MachineFunction: Return reference from getFunction(); NFC

The Function can never be nullptr so we can return a reference.

llvm-svn: 320884
diff --git a/llvm/lib/CodeGen/MachineCombiner.cpp b/llvm/lib/CodeGen/MachineCombiner.cpp
index 4f40fde..702d212 100644
--- a/llvm/lib/CodeGen/MachineCombiner.cpp
+++ b/llvm/lib/CodeGen/MachineCombiner.cpp
@@ -548,7 +548,7 @@
   MLI = &getAnalysis<MachineLoopInfo>();
   Traces = &getAnalysis<MachineTraceMetrics>();
   MinInstr = nullptr;
-  OptSize = MF.getFunction()->optForSize();
+  OptSize = MF.getFunction().optForSize();
 
   DEBUG(dbgs() << getPassName() << ": " << MF.getName() << '\n');
   if (!TII->useMachineCombiner()) {