Index: llvm/trunk/lib/IR/Attributes.cpp
===================================================================
--- llvm/trunk/lib/IR/Attributes.cpp
+++ llvm/trunk/lib/IR/Attributes.cpp
@@ -1006,6 +1006,10 @@
   for (AttributeList List : Attrs)
     MaxSize = std::max(MaxSize, List.getNumAttrSets());
 
+  // If every list was empty, there is no point in merging the lists.
+  if (MaxSize == 0)
+    return AttributeList();
+
   SmallVector<AttributeSet, 8> NewAttrSets(MaxSize);
   for (unsigned I = 0; I < MaxSize; ++I) {
     AttrBuilder CurBuilder;
Index: llvm/trunk/unittests/IR/AttributesTest.cpp
===================================================================
--- llvm/trunk/unittests/IR/AttributesTest.cpp
+++ llvm/trunk/unittests/IR/AttributesTest.cpp
@@ -82,4 +82,11 @@
   EXPECT_TRUE(AL.hasParamAttribute(0, Attribute::NonNull));
 }
 
+TEST(Attributes, EmptyGet) {
+  LLVMContext C;
+  AttributeList EmptyLists[] = {AttributeList(), AttributeList()};
+  AttributeList AL = AttributeList::get(C, EmptyLists);
+  EXPECT_TRUE(AL.isEmpty());
+}
+
 } // end anonymous namespace