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;
224 /// Whether the "realign-stack" option is on.
227 explicit MachineFrameInfo(const TargetFrameLowering &tfi, bool RealignOpt)
228 : TFI(tfi), RealignOption(RealignOpt) {
229 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
230 HasVarSizedObjects = false;
231 FrameAddressTaken = false;
232 ReturnAddressTaken = false;
233 AdjustsStack = false;
235 StackProtectorIdx = -1;
236 FunctionContextIdx = -1;
237 MaxCallFrameSize = 0;
240 LocalFrameMaxAlign = 0;
241 UseLocalStackAllocationBlock = false;
244 /// hasStackObjects - Return true if there are any stack objects in this
247 bool hasStackObjects() const { return !Objects.empty(); }
249 /// hasVarSizedObjects - This method may be called any time after instruction
250 /// selection is complete to determine if the stack frame for this function
251 /// contains any variable sized objects.
253 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
255 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
256 /// stack protector object.
258 int getStackProtectorIndex() const { return StackProtectorIdx; }
259 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
261 /// getFunctionContextIndex/setFunctionContextIndex - Return the index for the
262 /// function context object. This object is used for SjLj exceptions.
263 int getFunctionContextIndex() const { return FunctionContextIdx; }
264 void setFunctionContextIndex(int I) { FunctionContextIdx = I; }
266 /// isFrameAddressTaken - This method may be called any time after instruction
267 /// selection is complete to determine if there is a call to
268 /// \@llvm.frameaddress in this function.
269 bool isFrameAddressTaken() const { return FrameAddressTaken; }
270 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
272 /// isReturnAddressTaken - This method may be called any time after
273 /// instruction selection is complete to determine if there is a call to
274 /// \@llvm.returnaddress in this function.
275 bool isReturnAddressTaken() const { return ReturnAddressTaken; }
276 void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
278 /// getObjectIndexBegin - Return the minimum frame object index.
280 int getObjectIndexBegin() const { return -NumFixedObjects; }
282 /// getObjectIndexEnd - Return one past the maximum frame object index.
284 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
286 /// getNumFixedObjects - Return the number of fixed objects.
287 unsigned getNumFixedObjects() const { return NumFixedObjects; }
289 /// getNumObjects - Return the number of objects.
291 unsigned getNumObjects() const { return Objects.size(); }
293 /// mapLocalFrameObject - Map a frame index into the local object block
294 void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
295 LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
296 Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
299 /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
300 std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
301 assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
302 "Invalid local object reference!");
303 return LocalFrameObjects[i];
306 /// getLocalFrameObjectCount - Return the number of objects allocated into
307 /// the local object block.
308 int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
310 /// setLocalFrameSize - Set the size of the local object blob.
311 void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }
313 /// getLocalFrameSize - Get the size of the local object blob.
314 int64_t getLocalFrameSize() const { return LocalFrameSize; }
316 /// setLocalFrameMaxAlign - Required alignment of the local object blob,
317 /// which is the strictest alignment of any object in it.
318 void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; }
320 /// getLocalFrameMaxAlign - Return the required alignment of the local
322 unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
324 /// getUseLocalStackAllocationBlock - Get whether the local allocation blob
325 /// should be allocated together or let PEI allocate the locals in it
327 bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;}
329 /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
330 /// should be allocated together or let PEI allocate the locals in it
332 void setUseLocalStackAllocationBlock(bool v) {
333 UseLocalStackAllocationBlock = v;
336 /// isObjectPreAllocated - Return true if the object was pre-allocated into
338 bool isObjectPreAllocated(int ObjectIdx) const {
339 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
340 "Invalid Object Idx!");
341 return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
344 /// getObjectSize - Return the size of the specified object.
346 int64_t getObjectSize(int ObjectIdx) const {
347 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
348 "Invalid Object Idx!");
349 return Objects[ObjectIdx+NumFixedObjects].Size;
352 /// setObjectSize - Change the size of the specified stack object.
353 void setObjectSize(int ObjectIdx, int64_t Size) {
354 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
355 "Invalid Object Idx!");
356 Objects[ObjectIdx+NumFixedObjects].Size = Size;
359 /// getObjectAlignment - Return the alignment of the specified stack object.
360 unsigned getObjectAlignment(int ObjectIdx) const {
361 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
362 "Invalid Object Idx!");
363 return Objects[ObjectIdx+NumFixedObjects].Alignment;
366 /// setObjectAlignment - Change the alignment of the specified stack object.
367 void setObjectAlignment(int ObjectIdx, unsigned Align) {
368 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
369 "Invalid Object Idx!");
370 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
371 ensureMaxAlignment(Align);
374 /// getObjectAllocation - Return the underlying Alloca of the specified
375 /// stack object if it exists. Returns 0 if none exists.
376 const AllocaInst* getObjectAllocation(int ObjectIdx) const {
377 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
378 "Invalid Object Idx!");
379 return Objects[ObjectIdx+NumFixedObjects].Alloca;
382 /// NeedsStackProtector - Returns true if the object may need stack
384 bool MayNeedStackProtector(int ObjectIdx) const {
385 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
386 "Invalid Object Idx!");
387 return Objects[ObjectIdx+NumFixedObjects].MayNeedSP;
390 /// getObjectOffset - Return the assigned stack offset of the specified object
391 /// from the incoming stack pointer.
393 int64_t getObjectOffset(int ObjectIdx) const {
394 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
395 "Invalid Object Idx!");
396 assert(!isDeadObjectIndex(ObjectIdx) &&
397 "Getting frame offset for a dead object?");
398 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
401 /// setObjectOffset - Set the stack frame offset of the specified object. The
402 /// offset is relative to the stack pointer on entry to the function.
404 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
405 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
406 "Invalid Object Idx!");
407 assert(!isDeadObjectIndex(ObjectIdx) &&
408 "Setting frame offset for a dead object?");
409 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
412 /// getStackSize - Return the number of bytes that must be allocated to hold
413 /// all of the fixed size frame objects. This is only valid after
414 /// Prolog/Epilog code insertion has finalized the stack frame layout.
416 uint64_t getStackSize() const { return StackSize; }
418 /// setStackSize - Set the size of the stack...
420 void setStackSize(uint64_t Size) { StackSize = Size; }
422 /// Estimate and return the size of the stack frame.
423 unsigned estimateStackSize(const MachineFunction &MF) const;
425 /// getOffsetAdjustment - Return the correction for frame offsets.
427 int getOffsetAdjustment() const { return OffsetAdjustment; }
429 /// setOffsetAdjustment - Set the correction for frame offsets.
431 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
433 /// getMaxAlignment - Return the alignment in bytes that this function must be
434 /// aligned to, which is greater than the default stack alignment provided by
437 unsigned getMaxAlignment() const { return MaxAlignment; }
439 /// ensureMaxAlignment - Make sure the function is at least Align bytes
441 void ensureMaxAlignment(unsigned Align);
443 /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
444 /// when calling another function. This is only valid during and after
445 /// prolog/epilog code insertion.
446 bool adjustsStack() const { return AdjustsStack; }
447 void setAdjustsStack(bool V) { AdjustsStack = V; }
449 /// hasCalls - Return true if the current function has any function calls.
450 bool hasCalls() const { return HasCalls; }
451 void setHasCalls(bool V) { HasCalls = V; }
453 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
454 /// allocated for an outgoing function call. This is only available if
455 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
456 /// then only during or after prolog/epilog code insertion.
458 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
459 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
461 /// CreateFixedObject - Create a new object at a fixed location on the stack.
462 /// All fixed objects should be created before other objects are created for
463 /// efficiency. By default, fixed objects are immutable. This returns an
464 /// index with a negative value.
466 int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable);
469 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
470 /// fixed stack object.
471 bool isFixedObjectIndex(int ObjectIdx) const {
472 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
475 /// isImmutableObjectIndex - Returns true if the specified index corresponds
476 /// to an immutable object.
477 bool isImmutableObjectIndex(int ObjectIdx) const {
478 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
479 "Invalid Object Idx!");
480 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
483 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
484 /// to a spill slot..
485 bool isSpillSlotObjectIndex(int ObjectIdx) const {
486 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
487 "Invalid Object Idx!");
488 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;
491 /// isDeadObjectIndex - Returns true if the specified index corresponds to
493 bool isDeadObjectIndex(int ObjectIdx) const {
494 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
495 "Invalid Object Idx!");
496 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
499 /// CreateStackObject - Create a new statically sized stack object, returning
500 /// a nonnegative identifier to represent it.
502 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
503 bool MayNeedSP = false, const AllocaInst *Alloca = 0);
505 /// CreateSpillStackObject - Create a new statically sized stack object that
506 /// represents a spill slot, returning a nonnegative identifier to represent
509 int CreateSpillStackObject(uint64_t Size, unsigned Alignment);
511 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
513 void RemoveStackObject(int ObjectIdx) {
515 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
518 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
519 /// variable sized object has been created. This must be created whenever a
520 /// variable sized object is created, whether or not the index returned is
523 int CreateVariableSizedObject(unsigned Alignment);
525 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
526 /// current function.
527 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
531 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
532 /// callee saved information.
533 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
537 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
538 bool isCalleeSavedInfoValid() const { return CSIValid; }
540 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
542 /// getPristineRegs - Return a set of physical registers that are pristine on
543 /// entry to the MBB.
545 /// Pristine registers hold a value that is useless to the current function,
546 /// but that must be preserved - they are callee saved registers that have not
549 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
550 /// method always returns an empty set.
551 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
553 /// print - Used by the MachineFunction printer to print information about
554 /// stack objects. Implemented in MachineFunction.cpp
556 void print(const MachineFunction &MF, raw_ostream &OS) const;
558 /// dump - Print the function to stderr.
559 void dump(const MachineFunction &MF) const;
562 } // End llvm namespace