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"
23 class TargetRegisterClass;
25 class MachineModuleInfo;
26 class MachineFunction;
27 class TargetFrameInfo;
29 /// The CalleeSavedInfo class tracks the information need to locate where a
30 /// callee saved register in the current frame.
31 class CalleeSavedInfo {
35 const TargetRegisterClass *RegClass;
39 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
46 unsigned getReg() const { return Reg; }
47 const TargetRegisterClass *getRegClass() const { return RegClass; }
48 int getFrameIdx() const { return FrameIdx; }
49 void setFrameIdx(int FI) { FrameIdx = FI; }
52 /// The MachineFrameInfo class represents an abstract stack frame until
53 /// prolog/epilog code is inserted. This class is key to allowing stack frame
54 /// representation optimizations, such as frame pointer elimination. It also
55 /// allows more mundane (but still important) optimizations, such as reordering
56 /// of abstract objects on the stack frame.
58 /// To support this, the class assigns unique integer identifiers to stack
59 /// objects requested clients. These identifiers are negative integers for
60 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
61 /// for objects that may be reordered. Instructions which refer to stack
62 /// objects use a special MO_FrameIndex operand to represent these frame
65 /// Because this class keeps track of all references to the stack frame, it
66 /// knows when a variable sized object is allocated on the stack. This is the
67 /// sole condition which prevents frame pointer elimination, which is an
68 /// important optimization on register-poor architectures. Because original
69 /// variable sized alloca's in the source program are the only source of
70 /// variable sized stack objects, it is safe to decide whether there will be
71 /// any variable sized objects before all stack objects are known (for
72 /// example, register allocator spill code never needs variable sized
75 /// When prolog/epilog code emission is performed, the final stack frame is
76 /// built and the machine instructions are modified to refer to the actual
77 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
80 /// @brief Abstract Stack Frame Information
81 class MachineFrameInfo {
83 // StackObject - Represent a single object allocated on the stack.
85 // The size of this object on the stack. 0 means a variable sized object,
86 // ~0ULL means a dead object.
89 // Alignment - The required alignment of this stack slot.
92 // isImmutable - If true, the value of the stack object is set before
93 // entering the function and is not modified inside the function. By
94 // default, fixed objects are immutable unless marked otherwise.
97 // SPOffset - The offset of this object from the stack pointer on entry to
98 // the function. This field has no meaning for a variable sized element.
101 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM = false)
102 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {}
105 /// Objects - The list of stack objects allocated...
107 std::vector<StackObject> Objects;
109 /// NumFixedObjects - This contains the number of fixed objects contained on
110 /// the stack. Because fixed objects are stored at a negative index in the
111 /// Objects list, this is also the index to the 0th object in the list.
113 unsigned NumFixedObjects;
115 /// HasVarSizedObjects - This boolean keeps track of whether any variable
116 /// sized objects have been allocated yet.
118 bool HasVarSizedObjects;
120 /// StackSize - The prolog/epilog code inserter calculates the final stack
121 /// offsets for all of the fixed size objects, updating the Objects list
122 /// above. It then updates StackSize to contain the number of bytes that need
123 /// to be allocated on entry to the function.
127 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
128 /// have the actual offset from the stack/frame pointer. The calculation is
129 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() +
130 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are
131 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward
133 int OffsetAdjustment;
135 /// MaxAlignment - The prolog/epilog code inserter may process objects
136 /// that require greater alignment than the default alignment the target
137 /// provides. To handle this, MaxAlignment is set to the maximum alignment
138 /// needed by the objects on the current frame. If this is greater than the
139 /// native alignment maintained by the compiler, dynamic alignment code will
142 unsigned MaxAlignment;
144 /// HasCalls - Set to true if this function has any function calls. This is
145 /// only valid during and after prolog/epilog code insertion.
148 /// MaxCallFrameSize - This contains the size of the largest call frame if the
149 /// target uses frame setup/destroy pseudo instructions (as defined in the
150 /// TargetFrameInfo class). This information is important for frame pointer
151 /// elimination. If is only valid during and after prolog/epilog code
154 unsigned MaxCallFrameSize;
156 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
157 /// callee saved register saved in the frame. Beyond its use by the prolog/
158 /// epilog code inserter, this data used for debug info and exception
160 std::vector<CalleeSavedInfo> CSInfo;
162 /// MMI - This field is set (via setMachineModuleInfo) by a module info
163 /// consumer (ex. DwarfWriter) to indicate that frame layout information
164 /// should be acquired. Typically, it's the responsibility of the target's
165 /// TargetRegisterInfo prologue/epilogue emitting code to inform
166 /// MachineModuleInfo of frame layouts.
167 MachineModuleInfo *MMI;
169 /// TargetFrameInfo - Target information about frame layout.
171 const TargetFrameInfo &TFI;
173 MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
174 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
175 HasVarSizedObjects = false;
177 MaxCallFrameSize = 0;
181 /// hasStackObjects - Return true if there are any stack objects in this
184 bool hasStackObjects() const { return !Objects.empty(); }
186 /// hasVarSizedObjects - This method may be called any time after instruction
187 /// selection is complete to determine if the stack frame for this function
188 /// contains any variable sized objects.
190 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
192 /// getObjectIndexBegin - Return the minimum frame object index...
194 int getObjectIndexBegin() const { return -NumFixedObjects; }
196 /// getObjectIndexEnd - Return one past the maximum frame object index...
198 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
200 /// getNumFixedObjects() - Return the number of fixed objects.
201 unsigned getNumFixedObjects() const { return NumFixedObjects; }
203 /// getNumObjects() - Return the number of objects.
205 unsigned getNumObjects() const { return Objects.size(); }
207 /// getObjectSize - Return the size of the specified object
209 int64_t getObjectSize(int ObjectIdx) const {
210 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
211 "Invalid Object Idx!");
212 return Objects[ObjectIdx+NumFixedObjects].Size;
215 // setObjectSize - Change the size of the specified stack object...
216 void setObjectSize(int ObjectIdx, int64_t Size) {
217 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
218 "Invalid Object Idx!");
219 Objects[ObjectIdx+NumFixedObjects].Size = Size;
222 /// getObjectAlignment - Return the alignment of the specified stack object...
223 unsigned getObjectAlignment(int ObjectIdx) const {
224 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
225 "Invalid Object Idx!");
226 return Objects[ObjectIdx+NumFixedObjects].Alignment;
229 /// setObjectAlignment - Change the alignment of the specified stack object...
230 void setObjectAlignment(int ObjectIdx, unsigned Align) {
231 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
232 "Invalid Object Idx!");
233 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
236 /// getObjectOffset - Return the assigned stack offset of the specified object
237 /// from the incoming stack pointer.
239 int64_t getObjectOffset(int ObjectIdx) const {
240 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
241 "Invalid Object Idx!");
242 assert(!isDeadObjectIndex(ObjectIdx) &&
243 "Getting frame offset for a dead object?");
244 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
247 /// setObjectOffset - Set the stack frame offset of the specified object. The
248 /// offset is relative to the stack pointer on entry to the function.
250 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
251 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
252 "Invalid Object Idx!");
253 assert(!isDeadObjectIndex(ObjectIdx) &&
254 "Setting frame offset for a dead object?");
255 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
258 /// getStackSize - Return the number of bytes that must be allocated to hold
259 /// all of the fixed size frame objects. This is only valid after
260 /// Prolog/Epilog code insertion has finalized the stack frame layout.
262 uint64_t getStackSize() const { return StackSize; }
264 /// setStackSize - Set the size of the stack...
266 void setStackSize(uint64_t Size) { StackSize = Size; }
268 /// getOffsetAdjustment - Return the correction for frame offsets.
270 int getOffsetAdjustment() const { return OffsetAdjustment; }
272 /// setOffsetAdjustment - Set the correction for frame offsets.
274 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
276 /// getMaxAlignment - Return the alignment in bytes that this function must be
277 /// aligned to, which is greater than the default stack alignment provided by
280 unsigned getMaxAlignment() const { return MaxAlignment; }
282 /// setMaxAlignment - Set the preferred alignment.
284 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
286 /// hasCalls - Return true if the current function has no function calls.
287 /// This is only valid during or after prolog/epilog code emission.
289 bool hasCalls() const { return HasCalls; }
290 void setHasCalls(bool V) { HasCalls = V; }
292 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
293 /// allocated for an outgoing function call. This is only available if
294 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
295 /// then only during or after prolog/epilog code insertion.
297 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
298 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
300 /// CreateFixedObject - Create a new object at a fixed location on the stack.
301 /// All fixed objects should be created before other objects are created for
302 /// efficiency. By default, fixed objects are immutable. This returns an
303 /// index with a negative value.
305 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
306 bool Immutable = true);
309 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
310 /// fixed stack object.
311 bool isFixedObjectIndex(int ObjectIdx) const {
312 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
315 /// isImmutableObjectIndex - Returns true if the specified index corresponds
316 /// to an immutable object.
317 bool isImmutableObjectIndex(int ObjectIdx) const {
318 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
319 "Invalid Object Idx!");
320 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
323 /// isDeadObjectIndex - Returns true if the specified index corresponds to
325 bool isDeadObjectIndex(int ObjectIdx) const {
326 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
327 "Invalid Object Idx!");
328 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
331 /// CreateStackObject - Create a new statically sized stack object, returning
332 /// a nonnegative identifier to represent it.
334 int CreateStackObject(uint64_t Size, unsigned Alignment) {
335 assert(Size != 0 && "Cannot allocate zero size stack objects!");
336 Objects.push_back(StackObject(Size, Alignment, -1));
337 return (int)Objects.size()-NumFixedObjects-1;
340 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
342 void RemoveStackObject(int ObjectIdx) {
344 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
347 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
348 /// variable sized object has been created. This must be created whenever a
349 /// variable sized object is created, whether or not the index returned is
352 int CreateVariableSizedObject() {
353 HasVarSizedObjects = true;
354 Objects.push_back(StackObject(0, 1, -1));
355 return (int)Objects.size()-NumFixedObjects-1;
358 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
359 /// current function.
360 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
364 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
365 /// callee saved information.
366 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
370 /// getMachineModuleInfo - Used by a prologue/epilogue
371 /// emitter (TargetRegisterInfo) to provide frame layout information.
372 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
374 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
375 /// indicate that frame layout information should be gathered.
376 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
378 /// print - Used by the MachineFunction printer to print information about
379 /// stack objects. Implemented in MachineFunction.cpp
381 void print(const MachineFunction &MF, std::ostream &OS) const;
383 /// dump - Call print(MF, std::cerr) to be called from the debugger.
384 void dump(const MachineFunction &MF) const;
387 } // End llvm namespace