upsample_bilinear: fix output data-type. (#7111)

test/test_operations.py

@@ -2069,6 +2069,54 @@ def test(f, xshape, ishapes):
     for xshape, i0shape, i1shape in cases[f2]:
       test(f2, xshape, (i0shape, i1shape))
 
+  def test_upsample_bilinear_double(self):
+    # Originally, the upsample_bilinear implementation (in resize_ops.cpp)
+    # was copied from TF. The computation was done intentionally on F32 and
+    # not cast back[1]. However, that didn't reflect in the returned tensor.
+    # Basically, what would happen is:
+    #
+    # 1. A tensor of data-type other than F32 is created:
+    #    > a = torch.rand(..., dtype=torch.double)
+    #
+    # 2. Call upsample_bilinear on it
+    #    > r = torch.nn.functional.upsample_bilinear(a, scale_factor=2)
+    #
+    # 3. The result's data-type would show as torch.float64, but its inner
+    #    HLO representation would be actually F32.
+    #
+    #     - It would rarely surface as an error, since we do data-type
+    #       promotion at the HLO level.
+    #
+    #     - When this result is the argument of a new HLO function, XLA
+    #       would actually expect a F16 tensor, since its torch.Tensor
+    #       data-type "is" torch.float16. However, since the actual HLO
+    #       data-type is F32, XLA raises an error.
+    #
+    # See more details at [2].
+    #
+    # [1]: https://github.com/tensorflow/tensorflow/commit/f8b35e00afe09c8606bcb0441a51be8bd38168d2
+    # [2]: https://github.com/pytorch/xla/issues/7095
+
+    def foo(x, is_xla=False):
+      # Compute upsample_bilinear.
+      r = torch.nn.functional.upsample_bilinear(x, scale_factor=2)
+
+      if is_xla:
+        # Mark the end of the HLO graph.
+        xm.mark_step()
+
+      # Start a new HLO graph using the upsample_bilinear result as
+      # one of its arguments.
+      return r + 5
+
+    inp = torch.rand(1, 3, 10, 10, dtype=torch.double)
+    Xinp = inp.to(xm.xla_device())
+
+    out = foo(inp)
+    Xout = foo(Xinp, is_xla=True)
+
+    self.assertEqual(out, Xout.cpu())
+
 
 class MNISTComparator(nn.Module):
 

torch_xla/csrc/resize_ops.cpp

@@ -21,6 +21,10 @@ xla::XlaOp BuildResize(xla::XlaOp input, const xla::Shape& output_shape,
                        bool is_kernel_bilinear) {
   // Code copied from
   // https://github.com/tensorflow/tensorflow/blob/e51d6ab5730092775d516b18fa4ee85d49602cd8/tensorflow/compiler/tf2xla/kernels/image_resize_ops.cc#L477-L672
+  //
+  // Changes:
+  // - Remove F32 data-type conversion when is_kernel_bilinear
+  //   See: https://github.com/pytorch/xla/issues/7095
 
   // We implement bilinear interpolation and nearest neighbor with a Gather op.
   // For each output pixel, we gather the necessary slices of the input.
@@ -53,7 +57,7 @@ xla::XlaOp BuildResize(xla::XlaOp input, const xla::Shape& output_shape,
       << "input and output must have the same element type";
 
   xla::PrimitiveType original_input_type = input_type;
-  if (is_kernel_bilinear || xla::primitive_util::IsIntegralType(input_type)) {
+  if (xla::primitive_util::IsIntegralType(input_type)) {
     input = xla::ConvertElementType(input, xla::F32);
     input_type = xla::F32;
   }
@@ -210,7 +214,7 @@ xla::XlaOp BuildResize(xla::XlaOp input, const xla::Shape& output_shape,
   absl::InlinedVector<int64_t, 4> perm = {2, 0, 1, 3};
   input = xla::Transpose(input, perm);
 
-  if (!is_kernel_bilinear && original_input_type != input_type) {
+  if (original_input_type != input_type) {
     input = xla::ConvertElementType(input, original_input_type);
   }
   return input;