bool runOnBasicBlock(BasicBlock &BB);
bool handleFreeWithNonTrivialDependency(const CallInst *F,
+ Instruction *Inst,
MemDepResult Dep);
bool handleEndBlock(BasicBlock &BB);
bool RemoveUndeadPointers(Value *Ptr, uint64_t killPointerSize,
// Handle frees whose dependencies are non-trivial.
if (const CallInst *F = isFreeCall(Inst)) {
- MadeChange |= handleFreeWithNonTrivialDependency(F, InstDep);
+ MadeChange |= handleFreeWithNonTrivialDependency(F, Inst, InstDep);
continue;
}
/// handleFreeWithNonTrivialDependency - Handle frees of entire structures whose
/// dependency is a store to a field of that structure.
bool DSE::handleFreeWithNonTrivialDependency(const CallInst *F,
+ Instruction *Inst,
MemDepResult Dep) {
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
+ MemoryDependenceAnalysis &MD = getAnalysis<MemoryDependenceAnalysis>();
- Instruction *Dependency = Dep.getInst();
- if (!Dependency || !doesClobberMemory(Dependency) || !isElidable(Dependency))
- return false;
+ do {
+ Instruction *Dependency = Dep.getInst();
+ if (!Dependency || !doesClobberMemory(Dependency) || !isElidable(Dependency))
+ return false;
- Value *DepPointer = getPointerOperand(Dependency)->getUnderlyingObject();
+ Value *DepPointer = getPointerOperand(Dependency)->getUnderlyingObject();
- // Check for aliasing.
- if (AA.alias(F->getArgOperand(0), 1, DepPointer, 1) !=
- AliasAnalysis::MustAlias)
- return false;
+ // Check for aliasing.
+ if (AA.alias(F->getArgOperand(0), 1, DepPointer, 1) !=
+ AliasAnalysis::MustAlias)
+ return false;
- // DCE instructions only used to calculate that store
- DeleteDeadInstruction(Dependency);
- ++NumFastStores;
+ // DCE instructions only used to calculate that store
+ DeleteDeadInstruction(Dependency);
+ ++NumFastStores;
+
+ // Inst's old Dependency is now deleted. Compute the next dependency,
+ // which may also be dead, as in
+ // s[0] = 0;
+ // s[1] = 0; // This has just been deleted.
+ // free(s);
+ Dep = MD.getDependency(Inst);
+ } while (!Dep.isNonLocal());
return true;
}