diff --git a/llvm/lib/Transforms/Scalar/PartiallyInlineLibCalls.cpp b/llvm/lib/Transforms/Scalar/PartiallyInlineLibCalls.cpp
--- a/llvm/lib/Transforms/Scalar/PartiallyInlineLibCalls.cpp
+++ b/llvm/lib/Transforms/Scalar/PartiallyInlineLibCalls.cpp
@@ -125,6 +125,9 @@
       if (Call->isNoBuiltin() || Call->isStrictFP())
         continue;
 
+      if (Call->isMustTailCall())
+        continue;
+
       // Skip if function either has local linkage or is not a known library
       // function.
       LibFunc LF;