The function live-out registers must be live at all function returns,
and %RCX is only used by eh.return. When a function also has a normal
return, only %RAX holds a return value.
This fixes PR13188.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159116 91177308-0d34-0410-b5e6-96231b3b80d8
