/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
/// abstract stack objects.
///
void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
  const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();

  bool StackGrowsDown =
    TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;

  // Loop over all of the stack objects, assigning sequential addresses...
  MachineFrameInfo *MFI = Fn.getFrameInfo();

  // Start at the beginning of the local area.
  // The Offset is the distance from the stack top in the direction
  // of stack growth -- so it's always nonnegative.
  int LocalAreaOffset = TFI.getOffsetOfLocalArea();
  if (StackGrowsDown)
    LocalAreaOffset = -LocalAreaOffset;
  assert(LocalAreaOffset >= 0
         && "Local area offset should be in direction of stack growth");
  int64_t Offset = LocalAreaOffset;

  // If there are fixed sized objects that are preallocated in the local area,
  // non-fixed objects can't be allocated right at the start of local area.
  // We currently don't support filling in holes in between fixed sized
  // objects, so we adjust 'Offset' to point to the end of last fixed sized
  // preallocated object.
  for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
    int64_t FixedOff;
    if (StackGrowsDown) {
      // The maximum distance from the stack pointer is at lower address of
      // the object -- which is given by offset. For down growing stack
      // the offset is negative, so we negate the offset to get the distance.
      FixedOff = -MFI->getObjectOffset(i);
    } else {
      // The maximum distance from the start pointer is at the upper
      // address of the object.
      FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
    }
    if (FixedOff > Offset) Offset = FixedOff;
  }

  // First assign frame offsets to stack objects that are used to spill
  // callee saved registers.
  if (StackGrowsDown) {
    for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
      // If the stack grows down, we need to add the size to find the lowest
      // address of the object.
      Offset += MFI->getObjectSize(i);

      unsigned Align = MFI->getObjectAlignment(i);
      // Adjust to alignment boundary
      Offset = (Offset+Align-1)/Align*Align;

      MFI->setObjectOffset(i, -Offset);        // Set the computed offset
    }
  } else {
    int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
    for (int i = MaxCSFI; i >= MinCSFI ; --i) {
      unsigned Align = MFI->getObjectAlignment(i);
      // Adjust to alignment boundary
      Offset = (Offset+Align-1)/Align*Align;

      MFI->setObjectOffset(i, Offset);
      Offset += MFI->getObjectSize(i);
    }
  }

  unsigned MaxAlign = MFI->getMaxAlignment();

  // Make sure the special register scavenging spill slot is closest to the
  // frame pointer if a frame pointer is required.
  const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
  if (RS && TFI.hasFP(Fn) && RegInfo->useFPForScavengingIndex(Fn) &&
      !RegInfo->needsStackRealignment(Fn)) {
    int SFI = RS->getScavengingFrameIndex();
    if (SFI >= 0)
      AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
  }

  // FIXME: Once this is working, then enable flag will change to a target
  // check for whether the frame is large enough to want to use virtual
  // frame index registers. Functions which don't want/need this optimization
  // will continue to use the existing code path.
  if (MFI->getUseLocalStackAllocationBlock()) {
    unsigned Align = MFI->getLocalFrameMaxAlign();

    // Adjust to alignment boundary.
    Offset = (Offset + Align - 1) / Align * Align;

    DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");

    // Resolve offsets for objects in the local block.
    for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
      std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
      int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
      DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" <<
            FIOffset << "]\n");
      MFI->setObjectOffset(Entry.first, FIOffset);
    }
    // Allocate the local block
    Offset += MFI->getLocalFrameSize();

    MaxAlign = std::max(Align, MaxAlign);
  }

  // Make sure that the stack protector comes before the local variables on the
  // stack.
  SmallSet<int, 16> LargeStackObjs;
  if (MFI->getStackProtectorIndex() >= 0) {
    AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
                      Offset, MaxAlign);

    // Assign large stack objects first.
    for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
      if (MFI->isObjectPreAllocated(i) &&
          MFI->getUseLocalStackAllocationBlock())
        continue;
      if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
        continue;
      if (RS && (int)i == RS->getScavengingFrameIndex())
        continue;
      if (MFI->isDeadObjectIndex(i))
        continue;
      if (MFI->getStackProtectorIndex() == (int)i)
        continue;
      if (!MFI->MayNeedStackProtector(i))
        continue;

      AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
      LargeStackObjs.insert(i);
    }
  }

  // Then assign frame offsets to stack objects that are not used to spill
  // callee saved registers.
  for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
    if (MFI->isObjectPreAllocated(i) &&
        MFI->getUseLocalStackAllocationBlock())
      continue;
    if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
      continue;
    if (RS && (int)i == RS->getScavengingFrameIndex())
      continue;
    if (MFI->isDeadObjectIndex(i))
      continue;
    if (MFI->getStackProtectorIndex() == (int)i)
      continue;
    if (LargeStackObjs.count(i))
      continue;

    AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
  }

  // Make sure the special register scavenging spill slot is closest to the
  // stack pointer.
  if (RS && (!TFI.hasFP(Fn) || RegInfo->needsStackRealignment(Fn) ||
             !RegInfo->useFPForScavengingIndex(Fn))) {
    int SFI = RS->getScavengingFrameIndex();
    if (SFI >= 0)
      AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
  }

  if (!TFI.targetHandlesStackFrameRounding()) {
    // If we have reserved argument space for call sites in the function
    // immediately on entry to the current function, count it as part of the
    // overall stack size.
    if (MFI->adjustsStack() && TFI.hasReservedCallFrame(Fn))
      Offset += MFI->getMaxCallFrameSize();

    // Round up the size to a multiple of the alignment.  If the function has
    // any calls or alloca's, align to the target's StackAlignment value to
    // ensure that the callee's frame or the alloca data is suitably aligned;
    // otherwise, for leaf functions, align to the TransientStackAlignment
    // value.
    unsigned StackAlign;
    if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
        (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
      StackAlign = TFI.getStackAlignment();
    else
      StackAlign = TFI.getTransientStackAlignment();

    // If the frame pointer is eliminated, all frame offsets will be relative to
    // SP not FP. Align to MaxAlign so this works.
    StackAlign = std::max(StackAlign, MaxAlign);
    unsigned AlignMask = StackAlign - 1;
    Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
  }

  // Update frame info to pretend that this is part of the stack...
  int64_t StackSize = Offset - LocalAreaOffset;
  MFI->setStackSize(StackSize);
  NumBytesStackSpace += StackSize;
}
bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
  // Scan the function's instructions looking for frame index references.
  // For each, ask the target if it wants a virtual base register for it
  // based on what we can tell it about where the local will end up in the
  // stack frame. If it wants one, re-use a suitable one we've previously
  // allocated, or if there isn't one that fits the bill, allocate a new one
  // and ask the target to create a defining instruction for it.
  bool UsedBaseReg = false;

  MachineFrameInfo *MFI = Fn.getFrameInfo();
  const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
  const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
  bool StackGrowsDown =
    TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;

  // Collect all of the instructions in the block that reference
  // a frame index. Also store the frame index referenced to ease later
  // lookup. (For any insn that has more than one FI reference, we arbitrarily
  // choose the first one).
  SmallVector<FrameRef, 64> FrameReferenceInsns;

  for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
    for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
      MachineInstr *MI = I;

      // Debug value, stackmap and patchpoint instructions can't be out of
      // range, so they don't need any updates.
      if (MI->isDebugValue() ||
          MI->getOpcode() == TargetOpcode::STATEPOINT ||
          MI->getOpcode() == TargetOpcode::STACKMAP ||
          MI->getOpcode() == TargetOpcode::PATCHPOINT)
        continue;

      // For now, allocate the base register(s) within the basic block
      // where they're used, and don't try to keep them around outside
      // of that. It may be beneficial to try sharing them more broadly
      // than that, but the increased register pressure makes that a
      // tricky thing to balance. Investigate if re-materializing these
      // becomes an issue.
      for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
        // Consider replacing all frame index operands that reference
        // an object allocated in the local block.
        if (MI->getOperand(i).isFI()) {
          // Don't try this with values not in the local block.
          if (!MFI->isObjectPreAllocated(MI->getOperand(i).getIndex()))
            break;
          int Idx = MI->getOperand(i).getIndex();
          int64_t LocalOffset = LocalOffsets[Idx];
          if (!TRI->needsFrameBaseReg(MI, LocalOffset))
            break;
          FrameReferenceInsns.
            push_back(FrameRef(MI, LocalOffset, Idx));
          break;
        }
      }
    }
  }

  // Sort the frame references by local offset
  array_pod_sort(FrameReferenceInsns.begin(), FrameReferenceInsns.end());

  MachineBasicBlock *Entry = Fn.begin();

  unsigned BaseReg = 0;
  int64_t BaseOffset = 0;

  // Loop through the frame references and allocate for them as necessary.
  for (int ref = 0, e = FrameReferenceInsns.size(); ref < e ; ++ref) {
    FrameRef &FR = FrameReferenceInsns[ref];
    MachineBasicBlock::iterator I = FR.getMachineInstr();
    MachineInstr *MI = I;
    int64_t LocalOffset = FR.getLocalOffset();
    int FrameIdx = FR.getFrameIndex();
    assert(MFI->isObjectPreAllocated(FrameIdx) &&
           "Only pre-allocated locals expected!");

    DEBUG(dbgs() << "Considering: " << *MI);

    unsigned idx = 0;
    for (unsigned f = MI->getNumOperands(); idx != f; ++idx) {
      if (!MI->getOperand(idx).isFI())
        continue;

      if (FrameIdx == I->getOperand(idx).getIndex())
        break;
    }

    assert(idx < MI->getNumOperands() && "Cannot find FI operand");

    int64_t Offset = 0;
    int64_t FrameSizeAdjust = StackGrowsDown ? MFI->getLocalFrameSize() : 0;

    DEBUG(dbgs() << "  Replacing FI in: " << *MI);

    // If we have a suitable base register available, use it; otherwise
    // create a new one. Note that any offset encoded in the
    // instruction itself will be taken into account by the target,
    // so we don't have to adjust for it here when reusing a base
    // register.
    if (UsedBaseReg && lookupCandidateBaseReg(BaseOffset, FrameSizeAdjust,
                                              LocalOffset, MI, TRI)) {
      DEBUG(dbgs() << "  Reusing base register " << BaseReg << "\n");
      // We found a register to reuse.
      Offset = FrameSizeAdjust + LocalOffset - BaseOffset;
    } else {
      // No previously defined register was in range, so create a // new one.
 
      int64_t InstrOffset = TRI->getFrameIndexInstrOffset(MI, idx);

      int64_t PrevBaseOffset = BaseOffset;
      BaseOffset = FrameSizeAdjust + LocalOffset + InstrOffset;

      // We'd like to avoid creating single-use virtual base registers.
      // Because the FrameRefs are in sorted order, and we've already
      // processed all FrameRefs before this one, just check whether or not
      // the next FrameRef will be able to reuse this new register. If not,
      // then don't bother creating it.
      bool CanReuse = false;
      for (int refn = ref + 1; refn < e; ++refn) {
        FrameRef &FRN = FrameReferenceInsns[refn];
        MachineBasicBlock::iterator J = FRN.getMachineInstr();
        MachineInstr *MIN = J;

        CanReuse = lookupCandidateBaseReg(BaseOffset, FrameSizeAdjust,
                                          FRN.getLocalOffset(), MIN, TRI);
        break;
      }

      if (!CanReuse) {
        BaseOffset = PrevBaseOffset;
        continue;
      }

      const MachineFunction *MF = MI->getParent()->getParent();
      const TargetRegisterClass *RC = TRI->getPointerRegClass(*MF);
      BaseReg = Fn.getRegInfo().createVirtualRegister(RC);

      DEBUG(dbgs() << "  Materializing base register " << BaseReg <<
            " at frame local offset " << LocalOffset + InstrOffset << "\n");

      // Tell the target to insert the instruction to initialize
      // the base register.
      //            MachineBasicBlock::iterator InsertionPt = Entry->begin();
      TRI->materializeFrameBaseRegister(Entry, BaseReg, FrameIdx,
                                        InstrOffset);

      // The base register already includes any offset specified
      // by the instruction, so account for that so it doesn't get
      // applied twice.
      Offset = -InstrOffset;

      ++NumBaseRegisters;
      UsedBaseReg = true;
    }
    assert(BaseReg != 0 && "Unable to allocate virtual base register!");

    // Modify the instruction to use the new base register rather
    // than the frame index operand.
    TRI->resolveFrameIndex(I, BaseReg, Offset);
    DEBUG(dbgs() << "Resolved: " << *MI);

    ++NumReplacements;
  }

  return UsedBaseReg;
}
示例#3
0
bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
  // Scan the function's instructions looking for frame index references.
  // For each, ask the target if it wants a virtual base register for it
  // based on what we can tell it about where the local will end up in the
  // stack frame. If it wants one, re-use a suitable one we've previously
  // allocated, or if there isn't one that fits the bill, allocate a new one
  // and ask the target to create a defining instruction for it.
  bool UsedBaseReg = false;

  MachineFrameInfo *MFI = Fn.getFrameInfo();
  const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
  const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
  bool StackGrowsDown =
    TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
  MachineBasicBlock::iterator InsertionPt = Fn.begin()->begin();

  // Collect all of the instructions in the block that reference
  // a frame index. Also store the frame index referenced to ease later
  // lookup. (For any insn that has more than one FI reference, we arbitrarily
  // choose the first one).
  SmallVector<FrameRef, 64> FrameReferenceInsns;
  // A base register definition is a register+offset pair.
  SmallVector<std::pair<unsigned, int64_t>, 8> BaseRegisters;


  for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
    for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
      MachineInstr *MI = I;
      // Debug value instructions can't be out of range, so they don't need
      // any updates.
      if (MI->isDebugValue())
        continue;
      // For now, allocate the base register(s) within the basic block
      // where they're used, and don't try to keep them around outside
      // of that. It may be beneficial to try sharing them more broadly
      // than that, but the increased register pressure makes that a
      // tricky thing to balance. Investigate if re-materializing these
      // becomes an issue.
      for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
        // Consider replacing all frame index operands that reference
        // an object allocated in the local block.
        if (MI->getOperand(i).isFI()) {
          // Don't try this with values not in the local block.
          if (!MFI->isObjectPreAllocated(MI->getOperand(i).getIndex()))
            break;
          FrameReferenceInsns.
            push_back(FrameRef(MI, LocalOffsets[MI->getOperand(i).getIndex()]));
          break;
        }
      }
    }
  }
  // Sort the frame references by local offset
  array_pod_sort(FrameReferenceInsns.begin(), FrameReferenceInsns.end());


  // Loop throught the frame references and allocate for them as necessary
  for (int ref = 0, e = FrameReferenceInsns.size(); ref < e ; ++ref) {
    MachineBasicBlock::iterator I =
      FrameReferenceInsns[ref].getMachineInstr();
    MachineInstr *MI = I;
    for (unsigned idx = 0, e = MI->getNumOperands(); idx != e; ++idx) {
      // Consider replacing all frame index operands that reference
      // an object allocated in the local block.
      if (MI->getOperand(idx).isFI()) {
        int FrameIdx = MI->getOperand(idx).getIndex();

        assert(MFI->isObjectPreAllocated(FrameIdx) &&
               "Only pre-allocated locals expected!");

        DEBUG(dbgs() << "Considering: " << *MI);
        if (TRI->needsFrameBaseReg(MI, LocalOffsets[FrameIdx])) {
          unsigned BaseReg = 0;
          int64_t Offset = 0;
          int64_t FrameSizeAdjust =
            StackGrowsDown ? MFI->getLocalFrameSize() : 0;

          DEBUG(dbgs() << "  Replacing FI in: " << *MI);

          // If we have a suitable base register available, use it; otherwise
          // create a new one. Note that any offset encoded in the
          // instruction itself will be taken into account by the target,
          // so we don't have to adjust for it here when reusing a base
          // register.
          std::pair<unsigned, int64_t> RegOffset;
          if (lookupCandidateBaseReg(BaseRegisters, RegOffset,
                                     FrameSizeAdjust,
                                     LocalOffsets[FrameIdx],
                                     MI, TRI)) {
            DEBUG(dbgs() << "  Reusing base register " <<
                  RegOffset.first << "\n");
            // We found a register to reuse.
            BaseReg = RegOffset.first;
            Offset = FrameSizeAdjust + LocalOffsets[FrameIdx] -
              RegOffset.second;
          } else {
            // No previously defined register was in range, so create a
            // new one.
            int64_t InstrOffset = TRI->getFrameIndexInstrOffset(MI, idx);
            const TargetRegisterClass *RC = TRI->getPointerRegClass();
            BaseReg = Fn.getRegInfo().createVirtualRegister(RC);

            DEBUG(dbgs() << "  Materializing base register " << BaseReg <<
                  " at frame local offset " <<
                  LocalOffsets[FrameIdx] + InstrOffset << "\n");
            // Tell the target to insert the instruction to initialize
            // the base register.
            TRI->materializeFrameBaseRegister(InsertionPt, BaseReg,
                                              FrameIdx, InstrOffset);

            // The base register already includes any offset specified
            // by the instruction, so account for that so it doesn't get
            // applied twice.
            Offset = -InstrOffset;

            int64_t BaseOffset = FrameSizeAdjust + LocalOffsets[FrameIdx] +
              InstrOffset;
            BaseRegisters.push_back(
              std::pair<unsigned, int64_t>(BaseReg, BaseOffset));
            ++NumBaseRegisters;
            UsedBaseReg = true;
          }
          assert(BaseReg != 0 && "Unable to allocate virtual base register!");

          // Modify the instruction to use the new base register rather
          // than the frame index operand.
          TRI->resolveFrameIndex(I, BaseReg, Offset);
          DEBUG(dbgs() << "Resolved: " << *MI);

          ++NumReplacements;
        }
      }
    }
  }
  return UsedBaseReg;
}
示例#4
0
/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
/// abstract stack objects.
///
void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
  const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering();
  StackProtector *SP = &getAnalysis<StackProtector>();

  bool StackGrowsDown =
    TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;

  // Loop over all of the stack objects, assigning sequential addresses...
  MachineFrameInfo *MFI = Fn.getFrameInfo();

  // Start at the beginning of the local area.
  // The Offset is the distance from the stack top in the direction
  // of stack growth -- so it's always nonnegative.
  int LocalAreaOffset = TFI.getOffsetOfLocalArea();
  if (StackGrowsDown)
    LocalAreaOffset = -LocalAreaOffset;
  assert(LocalAreaOffset >= 0
         && "Local area offset should be in direction of stack growth");
  int64_t Offset = LocalAreaOffset;

  // Skew to be applied to alignment.
  unsigned Skew = TFI.getStackAlignmentSkew(Fn);

  // If there are fixed sized objects that are preallocated in the local area,
  // non-fixed objects can't be allocated right at the start of local area.
  // We currently don't support filling in holes in between fixed sized
  // objects, so we adjust 'Offset' to point to the end of last fixed sized
  // preallocated object.
  for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
    int64_t FixedOff;
    if (StackGrowsDown) {
      // The maximum distance from the stack pointer is at lower address of
      // the object -- which is given by offset. For down growing stack
      // the offset is negative, so we negate the offset to get the distance.
      FixedOff = -MFI->getObjectOffset(i);
    } else {
      // The maximum distance from the start pointer is at the upper
      // address of the object.
      FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
    }
    if (FixedOff > Offset) Offset = FixedOff;
  }

  // First assign frame offsets to stack objects that are used to spill
  // callee saved registers.
  if (StackGrowsDown) {
    for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
      // If the stack grows down, we need to add the size to find the lowest
      // address of the object.
      Offset += MFI->getObjectSize(i);

      unsigned Align = MFI->getObjectAlignment(i);
      // Adjust to alignment boundary
      Offset = alignTo(Offset, Align, Skew);

      DEBUG(dbgs() << "alloc FI(" << i << ") at SP[" << -Offset << "]\n");
      MFI->setObjectOffset(i, -Offset);        // Set the computed offset
    }
  } else {
    int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
    for (int i = MaxCSFI; i >= MinCSFI ; --i) {
      unsigned Align = MFI->getObjectAlignment(i);
      // Adjust to alignment boundary
      Offset = alignTo(Offset, Align, Skew);

      DEBUG(dbgs() << "alloc FI(" << i << ") at SP[" << Offset << "]\n");
      MFI->setObjectOffset(i, Offset);
      Offset += MFI->getObjectSize(i);
    }
  }

  unsigned MaxAlign = MFI->getMaxAlignment();

  // Make sure the special register scavenging spill slot is closest to the
  // incoming stack pointer if a frame pointer is required and is closer
  // to the incoming rather than the final stack pointer.
  const TargetRegisterInfo *RegInfo = Fn.getSubtarget().getRegisterInfo();
  bool EarlyScavengingSlots = (TFI.hasFP(Fn) &&
                               TFI.isFPCloseToIncomingSP() &&
                               RegInfo->useFPForScavengingIndex(Fn) &&
                               !RegInfo->needsStackRealignment(Fn));
  if (RS && EarlyScavengingSlots) {
    SmallVector<int, 2> SFIs;
    RS->getScavengingFrameIndices(SFIs);
    for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
           IE = SFIs.end(); I != IE; ++I)
      AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign, Skew);
  }

  // FIXME: Once this is working, then enable flag will change to a target
  // check for whether the frame is large enough to want to use virtual
  // frame index registers. Functions which don't want/need this optimization
  // will continue to use the existing code path.
  if (MFI->getUseLocalStackAllocationBlock()) {
    unsigned Align = MFI->getLocalFrameMaxAlign();

    // Adjust to alignment boundary.
    Offset = alignTo(Offset, Align, Skew);

    DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");

    // Resolve offsets for objects in the local block.
    for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
      std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
      int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
      DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" <<
            FIOffset << "]\n");
      MFI->setObjectOffset(Entry.first, FIOffset);
    }
    // Allocate the local block
    Offset += MFI->getLocalFrameSize();

    MaxAlign = std::max(Align, MaxAlign);
  }

  // Make sure that the stack protector comes before the local variables on the
  // stack.
  SmallSet<int, 16> ProtectedObjs;
  if (MFI->getStackProtectorIndex() >= 0) {
    StackObjSet LargeArrayObjs;
    StackObjSet SmallArrayObjs;
    StackObjSet AddrOfObjs;

    AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
                      Offset, MaxAlign, Skew);

    // Assign large stack objects first.
    for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
      if (MFI->isObjectPreAllocated(i) &&
          MFI->getUseLocalStackAllocationBlock())
        continue;
      if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
        continue;
      if (RS && RS->isScavengingFrameIndex((int)i))
        continue;
      if (MFI->isDeadObjectIndex(i))
        continue;
      if (MFI->getStackProtectorIndex() == (int)i)
        continue;

      switch (SP->getSSPLayout(MFI->getObjectAllocation(i))) {
      case StackProtector::SSPLK_None:
        continue;
      case StackProtector::SSPLK_SmallArray:
        SmallArrayObjs.insert(i);
        continue;
      case StackProtector::SSPLK_AddrOf:
        AddrOfObjs.insert(i);
        continue;
      case StackProtector::SSPLK_LargeArray:
        LargeArrayObjs.insert(i);
        continue;
      }
      llvm_unreachable("Unexpected SSPLayoutKind.");
    }

    AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
                          Offset, MaxAlign, Skew);
    AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
                          Offset, MaxAlign, Skew);
    AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown,
                          Offset, MaxAlign, Skew);
  }

  SmallVector<int, 8> ObjectsToAllocate;

  int EHRegNodeFrameIndex = INT_MAX;
  if (const WinEHFuncInfo *FuncInfo = Fn.getWinEHFuncInfo())
    EHRegNodeFrameIndex = FuncInfo->EHRegNodeFrameIndex;

  // Then prepare to assign frame offsets to stack objects that are not used to
  // spill callee saved registers.
  for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
    if (MFI->isObjectPreAllocated(i) &&
        MFI->getUseLocalStackAllocationBlock())
      continue;
    if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
      continue;
    if (RS && RS->isScavengingFrameIndex((int)i))
      continue;
    if (MFI->isDeadObjectIndex(i))
      continue;
    if (MFI->getStackProtectorIndex() == (int)i)
      continue;
    if (EHRegNodeFrameIndex == (int)i)
      continue;
    if (ProtectedObjs.count(i))
      continue;

    // Add the objects that we need to allocate to our working set.
    ObjectsToAllocate.push_back(i);
  }

  // Allocate the EH registration node first if one is present.
  if (EHRegNodeFrameIndex != INT_MAX)
    AdjustStackOffset(MFI, EHRegNodeFrameIndex, StackGrowsDown, Offset,
                      MaxAlign, Skew);

  // Give the targets a chance to order the objects the way they like it.
  if (Fn.getTarget().getOptLevel() != CodeGenOpt::None &&
      Fn.getTarget().Options.StackSymbolOrdering)
    TFI.orderFrameObjects(Fn, ObjectsToAllocate);
  
  // Now walk the objects and actually assign base offsets to them.
  for (auto &Object : ObjectsToAllocate)
    AdjustStackOffset(MFI, Object, StackGrowsDown, Offset, MaxAlign, Skew);

  // Make sure the special register scavenging spill slot is closest to the
  // stack pointer.
  if (RS && !EarlyScavengingSlots) {
    SmallVector<int, 2> SFIs;
    RS->getScavengingFrameIndices(SFIs);
    for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
           IE = SFIs.end(); I != IE; ++I)
      AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign, Skew);
  }

  if (!TFI.targetHandlesStackFrameRounding()) {
    // If we have reserved argument space for call sites in the function
    // immediately on entry to the current function, count it as part of the
    // overall stack size.
    if (MFI->adjustsStack() && TFI.hasReservedCallFrame(Fn))
      Offset += MFI->getMaxCallFrameSize();

    // Round up the size to a multiple of the alignment.  If the function has
    // any calls or alloca's, align to the target's StackAlignment value to
    // ensure that the callee's frame or the alloca data is suitably aligned;
    // otherwise, for leaf functions, align to the TransientStackAlignment
    // value.
    unsigned StackAlign;
    if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
        (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
      StackAlign = TFI.getStackAlignment();
    else
      StackAlign = TFI.getTransientStackAlignment();

    // If the frame pointer is eliminated, all frame offsets will be relative to
    // SP not FP. Align to MaxAlign so this works.
    StackAlign = std::max(StackAlign, MaxAlign);
    Offset = alignTo(Offset, StackAlign, Skew);
  }

  // Update frame info to pretend that this is part of the stack...
  int64_t StackSize = Offset - LocalAreaOffset;
  MFI->setStackSize(StackSize);
  NumBytesStackSpace += StackSize;
}