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/Support/DataTypes.h"
24 class TargetRegisterClass;
26 class MachineModuleInfo;
27 class MachineFunction;
28 class TargetFrameInfo;
30 /// The CalleeSavedInfo class tracks the information need to locate where a
31 /// callee saved register in the current frame.
32 class CalleeSavedInfo {
36 const TargetRegisterClass *RegClass;
40 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
47 unsigned getReg() const { return Reg; }
48 const TargetRegisterClass *getRegClass() const { return RegClass; }
49 int getFrameIdx() const { return FrameIdx; }
50 void setFrameIdx(int FI) { FrameIdx = FI; }
53 /// The MachineFrameInfo class represents an abstract stack frame until
54 /// prolog/epilog code is inserted. This class is key to allowing stack frame
55 /// representation optimizations, such as frame pointer elimination. It also
56 /// allows more mundane (but still important) optimizations, such as reordering
57 /// of abstract objects on the stack frame.
59 /// To support this, the class assigns unique integer identifiers to stack
60 /// objects requested clients. These identifiers are negative integers for
61 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
62 /// for objects that may be reordered. Instructions which refer to stack
63 /// objects use a special MO_FrameIndex operand to represent these frame
66 /// Because this class keeps track of all references to the stack frame, it
67 /// knows when a variable sized object is allocated on the stack. This is the
68 /// sole condition which prevents frame pointer elimination, which is an
69 /// important optimization on register-poor architectures. Because original
70 /// variable sized alloca's in the source program are the only source of
71 /// variable sized stack objects, it is safe to decide whether there will be
72 /// any variable sized objects before all stack objects are known (for
73 /// example, register allocator spill code never needs variable sized
76 /// When prolog/epilog code emission is performed, the final stack frame is
77 /// built and the machine instructions are modified to refer to the actual
78 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
81 /// @brief Abstract Stack Frame Information
82 class MachineFrameInfo {
84 // StackObject - Represent a single object allocated on the stack.
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 // SPOffset - The offset of this object from the stack pointer on entry to
99 // the function. This field has no meaning for a variable sized element.
102 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM = false)
103 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {}
106 /// Objects - The list of stack objects allocated...
108 std::vector<StackObject> Objects;
110 /// NumFixedObjects - This contains the number of fixed objects contained on
111 /// the stack. Because fixed objects are stored at a negative index in the
112 /// Objects list, this is also the index to the 0th object in the list.
114 unsigned NumFixedObjects;
116 /// HasVarSizedObjects - This boolean keeps track of whether any variable
117 /// sized objects have been allocated yet.
119 bool HasVarSizedObjects;
121 /// StackSize - The prolog/epilog code inserter calculates the final stack
122 /// offsets for all of the fixed size objects, updating the Objects list
123 /// above. It then updates StackSize to contain the number of bytes that need
124 /// to be allocated on entry to the function.
128 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
129 /// have the actual offset from the stack/frame pointer. The calculation is
130 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
131 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
132 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
134 int OffsetAdjustment;
136 /// MaxAlignment - The prolog/epilog code inserter may process objects
137 /// that require greater alignment than the default alignment the target
138 /// provides. To handle this, MaxAlignment is set to the maximum alignment
139 /// needed by the objects on the current frame. If this is greater than the
140 /// native alignment maintained by the compiler, dynamic alignment code will
143 unsigned MaxAlignment;
145 /// HasCalls - Set to true if this function has any function calls. This is
146 /// only valid during and after prolog/epilog code insertion.
149 /// MaxCallFrameSize - This contains the size of the largest call frame if the
150 /// target uses frame setup/destroy pseudo instructions (as defined in the
151 /// TargetFrameInfo class). This information is important for frame pointer
152 /// elimination. If is only valid during and after prolog/epilog code
155 unsigned MaxCallFrameSize;
157 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
158 /// callee saved register saved in the frame. Beyond its use by the prolog/
159 /// epilog code inserter, this data used for debug info and exception
161 std::vector<CalleeSavedInfo> CSInfo;
163 /// MMI - This field is set (via setMachineModuleInfo) by a module info
164 /// consumer (ex. DwarfWriter) to indicate that frame layout information
165 /// should be acquired. Typically, it's the responsibility of the target's
166 /// TargetRegisterInfo prologue/epilogue emitting code to inform
167 /// MachineModuleInfo of frame layouts.
168 MachineModuleInfo *MMI;
170 /// TargetFrameInfo - Target information about frame layout.
172 const TargetFrameInfo &TFI;
174 MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
175 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
176 HasVarSizedObjects = false;
178 MaxCallFrameSize = 0;
182 /// hasStackObjects - Return true if there are any stack objects in this
185 bool hasStackObjects() const { return !Objects.empty(); }
187 /// hasVarSizedObjects - This method may be called any time after instruction
188 /// selection is complete to determine if the stack frame for this function
189 /// contains any variable sized objects.
191 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
193 /// getObjectIndexBegin - Return the minimum frame object index...
195 int getObjectIndexBegin() const { return -NumFixedObjects; }
197 /// getObjectIndexEnd - Return one past the maximum frame object index...
199 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
201 /// getNumFixedObjects() - Return the number of fixed objects.
202 unsigned getNumFixedObjects() const { return NumFixedObjects; }
204 /// getNumObjects() - Return the number of objects.
206 unsigned getNumObjects() const { return Objects.size(); }
208 /// getObjectSize - Return the size of the specified object
210 int64_t getObjectSize(int ObjectIdx) const {
211 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
212 "Invalid Object Idx!");
213 return Objects[ObjectIdx+NumFixedObjects].Size;
216 // setObjectSize - Change the size of the specified stack object...
217 void setObjectSize(int ObjectIdx, int64_t Size) {
218 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
219 "Invalid Object Idx!");
220 Objects[ObjectIdx+NumFixedObjects].Size = Size;
223 /// getObjectAlignment - Return the alignment of the specified stack object...
224 unsigned getObjectAlignment(int ObjectIdx) const {
225 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
226 "Invalid Object Idx!");
227 return Objects[ObjectIdx+NumFixedObjects].Alignment;
230 /// setObjectAlignment - Change the alignment of the specified stack object...
231 void setObjectAlignment(int ObjectIdx, unsigned Align) {
232 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
233 "Invalid Object Idx!");
234 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
237 /// getObjectOffset - Return the assigned stack offset of the specified object
238 /// from the incoming stack pointer.
240 int64_t getObjectOffset(int ObjectIdx) const {
241 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
242 "Invalid Object Idx!");
243 assert(!isDeadObjectIndex(ObjectIdx) &&
244 "Getting frame offset for a dead object?");
245 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
248 /// setObjectOffset - Set the stack frame offset of the specified object. The
249 /// offset is relative to the stack pointer on entry to the function.
251 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
252 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
253 "Invalid Object Idx!");
254 assert(!isDeadObjectIndex(ObjectIdx) &&
255 "Setting frame offset for a dead object?");
256 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
259 /// getStackSize - Return the number of bytes that must be allocated to hold
260 /// all of the fixed size frame objects. This is only valid after
261 /// Prolog/Epilog code insertion has finalized the stack frame layout.
263 uint64_t getStackSize() const { return StackSize; }
265 /// setStackSize - Set the size of the stack...
267 void setStackSize(uint64_t Size) { StackSize = Size; }
269 /// getOffsetAdjustment - Return the correction for frame offsets.
271 int getOffsetAdjustment() const { return OffsetAdjustment; }
273 /// setOffsetAdjustment - Set the correction for frame offsets.
275 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
277 /// getMaxAlignment - Return the alignment in bytes that this function must be
278 /// aligned to, which is greater than the default stack alignment provided by
281 unsigned getMaxAlignment() const { return MaxAlignment; }
283 /// setMaxAlignment - Set the preferred alignment.
285 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
287 /// hasCalls - Return true if the current function has no function calls.
288 /// This is only valid during or after prolog/epilog code emission.
290 bool hasCalls() const { return HasCalls; }
291 void setHasCalls(bool V) { HasCalls = V; }
293 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
294 /// allocated for an outgoing function call. This is only available if
295 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
296 /// then only during or after prolog/epilog code insertion.
298 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
299 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
301 /// CreateFixedObject - Create a new object at a fixed location on the stack.
302 /// All fixed objects should be created before other objects are created for
303 /// efficiency. By default, fixed objects are immutable. This returns an
304 /// index with a negative value.
306 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
307 bool Immutable = true);
310 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
311 /// fixed stack object.
312 bool isFixedObjectIndex(int ObjectIdx) const {
313 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
316 /// isImmutableObjectIndex - Returns true if the specified index corresponds
317 /// to an immutable object.
318 bool isImmutableObjectIndex(int ObjectIdx) const {
319 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
320 "Invalid Object Idx!");
321 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
324 /// isDeadObjectIndex - Returns true if the specified index corresponds to
326 bool isDeadObjectIndex(int ObjectIdx) const {
327 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
328 "Invalid Object Idx!");
329 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
332 /// CreateStackObject - Create a new statically sized stack object, returning
333 /// a nonnegative identifier to represent it.
335 int CreateStackObject(uint64_t Size, unsigned Alignment) {
336 assert(Size != 0 && "Cannot allocate zero size stack objects!");
337 Objects.push_back(StackObject(Size, Alignment, -1));
338 return (int)Objects.size()-NumFixedObjects-1;
341 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
343 void RemoveStackObject(int ObjectIdx) {
345 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
348 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
349 /// variable sized object has been created. This must be created whenever a
350 /// variable sized object is created, whether or not the index returned is
353 int CreateVariableSizedObject() {
354 HasVarSizedObjects = true;
355 Objects.push_back(StackObject(0, 1, -1));
356 return (int)Objects.size()-NumFixedObjects-1;
359 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
360 /// current function.
361 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
365 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
366 /// callee saved information.
367 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
371 /// getMachineModuleInfo - Used by a prologue/epilogue
372 /// emitter (TargetRegisterInfo) to provide frame layout information.
373 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
375 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
376 /// indicate that frame layout information should be gathered.
377 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
379 /// print - Used by the MachineFunction printer to print information about
380 /// stack objects. Implemented in MachineFunction.cpp
382 void print(const MachineFunction &MF, std::ostream &OS) const;
384 /// dump - Call print(MF, std::cerr) to be called from the debugger.
385 void dump(const MachineFunction &MF) const;
388 } // End llvm namespace