diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -886,8 +886,9 @@
               [, partition "name"]
 
 The linkage must be one of ``private``, ``internal``, ``linkonce``, ``weak``,
-``linkonce_odr``, ``weak_odr``, ``external``. Note that some system linkers
-might not correctly handle dropping a weak symbol that is aliased.
+``linkonce_odr``, ``weak_odr``, ``external``, ``available_externally``. Note
+that some system linkers might not correctly handle dropping a weak symbol that
+is aliased.
 
 Aliases that are not ``unnamed_addr`` are guaranteed to have the same address as
 the aliasee expression. ``unnamed_addr`` ones are only guaranteed to point
diff --git a/llvm/include/llvm/IR/GlobalAlias.h b/llvm/include/llvm/IR/GlobalAlias.h
--- a/llvm/include/llvm/IR/GlobalAlias.h
+++ b/llvm/include/llvm/IR/GlobalAlias.h
@@ -93,8 +93,8 @@
   }
 
   static bool isValidLinkage(LinkageTypes L) {
-    return isExternalLinkage(L) || isLocalLinkage(L) ||
-      isWeakLinkage(L) || isLinkOnceLinkage(L);
+    return isExternalLinkage(L) || isLocalLinkage(L) || isWeakLinkage(L) ||
+           isLinkOnceLinkage(L) || isAvailableExternallyLinkage(L);
   }
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -816,8 +816,13 @@
 void Verifier::visitAliaseeSubExpr(SmallPtrSetImpl<const GlobalAlias*> &Visited,
                                    const GlobalAlias &GA, const Constant &C) {
   if (const auto *GV = dyn_cast<GlobalValue>(&C)) {
-    Check(!GV->isDeclarationForLinker(), "Alias must point to a definition",
-          &GA);
+    if (GV->hasAvailableExternallyLinkage()) {
+      Check(GA.hasAvailableExternallyLinkage(),
+            "available_externally aliasee requires available_externally alias",
+            &GA);
+    } else {
+      Check(!GV->isDeclaration(), "Alias must point to a definition", &GA);
+    }
 
     if (const auto *GA2 = dyn_cast<GlobalAlias>(GV)) {
       Check(Visited.insert(GA2).second, "Aliases cannot form a cycle", &GA);
@@ -846,7 +851,7 @@
 void Verifier::visitGlobalAlias(const GlobalAlias &GA) {
   Check(GlobalAlias::isValidLinkage(GA.getLinkage()),
         "Alias should have private, internal, linkonce, weak, linkonce_odr, "
-        "weak_odr, or external linkage!",
+        "weak_odr, external, or available_externally linkage!",
         &GA);
   const Constant *Aliasee = GA.getAliasee();
   Check(Aliasee, "Aliasee cannot be NULL!", &GA);
diff --git a/llvm/test/Verifier/alias.ll b/llvm/test/Verifier/alias.ll
--- a/llvm/test/Verifier/alias.ll
+++ b/llvm/test/Verifier/alias.ll
@@ -1,4 +1,4 @@
-; RUN:  not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+; RUN:  not llvm-as %s -o /dev/null 2>&1 | FileCheck %s --implicit-check-not=alias --implicit-check-not=Alias
 
 
 declare void @f()
@@ -15,7 +15,7 @@
   ret void
 }
 @fa2 = alias void(), void()* @f2
-; CHECK: Alias must point to a definition
+; CHECK: available_externally aliasee requires available_externally alias
 ; CHECK-NEXT: @fa2
 
 @test2_a = alias i32, i32* @test2_b
@@ -31,3 +31,7 @@
 @test3_c = alias i32, i32* @test3_b
 ; CHECK: Alias cannot point to an interposable alias
 ; CHECK-NEXT: i32* @test3_c
+
+@test4_a = available_externally alias i32, i32* @test3_a
+@test4_b = available_externally alias void(), void()* @f2
+@test4_c = available_externally alias i32, i32* @test4_a