Also compute interference intervals for blocks with no uses.
Also compute interference intervals for blocks with no uses.

When the live range is live through a block that doesn't use the register, but
that has interference, region splitting wants to split at the top and bottom of
the basic block.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@124839 91177308-0d34-0410-b5e6-96231b3b80d8

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