Switch all register list clients to the new MC*Iterator interface.

No functional change intended.

Sorry for the churn. The iterator classes are supposed to help avoid
giant commits like this one in the future. The TableGen-produced
register lists are getting quite large, and it may be necessary to
change the table representation.

This makes it possible to do so without changing all clients (again).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157854 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/Thumb2ITBlockPass.cpp b/lib/Target/ARM/Thumb2ITBlockPass.cpp
index ecb4c2f..3fce121 100644
--- a/lib/Target/ARM/Thumb2ITBlockPass.cpp
+++ b/lib/Target/ARM/Thumb2ITBlockPass.cpp
@@ -76,16 +76,14 @@
   for (unsigned i = 0, e = LocalUses.size(); i != e; ++i) {
     unsigned Reg = LocalUses[i];
     Uses.insert(Reg);
-    for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-         *Subreg; ++Subreg)
+    for (MCSubRegIterator Subreg(Reg, TRI); Subreg.isValid(); ++Subreg)
       Uses.insert(*Subreg);
   }
 
   for (unsigned i = 0, e = LocalDefs.size(); i != e; ++i) {
     unsigned Reg = LocalDefs[i];
     Defs.insert(Reg);
-    for (const uint16_t *Subreg = TRI->getSubRegisters(Reg);
-         *Subreg; ++Subreg)
+    for (MCSubRegIterator Subreg(Reg, TRI); Subreg.isValid(); ++Subreg)
       Defs.insert(*Subreg);
     if (Reg == ARM::CPSR)
       continue;