[llvm] r304300 - Fix assertion when merging multiple empty AttributeLists

[Reid Kleckner via llvm-commits]

Author: rnk
Date: Wed May 31 09:24:06 2017
New Revision: 304300

URL: http://llvm.org/viewvc/llvm-project?rev=304300&view=rev
Log:
Fix assertion when merging multiple empty AttributeLists

Patch by Nicholas Wilson!

Differential Revision: https://reviews.llvm.org/D33627

Modified:
    llvm/trunk/lib/IR/Attributes.cpp
    llvm/trunk/unittests/IR/AttributesTest.cpp

Modified: llvm/trunk/lib/IR/Attributes.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Attributes.cpp?rev=304300&r1=304299&r2=304300&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Attributes.cpp (original)
+++ llvm/trunk/lib/IR/Attributes.cpp Wed May 31 09:24:06 2017
@@ -1006,6 +1006,10 @@ AttributeList AttributeList::get(LLVMCon
   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;

Modified: llvm/trunk/unittests/IR/AttributesTest.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/unittests/IR/AttributesTest.cpp?rev=304300&r1=304299&r2=304300&view=diff
==============================================================================
--- llvm/trunk/unittests/IR/AttributesTest.cpp (original)
+++ llvm/trunk/unittests/IR/AttributesTest.cpp Wed May 31 09:24:06 2017
@@ -82,4 +82,11 @@ TEST(Attributes, AddMatchingAlignAttr) {
   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