From 832b2a9cd8870211bf2d347d7b435beacbb06c8d Mon Sep 17 00:00:00 2001
From: Anton Korobeynikov <asl@math.spbu.ru>
Date: Tue, 9 Sep 2008 18:23:48 +0000
Subject: [PATCH] Fix incorrect linker behaviour: we shouldn't resolve weak
 aliases.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55997 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/GlobalAlias.h |  6 ++++--
 lib/Linker/LinkModules.cpp |  4 ++--
 lib/VMCore/Globals.cpp     | 10 +++++++++-
 3 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/include/llvm/GlobalAlias.h b/include/llvm/GlobalAlias.h
index 6dba21bf609..1081fc675fc 100644
--- a/include/llvm/GlobalAlias.h
+++ b/include/llvm/GlobalAlias.h
@@ -76,8 +76,10 @@ public:
 
   /// resolveAliasedGlobal() - This method tries to ultimately resolve the alias
   /// by going through the aliasing chain and trying to find the very last
-  /// global. Returns NULL if a cycle was found.
-  const GlobalValue* resolveAliasedGlobal() const;
+  /// global. Returns NULL if a cycle was found. If traverseWeak is true, then
+  /// the whole chain aliasing chain is traversed, otherwise - only strong
+  /// aliases.
+  const GlobalValue* resolveAliasedGlobal(bool traverseWeak = true) const;
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static inline bool classof(const GlobalAlias *) { return true; }
diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index 3b319c28402..f4ebe6b10c0 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -1169,8 +1169,8 @@ static bool LinkAppendingVars(Module *M,
 static bool ResolveAliases(Module *Dest) {
   for (Module::alias_iterator I = Dest->alias_begin(), E = Dest->alias_end();
        I != E; ++I)
-    if (const GlobalValue *GV = I->resolveAliasedGlobal())
-      if (!GV->isDeclaration())
+    if (const GlobalValue *GV = I->resolveAliasedGlobal(/*traverseWeak*/ false))
+      if (GV != I && !GV->isDeclaration())
         I->replaceAllUsesWith(const_cast<GlobalValue*>(GV));
 
   return false;
diff --git a/lib/VMCore/Globals.cpp b/lib/VMCore/Globals.cpp
index 7340f1532f5..e55cb5a5ac5 100644
--- a/lib/VMCore/Globals.cpp
+++ b/lib/VMCore/Globals.cpp
@@ -248,13 +248,21 @@ const GlobalValue *GlobalAlias::getAliasedGlobal() const {
   return 0;
 }
 
-const GlobalValue *GlobalAlias::resolveAliasedGlobal() const {
+const GlobalValue *GlobalAlias::resolveAliasedGlobal(bool traverseWeak) const {
   SmallPtrSet<const GlobalValue*, 3> Visited;
 
+  // Check if we need to stop early.
+  if (!traverseWeak && hasWeakLinkage())
+    return this;
+
   const GlobalValue *GV = getAliasedGlobal();
   Visited.insert(GV);
 
+  // Iterate over aliasing chain, stopping on weak alias if necessary.
   while (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV)) {
+    if (traverseWeak && GA->hasWeakLinkage())
+      break;
+
     GV = GA->getAliasedGlobal();
 
     if (!Visited.insert(GV))
-- 
2.34.1