[mlir][Bufferization] Support cast from ranked to unranked in canonic… (llvm#152257)

llvm#150511 changed the
canonicalization pattern to not allow casts from ranked to unranked
anymore. This patch restores this functionality, while still keeping the
fix to preserve memory space and layout.

Author: akuegel

mlir/lib/Dialect/Bufferization/IR/BufferizationOps.cpp

@@ -806,14 +806,12 @@ struct ToBufferOfCast : public OpRewritePattern<ToBufferOp> {
     if (!srcTensorType)
       return failure();
     auto currentOutputMemRefType =
-        dyn_cast<MemRefType>(toBuffer.getResult().getType());
+        dyn_cast<BaseMemRefType>(toBuffer.getResult().getType());
     if (!currentOutputMemRefType)
       return failure();
 
-    auto memrefType = MemRefType::get(srcTensorType.getShape(),
-                                      srcTensorType.getElementType(),
-                                      currentOutputMemRefType.getLayout(),
-                                      currentOutputMemRefType.getMemorySpace());
+    auto memrefType = currentOutputMemRefType.cloneWith(
+        srcTensorType.getShape(), srcTensorType.getElementType());
     Value memref = ToBufferOp::create(rewriter, toBuffer.getLoc(), memrefType,
                                       tensorCastOperand.getOperand(),
                                       toBuffer.getReadOnly());

mlir/test/Dialect/Bufferization/canonicalize.mlir

@@ -263,6 +263,19 @@ func.func @tensor_cast_to_buffer(%arg0 : tensor<4x6x16x32xi8>) ->
 // CHECK-SAME: memref<4x6x16x32xi8> to memref<?x?x16x32xi8>
 // CHECK:   return %[[M1]] : memref<?x?x16x32xi8>
 
+// CHECK-LABEL: func @tensor_cast_to_unranked_buffer
+//  CHECK-SAME:   %[[ARG0:.+]]: tensor<4x6x16x32xi8>
+func.func @tensor_cast_to_unranked_buffer(%arg0 : tensor<4x6x16x32xi8>) ->
+  memref<*xi8> {
+  %0 = tensor.cast %arg0 : tensor<4x6x16x32xi8> to tensor<*xi8>
+  %1 = bufferization.to_buffer %0 read_only : tensor<*xi8> to memref<*xi8>
+  return %1 : memref<*xi8>
+}
+// CHECK:   %[[M:.+]] = bufferization.to_buffer %[[ARG0]] read_only : tensor<4x6x16x32xi8>
+// CHECK:   %[[M1:.+]] = memref.cast %[[M]]
+// CHECK-SAME: memref<4x6x16x32xi8> to memref<*xi8>
+// CHECK:   return %[[M1]] : memref<*xi8>
+
 // -----
 
 // CHECK-LABEL: func @tensor_cast_to_buffer