[PowerPC] Improve int_to_fp(fp_to_int(x)) combining

The old target DAG combine that allowed for performing int_to_fp(fp_to_int(x))
without a load/store pair is updated here with support for unsigned integers,
and to support single-precision values without a third rounding step, on newer
cores with the appropriate instructions.

llvm-svn: 225248
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index dd2431e..ee946e6 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -748,6 +748,7 @@
 
     SDValue DAGCombineExtBoolTrunc(SDNode *N, DAGCombinerInfo &DCI) const;
     SDValue DAGCombineTruncBoolExt(SDNode *N, DAGCombinerInfo &DCI) const;
+    SDValue combineFPToIntToFP(SDNode *N, DAGCombinerInfo &DCI) const;
 
     SDValue getRsqrtEstimate(SDValue Operand, DAGCombinerInfo &DCI,
                              unsigned &RefinementSteps,