[clang] [Clang][OpenMP][LoopTransformations] Fix incorrect number of generated loops for Tile and Reverse directives (PR #140532)

[Michael Kruse via cfe-commits]

Meinersbur wrote:

This change makes sense to me. In principle, the information of generated loops is only needed in dependent contexts (not yet fully expanded templates); elsewhere we get the loop nest structure from `getTransformedStmt()`. The use in `doForAllLoops` is meant to delay evaluation for when the template is instantiated. A QoI would be able to check the loop structure within a template from this information, even without it needed to be instantiated. I don't think we should remove the information only to be re-added again for #139293.

I think a test case could be possible under the following conditions:
1. reverse construct (number of generated loops of `tile` is positive in either case)
2. In a template definition (dependent context)
3. Loop bounds of reversed loop depends on template parameter (seeing https://github.com/llvm/llvm-project/blob/dedef408d759b50360ae8a7ef2ba13ba6931b4d8/clang/lib/Sema/SemaOpenMP.cpp#L15136 this might not be necessary)
4. Another construct applied to the generated loop of the `reverse` (e.g. unroll)

In that case `doForAllLoops` should `break` instead of `return` causing the following code to execute on the `OMPReverseConstruct` itself instead of a loop, causing an assertion to fail.

https://github.com/llvm/llvm-project/pull/140532