[clang] [llvm] [SimplifyCFG] Not folding branch in loop header with constant iterations (PR #74268)

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xiangzh1 wrote:

> > > And I think you need to precommit tests first.
Done
> > In fact, there is no direct/strong relation with stack cost, it mostly base on unroll or not (or other loop optimizations). Maybe we should check "unroll" info (e.g #pragma unroll, any targets with this hint should try best to unroll too) before do or not do this folding. A little trouble is loop info is not well established now.
> 
> Yeah, it is a problem we unroll or not. But this case generally I believe we don't want to unroll it.
Update to handle unroll hint
Thanks for reviewing!


https://github.com/llvm/llvm-project/pull/74268