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/Support/DataTypes.h"
25 class TargetRegisterClass;
27 class MachineFunction;
28 class MachineBasicBlock;
29 class TargetFrameLowering;
34 /// The CalleeSavedInfo class tracks the information need to locate where a
35 /// callee saved register is in the current frame.
36 class CalleeSavedInfo {
41 explicit CalleeSavedInfo(unsigned R, int FI = 0)
42 : Reg(R), FrameIdx(FI) {}
45 unsigned getReg() const { return Reg; }
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 // MayNeedSP - If true the stack object triggered the creation of the stack
104 // protector. We should allocate this object right after the stack
108 /// Alloca - If this stack object is originated from an Alloca instruction
109 /// this value saves the original IR allocation. Can be NULL.
110 const AllocaInst *Alloca;
112 // PreAllocated - If true, the object was mapped into the local frame
113 // block and doesn't need additional handling for allocation beyond that.
116 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
117 bool isSS, bool NSP, const AllocaInst *Val)
118 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
119 isSpillSlot(isSS), MayNeedSP(NSP), Alloca(Val), PreAllocated(false) {}
122 /// Objects - The list of stack objects allocated...
124 std::vector<StackObject> Objects;
126 /// NumFixedObjects - This contains the number of fixed objects contained on
127 /// the stack. Because fixed objects are stored at a negative index in the
128 /// Objects list, this is also the index to the 0th object in the list.
130 unsigned NumFixedObjects;
132 /// HasVarSizedObjects - This boolean keeps track of whether any variable
133 /// sized objects have been allocated yet.
135 bool HasVarSizedObjects;
137 /// FrameAddressTaken - This boolean keeps track of whether there is a call
138 /// to builtin \@llvm.frameaddress.
139 bool FrameAddressTaken;
141 /// ReturnAddressTaken - This boolean keeps track of whether there is a call
142 /// to builtin \@llvm.returnaddress.
143 bool ReturnAddressTaken;
145 /// StackSize - The prolog/epilog code inserter calculates the final stack
146 /// offsets for all of the fixed size objects, updating the Objects list
147 /// above. It then updates StackSize to contain the number of bytes that need
148 /// to be allocated on entry to the function.
152 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
153 /// have the actual offset from the stack/frame pointer. The exact usage of
154 /// this is target-dependent, but it is typically used to adjust between
155 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
156 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
157 /// to the distance between the initial SP and the value in FP. For many
158 /// targets, this value is only used when generating debug info (via
159 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
160 /// corresponding adjustments are performed directly.
161 int OffsetAdjustment;
163 /// MaxAlignment - The prolog/epilog code inserter may process objects
164 /// that require greater alignment than the default alignment the target
165 /// provides. To handle this, MaxAlignment is set to the maximum alignment
166 /// needed by the objects on the current frame. If this is greater than the
167 /// native alignment maintained by the compiler, dynamic alignment code will
170 unsigned MaxAlignment;
172 /// AdjustsStack - Set to true if this function adjusts the stack -- e.g.,
173 /// when calling another function. This is only valid during and after
174 /// prolog/epilog code insertion.
177 /// HasCalls - Set to true if this function has any function calls.
180 /// StackProtectorIdx - The frame index for the stack protector.
181 int StackProtectorIdx;
183 /// FunctionContextIdx - The frame index for the function context. Used for
185 int FunctionContextIdx;
187 /// MaxCallFrameSize - This contains the size of the largest call frame if the
188 /// target uses frame setup/destroy pseudo instructions (as defined in the
189 /// TargetFrameInfo class). This information is important for frame pointer
190 /// elimination. If is only valid during and after prolog/epilog code
193 unsigned MaxCallFrameSize;
195 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
196 /// callee saved register saved in the frame. Beyond its use by the prolog/
197 /// epilog code inserter, this data used for debug info and exception
199 std::vector<CalleeSavedInfo> CSInfo;
201 /// CSIValid - Has CSInfo been set yet?
204 /// TargetFrameLowering - Target information about frame layout.
206 const TargetFrameLowering &TFI;
208 /// LocalFrameObjects - References to frame indices which are mapped
209 /// into the local frame allocation block. <FrameIdx, LocalOffset>
210 SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
212 /// LocalFrameSize - Size of the pre-allocated local frame block.
213 int64_t LocalFrameSize;
215 /// Required alignment of the local object blob, which is the strictest
216 /// alignment of any object in it.
217 unsigned LocalFrameMaxAlign;
219 /// Whether the local object blob needs to be allocated together. If not,
220 /// PEI should ignore the isPreAllocated flags on the stack objects and
221 /// just allocate them normally.
222 bool UseLocalStackAllocationBlock;
225 explicit MachineFrameInfo(const TargetFrameLowering &tfi) : TFI(tfi) {
226 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
227 HasVarSizedObjects = false;
228 FrameAddressTaken = false;
229 ReturnAddressTaken = false;
230 AdjustsStack = false;
232 StackProtectorIdx = -1;
233 FunctionContextIdx = -1;
234 MaxCallFrameSize = 0;
237 LocalFrameMaxAlign = 0;
238 UseLocalStackAllocationBlock = false;
241 /// hasStackObjects - Return true if there are any stack objects in this
244 bool hasStackObjects() const { return !Objects.empty(); }
246 /// hasVarSizedObjects - This method may be called any time after instruction
247 /// selection is complete to determine if the stack frame for this function
248 /// contains any variable sized objects.
250 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
252 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
253 /// stack protector object.
255 int getStackProtectorIndex() const { return StackProtectorIdx; }
256 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
258 /// getFunctionContextIndex/setFunctionContextIndex - Return the index for the
259 /// function context object. This object is used for SjLj exceptions.
260 int getFunctionContextIndex() const { return FunctionContextIdx; }
261 void setFunctionContextIndex(int I) { FunctionContextIdx = I; }
263 /// isFrameAddressTaken - This method may be called any time after instruction
264 /// selection is complete to determine if there is a call to
265 /// \@llvm.frameaddress in this function.
266 bool isFrameAddressTaken() const { return FrameAddressTaken; }
267 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
269 /// isReturnAddressTaken - This method may be called any time after
270 /// instruction selection is complete to determine if there is a call to
271 /// \@llvm.returnaddress in this function.
272 bool isReturnAddressTaken() const { return ReturnAddressTaken; }
273 void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
275 /// getObjectIndexBegin - Return the minimum frame object index.
277 int getObjectIndexBegin() const { return -NumFixedObjects; }
279 /// getObjectIndexEnd - Return one past the maximum frame object index.
281 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
283 /// getNumFixedObjects - Return the number of fixed objects.
284 unsigned getNumFixedObjects() const { return NumFixedObjects; }
286 /// getNumObjects - Return the number of objects.
288 unsigned getNumObjects() const { return Objects.size(); }
290 /// mapLocalFrameObject - Map a frame index into the local object block
291 void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
292 LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
293 Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
296 /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
297 std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
298 assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
299 "Invalid local object reference!");
300 return LocalFrameObjects[i];
303 /// getLocalFrameObjectCount - Return the number of objects allocated into
304 /// the local object block.
305 int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
307 /// setLocalFrameSize - Set the size of the local object blob.
308 void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }
310 /// getLocalFrameSize - Get the size of the local object blob.
311 int64_t getLocalFrameSize() const { return LocalFrameSize; }
313 /// setLocalFrameMaxAlign - Required alignment of the local object blob,
314 /// which is the strictest alignment of any object in it.
315 void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; }
317 /// getLocalFrameMaxAlign - Return the required alignment of the local
319 unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
321 /// getUseLocalStackAllocationBlock - Get whether the local allocation blob
322 /// should be allocated together or let PEI allocate the locals in it
324 bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;}
326 /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
327 /// should be allocated together or let PEI allocate the locals in it
329 void setUseLocalStackAllocationBlock(bool v) {
330 UseLocalStackAllocationBlock = v;
333 /// isObjectPreAllocated - Return true if the object was pre-allocated into
335 bool isObjectPreAllocated(int ObjectIdx) const {
336 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
337 "Invalid Object Idx!");
338 return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
341 /// getObjectSize - Return the size of the specified object.
343 int64_t getObjectSize(int ObjectIdx) const {
344 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
345 "Invalid Object Idx!");
346 return Objects[ObjectIdx+NumFixedObjects].Size;
349 /// setObjectSize - Change the size of the specified stack object.
350 void setObjectSize(int ObjectIdx, int64_t Size) {
351 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
352 "Invalid Object Idx!");
353 Objects[ObjectIdx+NumFixedObjects].Size = Size;
356 /// getObjectAlignment - Return the alignment of the specified stack object.
357 unsigned getObjectAlignment(int ObjectIdx) const {
358 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
359 "Invalid Object Idx!");
360 return Objects[ObjectIdx+NumFixedObjects].Alignment;
363 /// setObjectAlignment - Change the alignment of the specified stack object.
364 void setObjectAlignment(int ObjectIdx, unsigned Align) {
365 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
366 "Invalid Object Idx!");
367 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
368 ensureMaxAlignment(Align);
371 /// getObjectAllocation - Return the underlying Alloca of the specified
372 /// stack object if it exists. Returns 0 if none exists.
373 const AllocaInst* getObjectAllocation(int ObjectIdx) const {
374 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
375 "Invalid Object Idx!");
376 return Objects[ObjectIdx+NumFixedObjects].Alloca;
379 /// NeedsStackProtector - Returns true if the object may need stack
381 bool MayNeedStackProtector(int ObjectIdx) const {
382 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
383 "Invalid Object Idx!");
384 return Objects[ObjectIdx+NumFixedObjects].MayNeedSP;
387 /// getObjectOffset - Return the assigned stack offset of the specified object
388 /// from the incoming stack pointer.
390 int64_t getObjectOffset(int ObjectIdx) const {
391 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
392 "Invalid Object Idx!");
393 assert(!isDeadObjectIndex(ObjectIdx) &&
394 "Getting frame offset for a dead object?");
395 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
398 /// setObjectOffset - Set the stack frame offset of the specified object. The
399 /// offset is relative to the stack pointer on entry to the function.
401 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
402 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
403 "Invalid Object Idx!");
404 assert(!isDeadObjectIndex(ObjectIdx) &&
405 "Setting frame offset for a dead object?");
406 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
409 /// getStackSize - Return the number of bytes that must be allocated to hold
410 /// all of the fixed size frame objects. This is only valid after
411 /// Prolog/Epilog code insertion has finalized the stack frame layout.
413 uint64_t getStackSize() const { return StackSize; }
415 /// setStackSize - Set the size of the stack...
417 void setStackSize(uint64_t Size) { StackSize = Size; }
419 /// getOffsetAdjustment - Return the correction for frame offsets.
421 int getOffsetAdjustment() const { return OffsetAdjustment; }
423 /// setOffsetAdjustment - Set the correction for frame offsets.
425 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
427 /// getMaxAlignment - Return the alignment in bytes that this function must be
428 /// aligned to, which is greater than the default stack alignment provided by
431 unsigned getMaxAlignment() const { return MaxAlignment; }
433 /// ensureMaxAlignment - Make sure the function is at least Align bytes
435 void ensureMaxAlignment(unsigned Align) {
436 if (MaxAlignment < Align) MaxAlignment = Align;
439 /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
440 /// when calling another function. This is only valid during and after
441 /// prolog/epilog code insertion.
442 bool adjustsStack() const { return AdjustsStack; }
443 void setAdjustsStack(bool V) { AdjustsStack = V; }
445 /// hasCalls - Return true if the current function has any function calls.
446 bool hasCalls() const { return HasCalls; }
447 void setHasCalls(bool V) { HasCalls = V; }
449 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
450 /// allocated for an outgoing function call. This is only available if
451 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
452 /// then only during or after prolog/epilog code insertion.
454 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
455 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
457 /// CreateFixedObject - Create a new object at a fixed location on the stack.
458 /// All fixed objects should be created before other objects are created for
459 /// efficiency. By default, fixed objects are immutable. This returns an
460 /// index with a negative value.
462 int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable);
465 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
466 /// fixed stack object.
467 bool isFixedObjectIndex(int ObjectIdx) const {
468 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
471 /// isImmutableObjectIndex - Returns true if the specified index corresponds
472 /// to an immutable object.
473 bool isImmutableObjectIndex(int ObjectIdx) const {
474 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
475 "Invalid Object Idx!");
476 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
479 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
480 /// to a spill slot..
481 bool isSpillSlotObjectIndex(int ObjectIdx) const {
482 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
483 "Invalid Object Idx!");
484 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;
487 /// isDeadObjectIndex - Returns true if the specified index corresponds to
489 bool isDeadObjectIndex(int ObjectIdx) const {
490 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
491 "Invalid Object Idx!");
492 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
495 /// CreateStackObject - Create a new statically sized stack object, returning
496 /// a nonnegative identifier to represent it.
498 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
499 bool MayNeedSP = false, const AllocaInst *Alloca = 0) {
500 assert(Size != 0 && "Cannot allocate zero size stack objects!");
501 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP,
503 int Index = (int)Objects.size() - NumFixedObjects - 1;
504 assert(Index >= 0 && "Bad frame index!");
505 ensureMaxAlignment(Alignment);
509 /// CreateSpillStackObject - Create a new statically sized stack object that
510 /// represents a spill slot, returning a nonnegative identifier to represent
513 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
514 CreateStackObject(Size, Alignment, true, false);
515 int Index = (int)Objects.size() - NumFixedObjects - 1;
516 ensureMaxAlignment(Alignment);
520 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
522 void RemoveStackObject(int ObjectIdx) {
524 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
527 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
528 /// variable sized object has been created. This must be created whenever a
529 /// variable sized object is created, whether or not the index returned is
532 int CreateVariableSizedObject(unsigned Alignment) {
533 HasVarSizedObjects = true;
534 Objects.push_back(StackObject(0, Alignment, 0, false, false, true, 0));
535 ensureMaxAlignment(Alignment);
536 return (int)Objects.size()-NumFixedObjects-1;
539 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
540 /// current function.
541 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
545 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
546 /// callee saved information.
547 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
551 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
552 bool isCalleeSavedInfoValid() const { return CSIValid; }
554 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
556 /// getPristineRegs - Return a set of physical registers that are pristine on
557 /// entry to the MBB.
559 /// Pristine registers hold a value that is useless to the current function,
560 /// but that must be preserved - they are callee saved registers that have not
563 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
564 /// method always returns an empty set.
565 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
567 /// print - Used by the MachineFunction printer to print information about
568 /// stack objects. Implemented in MachineFunction.cpp
570 void print(const MachineFunction &MF, raw_ostream &OS) const;
572 /// dump - Print the function to stderr.
573 void dump(const MachineFunction &MF) const;
576 } // End llvm namespace