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/AMDGPU/SIShrinkInstructions.cpp b/llvm/lib/Target/AMDGPU/SIShrinkInstructions.cpp
index 874fbad..41f989a 100644
--- a/llvm/lib/Target/AMDGPU/SIShrinkInstructions.cpp
+++ b/llvm/lib/Target/AMDGPU/SIShrinkInstructions.cpp
@@ -286,7 +286,7 @@
 }
 
 bool SIShrinkInstructions::runOnMachineFunction(MachineFunction &MF) {
-  if (skipFunction(*MF.getFunction()))
+  if (skipFunction(MF.getFunction()))
     return false;
 
   MachineRegisterInfo &MRI = MF.getRegInfo();