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
17 #include "llvm/Support/DataTypes.h"
24 class TargetRegisterClass;
26 class MachineModuleInfo;
27 class MachineFunction;
28 class TargetFrameInfo;
30 /// The CalleeSavedInfo class tracks the information need to locate where a
31 /// callee saved register in the current frame.
32 class CalleeSavedInfo {
36 const TargetRegisterClass *RegClass;
40 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
47 unsigned getReg() const { return Reg; }
48 const TargetRegisterClass *getRegClass() const { return RegClass; }
49 int getFrameIdx() const { return FrameIdx; }
50 void setFrameIdx(int FI) { FrameIdx = FI; }
53 /// The MachineFrameInfo class represents an abstract stack frame until
54 /// prolog/epilog code is inserted. This class is key to allowing stack frame
55 /// representation optimizations, such as frame pointer elimination. It also
56 /// allows more mundane (but still important) optimizations, such as reordering
57 /// of abstract objects on the stack frame.
59 /// To support this, the class assigns unique integer identifiers to stack
60 /// objects requested clients. These identifiers are negative integers for
61 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
62 /// for objects that may be reordered. Instructions which refer to stack
63 /// objects use a special MO_FrameIndex operand to represent these frame
66 /// Because this class keeps track of all references to the stack frame, it
67 /// knows when a variable sized object is allocated on the stack. This is the
68 /// sole condition which prevents frame pointer elimination, which is an
69 /// important optimization on register-poor architectures. Because original
70 /// variable sized alloca's in the source program are the only source of
71 /// variable sized stack objects, it is safe to decide whether there will be
72 /// any variable sized objects before all stack objects are known (for
73 /// example, register allocator spill code never needs variable sized
76 /// When prolog/epilog code emission is performed, the final stack frame is
77 /// built and the machine instructions are modified to refer to the actual
78 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
81 /// @brief Abstract Stack Frame Information
82 class MachineFrameInfo {
84 // StackObject - Represent a single object allocated on the stack.
86 // The size of this object on the stack. 0 means a variable sized object,
87 // ~0ULL means a dead object.
90 // Alignment - The required alignment of this stack slot.
93 // isImmutable - If true, the value of the stack object is set before
94 // entering the function and is not modified inside the function. By
95 // default, fixed objects are immutable unless marked otherwise.
98 // SPOffset - The offset of this object from the stack pointer on entry to
99 // the function. This field has no meaning for a variable sized element.
102 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM = false)
103 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {}
106 /// Objects - The list of stack objects allocated...
108 std::vector<StackObject> Objects;
110 /// NumFixedObjects - This contains the number of fixed objects contained on
111 /// the stack. Because fixed objects are stored at a negative index in the
112 /// Objects list, this is also the index to the 0th object in the list.
114 unsigned NumFixedObjects;
116 /// HasVarSizedObjects - This boolean keeps track of whether any variable
117 /// sized objects have been allocated yet.
119 bool HasVarSizedObjects;
121 /// FrameAddressTaken - This boolean keeps track of whether there is a call
122 /// to builtin @llvm.frameaddress.
123 bool FrameAddressTaken;
125 /// StackSize - The prolog/epilog code inserter calculates the final stack
126 /// offsets for all of the fixed size objects, updating the Objects list
127 /// above. It then updates StackSize to contain the number of bytes that need
128 /// to be allocated on entry to the function.
132 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
133 /// have the actual offset from the stack/frame pointer. The calculation is
134 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
135 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
136 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
138 int OffsetAdjustment;
140 /// MaxAlignment - The prolog/epilog code inserter may process objects
141 /// that require greater alignment than the default alignment the target
142 /// provides. To handle this, MaxAlignment is set to the maximum alignment
143 /// needed by the objects on the current frame. If this is greater than the
144 /// native alignment maintained by the compiler, dynamic alignment code will
147 unsigned MaxAlignment;
149 /// HasCalls - Set to true if this function has any function calls. This is
150 /// only valid during and after prolog/epilog code insertion.
153 /// MaxCallFrameSize - This contains the size of the largest call frame if the
154 /// target uses frame setup/destroy pseudo instructions (as defined in the
155 /// TargetFrameInfo class). This information is important for frame pointer
156 /// elimination. If is only valid during and after prolog/epilog code
159 unsigned MaxCallFrameSize;
161 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
162 /// callee saved register saved in the frame. Beyond its use by the prolog/
163 /// epilog code inserter, this data used for debug info and exception
165 std::vector<CalleeSavedInfo> CSInfo;
167 /// MMI - This field is set (via setMachineModuleInfo) by a module info
168 /// consumer (ex. DwarfWriter) to indicate that frame layout information
169 /// should be acquired. Typically, it's the responsibility of the target's
170 /// TargetRegisterInfo prologue/epilogue emitting code to inform
171 /// MachineModuleInfo of frame layouts.
172 MachineModuleInfo *MMI;
174 /// TargetFrameInfo - Target information about frame layout.
176 const TargetFrameInfo &TFI;
178 MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
179 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
180 HasVarSizedObjects = false;
181 FrameAddressTaken = false;
183 MaxCallFrameSize = 0;
187 /// hasStackObjects - Return true if there are any stack objects in this
190 bool hasStackObjects() const { return !Objects.empty(); }
192 /// hasVarSizedObjects - This method may be called any time after instruction
193 /// selection is complete to determine if the stack frame for this function
194 /// contains any variable sized objects.
196 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
198 /// isFrameAddressTaken - This method may be called any time after instruction
199 /// selection is complete to determine if there is a call to
200 /// @llvm.frameaddress in this function.
201 bool isFrameAddressTaken() const { return FrameAddressTaken; }
202 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
204 /// getObjectIndexBegin - Return the minimum frame object index...
206 int getObjectIndexBegin() const { return -NumFixedObjects; }
208 /// getObjectIndexEnd - Return one past the maximum frame object index...
210 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
212 /// getNumFixedObjects() - Return the number of fixed objects.
213 unsigned getNumFixedObjects() const { return NumFixedObjects; }
215 /// getNumObjects() - Return the number of objects.
217 unsigned getNumObjects() const { return Objects.size(); }
219 /// getObjectSize - Return the size of the specified object
221 int64_t getObjectSize(int ObjectIdx) const {
222 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
223 "Invalid Object Idx!");
224 return Objects[ObjectIdx+NumFixedObjects].Size;
227 // setObjectSize - Change the size of the specified stack object...
228 void setObjectSize(int ObjectIdx, int64_t Size) {
229 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
230 "Invalid Object Idx!");
231 Objects[ObjectIdx+NumFixedObjects].Size = Size;
234 /// getObjectAlignment - Return the alignment of the specified stack object...
235 unsigned getObjectAlignment(int ObjectIdx) const {
236 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
237 "Invalid Object Idx!");
238 return Objects[ObjectIdx+NumFixedObjects].Alignment;
241 /// setObjectAlignment - Change the alignment of the specified stack object...
242 void setObjectAlignment(int ObjectIdx, unsigned Align) {
243 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
244 "Invalid Object Idx!");
245 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
248 /// getObjectOffset - Return the assigned stack offset of the specified object
249 /// from the incoming stack pointer.
251 int64_t getObjectOffset(int ObjectIdx) const {
252 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
253 "Invalid Object Idx!");
254 assert(!isDeadObjectIndex(ObjectIdx) &&
255 "Getting frame offset for a dead object?");
256 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
259 /// setObjectOffset - Set the stack frame offset of the specified object. The
260 /// offset is relative to the stack pointer on entry to the function.
262 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
263 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
264 "Invalid Object Idx!");
265 assert(!isDeadObjectIndex(ObjectIdx) &&
266 "Setting frame offset for a dead object?");
267 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
270 /// getStackSize - Return the number of bytes that must be allocated to hold
271 /// all of the fixed size frame objects. This is only valid after
272 /// Prolog/Epilog code insertion has finalized the stack frame layout.
274 uint64_t getStackSize() const { return StackSize; }
276 /// setStackSize - Set the size of the stack...
278 void setStackSize(uint64_t Size) { StackSize = Size; }
280 /// getOffsetAdjustment - Return the correction for frame offsets.
282 int getOffsetAdjustment() const { return OffsetAdjustment; }
284 /// setOffsetAdjustment - Set the correction for frame offsets.
286 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
288 /// getMaxAlignment - Return the alignment in bytes that this function must be
289 /// aligned to, which is greater than the default stack alignment provided by
292 unsigned getMaxAlignment() const { return MaxAlignment; }
294 /// setMaxAlignment - Set the preferred alignment.
296 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
298 /// hasCalls - Return true if the current function has no function calls.
299 /// This is only valid during or after prolog/epilog code emission.
301 bool hasCalls() const { return HasCalls; }
302 void setHasCalls(bool V) { HasCalls = V; }
304 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
305 /// allocated for an outgoing function call. This is only available if
306 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
307 /// then only during or after prolog/epilog code insertion.
309 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
310 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
312 /// CreateFixedObject - Create a new object at a fixed location on the stack.
313 /// All fixed objects should be created before other objects are created for
314 /// efficiency. By default, fixed objects are immutable. This returns an
315 /// index with a negative value.
317 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
318 bool Immutable = true);
321 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
322 /// fixed stack object.
323 bool isFixedObjectIndex(int ObjectIdx) const {
324 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
327 /// isImmutableObjectIndex - Returns true if the specified index corresponds
328 /// to an immutable object.
329 bool isImmutableObjectIndex(int ObjectIdx) const {
330 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
331 "Invalid Object Idx!");
332 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
335 /// isDeadObjectIndex - Returns true if the specified index corresponds to
337 bool isDeadObjectIndex(int ObjectIdx) const {
338 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
339 "Invalid Object Idx!");
340 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
343 /// CreateStackObject - Create a new statically sized stack object, returning
344 /// a nonnegative identifier to represent it.
346 int CreateStackObject(uint64_t Size, unsigned Alignment) {
347 assert(Size != 0 && "Cannot allocate zero size stack objects!");
348 Objects.push_back(StackObject(Size, Alignment, -1));
349 return (int)Objects.size()-NumFixedObjects-1;
352 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
354 void RemoveStackObject(int ObjectIdx) {
356 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
359 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
360 /// variable sized object has been created. This must be created whenever a
361 /// variable sized object is created, whether or not the index returned is
364 int CreateVariableSizedObject() {
365 HasVarSizedObjects = true;
366 Objects.push_back(StackObject(0, 1, -1));
367 return (int)Objects.size()-NumFixedObjects-1;
370 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
371 /// current function.
372 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
376 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
377 /// callee saved information.
378 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
382 /// getMachineModuleInfo - Used by a prologue/epilogue
383 /// emitter (TargetRegisterInfo) to provide frame layout information.
384 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
386 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
387 /// indicate that frame layout information should be gathered.
388 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
390 /// print - Used by the MachineFunction printer to print information about
391 /// stack objects. Implemented in MachineFunction.cpp
393 void print(const MachineFunction &MF, std::ostream &OS) const;
395 /// dump - Call print(MF, std::cerr) to be called from the debugger.
396 void dump(const MachineFunction &MF) const;
399 } // End llvm namespace