/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
/// abstract stack objects.
///
void LocalStackSlotPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
  // Loop over all of the stack objects, assigning sequential addresses...
  MachineFrameInfo *MFI = Fn.getFrameInfo();
  const TargetFrameLowering &TFI = *Fn.getTarget().getFrameLowering();
  bool StackGrowsDown =
    TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
  int64_t Offset = 0;
  unsigned MaxAlign = 0;
  StackProtector *SP = &getAnalysis<StackProtector>();

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

    // Assign large stack objects first.
    for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
      if (MFI->isDeadObjectIndex(i))
        continue;
      if (MFI->getStackProtectorIndex() == (int)i)
        continue;

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

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

  // 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->isDeadObjectIndex(i))
      continue;
    if (MFI->getStackProtectorIndex() == (int)i)
      continue;
    if (ProtectedObjs.count(i))
      continue;

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

  // Remember how big this blob of stack space is
  MFI->setLocalFrameSize(Offset);
  MFI->setLocalFrameMaxAlign(MaxAlign);
}
/// AssignProtectedObjSet - Helper function to assign large stack objects (i.e.,
/// those required to be close to the Stack Protector) to stack offsets.
void LocalStackSlotPass::AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
                                           SmallSet<int, 16> &ProtectedObjs,
                                           MachineFrameInfo &MFI,
                                           bool StackGrowsDown, int64_t &Offset,
                                           unsigned &MaxAlign) {
  for (StackObjSet::const_iterator I = UnassignedObjs.begin(),
        E = UnassignedObjs.end(); I != E; ++I) {
    int i = *I;
    AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign);
    ProtectedObjs.insert(i);
  }
}
Exemplo n.º 3
0
/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
/// abstract stack objects.
void PEI::calculateFrameObjectOffsets(MachineFunction &MF) {
  const TargetFrameLowering &TFI = *MF.getSubtarget().getFrameLowering();

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

  // Loop over all of the stack objects, assigning sequential addresses...
  MachineFrameInfo &MFI = MF.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(MF);

  // 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.
  // 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);

      LLVM_DEBUG(dbgs() << "alloc FI(" << i << ") at SP[" << -Offset << "]\n");
      MFI.setObjectOffset(i, -Offset);        // Set the computed offset
    }
  } else if (MaxCSFrameIndex >= MinCSFrameIndex) {
    // Be careful about underflow in comparisons agains MinCSFrameIndex.
    for (unsigned i = MaxCSFrameIndex; i != MinCSFrameIndex - 1; --i) {
      if (MFI.isDeadObjectIndex(i))
        continue;

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

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

  // FixedCSEnd is the stack offset to the end of the fixed and callee-save
  // stack area.
  int64_t FixedCSEnd = Offset;
  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 = MF.getSubtarget().getRegisterInfo();
  bool EarlyScavengingSlots = (TFI.hasFP(MF) &&
                               TFI.isFPCloseToIncomingSP() &&
                               RegInfo->useFPForScavengingIndex(MF) &&
                               !RegInfo->needsStackRealignment(MF));
  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);

    LLVM_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;
      LLVM_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);
  }

  // Retrieve the Exception Handler registration node.
  int EHRegNodeFrameIndex = std::numeric_limits<int>::max();
  if (const WinEHFuncInfo *FuncInfo = MF.getWinEHFuncInfo())
    EHRegNodeFrameIndex = FuncInfo->EHRegNodeFrameIndex;

  // 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 ||
          EHRegNodeFrameIndex == (int)i)
        continue;

      switch (MFI.getObjectSSPLayout(i)) {
      case MachineFrameInfo::SSPLK_None:
        continue;
      case MachineFrameInfo::SSPLK_SmallArray:
        SmallArrayObjs.insert(i);
        continue;
      case MachineFrameInfo::SSPLK_AddrOf:
        AddrOfObjs.insert(i);
        continue;
      case MachineFrameInfo::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;

  // 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 ||
        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 != std::numeric_limits<int>::max())
    AdjustStackOffset(MFI, EHRegNodeFrameIndex, StackGrowsDown, Offset,
                      MaxAlign, Skew);

  // Give the targets a chance to order the objects the way they like it.
  if (MF.getTarget().getOptLevel() != CodeGenOpt::None &&
      MF.getTarget().Options.StackSymbolOrdering)
    TFI.orderFrameObjects(MF, ObjectsToAllocate);

  // Keep track of which bytes in the fixed and callee-save range are used so we
  // can use the holes when allocating later stack objects.  Only do this if
  // stack protector isn't being used and the target requests it and we're
  // optimizing.
  BitVector StackBytesFree;
  if (!ObjectsToAllocate.empty() &&
      MF.getTarget().getOptLevel() != CodeGenOpt::None &&
      MFI.getStackProtectorIndex() < 0 && TFI.enableStackSlotScavenging(MF))
    computeFreeStackSlots(MFI, StackGrowsDown, MinCSFrameIndex, MaxCSFrameIndex,
                          FixedCSEnd, StackBytesFree);

  // Now walk the objects and actually assign base offsets to them.
  for (auto &Object : ObjectsToAllocate)
    if (!scavengeStackSlot(MFI, Object, StackGrowsDown, MaxAlign,
                           StackBytesFree))
      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(MF))
      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(MF) && 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;
}
Exemplo n.º 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;

  // 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 = RoundUpToAlignment(Offset, 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 = RoundUpToAlignment(Offset, 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
  // 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);
  }

  // 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 = RoundUpToAlignment(Offset, 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> ProtectedObjs;
  if (MFI->getStackProtectorIndex() >= 0) {
    StackObjSet LargeArrayObjs;
    StackObjSet SmallArrayObjs;
    StackObjSet AddrOfObjs;

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

  // 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 && RS->isScavengingFrameIndex((int)i))
      continue;
    if (MFI->isDeadObjectIndex(i))
      continue;
    if (MFI->getStackProtectorIndex() == (int)i)
      continue;
    if (ProtectedObjs.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 && !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);
  }

  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 = RoundUpToAlignment(Offset, StackAlign);
  }

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