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Reduce indentation by early detection of 'continue'. No functionality change.
llvm-svn: 157348
This commit is contained in:
Bill Wendling
parent
bf7155d836
commit
9235b4e8b1
@ -819,10 +819,8 @@ bool BranchFolder::TryTailMergeBlocks(MachineBasicBlock *SuccBB,
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}
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bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
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if (!EnableTailMerge) return false;
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bool MadeChange = false;
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if (!EnableTailMerge) return MadeChange;
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// First find blocks with no successors.
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MergePotentials.clear();
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@ -839,6 +837,7 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
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if (MergePotentials.size() == TailMergeThreshold)
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for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
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TriedMerging.insert(MergePotentials[i].getBlock());
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// See if we can do any tail merging on those.
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if (MergePotentials.size() >= 2)
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MadeChange |= TryTailMergeBlocks(NULL, NULL);
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@ -864,88 +863,97 @@ bool BranchFolder::TailMergeBlocks(MachineFunction &MF) {
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for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
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I != E; ++I) {
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if (I->pred_size() >= 2) {
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SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
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MachineBasicBlock *IBB = I;
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MachineBasicBlock *PredBB = prior(I);
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MergePotentials.clear();
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for (MachineBasicBlock::pred_iterator P = I->pred_begin(),
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E2 = I->pred_end();
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P != E2 && MergePotentials.size() < TailMergeThreshold; ++P) {
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MachineBasicBlock *PBB = *P;
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if (TriedMerging.count(PBB))
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continue;
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// Skip blocks that loop to themselves, can't tail merge these.
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if (PBB == IBB)
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continue;
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// Visit each predecessor only once.
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if (!UniquePreds.insert(PBB))
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continue;
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// Skip blocks which may jump to a landing pad. Can't tail merge these.
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if (PBB->getLandingPadSuccessor())
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continue;
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MachineBasicBlock *TBB = 0, *FBB = 0;
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SmallVector<MachineOperand, 4> Cond;
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if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) {
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// Failing case: IBB is the target of a cbr, and
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// we cannot reverse the branch.
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SmallVector<MachineOperand, 4> NewCond(Cond);
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if (!Cond.empty() && TBB == IBB) {
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if (TII->ReverseBranchCondition(NewCond))
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continue;
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// This is the QBB case described above
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if (!FBB)
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FBB = llvm::next(MachineFunction::iterator(PBB));
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}
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// Failing case: the only way IBB can be reached from PBB is via
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// exception handling. Happens for landing pads. Would be nice
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// to have a bit in the edge so we didn't have to do all this.
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if (IBB->isLandingPad()) {
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MachineFunction::iterator IP = PBB; IP++;
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MachineBasicBlock *PredNextBB = NULL;
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if (IP != MF.end())
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PredNextBB = IP;
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if (TBB == NULL) {
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if (IBB != PredNextBB) // fallthrough
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continue;
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} else if (FBB) {
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if (TBB != IBB && FBB != IBB) // cbr then ubr
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continue;
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} else if (Cond.empty()) {
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if (TBB != IBB) // ubr
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continue;
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} else {
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if (TBB != IBB && IBB != PredNextBB) // cbr
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continue;
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}
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}
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// Remove the unconditional branch at the end, if any.
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if (TBB && (Cond.empty() || FBB)) {
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DebugLoc dl; // FIXME: this is nowhere
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TII->RemoveBranch(*PBB);
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if (!Cond.empty())
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// reinsert conditional branch only, for now
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TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond, dl);
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}
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MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), *P));
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if (I->pred_size() >= 2) continue;
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SmallPtrSet<MachineBasicBlock *, 8> UniquePreds;
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MachineBasicBlock *IBB = I;
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MachineBasicBlock *PredBB = prior(I);
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MergePotentials.clear();
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for (MachineBasicBlock::pred_iterator P = I->pred_begin(),
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E2 = I->pred_end();
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P != E2 && MergePotentials.size() < TailMergeThreshold; ++P) {
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MachineBasicBlock *PBB = *P;
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if (TriedMerging.count(PBB))
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continue;
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// Skip blocks that loop to themselves, can't tail merge these.
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if (PBB == IBB)
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continue;
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// Visit each predecessor only once.
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if (!UniquePreds.insert(PBB))
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continue;
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// Skip blocks which may jump to a landing pad. Can't tail merge these.
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if (PBB->getLandingPadSuccessor())
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continue;
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MachineBasicBlock *TBB = 0, *FBB = 0;
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SmallVector<MachineOperand, 4> Cond;
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if (!TII->AnalyzeBranch(*PBB, TBB, FBB, Cond, true)) {
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// Failing case: IBB is the target of a cbr, and we cannot reverse the
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// branch.
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SmallVector<MachineOperand, 4> NewCond(Cond);
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if (!Cond.empty() && TBB == IBB) {
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if (TII->ReverseBranchCondition(NewCond))
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continue;
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// This is the QBB case described above
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if (!FBB)
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FBB = llvm::next(MachineFunction::iterator(PBB));
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}
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// Failing case: the only way IBB can be reached from PBB is via
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// exception handling. Happens for landing pads. Would be nice to have
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// a bit in the edge so we didn't have to do all this.
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if (IBB->isLandingPad()) {
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MachineFunction::iterator IP = PBB; IP++;
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MachineBasicBlock *PredNextBB = NULL;
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if (IP != MF.end())
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PredNextBB = IP;
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if (TBB == NULL) {
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if (IBB != PredNextBB) // fallthrough
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continue;
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} else if (FBB) {
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if (TBB != IBB && FBB != IBB) // cbr then ubr
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continue;
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} else if (Cond.empty()) {
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if (TBB != IBB) // ubr
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continue;
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} else {
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if (TBB != IBB && IBB != PredNextBB) // cbr
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continue;
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}
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}
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// Remove the unconditional branch at the end, if any.
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if (TBB && (Cond.empty() || FBB)) {
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DebugLoc dl; // FIXME: this is nowhere
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TII->RemoveBranch(*PBB);
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if (!Cond.empty())
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// reinsert conditional branch only, for now
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TII->InsertBranch(*PBB, (TBB == IBB) ? FBB : TBB, 0, NewCond, dl);
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}
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MergePotentials.push_back(MergePotentialsElt(HashEndOfMBB(PBB), *P));
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}
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// If this is a large problem, avoid visiting the same basic blocks
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// multiple times.
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if (MergePotentials.size() == TailMergeThreshold)
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for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
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TriedMerging.insert(MergePotentials[i].getBlock());
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if (MergePotentials.size() >= 2)
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MadeChange |= TryTailMergeBlocks(IBB, PredBB);
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// Reinsert an unconditional branch if needed.
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// The 1 below can occur as a result of removing blocks in
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// TryTailMergeBlocks.
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PredBB = prior(I); // this may have been changed in TryTailMergeBlocks
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if (MergePotentials.size() == 1 &&
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MergePotentials.begin()->getBlock() != PredBB)
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FixTail(MergePotentials.begin()->getBlock(), IBB, TII);
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}
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// If this is a large problem, avoid visiting the same basic blocks multiple
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// times.
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if (MergePotentials.size() == TailMergeThreshold)
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for (unsigned i = 0, e = MergePotentials.size(); i != e; ++i)
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TriedMerging.insert(MergePotentials[i].getBlock());
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if (MergePotentials.size() >= 2)
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MadeChange |= TryTailMergeBlocks(IBB, PredBB);
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// Reinsert an unconditional branch if needed. The 1 below can occur as a
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// result of removing blocks in TryTailMergeBlocks.
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PredBB = prior(I); // this may have been changed in TryTailMergeBlocks
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if (MergePotentials.size() == 1 &&
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MergePotentials.begin()->getBlock() != PredBB)
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FixTail(MergePotentials.begin()->getBlock(), IBB, TII);
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}
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return MadeChange;
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}
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