[DAGCombiner] visitIMINMAX - use general SelectionDAG::FoldConstantArithmetic

This handles all the constant splat / opaque testing for us instead of the ConstantSDNode variant where we have to do it ourselves.

Author: RKSimon

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -4321,26 +4321,24 @@ SDValue DAGCombiner::visitIMINMAX(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
   EVT VT = N0.getValueType();
+  unsigned Opcode = N->getOpcode();
 
   // fold vector ops
   if (VT.isVector())
     if (SDValue FoldedVOp = SimplifyVBinOp(N))
       return FoldedVOp;
 
   // fold operation with constant operands.
-  ConstantSDNode *N0C = getAsNonOpaqueConstant(N0);
-  ConstantSDNode *N1C = getAsNonOpaqueConstant(N1);
-  if (N0C && N1C)
-    return DAG.FoldConstantArithmetic(N->getOpcode(), SDLoc(N), VT, N0C, N1C);
+  if (SDValue C = DAG.FoldConstantArithmetic(Opcode, SDLoc(N), VT, {N0, N1}))
+    return C;
 
   // canonicalize constant to RHS
   if (DAG.isConstantIntBuildVectorOrConstantInt(N0) &&
-     !DAG.isConstantIntBuildVectorOrConstantInt(N1))
+      !DAG.isConstantIntBuildVectorOrConstantInt(N1))
     return DAG.getNode(N->getOpcode(), SDLoc(N), VT, N1, N0);
 
   // Is sign bits are zero, flip between UMIN/UMAX and SMIN/SMAX.
   // Only do this if the current op isn't legal and the flipped is.
-  unsigned Opcode = N->getOpcode();
   if (!TLI.isOperationLegal(Opcode, VT) &&
       (N0.isUndef() || DAG.SignBitIsZero(N0)) &&
       (N1.isUndef() || DAG.SignBitIsZero(N1))) {