[PATCH, Loop optimizer]: Add logic to disable certain loop optimizations on pre-/post-loops

[Zdenek Dvorak]

Hi,

> For prefetching of prologue or epilogue loops, we have two choices (1) prefetching not 
> not unrolling, (2) not prefetching.  Which one do you prefer?

it is better not to prefetch (the current placement of prefetches is not good for non-rolling
loops),

Zdenek