LoopSimplify (and other passes) destroyed llvm.loop infos

When I was checking loop-unroll in O1, I thought any loops would not be unrolled since loopunroll was disabled.
LoopSimplify destroyed the loop info !27 at while.end (loop %while.cond), making it enable to be unrolled.
https://godbolt.org/z/v97ojTsn7
I wonder if it is a bug.

The issue names LoopSimplify, loop-unroll, and a Godbolt reproducer. Start by reproducing the example and tracing the LoopSimplify and loop-unroll pass entry points to confirm how the loop metadata affects unrolling. Done means establishing whether the metadata loss is a bug and documenting or testing the expected O1 behavior.

Written by the indexing model from the issue text.