llvm/include
Nirav Dave a9f320779b Prevent construction of cycle in DAG store merge
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
2016-03-25 21:06:30 +00:00
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