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;
22 class TargetFrameInfo;
24 /// The CalleeSavedInfo class tracks the information need to locate where a
25 /// callee saved register in the current frame.
26 class CalleeSavedInfo {
30 const TargetRegisterClass *RegClass;
34 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
41 unsigned getReg() const { return Reg; }
42 const TargetRegisterClass *getRegClass() const { return RegClass; }
43 int getFrameIdx() const { return FrameIdx; }
44 void setFrameIdx(int FI) { FrameIdx = FI; }
47 /// The MachineFrameInfo class represents an abstract stack frame until
48 /// prolog/epilog code is inserted. This class is key to allowing stack frame
49 /// representation optimizations, such as frame pointer elimination. It also
50 /// allows more mundane (but still important) optimizations, such as reordering
51 /// of abstract objects on the stack frame.
53 /// To support this, the class assigns unique integer identifiers to stack
54 /// objects requested clients. These identifiers are negative integers for
55 /// fixed stack objects (such as arguments passed on the stack) or positive
56 /// for objects that may be reordered. Instructions which refer to stack
57 /// objects use a special MO_FrameIndex operand to represent these frame
60 /// Because this class keeps track of all references to the stack frame, it
61 /// knows when a variable sized object is allocated on the stack. This is the
62 /// sole condition which prevents frame pointer elimination, which is an
63 /// important optimization on register-poor architectures. Because original
64 /// variable sized alloca's in the source program are the only source of
65 /// variable sized stack objects, it is safe to decide whether there will be
66 /// any variable sized objects before all stack objects are known (for
67 /// example, register allocator spill code never needs variable sized
70 /// When prolog/epilog code emission is performed, the final stack frame is
71 /// built and the machine instructions are modified to refer to the actual
72 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
75 /// @brief Abstract Stack Frame Information
76 class MachineFrameInfo {
78 // StackObject - Represent a single object allocated on the stack.
80 // The size of this object on the stack. 0 means a variable sized object
83 // Alignment - The required alignment of this stack slot.
86 // SPOffset - The offset of this object from the stack pointer on entry to
87 // the function. This field has no meaning for a variable sized element.
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 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM = false)
96 : Size(Sz), Alignment(Al), SPOffset(SP), isImmutable(IM) {}
99 /// Objects - The list of stack objects allocated...
101 std::vector<StackObject> Objects;
103 /// NumFixedObjects - This contains the number of fixed objects contained on
104 /// the stack. Because fixed objects are stored at a negative index in the
105 /// Objects list, this is also the index to the 0th object in the list.
107 unsigned NumFixedObjects;
109 /// HasVarSizedObjects - This boolean keeps track of whether any variable
110 /// sized objects have been allocated yet.
112 bool HasVarSizedObjects;
114 /// StackSize - The prolog/epilog code inserter calculates the final stack
115 /// offsets for all of the fixed size objects, updating the Objects list
116 /// above. It then updates StackSize to contain the number of bytes that need
117 /// to be allocated on entry to the function.
121 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
122 /// have the actual offset from the stack/frame pointer. The calculation is
123 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
124 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
125 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
127 int OffsetAdjustment;
129 /// MaxAlignment - The prolog/epilog code inserter may process objects
130 /// that require greater alignment than the default alignment the target
131 /// provides. To handle this, MaxAlignment is set to the maximum alignment
132 /// needed by the objects on the current frame. If this is greater than the
133 /// native alignment maintained by the compiler, dynamic alignment code will
136 unsigned MaxAlignment;
138 /// HasCalls - Set to true if this function has any function calls. This is
139 /// only valid during and after prolog/epilog code insertion.
142 /// MaxCallFrameSize - This contains the size of the largest call frame if the
143 /// target uses frame setup/destroy pseudo instructions (as defined in the
144 /// TargetFrameInfo class). This information is important for frame pointer
145 /// elimination. If is only valid during and after prolog/epilog code
148 unsigned MaxCallFrameSize;
150 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
151 /// callee saved register saved in the frame. Beyond its use by the prolog/
152 /// epilog code inserter, this data used for debug info and exception
154 std::vector<CalleeSavedInfo> CSInfo;
156 /// MMI - This field is set (via setMachineModuleInfo) by a module info
157 /// consumer (ex. DwarfWriter) to indicate that frame layout information
158 /// should be acquired. Typically, it's the responsibility of the target's
159 /// MRegisterInfo prologue/epilogue emitting code to inform MachineModuleInfo
160 /// of frame layouts.
161 MachineModuleInfo *MMI;
163 /// TargetFrameInfo - Target information about frame layout.
165 const TargetFrameInfo &TFI;
167 MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
168 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
169 HasVarSizedObjects = false;
171 MaxCallFrameSize = 0;
175 /// hasStackObjects - Return true if there are any stack objects in this
178 bool hasStackObjects() const { return !Objects.empty(); }
180 /// hasVarSizedObjects - This method may be called any time after instruction
181 /// selection is complete to determine if the stack frame for this function
182 /// contains any variable sized objects.
184 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
186 /// getObjectIndexBegin - Return the minimum frame object index...
188 int getObjectIndexBegin() const { return -NumFixedObjects; }
190 /// getObjectIndexEnd - Return one past the maximum frame object index...
192 int getObjectIndexEnd() const { return Objects.size()-NumFixedObjects; }
194 /// getObjectSize - Return the size of the specified object
196 int64_t getObjectSize(int ObjectIdx) const {
197 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
198 return Objects[ObjectIdx+NumFixedObjects].Size;
201 /// getObjectAlignment - Return the alignment of the specified stack object...
202 int getObjectAlignment(int ObjectIdx) const {
203 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
204 return Objects[ObjectIdx+NumFixedObjects].Alignment;
207 /// getObjectOffset - Return the assigned stack offset of the specified object
208 /// from the incoming stack pointer.
210 int64_t getObjectOffset(int ObjectIdx) const {
211 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
212 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
215 /// setObjectOffset - Set the stack frame offset of the specified object. The
216 /// offset is relative to the stack pointer on entry to the function.
218 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
219 assert(ObjectIdx+NumFixedObjects < Objects.size() && "Invalid Object Idx!");
220 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
223 /// getStackSize - Return the number of bytes that must be allocated to hold
224 /// all of the fixed size frame objects. This is only valid after
225 /// Prolog/Epilog code insertion has finalized the stack frame layout.
227 uint64_t getStackSize() const { return StackSize; }
229 /// setStackSize - Set the size of the stack...
231 void setStackSize(uint64_t Size) { StackSize = Size; }
233 /// getOffsetAdjustment - Return the correction for frame offsets.
235 int getOffsetAdjustment() const { return OffsetAdjustment; }
237 /// setOffsetAdjustment - Set the correction for frame offsets.
239 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
241 /// getMaxAlignment - Return the alignment in bytes that this function must be
242 /// aligned to, which is greater than the default stack alignment provided by
245 unsigned getMaxAlignment() const { return MaxAlignment; }
247 /// setMaxAlignment - Set the preferred alignment.
249 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
251 /// hasCalls - Return true if the current function has no function calls.
252 /// This is only valid during or after prolog/epilog code emission.
254 bool hasCalls() const { return HasCalls; }
255 void setHasCalls(bool V) { HasCalls = V; }
257 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
258 /// allocated for an outgoing function call. This is only available if
259 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
260 /// then only during or after prolog/epilog code insertion.
262 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
263 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
265 /// CreateFixedObject - Create a new object at a fixed location on the stack.
266 /// All fixed objects should be created before other objects are created for
267 /// efficiency. By default, fixed objects are immutable. This returns an
268 /// index with a negative value.
270 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
271 bool Immutable = true);
274 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
275 /// fixed stack object.
276 bool isFixedObjectIndex(int ObjectIdx) const {
277 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
280 /// isImmutableObjectIndex - Returns true if the specified index corresponds
281 /// to an immutable object.
282 bool isImmutableObjectIndex(int ObjectIdx) const {
283 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
286 /// CreateStackObject - Create a new statically sized stack object, returning
287 /// a postive identifier to represent it.
289 int CreateStackObject(uint64_t Size, unsigned Alignment) {
290 // Keep track of the maximum alignment.
291 if (MaxAlignment < Alignment) MaxAlignment = Alignment;
293 assert(Size != 0 && "Cannot allocate zero size stack objects!");
294 Objects.push_back(StackObject(Size, Alignment, -1));
295 return Objects.size()-NumFixedObjects-1;
298 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
299 /// variable sized object has been created. This must be created whenever a
300 /// variable sized object is created, whether or not the index returned is
303 int CreateVariableSizedObject() {
304 HasVarSizedObjects = true;
305 if (MaxAlignment < 1) MaxAlignment = 1;
306 Objects.push_back(StackObject(0, 1, -1));
307 return Objects.size()-NumFixedObjects-1;
310 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
311 /// current function.
312 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
316 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
317 /// callee saved information.
318 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
322 /// getMachineModuleInfo - Used by a prologue/epilogue emitter (MRegisterInfo)
323 /// to provide frame layout information.
324 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
326 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
327 /// indicate that frame layout information should be gathered.
328 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
330 /// print - Used by the MachineFunction printer to print information about
331 /// stack objects. Implemented in MachineFunction.cpp
333 void print(const MachineFunction &MF, std::ostream &OS) const;
335 /// dump - Call print(MF, std::cerr) to be called from the debugger.
336 void dump(const MachineFunction &MF) const;
339 } // End llvm namespace