[PATCH] D62633: Recommit r360171: [DAGCombiner] Avoid creating large tokenfactors in visitTokenFactor.

[Florian Hahn via Phabricator via llvm-commits]

fhahn updated this revision to Diff 202334.
fhahn added a comment.

Only add tokenfactors instead of inlining the first TF. Adjust logic for adding
TFs to the worklist accordingly.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62633/new/

https://reviews.llvm.org/D62633

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
@@ -1801,8 +1801,19 @@
   // Iterate through token factors.  The TFs grows when new token factors are
   // encountered.
   for (unsigned i = 0; i < TFs.size(); ++i) {
-    SDNode *TF = TFs[i];
+    // Limit number of nodes to inline, to avoid quadratic compile times.
+    // We have to add the outstanding tokenfactors to Ops, otherwise we might
+    // drop Ops from the resulting tokenfactor.
+    if (Ops.size() > 5) {
+      for (unsigned j = i; j < TFs.size(); j++)
+        Ops.emplace_back(TFs[j], 0);
+      // Drop unprocessed tokenfactors from TFs, so we do not add them to the
+      // combiner worklist later.
+      TFs.resize(i);
+      break;
+    }
 
+    SDNode *TF = TFs[i];
     // Check each of the operands.
     for (const SDValue &Op : TF->op_values()) {
       switch (Op.getOpcode()) {
@@ -1816,8 +1827,6 @@
         if (Op.hasOneUse() && !is_contained(TFs, Op.getNode())) {
           // Queue up for processing.
           TFs.push_back(Op.getNode());
-          // Clean up in case the token factor is removed.
-          AddToWorklist(Op.getNode());
           Changed = true;
           break;
         }
@@ -1834,6 +1843,11 @@
     }
   }
 
+  // Re-visit inlined tokenfactors, to clean them up in case they have been
+  // removed. Skip the first tokenfacto, as this is the current node.
+  for (unsigned i = 1, e = TFs.size(); i < e ; i++)
+    AddToWorklist(TFs[i]);
+
   // Remove Nodes that are chained to another node in the list. Do so
   // by walking up chains breath-first stopping when we've seen
   // another operand. In general we must climb to the EntryNode, but we can exit


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