[SelectionDAG] Add static getMaxNumOperands function to SDNode.

Summary:
Use this helper to make sure we use the same value at various places.
This will likely be needed at more places were we currently crash
because we use more operands than possible.

Also makes it easier to change in the future.

Reviewers: RKSimon, craig.topper, efriedma, aemerson

Reviewed By: RKSimon

Subscribers: hiraditya, arsenm, llvm-commits

Differential Revision: https://reviews.llvm.org/D56859

llvm-svn: 351537

llvm/include/llvm/CodeGen/SelectionDAGNodes.h

@@ -898,6 +898,11 @@ public:
   /// Return the number of values used by this operation.
   unsigned getNumOperands() const { return NumOperands; }
 
+  /// Return the maximum number of operands that a SDNode can hold.
+  static constexpr size_t getMaxNumOperands() {
+    return std::numeric_limits<decltype(SDNode::NumOperands)>::max();
+  }
+
   /// Helper method returns the integer value of a ConstantSDNode operand.
   inline uint64_t getConstantOperandVal(unsigned Num) const;
 

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -9266,8 +9266,7 @@ SDNode *SelectionDAG::isConstantFPBuildVectorOrConstantFP(SDValue N) {
 
 void SelectionDAG::createOperands(SDNode *Node, ArrayRef<SDValue> Vals) {
   assert(!Node->OperandList && "Node already has operands");
-  assert(std::numeric_limits<decltype(SDNode::NumOperands)>::max() >=
-             Vals.size() &&
+  assert(SDNode::getMaxNumOperands() >= Vals.size() &&
          "too many operands to fit into SDNode");
   SDUse *Ops = OperandRecycler.allocate(
       ArrayRecycler<SDUse>::Capacity::get(Vals.size()), OperandAllocator);

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -1035,7 +1035,7 @@ SDValue SelectionDAGBuilder::getRoot() {
   // 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;
+  size_t Limit = SDNode::getMaxNumOperands();
   while (PendingLoads.size() > Limit) {
     unsigned SliceIdx = PendingLoads.size() - Limit;
     auto ExtractedTFs = ArrayRef<SDValue>(PendingLoads).slice(SliceIdx, Limit);