[PATCH] D46955: [DAG] Prune cycle check in store merge.

[Nirav Dave via Phabricator via llvm-commits]

niravd created this revision.
niravd added a reviewer: jyknight.
Herald added a subscriber: hiraditya.

As part of merging stores we check that fusing the nodes does not
cause a cycle due to one candidate store being indirectly dependent on
another store (this may happen via chained memory copies). This is
done by searching if a store is a predecessor to another store's
value.

Prune the search at the candidate search's root node which is a
predecessor to all candidate stores. This reduces the
size of the subgraph searched in large basic blocks.


Repository:
  rL LLVM

https://reviews.llvm.org/D46955

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

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