[polly] r217525 - Allow to generate a loop without the GuardBB

[Tobias Grosser]

On 10/09/2014 19:33, Johannes Doerfert wrote:
> Author: jdoerfert
> Date: Wed Sep 10 12:33:32 2014
> New Revision: 217525
>
> URL: http://llvm.org/viewvc/llvm-project?rev=217525&view=rev
> Log:
> Allow to generate a loop without the GuardBB
>
>    This allows us to omit the GuardBB in front of created loops
>    if we can show the loop trip count is at least one. It also
>    simplifies the dominance relation inside the new created region.
>    A GuardBB (even with a constant branch condition) might trigger
>    false dominance errors during function verification.
>
> Differential Revision: http://reviews.llvm.org/D5297

Nice.

For the record. It should also be possible to derive the at-least-once 
condition on the polyhedral side. This will possibly enable the 
elimination of more guards, in case of iteration space boundaries that
are too complicated for SCEV to understand.

Tobias