[llvm] [LoopInterchange] Constrain number of load/stores in a loop (PR #118973)

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CongzheUalberta wrote:

> When I profiled this change on LLVM Test-suite, I see 39 interchanges compared to 43 with the trunk. If I bump up the value of `MaxMemInstrCount` to 128, I see 42 interchanges. However, with 128 we see bump in the compile-time too. Please find numbers here [ ](https://llvm-compile-time-tracker.com/index.php?config=stage2-O3&stat=instructions%3Au&remote=madhur13490) the branch is `madhur13490/perf/revert_and_bound_instr_64`
> 
> This change tries to achieve trade-off between the number of loop interchanges and compile-time. Indeed, compile-time is directly proportional to the value of `MaxMemInstCount`.

With your results I see compile time actually increases with this patch but not decreases? For example compare the results of commit `ae719f0756` versus commit `f8c5d74865`/`bfbcc6d728`.

https://github.com/llvm/llvm-project/pull/118973