[PowerPC] Fix the int2fp(fp2int(x)) DAGCombine to ignore ppc_fp128

This DAGCombine was creating custom SDAG nodes with an illegal ppc_fp128
operand type because it was triggering on f64/f32 int2fp(fp2int(ppc_fp128 x)),
but shouldn't (it should only apply to f32/f64 types). The result was a crash.

llvm-svn: 245530
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 173269c..72d1d19 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -9991,6 +9991,9 @@
     if (Src.getValueType() == MVT::f32) {
       Src = DAG.getNode(ISD::FP_EXTEND, dl, MVT::f64, Src);
       DCI.AddToWorklist(Src.getNode());
+    } else if (Src.getValueType() != MVT::f64) {
+      // Make sure that we don't pick up a ppc_fp128 source value.
+      return SDValue();
     }
 
     unsigned FCTOp =