Measure the worst case number of probes for a miss instead of the less
conservative number of probes required for an insertion.
Lower the limit to < 6 probes worst case.
This doubles the size of the ARM and X86 hash tables, other targets are
unaffected. LiveVariables runs 12% faster with this change.
<rdar://problem/9598545>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132999 91177308-0d34-0410-b5e6-96231b3b80d8
