From a3b2103ffc378bb6c82a05e720163f448149cd75 Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Tue, 29 Aug 2017 21:38:44 +0000 Subject: Merging r312022: ------------------------------------------------------------------------ r312022 | hans | 2017-08-29 11:41:00 -0700 (Tue, 29 Aug 2017) | 10 lines [DAG] Bound loop dependence check in merge optimization. The loop dependence check looks for dependencies between store merge candidates not captured by the chain sub-DAG doing a check of predecessors which may be very large. Conservatively bound number of nodes checked for compilation time. (Resolves PR34326). Landing on behalf of Nirav Dave to unblock the 5.0.0 release. Differential Revision: https://reviews.llvm.org/D37220 ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_50@312041 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/llvm/CodeGen/SelectionDAGNodes.h | 5 ++++- lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 22 +++++++++++++++++----- 2 files changed, 21 insertions(+), 6 deletions(-) diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h index 051c93601d3f..5fb69ae232af 100644 --- a/include/llvm/CodeGen/SelectionDAGNodes.h +++ b/include/llvm/CodeGen/SelectionDAGNodes.h @@ -801,7 +801,8 @@ public: /// if DAG changes. static bool hasPredecessorHelper(const SDNode *N, SmallPtrSetImpl &Visited, - SmallVectorImpl &Worklist) { + SmallVectorImpl &Worklist, + unsigned int MaxSteps = 0) { if (Visited.count(N)) return true; while (!Worklist.empty()) { @@ -816,6 +817,8 @@ public: } if (Found) return true; + if (MaxSteps != 0 && Visited.size() >= MaxSteps) + return false; } return false; } diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index a083f23bf923..432c86dd6f1e 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -12607,25 +12607,37 @@ void DAGCombiner::getStoreMergeCandidates( } } -// We need to check that merging these stores does not cause a loop -// in the DAG. Any store candidate may depend on another candidate +// We need to check that merging these stores does not cause a loop in +// the DAG. Any store candidate may depend on another candidate // indirectly through its operand (we already consider dependencies // through the chain). Check in parallel by searching up from // non-chain operands of candidates. + bool DAGCombiner::checkMergeStoreCandidatesForDependencies( SmallVectorImpl &StoreNodes, unsigned NumStores) { + + // FIXME: We should be able to truncate a full search of + // predecessors by doing a BFS and keeping tabs the originating + // stores from which worklist nodes come from in a similar way to + // TokenFactor simplfication. + SmallPtrSet Visited; SmallVector Worklist; - // search ops of store candidates + unsigned int Max = 8192; + // Search Ops of store candidates. for (unsigned i = 0; i < NumStores; ++i) { SDNode *n = StoreNodes[i].MemNode; // Potential loops may happen only through non-chain operands for (unsigned j = 1; j < n->getNumOperands(); ++j) Worklist.push_back(n->getOperand(j).getNode()); } - // search through DAG. We can stop early if we find a storenode + // Search through DAG. We can stop early if we find a store node. for (unsigned i = 0; i < NumStores; ++i) { - if (SDNode::hasPredecessorHelper(StoreNodes[i].MemNode, Visited, Worklist)) + if (SDNode::hasPredecessorHelper(StoreNodes[i].MemNode, Visited, Worklist, + Max)) + return false; + // Check if we ended early, failing conservatively if so. + if (Visited.size() >= Max) return false; } return true; -- cgit v1.2.3