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/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 62c396e..475bb82 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -263,7 +263,7 @@
 
   const ConstantInt *NewVal = &Val;
   if (Ty.getSizeInBits() != Val.getBitWidth())
-    NewVal = ConstantInt::get(MF->getFunction()->getContext(),
+    NewVal = ConstantInt::get(MF->getFunction().getContext(),
                               Val.getValue().sextOrTrunc(Ty.getSizeInBits()));
 
   return buildInstr(TargetOpcode::G_CONSTANT).addDef(Res).addCImm(NewVal);
@@ -271,7 +271,7 @@
 
 MachineInstrBuilder MachineIRBuilder::buildConstant(unsigned Res,
                                                     int64_t Val) {
-  auto IntN = IntegerType::get(MF->getFunction()->getContext(),
+  auto IntN = IntegerType::get(MF->getFunction().getContext(),
                                MRI->getType(Res).getSizeInBits());
   ConstantInt *CI = ConstantInt::get(IntN, Val, true);
   return buildConstant(Res, *CI);