[PATCH] Add a flag to experiment with outlining optional branches.

[Philip Reames]

Codewise, I have some concern about adding the post dominator dependency.  Any idea how much running time that adds?  Otherwise, LGTM.

Approach wise, I think you may want to invert your reasoning.  Your currently inferring coldness of the conditional block from the hotness of the successor.  It would be more clear and predictable to consider the probability of the skipped successors directly.

Overall, I'm really excited about the direction of this patch.  This might be very material on my workloads.  Once this is landed, I'll do a run and see what differences I can report.


http://reviews.llvm.org/D7719

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