Use helper function to check for low registers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@138048 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 9658e08..58d01e8 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -3015,7 +3015,7 @@
       if (Reg == Rn)
         doesWriteback = false;
       // Anything other than a low register isn't legal here.
-      if (getARMRegisterNumbering(Reg) > 7)
+      if (!isARMLowRegister(Reg))
         return Error(Operands[4]->getStartLoc(),
                      "registers must be in range r0-r7");
     }