Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// The file defines the MachineFrameInfo class.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H

#define LLVM_CODEGEN_MACHINEFRAMEINFO_H

#include "llvm/ADT/SmallVector.h"

#include "llvm/CodeGen/Register.h"

#include "llvm/CodeGen/TargetFrameLowering.h"

#include "llvm/Support/Alignment.h"

#include <cassert>

#include <vector>

namespace llvm {

class raw_ostream;

class MachineFunction;

class MachineBasicBlock;

class BitVector;

class AllocaInst;

/// The CalleeSavedInfo class tracks the information need to locate where a

/// callee saved register is in the current frame.

/// Callee saved reg can also be saved to a different register rather than

/// on the stack by setting DstReg instead of FrameIdx.

class CalleeSavedInfo {

  Register Reg;

  union {

    int FrameIdx;

    unsigned DstReg;

  };

  /// Flag indicating whether the register is actually restored in the epilog.

  /// In most cases, if a register is saved, it is also restored. There are

  /// some situations, though, when this is not the case. For example, the

  /// LR register on ARM is usually saved, but on exit from the function its

  /// saved value may be loaded directly into PC. Since liveness tracking of

  /// physical registers treats callee-saved registers are live outside of

  /// the function, LR would be treated as live-on-exit, even though in these

  /// scenarios it is not. This flag is added to indicate that the saved

  /// register described by this object is not restored in the epilog.

  /// The long-term solution is to model the liveness of callee-saved registers

  /// by implicit uses on the return instructions, however, the required

  /// changes in the ARM backend would be quite extensive.

  bool Restored = true;

  /// Flag indicating whether the register is spilled to stack or another

  /// register.

  bool SpilledToReg = false;

public:

  explicit CalleeSavedInfo(unsigned R, int FI = 0) : Reg(R), FrameIdx(FI) {}

  // Accessors.

  Register getReg()                        const { return Reg; }

  int getFrameIdx()                        const { return FrameIdx; }

  unsigned getDstReg()                     const { return DstReg; }

  void setFrameIdx(int FI) {

    FrameIdx = FI;

    SpilledToReg = false;

  }

  void setDstReg(Register SpillReg) {

    DstReg = SpillReg;

    SpilledToReg = true;

  }

  bool isRestored()                        const { return Restored; }

  void setRestored(bool R)                       { Restored = R; }

  bool isSpilledToReg()                    const { return SpilledToReg; }

};

/// The MachineFrameInfo class represents an abstract stack frame until

/// prolog/epilog code is inserted.  This class is key to allowing stack frame

/// representation optimizations, such as frame pointer elimination.  It also

/// allows more mundane (but still important) optimizations, such as reordering

/// of abstract objects on the stack frame.

///

/// To support this, the class assigns unique integer identifiers to stack

/// objects requested clients.  These identifiers are negative integers for

/// fixed stack objects (such as arguments passed on the stack) or nonnegative

/// for objects that may be reordered.  Instructions which refer to stack

/// objects use a special MO_FrameIndex operand to represent these frame

/// indexes.

///

/// Because this class keeps track of all references to the stack frame, it

/// knows when a variable sized object is allocated on the stack.  This is the

/// sole condition which prevents frame pointer elimination, which is an

/// important optimization on register-poor architectures.  Because original

/// variable sized alloca's in the source program are the only source of

/// variable sized stack objects, it is safe to decide whether there will be

/// any variable sized objects before all stack objects are known (for

/// example, register allocator spill code never needs variable sized

/// objects).

///

/// When prolog/epilog code emission is performed, the final stack frame is

/// built and the machine instructions are modified to refer to the actual

/// stack offsets of the object, eliminating all MO_FrameIndex operands from

/// the program.

///

/// Abstract Stack Frame Information

class MachineFrameInfo {

public:

  /// Stack Smashing Protection (SSP) rules require that vulnerable stack

  /// allocations are located close the stack protector.

  enum SSPLayoutKind {

    SSPLK_None,       ///< Did not trigger a stack protector.  No effect on data

                      ///< layout.

    SSPLK_LargeArray, ///< Array or nested array >= SSP-buffer-size.  Closest

                      ///< to the stack protector.

    SSPLK_SmallArray, ///< Array or nested array < SSP-buffer-size. 2nd closest

                      ///< to the stack protector.

    SSPLK_AddrOf      ///< The address of this allocation is exposed and

                      ///< triggered protection.  3rd closest to the protector.

  };

private:

  // Represent a single object allocated on the stack.

  struct StackObject {

    // The offset of this object from the stack pointer on entry to

    // the function.  This field has no meaning for a variable sized element.

    int64_t SPOffset;

    // The size of this object on the stack. 0 means a variable sized object,

    // ~0ULL means a dead object.

    uint64_t Size;

    // The required alignment of this stack slot.

    Align Alignment;

    // If true, the value of the stack object is set before

    // entering the function and is not modified inside the function. By

    // default, fixed objects are immutable unless marked otherwise.

    bool isImmutable;

    // If true the stack object is used as spill slot. It

    // cannot alias any other memory objects.

    bool isSpillSlot;

    /// If true, this stack slot is used to spill a value (could be deopt

    /// and/or GC related) over a statepoint. We know that the address of the

    /// slot can't alias any LLVM IR value.  This is very similar to a Spill

    /// Slot, but is created by statepoint lowering is SelectionDAG, not the

    /// register allocator.

    bool isStatepointSpillSlot = false;

    /// Identifier for stack memory type analagous to address space. If this is

    /// non-0, the meaning is target defined. Offsets cannot be directly

    /// compared between objects with different stack IDs. The object may not

    /// necessarily reside in the same contiguous memory block as other stack

    /// objects. Objects with differing stack IDs should not be merged or

    /// replaced substituted for each other.

    //

    /// It is assumed a target uses consecutive, increasing stack IDs starting

    /// from 1.

    uint8_t StackID;

    /// If this stack object is originated from an Alloca instruction

    /// this value saves the original IR allocation. Can be NULL.

    const AllocaInst *Alloca;

    // If true, the object was mapped into the local frame

    // block and doesn't need additional handling for allocation beyond that.

    bool PreAllocated = false;

    // If true, an LLVM IR value might point to this object.

    // Normally, spill slots and fixed-offset objects don't alias IR-accessible

    // objects, but there are exceptions (on PowerPC, for example, some byval

    // arguments have ABI-prescribed offsets).

    bool isAliased;

    /// If true, the object has been zero-extended.

    bool isZExt = false;

    /// If true, the object has been sign-extended.

    bool isSExt = false;

    uint8_t SSPLayout = SSPLK_None;

    StackObject(uint64_t Size, Align Alignment, int64_t SPOffset,

                bool IsImmutable, bool IsSpillSlot, const AllocaInst *Alloca,

                bool IsAliased, uint8_t StackID = 0)

        : SPOffset(SPOffset), Size(Size), Alignment(Alignment),

          isImmutable(IsImmutable), isSpillSlot(IsSpillSlot), StackID(StackID),

          Alloca(Alloca), isAliased(IsAliased) {}

  };

  /// The alignment of the stack.

  Align StackAlignment;

  /// Can the stack be realigned. This can be false if the target does not

  /// support stack realignment, or if the user asks us not to realign the

  /// stack. In this situation, overaligned allocas are all treated as dynamic

  /// allocations and the target must handle them as part of DYNAMIC_STACKALLOC

  /// lowering. All non-alloca stack objects have their alignment clamped to the

  /// base ABI stack alignment.

  /// FIXME: There is room for improvement in this case, in terms of

  /// grouping overaligned allocas into a "secondary stack frame" and

  /// then only use a single alloca to allocate this frame and only a

  /// single virtual register to access it. Currently, without such an

  /// optimization, each such alloca gets its own dynamic realignment.

  bool StackRealignable;

  /// Whether the function has the \c alignstack attribute.

  bool ForcedRealign;

  /// The list of stack objects allocated.

  std::vector<StackObject> Objects;

  /// This contains the number of fixed objects contained on

  /// the stack.  Because fixed objects are stored at a negative index in the

  /// Objects list, this is also the index to the 0th object in the list.

  unsigned NumFixedObjects = 0;

  /// This boolean keeps track of whether any variable

  /// sized objects have been allocated yet.

  bool HasVarSizedObjects = false;

  /// This boolean keeps track of whether there is a call

  /// to builtin \@llvm.frameaddress.

  bool FrameAddressTaken = false;

  /// This boolean keeps track of whether there is a call

  /// to builtin \@llvm.returnaddress.

  bool ReturnAddressTaken = false;

  /// This boolean keeps track of whether there is a call

  /// to builtin \@llvm.experimental.stackmap.

  bool HasStackMap = false;

  /// This boolean keeps track of whether there is a call

  /// to builtin \@llvm.experimental.patchpoint.

  bool HasPatchPoint = false;

  /// The prolog/epilog code inserter calculates the final stack

  /// offsets for all of the fixed size objects, updating the Objects list

  /// above.  It then updates StackSize to contain the number of bytes that need

  /// to be allocated on entry to the function.

  uint64_t StackSize = 0;

  /// The amount that a frame offset needs to be adjusted to

  /// have the actual offset from the stack/frame pointer.  The exact usage of

  /// this is target-dependent, but it is typically used to adjust between

  /// SP-relative and FP-relative offsets.  E.G., if objects are accessed via

  /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set

  /// to the distance between the initial SP and the value in FP.  For many

  /// targets, this value is only used when generating debug info (via

  /// TargetRegisterInfo::getFrameIndexReference); when generating code, the

  /// corresponding adjustments are performed directly.

  int OffsetAdjustment = 0;

  /// The prolog/epilog code inserter may process objects that require greater

  /// alignment than the default alignment the target provides.

  /// To handle this, MaxAlignment is set to the maximum alignment

  /// needed by the objects on the current frame.  If this is greater than the

  /// native alignment maintained by the compiler, dynamic alignment code will

  /// be needed.

  ///

  Align MaxAlignment;

  /// Set to true if this function adjusts the stack -- e.g.,

  /// when calling another function. This is only valid during and after

  /// prolog/epilog code insertion.

  bool AdjustsStack = false;

  /// Set to true if this function has any function calls.

  bool HasCalls = false;

  /// The frame index for the stack protector.

  int StackProtectorIdx = -1;

  /// The frame index for the function context. Used for SjLj exceptions.

  int FunctionContextIdx = -1;

  /// This contains the size of the largest call frame if the target uses frame

  /// setup/destroy pseudo instructions (as defined in the TargetFrameInfo

  /// class).  This information is important for frame pointer elimination.

  /// It is only valid during and after prolog/epilog code insertion.

  unsigned MaxCallFrameSize = ~0u;

  /// The number of bytes of callee saved registers that the target wants to

  /// report for the current function in the CodeView S_FRAMEPROC record.

  unsigned CVBytesOfCalleeSavedRegisters = 0;

  /// The prolog/epilog code inserter fills in this vector with each

  /// callee saved register saved in either the frame or a different

  /// register.  Beyond its use by the prolog/ epilog code inserter,

  /// this data is used for debug info and exception handling.

  std::vector<CalleeSavedInfo> CSInfo;

  /// Has CSInfo been set yet?

  bool CSIValid = false;

  /// References to frame indices which are mapped

  /// into the local frame allocation block. <FrameIdx, LocalOffset>

  SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;

  /// Size of the pre-allocated local frame block.

  int64_t LocalFrameSize = 0;

  /// Required alignment of the local object blob, which is the strictest

  /// alignment of any object in it.

  Align LocalFrameMaxAlign;

  /// Whether the local object blob needs to be allocated together. If not,

  /// PEI should ignore the isPreAllocated flags on the stack objects and

  /// just allocate them normally.

  bool UseLocalStackAllocationBlock = false;

  /// True if the function dynamically adjusts the stack pointer through some

  /// opaque mechanism like inline assembly or Win32 EH.

  bool HasOpaqueSPAdjustment = false;

  /// True if the function contains operations which will lower down to

  /// instructions which manipulate the stack pointer.

  bool HasCopyImplyingStackAdjustment = false;

  /// True if the function contains a call to the llvm.vastart intrinsic.

  bool HasVAStart = false;

  /// True if this is a varargs function that contains a musttail call.

  bool HasMustTailInVarArgFunc = false;

  /// True if this function contains a tail call. If so immutable objects like

  /// function arguments are no longer so. A tail call *can* override fixed

  /// stack objects like arguments so we can't treat them as immutable.

  bool HasTailCall = false;

  /// Not null, if shrink-wrapping found a better place for the prologue.

  MachineBasicBlock *Save = nullptr;

  /// Not null, if shrink-wrapping found a better place for the epilogue.

  MachineBasicBlock *Restore = nullptr;

  /// Size of the UnsafeStack Frame

  uint64_t UnsafeStackSize = 0;

public:

  explicit MachineFrameInfo(Align StackAlignment, bool StackRealignable,

                            bool ForcedRealign)

      : StackAlignment(StackAlignment),

        StackRealignable(StackRealignable), ForcedRealign(ForcedRealign) {}

  MachineFrameInfo(const MachineFrameInfo &) = delete;

  /// Return true if there are any stack objects in this function.

  bool hasStackObjects() const { return !Objects.empty(); }

  /// This method may be called any time after instruction

  /// selection is complete to determine if the stack frame for this function

  /// contains any variable sized objects.

  bool hasVarSizedObjects() const { return HasVarSizedObjects; }

  /// Return the index for the stack protector object.

  int getStackProtectorIndex() const { return StackProtectorIdx; }

  void setStackProtectorIndex(int I) { StackProtectorIdx = I; }

  bool hasStackProtectorIndex() const { return StackProtectorIdx != -1; }

  /// Return the index for the function context object.

  /// This object is used for SjLj exceptions.

  int getFunctionContextIndex() const { return FunctionContextIdx; }

  void setFunctionContextIndex(int I) { FunctionContextIdx = I; }

  bool hasFunctionContextIndex() const { return FunctionContextIdx != -1; }

  /// This method may be called any time after instruction

  /// selection is complete to determine if there is a call to

  /// \@llvm.frameaddress in this function.

  bool isFrameAddressTaken() const { return FrameAddressTaken; }

  void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }

  /// This method may be called any time after

  /// instruction selection is complete to determine if there is a call to

  /// \@llvm.returnaddress in this function.

  bool isReturnAddressTaken() const { return ReturnAddressTaken; }

  void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }

  /// This method may be called any time after instruction

  /// selection is complete to determine if there is a call to builtin

  /// \@llvm.experimental.stackmap.

  bool hasStackMap() const { return HasStackMap; }

  void setHasStackMap(bool s = true) { HasStackMap = s; }

  /// This method may be called any time after instruction

  /// selection is complete to determine if there is a call to builtin

  /// \@llvm.experimental.patchpoint.

  bool hasPatchPoint() const { return HasPatchPoint; }

  void setHasPatchPoint(bool s = true) { HasPatchPoint = s; }

  /// Return true if this function requires a split stack prolog, even if it

  /// uses no stack space. This is only meaningful for functions where

  /// MachineFunction::shouldSplitStack() returns true.

  //

  // For non-leaf functions we have to allow for the possibility that the call

  // is to a non-split function, as in PR37807. This function could also take

  // the address of a non-split function. When the linker tries to adjust its

  // non-existent prologue, it would fail with an error. Mark the object file so

  // that such failures are not errors. See this Go language bug-report

  // https://go-review.googlesource.com/c/go/+/148819/

  bool needsSplitStackProlog() const {

    return getStackSize() != 0 || hasTailCall();

  }

  /// Return the minimum frame object index.

  int getObjectIndexBegin() const { return -NumFixedObjects; }

  /// Return one past the maximum frame object index.

  int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }

  /// Return the number of fixed objects.

  unsigned getNumFixedObjects() const { return NumFixedObjects; }

  /// Return the number of objects.

  unsigned getNumObjects() const { return Objects.size(); }

  /// Map a frame index into the local object block

  void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {

    LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));

    Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;

  }

  /// Get the local offset mapping for a for an object.

  std::pair<int, int64_t> getLocalFrameObjectMap(int i) const {

    assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&

            "Invalid local object reference!");

    return LocalFrameObjects[i];

  }

  /// Return the number of objects allocated into the local object block.

  int64_t getLocalFrameObjectCount() const { return LocalFrameObjects.size(); }

  /// Set the size of the local object blob.

  void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }

  /// Get the size of the local object blob.

  int64_t getLocalFrameSize() const { return LocalFrameSize; }

  /// Required alignment of the local object blob,

  /// which is the strictest alignment of any object in it.

  void setLocalFrameMaxAlign(Align Alignment) {

    LocalFrameMaxAlign = Alignment;

  }

  /// Return the required alignment of the local object blob.

  Align getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }

  /// Get whether the local allocation blob should be allocated together or

  /// let PEI allocate the locals in it directly.

  bool getUseLocalStackAllocationBlock() const {

    return UseLocalStackAllocationBlock;

  }

  /// setUseLocalStackAllocationBlock - Set whether the local allocation blob

  /// should be allocated together or let PEI allocate the locals in it

  /// directly.

  void setUseLocalStackAllocationBlock(bool v) {

    UseLocalStackAllocationBlock = v;

  }

  /// Return true if the object was pre-allocated into the local block.

  bool isObjectPreAllocated(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].PreAllocated;

  }

  /// Return the size of the specified object.

  int64_t getObjectSize(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].Size;

  }

  /// Change the size of the specified stack object.

  void setObjectSize(int ObjectIdx, int64_t Size) {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    Objects[ObjectIdx+NumFixedObjects].Size = Size;

  }

  /// Return the alignment of the specified stack object.

  Align getObjectAlign(int ObjectIdx) const {

    assert(unsigned(ObjectIdx + NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx + NumFixedObjects].Alignment;

  }

  /// Should this stack ID be considered in MaxAlignment.

  bool contributesToMaxAlignment(uint8_t StackID) {

    return StackID == TargetStackID::Default ||

           StackID == TargetStackID::ScalableVector;

  }

  /// setObjectAlignment - Change the alignment of the specified stack object.

  void setObjectAlignment(int ObjectIdx, Align Alignment) {

    assert(unsigned(ObjectIdx + NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    Objects[ObjectIdx + NumFixedObjects].Alignment = Alignment;

    // Only ensure max alignment for the default and scalable vector stack.

    uint8_t StackID = getStackID(ObjectIdx);

    if (contributesToMaxAlignment(StackID))

      ensureMaxAlignment(Alignment);

  }

  /// Return the underlying Alloca of the specified

  /// stack object if it exists. Returns 0 if none exists.

  const AllocaInst* getObjectAllocation(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].Alloca;

  }

  /// Remove the underlying Alloca of the specified stack object if it

  /// exists. This generally should not be used and is for reduction tooling.

  void clearObjectAllocation(int ObjectIdx) {

    assert(unsigned(ObjectIdx + NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    Objects[ObjectIdx + NumFixedObjects].Alloca = nullptr;

  }

  /// Return the assigned stack offset of the specified object

  /// from the incoming stack pointer.

  int64_t getObjectOffset(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    assert(!isDeadObjectIndex(ObjectIdx) &&

           "Getting frame offset for a dead object?");

    return Objects[ObjectIdx+NumFixedObjects].SPOffset;

  }

  bool isObjectZExt(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].isZExt;

  }

  void setObjectZExt(int ObjectIdx, bool IsZExt) {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    Objects[ObjectIdx+NumFixedObjects].isZExt = IsZExt;

  }

  bool isObjectSExt(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].isSExt;

  }

  void setObjectSExt(int ObjectIdx, bool IsSExt) {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    Objects[ObjectIdx+NumFixedObjects].isSExt = IsSExt;

  }

  /// Set the stack frame offset of the specified object. The

  /// offset is relative to the stack pointer on entry to the function.

  void setObjectOffset(int ObjectIdx, int64_t SPOffset) {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    assert(!isDeadObjectIndex(ObjectIdx) &&

           "Setting frame offset for a dead object?");

    Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;

  }

  SSPLayoutKind getObjectSSPLayout(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return (SSPLayoutKind)Objects[ObjectIdx+NumFixedObjects].SSPLayout;

  }

  void setObjectSSPLayout(int ObjectIdx, SSPLayoutKind Kind) {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    assert(!isDeadObjectIndex(ObjectIdx) &&

           "Setting SSP layout for a dead object?");

    Objects[ObjectIdx+NumFixedObjects].SSPLayout = Kind;

  }

  /// Return the number of bytes that must be allocated to hold

  /// all of the fixed size frame objects.  This is only valid after

  /// Prolog/Epilog code insertion has finalized the stack frame layout.

  uint64_t getStackSize() const { return StackSize; }

  /// Set the size of the stack.

  void setStackSize(uint64_t Size) { StackSize = Size; }

  /// Estimate and return the size of the stack frame.

  uint64_t estimateStackSize(const MachineFunction &MF) const;

  /// Return the correction for frame offsets.

  int getOffsetAdjustment() const { return OffsetAdjustment; }

  /// Set the correction for frame offsets.

  void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }

  /// Return the alignment in bytes that this function must be aligned to,

  /// which is greater than the default stack alignment provided by the target.

  Align getMaxAlign() const { return MaxAlignment; }

  /// Make sure the function is at least Align bytes aligned.

  void ensureMaxAlignment(Align Alignment);

  /// Return true if this function adjusts the stack -- e.g.,

  /// when calling another function. This is only valid during and after

  /// prolog/epilog code insertion.

  bool adjustsStack() const { return AdjustsStack; }

  void setAdjustsStack(bool V) { AdjustsStack = V; }

  /// Return true if the current function has any function calls.

  bool hasCalls() const { return HasCalls; }

  void setHasCalls(bool V) { HasCalls = V; }

  /// Returns true if the function contains opaque dynamic stack adjustments.

  bool hasOpaqueSPAdjustment() const { return HasOpaqueSPAdjustment; }

  void setHasOpaqueSPAdjustment(bool B) { HasOpaqueSPAdjustment = B; }

  /// Returns true if the function contains operations which will lower down to

  /// instructions which manipulate the stack pointer.

  bool hasCopyImplyingStackAdjustment() const {

    return HasCopyImplyingStackAdjustment;

  }

  void setHasCopyImplyingStackAdjustment(bool B) {

    HasCopyImplyingStackAdjustment = B;

  }

  /// Returns true if the function calls the llvm.va_start intrinsic.

  bool hasVAStart() const { return HasVAStart; }

  void setHasVAStart(bool B) { HasVAStart = B; }

  /// Returns true if the function is variadic and contains a musttail call.

  bool hasMustTailInVarArgFunc() const { return HasMustTailInVarArgFunc; }

  void setHasMustTailInVarArgFunc(bool B) { HasMustTailInVarArgFunc = B; }

  /// Returns true if the function contains a tail call.

  bool hasTailCall() const { return HasTailCall; }

  void setHasTailCall(bool V = true) { HasTailCall = V; }

  /// Computes the maximum size of a callframe and the AdjustsStack property.

  /// This only works for targets defining

  /// TargetInstrInfo::getCallFrameSetupOpcode(), getCallFrameDestroyOpcode(),

  /// and getFrameSize().

  /// This is usually computed by the prologue epilogue inserter but some

  /// targets may call this to compute it earlier.

  void computeMaxCallFrameSize(const MachineFunction &MF);

  /// Return the maximum size of a call frame that must be

  /// allocated for an outgoing function call.  This is only available if

  /// CallFrameSetup/Destroy pseudo instructions are used by the target, and

  /// then only during or after prolog/epilog code insertion.

  ///

  unsigned getMaxCallFrameSize() const {

    // TODO: Enable this assert when targets are fixed.

    //assert(isMaxCallFrameSizeComputed() && "MaxCallFrameSize not computed yet");

    if (!isMaxCallFrameSizeComputed())

      return 0;

    return MaxCallFrameSize;

  }

  bool isMaxCallFrameSizeComputed() const {

    return MaxCallFrameSize != ~0u;

  }

  void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }

  /// Returns how many bytes of callee-saved registers the target pushed in the

  /// prologue. Only used for debug info.

  unsigned getCVBytesOfCalleeSavedRegisters() const {

    return CVBytesOfCalleeSavedRegisters;

  }

  void setCVBytesOfCalleeSavedRegisters(unsigned S) {

    CVBytesOfCalleeSavedRegisters = S;

  }

  /// Create a new object at a fixed location on the stack.

  /// All fixed objects should be created before other objects are created for

  /// efficiency. By default, fixed objects are not pointed to by LLVM IR

  /// values. This returns an index with a negative value.

  int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool IsImmutable,

                        bool isAliased = false);

  /// Create a spill slot at a fixed location on the stack.

  /// Returns an index with a negative value.

  int CreateFixedSpillStackObject(uint64_t Size, int64_t SPOffset,

                                  bool IsImmutable = false);

  /// Returns true if the specified index corresponds to a fixed stack object.

  bool isFixedObjectIndex(int ObjectIdx) const {

    return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);

  }

  /// Returns true if the specified index corresponds

  /// to an object that might be pointed to by an LLVM IR value.

  bool isAliasedObjectIndex(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].isAliased;

  }

  /// Returns true if the specified index corresponds to an immutable object.

  bool isImmutableObjectIndex(int ObjectIdx) const {

    // Tail calling functions can clobber their function arguments.

    if (HasTailCall)

      return false;

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].isImmutable;

  }

  /// Marks the immutability of an object.

  void setIsImmutableObjectIndex(int ObjectIdx, bool IsImmutable) {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    Objects[ObjectIdx+NumFixedObjects].isImmutable = IsImmutable;

  }

  /// Returns true if the specified index corresponds to a spill slot.

  bool isSpillSlotObjectIndex(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;

  }

  bool isStatepointSpillSlotObjectIndex(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].isStatepointSpillSlot;

  }

  /// \see StackID

  uint8_t getStackID(int ObjectIdx) const {

    return Objects[ObjectIdx+NumFixedObjects].StackID;

  }

  /// \see StackID

  void setStackID(int ObjectIdx, uint8_t ID) {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    Objects[ObjectIdx+NumFixedObjects].StackID = ID;

    // If ID > 0, MaxAlignment may now be overly conservative.

    // If ID == 0, MaxAlignment will need to be updated separately.

  }

  /// Returns true if the specified index corresponds to a dead object.

  bool isDeadObjectIndex(int ObjectIdx) const {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;

  }

  /// Returns true if the specified index corresponds to a variable sized

  /// object.

  bool isVariableSizedObjectIndex(int ObjectIdx) const {

    assert(unsigned(ObjectIdx + NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    return Objects[ObjectIdx + NumFixedObjects].Size == 0;

  }

  void markAsStatepointSpillSlotObjectIndex(int ObjectIdx) {

    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&

           "Invalid Object Idx!");

    Objects[ObjectIdx+NumFixedObjects].isStatepointSpillSlot = true;

    assert(isStatepointSpillSlotObjectIndex(ObjectIdx) && "inconsistent");

  }

  /// Create a new statically sized stack object, returning

  /// a nonnegative identifier to represent it.

  int CreateStackObject(uint64_t Size, Align Alignment, bool isSpillSlot,

                        const AllocaInst *Alloca = nullptr, uint8_t ID = 0);

  /// Create a new statically sized stack object that represents a spill slot,

  /// returning a nonnegative identifier to represent it.

  int CreateSpillStackObject(uint64_t Size, Align Alignment);

  /// Remove or mark dead a statically sized stack object.

  void RemoveStackObject(int ObjectIdx) {

    // Mark it dead.

    Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;

  }

  /// Notify the MachineFrameInfo object that a variable sized object has been

  /// created.  This must be created whenever a variable sized object is

  /// created, whether or not the index returned is actually used.

  int CreateVariableSizedObject(Align Alignment, const AllocaInst *Alloca);

  /// Returns a reference to call saved info vector for the current function.

  const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {

    return CSInfo;

  }

  /// \copydoc getCalleeSavedInfo()

  std::vector<CalleeSavedInfo> &getCalleeSavedInfo() { return CSInfo; }

  /// Used by prolog/epilog inserter to set the function's callee saved

  /// information.

  void setCalleeSavedInfo(std::vector<CalleeSavedInfo> CSI) {

    CSInfo = std::move(CSI);

  }

  /// Has the callee saved info been calculated yet?

  bool isCalleeSavedInfoValid() const { return CSIValid; }

  void setCalleeSavedInfoValid(bool v) { CSIValid = v; }

  MachineBasicBlock *getSavePoint() const { return Save; }

  void setSavePoint(MachineBasicBlock *NewSave) { Save = NewSave; }

  MachineBasicBlock *getRestorePoint() const { return Restore; }

  void setRestorePoint(MachineBasicBlock *NewRestore) { Restore = NewRestore; }

  uint64_t getUnsafeStackSize() const { return UnsafeStackSize; }

  void setUnsafeStackSize(uint64_t Size) { UnsafeStackSize = Size; }

  /// Return a set of physical registers that are pristine.

  ///

  /// Pristine registers hold a value that is useless to the current function,

  /// but that must be preserved - they are callee saved registers that are not

  /// saved.

  ///

  /// Before the PrologueEpilogueInserter has placed the CSR spill code, this

  /// method always returns an empty set.

  BitVector getPristineRegs(const MachineFunction &MF) const;

  /// Used by the MachineFunction printer to print information about

  /// stack objects. Implemented in MachineFunction.cpp.

  void print(const MachineFunction &MF, raw_ostream &OS) const;