-
-MachineBasicBlock *PHIElimination::SplitCriticalEdge(MachineBasicBlock *A,
- MachineBasicBlock *B) {
- assert(A && B && "Missing MBB end point");
-
- MachineFunction *MF = A->getParent();
-
- // We may need to update A's terminator, but we can't do that if AnalyzeBranch
- // fails. If A uses a jump table, we won't touch it.
- const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
- MachineBasicBlock *TBB = 0, *FBB = 0;
- SmallVector<MachineOperand, 4> Cond;
- if (TII->AnalyzeBranch(*A, TBB, FBB, Cond))
- return NULL;
-
- ++NumSplits;
-
- MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
- MF->insert(llvm::next(MachineFunction::iterator(A)), NMBB);
- DEBUG(dbgs() << "PHIElimination splitting critical edge:"
- " BB#" << A->getNumber()
- << " -- BB#" << NMBB->getNumber()
- << " -- BB#" << B->getNumber() << '\n');
-
- A->ReplaceUsesOfBlockWith(B, NMBB);
- A->updateTerminator();
-
- // Insert unconditional "jump B" instruction in NMBB if necessary.
- NMBB->addSuccessor(B);
- if (!NMBB->isLayoutSuccessor(B)) {
- Cond.clear();
- MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, B, NULL, Cond);
- }
-
- // Fix PHI nodes in B so they refer to NMBB instead of A
- for (MachineBasicBlock::iterator i = B->begin(), e = B->end();
- i != e && i->isPHI(); ++i)
- for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
- if (i->getOperand(ni+1).getMBB() == A)
- i->getOperand(ni+1).setMBB(NMBB);
-
- if (LiveVariables *LV=getAnalysisIfAvailable<LiveVariables>())
- LV->addNewBlock(NMBB, A, B);
-
- if (MachineDominatorTree *MDT=getAnalysisIfAvailable<MachineDominatorTree>())
- MDT->addNewBlock(NMBB, A);
-
- return NMBB;
-}