Inliner: Don't mark notail calls with the 'tail' attribute

enum TailCallKind { TCK_None = 0, TCK_Tail = 1, TCK_MustTail = 2,
                    TCK_NoTail = 3 };

TCK_NoTail is greater than TCK_Tail so taking the min does not do the
correct thing.

rdar://35639547

llvm-svn: 319075
diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 23a72e8..15a8bf2 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1850,7 +1850,8 @@
         //    f ->          g -> musttail f  ==>  f ->          f
         //    f ->          g ->     tail f  ==>  f ->          f
         CallInst::TailCallKind ChildTCK = CI->getTailCallKind();
-        ChildTCK = std::min(CallSiteTailKind, ChildTCK);
+        if (ChildTCK != CallInst::TCK_NoTail)
+          ChildTCK = std::min(CallSiteTailKind, ChildTCK);
         CI->setTailCallKind(ChildTCK);
         InlinedMustTailCalls |= CI->isMustTailCall();