// This file defines the interface to a pass that merges duplicate global
// constants together into a single constant that is shared. This is useful
// because some passes (ie TraceValues) insert a lot of string constants into
-// the program, regardless of whether or not they duplicate an existing string.
+// the program, regardless of whether or not an existing string is available.
//
// Algorithm: ConstantMerge is designed to build up a map of available constants
-// and elminate duplicates when it is initialized.
-//
-// The DynamicConstantMerge method is a superset of the ConstantMerge algorithm
-// that checks for each method to see if constants have been added to the
-// constant pool since it was last run... if so, it processes them.
+// and eliminate duplicates when it is initialized.
//
//===----------------------------------------------------------------------===//
-#include "llvm/Transforms/ConstantMerge.h"
-#include "llvm/GlobalVariable.h"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "Support/Statistic.h"
-// mergeDuplicateConstants - Workhorse for the pass. This eliminates duplicate
-// constants, starting at global ConstantNo, and adds vars to the map if they
-// are new and unique.
-//
-static inline
-bool mergeDuplicateConstants(Module *M, unsigned &ConstantNo,
- std::map<Constant*, GlobalVariable*> &CMap) {
- Module::GlobalListType &GList = M->getGlobalList();
- if (GList.size() <= ConstantNo) return false; // No new constants
+namespace {
+ Statistic<> NumMerged("constmerge", "Number of global constants merged");
+
+ struct ConstantMerge : public Pass {
+ // run - For this pass, process all of the globals in the module,
+ // eliminating duplicate constants.
+ //
+ bool run(Module &M);
+ };
+
+ RegisterOpt<ConstantMerge> X("constmerge","Merge Duplicate Global Constants");
+}
+
+Pass *createConstantMergePass() { return new ConstantMerge(); }
+
+
+bool ConstantMerge::run(Module &M) {
+ std::map<Constant*, GlobalVariable*> CMap;
bool MadeChanges = false;
- for (; ConstantNo < GList.size(); ++ConstantNo) {
- GlobalVariable *GV = GList[ConstantNo];
+ 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();
std::map<Constant*, GlobalVariable*>::iterator I = CMap.find(Init);
if (I == CMap.end()) { // Nope, add it to the map
- CMap.insert(std::make_pair(Init, GV));
+ 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);
- // Remove and delete the global value from the module...
- delete GList.remove(GList.begin()+ConstantNo);
+ // Delete the global value from the module... and back up iterator to
+ // not skip the next global...
+ GV = --M.getGlobalList().erase(GV);
- --ConstantNo; // Don't skip the next constant.
+ ++NumMerged;
MadeChanges = true;
}
}
- }
- return MadeChanges;
-}
-
-// mergeDuplicateConstants - Static accessor for clients that don't want to
-// deal with passes.
-//
-bool ConstantMerge::mergeDuplicateConstants(Module *M) {
- std::map<Constant*, GlobalVariable*> Constants;
- unsigned LastConstantSeen = 0;
- return ::mergeDuplicateConstants(M, LastConstantSeen, Constants);
-}
-
-
-// doInitialization - For this pass, process all of the globals in the
-// module, eliminating duplicate constants.
-//
-bool ConstantMerge::doInitialization(Module *M) {
- return ::mergeDuplicateConstants(M, LastConstantSeen, Constants);
-}
-
-// doPerMethodWork - Check to see if any globals have been added to the
-// global list for the module. If so, eliminate them.
-//
-bool DynamicConstantMerge::runOnMethod(Method *M) {
- return ::mergeDuplicateConstants(M->getParent(), LastConstantSeen, Constants);
+ return MadeChanges;
}