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/ADT/IndexedMap.h"
19 #include "llvm/Support/DataTypes.h"
26 class TargetRegisterClass;
28 class MachineFunction;
29 class MachineBasicBlock;
30 class TargetFrameLowering;
33 /// The CalleeSavedInfo class tracks the information need to locate where a
34 /// callee saved register is in the current frame.
35 class CalleeSavedInfo {
40 explicit CalleeSavedInfo(unsigned R, int FI = 0)
41 : Reg(R), FrameIdx(FI) {}
44 unsigned getReg() const { return Reg; }
45 int getFrameIdx() const { return FrameIdx; }
46 void setFrameIdx(int FI) { FrameIdx = FI; }
49 /// The MachineFrameInfo class represents an abstract stack frame until
50 /// prolog/epilog code is inserted. This class is key to allowing stack frame
51 /// representation optimizations, such as frame pointer elimination. It also
52 /// allows more mundane (but still important) optimizations, such as reordering
53 /// of abstract objects on the stack frame.
55 /// To support this, the class assigns unique integer identifiers to stack
56 /// objects requested clients. These identifiers are negative integers for
57 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
58 /// for objects that may be reordered. Instructions which refer to stack
59 /// objects use a special MO_FrameIndex operand to represent these frame
62 /// Because this class keeps track of all references to the stack frame, it
63 /// knows when a variable sized object is allocated on the stack. This is the
64 /// sole condition which prevents frame pointer elimination, which is an
65 /// important optimization on register-poor architectures. Because original
66 /// variable sized alloca's in the source program are the only source of
67 /// variable sized stack objects, it is safe to decide whether there will be
68 /// any variable sized objects before all stack objects are known (for
69 /// example, register allocator spill code never needs variable sized
72 /// When prolog/epilog code emission is performed, the final stack frame is
73 /// built and the machine instructions are modified to refer to the actual
74 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
77 /// @brief Abstract Stack Frame Information
78 class MachineFrameInfo {
80 // StackObject - Represent a single object allocated on the stack.
82 // SPOffset - The offset of this object from the stack pointer on entry to
83 // the function. This field has no meaning for a variable sized element.
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 // isSpillSlot - If true the stack object is used as spill slot. It
99 // cannot alias any other memory objects.
102 // MayNeedSP - If true the stack object triggered the creation of the stack
103 // protector. We should allocate this object right after the stack
107 // PreAllocated - If true, the object was mapped into the local frame
108 // block and doesn't need additional handling for allocation beyond that.
111 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
113 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
114 isSpillSlot(isSS), MayNeedSP(NSP), PreAllocated(false) {}
117 /// Objects - The list of stack objects allocated...
119 std::vector<StackObject> Objects;
121 /// NumFixedObjects - This contains the number of fixed objects contained on
122 /// the stack. Because fixed objects are stored at a negative index in the
123 /// Objects list, this is also the index to the 0th object in the list.
125 unsigned NumFixedObjects;
127 /// HasVarSizedObjects - This boolean keeps track of whether any variable
128 /// sized objects have been allocated yet.
130 bool HasVarSizedObjects;
132 /// FrameAddressTaken - This boolean keeps track of whether there is a call
133 /// to builtin \@llvm.frameaddress.
134 bool FrameAddressTaken;
136 /// ReturnAddressTaken - This boolean keeps track of whether there is a call
137 /// to builtin \@llvm.returnaddress.
138 bool ReturnAddressTaken;
140 /// StackSize - The prolog/epilog code inserter calculates the final stack
141 /// offsets for all of the fixed size objects, updating the Objects list
142 /// above. It then updates StackSize to contain the number of bytes that need
143 /// to be allocated on entry to the function.
147 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
148 /// have the actual offset from the stack/frame pointer. The exact usage of
149 /// this is target-dependent, but it is typically used to adjust between
150 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
151 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
152 /// to the distance between the initial SP and the value in FP. For many
153 /// targets, this value is only used when generating debug info (via
154 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
155 /// corresponding adjustments are performed directly.
156 int OffsetAdjustment;
158 /// MaxAlignment - The prolog/epilog code inserter may process objects
159 /// that require greater alignment than the default alignment the target
160 /// provides. To handle this, MaxAlignment is set to the maximum alignment
161 /// needed by the objects on the current frame. If this is greater than the
162 /// native alignment maintained by the compiler, dynamic alignment code will
165 unsigned MaxAlignment;
167 /// AdjustsStack - Set to true if this function adjusts the stack -- e.g.,
168 /// when calling another function. This is only valid during and after
169 /// prolog/epilog code insertion.
172 /// HasCalls - Set to true if this function has any function calls.
175 /// StackProtectorIdx - The frame index for the stack protector.
176 int StackProtectorIdx;
178 /// MaxCallFrameSize - This contains the size of the largest call frame if the
179 /// target uses frame setup/destroy pseudo instructions (as defined in the
180 /// TargetFrameInfo class). This information is important for frame pointer
181 /// elimination. If is only valid during and after prolog/epilog code
184 unsigned MaxCallFrameSize;
186 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
187 /// callee saved register saved in the frame. Beyond its use by the prolog/
188 /// epilog code inserter, this data used for debug info and exception
190 std::vector<CalleeSavedInfo> CSInfo;
192 /// CSIValid - Has CSInfo been set yet?
195 /// TargetFrameLowering - Target information about frame layout.
197 const TargetFrameLowering &TFI;
199 /// LocalFrameObjects - References to frame indices which are mapped
200 /// into the local frame allocation block. <FrameIdx, LocalOffset>
201 SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
203 /// LocalFrameSize - Size of the pre-allocated local frame block.
204 int64_t LocalFrameSize;
206 /// Required alignment of the local object blob, which is the strictest
207 /// alignment of any object in it.
208 unsigned LocalFrameMaxAlign;
210 /// Whether the local object blob needs to be allocated together. If not,
211 /// PEI should ignore the isPreAllocated flags on the stack objects and
212 /// just allocate them normally.
213 bool UseLocalStackAllocationBlock;
216 explicit MachineFrameInfo(const TargetFrameLowering &tfi) : TFI(tfi) {
217 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
218 HasVarSizedObjects = false;
219 FrameAddressTaken = false;
220 ReturnAddressTaken = false;
221 AdjustsStack = false;
223 StackProtectorIdx = -1;
224 MaxCallFrameSize = 0;
227 LocalFrameMaxAlign = 0;
228 UseLocalStackAllocationBlock = false;
231 /// hasStackObjects - Return true if there are any stack objects in this
234 bool hasStackObjects() const { return !Objects.empty(); }
236 /// hasVarSizedObjects - This method may be called any time after instruction
237 /// selection is complete to determine if the stack frame for this function
238 /// contains any variable sized objects.
240 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
242 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
243 /// stack protector object.
245 int getStackProtectorIndex() const { return StackProtectorIdx; }
246 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
248 /// isFrameAddressTaken - This method may be called any time after instruction
249 /// selection is complete to determine if there is a call to
250 /// \@llvm.frameaddress in this function.
251 bool isFrameAddressTaken() const { return FrameAddressTaken; }
252 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
254 /// isReturnAddressTaken - This method may be called any time after
255 /// instruction selection is complete to determine if there is a call to
256 /// \@llvm.returnaddress in this function.
257 bool isReturnAddressTaken() const { return ReturnAddressTaken; }
258 void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
260 /// getObjectIndexBegin - Return the minimum frame object index.
262 int getObjectIndexBegin() const { return -NumFixedObjects; }
264 /// getObjectIndexEnd - Return one past the maximum frame object index.
266 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
268 /// getNumFixedObjects - Return the number of fixed objects.
269 unsigned getNumFixedObjects() const { return NumFixedObjects; }
271 /// getNumObjects - Return the number of objects.
273 unsigned getNumObjects() const { return Objects.size(); }
275 /// mapLocalFrameObject - Map a frame index into the local object block
276 void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
277 LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
278 Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
281 /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
282 std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
283 assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
284 "Invalid local object reference!");
285 return LocalFrameObjects[i];
288 /// getLocalFrameObjectCount - Return the number of objects allocated into
289 /// the local object block.
290 int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
292 /// setLocalFrameSize - Set the size of the local object blob.
293 void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }
295 /// getLocalFrameSize - Get the size of the local object blob.
296 int64_t getLocalFrameSize() const { return LocalFrameSize; }
298 /// setLocalFrameMaxAlign - Required alignment of the local object blob,
299 /// which is the strictest alignment of any object in it.
300 void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; }
302 /// getLocalFrameMaxAlign - Return the required alignment of the local
304 unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
306 /// getUseLocalStackAllocationBlock - Get whether the local allocation blob
307 /// should be allocated together or let PEI allocate the locals in it
309 bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;}
311 /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
312 /// should be allocated together or let PEI allocate the locals in it
314 void setUseLocalStackAllocationBlock(bool v) {
315 UseLocalStackAllocationBlock = v;
318 /// isObjectPreAllocated - Return true if the object was pre-allocated into
320 bool isObjectPreAllocated(int ObjectIdx) const {
321 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
322 "Invalid Object Idx!");
323 return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
326 /// getObjectSize - Return the size of the specified object.
328 int64_t getObjectSize(int ObjectIdx) const {
329 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
330 "Invalid Object Idx!");
331 return Objects[ObjectIdx+NumFixedObjects].Size;
334 /// setObjectSize - Change the size of the specified stack object.
335 void setObjectSize(int ObjectIdx, int64_t Size) {
336 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
337 "Invalid Object Idx!");
338 Objects[ObjectIdx+NumFixedObjects].Size = Size;
341 /// getObjectAlignment - Return the alignment of the specified stack object.
342 unsigned getObjectAlignment(int ObjectIdx) const {
343 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
344 "Invalid Object Idx!");
345 return Objects[ObjectIdx+NumFixedObjects].Alignment;
348 /// setObjectAlignment - Change the alignment of the specified stack object.
349 void setObjectAlignment(int ObjectIdx, unsigned Align) {
350 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
351 "Invalid Object Idx!");
352 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
353 MaxAlignment = std::max(MaxAlignment, Align);
356 /// NeedsStackProtector - Returns true if the object may need stack
358 bool MayNeedStackProtector(int ObjectIdx) const {
359 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
360 "Invalid Object Idx!");
361 return Objects[ObjectIdx+NumFixedObjects].MayNeedSP;
364 /// getObjectOffset - Return the assigned stack offset of the specified object
365 /// from the incoming stack pointer.
367 int64_t getObjectOffset(int ObjectIdx) const {
368 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
369 "Invalid Object Idx!");
370 assert(!isDeadObjectIndex(ObjectIdx) &&
371 "Getting frame offset for a dead object?");
372 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
375 /// setObjectOffset - Set the stack frame offset of the specified object. The
376 /// offset is relative to the stack pointer on entry to the function.
378 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
379 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
380 "Invalid Object Idx!");
381 assert(!isDeadObjectIndex(ObjectIdx) &&
382 "Setting frame offset for a dead object?");
383 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
386 /// getStackSize - Return the number of bytes that must be allocated to hold
387 /// all of the fixed size frame objects. This is only valid after
388 /// Prolog/Epilog code insertion has finalized the stack frame layout.
390 uint64_t getStackSize() const { return StackSize; }
392 /// setStackSize - Set the size of the stack...
394 void setStackSize(uint64_t Size) { StackSize = Size; }
396 /// getOffsetAdjustment - Return the correction for frame offsets.
398 int getOffsetAdjustment() const { return OffsetAdjustment; }
400 /// setOffsetAdjustment - Set the correction for frame offsets.
402 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
404 /// getMaxAlignment - Return the alignment in bytes that this function must be
405 /// aligned to, which is greater than the default stack alignment provided by
408 unsigned getMaxAlignment() const { return MaxAlignment; }
410 /// setMaxAlignment - Set the preferred alignment.
412 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
414 /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
415 /// when calling another function. This is only valid during and after
416 /// prolog/epilog code insertion.
417 bool adjustsStack() const { return AdjustsStack; }
418 void setAdjustsStack(bool V) { AdjustsStack = V; }
420 /// hasCalls - Return true if the current function has any function calls.
421 bool hasCalls() const { return HasCalls; }
422 void setHasCalls(bool V) { HasCalls = V; }
424 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
425 /// allocated for an outgoing function call. This is only available if
426 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
427 /// then only during or after prolog/epilog code insertion.
429 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
430 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
432 /// CreateFixedObject - Create a new object at a fixed location on the stack.
433 /// All fixed objects should be created before other objects are created for
434 /// efficiency. By default, fixed objects are immutable. This returns an
435 /// index with a negative value.
437 int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable);
440 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
441 /// fixed stack object.
442 bool isFixedObjectIndex(int ObjectIdx) const {
443 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
446 /// isImmutableObjectIndex - Returns true if the specified index corresponds
447 /// to an immutable object.
448 bool isImmutableObjectIndex(int ObjectIdx) const {
449 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
450 "Invalid Object Idx!");
451 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
454 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
455 /// to a spill slot..
456 bool isSpillSlotObjectIndex(int ObjectIdx) const {
457 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
458 "Invalid Object Idx!");
459 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;;
462 /// isDeadObjectIndex - Returns true if the specified index corresponds to
464 bool isDeadObjectIndex(int ObjectIdx) const {
465 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
466 "Invalid Object Idx!");
467 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
470 /// CreateStackObject - Create a new statically sized stack object, returning
471 /// a nonnegative identifier to represent it.
473 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
474 bool MayNeedSP = false) {
475 assert(Size != 0 && "Cannot allocate zero size stack objects!");
476 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP));
477 int Index = (int)Objects.size() - NumFixedObjects - 1;
478 assert(Index >= 0 && "Bad frame index!");
479 MaxAlignment = std::max(MaxAlignment, Alignment);
483 /// CreateSpillStackObject - Create a new statically sized stack object that
484 /// represents a spill slot, returning a nonnegative identifier to represent
487 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
488 CreateStackObject(Size, Alignment, true, false);
489 int Index = (int)Objects.size() - NumFixedObjects - 1;
490 MaxAlignment = std::max(MaxAlignment, Alignment);
494 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
496 void RemoveStackObject(int ObjectIdx) {
498 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
501 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
502 /// variable sized object has been created. This must be created whenever a
503 /// variable sized object is created, whether or not the index returned is
506 int CreateVariableSizedObject(unsigned Alignment) {
507 HasVarSizedObjects = true;
508 Objects.push_back(StackObject(0, Alignment, 0, false, false, true));
509 MaxAlignment = std::max(MaxAlignment, Alignment);
510 return (int)Objects.size()-NumFixedObjects-1;
513 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
514 /// current function.
515 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
519 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
520 /// callee saved information.
521 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
525 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
526 bool isCalleeSavedInfoValid() const { return CSIValid; }
528 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
530 /// getPristineRegs - Return a set of physical registers that are pristine on
531 /// entry to the MBB.
533 /// Pristine registers hold a value that is useless to the current function,
534 /// but that must be preserved - they are callee saved registers that have not
537 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
538 /// method always returns an empty set.
539 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
541 /// print - Used by the MachineFunction printer to print information about
542 /// stack objects. Implemented in MachineFunction.cpp
544 void print(const MachineFunction &MF, raw_ostream &OS) const;
546 /// dump - Print the function to stderr.
547 void dump(const MachineFunction &MF) const;
550 } // End llvm namespace