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/System/DataTypes.h"
25 class TargetRegisterClass;
27 class MachineFunction;
28 class MachineBasicBlock;
29 class TargetFrameInfo;
32 /// The CalleeSavedInfo class tracks the information need to locate where a
33 /// callee saved register in the current frame.
34 class CalleeSavedInfo {
36 const TargetRegisterClass *RegClass;
40 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
41 : Reg(R), RegClass(RC), FrameIdx(FI) {}
44 unsigned getReg() const { return Reg; }
45 const TargetRegisterClass *getRegClass() const { return RegClass; }
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 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
105 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
109 /// Objects - The list of stack objects allocated...
111 std::vector<StackObject> Objects;
113 /// NumFixedObjects - This contains the number of fixed objects contained on
114 /// the stack. Because fixed objects are stored at a negative index in the
115 /// Objects list, this is also the index to the 0th object in the list.
117 unsigned NumFixedObjects;
119 /// HasVarSizedObjects - This boolean keeps track of whether any variable
120 /// sized objects have been allocated yet.
122 bool HasVarSizedObjects;
124 /// FrameAddressTaken - This boolean keeps track of whether there is a call
125 /// to builtin \@llvm.frameaddress.
126 bool FrameAddressTaken;
128 /// StackSize - The prolog/epilog code inserter calculates the final stack
129 /// offsets for all of the fixed size objects, updating the Objects list
130 /// above. It then updates StackSize to contain the number of bytes that need
131 /// to be allocated on entry to the function.
135 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
136 /// have the actual offset from the stack/frame pointer. The exact usage of
137 /// this is target-dependent, but it is typically used to adjust between
138 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
139 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
140 /// to the distance between the initial SP and the value in FP. For many
141 /// targets, this value is only used when generating debug info (via
142 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
143 /// corresponding adjustments are performed directly.
144 int OffsetAdjustment;
146 /// MaxAlignment - The prolog/epilog code inserter may process objects
147 /// that require greater alignment than the default alignment the target
148 /// provides. To handle this, MaxAlignment is set to the maximum alignment
149 /// needed by the objects on the current frame. If this is greater than the
150 /// native alignment maintained by the compiler, dynamic alignment code will
153 unsigned MaxAlignment;
155 /// HasCalls - Set to true if this function has any function calls. This is
156 /// only valid during and after prolog/epilog code insertion.
159 /// StackProtectorIdx - The frame index for the stack protector.
160 int StackProtectorIdx;
162 /// MaxCallFrameSize - This contains the size of the largest call frame if the
163 /// target uses frame setup/destroy pseudo instructions (as defined in the
164 /// TargetFrameInfo class). This information is important for frame pointer
165 /// elimination. If is only valid during and after prolog/epilog code
168 unsigned MaxCallFrameSize;
170 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
171 /// callee saved register saved in the frame. Beyond its use by the prolog/
172 /// epilog code inserter, this data used for debug info and exception
174 std::vector<CalleeSavedInfo> CSInfo;
176 /// CSIValid - Has CSInfo been set yet?
179 /// SpillObjects - A vector indicating which frame indices refer to
181 SmallVector<bool, 8> SpillObjects;
183 /// TargetFrameInfo - Target information about frame layout.
185 const TargetFrameInfo &TFI;
188 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
189 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
190 HasVarSizedObjects = false;
191 FrameAddressTaken = false;
193 StackProtectorIdx = -1;
194 MaxCallFrameSize = 0;
198 /// hasStackObjects - Return true if there are any stack objects in this
201 bool hasStackObjects() const { return !Objects.empty(); }
203 /// hasVarSizedObjects - This method may be called any time after instruction
204 /// selection is complete to determine if the stack frame for this function
205 /// contains any variable sized objects.
207 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
209 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
210 /// stack protector object.
212 int getStackProtectorIndex() const { return StackProtectorIdx; }
213 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
215 /// isFrameAddressTaken - This method may be called any time after instruction
216 /// selection is complete to determine if there is a call to
217 /// \@llvm.frameaddress in this function.
218 bool isFrameAddressTaken() const { return FrameAddressTaken; }
219 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
221 /// getObjectIndexBegin - Return the minimum frame object index.
223 int getObjectIndexBegin() const { return -NumFixedObjects; }
225 /// getObjectIndexEnd - Return one past the maximum frame object index.
227 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
229 /// getNumFixedObjects() - Return the number of fixed objects.
230 unsigned getNumFixedObjects() const { return NumFixedObjects; }
232 /// getNumObjects() - Return the number of objects.
234 unsigned getNumObjects() const { return Objects.size(); }
236 /// getObjectSize - Return the size of the specified object.
238 int64_t getObjectSize(int ObjectIdx) const {
239 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
240 "Invalid Object Idx!");
241 return Objects[ObjectIdx+NumFixedObjects].Size;
244 /// setObjectSize - Change the size of the specified stack object.
245 void setObjectSize(int ObjectIdx, int64_t Size) {
246 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
247 "Invalid Object Idx!");
248 Objects[ObjectIdx+NumFixedObjects].Size = Size;
251 /// getObjectAlignment - Return the alignment of the specified stack object.
252 unsigned getObjectAlignment(int ObjectIdx) const {
253 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
254 "Invalid Object Idx!");
255 return Objects[ObjectIdx+NumFixedObjects].Alignment;
258 /// setObjectAlignment - Change the alignment of the specified stack object.
259 void setObjectAlignment(int ObjectIdx, unsigned Align) {
260 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
261 "Invalid Object Idx!");
262 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
263 MaxAlignment = std::max(MaxAlignment, Align);
266 /// getObjectOffset - Return the assigned stack offset of the specified object
267 /// from the incoming stack pointer.
269 int64_t getObjectOffset(int ObjectIdx) const {
270 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
271 "Invalid Object Idx!");
272 assert(!isDeadObjectIndex(ObjectIdx) &&
273 "Getting frame offset for a dead object?");
274 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
277 /// setObjectOffset - Set the stack frame offset of the specified object. The
278 /// offset is relative to the stack pointer on entry to the function.
280 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
281 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
282 "Invalid Object Idx!");
283 assert(!isDeadObjectIndex(ObjectIdx) &&
284 "Setting frame offset for a dead object?");
285 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
288 /// getStackSize - Return the number of bytes that must be allocated to hold
289 /// all of the fixed size frame objects. This is only valid after
290 /// Prolog/Epilog code insertion has finalized the stack frame layout.
292 uint64_t getStackSize() const { return StackSize; }
294 /// setStackSize - Set the size of the stack...
296 void setStackSize(uint64_t Size) { StackSize = Size; }
298 /// getOffsetAdjustment - Return the correction for frame offsets.
300 int getOffsetAdjustment() const { return OffsetAdjustment; }
302 /// setOffsetAdjustment - Set the correction for frame offsets.
304 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
306 /// getMaxAlignment - Return the alignment in bytes that this function must be
307 /// aligned to, which is greater than the default stack alignment provided by
310 unsigned getMaxAlignment() const { return MaxAlignment; }
312 /// setMaxAlignment - Set the preferred alignment.
314 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
316 /// hasCalls - Return true if the current function has no function calls.
317 /// This is only valid during or after prolog/epilog code emission.
319 bool hasCalls() const { return HasCalls; }
320 void setHasCalls(bool V) { HasCalls = V; }
322 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
323 /// allocated for an outgoing function call. This is only available if
324 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
325 /// then only during or after prolog/epilog code insertion.
327 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
328 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
330 /// CreateFixedObject - Create a new object at a fixed location on the stack.
331 /// All fixed objects should be created before other objects are created for
332 /// efficiency. By default, fixed objects are immutable. This returns an
333 /// index with a negative value.
335 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
336 bool Immutable, bool isSS);
339 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
340 /// fixed stack object.
341 bool isFixedObjectIndex(int ObjectIdx) const {
342 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
345 /// isImmutableObjectIndex - Returns true if the specified index corresponds
346 /// to an immutable object.
347 bool isImmutableObjectIndex(int ObjectIdx) const {
348 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
349 "Invalid Object Idx!");
350 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
353 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
354 /// to a spill slot..
355 bool isSpillSlotObjectIndex(int ObjectIdx) const {
356 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
357 "Invalid Object Idx!");
358 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;;
361 /// isDeadObjectIndex - Returns true if the specified index corresponds to
363 bool isDeadObjectIndex(int ObjectIdx) const {
364 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
365 "Invalid Object Idx!");
366 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
369 /// CreateStackObject - Create a new statically sized stack object,
370 /// returning a nonnegative identifier to represent it.
372 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS) {
373 assert(Size != 0 && "Cannot allocate zero size stack objects!");
374 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS));
375 int Index = (int)Objects.size()-NumFixedObjects-1;
376 assert(Index >= 0 && "Bad frame index!");
377 MaxAlignment = std::max(MaxAlignment, Alignment);
381 /// CreateSpillStackObject - Create a new statically sized stack
382 /// object that represents a spill slot, returning a nonnegative
383 /// identifier to represent it.
385 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
386 CreateStackObject(Size, Alignment, true);
387 int Index = (int)Objects.size()-NumFixedObjects-1;
388 MaxAlignment = std::max(MaxAlignment, Alignment);
392 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
394 void RemoveStackObject(int ObjectIdx) {
396 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
399 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
400 /// variable sized object has been created. This must be created whenever a
401 /// variable sized object is created, whether or not the index returned is
404 int CreateVariableSizedObject() {
405 HasVarSizedObjects = true;
406 Objects.push_back(StackObject(0, 1, 0, false, false));
407 return (int)Objects.size()-NumFixedObjects-1;
410 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
411 /// current function.
412 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
416 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
417 /// callee saved information.
418 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
422 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
423 bool isCalleeSavedInfoValid() const { return CSIValid; }
425 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
427 /// getPristineRegs - Return a set of physical registers that are pristine on
428 /// entry to the MBB.
430 /// Pristine registers hold a value that is useless to the current function,
431 /// but that must be preserved - they are callee saved registers that have not
434 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
435 /// method always returns an empty set.
436 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
438 /// print - Used by the MachineFunction printer to print information about
439 /// stack objects. Implemented in MachineFunction.cpp
441 void print(const MachineFunction &MF, raw_ostream &OS) const;
443 /// dump - Print the function to stderr.
444 void dump(const MachineFunction &MF) const;
447 } // End llvm namespace