Implement a more intelligent way of spilling uses across an invoke boundary.
Implement a more intelligent way of spilling uses across an invoke boundary.

The old way of determine when and where to spill a value that was used inside of
a landing pad resulted in spilling that value everywhere and not just at the
invoke edge.

This algorithm determines which values are used within a landing pad. It then
spills those values before the invoke and reloads them before the uses. This
should prevent excessive spilling in many cases, e.g. inside of loops.
<rdar://problem/10609139>


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@152486 91177308-0d34-0410-b5e6-96231b3b80d8

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