[PATCH] [OPENMP] llvm.loop.vectorize.enable metadata are lost after critical edge splitting

[Andrew Trick]

Is it incorrect to leave the loop metadata on the original branch when splitting the edge?

GVN already requires DomTree, so no change to the pipeline is needed if you use it.

In splitCriticalEdges, if LoopInfo is available you can use it. Otherwise you can use the DomTree. If the DomTree check fails (ie. both targets dominate the latch) then just invalidate the metadata.

I think there is a fundamental problem with the metadata design--it's ridiculous to assume that any pass that splits critical edges has LoopInfo--but that should at least workaround your problem.

http://reviews.llvm.org/D5539