🐛 [Bug] Differing behavior for fully-supported models with collection outputs, when toggling `require_full_compilation`

[gs-olive]

Bug Description

For model types which are fully-supported in Torch-TRT, but which use complex collections of outputs, for example Tuple[Tensor, Tensor], or Tuple[Tensor, Tuple[Tensor, Tensor]], the compilation behavior of Torch-TRT is different when the flag require_full_compilation is enabled versus not.

When require_full_compilation=False, the model compiles successfully, and the only operations executed in Torch are collections-processing operations. When require_full_compilation=True, however, the model fails with:

RuntimeError: [Error thrown at core/conversion/conversion.cpp:230] Tuple type. Only a single tensor or a TensorList type is supported.

To Reproduce

Steps to reproduce the behavior:

1. Define a fully convertible Torch model with forward function having the following form:

def forward(self, input : Tensor) -> Tuple[torch.Tensor, Tuple[torch.Tensor, torch.Tensor]]:

2. Define the Torch-TRT Inputs and compilation settings using require_full_compilation=True, then compile the scripted model:

compile_settings = {
    "inputs": [torch_tensorrt.Input((5, 5), dtype=torch.float)],
    "enabled_precisions": {torch.float},
    "truncate_long_and_double": True,
    "require_full_compilation": True,
}
trt_ts_module = torch_tensorrt.ts.compile(scripted_model, **compile_settings)

Expected behavior

Model should compile with require_full_compilation=True, when containing nested Tuple collection.

Environment

• Torch-TensorRT Version: 1.4.0.dev0+f43be5b6
• PyTorch Version: 1.14.0.dev20221114+cu116
• CPU Architecture: Intel Xeon CPU
• OS: Ubuntu 20.04
• How you installed PyTorch: pip
• Build command you used: python setup.py develop
• Are you using local sources or building from archives: local
• Python version: 3.8.13
• CUDA version: 11.6

Additional context

This bug is related to, but not the same as #1595, as this bug relates to nested collection outputs and not inputs. The resolution to both of these bugs should resolve the overall issue of having fully-compiled models with complex collections of inputs and outputs.

This particular bug also appears when compiling the HuggingFace BERT uncased model with require_full_compilation=True.

[Christina-Young-NVIDIA]

Fixed with #1599