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;
32 /// The CalleeSavedInfo class tracks the information need to locate where a
33 /// callee saved register is 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 // PreAllocated - If true, the object was mapped into the local frame
107 // block and doesn't need additional handling for allocation beyond that.
110 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
112 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
113 isSpillSlot(isSS), MayNeedSP(NSP), PreAllocated(false) {}
116 /// Objects - The list of stack objects allocated...
118 std::vector<StackObject> Objects;
120 /// NumFixedObjects - This contains the number of fixed objects contained on
121 /// the stack. Because fixed objects are stored at a negative index in the
122 /// Objects list, this is also the index to the 0th object in the list.
124 unsigned NumFixedObjects;
126 /// HasVarSizedObjects - This boolean keeps track of whether any variable
127 /// sized objects have been allocated yet.
129 bool HasVarSizedObjects;
131 /// FrameAddressTaken - This boolean keeps track of whether there is a call
132 /// to builtin \@llvm.frameaddress.
133 bool FrameAddressTaken;
135 /// ReturnAddressTaken - This boolean keeps track of whether there is a call
136 /// to builtin \@llvm.returnaddress.
137 bool ReturnAddressTaken;
139 /// StackSize - The prolog/epilog code inserter calculates the final stack
140 /// offsets for all of the fixed size objects, updating the Objects list
141 /// above. It then updates StackSize to contain the number of bytes that need
142 /// to be allocated on entry to the function.
146 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
147 /// have the actual offset from the stack/frame pointer. The exact usage of
148 /// this is target-dependent, but it is typically used to adjust between
149 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
150 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
151 /// to the distance between the initial SP and the value in FP. For many
152 /// targets, this value is only used when generating debug info (via
153 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
154 /// corresponding adjustments are performed directly.
155 int OffsetAdjustment;
157 /// MaxAlignment - The prolog/epilog code inserter may process objects
158 /// that require greater alignment than the default alignment the target
159 /// provides. To handle this, MaxAlignment is set to the maximum alignment
160 /// needed by the objects on the current frame. If this is greater than the
161 /// native alignment maintained by the compiler, dynamic alignment code will
164 unsigned MaxAlignment;
166 /// AdjustsStack - Set to true if this function adjusts the stack -- e.g.,
167 /// when calling another function. This is only valid during and after
168 /// prolog/epilog code insertion.
171 /// HasCalls - Set to true if this function has any function calls.
174 /// StackProtectorIdx - The frame index for the stack protector.
175 int StackProtectorIdx;
177 /// FunctionContextIdx - The frame index for the function context. Used for
179 int FunctionContextIdx;
181 /// MaxCallFrameSize - This contains the size of the largest call frame if the
182 /// target uses frame setup/destroy pseudo instructions (as defined in the
183 /// TargetFrameInfo class). This information is important for frame pointer
184 /// elimination. If is only valid during and after prolog/epilog code
187 unsigned MaxCallFrameSize;
189 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
190 /// callee saved register saved in the frame. Beyond its use by the prolog/
191 /// epilog code inserter, this data used for debug info and exception
193 std::vector<CalleeSavedInfo> CSInfo;
195 /// CSIValid - Has CSInfo been set yet?
198 /// TargetFrameLowering - Target information about frame layout.
200 const TargetFrameLowering &TFI;
202 /// LocalFrameObjects - References to frame indices which are mapped
203 /// into the local frame allocation block. <FrameIdx, LocalOffset>
204 SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
206 /// LocalFrameSize - Size of the pre-allocated local frame block.
207 int64_t LocalFrameSize;
209 /// Required alignment of the local object blob, which is the strictest
210 /// alignment of any object in it.
211 unsigned LocalFrameMaxAlign;
213 /// Whether the local object blob needs to be allocated together. If not,
214 /// PEI should ignore the isPreAllocated flags on the stack objects and
215 /// just allocate them normally.
216 bool UseLocalStackAllocationBlock;
219 explicit MachineFrameInfo(const TargetFrameLowering &tfi) : TFI(tfi) {
220 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
221 HasVarSizedObjects = false;
222 FrameAddressTaken = false;
223 ReturnAddressTaken = false;
224 AdjustsStack = false;
226 StackProtectorIdx = -1;
227 FunctionContextIdx = -1;
228 MaxCallFrameSize = 0;
231 LocalFrameMaxAlign = 0;
232 UseLocalStackAllocationBlock = false;
235 /// hasStackObjects - Return true if there are any stack objects in this
238 bool hasStackObjects() const { return !Objects.empty(); }
240 /// hasVarSizedObjects - This method may be called any time after instruction
241 /// selection is complete to determine if the stack frame for this function
242 /// contains any variable sized objects.
244 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
246 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
247 /// stack protector object.
249 int getStackProtectorIndex() const { return StackProtectorIdx; }
250 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
252 /// getFunctionContextIndex/setFunctionContextIndex - Return the index for the
253 /// function context object. This object is used for SjLj exceptions.
254 int getFunctionContextIndex() const { return FunctionContextIdx; }
255 void setFunctionContextIndex(int I) { FunctionContextIdx = I; }
257 /// isFrameAddressTaken - This method may be called any time after instruction
258 /// selection is complete to determine if there is a call to
259 /// \@llvm.frameaddress in this function.
260 bool isFrameAddressTaken() const { return FrameAddressTaken; }
261 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
263 /// isReturnAddressTaken - This method may be called any time after
264 /// instruction selection is complete to determine if there is a call to
265 /// \@llvm.returnaddress in this function.
266 bool isReturnAddressTaken() const { return ReturnAddressTaken; }
267 void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
269 /// getObjectIndexBegin - Return the minimum frame object index.
271 int getObjectIndexBegin() const { return -NumFixedObjects; }
273 /// getObjectIndexEnd - Return one past the maximum frame object index.
275 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
277 /// getNumFixedObjects - Return the number of fixed objects.
278 unsigned getNumFixedObjects() const { return NumFixedObjects; }
280 /// getNumObjects - Return the number of objects.
282 unsigned getNumObjects() const { return Objects.size(); }
284 /// mapLocalFrameObject - Map a frame index into the local object block
285 void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
286 LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
287 Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
290 /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
291 std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
292 assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
293 "Invalid local object reference!");
294 return LocalFrameObjects[i];
297 /// getLocalFrameObjectCount - Return the number of objects allocated into
298 /// the local object block.
299 int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
301 /// setLocalFrameSize - Set the size of the local object blob.
302 void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }
304 /// getLocalFrameSize - Get the size of the local object blob.
305 int64_t getLocalFrameSize() const { return LocalFrameSize; }
307 /// setLocalFrameMaxAlign - Required alignment of the local object blob,
308 /// which is the strictest alignment of any object in it.
309 void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; }
311 /// getLocalFrameMaxAlign - Return the required alignment of the local
313 unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
315 /// getUseLocalStackAllocationBlock - Get whether the local allocation blob
316 /// should be allocated together or let PEI allocate the locals in it
318 bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;}
320 /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
321 /// should be allocated together or let PEI allocate the locals in it
323 void setUseLocalStackAllocationBlock(bool v) {
324 UseLocalStackAllocationBlock = v;
327 /// isObjectPreAllocated - Return true if the object was pre-allocated into
329 bool isObjectPreAllocated(int ObjectIdx) const {
330 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
331 "Invalid Object Idx!");
332 return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
335 /// getObjectSize - Return the size of the specified object.
337 int64_t getObjectSize(int ObjectIdx) const {
338 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
339 "Invalid Object Idx!");
340 return Objects[ObjectIdx+NumFixedObjects].Size;
343 /// setObjectSize - Change the size of the specified stack object.
344 void setObjectSize(int ObjectIdx, int64_t Size) {
345 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
346 "Invalid Object Idx!");
347 Objects[ObjectIdx+NumFixedObjects].Size = Size;
350 /// getObjectAlignment - Return the alignment of the specified stack object.
351 unsigned getObjectAlignment(int ObjectIdx) const {
352 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
353 "Invalid Object Idx!");
354 return Objects[ObjectIdx+NumFixedObjects].Alignment;
357 /// setObjectAlignment - Change the alignment of the specified stack object.
358 void setObjectAlignment(int ObjectIdx, unsigned Align) {
359 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
360 "Invalid Object Idx!");
361 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
362 ensureMaxAlignment(Align);
365 /// NeedsStackProtector - Returns true if the object may need stack
367 bool MayNeedStackProtector(int ObjectIdx) const {
368 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
369 "Invalid Object Idx!");
370 return Objects[ObjectIdx+NumFixedObjects].MayNeedSP;
373 /// getObjectOffset - Return the assigned stack offset of the specified object
374 /// from the incoming stack pointer.
376 int64_t getObjectOffset(int ObjectIdx) const {
377 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
378 "Invalid Object Idx!");
379 assert(!isDeadObjectIndex(ObjectIdx) &&
380 "Getting frame offset for a dead object?");
381 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
384 /// setObjectOffset - Set the stack frame offset of the specified object. The
385 /// offset is relative to the stack pointer on entry to the function.
387 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
388 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
389 "Invalid Object Idx!");
390 assert(!isDeadObjectIndex(ObjectIdx) &&
391 "Setting frame offset for a dead object?");
392 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
395 /// getStackSize - Return the number of bytes that must be allocated to hold
396 /// all of the fixed size frame objects. This is only valid after
397 /// Prolog/Epilog code insertion has finalized the stack frame layout.
399 uint64_t getStackSize() const { return StackSize; }
401 /// setStackSize - Set the size of the stack...
403 void setStackSize(uint64_t Size) { StackSize = Size; }
405 /// getOffsetAdjustment - Return the correction for frame offsets.
407 int getOffsetAdjustment() const { return OffsetAdjustment; }
409 /// setOffsetAdjustment - Set the correction for frame offsets.
411 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
413 /// getMaxAlignment - Return the alignment in bytes that this function must be
414 /// aligned to, which is greater than the default stack alignment provided by
417 unsigned getMaxAlignment() const { return MaxAlignment; }
419 /// ensureMaxAlignment - Make sure the function is at least Align bytes
421 void ensureMaxAlignment(unsigned Align) {
422 if (MaxAlignment < Align) MaxAlignment = Align;
425 /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
426 /// when calling another function. This is only valid during and after
427 /// prolog/epilog code insertion.
428 bool adjustsStack() const { return AdjustsStack; }
429 void setAdjustsStack(bool V) { AdjustsStack = V; }
431 /// hasCalls - Return true if the current function has any function calls.
432 bool hasCalls() const { return HasCalls; }
433 void setHasCalls(bool V) { HasCalls = V; }
435 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
436 /// allocated for an outgoing function call. This is only available if
437 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
438 /// then only during or after prolog/epilog code insertion.
440 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
441 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
443 /// CreateFixedObject - Create a new object at a fixed location on the stack.
444 /// All fixed objects should be created before other objects are created for
445 /// efficiency. By default, fixed objects are immutable. This returns an
446 /// index with a negative value.
448 int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable);
451 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
452 /// fixed stack object.
453 bool isFixedObjectIndex(int ObjectIdx) const {
454 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
457 /// isImmutableObjectIndex - Returns true if the specified index corresponds
458 /// to an immutable object.
459 bool isImmutableObjectIndex(int ObjectIdx) const {
460 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
461 "Invalid Object Idx!");
462 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
465 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
466 /// to a spill slot..
467 bool isSpillSlotObjectIndex(int ObjectIdx) const {
468 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
469 "Invalid Object Idx!");
470 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;
473 /// isDeadObjectIndex - Returns true if the specified index corresponds to
475 bool isDeadObjectIndex(int ObjectIdx) const {
476 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
477 "Invalid Object Idx!");
478 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
481 /// CreateStackObject - Create a new statically sized stack object, returning
482 /// a nonnegative identifier to represent it.
484 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
485 bool MayNeedSP = false) {
486 assert(Size != 0 && "Cannot allocate zero size stack objects!");
487 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP));
488 int Index = (int)Objects.size() - NumFixedObjects - 1;
489 assert(Index >= 0 && "Bad frame index!");
490 ensureMaxAlignment(Alignment);
494 /// CreateSpillStackObject - Create a new statically sized stack object that
495 /// represents a spill slot, returning a nonnegative identifier to represent
498 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
499 CreateStackObject(Size, Alignment, true, false);
500 int Index = (int)Objects.size() - NumFixedObjects - 1;
501 ensureMaxAlignment(Alignment);
505 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
507 void RemoveStackObject(int ObjectIdx) {
509 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
512 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
513 /// variable sized object has been created. This must be created whenever a
514 /// variable sized object is created, whether or not the index returned is
517 int CreateVariableSizedObject(unsigned Alignment) {
518 HasVarSizedObjects = true;
519 Objects.push_back(StackObject(0, Alignment, 0, false, false, true));
520 ensureMaxAlignment(Alignment);
521 return (int)Objects.size()-NumFixedObjects-1;
524 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
525 /// current function.
526 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
530 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
531 /// callee saved information.
532 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
536 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
537 bool isCalleeSavedInfoValid() const { return CSIValid; }
539 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
541 /// getPristineRegs - Return a set of physical registers that are pristine on
542 /// entry to the MBB.
544 /// Pristine registers hold a value that is useless to the current function,
545 /// but that must be preserved - they are callee saved registers that have not
548 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
549 /// method always returns an empty set.
550 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
552 /// print - Used by the MachineFunction printer to print information about
553 /// stack objects. Implemented in MachineFunction.cpp
555 void print(const MachineFunction &MF, raw_ostream &OS) const;
557 /// dump - Print the function to stderr.
558 void dump(const MachineFunction &MF) const;
561 } // End llvm namespace