[X86] Enable shrink-wrapping by default, but keep it disabled for stack frames
without a frame pointer when unwind may happen.
This is a workaround for a bug in the way we emit the CFI directives for
frameless unwind information. See PR25614.

llvm-svn: 255175
diff --git a/llvm/lib/Target/X86/X86FrameLowering.h b/llvm/lib/Target/X86/X86FrameLowering.h
index 68dc8ed..3ab41b4 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.h
+++ b/llvm/lib/Target/X86/X86FrameLowering.h
@@ -134,6 +134,9 @@
   /// \p MBB will be correctly handled by the target.
   bool canUseAsEpilogue(const MachineBasicBlock &MBB) const override;
 
+  /// Returns true if the target will correctly handle shrink wrapping.
+  bool enableShrinkWrapping(const MachineFunction &MF) const override;
+
   /// convertArgMovsToPushes - This method tries to convert a call sequence
   /// that uses sub and mov instructions to put the argument onto the stack
   /// into a series of pushes.