예제 #1
0
/// The liverange splitting logic sometimes produces bundles of copies when
/// subregisters are involved. Expand these into a sequence of copy instructions
/// after processing the last in the bundle. Does not update LiveIntervals
/// which we shouldn't need for this instruction anymore.
void VirtRegRewriter::expandCopyBundle(MachineInstr &MI) const {
  if (!MI.isCopy())
    return;

  if (MI.isBundledWithPred() && !MI.isBundledWithSucc()) {
    // Only do this when the complete bundle is made out of COPYs.
    MachineBasicBlock &MBB = *MI.getParent();
    for (MachineBasicBlock::reverse_instr_iterator I =
         std::next(MI.getReverseIterator()), E = MBB.instr_rend();
         I != E && I->isBundledWithSucc(); ++I) {
      if (!I->isCopy())
        return;
    }

    for (MachineBasicBlock::reverse_instr_iterator I = MI.getReverseIterator();
         I->isBundledWithPred(); ) {
      MachineInstr &MI = *I;
      ++I;

      MI.unbundleFromPred();
      if (Indexes)
        Indexes->insertMachineInstrInMaps(MI);
    }
  }
}
예제 #2
0
/// The liverange splitting logic sometimes produces bundles of copies when
/// subregisters are involved. Expand these into a sequence of copy instructions
/// after processing the last in the bundle. Does not update LiveIntervals
/// which we shouldn't need for this instruction anymore.
void VirtRegRewriter::expandCopyBundle(MachineInstr &MI) const {
  if (!MI.isCopy())
    return;

  if (MI.isBundledWithPred() && !MI.isBundledWithSucc()) {
    SmallVector<MachineInstr *, 2> MIs({&MI});

    // Only do this when the complete bundle is made out of COPYs.
    MachineBasicBlock &MBB = *MI.getParent();
    for (MachineBasicBlock::reverse_instr_iterator I =
         std::next(MI.getReverseIterator()), E = MBB.instr_rend();
         I != E && I->isBundledWithSucc(); ++I) {
      if (!I->isCopy())
        return;
      MIs.push_back(&*I);
    }
    MachineInstr *FirstMI = MIs.back();

    auto anyRegsAlias = [](const MachineInstr *Dst,
                           ArrayRef<MachineInstr *> Srcs,
                           const TargetRegisterInfo *TRI) {
      for (const MachineInstr *Src : Srcs)
        if (Src != Dst)
          if (TRI->regsOverlap(Dst->getOperand(0).getReg(),
                               Src->getOperand(1).getReg()))
            return true;
      return false;
    };

    // If any of the destination registers in the bundle of copies alias any of
    // the source registers, try to schedule the instructions to avoid any
    // clobbering.
    for (int E = MIs.size(), PrevE = E; E > 1; PrevE = E) {
      for (int I = E; I--; )
        if (!anyRegsAlias(MIs[I], makeArrayRef(MIs).take_front(E), TRI)) {
          if (I + 1 != E)
            std::swap(MIs[I], MIs[E - 1]);
          --E;
        }
      if (PrevE == E) {
        MF->getFunction().getContext().emitError(
            "register rewriting failed: cycle in copy bundle");
        break;
      }
    }

    MachineInstr *BundleStart = FirstMI;
    for (MachineInstr *BundledMI : llvm::reverse(MIs)) {
      // If instruction is in the middle of the bundle, move it before the
      // bundle starts, otherwise, just unbundle it. When we get to the last
      // instruction, the bundle will have been completely undone.
      if (BundledMI != BundleStart) {
        BundledMI->removeFromBundle();
        MBB.insert(FirstMI, BundledMI);
      } else if (BundledMI->isBundledWithSucc()) {
        BundledMI->unbundleFromSucc();
        BundleStart = &*std::next(BundledMI->getIterator());
      }

      if (Indexes && BundledMI != FirstMI)
        Indexes->insertMachineInstrInMaps(*BundledMI);
    }
  }
}