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/ADT/SmallVector.h"
18 #include "llvm/System/DataTypes.h"
25 class TargetRegisterClass;
27 class MachineFunction;
28 class MachineBasicBlock;
29 class TargetFrameInfo;
32 /// The CalleeSavedInfo class tracks the information need to locate where a
33 /// callee saved register in the current frame.
34 class CalleeSavedInfo {
36 const TargetRegisterClass *RegClass;
40 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
41 : Reg(R), RegClass(RC), FrameIdx(FI) {}
44 unsigned getReg() const { return Reg; }
45 const TargetRegisterClass *getRegClass() const { return RegClass; }
46 int getFrameIdx() const { return FrameIdx; }
47 void setFrameIdx(int FI) { FrameIdx = FI; }
50 /// The MachineFrameInfo class represents an abstract stack frame until
51 /// prolog/epilog code is inserted. This class is key to allowing stack frame
52 /// representation optimizations, such as frame pointer elimination. It also
53 /// allows more mundane (but still important) optimizations, such as reordering
54 /// of abstract objects on the stack frame.
56 /// To support this, the class assigns unique integer identifiers to stack
57 /// objects requested clients. These identifiers are negative integers for
58 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
59 /// for objects that may be reordered. Instructions which refer to stack
60 /// objects use a special MO_FrameIndex operand to represent these frame
63 /// Because this class keeps track of all references to the stack frame, it
64 /// knows when a variable sized object is allocated on the stack. This is the
65 /// sole condition which prevents frame pointer elimination, which is an
66 /// important optimization on register-poor architectures. Because original
67 /// variable sized alloca's in the source program are the only source of
68 /// variable sized stack objects, it is safe to decide whether there will be
69 /// any variable sized objects before all stack objects are known (for
70 /// example, register allocator spill code never needs variable sized
73 /// When prolog/epilog code emission is performed, the final stack frame is
74 /// built and the machine instructions are modified to refer to the actual
75 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
78 /// @brief Abstract Stack Frame Information
79 class MachineFrameInfo {
81 // StackObject - Represent a single object allocated on the stack.
83 // SPOffset - The offset of this object from the stack pointer on entry to
84 // the function. This field has no meaning for a variable sized element.
87 // The size of this object on the stack. 0 means a variable sized object,
88 // ~0ULL means a dead object.
91 // Alignment - The required alignment of this stack slot.
94 // isImmutable - If true, the value of the stack object is set before
95 // entering the function and is not modified inside the function. By
96 // default, fixed objects are immutable unless marked otherwise.
99 // isSpillSlot - If true, the stack object is used as spill slot. It
100 // cannot alias any other memory objects.
103 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
105 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
109 /// Objects - The list of stack objects allocated...
111 std::vector<StackObject> Objects;
113 /// NumFixedObjects - This contains the number of fixed objects contained on
114 /// the stack. Because fixed objects are stored at a negative index in the
115 /// Objects list, this is also the index to the 0th object in the list.
117 unsigned NumFixedObjects;
119 /// HasVarSizedObjects - This boolean keeps track of whether any variable
120 /// sized objects have been allocated yet.
122 bool HasVarSizedObjects;
124 /// FrameAddressTaken - This boolean keeps track of whether there is a call
125 /// to builtin \@llvm.frameaddress.
126 bool FrameAddressTaken;
128 /// StackSize - The prolog/epilog code inserter calculates the final stack
129 /// offsets for all of the fixed size objects, updating the Objects list
130 /// above. It then updates StackSize to contain the number of bytes that need
131 /// to be allocated on entry to the function.
135 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
136 /// have the actual offset from the stack/frame pointer. The exact usage of
137 /// this is target-dependent, but it is typically used to adjust between
138 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
139 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
140 /// to the distance between the initial SP and the value in FP. For many
141 /// targets, this value is only used when generating debug info (via
142 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
143 /// corresponding adjustments are performed directly.
144 int OffsetAdjustment;
146 /// MaxAlignment - The prolog/epilog code inserter may process objects
147 /// that require greater alignment than the default alignment the target
148 /// provides. To handle this, MaxAlignment is set to the maximum alignment
149 /// needed by the objects on the current frame. If this is greater than the
150 /// native alignment maintained by the compiler, dynamic alignment code will
153 unsigned MaxAlignment;
155 /// AdjustsStack - Set to true if this function adjusts the stack -- e.g.,
156 /// when calling another function. This is only valid during and after
157 /// prolog/epilog code insertion.
160 /// HasCalls - Set to true if this function has any function calls.
163 /// StackProtectorIdx - The frame index for the stack protector.
164 int StackProtectorIdx;
166 /// MaxCallFrameSize - This contains the size of the largest call frame if the
167 /// target uses frame setup/destroy pseudo instructions (as defined in the
168 /// TargetFrameInfo class). This information is important for frame pointer
169 /// elimination. If is only valid during and after prolog/epilog code
172 unsigned MaxCallFrameSize;
174 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
175 /// callee saved register saved in the frame. Beyond its use by the prolog/
176 /// epilog code inserter, this data used for debug info and exception
178 std::vector<CalleeSavedInfo> CSInfo;
180 /// CSIValid - Has CSInfo been set yet?
183 /// SpillObjects - A vector indicating which frame indices refer to
185 SmallVector<bool, 8> SpillObjects;
187 /// TargetFrameInfo - Target information about frame layout.
189 const TargetFrameInfo &TFI;
192 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
193 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
194 HasVarSizedObjects = false;
195 FrameAddressTaken = false;
196 AdjustsStack = false;
198 StackProtectorIdx = -1;
199 MaxCallFrameSize = 0;
203 /// hasStackObjects - Return true if there are any stack objects in this
206 bool hasStackObjects() const { return !Objects.empty(); }
208 /// hasVarSizedObjects - This method may be called any time after instruction
209 /// selection is complete to determine if the stack frame for this function
210 /// contains any variable sized objects.
212 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
214 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
215 /// stack protector object.
217 int getStackProtectorIndex() const { return StackProtectorIdx; }
218 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
220 /// isFrameAddressTaken - This method may be called any time after instruction
221 /// selection is complete to determine if there is a call to
222 /// \@llvm.frameaddress in this function.
223 bool isFrameAddressTaken() const { return FrameAddressTaken; }
224 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
226 /// getObjectIndexBegin - Return the minimum frame object index.
228 int getObjectIndexBegin() const { return -NumFixedObjects; }
230 /// getObjectIndexEnd - Return one past the maximum frame object index.
232 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
234 /// getNumFixedObjects() - Return the number of fixed objects.
235 unsigned getNumFixedObjects() const { return NumFixedObjects; }
237 /// getNumObjects() - Return the number of objects.
239 unsigned getNumObjects() const { return Objects.size(); }
241 /// getObjectSize - Return the size of the specified object.
243 int64_t getObjectSize(int ObjectIdx) const {
244 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
245 "Invalid Object Idx!");
246 return Objects[ObjectIdx+NumFixedObjects].Size;
249 /// setObjectSize - Change the size of the specified stack object.
250 void setObjectSize(int ObjectIdx, int64_t Size) {
251 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
252 "Invalid Object Idx!");
253 Objects[ObjectIdx+NumFixedObjects].Size = Size;
256 /// getObjectAlignment - Return the alignment of the specified stack object.
257 unsigned getObjectAlignment(int ObjectIdx) const {
258 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
259 "Invalid Object Idx!");
260 return Objects[ObjectIdx+NumFixedObjects].Alignment;
263 /// setObjectAlignment - Change the alignment of the specified stack object.
264 void setObjectAlignment(int ObjectIdx, unsigned Align) {
265 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
266 "Invalid Object Idx!");
267 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
268 MaxAlignment = std::max(MaxAlignment, Align);
271 /// getObjectOffset - Return the assigned stack offset of the specified object
272 /// from the incoming stack pointer.
274 int64_t getObjectOffset(int ObjectIdx) const {
275 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
276 "Invalid Object Idx!");
277 assert(!isDeadObjectIndex(ObjectIdx) &&
278 "Getting frame offset for a dead object?");
279 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
282 /// setObjectOffset - Set the stack frame offset of the specified object. The
283 /// offset is relative to the stack pointer on entry to the function.
285 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
286 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
287 "Invalid Object Idx!");
288 assert(!isDeadObjectIndex(ObjectIdx) &&
289 "Setting frame offset for a dead object?");
290 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
293 /// getStackSize - Return the number of bytes that must be allocated to hold
294 /// all of the fixed size frame objects. This is only valid after
295 /// Prolog/Epilog code insertion has finalized the stack frame layout.
297 uint64_t getStackSize() const { return StackSize; }
299 /// setStackSize - Set the size of the stack...
301 void setStackSize(uint64_t Size) { StackSize = Size; }
303 /// getOffsetAdjustment - Return the correction for frame offsets.
305 int getOffsetAdjustment() const { return OffsetAdjustment; }
307 /// setOffsetAdjustment - Set the correction for frame offsets.
309 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
311 /// getMaxAlignment - Return the alignment in bytes that this function must be
312 /// aligned to, which is greater than the default stack alignment provided by
315 unsigned getMaxAlignment() const { return MaxAlignment; }
317 /// setMaxAlignment - Set the preferred alignment.
319 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
321 /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
322 /// when calling another function. This is only valid during and after
323 /// prolog/epilog code insertion.
324 bool adjustsStack() const { return AdjustsStack; }
325 void setAdjustsStack(bool V) { AdjustsStack = V; }
327 /// hasCalls - Return true if the current function has any function calls.
328 bool hasCalls() const { return HasCalls; }
329 void setHasCalls(bool V) { HasCalls = V; }
331 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
332 /// allocated for an outgoing function call. This is only available if
333 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
334 /// then only during or after prolog/epilog code insertion.
336 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
337 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
339 /// CreateFixedObject - Create a new object at a fixed location on the stack.
340 /// All fixed objects should be created before other objects are created for
341 /// efficiency. By default, fixed objects are immutable. This returns an
342 /// index with a negative value.
344 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
345 bool Immutable, bool isSS);
348 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
349 /// fixed stack object.
350 bool isFixedObjectIndex(int ObjectIdx) const {
351 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
354 /// isImmutableObjectIndex - Returns true if the specified index corresponds
355 /// to an immutable object.
356 bool isImmutableObjectIndex(int ObjectIdx) const {
357 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
358 "Invalid Object Idx!");
359 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
362 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
363 /// to a spill slot..
364 bool isSpillSlotObjectIndex(int ObjectIdx) const {
365 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
366 "Invalid Object Idx!");
367 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;;
370 /// isDeadObjectIndex - Returns true if the specified index corresponds to
372 bool isDeadObjectIndex(int ObjectIdx) const {
373 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
374 "Invalid Object Idx!");
375 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
378 /// CreateStackObject - Create a new statically sized stack object,
379 /// returning a nonnegative identifier to represent it.
381 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS) {
382 assert(Size != 0 && "Cannot allocate zero size stack objects!");
383 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS));
384 int Index = (int)Objects.size()-NumFixedObjects-1;
385 assert(Index >= 0 && "Bad frame index!");
386 MaxAlignment = std::max(MaxAlignment, Alignment);
390 /// CreateSpillStackObject - Create a new statically sized stack
391 /// object that represents a spill slot, returning a nonnegative
392 /// identifier to represent it.
394 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
395 CreateStackObject(Size, Alignment, true);
396 int Index = (int)Objects.size()-NumFixedObjects-1;
397 MaxAlignment = std::max(MaxAlignment, Alignment);
401 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
403 void RemoveStackObject(int ObjectIdx) {
405 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
408 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
409 /// variable sized object has been created. This must be created whenever a
410 /// variable sized object is created, whether or not the index returned is
413 int CreateVariableSizedObject() {
414 HasVarSizedObjects = true;
415 Objects.push_back(StackObject(0, 1, 0, false, false));
416 return (int)Objects.size()-NumFixedObjects-1;
419 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
420 /// current function.
421 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
425 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
426 /// callee saved information.
427 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
431 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
432 bool isCalleeSavedInfoValid() const { return CSIValid; }
434 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
436 /// getPristineRegs - Return a set of physical registers that are pristine on
437 /// entry to the MBB.
439 /// Pristine registers hold a value that is useless to the current function,
440 /// but that must be preserved - they are callee saved registers that have not
443 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
444 /// method always returns an empty set.
445 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
447 /// print - Used by the MachineFunction printer to print information about
448 /// stack objects. Implemented in MachineFunction.cpp
450 void print(const MachineFunction &MF, raw_ostream &OS) const;
452 /// dump - Print the function to stderr.
453 void dump(const MachineFunction &MF) const;
456 } // End llvm namespace