[llvm] [LoopUnroll] Introduce PragmaUnrollFullMaxIterations as a hard cap on how many iterations we try to unroll (PR #78648)

[David Blaikie via llvm-commits]

dwblaikie wrote:

So not sure I'm following. The condition that was added in this patch that seems to be relevant, if I'm understanding correctly, is to add `UP.Count < TripCount` as a condition to bailout/abort all the unrolling, if the trip count exceeds the count on the unroll pragma, I guess?

But there is no count on the unroll pragma in this case - so why would that condition fire? (I'm poking around in a debugger now to better understand it)

(& I tried to find some documentation, but couldn't - to figure out what `#pragma clang loop unroll` means, and how it differs from `#pragma clang loop unroll(full)` but didn't find any docs - do you have a link to some?)

https://github.com/llvm/llvm-project/pull/78648