[PATCH] [MBP] Don't outline short optional branches

[Daniel Jasper]

================
Comment at: lib/CodeGen/MachineBlockPlacement.cpp:394
@@ +393,3 @@
+              Pred->size() < OutlineOptionalThreshold)
+            return Pred;
+        }
----------------
chandlerc wrote:
> Shouldn't this be disabling the return of Succ here rather than arbitrarily returning Pred?
> 
> And in general, it seems very strange to look at all of the predecessors' predecessors here. That seems really expensive and it isn't clear why. This at least needs some serious commenting to clarify the algorithm used.
Addressed both concerns.

http://reviews.llvm.org/D8108

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