1 files changed, 67 insertions, 19 deletions

diff --git a/contrib/llvm/lib/Transforms/IPO/ConstantMerge.cpp b/contrib/llvm/lib/Transforms/IPO/ConstantMerge.cpp
index 64e8d79..a21efce 100644
--- a/contrib/llvm/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/contrib/llvm/lib/Transforms/IPO/ConstantMerge.cpp
@@ -33,7 +33,9 @@ STATISTIC(NumMerged, "Number of global constants merged");
 namespace {
   struct ConstantMerge : public ModulePass {
     static char ID; // Pass identification, replacement for typeid
-    ConstantMerge() : ModulePass(ID) {}
+    ConstantMerge() : ModulePass(ID) {
+      initializeConstantMergePass(*PassRegistry::getPassRegistry());
+    }
 
     // run - For this pass, process all of the globals in the module,
     // eliminating duplicate constants.
@@ -44,7 +46,7 @@ namespace {
 
 char ConstantMerge::ID = 0;
 INITIALIZE_PASS(ConstantMerge, "constmerge",
-                "Merge Duplicate Global Constants", false, false);
+                "Merge Duplicate Global Constants", false, false)
 
 ModulePass *llvm::createConstantMergePass() { return new ConstantMerge(); }
 
@@ -63,6 +65,18 @@ static void FindUsedValues(GlobalVariable *LLVMUsed,
       UsedValues.insert(GV);
 }
 
+// True if A is better than B.
+static bool IsBetterCannonical(const GlobalVariable &A,
+                               const GlobalVariable &B) {
+  if (!A.hasLocalLinkage() && B.hasLocalLinkage())
+    return true;
+
+  if (A.hasLocalLinkage() && !B.hasLocalLinkage())
+    return false;
+
+  return A.hasUnnamedAddr();
+}
+
 bool ConstantMerge::runOnModule(Module &M) {
   // Find all the globals that are marked "used".  These cannot be merged.
   SmallPtrSet<const GlobalValue*, 8> UsedGlobals;
@@ -83,44 +97,76 @@ bool ConstantMerge::runOnModule(Module &M) {
   // second level constants have initializers which point to the globals that
   // were just merged.
   while (1) {
-    // First pass: identify all globals that can be merged together, filling in
-    // the Replacements vector.  We cannot do the replacement in this pass
-    // because doing so may cause initializers of other globals to be rewritten,
-    // invalidating the Constant* pointers in CMap.
-    //
+
+    // First: Find the canonical constants others will be merged with.
     for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
          GVI != E; ) {
       GlobalVariable *GV = GVI++;
-      
+
       // If this GV is dead, remove it.
       GV->removeDeadConstantUsers();
       if (GV->use_empty() && GV->hasLocalLinkage()) {
         GV->eraseFromParent();
         continue;
       }
-      
-      // Only process constants with initializers in the default addres space.
-      if (!GV->isConstant() ||!GV->hasDefinitiveInitializer() ||
-          GV->getType()->getAddressSpace() != 0 || !GV->getSection().empty() ||
+
+      // Only process constants with initializers in the default address space.
+      if (!GV->isConstant() || !GV->hasDefinitiveInitializer() ||
+          GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
           // Don't touch values marked with attribute(used).
           UsedGlobals.count(GV))
         continue;
-      
-      
-      
+
       Constant *Init = GV->getInitializer();
 
       // Check to see if the initializer is already known.
       GlobalVariable *&Slot = CMap[Init];
 
-      if (Slot == 0) {    // Nope, add it to the map.
+      // 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
+      // it cannot be replace, but can be the canonical constant we merge with.
+      if (Slot == 0 || IsBetterCannonical(*GV, *Slot)) {
         Slot = GV;
-      } else if (GV->hasLocalLinkage()) {    // Yup, this is a duplicate!
-        // Make all uses of the duplicate constant use the canonical version.
-        Replacements.push_back(std::make_pair(GV, Slot));
       }
     }
 
+    // Second: identify all globals that can be merged together, filling in
+    // the Replacements vector.  We cannot do the replacement in this pass
+    // because doing so may cause initializers of other globals to be rewritten,
+    // invalidating the Constant* pointers in CMap.
+    for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
+         GVI != E; ) {
+      GlobalVariable *GV = GVI++;
+
+      // Only process constants with initializers in the default address space.
+      if (!GV->isConstant() || !GV->hasDefinitiveInitializer() ||
+          GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
+          // Don't touch values marked with attribute(used).
+          UsedGlobals.count(GV))
+        continue;
+
+      // We can only replace constant with local linkage.
+      if (!GV->hasLocalLinkage())
+        continue;
+
+      Constant *Init = GV->getInitializer();
+
+      // Check to see if the initializer is already known.
+      GlobalVariable *Slot = CMap[Init];
+
+      if (!Slot || Slot == GV)
+        continue;
+
+      if (!Slot->hasUnnamedAddr() && !GV->hasUnnamedAddr())
+        continue;
+
+      if (!GV->hasUnnamedAddr())
+        Slot->setUnnamedAddr(false);
+
+      // Make all uses of the duplicate constant use the canonical version.
+      Replacements.push_back(std::make_pair(GV, Slot));
+    }
+
     if (Replacements.empty())
       return MadeChange;
     CMap.clear();
@@ -133,6 +179,8 @@ bool ConstantMerge::runOnModule(Module &M) {
       Replacements[i].first->replaceAllUsesWith(Replacements[i].second);
 
       // Delete the global value from the module.
+      assert(Replacements[i].first->hasLocalLinkage() &&
+             "Refusing to delete an externally visible global variable.");
       Replacements[i].first->eraseFromParent();
     }