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 {
39 explicit CalleeSavedInfo(unsigned R, int FI = 0)
40 : Reg(R), FrameIdx(FI) {}
43 unsigned getReg() const { return Reg; }
44 int getFrameIdx() const { return FrameIdx; }
45 void setFrameIdx(int FI) { FrameIdx = FI; }
48 /// The MachineFrameInfo class represents an abstract stack frame until
49 /// prolog/epilog code is inserted. This class is key to allowing stack frame
50 /// representation optimizations, such as frame pointer elimination. It also
51 /// allows more mundane (but still important) optimizations, such as reordering
52 /// of abstract objects on the stack frame.
54 /// To support this, the class assigns unique integer identifiers to stack
55 /// objects requested clients. These identifiers are negative integers for
56 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
57 /// for objects that may be reordered. Instructions which refer to stack
58 /// objects use a special MO_FrameIndex operand to represent these frame
61 /// Because this class keeps track of all references to the stack frame, it
62 /// knows when a variable sized object is allocated on the stack. This is the
63 /// sole condition which prevents frame pointer elimination, which is an
64 /// important optimization on register-poor architectures. Because original
65 /// variable sized alloca's in the source program are the only source of
66 /// variable sized stack objects, it is safe to decide whether there will be
67 /// any variable sized objects before all stack objects are known (for
68 /// example, register allocator spill code never needs variable sized
71 /// When prolog/epilog code emission is performed, the final stack frame is
72 /// built and the machine instructions are modified to refer to the actual
73 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
76 /// @brief Abstract Stack Frame Information
77 class MachineFrameInfo {
79 // StackObject - Represent a single object allocated on the stack.
81 // SPOffset - The offset of this object from the stack pointer on entry to
82 // the function. This field has no meaning for a variable sized element.
85 // The size of this object on the stack. 0 means a variable sized object,
86 // ~0ULL means a dead object.
89 // Alignment - The required alignment of this stack slot.
92 // isImmutable - If true, the value of the stack object is set before
93 // entering the function and is not modified inside the function. By
94 // default, fixed objects are immutable unless marked otherwise.
97 // isSpillSlot - If true the stack object is used as spill slot. It
98 // cannot alias any other memory objects.
101 // MayNeedSP - If true the stack object triggered the creation of the stack
102 // protector. We should allocate this object right after the stack
106 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
108 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
109 isSpillSlot(isSS), MayNeedSP(NSP) {}
112 /// Objects - The list of stack objects allocated...
114 std::vector<StackObject> Objects;
116 /// NumFixedObjects - This contains the number of fixed objects contained on
117 /// the stack. Because fixed objects are stored at a negative index in the
118 /// Objects list, this is also the index to the 0th object in the list.
120 unsigned NumFixedObjects;
122 /// HasVarSizedObjects - This boolean keeps track of whether any variable
123 /// sized objects have been allocated yet.
125 bool HasVarSizedObjects;
127 /// FrameAddressTaken - This boolean keeps track of whether there is a call
128 /// to builtin \@llvm.frameaddress.
129 bool FrameAddressTaken;
131 /// ReturnAddressTaken - This boolean keeps track of whether there is a call
132 /// to builtin \@llvm.returnaddress.
133 bool ReturnAddressTaken;
135 /// StackSize - The prolog/epilog code inserter calculates the final stack
136 /// offsets for all of the fixed size objects, updating the Objects list
137 /// above. It then updates StackSize to contain the number of bytes that need
138 /// to be allocated on entry to the function.
142 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
143 /// have the actual offset from the stack/frame pointer. The exact usage of
144 /// this is target-dependent, but it is typically used to adjust between
145 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
146 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
147 /// to the distance between the initial SP and the value in FP. For many
148 /// targets, this value is only used when generating debug info (via
149 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
150 /// corresponding adjustments are performed directly.
151 int OffsetAdjustment;
153 /// MaxAlignment - The prolog/epilog code inserter may process objects
154 /// that require greater alignment than the default alignment the target
155 /// provides. To handle this, MaxAlignment is set to the maximum alignment
156 /// needed by the objects on the current frame. If this is greater than the
157 /// native alignment maintained by the compiler, dynamic alignment code will
160 unsigned MaxAlignment;
162 /// AdjustsStack - Set to true if this function adjusts the stack -- e.g.,
163 /// when calling another function. This is only valid during and after
164 /// prolog/epilog code insertion.
167 /// HasCalls - Set to true if this function has any function calls.
170 /// StackProtectorIdx - The frame index for the stack protector.
171 int StackProtectorIdx;
173 /// MaxCallFrameSize - This contains the size of the largest call frame if the
174 /// target uses frame setup/destroy pseudo instructions (as defined in the
175 /// TargetFrameInfo class). This information is important for frame pointer
176 /// elimination. If is only valid during and after prolog/epilog code
179 unsigned MaxCallFrameSize;
181 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
182 /// callee saved register saved in the frame. Beyond its use by the prolog/
183 /// epilog code inserter, this data used for debug info and exception
185 std::vector<CalleeSavedInfo> CSInfo;
187 /// CSIValid - Has CSInfo been set yet?
190 /// SpillObjects - A vector indicating which frame indices refer to
192 SmallVector<bool, 8> SpillObjects;
194 /// TargetFrameInfo - Target information about frame layout.
196 const TargetFrameInfo &TFI;
199 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
200 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
201 HasVarSizedObjects = false;
202 FrameAddressTaken = false;
203 ReturnAddressTaken = false;
204 AdjustsStack = false;
206 StackProtectorIdx = -1;
207 MaxCallFrameSize = 0;
211 /// hasStackObjects - Return true if there are any stack objects in this
214 bool hasStackObjects() const { return !Objects.empty(); }
216 /// hasVarSizedObjects - This method may be called any time after instruction
217 /// selection is complete to determine if the stack frame for this function
218 /// contains any variable sized objects.
220 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
222 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
223 /// stack protector object.
225 int getStackProtectorIndex() const { return StackProtectorIdx; }
226 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
228 /// isFrameAddressTaken - This method may be called any time after instruction
229 /// selection is complete to determine if there is a call to
230 /// \@llvm.frameaddress in this function.
231 bool isFrameAddressTaken() const { return FrameAddressTaken; }
232 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
234 /// isReturnAddressTaken - This method may be called any time after
235 /// instruction selection is complete to determine if there is a call to
236 /// \@llvm.returnaddress in this function.
237 bool isReturnAddressTaken() const { return ReturnAddressTaken; }
238 void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
240 /// getObjectIndexBegin - Return the minimum frame object index.
242 int getObjectIndexBegin() const { return -NumFixedObjects; }
244 /// getObjectIndexEnd - Return one past the maximum frame object index.
246 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
248 /// getNumFixedObjects() - Return the number of fixed objects.
249 unsigned getNumFixedObjects() const { return NumFixedObjects; }
251 /// getNumObjects() - Return the number of objects.
253 unsigned getNumObjects() const { return Objects.size(); }
255 /// getObjectSize - Return the size of the specified object.
257 int64_t getObjectSize(int ObjectIdx) const {
258 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
259 "Invalid Object Idx!");
260 return Objects[ObjectIdx+NumFixedObjects].Size;
263 /// setObjectSize - Change the size of the specified stack object.
264 void setObjectSize(int ObjectIdx, int64_t Size) {
265 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
266 "Invalid Object Idx!");
267 Objects[ObjectIdx+NumFixedObjects].Size = Size;
270 /// getObjectAlignment - Return the alignment of the specified stack object.
271 unsigned getObjectAlignment(int ObjectIdx) const {
272 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
273 "Invalid Object Idx!");
274 return Objects[ObjectIdx+NumFixedObjects].Alignment;
277 /// setObjectAlignment - Change the alignment of the specified stack object.
278 void setObjectAlignment(int ObjectIdx, unsigned Align) {
279 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
280 "Invalid Object Idx!");
281 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
282 MaxAlignment = std::max(MaxAlignment, Align);
285 /// NeedsStackProtector - Returns true if the object may need stack
287 bool MayNeedStackProtector(int ObjectIdx) const {
288 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
289 "Invalid Object Idx!");
290 return Objects[ObjectIdx+NumFixedObjects].MayNeedSP;
293 /// getObjectOffset - Return the assigned stack offset of the specified object
294 /// from the incoming stack pointer.
296 int64_t getObjectOffset(int ObjectIdx) const {
297 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
298 "Invalid Object Idx!");
299 assert(!isDeadObjectIndex(ObjectIdx) &&
300 "Getting frame offset for a dead object?");
301 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
304 /// setObjectOffset - Set the stack frame offset of the specified object. The
305 /// offset is relative to the stack pointer on entry to the function.
307 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
308 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
309 "Invalid Object Idx!");
310 assert(!isDeadObjectIndex(ObjectIdx) &&
311 "Setting frame offset for a dead object?");
312 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
315 /// getStackSize - Return the number of bytes that must be allocated to hold
316 /// all of the fixed size frame objects. This is only valid after
317 /// Prolog/Epilog code insertion has finalized the stack frame layout.
319 uint64_t getStackSize() const { return StackSize; }
321 /// setStackSize - Set the size of the stack...
323 void setStackSize(uint64_t Size) { StackSize = Size; }
325 /// getOffsetAdjustment - Return the correction for frame offsets.
327 int getOffsetAdjustment() const { return OffsetAdjustment; }
329 /// setOffsetAdjustment - Set the correction for frame offsets.
331 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
333 /// getMaxAlignment - Return the alignment in bytes that this function must be
334 /// aligned to, which is greater than the default stack alignment provided by
337 unsigned getMaxAlignment() const { return MaxAlignment; }
339 /// setMaxAlignment - Set the preferred alignment.
341 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
343 /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
344 /// when calling another function. This is only valid during and after
345 /// prolog/epilog code insertion.
346 bool adjustsStack() const { return AdjustsStack; }
347 void setAdjustsStack(bool V) { AdjustsStack = V; }
349 /// hasCalls - Return true if the current function has any function calls.
350 bool hasCalls() const { return HasCalls; }
351 void setHasCalls(bool V) { HasCalls = V; }
353 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
354 /// allocated for an outgoing function call. This is only available if
355 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
356 /// then only during or after prolog/epilog code insertion.
358 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
359 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
361 /// CreateFixedObject - Create a new object at a fixed location on the stack.
362 /// All fixed objects should be created before other objects are created for
363 /// efficiency. By default, fixed objects are immutable. This returns an
364 /// index with a negative value.
366 int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable);
369 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
370 /// fixed stack object.
371 bool isFixedObjectIndex(int ObjectIdx) const {
372 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
375 /// isImmutableObjectIndex - Returns true if the specified index corresponds
376 /// to an immutable object.
377 bool isImmutableObjectIndex(int ObjectIdx) const {
378 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
379 "Invalid Object Idx!");
380 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
383 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
384 /// to a spill slot..
385 bool isSpillSlotObjectIndex(int ObjectIdx) const {
386 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
387 "Invalid Object Idx!");
388 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;;
391 /// isDeadObjectIndex - Returns true if the specified index corresponds to
393 bool isDeadObjectIndex(int ObjectIdx) const {
394 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
395 "Invalid Object Idx!");
396 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
399 /// CreateStackObject - Create a new statically sized stack object, returning
400 /// a nonnegative identifier to represent it.
402 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
403 bool MayNeedSP = false) {
404 assert(Size != 0 && "Cannot allocate zero size stack objects!");
405 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP));
406 int Index = (int)Objects.size() - NumFixedObjects - 1;
407 assert(Index >= 0 && "Bad frame index!");
408 MaxAlignment = std::max(MaxAlignment, Alignment);
412 /// CreateSpillStackObject - Create a new statically sized stack object that
413 /// represents a spill slot, returning a nonnegative identifier to represent
416 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
417 CreateStackObject(Size, Alignment, true, false);
418 int Index = (int)Objects.size() - NumFixedObjects - 1;
419 MaxAlignment = std::max(MaxAlignment, Alignment);
423 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
425 void RemoveStackObject(int ObjectIdx) {
427 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
430 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
431 /// variable sized object has been created. This must be created whenever a
432 /// variable sized object is created, whether or not the index returned is
435 int CreateVariableSizedObject(unsigned Alignment) {
436 HasVarSizedObjects = true;
437 Objects.push_back(StackObject(0, Alignment, 0, false, false, true));
438 MaxAlignment = std::max(MaxAlignment, Alignment);
439 return (int)Objects.size()-NumFixedObjects-1;
442 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
443 /// current function.
444 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
448 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
449 /// callee saved information.
450 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
454 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
455 bool isCalleeSavedInfoValid() const { return CSIValid; }
457 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
459 /// getPristineRegs - Return a set of physical registers that are pristine on
460 /// entry to the MBB.
462 /// Pristine registers hold a value that is useless to the current function,
463 /// but that must be preserved - they are callee saved registers that have not
466 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
467 /// method always returns an empty set.
468 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
470 /// print - Used by the MachineFunction printer to print information about
471 /// stack objects. Implemented in MachineFunction.cpp
473 void print(const MachineFunction &MF, raw_ostream &OS) const;
475 /// dump - Print the function to stderr.
476 void dump(const MachineFunction &MF) const;
479 } // End llvm namespace