[SelectionDAG] Add getTokenFactor, which splits nodes with > 64k operands.

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

Differential Revision: https://reviews.llvm.org/D56739

llvm-svn: 351552

Author: fhahn

llvm/include/llvm/CodeGen/SelectionDAG.h

@@ -1154,6 +1154,11 @@ class SelectionDAG {
                                SDValue Op3, SDValue Op4, SDValue Op5);
   SDNode *UpdateNodeOperands(SDNode *N, ArrayRef<SDValue> Ops);
 
+  /// Creates a new TokenFactor containing \p Vals. If \p Vals contains 64k
+  /// values or more, move values into new TokenFactors in 64k-1 blocks, until
+  /// the final TokenFactor has less than 64k operands.
+  SDValue getTokenFactor(const SDLoc &DL, SmallVectorImpl<SDValue> &Vals);
+
   /// *Mutate* the specified machine node's memory references to the provided
   /// list.
   void setNodeMemRefs(MachineSDNode *N,

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -9286,6 +9286,19 @@ void SelectionDAG::createOperands(SDNode *Node, ArrayRef<SDValue> Vals) {
   checkForCycles(Node);
 }
 
+SDValue SelectionDAG::getTokenFactor(const SDLoc &DL,
+                                     SmallVectorImpl<SDValue> &Vals) {
+  size_t Limit = SDNode::getMaxNumOperands();
+  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);
+  }
+  return getNode(ISD::TokenFactor, DL, MVT::Other, Vals);
+}
+
 #ifndef NDEBUG
 static void checkForCyclesHelper(const SDNode *N,
                                  SmallPtrSetImpl<const SDNode*> &Visited,

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -1032,19 +1032,7 @@ SDValue SelectionDAGBuilder::getRoot() {
   }
 
   // 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 = SDNode::getMaxNumOperands();
-  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);
+  SDValue Root = DAG.getTokenFactor(getCurSDLoc(), PendingLoads);
   PendingLoads.clear();
   DAG.setRoot(Root);
   return Root;