Switch a number of loops in lib/CodeGen over to range-based for-loops, now that
the MachineRegisterInfo iterators are compatible with it.

llvm-svn: 204075
diff --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp
index cff8031..0e9df58 100644
--- a/llvm/lib/CodeGen/PHIElimination.cpp
+++ b/llvm/lib/CodeGen/PHIElimination.cpp
@@ -198,10 +198,8 @@
 /// This includes registers with no defs.
 static bool isImplicitlyDefined(unsigned VirtReg,
                                 const MachineRegisterInfo *MRI) {
-  for (MachineRegisterInfo::def_instr_iterator
-       DI = MRI->def_instr_begin(VirtReg), DE = MRI->def_instr_end();
-       DI != DE; ++DI)
-    if (!DI->isImplicitDef())
+  for (MachineInstr &DI : MRI->def_instructions(VirtReg))
+    if (!DI.isImplicitDef())
       return false;
   return true;
 }