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
86 // Alignment - The required alignment of this stack slot.
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 // SPOffset - The offset of this object from the stack pointer on entry to
95 // the function. This field has no meaning for a variable sized element.
98 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM = false)
99 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {}
102 /// Objects - The list of stack objects allocated...
104 std::vector<StackObject> Objects;
106 /// NumFixedObjects - This contains the number of fixed objects contained on
107 /// the stack. Because fixed objects are stored at a negative index in the
108 /// Objects list, this is also the index to the 0th object in the list.
110 unsigned NumFixedObjects;
112 /// HasVarSizedObjects - This boolean keeps track of whether any variable
113 /// sized objects have been allocated yet.
115 bool HasVarSizedObjects;
117 /// StackSize - The prolog/epilog code inserter calculates the final stack
118 /// offsets for all of the fixed size objects, updating the Objects list
119 /// above. It then updates StackSize to contain the number of bytes that need
120 /// to be allocated on entry to the function.
124 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
125 /// have the actual offset from the stack/frame pointer. The calculation is
126 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
127 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
128 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
130 int OffsetAdjustment;
132 /// MaxAlignment - The prolog/epilog code inserter may process objects
133 /// that require greater alignment than the default alignment the target
134 /// provides. To handle this, MaxAlignment is set to the maximum alignment
135 /// needed by the objects on the current frame. If this is greater than the
136 /// native alignment maintained by the compiler, dynamic alignment code will
139 unsigned MaxAlignment;
141 /// HasCalls - Set to true if this function has any function calls. This is
142 /// only valid during and after prolog/epilog code insertion.
145 /// MaxCallFrameSize - This contains the size of the largest call frame if the
146 /// target uses frame setup/destroy pseudo instructions (as defined in the
147 /// TargetFrameInfo class). This information is important for frame pointer
148 /// elimination. If is only valid during and after prolog/epilog code
151 unsigned MaxCallFrameSize;
153 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
154 /// callee saved register saved in the frame. Beyond its use by the prolog/
155 /// epilog code inserter, this data used for debug info and exception
157 std::vector<CalleeSavedInfo> CSInfo;
159 /// MMI - This field is set (via setMachineModuleInfo) by a module info
160 /// consumer (ex. DwarfWriter) to indicate that frame layout information
161 /// should be acquired. Typically, it's the responsibility of the target's
162 /// MRegisterInfo prologue/epilogue emitting code to inform MachineModuleInfo
163 /// of frame layouts.
164 MachineModuleInfo *MMI;
166 /// TargetFrameInfo - Target information about frame layout.
168 const TargetFrameInfo &TFI;
170 MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
171 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
172 HasVarSizedObjects = false;
174 MaxCallFrameSize = 0;
178 /// hasStackObjects - Return true if there are any stack objects in this
181 bool hasStackObjects() const { return !Objects.empty(); }
183 /// hasVarSizedObjects - This method may be called any time after instruction
184 /// selection is complete to determine if the stack frame for this function
185 /// contains any variable sized objects.
187 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
189 /// getObjectIndexBegin - Return the minimum frame object index...
191 int getObjectIndexBegin() const { return -NumFixedObjects; }
193 /// getObjectIndexEnd - Return one past the maximum frame object index...
195 int getObjectIndexEnd() const { return Objects.size()-NumFixedObjects; }
197 /// getObjectSize - Return the size of the specified object
199 int64_t getObjectSize(int ObjectIdx) const {
200 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
201 "Invalid Object Idx!");
202 return Objects[ObjectIdx+NumFixedObjects].Size;
205 /// getObjectAlignment - Return the alignment of the specified stack object...
206 int getObjectAlignment(int ObjectIdx) const {
207 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
208 "Invalid Object Idx!");
209 return Objects[ObjectIdx+NumFixedObjects].Alignment;
212 /// getObjectOffset - Return the assigned stack offset of the specified object
213 /// from the incoming stack pointer.
215 int64_t getObjectOffset(int ObjectIdx) const {
216 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
217 "Invalid Object Idx!");
218 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
221 /// setObjectOffset - Set the stack frame offset of the specified object. The
222 /// offset is relative to the stack pointer on entry to the function.
224 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
225 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
226 "Invalid Object Idx!");
227 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
230 /// getStackSize - Return the number of bytes that must be allocated to hold
231 /// all of the fixed size frame objects. This is only valid after
232 /// Prolog/Epilog code insertion has finalized the stack frame layout.
234 uint64_t getStackSize() const { return StackSize; }
236 /// setStackSize - Set the size of the stack...
238 void setStackSize(uint64_t Size) { StackSize = Size; }
240 /// getOffsetAdjustment - Return the correction for frame offsets.
242 int getOffsetAdjustment() const { return OffsetAdjustment; }
244 /// setOffsetAdjustment - Set the correction for frame offsets.
246 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
248 /// getMaxAlignment - Return the alignment in bytes that this function must be
249 /// aligned to, which is greater than the default stack alignment provided by
252 unsigned getMaxAlignment() const { return MaxAlignment; }
254 /// setMaxAlignment - Set the preferred alignment.
256 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
258 /// hasCalls - Return true if the current function has no function calls.
259 /// This is only valid during or after prolog/epilog code emission.
261 bool hasCalls() const { return HasCalls; }
262 void setHasCalls(bool V) { HasCalls = V; }
264 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
265 /// allocated for an outgoing function call. This is only available if
266 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
267 /// then only during or after prolog/epilog code insertion.
269 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
270 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
272 /// CreateFixedObject - Create a new object at a fixed location on the stack.
273 /// All fixed objects should be created before other objects are created for
274 /// efficiency. By default, fixed objects are immutable. This returns an
275 /// index with a negative value.
277 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
278 bool Immutable = true);
281 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
282 /// fixed stack object.
283 bool isFixedObjectIndex(int ObjectIdx) const {
284 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
287 /// isImmutableObjectIndex - Returns true if the specified index corresponds
288 /// to an immutable object.
289 bool isImmutableObjectIndex(int ObjectIdx) const {
290 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
291 "Invalid Object Idx!");
292 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
295 /// CreateStackObject - Create a new statically sized stack object, returning
296 /// a postive identifier to represent it.
298 int CreateStackObject(uint64_t Size, unsigned Alignment) {
299 // Keep track of the maximum alignment.
300 if (MaxAlignment < Alignment) MaxAlignment = Alignment;
302 assert(Size != 0 && "Cannot allocate zero size stack objects!");
303 Objects.push_back(StackObject(Size, Alignment, -1));
304 return Objects.size()-NumFixedObjects-1;
307 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
308 /// variable sized object has been created. This must be created whenever a
309 /// variable sized object is created, whether or not the index returned is
312 int CreateVariableSizedObject() {
313 HasVarSizedObjects = true;
314 if (MaxAlignment < 1) MaxAlignment = 1;
315 Objects.push_back(StackObject(0, 1, -1));
316 return Objects.size()-NumFixedObjects-1;
319 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
320 /// current function.
321 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
325 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
326 /// callee saved information.
327 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
331 /// getMachineModuleInfo - Used by a prologue/epilogue emitter (MRegisterInfo)
332 /// to provide frame layout information.
333 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
335 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
336 /// indicate that frame layout information should be gathered.
337 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
339 /// print - Used by the MachineFunction printer to print information about
340 /// stack objects. Implemented in MachineFunction.cpp
342 void print(const MachineFunction &MF, std::ostream &OS) const;
344 /// dump - Call print(MF, std::cerr) to be called from the debugger.
345 void dump(const MachineFunction &MF) const;
348 } // End llvm namespace