Replaced residual + hidden_states with torch.add(residual, hidden_states) to improve memory allocation.
Author: philrwebb
Pull request: yes

replaced tensor1 + tensor2 with torch.add(tensor1, tensor2) because the latter only allocates memory for output tensor.   The tensor in question were hidden_states and residual.   This was blowing up a google colab TPU out of memory.

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Comments:
Hi @philrwebb - thanks for opening a PR! 

Could you remove all of the formatting changes (splitting across lines) from the diff so that we can more easily review and assess the proposed changes? 

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md) are likely to be ignored.