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/System/DataTypes.h"
26 class TargetRegisterClass;
28 class MachineFunction;
29 class MachineBasicBlock;
30 class TargetFrameInfo;
33 /// The CalleeSavedInfo class tracks the information need to locate where a
34 /// callee saved register 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 /// SpillObjects - A vector indicating which frame indices refer to
197 SmallVector<bool, 8> SpillObjects;
199 /// TargetFrameInfo - Target information about frame layout.
201 const TargetFrameInfo &TFI;
203 /// LocalFrameObjects - References to frame indices which are mapped
204 /// into the local frame allocation block. <FrameIdx, LocalOffset>
205 SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
207 /// LocalFrameSize - Size of the pre-allocated local frame block.
208 int64_t LocalFrameSize;
210 /// LocalFrameBaseOffset - The base offset from the stack pointer at
211 /// function entry of the local frame blob. Set by PEI for use by
212 /// target in eliminateFrameIndex().
213 int64_t LocalFrameBaseOffset;
216 explicit MachineFrameInfo(const TargetFrameInfo &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 LocalFrameBaseOffset = 0;
230 /// hasStackObjects - Return true if there are any stack objects in this
233 bool hasStackObjects() const { return !Objects.empty(); }
235 /// hasVarSizedObjects - This method may be called any time after instruction
236 /// selection is complete to determine if the stack frame for this function
237 /// contains any variable sized objects.
239 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
241 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
242 /// stack protector object.
244 int getStackProtectorIndex() const { return StackProtectorIdx; }
245 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
247 /// isFrameAddressTaken - This method may be called any time after instruction
248 /// selection is complete to determine if there is a call to
249 /// \@llvm.frameaddress in this function.
250 bool isFrameAddressTaken() const { return FrameAddressTaken; }
251 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
253 /// isReturnAddressTaken - This method may be called any time after
254 /// instruction selection is complete to determine if there is a call to
255 /// \@llvm.returnaddress in this function.
256 bool isReturnAddressTaken() const { return ReturnAddressTaken; }
257 void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
259 /// getObjectIndexBegin - Return the minimum frame object index.
261 int getObjectIndexBegin() const { return -NumFixedObjects; }
263 /// getObjectIndexEnd - Return one past the maximum frame object index.
265 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
267 /// getNumFixedObjects - Return the number of fixed objects.
268 unsigned getNumFixedObjects() const { return NumFixedObjects; }
270 /// getNumObjects - Return the number of objects.
272 unsigned getNumObjects() const { return Objects.size(); }
274 /// mapLocalFrameObject - Map a frame index into the local object block
275 void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
276 LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
277 Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
280 /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
281 std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
282 assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
283 "Invalid local object reference!");
284 return LocalFrameObjects[i];
287 /// getLocalFrameObjectCount - Return the number of objects allocated into
288 /// the local object block.
289 int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
291 /// setLocalFrameBaseOffset - Set the base SP offset of the local frame
293 void setLocalFrameBaseOffset(int64_t o) { LocalFrameBaseOffset = o; }
295 /// getLocalFrameBaseOffset - Get the base SP offset of the local frame
297 int64_t getLocalFrameBaseOffset() const { return LocalFrameBaseOffset; }
299 /// getLocalFrameSize - Get the size of the local object blob.
300 int64_t getLocalFrameSize() const { return LocalFrameSize; }
302 /// isObjectPreAllocated - Return true if the object was pre-allocated into
304 bool isObjectPreAllocated(int ObjectIdx) const {
305 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
306 "Invalid Object Idx!");
307 return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
310 /// getObjectSize - Return the size of the specified object.
312 int64_t getObjectSize(int ObjectIdx) const {
313 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
314 "Invalid Object Idx!");
315 return Objects[ObjectIdx+NumFixedObjects].Size;
318 /// setObjectSize - Change the size of the specified stack object.
319 void setObjectSize(int ObjectIdx, int64_t Size) {
320 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
321 "Invalid Object Idx!");
322 Objects[ObjectIdx+NumFixedObjects].Size = Size;
325 /// getObjectAlignment - Return the alignment of the specified stack object.
326 unsigned getObjectAlignment(int ObjectIdx) const {
327 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
328 "Invalid Object Idx!");
329 return Objects[ObjectIdx+NumFixedObjects].Alignment;
332 /// setObjectAlignment - Change the alignment of the specified stack object.
333 void setObjectAlignment(int ObjectIdx, unsigned Align) {
334 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
335 "Invalid Object Idx!");
336 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
337 MaxAlignment = std::max(MaxAlignment, Align);
340 /// NeedsStackProtector - Returns true if the object may need stack
342 bool MayNeedStackProtector(int ObjectIdx) const {
343 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
344 "Invalid Object Idx!");
345 return Objects[ObjectIdx+NumFixedObjects].MayNeedSP;
348 /// getObjectOffset - Return the assigned stack offset of the specified object
349 /// from the incoming stack pointer.
351 int64_t getObjectOffset(int ObjectIdx) const {
352 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
353 "Invalid Object Idx!");
354 assert(!isDeadObjectIndex(ObjectIdx) &&
355 "Getting frame offset for a dead object?");
356 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
359 /// setObjectOffset - Set the stack frame offset of the specified object. The
360 /// offset is relative to the stack pointer on entry to the function.
362 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
363 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
364 "Invalid Object Idx!");
365 assert(!isDeadObjectIndex(ObjectIdx) &&
366 "Setting frame offset for a dead object?");
367 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
370 /// getStackSize - Return the number of bytes that must be allocated to hold
371 /// all of the fixed size frame objects. This is only valid after
372 /// Prolog/Epilog code insertion has finalized the stack frame layout.
374 uint64_t getStackSize() const { return StackSize; }
376 /// setStackSize - Set the size of the stack...
378 void setStackSize(uint64_t Size) { StackSize = Size; }
380 /// getOffsetAdjustment - Return the correction for frame offsets.
382 int getOffsetAdjustment() const { return OffsetAdjustment; }
384 /// setOffsetAdjustment - Set the correction for frame offsets.
386 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
388 /// getMaxAlignment - Return the alignment in bytes that this function must be
389 /// aligned to, which is greater than the default stack alignment provided by
392 unsigned getMaxAlignment() const { return MaxAlignment; }
394 /// setMaxAlignment - Set the preferred alignment.
396 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
398 /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
399 /// when calling another function. This is only valid during and after
400 /// prolog/epilog code insertion.
401 bool adjustsStack() const { return AdjustsStack; }
402 void setAdjustsStack(bool V) { AdjustsStack = V; }
404 /// hasCalls - Return true if the current function has any function calls.
405 bool hasCalls() const { return HasCalls; }
406 void setHasCalls(bool V) { HasCalls = V; }
408 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
409 /// allocated for an outgoing function call. This is only available if
410 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
411 /// then only during or after prolog/epilog code insertion.
413 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
414 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
416 /// CreateFixedObject - Create a new object at a fixed location on the stack.
417 /// All fixed objects should be created before other objects are created for
418 /// efficiency. By default, fixed objects are immutable. This returns an
419 /// index with a negative value.
421 int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable);
424 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
425 /// fixed stack object.
426 bool isFixedObjectIndex(int ObjectIdx) const {
427 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
430 /// isImmutableObjectIndex - Returns true if the specified index corresponds
431 /// to an immutable object.
432 bool isImmutableObjectIndex(int ObjectIdx) const {
433 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
434 "Invalid Object Idx!");
435 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
438 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
439 /// to a spill slot..
440 bool isSpillSlotObjectIndex(int ObjectIdx) const {
441 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
442 "Invalid Object Idx!");
443 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;;
446 /// isDeadObjectIndex - Returns true if the specified index corresponds to
448 bool isDeadObjectIndex(int ObjectIdx) const {
449 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
450 "Invalid Object Idx!");
451 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
454 /// CreateStackObject - Create a new statically sized stack object, returning
455 /// a nonnegative identifier to represent it.
457 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
458 bool MayNeedSP = false) {
459 assert(Size != 0 && "Cannot allocate zero size stack objects!");
460 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP));
461 int Index = (int)Objects.size() - NumFixedObjects - 1;
462 assert(Index >= 0 && "Bad frame index!");
463 MaxAlignment = std::max(MaxAlignment, Alignment);
467 /// CreateSpillStackObject - Create a new statically sized stack object that
468 /// represents a spill slot, returning a nonnegative identifier to represent
471 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
472 CreateStackObject(Size, Alignment, true, false);
473 int Index = (int)Objects.size() - NumFixedObjects - 1;
474 MaxAlignment = std::max(MaxAlignment, Alignment);
478 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
480 void RemoveStackObject(int ObjectIdx) {
482 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
485 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
486 /// variable sized object has been created. This must be created whenever a
487 /// variable sized object is created, whether or not the index returned is
490 int CreateVariableSizedObject(unsigned Alignment) {
491 HasVarSizedObjects = true;
492 Objects.push_back(StackObject(0, Alignment, 0, false, false, true));
493 MaxAlignment = std::max(MaxAlignment, Alignment);
494 return (int)Objects.size()-NumFixedObjects-1;
497 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
498 /// current function.
499 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
503 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
504 /// callee saved information.
505 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
509 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
510 bool isCalleeSavedInfoValid() const { return CSIValid; }
512 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
514 /// getPristineRegs - Return a set of physical registers that are pristine on
515 /// entry to the MBB.
517 /// Pristine registers hold a value that is useless to the current function,
518 /// but that must be preserved - they are callee saved registers that have not
521 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
522 /// method always returns an empty set.
523 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
525 /// print - Used by the MachineFunction printer to print information about
526 /// stack objects. Implemented in MachineFunction.cpp
528 void print(const MachineFunction &MF, raw_ostream &OS) const;
530 /// dump - Print the function to stderr.
531 void dump(const MachineFunction &MF) const;
534 } // End llvm namespace