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

[Florian Hahn via Phabricator via llvm-commits]

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

If we hit the limit, we do expand the outstanding tokenfactors.
Otherwise, we might drop nodes with users in the unexpanded
tokenfactors. This fixes the crashes reported by Jordan Rupprecht.


Repository:
  rG LLVM Github Monorepo

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
@@ -1800,9 +1800,20 @@
 
   // 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];
+  bool CompletelyExpanded = true;
+  for (unsigned i = 0; i < TFs.size() ; ++i) {
+    // Limit number of nodes to inline, to avoid quadratic compile times.
+    // Expand outstanding tokenfactors, otherwise we might drop Ops with
+    // users in unexpanded tokenfactors.
+    if (Ops.size() > 2048) {
+      CompletelyExpanded = false;
+      for (; i < TFs.size(); i++)
+        for (const SDValue &Op : TFs[i]->op_values())
+          Ops.push_back(Op);
+      break;
+    }
 
+    SDNode *TF = TFs[i];
     // Check each of the operands.
     for (const SDValue &Op : TF->op_values()) {
       switch (Op.getOpcode()) {
@@ -1923,7 +1934,7 @@
       // The entry token is the only possible outcome.
       Result = DAG.getEntryNode();
     } else {
-      if (DidPruneOps) {
+      if (DidPruneOps && CompletelyExpanded) {
         SmallVector<SDValue, 8> PrunedOps;
         //
         for (const SDValue &Op : Ops) {


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