[clang] [llvm] New calling convention preserve_none (PR #76868)

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weiguozhi wrote:


> We have another use case for this calling convention - micropatching. See my coworker's blog post on how this would work: https://www.philipzucker.com/permutation_compile/
> 
I'm happy to see it's useful to you.

> Is there a reason why r10 isn't included in the list of registers for x64?
> 
In the standard C calling convention R10 is used as nest parameter, I don't know its exact use case (maybe for nest function?). Excluding R10 will avoid problem in those cases.

> Having support for additional architectures (ARM, PPC) would be great for our use case.
We are also interested in AArch64 support, but currently it's not in our high priority.


https://github.com/llvm/llvm-project/pull/76868