+ // If this is after register allocation, there are no phis to fix.
+ if (!PreRegAlloc)
+ return Changed;
+
+ // If we made no changes so far, we are safe.
+ if (!Changed)
+ return Changed;
+
+
+ // Handle the nasty case in that we duplicated a block that is part of a loop
+ // into some but not all of its predecessors. For example:
+ // 1 -> 2 <-> 3 |
+ // \ |
+ // \---> rest |
+ // if we duplicate 2 into 1 but not into 3, we end up with
+ // 12 -> 3 <-> 2 -> rest |
+ // \ / |
+ // \----->-----/ |
+ // If there was a "var = phi(1, 3)" in 2, it has to be ultimately replaced
+ // with a phi in 3 (which now dominates 2).
+ // What we do here is introduce a copy in 3 of the register defined by the
+ // phi, just like when we are duplicating 2 into 3, but we don't copy any
+ // real instructions or remove the 3 -> 2 edge from the phi in 2.
+ for (SmallSetVector<MachineBasicBlock *, 8>::iterator PI = Preds.begin(),
+ PE = Preds.end(); PI != PE; ++PI) {
+ MachineBasicBlock *PredBB = *PI;
+ if (std::find(TDBBs.begin(), TDBBs.end(), PredBB) != TDBBs.end())
+ continue;
+
+ // EH edges
+ if (PredBB->succ_size() != 1)
+ continue;
+
+ DenseMap<unsigned, unsigned> LocalVRMap;
+ SmallVector<std::pair<unsigned,unsigned>, 4> CopyInfos;
+ MachineBasicBlock::iterator I = TailBB->begin();
+ // Process PHI instructions first.
+ while (I != TailBB->end() && I->isPHI()) {
+ // Replace the uses of the def of the PHI with the register coming
+ // from PredBB.
+ MachineInstr *MI = &*I++;
+ ProcessPHI(MI, TailBB, PredBB, LocalVRMap, CopyInfos, UsedByPhi, false);
+ }
+ MachineBasicBlock::iterator Loc = PredBB->getFirstTerminator();
+ for (unsigned i = 0, e = CopyInfos.size(); i != e; ++i) {
+ Copies.push_back(BuildMI(*PredBB, Loc, DebugLoc(),
+ TII->get(TargetOpcode::COPY),
+ CopyInfos[i].first).addReg(CopyInfos[i].second));
+ }
+ }
+