[llvm] [SLP]Support reordered buildvector nodes for better clustering (PR #114284)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

> FYI this has some compile-time impact, though it's not particularly large: https://llvm-compile-time-tracker.com/compare.php?from=8699f301ae70ce402618c061b6c45a99e31c5f5e&to=76422385c3081475ed1bf0e23aa2f3913e66c5b8&stat=instructions:u I think the largest change is:
> 
> ```
>     CMakeFiles/clamscan.dir/shared_sha256.c.o 	1524M 	1566M (+2.76%)
> ```

Will check and try to fix, thanks

https://github.com/llvm/llvm-project/pull/114284