diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -414,6 +414,11 @@
 def TargetSupportsInitPriority : TargetSpec {
   let CustomCode = [{ !Target.getTriple().isOSzOS() }];
 }
+
+def TargetSupportsMustTail : TargetSpec {
+  let CustomCode = [{ !Target.getTriple().isWasm() || Target.hasFeature("tail-call") }];
+}
+
 // Attribute subject match rules that are used for #pragma clang attribute.
 //
 // A instance of AttrSubjectMatcherRule represents an individual match rule.
@@ -1433,7 +1438,7 @@
   let SimpleHandler = 1;
 }
 
-def MustTail : StmtAttr {
+def MustTail : StmtAttr, TargetSpecificAttr<TargetSupportsMustTail> {
   let Spellings = [Clang<"musttail">];
   let Documentation = [MustTailDocs];
   let Subjects = SubjectList<[ReturnStmt], ErrorDiag, "return statements">;