Add convenient helper for win64 check. Simplify things slightly.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48691 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86CallingConv.td b/lib/Target/X86/X86CallingConv.td
index 3206e18..d4f4e26 100644
--- a/lib/Target/X86/X86CallingConv.td
+++ b/lib/Target/X86/X86CallingConv.td
@@ -101,8 +101,7 @@
 // This is the root return-value convention for the X86-64 backend.
 def RetCC_X86_64 : CallingConv<[
   // Mingw64 and native Win64 use Win64 CC
-  CCIfSubtarget<"isTargetMingw()", CCDelegateTo<RetCC_X86_Win64_C>>,
-  CCIfSubtarget<"isTargetWindows()", CCDelegateTo<RetCC_X86_Win64_C>>,
+  CCIfSubtarget<"isTargetWin64()", CCDelegateTo<RetCC_X86_Win64_C>>,
 
   // Otherwise, drop to normal X86-64 CC
   CCDelegateTo<RetCC_X86_64_C>