[PATCH] D56739: [SelectionDAG] Add splitAcrossTokenFactors to split nodes with > 64k operands.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: RKSimon, aemerson, craig.topper, efriedma.
Herald added a subscriber: hiraditya.

This functionality is required at multiple places which potentially
create large operand lists, like SelectionDAGBuilder or DAGCombiner.

Also updates the limit computation to use numeric_limits, as does the
assertion in createOperands.


https://reviews.llvm.org/D56739

Files:
  llvm/include/llvm/CodeGen/SelectionDAG.h
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp


Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1032,19 +1032,9 @@
   }
 
   // Otherwise, we have to make a token factor node.
-  // If we have >= 2^16 loads then split across multiple token factors as
-  // there's a 64k limit on the number of SDNode operands.
-  SDValue Root;
-  size_t Limit = (1 << 16) - 1;
-  while (PendingLoads.size() > Limit) {
-    unsigned SliceIdx = PendingLoads.size() - Limit;
-    auto ExtractedTFs = ArrayRef<SDValue>(PendingLoads).slice(SliceIdx, Limit);
-    SDValue NewTF =
-        DAG.getNode(ISD::TokenFactor, getCurSDLoc(), MVT::Other, ExtractedTFs);
-    PendingLoads.erase(PendingLoads.begin() + SliceIdx, PendingLoads.end());
-    PendingLoads.emplace_back(NewTF);
-  }
-  Root = DAG.getNode(ISD::TokenFactor, getCurSDLoc(), MVT::Other, PendingLoads);
+  DAG.splitAcrossTokenFactors(getCurSDLoc(), PendingLoads);
+  SDValue Root =
+      DAG.getNode(ISD::TokenFactor, getCurSDLoc(), MVT::Other, PendingLoads);
   PendingLoads.clear();
   DAG.setRoot(Root);
   return Root;
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -9287,6 +9287,18 @@
   checkForCycles(Node);
 }
 
+void SelectionDAG::splitAcrossTokenFactors(const SDLoc &DL,
+                                           SmallVector<SDValue, 8> &Vals) {
+  size_t Limit = std::numeric_limits<decltype(SDNode::NumOperands)>::max();
+  while (Vals.size() > Limit) {
+    unsigned SliceIdx = Vals.size() - Limit;
+    auto ExtractedTFs = ArrayRef<SDValue>(Vals).slice(SliceIdx, Limit);
+    SDValue NewTF = getNode(ISD::TokenFactor, DL, MVT::Other, ExtractedTFs);
+    Vals.erase(Vals.begin() + SliceIdx, Vals.end());
+    Vals.emplace_back(NewTF);
+  }
+}
+
 #ifndef NDEBUG
 static void checkForCyclesHelper(const SDNode *N,
                                  SmallPtrSetImpl<const SDNode*> &Visited,
Index: llvm/include/llvm/CodeGen/SelectionDAG.h
===================================================================
--- llvm/include/llvm/CodeGen/SelectionDAG.h
+++ llvm/include/llvm/CodeGen/SelectionDAG.h
@@ -1154,6 +1154,12 @@
                                SDValue Op3, SDValue Op4, SDValue Op5);
   SDNode *UpdateNodeOperands(SDNode *N, ArrayRef<SDValue> Ops);
 
+  /// If \p Vals contains 64k values or more, move values into new
+  /// TokenFactors in 64k-1 blocks, until \p Vals contains less than 64k values.
+  /// Use this function for operand lists exceeding the maximum number of
+  /// operands for SDValue nodes.
+  void splitAcrossTokenFactors(const SDLoc &DL, SmallVector<SDValue, 8> &Vals);
+
   /// *Mutate* the specified machine node's memory references to the provided
   /// list.
   void setNodeMemRefs(MachineSDNode *N,


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