make it possible to custom lower TRUNCATE (needed for the CellSPU target)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60409 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 9c57457..cd90f67 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -3904,6 +3904,11 @@
     case Legal:
       Tmp1 = LegalizeOp(Node->getOperand(0));
       Result = DAG.UpdateNodeOperands(Result, Tmp1);
+      if (TLI.getOperationAction(Node->getOpcode(), Node->getValueType(0)) ==
+          TargetLowering::Custom) {
+        Tmp1 = TLI.LowerOperation(Result, DAG);
+        if (Tmp1.getNode()) Result = Tmp1;
+      }
       break;
     case Expand:
       ExpandOp(Node->getOperand(0), Tmp1, Tmp2);