[llvm] [LoopUnroll] Skip remainder loop guard if skip unrolled loop (PR #156549)

[Valery Dmitriev via llvm-commits]

valerydmit wrote:

> > @jdenny-ornl , this patch caused more than 25% performance degradation due to additional spills/reloads. Could you please take a look? [f.zip](https://github.com/user-attachments/files/23277796/f.zip) To reproduce compile the attached file with O3 using flang or clang.
> 
> Thanks for the report. Are you using `-pass-remarks-missed=regalloc` or some other tool to see the performance change?
Performance was verified on a hardware. I've built compiler before/after the commit to verify it is the culprit.
clang annotates produced assembler (-S). I also used -save-stats option for pass statistics.  
The routine represents an outlined openmp region.

https://github.com/llvm/llvm-project/pull/156549