| //===-- 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. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H |
| #define LLVM_CODEGEN_MACHINEFRAMEINFO_H |
| |
| #include <vector> |
| |
| namespace llvm { |
| class TargetData; |
| class TargetRegisterClass; |
| class Type; |
| class MachineFunction; |
| |
| 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 |
| unsigned 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. |
| int SPOffset; |
| |
| StackObject(unsigned Sz, unsigned Al, int 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. |
| /// |
| unsigned StackSize; |
| |
| /// 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; |
| public: |
| MachineFrameInfo() { |
| NumFixedObjects = StackSize = 0; |
| HasVarSizedObjects = false; |
| HasCalls = false; |
| MaxCallFrameSize = 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 |
| /// |
| int 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. |
| /// |
| int 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, int 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. |
| /// |
| unsigned getStackSize() const { return StackSize; } |
| |
| /// setStackSize - Set the size of the stack... |
| /// |
| void setStackSize(unsigned Size) { StackSize = Size; } |
| |
| /// 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(unsigned Size, int SPOffset) { |
| assert(Size != 0 && "Cannot allocate zero size fixed stack objects!"); |
| Objects.insert(Objects.begin(), StackObject(Size, 1, SPOffset)); |
| return -++NumFixedObjects; |
| } |
| |
| /// CreateStackObject - Create a new statically sized stack object, returning |
| /// a postive identifier to represent it. |
| /// |
| int CreateStackObject(unsigned Size, unsigned Alignment) { |
| assert(Size != 0 && "Cannot allocate zero size stack objects!"); |
| Objects.push_back(StackObject(Size, Alignment, -1)); |
| return Objects.size()-NumFixedObjects-1; |
| } |
| |
| /// CreateStackObject - Create a stack object for a value of the specified |
| /// LLVM type. |
| /// |
| int CreateStackObject(const Type *Ty, const TargetData &TD); |
| |
| /// 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; |
| Objects.push_back(StackObject(0, 1, -1)); |
| return Objects.size()-NumFixedObjects-1; |
| } |
| |
| /// 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 |