[If Converter] Convert recursion to iteration.
This commit makes changes to IfConverter::AnalyzeBlock to use iteration instead of recursion. Previously, this function would get called recursively a large number of times and eventually segfault when a function with the following CFG was compiled: BB0: if (condition0) goto BB1 goto BB2 BB1: goto BB2 BB2: if (condition1) goto BB3 goto BB4 BB3: ... (repeat until BB7488) rdar://problem/21386145 Differential Revision: http://reviews.llvm.org/D10587 llvm-svn: 240589
This commit is contained in:
Akira Hatanaka
parent
75403d7753
commit
14348aa2c5
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@ -197,8 +197,7 @@ namespace {
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bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI,
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unsigned &Dups1, unsigned &Dups2) const;
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void ScanInstructions(BBInfo &BBI);
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BBInfo &AnalyzeBlock(MachineBasicBlock *BB,
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std::vector<IfcvtToken*> &Tokens);
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void AnalyzeBlock(MachineBasicBlock *MBB, std::vector<IfcvtToken*> &Tokens);
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bool FeasibilityAnalysis(BBInfo &BBI, SmallVectorImpl<MachineOperand> &Cond,
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bool isTriangle = false, bool RevBranch = false);
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void AnalyzeBlocks(MachineFunction &MF, std::vector<IfcvtToken*> &Tokens);
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@ -764,155 +763,185 @@ bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
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/// AnalyzeBlock - Analyze the structure of the sub-CFG starting from
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/// the specified block. Record its successors and whether it looks like an
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/// if-conversion candidate.
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IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
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std::vector<IfcvtToken*> &Tokens) {
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BBInfo &BBI = BBAnalysis[BB->getNumber()];
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void IfConverter::AnalyzeBlock(MachineBasicBlock *MBB,
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std::vector<IfcvtToken*> &Tokens) {
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struct BBState {
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BBState(MachineBasicBlock *BB) : MBB(BB), SuccsAnalyzed(false) {}
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MachineBasicBlock *MBB;
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if (BBI.IsAnalyzed || BBI.IsBeingAnalyzed)
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return BBI;
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/// This flag is true if MBB's successors have been analyzed.
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bool SuccsAnalyzed;
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};
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BBI.BB = BB;
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BBI.IsBeingAnalyzed = true;
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// Push MBB to the stack.
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SmallVector<BBState, 16> BBStack(1, MBB);
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ScanInstructions(BBI);
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while (!BBStack.empty()) {
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BBState &State = BBStack.back();
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MachineBasicBlock *BB = State.MBB;
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BBInfo &BBI = BBAnalysis[BB->getNumber()];
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// Unanalyzable or ends with fallthrough or unconditional branch, or if is not
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// considered for ifcvt anymore.
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if (!BBI.IsBrAnalyzable || BBI.BrCond.empty() || BBI.IsDone) {
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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return BBI;
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}
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if (!State.SuccsAnalyzed) {
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if (BBI.IsAnalyzed || BBI.IsBeingAnalyzed) {
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BBStack.pop_back();
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continue;
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}
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// Do not ifcvt if either path is a back edge to the entry block.
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if (BBI.TrueBB == BB || BBI.FalseBB == BB) {
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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return BBI;
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}
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BBI.BB = BB;
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BBI.IsBeingAnalyzed = true;
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// Do not ifcvt if true and false fallthrough blocks are the same.
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if (!BBI.FalseBB) {
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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return BBI;
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}
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ScanInstructions(BBI);
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BBInfo &TrueBBI = AnalyzeBlock(BBI.TrueBB, Tokens);
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BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens);
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// Unanalyzable or ends with fallthrough or unconditional branch, or if is
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// not considered for ifcvt anymore.
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if (!BBI.IsBrAnalyzable || BBI.BrCond.empty() || BBI.IsDone) {
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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BBStack.pop_back();
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continue;
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}
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if (TrueBBI.IsDone && FalseBBI.IsDone) {
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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return BBI;
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}
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// Do not ifcvt if either path is a back edge to the entry block.
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if (BBI.TrueBB == BB || BBI.FalseBB == BB) {
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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BBStack.pop_back();
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continue;
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}
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SmallVector<MachineOperand, 4> RevCond(BBI.BrCond.begin(), BBI.BrCond.end());
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bool CanRevCond = !TII->ReverseBranchCondition(RevCond);
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// Do not ifcvt if true and false fallthrough blocks are the same.
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if (!BBI.FalseBB) {
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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BBStack.pop_back();
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continue;
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}
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unsigned Dups = 0;
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unsigned Dups2 = 0;
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bool TNeedSub = !TrueBBI.Predicate.empty();
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bool FNeedSub = !FalseBBI.Predicate.empty();
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bool Enqueued = false;
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// Push the False and True blocks to the stack.
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State.SuccsAnalyzed = true;
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BBStack.push_back(BBI.FalseBB);
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BBStack.push_back(BBI.TrueBB);
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continue;
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}
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BranchProbability Prediction = MBPI->getEdgeProbability(BB, TrueBBI.BB);
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BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
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BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
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if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
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MeetIfcvtSizeLimit(*TrueBBI.BB, (TrueBBI.NonPredSize - (Dups + Dups2) +
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TrueBBI.ExtraCost), TrueBBI.ExtraCost2,
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*FalseBBI.BB, (FalseBBI.NonPredSize - (Dups + Dups2) +
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if (TrueBBI.IsDone && FalseBBI.IsDone) {
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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BBStack.pop_back();
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continue;
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}
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SmallVector<MachineOperand, 4>
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RevCond(BBI.BrCond.begin(), BBI.BrCond.end());
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bool CanRevCond = !TII->ReverseBranchCondition(RevCond);
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unsigned Dups = 0;
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unsigned Dups2 = 0;
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bool TNeedSub = !TrueBBI.Predicate.empty();
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bool FNeedSub = !FalseBBI.Predicate.empty();
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bool Enqueued = false;
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BranchProbability Prediction = MBPI->getEdgeProbability(BB, TrueBBI.BB);
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if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
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MeetIfcvtSizeLimit(*TrueBBI.BB, (TrueBBI.NonPredSize - (Dups + Dups2) +
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TrueBBI.ExtraCost), TrueBBI.ExtraCost2,
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*FalseBBI.BB, (FalseBBI.NonPredSize - (Dups + Dups2) +
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FalseBBI.ExtraCost),FalseBBI.ExtraCost2,
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Prediction) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
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FeasibilityAnalysis(FalseBBI, RevCond)) {
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// Diamond:
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// EBB
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// / \_
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// | |
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// TBB FBB
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// \ /
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// TailBB
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// Note TailBB can be empty.
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Tokens.push_back(new IfcvtToken(BBI, ICDiamond, TNeedSub|FNeedSub, Dups,
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Dups2));
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Enqueued = true;
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}
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if (ValidTriangle(TrueBBI, FalseBBI, false, Dups, Prediction) &&
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MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
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TrueBBI.ExtraCost2, Prediction) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) {
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// Triangle:
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// EBB
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// | \_
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// | |
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// | TBB
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// | /
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// FBB
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Tokens.push_back(new IfcvtToken(BBI, ICTriangle, TNeedSub, Dups));
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Enqueued = true;
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}
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if (ValidTriangle(TrueBBI, FalseBBI, true, Dups, Prediction) &&
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MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
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TrueBBI.ExtraCost2, Prediction) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond, true, true)) {
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Tokens.push_back(new IfcvtToken(BBI, ICTriangleRev, TNeedSub, Dups));
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Enqueued = true;
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}
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if (ValidSimple(TrueBBI, Dups, Prediction) &&
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MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
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TrueBBI.ExtraCost2, Prediction) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
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// Simple (split, no rejoin):
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// EBB
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// | \_
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// | |
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// | TBB---> exit
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// |
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// FBB
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Tokens.push_back(new IfcvtToken(BBI, ICSimple, TNeedSub, Dups));
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Enqueued = true;
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}
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if (CanRevCond) {
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// Try the other path...
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if (ValidTriangle(FalseBBI, TrueBBI, false, Dups,
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Prediction.getCompl()) &&
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MeetIfcvtSizeLimit(*FalseBBI.BB,
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FalseBBI.NonPredSize + FalseBBI.ExtraCost,
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FalseBBI.ExtraCost2, Prediction.getCompl()) &&
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FeasibilityAnalysis(FalseBBI, RevCond, true)) {
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Tokens.push_back(new IfcvtToken(BBI, ICTriangleFalse, FNeedSub, Dups));
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FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
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FeasibilityAnalysis(FalseBBI, RevCond)) {
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// Diamond:
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// EBB
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// / \_
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// | |
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// TBB FBB
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// \ /
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// TailBB
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// Note TailBB can be empty.
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Tokens.push_back(new IfcvtToken(BBI, ICDiamond, TNeedSub|FNeedSub, Dups,
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Dups2));
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Enqueued = true;
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}
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if (ValidTriangle(FalseBBI, TrueBBI, true, Dups,
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Prediction.getCompl()) &&
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MeetIfcvtSizeLimit(*FalseBBI.BB,
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FalseBBI.NonPredSize + FalseBBI.ExtraCost,
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if (ValidTriangle(TrueBBI, FalseBBI, false, Dups, Prediction) &&
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MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
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TrueBBI.ExtraCost2, Prediction) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) {
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// Triangle:
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// EBB
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// | \_
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// | |
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// | TBB
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// | /
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// FBB
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Tokens.push_back(new IfcvtToken(BBI, ICTriangle, TNeedSub, Dups));
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Enqueued = true;
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}
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if (ValidTriangle(TrueBBI, FalseBBI, true, Dups, Prediction) &&
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MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
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TrueBBI.ExtraCost2, Prediction) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond, true, true)) {
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Tokens.push_back(new IfcvtToken(BBI, ICTriangleRev, TNeedSub, Dups));
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Enqueued = true;
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}
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if (ValidSimple(TrueBBI, Dups, Prediction) &&
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MeetIfcvtSizeLimit(*TrueBBI.BB, TrueBBI.NonPredSize + TrueBBI.ExtraCost,
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TrueBBI.ExtraCost2, Prediction) &&
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FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
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// Simple (split, no rejoin):
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// EBB
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// | \_
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// | |
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// | TBB---> exit
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// |
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// FBB
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Tokens.push_back(new IfcvtToken(BBI, ICSimple, TNeedSub, Dups));
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Enqueued = true;
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}
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if (CanRevCond) {
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// Try the other path...
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if (ValidTriangle(FalseBBI, TrueBBI, false, Dups,
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Prediction.getCompl()) &&
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MeetIfcvtSizeLimit(*FalseBBI.BB,
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FalseBBI.NonPredSize + FalseBBI.ExtraCost,
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FalseBBI.ExtraCost2, Prediction.getCompl()) &&
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FeasibilityAnalysis(FalseBBI, RevCond, true)) {
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Tokens.push_back(new IfcvtToken(BBI, ICTriangleFalse, FNeedSub, Dups));
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Enqueued = true;
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}
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if (ValidTriangle(FalseBBI, TrueBBI, true, Dups,
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Prediction.getCompl()) &&
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MeetIfcvtSizeLimit(*FalseBBI.BB,
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FalseBBI.NonPredSize + FalseBBI.ExtraCost,
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FalseBBI.ExtraCost2, Prediction.getCompl()) &&
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FeasibilityAnalysis(FalseBBI, RevCond, true, true)) {
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Tokens.push_back(new IfcvtToken(BBI, ICTriangleFRev, FNeedSub, Dups));
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Enqueued = true;
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Tokens.push_back(new IfcvtToken(BBI, ICTriangleFRev, FNeedSub, Dups));
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Enqueued = true;
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}
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if (ValidSimple(FalseBBI, Dups, Prediction.getCompl()) &&
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MeetIfcvtSizeLimit(*FalseBBI.BB,
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FalseBBI.NonPredSize + FalseBBI.ExtraCost,
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FalseBBI.ExtraCost2, Prediction.getCompl()) &&
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FeasibilityAnalysis(FalseBBI, RevCond)) {
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Tokens.push_back(new IfcvtToken(BBI, ICSimpleFalse, FNeedSub, Dups));
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Enqueued = true;
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}
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}
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if (ValidSimple(FalseBBI, Dups, Prediction.getCompl()) &&
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MeetIfcvtSizeLimit(*FalseBBI.BB,
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FalseBBI.NonPredSize + FalseBBI.ExtraCost,
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FalseBBI.ExtraCost2, Prediction.getCompl()) &&
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FeasibilityAnalysis(FalseBBI, RevCond)) {
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Tokens.push_back(new IfcvtToken(BBI, ICSimpleFalse, FNeedSub, Dups));
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Enqueued = true;
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}
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BBI.IsEnqueued = Enqueued;
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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BBStack.pop_back();
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}
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BBI.IsEnqueued = Enqueued;
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BBI.IsBeingAnalyzed = false;
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BBI.IsAnalyzed = true;
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return BBI;
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}
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/// AnalyzeBlocks - Analyze all blocks and find entries for all if-conversion
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