Strengthen GetUnderlyingObject using InstructionSimplify.
Strengthen GetUnderlyingObject using InstructionSimplify.

While LLVM's main design is that analysis code shouldn't
go out of its way to understand code which hasn't been
InstCombined, analysis utility routines like this can
find themselves being called in the middle of transform
passes when instcombine hasn't had a chance to run.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@121886 91177308-0d34-0410-b5e6-96231b3b80d8

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