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/OptimizePHIs.cpp b/llvm/lib/CodeGen/OptimizePHIs.cpp
index 50968ef..4973802 100644
--- a/llvm/lib/CodeGen/OptimizePHIs.cpp
+++ b/llvm/lib/CodeGen/OptimizePHIs.cpp
@@ -139,10 +139,8 @@
   if (PHIsInCycle.size() == 16)
     return false;
 
-  for (MachineRegisterInfo::use_instr_iterator I = MRI->use_instr_begin(DstReg),
-         E = MRI->use_instr_end(); I != E; ++I) {
-    MachineInstr *UseMI = &*I;
-    if (!UseMI->isPHI() || !IsDeadPHICycle(UseMI, PHIsInCycle))
+  for (MachineInstr &UseMI : MRI->use_instructions(DstReg)) {
+    if (!UseMI.isPHI() || !IsDeadPHICycle(&UseMI, PHIsInCycle))
       return false;
   }