[PlaceSafepoints] Followup to commit L237172
[PlaceSafepoints] Followup to commit L237172

Responding to review feedback from http://reviews.llvm.org/D9585

1) Remove a variable shadow by converting the outer loop to a range for loop.  We never really used the 'i' variable which was being shadowed.
2) Reduce DominatorTree recalculations by passing the DT to SplitEdge.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@237212 91177308-0d34-0410-b5e6-96231b3b80d8

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