1 //===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // The file defines the MachineFrameInfo class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H
15 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
22 class TargetRegisterClass;
24 class MachineModuleInfo;
25 class MachineFunction;
26 class TargetFrameInfo;
28 /// The CalleeSavedInfo class tracks the information need to locate where a
29 /// callee saved register in the current frame.
30 class CalleeSavedInfo {
34 const TargetRegisterClass *RegClass;
38 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
45 unsigned getReg() const { return Reg; }
46 const TargetRegisterClass *getRegClass() const { return RegClass; }
47 int getFrameIdx() const { return FrameIdx; }
48 void setFrameIdx(int FI) { FrameIdx = FI; }
51 /// The MachineFrameInfo class represents an abstract stack frame until
52 /// prolog/epilog code is inserted. This class is key to allowing stack frame
53 /// representation optimizations, such as frame pointer elimination. It also
54 /// allows more mundane (but still important) optimizations, such as reordering
55 /// of abstract objects on the stack frame.
57 /// To support this, the class assigns unique integer identifiers to stack
58 /// objects requested clients. These identifiers are negative integers for
59 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
60 /// for objects that may be reordered. Instructions which refer to stack
61 /// objects use a special MO_FrameIndex operand to represent these frame
64 /// Because this class keeps track of all references to the stack frame, it
65 /// knows when a variable sized object is allocated on the stack. This is the
66 /// sole condition which prevents frame pointer elimination, which is an
67 /// important optimization on register-poor architectures. Because original
68 /// variable sized alloca's in the source program are the only source of
69 /// variable sized stack objects, it is safe to decide whether there will be
70 /// any variable sized objects before all stack objects are known (for
71 /// example, register allocator spill code never needs variable sized
74 /// When prolog/epilog code emission is performed, the final stack frame is
75 /// built and the machine instructions are modified to refer to the actual
76 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
79 /// @brief Abstract Stack Frame Information
80 class MachineFrameInfo {
82 // StackObject - Represent a single object allocated on the stack.
84 // The size of this object on the stack. 0 means a variable sized object,
85 // ~0ULL means a dead object.
88 // Alignment - The required alignment of this stack slot.
91 // isImmutable - If true, the value of the stack object is set before
92 // entering the function and is not modified inside the function. By
93 // default, fixed objects are immutable unless marked otherwise.
96 // SPOffset - The offset of this object from the stack pointer on entry to
97 // the function. This field has no meaning for a variable sized element.
100 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM = false)
101 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {}
104 /// Objects - The list of stack objects allocated...
106 std::vector<StackObject> Objects;
108 /// NumFixedObjects - This contains the number of fixed objects contained on
109 /// the stack. Because fixed objects are stored at a negative index in the
110 /// Objects list, this is also the index to the 0th object in the list.
112 unsigned NumFixedObjects;
114 /// HasVarSizedObjects - This boolean keeps track of whether any variable
115 /// sized objects have been allocated yet.
117 bool HasVarSizedObjects;
119 /// StackSize - The prolog/epilog code inserter calculates the final stack
120 /// offsets for all of the fixed size objects, updating the Objects list
121 /// above. It then updates StackSize to contain the number of bytes that need
122 /// to be allocated on entry to the function.
126 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
127 /// have the actual offset from the stack/frame pointer. The calculation is
128 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
129 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
130 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
132 int OffsetAdjustment;
134 /// MaxAlignment - The prolog/epilog code inserter may process objects
135 /// that require greater alignment than the default alignment the target
136 /// provides. To handle this, MaxAlignment is set to the maximum alignment
137 /// needed by the objects on the current frame. If this is greater than the
138 /// native alignment maintained by the compiler, dynamic alignment code will
141 unsigned MaxAlignment;
143 /// HasCalls - Set to true if this function has any function calls. This is
144 /// only valid during and after prolog/epilog code insertion.
147 /// MaxCallFrameSize - This contains the size of the largest call frame if the
148 /// target uses frame setup/destroy pseudo instructions (as defined in the
149 /// TargetFrameInfo class). This information is important for frame pointer
150 /// elimination. If is only valid during and after prolog/epilog code
153 unsigned MaxCallFrameSize;
155 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
156 /// callee saved register saved in the frame. Beyond its use by the prolog/
157 /// epilog code inserter, this data used for debug info and exception
159 std::vector<CalleeSavedInfo> CSInfo;
161 /// MMI - This field is set (via setMachineModuleInfo) by a module info
162 /// consumer (ex. DwarfWriter) to indicate that frame layout information
163 /// should be acquired. Typically, it's the responsibility of the target's
164 /// TargetRegisterInfo prologue/epilogue emitting code to inform
165 /// MachineModuleInfo of frame layouts.
166 MachineModuleInfo *MMI;
168 /// TargetFrameInfo - Target information about frame layout.
170 const TargetFrameInfo &TFI;
172 MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
173 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
174 HasVarSizedObjects = false;
176 MaxCallFrameSize = 0;
180 /// hasStackObjects - Return true if there are any stack objects in this
183 bool hasStackObjects() const { return !Objects.empty(); }
185 /// hasVarSizedObjects - This method may be called any time after instruction
186 /// selection is complete to determine if the stack frame for this function
187 /// contains any variable sized objects.
189 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
191 /// getObjectIndexBegin - Return the minimum frame object index...
193 int getObjectIndexBegin() const { return -NumFixedObjects; }
195 /// getObjectIndexEnd - Return one past the maximum frame object index...
197 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
199 /// getNumFixedObjects() - Return the number of fixed objects.
200 unsigned getNumFixedObjects() const { return NumFixedObjects; }
202 /// getNumObjects() - Return the number of objects.
204 unsigned getNumObjects() const { return Objects.size(); }
206 /// getObjectSize - Return the size of the specified object
208 int64_t getObjectSize(int ObjectIdx) const {
209 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
210 "Invalid Object Idx!");
211 return Objects[ObjectIdx+NumFixedObjects].Size;
214 // setObjectSize - Change the size of the specified stack object...
215 void setObjectSize(int ObjectIdx, int64_t Size) {
216 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
217 "Invalid Object Idx!");
218 Objects[ObjectIdx+NumFixedObjects].Size = Size;
221 /// getObjectAlignment - Return the alignment of the specified stack object...
222 unsigned getObjectAlignment(int ObjectIdx) const {
223 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
224 "Invalid Object Idx!");
225 return Objects[ObjectIdx+NumFixedObjects].Alignment;
228 /// setObjectAlignment - Change the alignment of the specified stack object...
229 void setObjectAlignment(int ObjectIdx, unsigned Align) {
230 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
231 "Invalid Object Idx!");
232 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
235 /// getObjectOffset - Return the assigned stack offset of the specified object
236 /// from the incoming stack pointer.
238 int64_t getObjectOffset(int ObjectIdx) const {
239 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
240 "Invalid Object Idx!");
241 assert(!isDeadObjectIndex(ObjectIdx) &&
242 "Getting frame offset for a dead object?");
243 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
246 /// setObjectOffset - Set the stack frame offset of the specified object. The
247 /// offset is relative to the stack pointer on entry to the function.
249 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
250 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
251 "Invalid Object Idx!");
252 assert(!isDeadObjectIndex(ObjectIdx) &&
253 "Setting frame offset for a dead object?");
254 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
257 /// getStackSize - Return the number of bytes that must be allocated to hold
258 /// all of the fixed size frame objects. This is only valid after
259 /// Prolog/Epilog code insertion has finalized the stack frame layout.
261 uint64_t getStackSize() const { return StackSize; }
263 /// setStackSize - Set the size of the stack...
265 void setStackSize(uint64_t Size) { StackSize = Size; }
267 /// getOffsetAdjustment - Return the correction for frame offsets.
269 int getOffsetAdjustment() const { return OffsetAdjustment; }
271 /// setOffsetAdjustment - Set the correction for frame offsets.
273 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
275 /// getMaxAlignment - Return the alignment in bytes that this function must be
276 /// aligned to, which is greater than the default stack alignment provided by
279 unsigned getMaxAlignment() const { return MaxAlignment; }
281 /// setMaxAlignment - Set the preferred alignment.
283 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
285 /// hasCalls - Return true if the current function has no function calls.
286 /// This is only valid during or after prolog/epilog code emission.
288 bool hasCalls() const { return HasCalls; }
289 void setHasCalls(bool V) { HasCalls = V; }
291 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
292 /// allocated for an outgoing function call. This is only available if
293 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
294 /// then only during or after prolog/epilog code insertion.
296 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
297 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
299 /// CreateFixedObject - Create a new object at a fixed location on the stack.
300 /// All fixed objects should be created before other objects are created for
301 /// efficiency. By default, fixed objects are immutable. This returns an
302 /// index with a negative value.
304 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
305 bool Immutable = true);
308 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
309 /// fixed stack object.
310 bool isFixedObjectIndex(int ObjectIdx) const {
311 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
314 /// isImmutableObjectIndex - Returns true if the specified index corresponds
315 /// to an immutable object.
316 bool isImmutableObjectIndex(int ObjectIdx) const {
317 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
318 "Invalid Object Idx!");
319 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
322 /// isDeadObjectIndex - Returns true if the specified index corresponds to
324 bool isDeadObjectIndex(int ObjectIdx) const {
325 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
326 "Invalid Object Idx!");
327 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
330 /// CreateStackObject - Create a new statically sized stack object, returning
331 /// a nonnegative identifier to represent it.
333 int CreateStackObject(uint64_t Size, unsigned Alignment) {
334 assert(Size != 0 && "Cannot allocate zero size stack objects!");
335 Objects.push_back(StackObject(Size, Alignment, -1));
336 return (int)Objects.size()-NumFixedObjects-1;
339 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
341 void RemoveStackObject(int ObjectIdx) {
343 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
346 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
347 /// variable sized object has been created. This must be created whenever a
348 /// variable sized object is created, whether or not the index returned is
351 int CreateVariableSizedObject() {
352 HasVarSizedObjects = true;
353 Objects.push_back(StackObject(0, 1, -1));
354 return (int)Objects.size()-NumFixedObjects-1;
357 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
358 /// current function.
359 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
363 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
364 /// callee saved information.
365 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
369 /// getMachineModuleInfo - Used by a prologue/epilogue
370 /// emitter (TargetRegisterInfo) to provide frame layout information.
371 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
373 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
374 /// indicate that frame layout information should be gathered.
375 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
377 /// print - Used by the MachineFunction printer to print information about
378 /// stack objects. Implemented in MachineFunction.cpp
380 void print(const MachineFunction &MF, std::ostream &OS) const;
382 /// dump - Call print(MF, std::cerr) to be called from the debugger.
383 void dump(const MachineFunction &MF) const;
386 } // End llvm namespace