From 1d7cbdfc3d28d5db078b4a214f73b5bc633bdfbb Mon Sep 17 00:00:00 2001
From: Reid Kleckner <rnk@google.com>
Date: Wed, 31 May 2017 14:24:06 +0000
Subject: Fix assertion when merging multiple empty AttributeLists

Patch by Nicholas Wilson!

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

llvm-svn: 304300
---
 llvm/lib/IR/Attributes.cpp | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'llvm/lib/IR/Attributes.cpp')

diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index 19b7c302723..a6d1c9035af 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -1006,6 +1006,10 @@ AttributeList AttributeList::get(LLVMContext &C,
   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;
-- 
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