RETURN_CAST:.+]] = tensor.cast %[[GENERIC]]#0 : tensor<3x2x4xf32> to tensor<?x?x?xf32>
 //       CHECK:   return %[[RETURN_CAST]], %[[GENERIC]]#1
+
+// -----
+
+#map = affine_map<(d0) -> (d0)>
+func.func @identity_mixed(%arg0 : tensor<?xf32>, %arg1: memref<?xf32>) {
+  linalg.generic {
+    indexing_maps = [#map, #map],
+    iterator_types = ["parallel"]
+  } ins(%arg0 : tensor<?xf32>)
+    outs(%arg1 : memref<?xf32>) {
+  ^bb0(%arg2 : f32, %arg3 : f32):
+    linalg.yield %arg2 : f32
+  }
+  return
+}
+
+// There was a crash in EraseIdentityGenericOp for generic with mixed semantics.
+// For now, check generic remained unchanged.
+// CHECK-LABEL: func @identity_mixed
+//  CHECK-SAME:     (%[[ARG1:.*]]: tensor<?xf32>, %[[ARG2:.*]]: memref<?xf32>)
+//       CHECK:     linalg.generic {
+//  CHECK-SAME:    indexing_maps = [#map, #map],
+//  CHECK-SAME:    iterator_types = ["parallel"]
+//  CHECK-SAME:  } ins(%[[ARG1]] : tensor<?xf32>)
+//  CHECK-SAME:    outs(%[[ARG2]] : memref<?xf32>) {