[onnx] Fix onnx.RNN for layout attribute (llvm#3620)

The `layout` attribute was not considered for the `onnx.RNN` operation.
Added support for the attribute to transpose the inputs / outputs of the
RNN when valid.

Author: rsuderman

lib/Conversion/TorchOnnxToTorch/OnnxRecurrentLayerOpExpanders.cpp

@@ -151,6 +151,22 @@ RnnLayerOutput rnn_layer(ImplicitLocOpBuilder &b, Value X, Value initial_h,
   output.Y_h = loop.getResult(1);
   return output;
 }
+
+static Value StaticTranspose(ImplicitLocOpBuilder b, Value value, int64_t dim0,
+                             int64_t dim1) {
+  auto valueTy = cast<ValueTensorType>(value.getType());
+
+  SmallVector<int64_t> valueShape(valueTy.getSizes());
+  std::swap(valueShape[dim0], valueShape[dim1]);
+  valueTy = b.getType<ValueTensorType>(valueShape, valueTy.getDtype());
+
+  auto intType = b.getType<IntType>();
+  Value dim0v = b.create<ConstantIntOp>(intType, b.getI64IntegerAttr(dim0));
+  Value dim1v = b.create<ConstantIntOp>(intType, b.getI64IntegerAttr(dim1));
+
+  return b.create<AtenTransposeIntOp>(valueTy, value, dim0v, dim1v);
+}
+
 LogicalResult OnnxRnnExpander(OpBinder binder,
                               ConversionPatternRewriter &rewriter) {
   Location loc = binder.getLoc();
@@ -201,9 +217,19 @@ LogicalResult OnnxRnnExpander(OpBinder binder,
     return rewriter.notifyMatchFailure(
         binder.op, "Missing required attribute hidden_size");
 
+  // Other attributes
+  int64_t layout;
+  if (binder.s64IntegerAttr(layout, "layout", 0))
+    return rewriter.notifyMatchFailure(binder.op,
+                                       "Unsupported layout attribute type.");
+
+  if (layout < 0 || layout > 1)
+    return rewriter.notifyMatchFailure(binder.op,
+                                       "Unsupported layout attribute value.");
+
   // Result types
   ValueTensorType yTy, Y_hType;
-  if (binder.tensorResultTypeAtIndex(yTy, 0) ||
+  if (binder.tensorResultTypeAtIndex(yTy, 0) &&
       binder.tensorResultTypeAtIndex(Y_hType, 1)) {
     return rewriter.notifyMatchFailure(binder.op,
                                        "At least one output must be present");
@@ -229,6 +255,12 @@ LogicalResult OnnxRnnExpander(OpBinder binder,
     initial_h = nullptr;
   }
 
+  if (layout == 1) {
+    X = StaticTranspose(b, X, 0, 1);
+    if (initial_h)
+      initial_h = StaticTranspose(b, initial_h, 0, 1);
+  }
+
   // validation
   auto xTy = cast<ValueTensorType>(X.getType());
   auto wTy = cast<ValueTensorType>(W.getType());
@@ -238,6 +270,7 @@ LogicalResult OnnxRnnExpander(OpBinder binder,
   auto rShape = rTy.getSizes();
   assert(wShape.size() == 3);
 
+  int64_t seq_len = xShape[0];
   int64_t batch_size = xShape[1];
   int64_t x_input_size = xShape[2];
 
@@ -368,7 +401,24 @@ LogicalResult OnnxRnnExpander(OpBinder binder,
   Value Y_h_unsqueezed = b.create<AtenUnsqueezeOp>(Y_h_unsqueezed_type,
                                                    rnnLayerOutput.Y_h, cstZero);
 
-  Value Y_unsqueezed = b.create<AtenUnsqueezeOp>(yTy, rnnLayerOutput.Y, cstOne);
+  auto Y_unsqueezed_type = b.getType<ValueTensorType>(
+      llvm::SmallVector<int64_t>{seq_len, num_directions, batch_size,
+                                 hidden_size},
+      cast<ValueTensorType>(rnnLayerOutput.Y_h.getType()).getDtype());
+  Value Y_unsqueezed =
+      b.create<AtenUnsqueezeOp>(Y_unsqueezed_type, rnnLayerOutput.Y, cstOne);
+
+  if (layout == 1) {
+    Y_h_unsqueezed = StaticTranspose(b, Y_h_unsqueezed, 0, 1);
+    Y_unsqueezed = StaticTranspose(b, Y_unsqueezed, 1, 2);
+    Y_unsqueezed = StaticTranspose(b, Y_unsqueezed, 0, 1);
+  }
+
+  if (!yTy)
+    Y_unsqueezed = cstNone;
+  if (!Y_hType)
+    Y_h_unsqueezed = cstNone;
+
   rewriter.replaceOp(binder.op, {Y_unsqueezed, Y_h_unsqueezed});
   return success();
 }