diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -597,6 +597,8 @@
 }
 
 bool AttributeImpl::operator<(const AttributeImpl &AI) const {
+  if (this == &AI)
+    return false;
   // This sorts the attributes with Attribute::AttrKinds coming first (sorted
   // relative to their enum value) and then strings.
   if (isEnumAttribute()) {
diff --git a/llvm/unittests/IR/AttributesTest.cpp b/llvm/unittests/IR/AttributesTest.cpp
--- a/llvm/unittests/IR/AttributesTest.cpp
+++ b/llvm/unittests/IR/AttributesTest.cpp
@@ -44,6 +44,7 @@
   Attribute ByVal = Attribute::get(C, Attribute::ByVal, Type::getInt32Ty(C));
   EXPECT_FALSE(ByVal < Attribute::get(C, Attribute::ZExt));
   EXPECT_TRUE(ByVal < Align4);
+  EXPECT_FALSE(ByVal < ByVal);
 
   AttributeList ASs[] = {AttributeList::get(C, 2, Attribute::ZExt),
                          AttributeList::get(C, 1, Attribute::SExt)};