[ONNX] Symbolic shape inference (#51481) (#53307)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53307
This PR did symbolic shape inference, in the onnx pass _jit_pass_onnx_graph_shape_type_inference.
It creates a singleton ConstantValueMap.
It leverages constant folding technique and did a per-op based handling for ConstantValueMap.
As a byproduct, it enables fold_if pass for dynamic axes cases, typically for faster-rcnn etc.
The core change is in `torch/csrc/jit/passes/onnx/shape_type_inference.cpp` and `torch/csrc/jit/passes/onnx/constant_map.cpp`.
We usually need copy tensor to store in the ConstantValueMap, otherwise the underlying value may change. I see this issue in (1) from_blob (2) get value from Constant node.
Test Plan: Imported from OSS
Reviewed By: pbelevich, malfet
Differential Revision: D26922414
Pulled By: SplitInfinity
fbshipit-source-id: 7654dc13d1de8d9496ad4be89f1454260d7bdeb0
