-// ConstantMerge::run - Workhorse for the pass. This eliminates duplicate
-// constants, starting at global ConstantNo, and adds vars to the map if they
-// are new and unique.
-//
-bool ConstantMerge::run(Module &M) {
- std::map<Constant*, GlobalVariable*> CMap;
- bool MadeChanges = false;
-
- for (Module::giterator GV = M.gbegin(), E = M.gend(); GV != E; ++GV)
- if (GV->isConstant()) { // Only process constants
- assert(GV->hasInitializer() && "Globals constants must have inits!");
- Constant *Init = GV->getInitializer();
-
- // Check to see if the initializer is already known...
- std::map<Constant*, GlobalVariable*>::iterator I = CMap.find(Init);
-
- if (I == CMap.end()) { // Nope, add it to the map
- CMap.insert(I, std::make_pair(Init, GV));
- } else { // Yup, this is a duplicate!
- // Make all uses of the duplicate constant use the cannonical version...
- GV->replaceAllUsesWith(I->second);
-
- // Delete the global value from the module... and back up iterator to
- // not skip the next global...
- GV = --M.getGlobalList().erase(GV);
-
- ++NumMerged;
- MadeChanges = true;
+ // Replacements - This vector contains a list of replacements to perform.
+ std::vector<std::pair<GlobalVariable*, GlobalVariable*> > Replacements;
+
+ bool MadeChange = false;
+
+ // Iterate constant merging while we are still making progress. Merging two
+ // constants together may allow us to merge other constants together if the
+ // 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.
+ //
+ 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->hasInternalLinkage()) {
+ GV->eraseFromParent();
+ continue;
+ }
+
+ // Only process constants with initializers.
+ if (GV->isConstant() && GV->hasInitializer()) {
+ Constant *Init = GV->getInitializer();
+
+ // Check to see if the initializer is already known.
+ GlobalVariable *&Slot = CMap[std::make_pair(Init, GV->getSection())];
+
+ if (Slot == 0) { // Nope, add it to the map.
+ Slot = GV;
+ } else if (GV->hasInternalLinkage()) { // Yup, this is a duplicate!
+ // Make all uses of the duplicate constant use the canonical version.
+ Replacements.push_back(std::make_pair(GV, Slot));
+ } else if (GV->hasInternalLinkage()) {
+ // Make all uses of the duplicate constant use the canonical version.
+ Replacements.push_back(std::make_pair(Slot, GV));
+ Slot = GV;
+ }