DAG: Add helper for testing constant values

[arsenm]

Summary

There are helpers for testing for constant or constant build_vector,
and for splat ConstantFP vectors, but not for a constantfp or
non-splat ConstantFP vector.

[RKSimon]

include/llvm/CodeGen/SelectionDAG.h

1368

Shouldn't that be \p N ?

[arsenm]

r290317

[arsenm]

include/llvm/CodeGen/SelectionDAG.h

1368

Yes, fixed

include/llvm/CodeGen/SelectionDAG.h

void ExtractVectorElements(SDValue Op, SmallVectorImpl<SDValue> &Args,
                              unsigned Start = 0, unsigned Count = 0);
 
   /// Compute the default alignment value for the given type.
   unsigned getEVTAlignment(EVT MemoryVT) const;
 
   /// Test whether the given value is a constant int or similar node.
   SDNode *isConstantIntBuildVectorOrConstantInt(SDValue N);
 
+  /// Test whether the given value is a constant FP or similar node.
+  SDNode *isConstantFPBuildVectorOrConstantFP(SDValue N);
+
+  /// \returns true if \p V is any kind of constant or build_vector of
+  /// constants, int or float. If a vector, it may not necessarily be a splat.
+  inline bool isConstantValueOfAnyType(SDValue N) {
+    return isConstantIntBuildVectorOrConstantInt(N) ||
+           isConstantFPBuildVectorOrConstantFP(N);
+  }
+
 private:
   void InsertNode(SDNode *N);
   bool RemoveNodeFromCSEMaps(SDNode *N);
   void AddModifiedNodeToCSEMaps(SDNode *N);
   SDNode *FindModifiedNodeSlot(SDNode *N, SDValue Op, void *&InsertPos);
   SDNode *FindModifiedNodeSlot(SDNode *N, SDValue Op1, SDValue Op2,
                                void *&InsertPos);
   SDNode *FindModifiedNodeSlot(SDNode *N, ArrayRef<SDValue> Ops,

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

SDNode *SelectionDAG::isConstantIntBuildVectorOrConstantInt(SDValue N) {
   // constant integer.
   if (GlobalAddressSDNode *GA = dyn_cast<GlobalAddressSDNode>(N))
     if (GA->getOpcode() == ISD::GlobalAddress &&
         TLI->isOffsetFoldingLegal(GA))
       return GA;
   return nullptr;
 }
 
+SDNode *SelectionDAG::isConstantFPBuildVectorOrConstantFP(SDValue N) {
+  if (isa<ConstantFPSDNode>(N))
+    return N.getNode();
+
+  if (ISD::isBuildVectorOfConstantFPSDNodes(N.getNode()))
+    return N.getNode();
+
+  return nullptr;
+}
+
 #ifndef NDEBUG
 static void checkForCyclesHelper(const SDNode *N,
                                  SmallPtrSetImpl<const SDNode*> &Visited,
                                  SmallPtrSetImpl<const SDNode*> &Checked,
                                  const llvm::SelectionDAG *DAG) {
   // If this node has already been checked, don't check it again.
   if (Checked.count(N))
     return;