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

[via llvm-commits]

xiangzh1 wrote:

> I think you are confusing upper bound and runtime unrolling. An upper bound unroll is a type of full unroll. In this case it would unroll it to 16 iterations, which is what you want, no?
Yes！: ) I thouth the upper bound is "partial unroll", and I am supprised if it can fully unroll to 16 iterations with the branch folding, anyway let me check shouldPragmaUnroll(), thank you a lot!
 

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