//===- ConstantMerge.cpp - Merge duplicate global constants ---------------===//
-//
+//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
//===----------------------------------------------------------------------===//
//
// This file defines the interface to a pass that merges duplicate global
//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "constmerge"
#include "llvm/Transforms/IPO.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Compiler.h"
using namespace llvm;
+STATISTIC(NumMerged, "Number of global constants merged");
+
namespace {
- Statistic<> NumMerged("constmerge", "Number of global constants merged");
+ struct VISIBILITY_HIDDEN ConstantMerge : public ModulePass {
+ static char ID; // Pass identification, replacement for typeid
+ ConstantMerge() : ModulePass((intptr_t)&ID) {}
- struct ConstantMerge : public ModulePass {
// run - For this pass, process all of the globals in the module,
// eliminating duplicate constants.
//
bool runOnModule(Module &M);
};
- RegisterOpt<ConstantMerge> X("constmerge","Merge Duplicate Global Constants");
+ char ConstantMerge::ID = 0;
+ RegisterPass<ConstantMerge>X("constmerge","Merge Duplicate Global Constants");
}
ModulePass *llvm::createConstantMergePass() { return new ConstantMerge(); }
bool ConstantMerge::runOnModule(Module &M) {
- std::map<Constant*, GlobalVariable*> CMap;
+ // Map unique constant/section pairs to globals. We don't want to merge
+ // globals in different sections.
+ std::map<std::pair<Constant*, std::string>, GlobalVariable*> CMap;
// Replacements - This vector contains a list of replacements to perform.
std::vector<std::pair<GlobalVariable*, GlobalVariable*> > Replacements;
// because doing so may cause initializers of other globals to be rewritten,
// invalidating the Constant* pointers in CMap.
//
- for (Module::global_iterator GV = M.global_begin(), E = M.global_end(); GV != E; ++GV)
- // Only process constants with initializers
+ 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...
- 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));
+
+ // 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, I->second));
- } else if (I->second->hasInternalLinkage()) {
- // Make all uses of the duplicate constant use the canonical version.
- Replacements.push_back(std::make_pair(I->second, GV));
- I->second = GV;
+ Replacements.push_back(std::make_pair(GV, Slot));
}
}
-
+ }
+
if (Replacements.empty())
return MadeChange;
CMap.clear();
-
+
// Now that we have figured out which replacements must be made, do them all
// now. This avoid invalidating the pointers in CMap, which are unneeded
// now.
for (unsigned i = 0, e = Replacements.size(); i != e; ++i) {
// Eliminate any uses of the dead global...
Replacements[i].first->replaceAllUsesWith(Replacements[i].second);
-
+
// Delete the global value from the module...
M.getGlobalList().erase(Replacements[i].first);
}
-
+
NumMerged += Replacements.size();
Replacements.clear();
}