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;
35 /// The CalleeSavedInfo class tracks the information need to locate where a
36 /// callee saved register is in the current frame.
37 class CalleeSavedInfo {
42 explicit CalleeSavedInfo(unsigned R, int FI = 0)
43 : Reg(R), FrameIdx(FI) {}
46 unsigned getReg() const { return Reg; }
47 int getFrameIdx() const { return FrameIdx; }
48 void setFrameIdx(int FI) { FrameIdx = FI; }
51 /// The MachineFrameInfo class represents an abstract stack frame until
52 /// prolog/epilog code is inserted. This class is key to allowing stack frame
53 /// representation optimizations, such as frame pointer elimination. It also
54 /// allows more mundane (but still important) optimizations, such as reordering
55 /// of abstract objects on the stack frame.
57 /// To support this, the class assigns unique integer identifiers to stack
58 /// objects requested clients. These identifiers are negative integers for
59 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
60 /// for objects that may be reordered. Instructions which refer to stack
61 /// objects use a special MO_FrameIndex operand to represent these frame
64 /// Because this class keeps track of all references to the stack frame, it
65 /// knows when a variable sized object is allocated on the stack. This is the
66 /// sole condition which prevents frame pointer elimination, which is an
67 /// important optimization on register-poor architectures. Because original
68 /// variable sized alloca's in the source program are the only source of
69 /// variable sized stack objects, it is safe to decide whether there will be
70 /// any variable sized objects before all stack objects are known (for
71 /// example, register allocator spill code never needs variable sized
74 /// When prolog/epilog code emission is performed, the final stack frame is
75 /// built and the machine instructions are modified to refer to the actual
76 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
79 /// @brief Abstract Stack Frame Information
80 class MachineFrameInfo {
82 // StackObject - Represent a single object allocated on the stack.
84 // SPOffset - The offset of this object from the stack pointer on entry to
85 // the function. This field has no meaning for a variable sized element.
88 // The size of this object on the stack. 0 means a variable sized object,
89 // ~0ULL means a dead object.
92 // Alignment - The required alignment of this stack slot.
95 // isImmutable - If true, the value of the stack object is set before
96 // entering the function and is not modified inside the function. By
97 // default, fixed objects are immutable unless marked otherwise.
100 // isSpillSlot - If true the stack object is used as spill slot. It
101 // cannot alias any other memory objects.
104 /// Alloca - If this stack object is originated from an Alloca instruction
105 /// this value saves the original IR allocation. Can be NULL.
106 const AllocaInst *Alloca;
108 // PreAllocated - If true, the object was mapped into the local frame
109 // block and doesn't need additional handling for allocation beyond that.
112 // If true, an LLVM IR value might point to this object.
113 // Normally, spill slots and fixed-offset objects don't alias IR-accessible
114 // objects, but there are exceptions (on PowerPC, for example, some byval
115 // arguments have ABI-prescribed offsets).
118 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
119 bool isSS, const AllocaInst *Val, bool A)
120 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
121 isSpillSlot(isSS), Alloca(Val), PreAllocated(false), isAliased(A) {}
124 const TargetMachine &TM;
126 /// Objects - The list of stack objects allocated...
128 std::vector<StackObject> Objects;
130 /// NumFixedObjects - This contains the number of fixed objects contained on
131 /// the stack. Because fixed objects are stored at a negative index in the
132 /// Objects list, this is also the index to the 0th object in the list.
134 unsigned NumFixedObjects;
136 /// HasVarSizedObjects - This boolean keeps track of whether any variable
137 /// sized objects have been allocated yet.
139 bool HasVarSizedObjects;
141 /// FrameAddressTaken - This boolean keeps track of whether there is a call
142 /// to builtin \@llvm.frameaddress.
143 bool FrameAddressTaken;
145 /// ReturnAddressTaken - This boolean keeps track of whether there is a call
146 /// to builtin \@llvm.returnaddress.
147 bool ReturnAddressTaken;
149 /// HasStackMap - This boolean keeps track of whether there is a call
150 /// to builtin \@llvm.experimental.stackmap.
153 /// HasPatchPoint - This boolean keeps track of whether there is a call
154 /// to builtin \@llvm.experimental.patchpoint.
157 /// StackSize - The prolog/epilog code inserter calculates the final stack
158 /// offsets for all of the fixed size objects, updating the Objects list
159 /// above. It then updates StackSize to contain the number of bytes that need
160 /// to be allocated on entry to the function.
164 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
165 /// have the actual offset from the stack/frame pointer. The exact usage of
166 /// this is target-dependent, but it is typically used to adjust between
167 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
168 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
169 /// to the distance between the initial SP and the value in FP. For many
170 /// targets, this value is only used when generating debug info (via
171 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
172 /// corresponding adjustments are performed directly.
173 int OffsetAdjustment;
175 /// MaxAlignment - The prolog/epilog code inserter may process objects
176 /// that require greater alignment than the default alignment the target
177 /// provides. To handle this, MaxAlignment is set to the maximum alignment
178 /// needed by the objects on the current frame. If this is greater than the
179 /// native alignment maintained by the compiler, dynamic alignment code will
182 unsigned MaxAlignment;
184 /// AdjustsStack - Set to true if this function adjusts the stack -- e.g.,
185 /// when calling another function. This is only valid during and after
186 /// prolog/epilog code insertion.
189 /// HasCalls - Set to true if this function has any function calls.
192 /// StackProtectorIdx - The frame index for the stack protector.
193 int StackProtectorIdx;
195 /// FunctionContextIdx - The frame index for the function context. Used for
197 int FunctionContextIdx;
199 /// MaxCallFrameSize - This contains the size of the largest call frame if the
200 /// target uses frame setup/destroy pseudo instructions (as defined in the
201 /// TargetFrameInfo class). This information is important for frame pointer
202 /// elimination. If is only valid during and after prolog/epilog code
205 unsigned MaxCallFrameSize;
207 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
208 /// callee saved register saved in the frame. Beyond its use by the prolog/
209 /// epilog code inserter, this data used for debug info and exception
211 std::vector<CalleeSavedInfo> CSInfo;
213 /// CSIValid - Has CSInfo been set yet?
216 /// LocalFrameObjects - References to frame indices which are mapped
217 /// into the local frame allocation block. <FrameIdx, LocalOffset>
218 SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
220 /// LocalFrameSize - Size of the pre-allocated local frame block.
221 int64_t LocalFrameSize;
223 /// Required alignment of the local object blob, which is the strictest
224 /// alignment of any object in it.
225 unsigned LocalFrameMaxAlign;
227 /// Whether the local object blob needs to be allocated together. If not,
228 /// PEI should ignore the isPreAllocated flags on the stack objects and
229 /// just allocate them normally.
230 bool UseLocalStackAllocationBlock;
232 /// Whether the "realign-stack" option is on.
235 /// True if the function includes inline assembly that adjusts the stack
237 bool HasInlineAsmWithSPAdjust;
239 /// True if the function contains a call to the llvm.vastart intrinsic.
242 /// True if this is a varargs function that contains a musttail call.
243 bool HasMustTailInVarArgFunc;
245 const TargetFrameLowering *getFrameLowering() const;
247 explicit MachineFrameInfo(const TargetMachine &TM, bool RealignOpt)
248 : TM(TM), RealignOption(RealignOpt) {
249 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
250 HasVarSizedObjects = false;
251 FrameAddressTaken = false;
252 ReturnAddressTaken = false;
254 HasPatchPoint = false;
255 AdjustsStack = false;
257 StackProtectorIdx = -1;
258 FunctionContextIdx = -1;
259 MaxCallFrameSize = 0;
262 LocalFrameMaxAlign = 0;
263 UseLocalStackAllocationBlock = false;
264 HasInlineAsmWithSPAdjust = false;
266 HasMustTailInVarArgFunc = false;
269 /// hasStackObjects - Return true if there are any stack objects in this
272 bool hasStackObjects() const { return !Objects.empty(); }
274 /// hasVarSizedObjects - This method may be called any time after instruction
275 /// selection is complete to determine if the stack frame for this function
276 /// contains any variable sized objects.
278 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
280 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
281 /// stack protector object.
283 int getStackProtectorIndex() const { return StackProtectorIdx; }
284 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
286 /// getFunctionContextIndex/setFunctionContextIndex - Return the index for the
287 /// function context object. This object is used for SjLj exceptions.
288 int getFunctionContextIndex() const { return FunctionContextIdx; }
289 void setFunctionContextIndex(int I) { FunctionContextIdx = I; }
291 /// isFrameAddressTaken - This method may be called any time after instruction
292 /// selection is complete to determine if there is a call to
293 /// \@llvm.frameaddress in this function.
294 bool isFrameAddressTaken() const { return FrameAddressTaken; }
295 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
297 /// isReturnAddressTaken - This method may be called any time after
298 /// instruction selection is complete to determine if there is a call to
299 /// \@llvm.returnaddress in this function.
300 bool isReturnAddressTaken() const { return ReturnAddressTaken; }
301 void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; }
303 /// hasStackMap - This method may be called any time after instruction
304 /// selection is complete to determine if there is a call to builtin
305 /// \@llvm.experimental.stackmap.
306 bool hasStackMap() const { return HasStackMap; }
307 void setHasStackMap(bool s = true) { HasStackMap = s; }
309 /// hasPatchPoint - This method may be called any time after instruction
310 /// selection is complete to determine if there is a call to builtin
311 /// \@llvm.experimental.patchpoint.
312 bool hasPatchPoint() const { return HasPatchPoint; }
313 void setHasPatchPoint(bool s = true) { HasPatchPoint = s; }
315 /// getObjectIndexBegin - Return the minimum frame object index.
317 int getObjectIndexBegin() const { return -NumFixedObjects; }
319 /// getObjectIndexEnd - Return one past the maximum frame object index.
321 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
323 /// getNumFixedObjects - Return the number of fixed objects.
324 unsigned getNumFixedObjects() const { return NumFixedObjects; }
326 /// getNumObjects - Return the number of objects.
328 unsigned getNumObjects() const { return Objects.size(); }
330 /// mapLocalFrameObject - Map a frame index into the local object block
331 void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
332 LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
333 Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
336 /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
337 std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
338 assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
339 "Invalid local object reference!");
340 return LocalFrameObjects[i];
343 /// getLocalFrameObjectCount - Return the number of objects allocated into
344 /// the local object block.
345 int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
347 /// setLocalFrameSize - Set the size of the local object blob.
348 void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }
350 /// getLocalFrameSize - Get the size of the local object blob.
351 int64_t getLocalFrameSize() const { return LocalFrameSize; }
353 /// setLocalFrameMaxAlign - Required alignment of the local object blob,
354 /// which is the strictest alignment of any object in it.
355 void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; }
357 /// getLocalFrameMaxAlign - Return the required alignment of the local
359 unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
361 /// getUseLocalStackAllocationBlock - Get whether the local allocation blob
362 /// should be allocated together or let PEI allocate the locals in it
364 bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;}
366 /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
367 /// should be allocated together or let PEI allocate the locals in it
369 void setUseLocalStackAllocationBlock(bool v) {
370 UseLocalStackAllocationBlock = v;
373 /// isObjectPreAllocated - Return true if the object was pre-allocated into
375 bool isObjectPreAllocated(int ObjectIdx) const {
376 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
377 "Invalid Object Idx!");
378 return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
381 /// getObjectSize - Return the size of the specified object.
383 int64_t getObjectSize(int ObjectIdx) const {
384 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
385 "Invalid Object Idx!");
386 return Objects[ObjectIdx+NumFixedObjects].Size;
389 /// setObjectSize - Change the size of the specified stack object.
390 void setObjectSize(int ObjectIdx, int64_t Size) {
391 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
392 "Invalid Object Idx!");
393 Objects[ObjectIdx+NumFixedObjects].Size = Size;
396 /// getObjectAlignment - Return the alignment of the specified stack object.
397 unsigned getObjectAlignment(int ObjectIdx) const {
398 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
399 "Invalid Object Idx!");
400 return Objects[ObjectIdx+NumFixedObjects].Alignment;
403 /// setObjectAlignment - Change the alignment of the specified stack object.
404 void setObjectAlignment(int ObjectIdx, unsigned Align) {
405 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
406 "Invalid Object Idx!");
407 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
408 ensureMaxAlignment(Align);
411 /// getObjectAllocation - Return the underlying Alloca of the specified
412 /// stack object if it exists. Returns 0 if none exists.
413 const AllocaInst* getObjectAllocation(int ObjectIdx) const {
414 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
415 "Invalid Object Idx!");
416 return Objects[ObjectIdx+NumFixedObjects].Alloca;
419 /// getObjectOffset - Return the assigned stack offset of the specified object
420 /// from the incoming stack pointer.
422 int64_t getObjectOffset(int ObjectIdx) const {
423 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
424 "Invalid Object Idx!");
425 assert(!isDeadObjectIndex(ObjectIdx) &&
426 "Getting frame offset for a dead object?");
427 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
430 /// setObjectOffset - Set the stack frame offset of the specified object. The
431 /// offset is relative to the stack pointer on entry to the function.
433 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
434 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
435 "Invalid Object Idx!");
436 assert(!isDeadObjectIndex(ObjectIdx) &&
437 "Setting frame offset for a dead object?");
438 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
441 /// getStackSize - Return the number of bytes that must be allocated to hold
442 /// all of the fixed size frame objects. This is only valid after
443 /// Prolog/Epilog code insertion has finalized the stack frame layout.
445 uint64_t getStackSize() const { return StackSize; }
447 /// setStackSize - Set the size of the stack...
449 void setStackSize(uint64_t Size) { StackSize = Size; }
451 /// Estimate and return the size of the stack frame.
452 unsigned estimateStackSize(const MachineFunction &MF) const;
454 /// getOffsetAdjustment - Return the correction for frame offsets.
456 int getOffsetAdjustment() const { return OffsetAdjustment; }
458 /// setOffsetAdjustment - Set the correction for frame offsets.
460 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
462 /// getMaxAlignment - Return the alignment in bytes that this function must be
463 /// aligned to, which is greater than the default stack alignment provided by
466 unsigned getMaxAlignment() const { return MaxAlignment; }
468 /// ensureMaxAlignment - Make sure the function is at least Align bytes
470 void ensureMaxAlignment(unsigned Align);
472 /// AdjustsStack - Return true if this function adjusts the stack -- e.g.,
473 /// when calling another function. This is only valid during and after
474 /// prolog/epilog code insertion.
475 bool adjustsStack() const { return AdjustsStack; }
476 void setAdjustsStack(bool V) { AdjustsStack = V; }
478 /// hasCalls - Return true if the current function has any function calls.
479 bool hasCalls() const { return HasCalls; }
480 void setHasCalls(bool V) { HasCalls = V; }
482 /// Returns true if the function contains any stack-adjusting inline assembly.
483 bool hasInlineAsmWithSPAdjust() const { return HasInlineAsmWithSPAdjust; }
484 void setHasInlineAsmWithSPAdjust(bool B) { HasInlineAsmWithSPAdjust = B; }
486 /// Returns true if the function calls the llvm.va_start intrinsic.
487 bool hasVAStart() const { return HasVAStart; }
488 void setHasVAStart(bool B) { HasVAStart = B; }
490 /// Returns true if the function is variadic and contains a musttail call.
491 bool hasMustTailInVarArgFunc() const { return HasMustTailInVarArgFunc; }
492 void setHasMustTailInVarArgFunc(bool B) { HasMustTailInVarArgFunc = B; }
494 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
495 /// allocated for an outgoing function call. This is only available if
496 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
497 /// then only during or after prolog/epilog code insertion.
499 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
500 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
502 /// CreateFixedObject - Create a new object at a fixed location on the stack.
503 /// All fixed objects should be created before other objects are created for
504 /// efficiency. By default, fixed objects are not pointed to by LLVM IR
505 /// values. This returns an index with a negative value.
507 int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable,
508 bool isAliased = false);
510 /// CreateFixedSpillStackObject - Create a spill slot at a fixed location
511 /// on the stack. Returns an index with a negative value.
512 int CreateFixedSpillStackObject(uint64_t Size, int64_t SPOffset);
514 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
515 /// fixed stack object.
516 bool isFixedObjectIndex(int ObjectIdx) const {
517 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
520 /// isAliasedObjectIndex - Returns true if the specified index corresponds
521 /// to an object that might be pointed to by an LLVM IR value.
522 bool isAliasedObjectIndex(int ObjectIdx) const {
523 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
524 "Invalid Object Idx!");
525 return Objects[ObjectIdx+NumFixedObjects].isAliased;
528 /// isImmutableObjectIndex - Returns true if the specified index corresponds
529 /// to an immutable object.
530 bool isImmutableObjectIndex(int ObjectIdx) const {
531 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
532 "Invalid Object Idx!");
533 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
536 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
537 /// to a spill slot..
538 bool isSpillSlotObjectIndex(int ObjectIdx) const {
539 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
540 "Invalid Object Idx!");
541 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;
544 /// isDeadObjectIndex - Returns true if the specified index corresponds to
546 bool isDeadObjectIndex(int ObjectIdx) const {
547 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
548 "Invalid Object Idx!");
549 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
552 /// CreateStackObject - Create a new statically sized stack object, returning
553 /// a nonnegative identifier to represent it.
555 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS,
556 const AllocaInst *Alloca = nullptr);
558 /// CreateSpillStackObject - Create a new statically sized stack object that
559 /// represents a spill slot, returning a nonnegative identifier to represent
562 int CreateSpillStackObject(uint64_t Size, unsigned Alignment);
564 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
566 void RemoveStackObject(int ObjectIdx) {
568 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
571 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
572 /// variable sized object has been created. This must be created whenever a
573 /// variable sized object is created, whether or not the index returned is
576 int CreateVariableSizedObject(unsigned Alignment, const AllocaInst *Alloca);
578 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
579 /// current function.
580 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
584 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
585 /// callee saved information.
586 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
590 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
591 bool isCalleeSavedInfoValid() const { return CSIValid; }
593 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
595 /// getPristineRegs - Return a set of physical registers that are pristine on
596 /// entry to the MBB.
598 /// Pristine registers hold a value that is useless to the current function,
599 /// but that must be preserved - they are callee saved registers that have not
602 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
603 /// method always returns an empty set.
604 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
606 /// print - Used by the MachineFunction printer to print information about
607 /// stack objects. Implemented in MachineFunction.cpp
609 void print(const MachineFunction &MF, raw_ostream &OS) const;
611 /// dump - Print the function to stderr.
612 void dump(const MachineFunction &MF) const;
615 } // End llvm namespace