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 //===----------------------------------------------------------------------===//
11 #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H
12 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
18 class TargetRegisterClass;
20 class MachineModuleInfo;
21 class MachineFunction;
23 /// The CalleeSavedInfo class tracks the information need to locate where a
24 /// callee saved register in the current frame.
25 class CalleeSavedInfo {
29 const TargetRegisterClass *RegClass;
33 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
40 unsigned getReg() const { return Reg; }
41 const TargetRegisterClass *getRegClass() const { return RegClass; }
42 int getFrameIdx() const { return FrameIdx; }
43 void setFrameIdx(int FI) { FrameIdx = FI; }
46 /// The MachineFrameInfo class represents an abstract stack frame until
47 /// prolog/epilog code is inserted. This class is key to allowing stack frame
48 /// representation optimizations, such as frame pointer elimination. It also
49 /// allows more mundane (but still important) optimizations, such as reordering
50 /// of abstract objects on the stack frame.
52 /// To support this, the class assigns unique integer identifiers to stack
53 /// objects requested clients. These identifiers are negative integers for
54 /// fixed stack objects (such as arguments passed on the stack) or positive
55 /// for objects that may be reordered. Instructions which refer to stack
56 /// objects use a special MO_FrameIndex operand to represent these frame
59 /// Because this class keeps track of all references to the stack frame, it
60 /// knows when a variable sized object is allocated on the stack. This is the
61 /// sole condition which prevents frame pointer elimination, which is an
62 /// important optimization on register-poor architectures. Because original
63 /// variable sized alloca's in the source program are the only source of
64 /// variable sized stack objects, it is safe to decide whether there will be
65 /// any variable sized objects before all stack objects are known (for
66 /// example, register allocator spill code never needs variable sized
69 /// When prolog/epilog code emission is performed, the final stack frame is
70 /// built and the machine instructions are modified to refer to the actual
71 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
74 /// @brief Abstract Stack Frame Information
75 class MachineFrameInfo {
77 // StackObject - Represent a single object allocated on the stack.
79 // The size of this object on the stack. 0 means a variable sized object
82 // Alignment - The required alignment of this stack slot.
85 // SPOffset - The offset of this object from the stack pointer on entry to
86 // the function. This field has no meaning for a variable sized element.
89 // isImmutable - If true, the value of the stack object is set before
90 // entering the function and is not modified inside the function. By
91 // default, fixed objects are immutable unless marked otherwise.
94 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM = false)
95 : Size(Sz), Alignment(Al), SPOffset(SP), isImmutable(IM) {}
98 /// Objects - The list of stack objects allocated...
100 std::vector<StackObject> Objects;
102 /// NumFixedObjects - This contains the number of fixed objects contained on
103 /// the stack. Because fixed objects are stored at a negative index in the
104 /// Objects list, this is also the index to the 0th object in the list.
106 unsigned NumFixedObjects;
108 /// HasVarSizedObjects - This boolean keeps track of whether any variable
109 /// sized objects have been allocated yet.
111 bool HasVarSizedObjects;
113 /// StackSize - The prolog/epilog code inserter calculates the final stack
114 /// offsets for all of the fixed size objects, updating the Objects list
115 /// above. It then updates StackSize to contain the number of bytes that need
116 /// to be allocated on entry to the function.
120 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
121 /// have the actual offset from the stack/frame pointer. The calculation is
122 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
123 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
124 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
126 int OffsetAdjustment;
128 /// MaxAlignment - The prolog/epilog code inserter may process objects
129 /// that require greater alignment than the default alignment the target
130 /// provides. To handle this, MaxAlignment is set to the maximum alignment
131 /// needed by the objects on the current frame. If this is greater than the
132 /// native alignment maintained by the compiler, dynamic alignment code will
135 unsigned MaxAlignment;
137 /// HasCalls - Set to true if this function has any function calls. This is
138 /// only valid during and after prolog/epilog code insertion.
141 /// MaxCallFrameSize - This contains the size of the largest call frame if the
142 /// target uses frame setup/destroy pseudo instructions (as defined in the
143 /// TargetFrameInfo class). This information is important for frame pointer
144 /// elimination. If is only valid during and after prolog/epilog code
147 unsigned MaxCallFrameSize;
149 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
150 /// callee saved register saved in the frame. Beyond its use by the prolog/
151 /// epilog code inserter, this data used for debug info and exception
153 std::vector<CalleeSavedInfo> CSInfo;
155 /// MMI - This field is set (via setMachineModuleInfo) by a module info
156 /// consumer (ex. DwarfWriter) to indicate that frame layout information
157 /// should be acquired. Typically, it's the responsibility of the target's
158 /// MRegisterInfo prologue/epilogue emitting code to inform MachineModuleInfo
159 /// of frame layouts.
160 MachineModuleInfo *MMI;
164 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
165 HasVarSizedObjects = false;
167 MaxCallFrameSize = 0;
171 /// hasStackObjects - Return true if there are any stack objects in this
174 bool hasStackObjects() const { return !Objects.empty(); }
176 /// hasVarSizedObjects - This method may be called any time after instruction
177 /// selection is complete to determine if the stack frame for this function
178 /// contains any variable sized objects.
180 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
182 /// getObjectIndexBegin - Return the minimum frame object index...
184 int getObjectIndexBegin() const { return -NumFixedObjects; }
186 /// getObjectIndexEnd - Return one past the maximum frame object index...
188 int getObjectIndexEnd() const { return Objects.size()-NumFixedObjects; }
190 /// getObjectSize - Return the size of the specified object
192 int64_t getObjectSize(int ObjectIdx) const {
193 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
194 return Objects[ObjectIdx+NumFixedObjects].Size;
197 /// getObjectAlignment - Return the alignment of the specified stack object...
198 int getObjectAlignment(int ObjectIdx) const {
199 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
200 return Objects[ObjectIdx+NumFixedObjects].Alignment;
203 /// getObjectOffset - Return the assigned stack offset of the specified object
204 /// from the incoming stack pointer.
206 int64_t getObjectOffset(int ObjectIdx) const {
207 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
208 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
211 /// setObjectOffset - Set the stack frame offset of the specified object. The
212 /// offset is relative to the stack pointer on entry to the function.
214 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
215 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
216 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
219 /// getStackSize - Return the number of bytes that must be allocated to hold
220 /// all of the fixed size frame objects. This is only valid after
221 /// Prolog/Epilog code insertion has finalized the stack frame layout.
223 uint64_t getStackSize() const { return StackSize; }
225 /// setStackSize - Set the size of the stack...
227 void setStackSize(uint64_t Size) { StackSize = Size; }
229 /// getOffsetAdjustment - Return the correction for frame offsets.
231 int getOffsetAdjustment() const { return OffsetAdjustment; }
233 /// setOffsetAdjustment - Set the correction for frame offsets.
235 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
237 /// getMaxAlignment - Return the alignment in bytes that this function must be
238 /// aligned to, which is greater than the default stack alignment provided by
241 unsigned getMaxAlignment() const { return MaxAlignment; }
243 /// setMaxAlignment - Set the preferred alignment.
245 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
247 /// hasCalls - Return true if the current function has no function calls.
248 /// This is only valid during or after prolog/epilog code emission.
250 bool hasCalls() const { return HasCalls; }
251 void setHasCalls(bool V) { HasCalls = V; }
253 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
254 /// allocated for an outgoing function call. This is only available if
255 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
256 /// then only during or after prolog/epilog code insertion.
258 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
259 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
261 /// CreateFixedObject - Create a new object at a fixed location on the stack.
262 /// All fixed objects should be created before other objects are created for
263 /// efficiency. By default, fixed objects are immutable. This returns an
264 /// index with a negative value.
266 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
267 bool Immutable = true) {
268 assert(Size != 0 && "Cannot allocate zero size fixed stack objects!");
269 Objects.insert(Objects.begin(), StackObject(Size, 1, SPOffset, Immutable));
270 return -++NumFixedObjects;
273 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
274 /// fixed stack object.
275 bool isFixedObjectIndex(int ObjectIdx) const {
276 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
279 /// isImmutableObjectIndex - Returns true if the specified index corresponds
280 /// to an immutable object.
281 bool isImmutableObjectIndex(int ObjectIdx) const {
282 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
285 /// CreateStackObject - Create a new statically sized stack object, returning
286 /// a postive identifier to represent it.
288 int CreateStackObject(uint64_t Size, unsigned Alignment) {
289 // Keep track of the maximum alignment.
290 if (MaxAlignment < Alignment) MaxAlignment = Alignment;
292 assert(Size != 0 && "Cannot allocate zero size stack objects!");
293 Objects.push_back(StackObject(Size, Alignment, -1));
294 return Objects.size()-NumFixedObjects-1;
297 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
298 /// variable sized object has been created. This must be created whenever a
299 /// variable sized object is created, whether or not the index returned is
302 int CreateVariableSizedObject() {
303 HasVarSizedObjects = true;
304 if (MaxAlignment < 1) MaxAlignment = 1;
305 Objects.push_back(StackObject(0, 1, -1));
306 return Objects.size()-NumFixedObjects-1;
309 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
310 /// current function.
311 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
315 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
316 /// callee saved information.
317 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
321 /// getMachineModuleInfo - Used by a prologue/epilogue emitter (MRegisterInfo)
322 /// to provide frame layout information.
323 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
325 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
326 /// indicate that frame layout information should be gathered.
327 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
329 /// print - Used by the MachineFunction printer to print information about
330 /// stack objects. Implemented in MachineFunction.cpp
332 void print(const MachineFunction &MF, std::ostream &OS) const;
334 /// dump - Call print(MF, std::cerr) to be called from the debugger.
335 void dump(const MachineFunction &MF) const;
338 } // End llvm namespace