Merging r182485:

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r182485 | arnolds | 2013-05-22 09:54:56 -0700 (Wed, 22 May 2013) | 7 lines

LoopVectorize: Make Value pointers that could be RAUW'ed a VH

The Value pointers we store in the induction variable list can be RAUW'ed by a
call to SCEVExpander::expandCodeFor, use a TrackingVH instead. Do the same thing
in some other places where we store pointers that could potentially be RAUW'ed.

Fixes PR16073.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_33@182492 91177308-0d34-0410-b5e6-96231b3b80d8