Simplify IfThenElse and CompareSelect within for-loop (#76793)
Analyze the range to determine if a condition cannot be satisfied. Suppose the for-loop body contains `IfThenElse` or `CompareSelect` while the condition of the two statements depends on the for-loop index `Var`. In that case, we will analyze the range to check whether the condition could always be satisfied or not. If the condition is deterministic, simplify the logic.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/76793
Approved by: https://github.com/huiguoo
