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/Target/Hexagon/HexagonCFGOptimizer.cpp b/llvm/lib/Target/Hexagon/HexagonCFGOptimizer.cpp
index 6e43574..a22ac8c 100644
--- a/llvm/lib/Target/Hexagon/HexagonCFGOptimizer.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonCFGOptimizer.cpp
@@ -114,7 +114,7 @@
 }
 
 bool HexagonCFGOptimizer::runOnMachineFunction(MachineFunction &Fn) {
-  if (skipFunction(*Fn.getFunction()))
+  if (skipFunction(Fn.getFunction()))
     return false;
 
   // Loop over all of the basic blocks.