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
When merging stores in DAGCombiner, add check to ensure that no dependenices exist that would cause the construction of a cycle in our DAG. This may happen if one store has a data dependence on another instruction (e.g. a load) which itself has a (chain) dependence on another store being merged. These stores cannot be merged safely and doing so results in a cycle that is discovered in LegalizeDAG. This test is only done in cases where Antialias analysis is used (UseAA) as non-AA store merge candidates will be merged logically after all loads which have been checked to not alias. Reviewers: ahatanak, spatel, niravd, arsenm, hfinkel, tstellarAMD, jyknight Subscribers: llvm-commits, tberghammer, danalbert, srhines Differential Revision: http://reviews.llvm.org/D18336 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264461 91177308-0d34-0410-b5e6-96231b3b80d8