-
- // 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));
- }
- }
+
+ // 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;
+
+ // 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 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))
+ Slot = GV;
+ }
+
+ // 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.
+ PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
+ GlobalVariable *Slot = CMap[Pair];
+
+ 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));