From 96bc72cb3b68bf026af9e88410dcefb969e4dd68 Mon Sep 17 00:00:00 2001
From: Mehdi Amini <mehdi.amini@apple.com>
Date: Sun, 15 May 2016 05:49:47 +0000
Subject: [PATCH] ThinLTOCodeGenerator: fix race condition found using TSAN

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 269588
---
 lib/LTO/ThinLTOCodeGenerator.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/LTO/ThinLTOCodeGenerator.cpp b/lib/LTO/ThinLTOCodeGenerator.cpp
index 33d0a0cd920..2867c730125 100644
--- a/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -884,6 +884,11 @@ void ThinLTOCodeGenerator::run() {
   auto GUIDPreservedSymbols =
       computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
 
+  // Make sure that every module has an entry in the ExportLists to enable
+  // threaded access to this map below
+  for (auto &DefinedGVSummaries : ModuleToDefinedGVSummaries)
+    ExportLists[DefinedGVSummaries.first()];
+
   // Parallel optimizer + codegen
   {
     ThreadPool Pool(ThreadCount);