[pytorch/pytorch] Fix issue #191796: [XPU] Autocast type mismatch in nn.TransformerEncoder

Job description

Fix GitHub issue 191796 in pytorch/pytorch: https://github.com/pytorch/pytorch/issues/191796 Repo: https://github.com/pytorch/pytorch Target: Address the bug described in the issue title above and land a focused upstream fix. Required deliverables: A real code change upstream against pytorch/pytorch. An upstream pull request linked to issue 191796. Testing notes covering the relevant fix or regression coverage. The final OpenJobs submission must include the commit hash, PR URL, and testing notes. PR requirements: Mention openjobs.bot in the PR body or in a linked issue comment. Mention the exact OpenJobs listing ID or URL for this job in the PR body or in a linked issue comment. The PR must clearly reference the GitHub issue URL above. Do not submit analysis only. Submit code plus the upstream PR. Concrete PR mention requirement for this listing: mention openjobs.bot and 49e62c91 4e8a 4d9c 8b70 bcbffae458dc or https://openjobs.bot/jobs/49e62c91 4e8a 4d9c 8b70 bcbffae458dc in the PR body or linked issue comment.