1 //===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H
12 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
18 class TargetRegisterClass;
20 class MachineDebugInfo;
21 class MachineFunction;
23 /// The CalleeSavedInfo class tracks the information need to locate where a
24 /// callee saved register in the current frame.
25 class CalleeSavedInfo {
29 const TargetRegisterClass *RegClass;
33 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
40 unsigned getReg() const { return Reg; }
41 const TargetRegisterClass *getRegClass() const { return RegClass; }
42 int getFrameIdx() const { return FrameIdx; }
43 void setFrameIdx(int FI) { FrameIdx = FI; }
46 /// The MachineFrameInfo class represents an abstract stack frame until
47 /// prolog/epilog code is inserted. This class is key to allowing stack frame
48 /// representation optimizations, such as frame pointer elimination. It also
49 /// allows more mundane (but still important) optimizations, such as reordering
50 /// of abstract objects on the stack frame.
52 /// To support this, the class assigns unique integer identifiers to stack
53 /// objects requested clients. These identifiers are negative integers for
54 /// fixed stack objects (such as arguments passed on the stack) or positive
55 /// for objects that may be reordered. Instructions which refer to stack
56 /// objects use a special MO_FrameIndex operand to represent these frame
59 /// Because this class keeps track of all references to the stack frame, it
60 /// knows when a variable sized object is allocated on the stack. This is the
61 /// sole condition which prevents frame pointer elimination, which is an
62 /// important optimization on register-poor architectures. Because original
63 /// variable sized alloca's in the source program are the only source of
64 /// variable sized stack objects, it is safe to decide whether there will be
65 /// any variable sized objects before all stack objects are known (for
66 /// example, register allocator spill code never needs variable sized
69 /// When prolog/epilog code emission is performed, the final stack frame is
70 /// built and the machine instructions are modified to refer to the actual
71 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
74 /// @brief Abstract Stack Frame Information
75 class MachineFrameInfo {
77 // StackObject - Represent a single object allocated on the stack.
79 // The size of this object on the stack. 0 means a variable sized object
82 // Alignment - The required alignment of this stack slot.
85 // SPOffset - The offset of this object from the stack pointer on entry to
86 // the function. This field has no meaning for a variable sized element.
89 StackObject(unsigned Sz, unsigned Al, int SP)
90 : Size(Sz), Alignment(Al), SPOffset(SP) {}
93 /// Objects - The list of stack objects allocated...
95 std::vector<StackObject> Objects;
97 /// NumFixedObjects - This contains the number of fixed objects contained on
98 /// the stack. Because fixed objects are stored at a negative index in the
99 /// Objects list, this is also the index to the 0th object in the list.
101 unsigned NumFixedObjects;
103 /// HasVarSizedObjects - This boolean keeps track of whether any variable
104 /// sized objects have been allocated yet.
106 bool HasVarSizedObjects;
108 /// StackSize - The prolog/epilog code inserter calculates the final stack
109 /// offsets for all of the fixed size objects, updating the Objects list
110 /// above. It then updates StackSize to contain the number of bytes that need
111 /// to be allocated on entry to the function.
115 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
116 /// have the actual offset from the stack/frame pointer. The calculation is
117 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
118 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
119 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
121 int OffsetAdjustment;
123 /// MaxAlignment - The prolog/epilog code inserter may process objects
124 /// that require greater alignment than the default alignment the target
125 /// provides. To handle this, MaxAlignment is set to the maximum alignment
126 /// needed by the objects on the current frame. If this is greater than the
127 /// native alignment maintained by the compiler, dynamic alignment code will
130 unsigned MaxAlignment;
132 /// HasCalls - Set to true if this function has any function calls. This is
133 /// only valid during and after prolog/epilog code insertion.
136 /// MaxCallFrameSize - This contains the size of the largest call frame if the
137 /// target uses frame setup/destroy pseudo instructions (as defined in the
138 /// TargetFrameInfo class). This information is important for frame pointer
139 /// elimination. If is only valid during and after prolog/epilog code
142 unsigned MaxCallFrameSize;
144 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
145 /// callee saved register saved in the frame. Beyond its use by the prolog/
146 /// epilog code inserter, this data used for debug info and exception
148 std::vector<CalleeSavedInfo> CSInfo;
150 /// DebugInfo - This field is set (via setMachineDebugInfo) by a debug info
151 /// consumer (ex. DwarfWriter) to indicate that frame layout information
152 /// should be acquired. Typically, it's the responsibility of the target's
153 /// MRegisterInfo prologue/epilogue emitting code to inform MachineDebugInfo
154 /// of frame layouts.
155 MachineDebugInfo *DebugInfo;
159 NumFixedObjects = StackSize = OffsetAdjustment = MaxAlignment = 0;
160 HasVarSizedObjects = false;
162 MaxCallFrameSize = 0;
166 /// hasStackObjects - Return true if there are any stack objects in this
169 bool hasStackObjects() const { return !Objects.empty(); }
171 /// hasVarSizedObjects - This method may be called any time after instruction
172 /// selection is complete to determine if the stack frame for this function
173 /// contains any variable sized objects.
175 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
177 /// getObjectIndexBegin - Return the minimum frame object index...
179 int getObjectIndexBegin() const { return -NumFixedObjects; }
181 /// getObjectIndexEnd - Return one past the maximum frame object index...
183 int getObjectIndexEnd() const { return Objects.size()-NumFixedObjects; }
185 /// getObjectSize - Return the size of the specified object
187 int getObjectSize(int ObjectIdx) const {
188 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
189 return Objects[ObjectIdx+NumFixedObjects].Size;
192 /// getObjectAlignment - Return the alignment of the specified stack object...
193 int getObjectAlignment(int ObjectIdx) const {
194 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
195 return Objects[ObjectIdx+NumFixedObjects].Alignment;
198 /// getObjectOffset - Return the assigned stack offset of the specified object
199 /// from the incoming stack pointer.
201 int getObjectOffset(int ObjectIdx) const {
202 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
203 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
206 /// setObjectOffset - Set the stack frame offset of the specified object. The
207 /// offset is relative to the stack pointer on entry to the function.
209 void setObjectOffset(int ObjectIdx, int SPOffset) {
210 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
211 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
214 /// getStackSize - Return the number of bytes that must be allocated to hold
215 /// all of the fixed size frame objects. This is only valid after
216 /// Prolog/Epilog code insertion has finalized the stack frame layout.
218 unsigned getStackSize() const { return StackSize; }
220 /// setStackSize - Set the size of the stack...
222 void setStackSize(unsigned Size) { StackSize = Size; }
224 /// getOffsetAdjustment - Return the correction for frame offsets.
226 int getOffsetAdjustment() const { return OffsetAdjustment; }
228 /// setOffsetAdjustment - Set the correction for frame offsets.
230 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
232 /// getMaxAlignment - Return the alignment in bytes that this function must be
233 /// aligned to, which is greater than the default stack alignment provided by
236 unsigned getMaxAlignment() const { return MaxAlignment; }
238 /// setMaxAlignment - Set the preferred alignment.
240 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
242 /// hasCalls - Return true if the current function has no function calls.
243 /// This is only valid during or after prolog/epilog code emission.
245 bool hasCalls() const { return HasCalls; }
246 void setHasCalls(bool V) { HasCalls = V; }
248 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
249 /// allocated for an outgoing function call. This is only available if
250 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
251 /// then only during or after prolog/epilog code insertion.
253 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
254 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
256 /// CreateFixedObject - Create a new object at a fixed location on the stack.
257 /// All fixed objects should be created before other objects are created for
258 /// efficiency. This returns an index with a negative value.
260 int CreateFixedObject(unsigned Size, int SPOffset) {
261 assert(Size != 0 && "Cannot allocate zero size fixed stack objects!");
262 Objects.insert(Objects.begin(), StackObject(Size, 1, SPOffset));
263 return -++NumFixedObjects;
266 /// CreateStackObject - Create a new statically sized stack object, returning
267 /// a postive identifier to represent it.
269 int CreateStackObject(unsigned Size, unsigned Alignment) {
270 // Keep track of the maximum alignment.
271 if (MaxAlignment < Alignment) MaxAlignment = Alignment;
273 assert(Size != 0 && "Cannot allocate zero size stack objects!");
274 Objects.push_back(StackObject(Size, Alignment, -1));
275 return Objects.size()-NumFixedObjects-1;
278 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
279 /// variable sized object has been created. This must be created whenever a
280 /// variable sized object is created, whether or not the index returned is
283 int CreateVariableSizedObject() {
284 HasVarSizedObjects = true;
285 if (MaxAlignment < 1) MaxAlignment = 1;
286 Objects.push_back(StackObject(0, 1, -1));
287 return Objects.size()-NumFixedObjects-1;
290 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
291 /// current function.
292 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
296 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
297 /// callee saved information.
298 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
302 /// getMachineDebugInfo - Used by a prologue/epilogue emitter (MRegisterInfo)
303 /// to provide frame layout information.
304 MachineDebugInfo *getMachineDebugInfo() const { return DebugInfo; }
306 /// setMachineDebugInfo - Used by a debug consumer (DwarfWriter) to indicate
307 /// that frame layout information should be gathered.
308 void setMachineDebugInfo(MachineDebugInfo *DI) { DebugInfo = DI; }
310 /// print - Used by the MachineFunction printer to print information about
311 /// stack objects. Implemented in MachineFunction.cpp
313 void print(const MachineFunction &MF, std::ostream &OS) const;
315 /// dump - Call print(MF, std::cerr) to be called from the debugger.
316 void dump(const MachineFunction &MF) const;
319 } // End llvm namespace