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;
diff --git a/llvm/test/Transforms/PartiallyInlineLibCalls/X86/musttail.ll b/llvm/test/Transforms/PartiallyInlineLibCalls/X86/musttail.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/PartiallyInlineLibCalls/X86/musttail.ll
@@ -0,0 +1,14 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -partially-inline-libcalls -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+; RUN: opt -S -passes=partially-inline-libcalls -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+
+define double @foo(double %x) {
+; CHECK-LABEL: @foo(
+; CHECK-NEXT:    [[R:%.*]] = musttail call double @sqrt(double [[X:%.*]])
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = musttail call double @sqrt(double %x)
+  ret double %r
+}
+
+declare double @sqrt(double)