CodeGen: Change MachineInstr to use MachineInstr&, NFC

Change MachineInstr API to prefer MachineInstr& over MachineInstr*
whenever the parameter is expected to be non-null.  Slowly inching
toward being able to fix PR26753.

llvm-svn: 262149
diff --git a/llvm/lib/CodeGen/IfConversion.cpp b/llvm/lib/CodeGen/IfConversion.cpp
index 9e898db..a4ce9c6 100644
--- a/llvm/lib/CodeGen/IfConversion.cpp
+++ b/llvm/lib/CodeGen/IfConversion.cpp
@@ -580,7 +580,7 @@
       if (FIB == FIE)
         break;
     }
-    if (!TIB->isIdenticalTo(FIB))
+    if (!TIB->isIdenticalTo(*FIB))
       break;
     ++Dups1;
     ++TIB;
@@ -624,7 +624,7 @@
       if (FIE == FIB)
         break;
     }
-    if (!TIE->isIdenticalTo(FIE))
+    if (!TIE->isIdenticalTo(*FIE))
       break;
     ++Dups2;
     --TIE;