[llvm] [ms] [llvm-ml] Allow PTR casting of registers to their own size (PR #132751)

[Nikita Popov via llvm-commits]

nikic wrote:

> > Not sure what's going on here, but this change increases the ThinLTO link time for clang by 2.5% (https://llvm-compile-time-tracker.com/compare_clang.php?from=40edc34782b3a804639042c2981c3c4ae6661a92&to=344708c2a3de005060242a77ccfea753406af8d0&stat=instructions%3Au&sortBy=interestingness).
> 
> All I can think is that we brought in `"X86RegisterInfo.h"`? But that doesn't seem like it should be dramatic.

I've checked that it's not the header. I expect that something in this change is exposing pathological behavior in LLVM.

https://github.com/llvm/llvm-project/pull/132751