Move some sets and maps to SmallPtrSet and DenseMap respectively.  This  reduces the time to optimize 403.gcc from 17.6s to 16.4s.
Move some sets and maps to SmallPtrSet and DenseMap respectively.  This 
reduces the time to optimize 403.gcc from 17.6s to 16.4s.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@40036 91177308-0d34-0410-b5e6-96231b3b80d8

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