Fix #97510 . Note that, for the new phi instruction `NewPH`, which replaces the old phi `PH` and the cast `ShadowUse`, I choose to propagate the debug location of `PH` to it, because the cast is eliminated according to the optimization semantics.
Fix #97510 . Note that, for the new phi instruction `NewPH`, which replaces the old phi `PH` and the cast `ShadowUse`, I choose to propagate the debug location of `PH` to it, because the cast is eliminated according to the optimization semantics.