[PATCH] D61511: [DAGCombiner] Limit number of nodes explored as store candidates.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: niravd, spatel, craig.topper.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

To find the candidates to merge stores we iterate over all nodes in a chain
for each store, which leads to quadratic compile times for large basic blocks
with a large number of stores.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D61511

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


Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -14838,9 +14838,11 @@
 
   RootNode = St->getChain().getNode();
 
+  unsigned NumNodesExplored = 0;
   if (LoadSDNode *Ldn = dyn_cast<LoadSDNode>(RootNode)) {
     RootNode = Ldn->getChain().getNode();
-    for (auto I = RootNode->use_begin(), E = RootNode->use_end(); I != E; ++I)
+    for (auto I = RootNode->use_begin(), E = RootNode->use_end();
+         I != E && NumNodesExplored < 1024; ++I, NumNodesExplored++)
       if (I.getOperandNo() == 0 && isa<LoadSDNode>(*I)) // walk down chain
         for (auto I2 = (*I)->use_begin(), E2 = (*I)->use_end(); I2 != E2; ++I2)
           if (I2.getOperandNo() == 0)
@@ -14851,7 +14853,8 @@
                 StoreNodes.push_back(MemOpLink(OtherST, PtrDiff));
             }
   } else
-    for (auto I = RootNode->use_begin(), E = RootNode->use_end(); I != E; ++I)
+    for (auto I = RootNode->use_begin(), E = RootNode->use_end();
+         I != E && NumNodesExplored < 1024; ++I, NumNodesExplored++)
       if (I.getOperandNo() == 0)
         if (StoreSDNode *OtherST = dyn_cast<StoreSDNode>(*I)) {
           BaseIndexOffset Ptr;


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