[llvm] [polly] [llvm][ConstraintElimination]Insert ConditionFact into loop header in case of monotonic induction variables (PR #112080)

[Grigory Pastukhov via llvm-commits]

grigorypas wrote:

> I am somewhat worried that this sort of constraint is not already added to the system because of compile time considerations. It would be good if you could outline the expected complexity effects here as program inputs grow. And not being too familiar with this part of the compiler myself I have to defer to @nikic and @fhahn for whether we need to be careful with the complexity here or if this is fine?

There is a limit on the number of constraints (MaxRaws parameter) that can be added to the same system of constraints (all additional onces are dropped). The default for this limit is 500. I also restricted these new constraints to be applied only for functions with less than MaxRaws / 5 number of conditional branches to avoid potential regression due to hitting MaxRaws limit. 

https://github.com/llvm/llvm-project/pull/112080