R600/SI: add folding helper

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176100 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/R600/SIISelLowering.cpp

@@ -357,3 +357,9 @@ SDValue SITargetLowering::PerformDAGCombine(SDNode *N,
   }
   return SDValue();
 }
+
+SDNode *SITargetLowering::PostISelFolding(MachineSDNode *Node,
+                                          SelectionDAG &DAG) const {
+  // TODO: Implement immediate folding
+  return Node;
+}