ARM target code clean up. Check for iOS, not Darwin where it makes sense.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146981 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMSubtarget.cpp b/lib/Target/ARM/ARMSubtarget.cpp
index 2cb5ab9..074cd4c 100644
--- a/lib/Target/ARM/ARMSubtarget.cpp
+++ b/lib/Target/ARM/ARMSubtarget.cpp
@@ -108,13 +108,13 @@
   if (isAAPCS_ABI())
     stackAlignment = 8;
 
-  if (!isTargetDarwin())
+  if (!isTargetIOS())
     UseMovt = hasV6T2Ops();
   else {
     IsR9Reserved = ReserveR9 | !HasV6Ops;
     UseMovt = DarwinUseMOVT && hasV6T2Ops();
     const Triple &T = getTargetTriple();
-    SupportsTailCall = T.getOS() == Triple::IOS && !T.isOSVersionLT(5, 0);
+    SupportsTailCall = !T.isOSVersionLT(5, 0);
   }
 
   if (!isThumb() || hasThumb2())