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
21 class TargetRegisterClass;
23 class MachineModuleInfo;
24 class MachineFunction;
25 class TargetFrameInfo;
27 /// The CalleeSavedInfo class tracks the information need to locate where a
28 /// callee saved register in the current frame.
29 class CalleeSavedInfo {
33 const TargetRegisterClass *RegClass;
37 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
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 positive
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 // The size of this object on the stack. 0 means a variable sized object,
84 // ~0ULL means a dead object.
87 // Alignment - The required alignment of this stack slot.
90 // isImmutable - If true, the value of the stack object is set before
91 // entering the function and is not modified inside the function. By
92 // default, fixed objects are immutable unless marked otherwise.
95 // SPOffset - The offset of this object from the stack pointer on entry to
96 // the function. This field has no meaning for a variable sized element.
99 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM = false)
100 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {}
103 /// Objects - The list of stack objects allocated...
105 std::vector<StackObject> Objects;
107 /// NumFixedObjects - This contains the number of fixed objects contained on
108 /// the stack. Because fixed objects are stored at a negative index in the
109 /// Objects list, this is also the index to the 0th object in the list.
111 unsigned NumFixedObjects;
113 /// HasVarSizedObjects - This boolean keeps track of whether any variable
114 /// sized objects have been allocated yet.
116 bool HasVarSizedObjects;
118 /// StackSize - The prolog/epilog code inserter calculates the final stack
119 /// offsets for all of the fixed size objects, updating the Objects list
120 /// above. It then updates StackSize to contain the number of bytes that need
121 /// to be allocated on entry to the function.
125 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
126 /// have the actual offset from the stack/frame pointer. The calculation is
127 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
128 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
129 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
131 int OffsetAdjustment;
133 /// MaxAlignment - The prolog/epilog code inserter may process objects
134 /// that require greater alignment than the default alignment the target
135 /// provides. To handle this, MaxAlignment is set to the maximum alignment
136 /// needed by the objects on the current frame. If this is greater than the
137 /// native alignment maintained by the compiler, dynamic alignment code will
140 unsigned MaxAlignment;
142 /// HasCalls - Set to true if this function has any function calls. This is
143 /// only valid during and after prolog/epilog code insertion.
146 /// MaxCallFrameSize - This contains the size of the largest call frame if the
147 /// target uses frame setup/destroy pseudo instructions (as defined in the
148 /// TargetFrameInfo class). This information is important for frame pointer
149 /// elimination. If is only valid during and after prolog/epilog code
152 unsigned MaxCallFrameSize;
154 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
155 /// callee saved register saved in the frame. Beyond its use by the prolog/
156 /// epilog code inserter, this data used for debug info and exception
158 std::vector<CalleeSavedInfo> CSInfo;
160 /// MMI - This field is set (via setMachineModuleInfo) by a module info
161 /// consumer (ex. DwarfWriter) to indicate that frame layout information
162 /// should be acquired. Typically, it's the responsibility of the target's
163 /// TargetRegisterInfo prologue/epilogue emitting code to inform
164 /// MachineModuleInfo of frame layouts.
165 MachineModuleInfo *MMI;
167 /// TargetFrameInfo - Target information about frame layout.
169 const TargetFrameInfo &TFI;
171 MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
172 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
173 HasVarSizedObjects = false;
175 MaxCallFrameSize = 0;
179 /// hasStackObjects - Return true if there are any stack objects in this
182 bool hasStackObjects() const { return !Objects.empty(); }
184 /// hasVarSizedObjects - This method may be called any time after instruction
185 /// selection is complete to determine if the stack frame for this function
186 /// contains any variable sized objects.
188 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
190 /// getObjectIndexBegin - Return the minimum frame object index...
192 int getObjectIndexBegin() const { return -NumFixedObjects; }
194 /// getObjectIndexEnd - Return one past the maximum frame object index...
196 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
198 /// getObjectSize - Return the size of the specified object
200 int64_t getObjectSize(int ObjectIdx) const {
201 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
202 "Invalid Object Idx!");
203 return Objects[ObjectIdx+NumFixedObjects].Size;
206 /// getObjectAlignment - Return the alignment of the specified stack object...
207 unsigned getObjectAlignment(int ObjectIdx) const {
208 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
209 "Invalid Object Idx!");
210 return Objects[ObjectIdx+NumFixedObjects].Alignment;
213 /// setObjectAlignment - Change the alignment of the specified stack object...
214 void setObjectAlignment(int ObjectIdx, unsigned Align) {
215 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
216 "Invalid Object Idx!");
217 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
220 /// getObjectOffset - Return the assigned stack offset of the specified object
221 /// from the incoming stack pointer.
223 int64_t getObjectOffset(int ObjectIdx) const {
224 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
225 "Invalid Object Idx!");
226 assert(!isDeadObjectIndex(ObjectIdx) &&
227 "Getting frame offset for a dead object?");
228 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
231 /// setObjectOffset - Set the stack frame offset of the specified object. The
232 /// offset is relative to the stack pointer on entry to the function.
234 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
235 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
236 "Invalid Object Idx!");
237 assert(!isDeadObjectIndex(ObjectIdx) &&
238 "Setting frame offset for a dead object?");
239 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
242 /// getStackSize - Return the number of bytes that must be allocated to hold
243 /// all of the fixed size frame objects. This is only valid after
244 /// Prolog/Epilog code insertion has finalized the stack frame layout.
246 uint64_t getStackSize() const { return StackSize; }
248 /// setStackSize - Set the size of the stack...
250 void setStackSize(uint64_t Size) { StackSize = Size; }
252 /// getOffsetAdjustment - Return the correction for frame offsets.
254 int getOffsetAdjustment() const { return OffsetAdjustment; }
256 /// setOffsetAdjustment - Set the correction for frame offsets.
258 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
260 /// getMaxAlignment - Return the alignment in bytes that this function must be
261 /// aligned to, which is greater than the default stack alignment provided by
264 unsigned getMaxAlignment() const { return MaxAlignment; }
266 /// setMaxAlignment - Set the preferred alignment.
268 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
270 /// hasCalls - Return true if the current function has no function calls.
271 /// This is only valid during or after prolog/epilog code emission.
273 bool hasCalls() const { return HasCalls; }
274 void setHasCalls(bool V) { HasCalls = V; }
276 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
277 /// allocated for an outgoing function call. This is only available if
278 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
279 /// then only during or after prolog/epilog code insertion.
281 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
282 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
284 /// CreateFixedObject - Create a new object at a fixed location on the stack.
285 /// All fixed objects should be created before other objects are created for
286 /// efficiency. By default, fixed objects are immutable. This returns an
287 /// index with a negative value.
289 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
290 bool Immutable = true);
293 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
294 /// fixed stack object.
295 bool isFixedObjectIndex(int ObjectIdx) const {
296 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
299 /// isImmutableObjectIndex - Returns true if the specified index corresponds
300 /// to an immutable object.
301 bool isImmutableObjectIndex(int ObjectIdx) const {
302 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
303 "Invalid Object Idx!");
304 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
307 /// isDeadObjectIndex - Returns true if the specified index corresponds to
309 bool isDeadObjectIndex(int ObjectIdx) const {
310 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
311 "Invalid Object Idx!");
312 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
315 /// CreateStackObject - Create a new statically sized stack object, returning
316 /// a postive identifier to represent it.
318 int CreateStackObject(uint64_t Size, unsigned Alignment) {
319 assert(Size != 0 && "Cannot allocate zero size stack objects!");
320 Objects.push_back(StackObject(Size, Alignment, -1));
321 return (int)Objects.size()-NumFixedObjects-1;
324 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
326 void RemoveStackObject(int ObjectIdx) {
327 if (ObjectIdx == (int)(Objects.size()-NumFixedObjects-1))
328 // Last object, simply pop it off the list.
332 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
335 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
336 /// variable sized object has been created. This must be created whenever a
337 /// variable sized object is created, whether or not the index returned is
340 int CreateVariableSizedObject() {
341 HasVarSizedObjects = true;
342 Objects.push_back(StackObject(0, 1, -1));
343 return (int)Objects.size()-NumFixedObjects-1;
346 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
347 /// current function.
348 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
352 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
353 /// callee saved information.
354 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
358 /// getMachineModuleInfo - Used by a prologue/epilogue
359 /// emitter (TargetRegisterInfo) to provide frame layout information.
360 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
362 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
363 /// indicate that frame layout information should be gathered.
364 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
366 /// print - Used by the MachineFunction printer to print information about
367 /// stack objects. Implemented in MachineFunction.cpp
369 void print(const MachineFunction &MF, std::ostream &OS) const;
371 /// dump - Call print(MF, std::cerr) to be called from the debugger.
372 void dump(const MachineFunction &MF) const;
375 } // End llvm namespace