Merge branch 'upstream' into merge-20120305

Conflicts:
	lib/Support/Atomic.cpp

Change-Id: I563b3bc2a82942ccbae5bed42e53b9149a8bf3a0

1 files changed, 10 insertions, 4 deletions

diff --git a/lib/Transforms/IPO/ConstantMerge.cpp b/lib/Transforms/IPO/ConstantMerge.cpp
index c3ecb7a..d8fae8a 100644
--- a/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/lib/Transforms/IPO/ConstantMerge.cpp
@@ -140,18 +140,24 @@ bool ConstantMerge::runOnModule(Module &M) {
           UsedGlobals.count(GV))
         continue;
 
+      // This transformation is legal for weak ODR globals in the sense it
+      // doesn't change semantics, but we really don't want to perform it
+      // anyway; it's likely to pessimize code generation, and some tools
+      // (like the Darwin linker in cases involving CFString) don't expect it.
+      if (GV->isWeakForLinker())
+        continue;
+
       Constant *Init = GV->getInitializer();
 
       // Check to see if the initializer is already known.
       PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
       GlobalVariable *&Slot = CMap[Pair];
 
-      // If this is the first constant we find or if the old on is local,
-      // replace with the current one. It the current is externally visible
+      // If this is the first constant we find or if the old one is local,
+      // replace with the current one. If the current is externally visible
       // it cannot be replace, but can be the canonical constant we merge with.
-      if (Slot == 0 || IsBetterCannonical(*GV, *Slot)) {
+      if (Slot == 0 || IsBetterCannonical(*GV, *Slot))
         Slot = GV;
-      }
     }
 
     // Second: identify all globals that can be merged together, filling in