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      1 //===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // The file defines the MachineFrameInfo class.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H
     15 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
     16 
     17 #include "llvm/ADT/SmallVector.h"
     18 #include "llvm/Support/DataTypes.h"
     19 #include <cassert>
     20 #include <vector>
     21 
     22 namespace llvm {
     23 class raw_ostream;
     24 class TargetData;
     25 class TargetRegisterClass;
     26 class Type;
     27 class MachineFunction;
     28 class MachineBasicBlock;
     29 class TargetFrameLowering;
     30 class BitVector;
     31 
     32 /// The CalleeSavedInfo class tracks the information need to locate where a
     33 /// callee saved register is in the current frame.
     34 class CalleeSavedInfo {
     35   unsigned Reg;
     36   int FrameIdx;
     37 
     38 public:
     39   explicit CalleeSavedInfo(unsigned R, int FI = 0)
     40   : Reg(R), FrameIdx(FI) {}
     41 
     42   // Accessors.
     43   unsigned getReg()                        const { return Reg; }
     44   int getFrameIdx()                        const { return FrameIdx; }
     45   void setFrameIdx(int FI)                       { FrameIdx = FI; }
     46 };
     47 
     48 /// The MachineFrameInfo class represents an abstract stack frame until
     49 /// prolog/epilog code is inserted.  This class is key to allowing stack frame
     50 /// representation optimizations, such as frame pointer elimination.  It also
     51 /// allows more mundane (but still important) optimizations, such as reordering
     52 /// of abstract objects on the stack frame.
     53 ///
     54 /// To support this, the class assigns unique integer identifiers to stack
     55 /// objects requested clients.  These identifiers are negative integers for
     56 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
     57 /// for objects that may be reordered.  Instructions which refer to stack
     58 /// objects use a special MO_FrameIndex operand to represent these frame
     59 /// indexes.
     60 ///
     61 /// Because this class keeps track of all references to the stack frame, it
     62 /// knows when a variable sized object is allocated on the stack.  This is the
     63 /// sole condition which prevents frame pointer elimination, which is an
     64 /// important optimization on register-poor architectures.  Because original
     65 /// variable sized alloca's in the source program are the only source of
     66 /// variable sized stack objects, it is safe to decide whether there will be
     67 /// any variable sized objects before all stack objects are known (for
     68 /// example, register allocator spill code never needs variable sized
     69 /// objects).
     70 ///
     71 /// When prolog/epilog code emission is performed, the final stack frame is
     72 /// built and the machine instructions are modified to refer to the actual
     73 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
     74 /// the program.
     75 ///
     76 /// @brief Abstract Stack Frame Information
     77 class MachineFrameInfo {
     78 
     79   // StackObject - Represent a single object allocated on the stack.
     80   struct StackObject {
     81     // SPOffset - The offset of this object from the stack pointer on entry to
     82     // the function.  This field has no meaning for a variable sized element.
     83     int64_t SPOffset;
     84 
     85     // The size of this object on the stack. 0 means a variable sized object,
     86     // ~0ULL means a dead object.
     87     uint64_t Size;
     88 
     89     // Alignment - The required alignment of this stack slot.
     90     unsigned Alignment;
     91 
     92     // isImmutable - If true, the value of the stack object is set before
     93     // entering the function and is not modified inside the function. By
     94     // default, fixed objects are immutable unless marked otherwise.
     95     bool isImmutable;
     96 
     97     // isSpillSlot - If true the stack object is used as spill slot. It
     98     // cannot alias any other memory objects.
     99     bool isSpillSlot;
    100 
    101     // MayNeedSP - If true the stack object triggered the creation of the stack
    102     // protector. We should allocate this object right after the stack
    103     // protector.
    104     bool MayNeedSP;
    105 
    106     // PreAllocated - If true, the object was mapped into the local frame
    107     // block and doesn't need additional handling for allocation beyond that.
    108     bool PreAllocated;
    109 
    110     StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
    111                 bool isSS, bool NSP)
    112       : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
    113         isSpillSlot(isSS), MayNeedSP(NSP), PreAllocated(false) {}
    114   };
    115 
    116   /// Objects - The list of stack objects allocated...
    117   ///
    118   std::vector<StackObject> Objects;
    119 
    120   /// NumFixedObjects - This contains the number of fixed objects contained on
    121   /// the stack.  Because fixed objects are stored at a negative index in the
    122   /// Objects list, this is also the index to the 0th object in the list.
    123   ///
    124   unsigned NumFixedObjects;
    125 
    126   /// HasVarSizedObjects - This boolean keeps track of whether any variable
    127   /// sized objects have been allocated yet.
    128   ///
    129   bool HasVarSizedObjects;
    130 
    131   /// FrameAddressTaken - This boolean keeps track of whether there is a call
    132   /// to builtin \@llvm.frameaddress.
    133   bool FrameAddressTaken;
    134 
    135   /// ReturnAddressTaken - This boolean keeps track of whether there is a call
    136   /// to builtin \@llvm.returnaddress.
    137   bool ReturnAddressTaken;
    138 
    139   /// StackSize - The prolog/epilog code inserter calculates the final stack
    140   /// offsets for all of the fixed size objects, updating the Objects list
    141   /// above.  It then updates StackSize to contain the number of bytes that need
    142   /// to be allocated on entry to the function.
    143   ///
    144   uint64_t StackSize;
    145 
    146   /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
    147   /// have the actual offset from the stack/frame pointer.  The exact usage of
    148   /// this is target-dependent, but it is typically used to adjust between
    149   /// SP-relative and FP-relative offsets.  E.G., if objects are accessed via
    150   /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
    151   /// to the distance between the initial SP and the value in FP.  For many
    152   /// targets, this value is only used when generating debug info (via
    153   /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
    154   /// corresponding adjustments are performed directly.
    155   int OffsetAdjustment;
    156 
    157   /// MaxAlignment - The prolog/epilog code inserter may process objects
    158   /// that require greater alignment than the default alignment the target
    159   /// provides. To handle this, MaxAlignment is set to the maximum alignment
    160   /// needed by the objects on the current frame.  If this is greater than the
    161   /// native alignment maintained by the compiler, dynamic alignment code will
    162   /// be needed.
    163   ///
    164   unsigned MaxAlignment;
    165 
    166   /// AdjustsStack - Set to true if this function adjusts the stack -- e.g.,
    167   /// when calling another function. This is only valid during and after
    168   /// prolog/epilog code insertion.
    169   bool AdjustsStack;
    170 
    171   /// HasCalls - Set to true if this function has any function calls.
    172   bool HasCalls;
    173 
    174   /// StackProtectorIdx - The frame index for the stack protector.
    175   int StackProtectorIdx;
    176 
    177   /// FunctionContextIdx - The frame index for the function context. Used for
    178   /// SjLj exceptions.
    179   int FunctionContextIdx;
    180 
    181   /// MaxCallFrameSize - This contains the size of the largest call frame if the
    182   /// target uses frame setup/destroy pseudo instructions (as defined in the
    183   /// TargetFrameInfo class).  This information is important for frame pointer
    184   /// elimination.  If is only valid during and after prolog/epilog code
    185   /// insertion.
    186   ///
    187   unsigned MaxCallFrameSize;
    188 
    189   /// CSInfo - The prolog/epilog code inserter fills in this vector with each
    190   /// callee saved register saved in the frame.  Beyond its use by the prolog/
    191   /// epilog code inserter, this data used for debug info and exception
    192   /// handling.
    193   std::vector<CalleeSavedInfo> CSInfo;
    194 
    195   /// CSIValid - Has CSInfo been set yet?
    196   bool CSIValid;
    197 
    198   /// TargetFrameLowering - Target information about frame layout.
    199   ///
    200   const TargetFrameLowering &TFI;
    201 
    202   /// LocalFrameObjects - References to frame indices which are mapped
    203   /// into the local frame allocation block. <FrameIdx, LocalOffset>
    204   SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
    205 
    206   /// LocalFrameSize - Size of the pre-allocated local frame block.
    207   int64_t LocalFrameSize;
    208 
    209   /// Required alignment of the local object blob, which is the strictest
    210   /// alignment of any object in it.
    211   unsigned LocalFrameMaxAlign;
    212 
    213   /// Whether the local object blob needs to be allocated together. If not,
    214   /// PEI should ignore the isPreAllocated flags on the stack objects and
    215   /// just allocate them normally.
    216   bool UseLocalStackAllocationBlock;
    217 
    218 public:
    219     explicit MachineFrameInfo(const TargetFrameLowering &tfi) : TFI(tfi) {
    220     StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
    221     HasVarSizedObjects = false;
    222     FrameAddressTaken = false;
    223     ReturnAddressTaken = false;
    224     AdjustsStack = false;
    225     HasCalls = false;
    226     StackProtectorIdx = -1;
    227     FunctionContextIdx = -1;
    228     MaxCallFrameSize = 0;
    229     CSIValid = false;
    230     LocalFrameSize = 0;
    231     LocalFrameMaxAlign = 0;
    232     UseLocalStackAllocationBlock = false;
    233   }
    234 
    235   /// hasStackObjects - Return true if there are any stack objects in this
    236   /// function.
    237   ///
    238   bool hasStackObjects() const { return !Objects.empty(); }
    239 
    240   /// hasVarSizedObjects - This method may be called any time after instruction
    241   /// selection is complete to determine if the stack frame for this function
    242   /// contains any variable sized objects.
    243   ///
    244   bool hasVarSizedObjects() const { return HasVarSizedObjects; }
    245 
    246   /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
    247   /// stack protector object.
    248   ///
    249   int getStackProtectorIndex() const { return StackProtectorIdx; }
    250   void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
    251 
    252   /// getFunctionContextIndex/setFunctionContextIndex - Return the index for the
    253   /// function context object. This object is used for SjLj exceptions.
    254   int getFunctionContextIndex() const { return FunctionContextIdx; }
    255   void setFunctionContextIndex(int I) { FunctionContextIdx = I; }
    256 
    257   /// isFrameAddressTaken - This method may be called any time after instruction
    258   /// selection is complete to determine if there is a call to
    259   /// \@llvm.frameaddress in this function.
    260   bool isFrameAddressTaken() const { return FrameAddressTaken; }
    261   void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
    262 
    263   /// isReturnAddressTaken - This method may be called any time after
    264   /// instruction selection is complete to determine if there is a call to
    265   /// \@llvm.returnaddress in this function.
    266   bool isReturnAddressTaken() const { return ReturnAddressTaken; }
    267   void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
    268 
    269   /// getObjectIndexBegin - Return the minimum frame object index.
    270   ///
    271   int getObjectIndexBegin() const { return -NumFixedObjects; }
    272 
    273   /// getObjectIndexEnd - Return one past the maximum frame object index.
    274   ///
    275   int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
    276 
    277   /// getNumFixedObjects - Return the number of fixed objects.
    278   unsigned getNumFixedObjects() const { return NumFixedObjects; }
    279 
    280   /// getNumObjects - Return the number of objects.
    281   ///
    282   unsigned getNumObjects() const { return Objects.size(); }
    283 
    284   /// mapLocalFrameObject - Map a frame index into the local object block
    285   void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
    286     LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
    287     Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
    288   }
    289 
    290   /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
    291   std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
    292     assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
    293             "Invalid local object reference!");
    294     return LocalFrameObjects[i];
    295   }
    296 
    297   /// getLocalFrameObjectCount - Return the number of objects allocated into
    298   /// the local object block.
    299   int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
    300 
    301   /// setLocalFrameSize - Set the size of the local object blob.
    302   void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }
    303 
    304   /// getLocalFrameSize - Get the size of the local object blob.
    305   int64_t getLocalFrameSize() const { return LocalFrameSize; }
    306 
    307   /// setLocalFrameMaxAlign - Required alignment of the local object blob,
    308   /// which is the strictest alignment of any object in it.
    309   void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; }
    310 
    311   /// getLocalFrameMaxAlign - Return the required alignment of the local
    312   /// object blob.
    313   unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
    314 
    315   /// getUseLocalStackAllocationBlock - Get whether the local allocation blob
    316   /// should be allocated together or let PEI allocate the locals in it
    317   /// directly.
    318   bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;}
    319 
    320   /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
    321   /// should be allocated together or let PEI allocate the locals in it
    322   /// directly.
    323   void setUseLocalStackAllocationBlock(bool v) {
    324     UseLocalStackAllocationBlock = v;
    325   }
    326 
    327   /// isObjectPreAllocated - Return true if the object was pre-allocated into
    328   /// the local block.
    329   bool isObjectPreAllocated(int ObjectIdx) const {
    330     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    331            "Invalid Object Idx!");
    332     return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
    333   }
    334 
    335   /// getObjectSize - Return the size of the specified object.
    336   ///
    337   int64_t getObjectSize(int ObjectIdx) const {
    338     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    339            "Invalid Object Idx!");
    340     return Objects[ObjectIdx+NumFixedObjects].Size;
    341   }
    342 
    343   /// setObjectSize - Change the size of the specified stack object.
    344   void setObjectSize(int ObjectIdx, int64_t Size) {
    345     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    346            "Invalid Object Idx!");
    347     Objects[ObjectIdx+NumFixedObjects].Size = Size;
    348   }
    349 
    350   /// getObjectAlignment - Return the alignment of the specified stack object.
    351   unsigned getObjectAlignment(int ObjectIdx) const {
    352     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    353            "Invalid Object Idx!");
    354     return Objects[ObjectIdx+NumFixedObjects].Alignment;
    355   }
    356 
    357   /// setObjectAlignment - Change the alignment of the specified stack object.
    358   void setObjectAlignment(int ObjectIdx, unsigned Align) {
    359     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    360            "Invalid Object Idx!");
    361     Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
    362     MaxAlignment = std::max(MaxAlignment, Align);
    363   }
    364 
    365   /// NeedsStackProtector - Returns true if the object may need stack
    366   /// protectors.
    367   bool MayNeedStackProtector(int ObjectIdx) const {
    368     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    369            "Invalid Object Idx!");
    370     return Objects[ObjectIdx+NumFixedObjects].MayNeedSP;
    371   }
    372 
    373   /// getObjectOffset - Return the assigned stack offset of the specified object
    374   /// from the incoming stack pointer.
    375   ///
    376   int64_t getObjectOffset(int ObjectIdx) const {
    377     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    378            "Invalid Object Idx!");
    379     assert(!isDeadObjectIndex(ObjectIdx) &&
    380            "Getting frame offset for a dead object?");
    381     return Objects[ObjectIdx+NumFixedObjects].SPOffset;
    382   }
    383 
    384   /// setObjectOffset - Set the stack frame offset of the specified object.  The
    385   /// offset is relative to the stack pointer on entry to the function.
    386   ///
    387   void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
    388     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    389            "Invalid Object Idx!");
    390     assert(!isDeadObjectIndex(ObjectIdx) &&
    391            "Setting frame offset for a dead object?");
    392     Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
    393   }
    394 
    395   /// getStackSize - Return the number of bytes that must be allocated to hold
    396   /// all of the fixed size frame objects.  This is only valid after
    397   /// Prolog/Epilog code insertion has finalized the stack frame layout.
    398   ///
    399   uint64_t getStackSize() const { return StackSize; }
    400 
    401   /// setStackSize - Set the size of the stack...
    402   ///
    403   void setStackSize(uint64_t Size) { StackSize = Size; }
    404 
    405   /// getOffsetAdjustment - Return the correction for frame offsets.
    406   ///
    407   int getOffsetAdjustment() const { return OffsetAdjustment; }
    408 
    409   /// setOffsetAdjustment - Set the correction for frame offsets.
    410   ///
    411   void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
    412 
    413   /// getMaxAlignment - Return the alignment in bytes that this function must be
    414   /// aligned to, which is greater than the default stack alignment provided by
    415   /// the target.
    416   ///
    417   unsigned getMaxAlignment() const { return MaxAlignment; }
    418 
    419   /// setMaxAlignment - Set the preferred alignment.
    420   ///
    421   void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
    422 
    423   /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
    424   /// when calling another function. This is only valid during and after
    425   /// prolog/epilog code insertion.
    426   bool adjustsStack() const { return AdjustsStack; }
    427   void setAdjustsStack(bool V) { AdjustsStack = V; }
    428 
    429   /// hasCalls - Return true if the current function has any function calls.
    430   bool hasCalls() const { return HasCalls; }
    431   void setHasCalls(bool V) { HasCalls = V; }
    432 
    433   /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
    434   /// allocated for an outgoing function call.  This is only available if
    435   /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
    436   /// then only during or after prolog/epilog code insertion.
    437   ///
    438   unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
    439   void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
    440 
    441   /// CreateFixedObject - Create a new object at a fixed location on the stack.
    442   /// All fixed objects should be created before other objects are created for
    443   /// efficiency. By default, fixed objects are immutable. This returns an
    444   /// index with a negative value.
    445   ///
    446   int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable);
    447 
    448 
    449   /// isFixedObjectIndex - Returns true if the specified index corresponds to a
    450   /// fixed stack object.
    451   bool isFixedObjectIndex(int ObjectIdx) const {
    452     return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
    453   }
    454 
    455   /// isImmutableObjectIndex - Returns true if the specified index corresponds
    456   /// to an immutable object.
    457   bool isImmutableObjectIndex(int ObjectIdx) const {
    458     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    459            "Invalid Object Idx!");
    460     return Objects[ObjectIdx+NumFixedObjects].isImmutable;
    461   }
    462 
    463   /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
    464   /// to a spill slot..
    465   bool isSpillSlotObjectIndex(int ObjectIdx) const {
    466     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    467            "Invalid Object Idx!");
    468     return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;
    469   }
    470 
    471   /// isDeadObjectIndex - Returns true if the specified index corresponds to
    472   /// a dead object.
    473   bool isDeadObjectIndex(int ObjectIdx) const {
    474     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
    475            "Invalid Object Idx!");
    476     return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
    477   }
    478 
    479   /// CreateStackObject - Create a new statically sized stack object, returning
    480   /// a nonnegative identifier to represent it.
    481   ///
    482   int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
    483                         bool MayNeedSP = false) {
    484     assert(Size != 0 && "Cannot allocate zero size stack objects!");
    485     Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP));
    486     int Index = (int)Objects.size() - NumFixedObjects - 1;
    487     assert(Index >= 0 && "Bad frame index!");
    488     MaxAlignment = std::max(MaxAlignment, Alignment);
    489     return Index;
    490   }
    491 
    492   /// CreateSpillStackObject - Create a new statically sized stack object that
    493   /// represents a spill slot, returning a nonnegative identifier to represent
    494   /// it.
    495   ///
    496   int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
    497     CreateStackObject(Size, Alignment, true, false);
    498     int Index = (int)Objects.size() - NumFixedObjects - 1;
    499     MaxAlignment = std::max(MaxAlignment, Alignment);
    500     return Index;
    501   }
    502 
    503   /// RemoveStackObject - Remove or mark dead a statically sized stack object.
    504   ///
    505   void RemoveStackObject(int ObjectIdx) {
    506     // Mark it dead.
    507     Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
    508   }
    509 
    510   /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
    511   /// variable sized object has been created.  This must be created whenever a
    512   /// variable sized object is created, whether or not the index returned is
    513   /// actually used.
    514   ///
    515   int CreateVariableSizedObject(unsigned Alignment) {
    516     HasVarSizedObjects = true;
    517     Objects.push_back(StackObject(0, Alignment, 0, false, false, true));
    518     MaxAlignment = std::max(MaxAlignment, Alignment);
    519     return (int)Objects.size()-NumFixedObjects-1;
    520   }
    521 
    522   /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
    523   /// current function.
    524   const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
    525     return CSInfo;
    526   }
    527 
    528   /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
    529   /// callee saved information.
    530   void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
    531     CSInfo = CSI;
    532   }
    533 
    534   /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
    535   bool isCalleeSavedInfoValid() const { return CSIValid; }
    536 
    537   void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
    538 
    539   /// getPristineRegs - Return a set of physical registers that are pristine on
    540   /// entry to the MBB.
    541   ///
    542   /// Pristine registers hold a value that is useless to the current function,
    543   /// but that must be preserved - they are callee saved registers that have not
    544   /// been saved yet.
    545   ///
    546   /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
    547   /// method always returns an empty set.
    548   BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
    549 
    550   /// print - Used by the MachineFunction printer to print information about
    551   /// stack objects. Implemented in MachineFunction.cpp
    552   ///
    553   void print(const MachineFunction &MF, raw_ostream &OS) const;
    554 
    555   /// dump - Print the function to stderr.
    556   void dump(const MachineFunction &MF) const;
    557 };
    558 
    559 } // End llvm namespace
    560 
    561 #endif
    562