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 // SPOffset - The offset of this object from the stack pointer on entry to
90 // the function. This field has no meaning for a variable sized element.
93 // The size of this object on the stack. 0 means a variable sized object,
94 // ~0ULL means a dead object.
97 // Alignment - The required alignment of this stack slot.
100 // isImmutable - If true, the value of the stack object is set before
101 // entering the function and is not modified inside the function. By
102 // default, fixed objects are immutable unless marked otherwise.
105 // isSpillSlot - If true, the stack object is used as spill slot. It
106 // cannot alias any other memory objects.
109 StackObject(uint64_t Sz, unsigned Al, int64_t SP = 0, bool IM = false,
111 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
115 /// Objects - The list of stack objects allocated...
117 std::vector<StackObject> Objects;
119 /// NumFixedObjects - This contains the number of fixed objects contained on
120 /// the stack. Because fixed objects are stored at a negative index in the
121 /// Objects list, this is also the index to the 0th object in the list.
123 unsigned NumFixedObjects;
125 /// HasVarSizedObjects - This boolean keeps track of whether any variable
126 /// sized objects have been allocated yet.
128 bool HasVarSizedObjects;
130 /// FrameAddressTaken - This boolean keeps track of whether there is a call
131 /// to builtin \@llvm.frameaddress.
132 bool FrameAddressTaken;
134 /// StackSize - The prolog/epilog code inserter calculates the final stack
135 /// offsets for all of the fixed size objects, updating the Objects list
136 /// above. It then updates StackSize to contain the number of bytes that need
137 /// to be allocated on entry to the function.
141 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
142 /// have the actual offset from the stack/frame pointer. The exact usage of
143 /// this is target-dependent, but it is typically used to adjust between
144 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
145 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
146 /// to the distance between the initial SP and the value in FP. For many
147 /// targets, this value is only used when generating debug info (via
148 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
149 /// corresponding adjustments are performed directly.
150 int OffsetAdjustment;
152 /// MaxAlignment - The prolog/epilog code inserter may process objects
153 /// that require greater alignment than the default alignment the target
154 /// provides. To handle this, MaxAlignment is set to the maximum alignment
155 /// needed by the objects on the current frame. If this is greater than the
156 /// native alignment maintained by the compiler, dynamic alignment code will
159 unsigned MaxAlignment;
161 /// HasCalls - Set to true if this function has any function calls. This is
162 /// only valid during and after prolog/epilog code insertion.
165 /// StackProtectorIdx - The frame index for the stack protector.
166 int StackProtectorIdx;
168 /// MaxCallFrameSize - This contains the size of the largest call frame if the
169 /// target uses frame setup/destroy pseudo instructions (as defined in the
170 /// TargetFrameInfo class). This information is important for frame pointer
171 /// elimination. If is only valid during and after prolog/epilog code
174 unsigned MaxCallFrameSize;
176 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
177 /// callee saved register saved in the frame. Beyond its use by the prolog/
178 /// epilog code inserter, this data used for debug info and exception
180 std::vector<CalleeSavedInfo> CSInfo;
182 /// CSIValid - Has CSInfo been set yet?
185 /// MMI - This field is set (via setMachineModuleInfo) by a module info
186 /// consumer (ex. DwarfWriter) to indicate that frame layout information
187 /// should be acquired. Typically, it's the responsibility of the target's
188 /// TargetRegisterInfo prologue/epilogue emitting code to inform
189 /// MachineModuleInfo of frame layouts.
190 MachineModuleInfo *MMI;
192 /// TargetFrameInfo - Target information about frame layout.
194 const TargetFrameInfo &TFI;
196 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
197 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
198 HasVarSizedObjects = false;
199 FrameAddressTaken = false;
201 StackProtectorIdx = -1;
202 MaxCallFrameSize = 0;
207 /// hasStackObjects - Return true if there are any stack objects in this
210 bool hasStackObjects() const { return !Objects.empty(); }
212 /// hasVarSizedObjects - This method may be called any time after instruction
213 /// selection is complete to determine if the stack frame for this function
214 /// contains any variable sized objects.
216 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
218 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
219 /// stack protector object.
221 int getStackProtectorIndex() const { return StackProtectorIdx; }
222 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
224 /// isFrameAddressTaken - This method may be called any time after instruction
225 /// selection is complete to determine if there is a call to
226 /// \@llvm.frameaddress in this function.
227 bool isFrameAddressTaken() const { return FrameAddressTaken; }
228 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
230 /// getObjectIndexBegin - Return the minimum frame object index.
232 int getObjectIndexBegin() const { return -NumFixedObjects; }
234 /// getObjectIndexEnd - Return one past the maximum frame object index.
236 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
238 /// getNumFixedObjects() - Return the number of fixed objects.
239 unsigned getNumFixedObjects() const { return NumFixedObjects; }
241 /// getNumObjects() - Return the number of objects.
243 unsigned getNumObjects() const { return Objects.size(); }
245 /// getObjectSize - Return the size of the specified object.
247 int64_t getObjectSize(int ObjectIdx) const {
248 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
249 "Invalid Object Idx!");
250 return Objects[ObjectIdx+NumFixedObjects].Size;
253 /// setObjectSize - Change the size of the specified stack object.
254 void setObjectSize(int ObjectIdx, int64_t Size) {
255 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
256 "Invalid Object Idx!");
257 Objects[ObjectIdx+NumFixedObjects].Size = Size;
260 /// getObjectAlignment - Return the alignment of the specified stack object.
261 unsigned getObjectAlignment(int ObjectIdx) const {
262 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
263 "Invalid Object Idx!");
264 return Objects[ObjectIdx+NumFixedObjects].Alignment;
267 /// setObjectAlignment - Change the alignment of the specified stack object.
268 void setObjectAlignment(int ObjectIdx, unsigned Align) {
269 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
270 "Invalid Object Idx!");
271 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
274 /// getObjectOffset - Return the assigned stack offset of the specified object
275 /// from the incoming stack pointer.
277 int64_t getObjectOffset(int ObjectIdx) const {
278 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
279 "Invalid Object Idx!");
280 assert(!isDeadObjectIndex(ObjectIdx) &&
281 "Getting frame offset for a dead object?");
282 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
285 /// setObjectOffset - Set the stack frame offset of the specified object. The
286 /// offset is relative to the stack pointer on entry to the function.
288 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
289 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
290 "Invalid Object Idx!");
291 assert(!isDeadObjectIndex(ObjectIdx) &&
292 "Setting frame offset for a dead object?");
293 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
296 /// getStackSize - Return the number of bytes that must be allocated to hold
297 /// all of the fixed size frame objects. This is only valid after
298 /// Prolog/Epilog code insertion has finalized the stack frame layout.
300 uint64_t getStackSize() const { return StackSize; }
302 /// setStackSize - Set the size of the stack...
304 void setStackSize(uint64_t Size) { StackSize = Size; }
306 /// getOffsetAdjustment - Return the correction for frame offsets.
308 int getOffsetAdjustment() const { return OffsetAdjustment; }
310 /// setOffsetAdjustment - Set the correction for frame offsets.
312 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
314 /// getMaxAlignment - Return the alignment in bytes that this function must be
315 /// aligned to, which is greater than the default stack alignment provided by
318 unsigned getMaxAlignment() const { return MaxAlignment; }
320 /// setMaxAlignment - Set the preferred alignment.
322 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
324 /// hasCalls - Return true if the current function has no function calls.
325 /// This is only valid during or after prolog/epilog code emission.
327 bool hasCalls() const { return HasCalls; }
328 void setHasCalls(bool V) { HasCalls = V; }
330 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
331 /// allocated for an outgoing function call. This is only available if
332 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
333 /// then only during or after prolog/epilog code insertion.
335 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
336 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
338 /// CreateFixedObject - Create a new object at a fixed location on the stack.
339 /// All fixed objects should be created before other objects are created for
340 /// efficiency. By default, fixed objects are immutable. This returns an
341 /// index with a negative value.
343 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
344 bool Immutable = true);
347 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
348 /// fixed stack object.
349 bool isFixedObjectIndex(int ObjectIdx) const {
350 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
353 /// isImmutableObjectIndex - Returns true if the specified index corresponds
354 /// to an immutable object.
355 bool isImmutableObjectIndex(int ObjectIdx) const {
356 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
357 "Invalid Object Idx!");
358 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
361 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds
362 /// to a spill slot..
363 bool isSpillSlotObjectIndex(int ObjectIdx) const {
364 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
365 "Invalid Object Idx!");
366 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;;
369 /// isDeadObjectIndex - Returns true if the specified index corresponds to
371 bool isDeadObjectIndex(int ObjectIdx) const {
372 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
373 "Invalid Object Idx!");
374 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
377 /// CreateStackObject - Create a new statically sized stack object, returning
378 /// a nonnegative identifier to represent it.
380 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS = false) {
381 assert(Size != 0 && "Cannot allocate zero size stack objects!");
382 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS));
383 return (int)Objects.size()-NumFixedObjects-1;
386 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
388 void RemoveStackObject(int ObjectIdx) {
390 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
393 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
394 /// variable sized object has been created. This must be created whenever a
395 /// variable sized object is created, whether or not the index returned is
398 int CreateVariableSizedObject() {
399 HasVarSizedObjects = true;
400 Objects.push_back(StackObject(0, 1));
401 return (int)Objects.size()-NumFixedObjects-1;
404 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
405 /// current function.
406 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
410 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
411 /// callee saved information.
412 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
416 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
417 bool isCalleeSavedInfoValid() const { return CSIValid; }
419 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
421 /// getPristineRegs - Return a set of physical registers that are pristine on
422 /// entry to the MBB.
424 /// Pristine registers hold a value that is useless to the current function,
425 /// but that must be preserved - they are callee saved registers that have not
428 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
429 /// method always returns an empty set.
430 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
432 /// getMachineModuleInfo - Used by a prologue/epilogue
433 /// emitter (TargetRegisterInfo) to provide frame layout information.
434 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
436 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
437 /// indicate that frame layout information should be gathered.
438 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
440 /// print - Used by the MachineFunction printer to print information about
441 /// stack objects. Implemented in MachineFunction.cpp
443 void print(const MachineFunction &MF, raw_ostream &OS) const;
445 /// dump - Print the function to stderr.
446 void dump(const MachineFunction &MF) const;
449 } // End llvm namespace