Fix missing element types and shapes when autograd.Function has multiple tensor outputs (#57966)
Summary:
When generating IR for autograd.Function, if the function has multiple outputs, a TupleUnpack may be inserted after the original function node, and Pytorch only assigns proper information (tensor element type and shape) to the TupleUnpack and forgets the original function node. In contrast, if autograd.Function only produces one output, the original function node may have tensor
element type and shape in its output schema.
Before this PR:
- (simplified) IR for autograd.Function with one output: input (tensor, dtype=float32, shape=[2, 3]) -> PythonOp -> output (tensor, dtype=float32, shape=[4, 5])
- (simplified) IR for autograd.Function with one output: input (tensor, dtype=float32, shape=[2, 3]) -> PythonOp -> output_0 **(tensor)**, output_1 **(tensor)** -> TupleUnpack output_2 (tensor, dtype=float32, shape=[4, 5]), output_3 (tensor, dtype=float32, shape=[6, 7])
After this PR:
- (simplified) IR for autograd.Function with one output: input (tensor, dtype=float32, shape=[2, 3]) -> PythonOp -> output (tensor, dtype=float32, shape=[4, 5])
- (simplified) IR for autograd.Function with one output: input (tensor, dtype=float32, shape=[2, 3]) -> PythonOp ->output_0 **(tensor, dtype=float32, shape=[4, 5])**, output_1 **(tensor, dtype=float32, shape=[6, 7])** -> TupleUnpack output_2 (tensor, dtype=float32, shape=[4, 5]), output_3 (tensor, dtype=float32, shape=[6, 7])
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57966
Reviewed By: zhxchen17
Differential Revision: D30208207
Pulled By: gmagogsfm
fbshipit-source-id: 42a3d1f9c0932133112a85df0c49cf4ea0afa175
