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/BitVector.h"
18 #include "llvm/ADT/DenseSet.h"
19 #include "llvm/Support/DataTypes.h"
26 class TargetRegisterClass;
28 class MachineModuleInfo;
29 class MachineFunction;
30 class MachineBasicBlock;
31 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 {
39 const TargetRegisterClass *RegClass;
43 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
50 unsigned getReg() const { return Reg; }
51 const TargetRegisterClass *getRegClass() const { return RegClass; }
52 int getFrameIdx() const { return FrameIdx; }
53 void setFrameIdx(int FI) { FrameIdx = FI; }
56 /// The MachineFrameInfo class represents an abstract stack frame until
57 /// prolog/epilog code is inserted. This class is key to allowing stack frame
58 /// representation optimizations, such as frame pointer elimination. It also
59 /// allows more mundane (but still important) optimizations, such as reordering
60 /// of abstract objects on the stack frame.
62 /// To support this, the class assigns unique integer identifiers to stack
63 /// objects requested clients. These identifiers are negative integers for
64 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
65 /// for objects that may be reordered. Instructions which refer to stack
66 /// objects use a special MO_FrameIndex operand to represent these frame
69 /// Because this class keeps track of all references to the stack frame, it
70 /// knows when a variable sized object is allocated on the stack. This is the
71 /// sole condition which prevents frame pointer elimination, which is an
72 /// important optimization on register-poor architectures. Because original
73 /// variable sized alloca's in the source program are the only source of
74 /// variable sized stack objects, it is safe to decide whether there will be
75 /// any variable sized objects before all stack objects are known (for
76 /// example, register allocator spill code never needs variable sized
79 /// When prolog/epilog code emission is performed, the final stack frame is
80 /// built and the machine instructions are modified to refer to the actual
81 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
84 /// @brief Abstract Stack Frame Information
85 class MachineFrameInfo {
87 // StackObject - Represent a single object allocated on the stack.
89 // The size of this object on the stack. 0 means a variable sized object,
90 // ~0ULL means a dead object.
93 // Alignment - The required alignment of this stack slot.
96 // isImmutable - If true, the value of the stack object is set before
97 // entering the function and is not modified inside the function. By
98 // default, fixed objects are immutable unless marked otherwise.
101 // SPOffset - The offset of this object from the stack pointer on entry to
102 // the function. This field has no meaning for a variable sized element.
105 StackObject(uint64_t Sz, unsigned Al, int64_t SP = 0, bool IM = false)
106 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {}
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 calculation is
137 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
138 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
139 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
141 int OffsetAdjustment;
143 /// MaxAlignment - The prolog/epilog code inserter may process objects
144 /// that require greater alignment than the default alignment the target
145 /// provides. To handle this, MaxAlignment is set to the maximum alignment
146 /// needed by the objects on the current frame. If this is greater than the
147 /// native alignment maintained by the compiler, dynamic alignment code will
150 unsigned MaxAlignment;
152 /// HasCalls - Set to true if this function has any function calls. This is
153 /// only valid during and after prolog/epilog code insertion.
156 /// StackProtectorIdx - The frame index for the stack protector.
157 int StackProtectorIdx;
159 /// MaxCallFrameSize - This contains the size of the largest call frame if the
160 /// target uses frame setup/destroy pseudo instructions (as defined in the
161 /// TargetFrameInfo class). This information is important for frame pointer
162 /// elimination. If is only valid during and after prolog/epilog code
165 unsigned MaxCallFrameSize;
167 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
168 /// callee saved register saved in the frame. Beyond its use by the prolog/
169 /// epilog code inserter, this data used for debug info and exception
171 std::vector<CalleeSavedInfo> CSInfo;
173 /// CSIValid - Has CSInfo been set yet?
176 /// MMI - This field is set (via setMachineModuleInfo) by a module info
177 /// consumer (ex. DwarfWriter) to indicate that frame layout information
178 /// should be acquired. Typically, it's the responsibility of the target's
179 /// TargetRegisterInfo prologue/epilogue emitting code to inform
180 /// MachineModuleInfo of frame layouts.
181 MachineModuleInfo *MMI;
183 /// TargetFrameInfo - Target information about frame layout.
185 const TargetFrameInfo &TFI;
187 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
188 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
189 HasVarSizedObjects = false;
190 FrameAddressTaken = false;
192 StackProtectorIdx = -1;
193 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;
265 /// getObjectOffset - Return the assigned stack offset of the specified object
266 /// from the incoming stack pointer.
268 int64_t getObjectOffset(int ObjectIdx) const {
269 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
270 "Invalid Object Idx!");
271 assert(!isDeadObjectIndex(ObjectIdx) &&
272 "Getting frame offset for a dead object?");
273 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
276 /// setObjectOffset - Set the stack frame offset of the specified object. The
277 /// offset is relative to the stack pointer on entry to the function.
279 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
280 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
281 "Invalid Object Idx!");
282 assert(!isDeadObjectIndex(ObjectIdx) &&
283 "Setting frame offset for a dead object?");
284 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
287 /// getStackSize - Return the number of bytes that must be allocated to hold
288 /// all of the fixed size frame objects. This is only valid after
289 /// Prolog/Epilog code insertion has finalized the stack frame layout.
291 uint64_t getStackSize() const { return StackSize; }
293 /// setStackSize - Set the size of the stack...
295 void setStackSize(uint64_t Size) { StackSize = Size; }
297 /// getOffsetAdjustment - Return the correction for frame offsets.
299 int getOffsetAdjustment() const { return OffsetAdjustment; }
301 /// setOffsetAdjustment - Set the correction for frame offsets.
303 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
305 /// getMaxAlignment - Return the alignment in bytes that this function must be
306 /// aligned to, which is greater than the default stack alignment provided by
309 unsigned getMaxAlignment() const { return MaxAlignment; }
311 /// setMaxAlignment - Set the preferred alignment.
313 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
315 /// hasCalls - Return true if the current function has no function calls.
316 /// This is only valid during or after prolog/epilog code emission.
318 bool hasCalls() const { return HasCalls; }
319 void setHasCalls(bool V) { HasCalls = V; }
321 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
322 /// allocated for an outgoing function call. This is only available if
323 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
324 /// then only during or after prolog/epilog code insertion.
326 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
327 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
329 /// CreateFixedObject - Create a new object at a fixed location on the stack.
330 /// All fixed objects should be created before other objects are created for
331 /// efficiency. By default, fixed objects are immutable. This returns an
332 /// index with a negative value.
334 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
335 bool Immutable = true);
338 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
339 /// fixed stack object.
340 bool isFixedObjectIndex(int ObjectIdx) const {
341 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
344 /// isImmutableObjectIndex - Returns true if the specified index corresponds
345 /// to an immutable object.
346 bool isImmutableObjectIndex(int ObjectIdx) const {
347 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
348 "Invalid Object Idx!");
349 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
352 /// isDeadObjectIndex - Returns true if the specified index corresponds to
354 bool isDeadObjectIndex(int ObjectIdx) const {
355 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
356 "Invalid Object Idx!");
357 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
360 /// CreateStackObject - Create a new statically sized stack object, returning
361 /// a nonnegative identifier to represent it.
363 int CreateStackObject(uint64_t Size, unsigned Alignment) {
364 assert(Size != 0 && "Cannot allocate zero size stack objects!");
365 Objects.push_back(StackObject(Size, Alignment));
366 return (int)Objects.size()-NumFixedObjects-1;
369 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
371 void RemoveStackObject(int ObjectIdx) {
373 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
376 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
377 /// variable sized object has been created. This must be created whenever a
378 /// variable sized object is created, whether or not the index returned is
381 int CreateVariableSizedObject() {
382 HasVarSizedObjects = true;
383 Objects.push_back(StackObject(0, 1));
384 return (int)Objects.size()-NumFixedObjects-1;
387 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
388 /// current function.
389 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
393 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
394 /// callee saved information.
395 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
399 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
400 bool isCalleeSavedInfoValid() const { return CSIValid; }
402 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
404 /// getPristineRegs - Return a set of physical registers that are pristine on
405 /// entry to the MBB.
407 /// Pristine registers hold a value that is useless to the current function,
408 /// but that must be preserved - they are callee saved registers that have not
411 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
412 /// method always returns an empty set.
413 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
415 /// getMachineModuleInfo - Used by a prologue/epilogue
416 /// emitter (TargetRegisterInfo) to provide frame layout information.
417 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
419 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
420 /// indicate that frame layout information should be gathered.
421 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
423 /// print - Used by the MachineFunction printer to print information about
424 /// stack objects. Implemented in MachineFunction.cpp
426 void print(const MachineFunction &MF, raw_ostream &OS) const;
428 /// dump - Print the function to stderr.
429 void dump(const MachineFunction &MF) const;
432 } // End llvm namespace