From 69ca26cc9732502b6c218aec9098174f87e75900 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Mon, 11 Aug 2014 17:07:34 +0000
Subject: [PATCH] Fix use of uninitialized variable.

Fixes linking bitcode files that use the new style comdats for constructors
with ones that don't.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215364 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Linker/LinkModules.cpp               |  8 ++++++--
 test/Linker/Inputs/constructor-comdat.ll |  7 +++++++
 test/Linker/constructor-comdat.ll        | 13 +++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 test/Linker/Inputs/constructor-comdat.ll
 create mode 100644 test/Linker/constructor-comdat.ll

diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index 1f4c3c13238..1748af47402 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -644,15 +644,19 @@ bool ModuleLinker::computeResultingSelectionKind(StringRef ComdatName,
 bool ModuleLinker::getComdatResult(const Comdat *SrcC,
                                    Comdat::SelectionKind &Result,
                                    bool &LinkFromSrc) {
+  Comdat::SelectionKind SSK = SrcC->getSelectionKind();
   StringRef ComdatName = SrcC->getName();
   Module::ComdatSymTabType &ComdatSymTab = DstM->getComdatSymbolTable();
   Module::ComdatSymTabType::iterator DstCI = ComdatSymTab.find(ComdatName);
 
-  if (DstCI == ComdatSymTab.end())
+  if (DstCI == ComdatSymTab.end()) {
+    // Use the comdat if it is only available in one of the modules.
+    LinkFromSrc = true;
+    Result = SSK;
     return false;
+  }
 
   const Comdat *DstC = &DstCI->second;
-  Comdat::SelectionKind SSK = SrcC->getSelectionKind();
   Comdat::SelectionKind DSK = DstC->getSelectionKind();
   return computeResultingSelectionKind(ComdatName, SSK, DSK, Result,
                                        LinkFromSrc);
diff --git a/test/Linker/Inputs/constructor-comdat.ll b/test/Linker/Inputs/constructor-comdat.ll
new file mode 100644
index 00000000000..b5f23da9035
--- /dev/null
+++ b/test/Linker/Inputs/constructor-comdat.ll
@@ -0,0 +1,7 @@
+define weak_odr void @_ZN3fooIiEC2Ev() {
+  ret void
+}
+
+define weak_odr void @_ZN3fooIiEC1Ev() {
+  ret void
+}
diff --git a/test/Linker/constructor-comdat.ll b/test/Linker/constructor-comdat.ll
new file mode 100644
index 00000000000..42e2d83424a
--- /dev/null
+++ b/test/Linker/constructor-comdat.ll
@@ -0,0 +1,13 @@
+; RUN: llvm-link %s %p/Inputs/constructor-comdat.ll -S -o - 2>&1 | FileCheck %s
+; RUN: llvm-link %p/Inputs/constructor-comdat.ll %s -S -o - 2>&1 | FileCheck %s
+
+$_ZN3fooIiEC5Ev = comdat any
+; CHECK: $_ZN3fooIiEC5Ev = comdat any
+
+@_ZN3fooIiEC1Ev = weak_odr alias void ()* @_ZN3fooIiEC2Ev
+; CHECK: @_ZN3fooIiEC1Ev = weak_odr alias void ()* @_ZN3fooIiEC2Ev
+
+; CHECK: define weak_odr void @_ZN3fooIiEC2Ev() comdat $_ZN3fooIiEC5Ev {
+define weak_odr void @_ZN3fooIiEC2Ev() comdat $_ZN3fooIiEC5Ev {
+  ret void
+}