+ bool AlreadyPredicated = BBI.Predicate.size() > 0;
+ // First analyze the end of BB branches.
+ BBI.TrueBB = BBI.FalseBB = NULL;
+ BBI.BrCond.clear();
+ BBI.IsBrAnalyzable =
+ !TII->AnalyzeBranch(*BBI.BB, BBI.TrueBB, BBI.FalseBB, BBI.BrCond);
+ BBI.HasFallThrough = BBI.IsBrAnalyzable && BBI.FalseBB == NULL;
+
+ if (BBI.BrCond.size()) {
+ // No false branch. This BB must end with a conditional branch and a
+ // fallthrough.
+ if (!BBI.FalseBB)
+ BBI.FalseBB = findFalseBlock(BBI.BB, BBI.TrueBB);
+ if (!BBI.FalseBB) {
+ // Malformed bcc? True and false blocks are the same?
+ BBI.IsUnpredicable = true;
+ return;
+ }
+ }
+
+ // Then scan all the instructions.
+ BBI.NonPredSize = 0;
+ BBI.ClobbersPred = false;
+ for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
+ I != E; ++I) {
+ const TargetInstrDesc &TID = I->getDesc();
+ if (TID.isNotDuplicable())
+ BBI.CannotBeCopied = true;
+
+ bool isPredicated = TII->isPredicated(I);
+ bool isCondBr = BBI.IsBrAnalyzable && TID.isConditionalBranch();
+
+ if (!isCondBr) {
+ if (!isPredicated)
+ BBI.NonPredSize++;
+ else if (!AlreadyPredicated) {
+ // FIXME: This instruction is already predicated before the
+ // if-conversion pass. It's probably something like a conditional move.
+ // Mark this block unpredicable for now.
+ BBI.IsUnpredicable = true;
+ return;
+ }
+ }
+
+ if (BBI.ClobbersPred && !isPredicated) {
+ // Predicate modification instruction should end the block (except for
+ // already predicated instructions and end of block branches).
+ if (isCondBr) {
+ // A conditional branch is not predicable, but it may be eliminated.
+ continue;
+ }
+
+ // Predicate may have been modified, the subsequent (currently)
+ // unpredicated instructions cannot be correctly predicated.
+ BBI.IsUnpredicable = true;
+ return;
+ }
+
+ // FIXME: Make use of PredDefs? e.g. ADDC, SUBC sets predicates but are
+ // still potentially predicable.
+ std::vector<MachineOperand> PredDefs;
+ if (TII->DefinesPredicate(I, PredDefs))
+ BBI.ClobbersPred = true;
+
+ if (!TII->isPredicable(I)) {
+ BBI.IsUnpredicable = true;
+ return;
+ }
+ }
+}
+
+/// FeasibilityAnalysis - Determine if the block is a suitable candidate to be
+/// predicated by the specified predicate.
+bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
+ SmallVectorImpl<MachineOperand> &Pred,
+ bool isTriangle, bool RevBranch) {
+ // If the block is dead or unpredicable, then it cannot be predicated.
+ if (BBI.IsDone || BBI.IsUnpredicable)
+ return false;
+
+ // If it is already predicated, check if its predicate subsumes the new
+ // predicate.
+ if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Pred))
+ return false;
+
+ if (BBI.BrCond.size()) {
+ if (!isTriangle)
+ return false;
+
+ // Test predicate subsumption.
+ SmallVector<MachineOperand, 4> RevPred(Pred.begin(), Pred.end());
+ SmallVector<MachineOperand, 4> Cond(BBI.BrCond.begin(), BBI.BrCond.end());
+ if (RevBranch) {
+ if (TII->ReverseBranchCondition(Cond))
+ return false;
+ }
+ if (TII->ReverseBranchCondition(RevPred) ||
+ !TII->SubsumesPredicate(Cond, RevPred))
+ return false;
+ }
+
+ return true;
+}
+
+/// AnalyzeBlock - Analyze the structure of the sub-CFG starting from
+/// the specified block. Record its successors and whether it looks like an
+/// if-conversion candidate.
+IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
+ std::vector<IfcvtToken*> &Tokens) {
+ BBInfo &BBI = BBAnalysis[BB->getNumber()];
+
+ if (BBI.IsAnalyzed || BBI.IsBeingAnalyzed)
+ return BBI;
+
+ BBI.BB = BB;
+ BBI.IsBeingAnalyzed = true;
+
+ ScanInstructions(BBI);
+
+ // Unanalyzable or ends with fallthrough or unconditional branch.
+ if (!BBI.IsBrAnalyzable || BBI.BrCond.empty()) {
+ BBI.IsBeingAnalyzed = false;
+ BBI.IsAnalyzed = true;
+ return BBI;
+ }
+
+ // Do not ifcvt if either path is a back edge to the entry block.
+ if (BBI.TrueBB == BB || BBI.FalseBB == BB) {
+ BBI.IsBeingAnalyzed = false;
+ BBI.IsAnalyzed = true;
+ return BBI;
+ }
+
+ // Do not ifcvt if true and false fallthrough blocks are the same.
+ if (!BBI.FalseBB) {
+ BBI.IsBeingAnalyzed = false;
+ BBI.IsAnalyzed = true;
+ return BBI;
+ }
+
+ BBInfo &TrueBBI = AnalyzeBlock(BBI.TrueBB, Tokens);
+ BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens);
+
+ if (TrueBBI.IsDone && FalseBBI.IsDone) {
+ BBI.IsBeingAnalyzed = false;
+ BBI.IsAnalyzed = true;
+ return BBI;
+ }
+
+ SmallVector<MachineOperand, 4> RevCond(BBI.BrCond.begin(), BBI.BrCond.end());
+ bool CanRevCond = !TII->ReverseBranchCondition(RevCond);
+
+ unsigned Dups = 0;
+ unsigned Dups2 = 0;
+ bool TNeedSub = TrueBBI.Predicate.size() > 0;
+ bool FNeedSub = FalseBBI.Predicate.size() > 0;
+ bool Enqueued = false;
+ if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI, Dups, Dups2) &&
+ MeetIfcvtSizeLimit(TrueBBI.NonPredSize - (Dups + Dups2)) &&
+ MeetIfcvtSizeLimit(FalseBBI.NonPredSize - (Dups + Dups2)) &&
+ FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
+ FeasibilityAnalysis(FalseBBI, RevCond)) {
+ // Diamond:
+ // EBB
+ // / \_
+ // | |
+ // TBB FBB
+ // \ /
+ // TailBB
+ // Note TailBB can be empty.
+ Tokens.push_back(new IfcvtToken(BBI, ICDiamond, TNeedSub|FNeedSub, Dups,
+ Dups2));
+ Enqueued = true;
+ }
+
+ if (ValidTriangle(TrueBBI, FalseBBI, false, Dups) &&
+ MeetIfcvtSizeLimit(TrueBBI.NonPredSize) &&
+ FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) {