| //===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| |
| #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H |
| #define LLVM_CODEGEN_MACHINEFRAMEINFO_H |
| |
| #include <vector> |
| |
| namespace llvm { |
| class TargetData; |
| class TargetRegisterClass; |
| class Type; |
| class MachineModuleInfo; |
| class MachineFunction; |
| |
| /// The CalleeSavedInfo class tracks the information need to locate where a |
| /// callee saved register in the current frame. |
| class CalleeSavedInfo { |
| |
| private: |
| unsigned Reg; |
| const TargetRegisterClass *RegClass; |
| int FrameIdx; |
| |
| public: |
| CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0) |
| : Reg(R) |
| , RegClass(RC) |
| , FrameIdx(FI) |
| {} |
| |
| // Accessors. |
| unsigned getReg() const { return Reg; } |
| const TargetRegisterClass *getRegClass() const { return RegClass; } |
| int getFrameIdx() const { return FrameIdx; } |
| void setFrameIdx(int FI) { FrameIdx = FI; } |
| }; |
| |
| /// 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 positive |
| /// 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. |
| /// |
| /// @brief Abstract Stack Frame Information |
| class MachineFrameInfo { |
| |
| // StackObject - Represent a single object allocated on the stack. |
| struct StackObject { |
| // The size of this object on the stack. 0 means a variable sized object |
| uint64_t Size; |
| |
| // Alignment - The required alignment of this stack slot. |
| unsigned Alignment; |
| |
| // SPOffset - 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; |
| |
| StackObject(uint64_t Sz, unsigned Al, int64_t SP) |
| : Size(Sz), Alignment(Al), SPOffset(SP) {} |
| }; |
| |
| /// Objects - The list of stack objects allocated... |
| /// |
| std::vector<StackObject> Objects; |
| |
| /// NumFixedObjects - 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; |
| |
| /// HasVarSizedObjects - This boolean keeps track of whether any variable |
| /// sized objects have been allocated yet. |
| /// |
| bool HasVarSizedObjects; |
| |
| /// StackSize - 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; |
| |
| /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to |
| /// have the actual offset from the stack/frame pointer. The calculation is |
| /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() + |
| /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are |
| /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward |
| /// TOS. |
| int OffsetAdjustment; |
| |
| /// MaxAlignment - 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. |
| /// |
| unsigned MaxAlignment; |
| |
| /// HasCalls - Set to true if this function has any function calls. This is |
| /// only valid during and after prolog/epilog code insertion. |
| bool HasCalls; |
| |
| /// MaxCallFrameSize - 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. If is only valid during and after prolog/epilog code |
| /// insertion. |
| /// |
| unsigned MaxCallFrameSize; |
| |
| /// CSInfo - The prolog/epilog code inserter fills in this vector with each |
| /// callee saved register saved in the frame. Beyond its use by the prolog/ |
| /// epilog code inserter, this data used for debug info and exception |
| /// handling. |
| std::vector<CalleeSavedInfo> CSInfo; |
| |
| /// MMI - This field is set (via setMachineModuleInfo) by a module info |
| /// consumer (ex. DwarfWriter) to indicate that frame layout information |
| /// should be acquired. Typically, it's the responsibility of the target's |
| /// MRegisterInfo prologue/epilogue emitting code to inform MachineModuleInfo |
| /// of frame layouts. |
| MachineModuleInfo *MMI; |
| |
| public: |
| MachineFrameInfo() { |
| StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0; |
| HasVarSizedObjects = false; |
| HasCalls = false; |
| MaxCallFrameSize = 0; |
| MMI = 0; |
| } |
| |
| /// hasStackObjects - Return true if there are any stack objects in this |
| /// function. |
| /// |
| bool hasStackObjects() const { return !Objects.empty(); } |
| |
| /// hasVarSizedObjects - 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; } |
| |
| /// getObjectIndexBegin - Return the minimum frame object index... |
| /// |
| int getObjectIndexBegin() const { return -NumFixedObjects; } |
| |
| /// getObjectIndexEnd - Return one past the maximum frame object index... |
| /// |
| int getObjectIndexEnd() const { return Objects.size()-NumFixedObjects; } |
| |
| /// getObjectSize - Return the size of the specified object |
| /// |
| int64_t getObjectSize(int ObjectIdx) const { |
| assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!"); |
| return Objects[ObjectIdx+NumFixedObjects].Size; |
| } |
| |
| /// getObjectAlignment - Return the alignment of the specified stack object... |
| int getObjectAlignment(int ObjectIdx) const { |
| assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!"); |
| return Objects[ObjectIdx+NumFixedObjects].Alignment; |
| } |
| |
| /// getObjectOffset - Return the assigned stack offset of the specified object |
| /// from the incoming stack pointer. |
| /// |
| int64_t getObjectOffset(int ObjectIdx) const { |
| assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!"); |
| return Objects[ObjectIdx+NumFixedObjects].SPOffset; |
| } |
| |
| /// setObjectOffset - 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(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!"); |
| Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset; |
| } |
| |
| /// getStackSize - 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; } |
| |
| /// setStackSize - Set the size of the stack... |
| /// |
| void setStackSize(uint64_t Size) { StackSize = Size; } |
| |
| /// getOffsetAdjustment - Return the correction for frame offsets. |
| /// |
| int getOffsetAdjustment() const { return OffsetAdjustment; } |
| |
| /// setOffsetAdjustment - Set the correction for frame offsets. |
| /// |
| void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; } |
| |
| /// getMaxAlignment - Return the alignment in bytes that this function must be |
| /// aligned to, which is greater than the default stack alignment provided by |
| /// the target. |
| /// |
| unsigned getMaxAlignment() const { return MaxAlignment; } |
| |
| /// setMaxAlignment - Set the preferred alignment. |
| /// |
| void setMaxAlignment(unsigned Align) { MaxAlignment = Align; } |
| |
| /// hasCalls - Return true if the current function has no function calls. |
| /// This is only valid during or after prolog/epilog code emission. |
| /// |
| bool hasCalls() const { return HasCalls; } |
| void setHasCalls(bool V) { HasCalls = V; } |
| |
| /// getMaxCallFrameSize - 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 { return MaxCallFrameSize; } |
| void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; } |
| |
| /// CreateFixedObject - Create a new object at a fixed location on the stack. |
| /// All fixed objects should be created before other objects are created for |
| /// efficiency. This returns an index with a negative value. |
| /// |
| int CreateFixedObject(uint64_t Size, int64_t SPOffset) { |
| assert(Size != 0 && "Cannot allocate zero size fixed stack objects!"); |
| Objects.insert(Objects.begin(), StackObject(Size, 1, SPOffset)); |
| return -++NumFixedObjects; |
| } |
| |
| /// isFixedObjectIndex - Returns true if the specified index corresponds to a |
| /// fixed stack object. |
| bool isFixedObjectIndex(int ObjectIdx) const { |
| return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects); |
| } |
| |
| /// CreateStackObject - Create a new statically sized stack object, returning |
| /// a postive identifier to represent it. |
| /// |
| int CreateStackObject(uint64_t Size, unsigned Alignment) { |
| // Keep track of the maximum alignment. |
| if (MaxAlignment < Alignment) MaxAlignment = Alignment; |
| |
| assert(Size != 0 && "Cannot allocate zero size stack objects!"); |
| Objects.push_back(StackObject(Size, Alignment, -1)); |
| return Objects.size()-NumFixedObjects-1; |
| } |
| |
| /// CreateVariableSizedObject - 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() { |
| HasVarSizedObjects = true; |
| if (MaxAlignment < 1) MaxAlignment = 1; |
| Objects.push_back(StackObject(0, 1, -1)); |
| return Objects.size()-NumFixedObjects-1; |
| } |
| |
| /// getCalleeSavedInfo - Returns a reference to call saved info vector for the |
| /// current function. |
| const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const { |
| return CSInfo; |
| } |
| |
| /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's |
| /// callee saved information. |
| void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) { |
| CSInfo = CSI; |
| } |
| |
| /// getMachineModuleInfo - Used by a prologue/epilogue emitter (MRegisterInfo) |
| /// to provide frame layout information. |
| MachineModuleInfo *getMachineModuleInfo() const { return MMI; } |
| |
| /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to |
| /// indicate that frame layout information should be gathered. |
| void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; } |
| |
| /// print - Used by the MachineFunction printer to print information about |
| /// stack objects. Implemented in MachineFunction.cpp |
| /// |
| void print(const MachineFunction &MF, std::ostream &OS) const; |
| |
| /// dump - Call print(MF, std::cerr) to be called from the debugger. |
| void dump(const MachineFunction &MF) const; |
| }; |
| |
| } // End llvm namespace |
| |
| #endif |