Use the subtarget reference that we already have

llvm-svn: 253244
diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 394151b..3c557fe 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -2568,8 +2568,7 @@
   // not taking a chance at messing with them.
   // I.e., unless this block is already an exit block, we can't use
   // it as an epilogue.
-  if (MBB.getParent()->getSubtarget<X86Subtarget>().isTargetWin64() &&
-      !MBB.succ_empty() && !MBB.isReturnBlock())
+  if (STI.isTargetWin64() && !MBB.succ_empty() && !MBB.isReturnBlock())
     return false;
 
   if (canUseLEAForSPInEpilogue(*MBB.getParent()))