diff --git a/llvm/lib/Transforms/IPO/Attributor.cpp b/llvm/lib/Transforms/IPO/Attributor.cpp
--- a/llvm/lib/Transforms/IPO/Attributor.cpp
+++ b/llvm/lib/Transforms/IPO/Attributor.cpp
@@ -1146,6 +1146,9 @@
   if (!AssociatedFunction)
     return false;
 
+  if (AssociatedFunction->isDeclaration())
+    return false;
+
   // TODO: use the function scope once we have call site AAReturnedValues.
   const IRPosition &QueryIRP = IRPosition::function(*AssociatedFunction);
   const auto *LivenessAA =
diff --git a/llvm/unittests/Transforms/IPO/AttributorTest.cpp b/llvm/unittests/Transforms/IPO/AttributorTest.cpp
--- a/llvm/unittests/Transforms/IPO/AttributorTest.cpp
+++ b/llvm/unittests/Transforms/IPO/AttributorTest.cpp
@@ -75,8 +75,16 @@
 
 TEST_F(AttributorTestBase, AAReachabilityTest) {
   const char *ModuleString = R"(
-    declare void @func4()
-    declare void @func3()
+    @x = global i32 0
+    define void @func4() {
+      store i32 0, i32* @x
+      ret void
+    }
+
+    define void @func3() {
+      store i32 0, i32* @x
+      ret void
+    }
 
     define void @func2() {
     entry: