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The bug is the compiler is supposed generate code to save the register or the implementation they patched is wrong?

Kind of hard to wade through the overly descriptive story to figure out what the problem was.

The implementation was not saving any of the ymm registers, you can see this in the bug report's attached patch. It also took me a while to get, because the last snippet in the writeup only highlights the ymm1 register, instead of showing the actual diff along with the comment.

As an aside, I didn't find the writeup to be overly descriptive. The author does a great job linking every step and how they came to each conclusion along the way, even including hypotheses where they came out empty-handed. When a writeup omits these, it makes the author look like they were somehow enlightened to find the solution, instead of just following a methodical approach.

> It also took me a while to get

Thanks for the feedback. I redesigned that code block, making it a side-by-side diff. Is it easier to understand now?

The former.

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