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Fix memory corruption bug PR193

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llvm-svn: 10586
This commit is contained in:
Chris Lattner 2003-12-22 23:49:36 +00:00
parent 8740fbd052
commit 30fa61ca6c
1 changed files with 26 additions and 20 deletions
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42
lib/Transforms/IPO/ConstantMerge.cpp
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@ -40,8 +40,15 @@ Pass *llvm::createConstantMergePass() { return new ConstantMerge(); }
bool ConstantMerge::run(Module &M) {
std::map<Constant*, GlobalVariable*> CMap;
bool MadeChanges = false;
// Replacements - This vector contains a list of replacements to perform.
std::vector<std::pair<GlobalVariable*, GlobalVariable*> > Replacements;
// 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::giterator GV = M.gbegin(), E = M.gend(); GV != E; ++GV)
// Only process constants with initializers
if (GV->isConstant() && GV->hasInitializer()) {
@ -54,28 +61,27 @@ bool ConstantMerge::run(Module &M) {
CMap.insert(I, std::make_pair(Init, GV));
} else if (GV->hasInternalLinkage()) { // Yup, this is a duplicate!
// Make all uses of the duplicate constant use the canonical 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.push_back(std::make_pair(GV, I->second));
} else if (I->second->hasInternalLinkage()) {
// Make all uses of the duplicate constant use the canonical version...
I->second->replaceAllUsesWith(GV);
// Delete the global value from the module... and back up iterator to
// not skip the next global...
M.getGlobalList().erase(I->second);
Replacements.push_back(std::make_pair(I->second, GV));
I->second = GV;
++NumMerged;
MadeChanges = true;
}
}
return MadeChanges;
if (Replacements.empty()) return false;
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();
return true;
}