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/ADT/BitVector.h"
18 #include "llvm/ADT/DenseSet.h"
19 #include "llvm/Support/DataTypes.h"
26 class TargetRegisterClass;
28 class MachineModuleInfo;
29 class MachineFunction;
30 class MachineBasicBlock;
31 class TargetFrameInfo;
33 /// The CalleeSavedInfo class tracks the information need to locate where a
34 /// callee saved register in the current frame.
35 class CalleeSavedInfo {
39 const TargetRegisterClass *RegClass;
43 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0)
50 unsigned getReg() const { return Reg; }
51 const TargetRegisterClass *getRegClass() const { return RegClass; }
52 int getFrameIdx() const { return FrameIdx; }
53 void setFrameIdx(int FI) { FrameIdx = FI; }
56 /// The MachineFrameInfo class represents an abstract stack frame until
57 /// prolog/epilog code is inserted. This class is key to allowing stack frame
58 /// representation optimizations, such as frame pointer elimination. It also
59 /// allows more mundane (but still important) optimizations, such as reordering
60 /// of abstract objects on the stack frame.
62 /// To support this, the class assigns unique integer identifiers to stack
63 /// objects requested clients. These identifiers are negative integers for
64 /// fixed stack objects (such as arguments passed on the stack) or nonnegative
65 /// for objects that may be reordered. Instructions which refer to stack
66 /// objects use a special MO_FrameIndex operand to represent these frame
69 /// Because this class keeps track of all references to the stack frame, it
70 /// knows when a variable sized object is allocated on the stack. This is the
71 /// sole condition which prevents frame pointer elimination, which is an
72 /// important optimization on register-poor architectures. Because original
73 /// variable sized alloca's in the source program are the only source of
74 /// variable sized stack objects, it is safe to decide whether there will be
75 /// any variable sized objects before all stack objects are known (for
76 /// example, register allocator spill code never needs variable sized
79 /// When prolog/epilog code emission is performed, the final stack frame is
80 /// built and the machine instructions are modified to refer to the actual
81 /// stack offsets of the object, eliminating all MO_FrameIndex operands from
84 /// @brief Abstract Stack Frame Information
85 class MachineFrameInfo {
87 // StackObject - Represent a single object allocated on the stack.
89 // The size of this object on the stack. 0 means a variable sized object,
90 // ~0ULL means a dead object.
93 // Alignment - The required alignment of this stack slot.
96 // isImmutable - If true, the value of the stack object is set before
97 // entering the function and is not modified inside the function. By
98 // default, fixed objects are immutable unless marked otherwise.
101 // SPOffset - The offset of this object from the stack pointer on entry to
102 // the function. This field has no meaning for a variable sized element.
105 StackObject(uint64_t Sz, unsigned Al, int64_t SP = 0, bool IM = false)
106 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {}
109 /// Objects - The list of stack objects allocated...
111 std::vector<StackObject> Objects;
113 /// NumFixedObjects - This contains the number of fixed objects contained on
114 /// the stack. Because fixed objects are stored at a negative index in the
115 /// Objects list, this is also the index to the 0th object in the list.
117 unsigned NumFixedObjects;
119 /// HasVarSizedObjects - This boolean keeps track of whether any variable
120 /// sized objects have been allocated yet.
122 bool HasVarSizedObjects;
124 /// FrameAddressTaken - This boolean keeps track of whether there is a call
125 /// to builtin \@llvm.frameaddress.
126 bool FrameAddressTaken;
128 /// StackSize - The prolog/epilog code inserter calculates the final stack
129 /// offsets for all of the fixed size objects, updating the Objects list
130 /// above. It then updates StackSize to contain the number of bytes that need
131 /// to be allocated on entry to the function.
135 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to
136 /// have the actual offset from the stack/frame pointer. The exact usage of
137 /// this is target-dependent, but it is typically used to adjust between
138 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via
139 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set
140 /// to the distance between the initial SP and the value in FP. For many
141 /// targets, this value is only used when generating debug info (via
142 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the
143 /// corresponding adjustments are performed directly.
144 int OffsetAdjustment;
146 /// MaxAlignment - The prolog/epilog code inserter may process objects
147 /// that require greater alignment than the default alignment the target
148 /// provides. To handle this, MaxAlignment is set to the maximum alignment
149 /// needed by the objects on the current frame. If this is greater than the
150 /// native alignment maintained by the compiler, dynamic alignment code will
153 unsigned MaxAlignment;
155 /// HasCalls - Set to true if this function has any function calls. This is
156 /// only valid during and after prolog/epilog code insertion.
159 /// StackProtectorIdx - The frame index for the stack protector.
160 int StackProtectorIdx;
162 /// MaxCallFrameSize - This contains the size of the largest call frame if the
163 /// target uses frame setup/destroy pseudo instructions (as defined in the
164 /// TargetFrameInfo class). This information is important for frame pointer
165 /// elimination. If is only valid during and after prolog/epilog code
168 unsigned MaxCallFrameSize;
170 /// CSInfo - The prolog/epilog code inserter fills in this vector with each
171 /// callee saved register saved in the frame. Beyond its use by the prolog/
172 /// epilog code inserter, this data used for debug info and exception
174 std::vector<CalleeSavedInfo> CSInfo;
176 /// CSIValid - Has CSInfo been set yet?
179 /// MMI - This field is set (via setMachineModuleInfo) by a module info
180 /// consumer (ex. DwarfWriter) to indicate that frame layout information
181 /// should be acquired. Typically, it's the responsibility of the target's
182 /// TargetRegisterInfo prologue/epilogue emitting code to inform
183 /// MachineModuleInfo of frame layouts.
184 MachineModuleInfo *MMI;
186 /// TargetFrameInfo - Target information about frame layout.
188 const TargetFrameInfo &TFI;
190 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
191 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
192 HasVarSizedObjects = false;
193 FrameAddressTaken = false;
195 StackProtectorIdx = -1;
196 MaxCallFrameSize = 0;
201 /// hasStackObjects - Return true if there are any stack objects in this
204 bool hasStackObjects() const { return !Objects.empty(); }
206 /// hasVarSizedObjects - This method may be called any time after instruction
207 /// selection is complete to determine if the stack frame for this function
208 /// contains any variable sized objects.
210 bool hasVarSizedObjects() const { return HasVarSizedObjects; }
212 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the
213 /// stack protector object.
215 int getStackProtectorIndex() const { return StackProtectorIdx; }
216 void setStackProtectorIndex(int I) { StackProtectorIdx = I; }
218 /// isFrameAddressTaken - This method may be called any time after instruction
219 /// selection is complete to determine if there is a call to
220 /// \@llvm.frameaddress in this function.
221 bool isFrameAddressTaken() const { return FrameAddressTaken; }
222 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; }
224 /// getObjectIndexBegin - Return the minimum frame object index.
226 int getObjectIndexBegin() const { return -NumFixedObjects; }
228 /// getObjectIndexEnd - Return one past the maximum frame object index.
230 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; }
232 /// getNumFixedObjects() - Return the number of fixed objects.
233 unsigned getNumFixedObjects() const { return NumFixedObjects; }
235 /// getNumObjects() - Return the number of objects.
237 unsigned getNumObjects() const { return Objects.size(); }
239 /// getObjectSize - Return the size of the specified object.
241 int64_t getObjectSize(int ObjectIdx) const {
242 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
243 "Invalid Object Idx!");
244 return Objects[ObjectIdx+NumFixedObjects].Size;
247 /// setObjectSize - Change the size of the specified stack object.
248 void setObjectSize(int ObjectIdx, int64_t Size) {
249 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
250 "Invalid Object Idx!");
251 Objects[ObjectIdx+NumFixedObjects].Size = Size;
254 /// getObjectAlignment - Return the alignment of the specified stack object.
255 unsigned getObjectAlignment(int ObjectIdx) const {
256 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
257 "Invalid Object Idx!");
258 return Objects[ObjectIdx+NumFixedObjects].Alignment;
261 /// setObjectAlignment - Change the alignment of the specified stack object.
262 void setObjectAlignment(int ObjectIdx, unsigned Align) {
263 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
264 "Invalid Object Idx!");
265 Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
268 /// getObjectOffset - Return the assigned stack offset of the specified object
269 /// from the incoming stack pointer.
271 int64_t getObjectOffset(int ObjectIdx) const {
272 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
273 "Invalid Object Idx!");
274 assert(!isDeadObjectIndex(ObjectIdx) &&
275 "Getting frame offset for a dead object?");
276 return Objects[ObjectIdx+NumFixedObjects].SPOffset;
279 /// setObjectOffset - Set the stack frame offset of the specified object. The
280 /// offset is relative to the stack pointer on entry to the function.
282 void setObjectOffset(int ObjectIdx, int64_t SPOffset) {
283 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
284 "Invalid Object Idx!");
285 assert(!isDeadObjectIndex(ObjectIdx) &&
286 "Setting frame offset for a dead object?");
287 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset;
290 /// getStackSize - Return the number of bytes that must be allocated to hold
291 /// all of the fixed size frame objects. This is only valid after
292 /// Prolog/Epilog code insertion has finalized the stack frame layout.
294 uint64_t getStackSize() const { return StackSize; }
296 /// setStackSize - Set the size of the stack...
298 void setStackSize(uint64_t Size) { StackSize = Size; }
300 /// getOffsetAdjustment - Return the correction for frame offsets.
302 int getOffsetAdjustment() const { return OffsetAdjustment; }
304 /// setOffsetAdjustment - Set the correction for frame offsets.
306 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
308 /// getMaxAlignment - Return the alignment in bytes that this function must be
309 /// aligned to, which is greater than the default stack alignment provided by
312 unsigned getMaxAlignment() const { return MaxAlignment; }
314 /// setMaxAlignment - Set the preferred alignment.
316 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
318 /// hasCalls - Return true if the current function has no function calls.
319 /// This is only valid during or after prolog/epilog code emission.
321 bool hasCalls() const { return HasCalls; }
322 void setHasCalls(bool V) { HasCalls = V; }
324 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be
325 /// allocated for an outgoing function call. This is only available if
326 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and
327 /// then only during or after prolog/epilog code insertion.
329 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; }
330 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; }
332 /// CreateFixedObject - Create a new object at a fixed location on the stack.
333 /// All fixed objects should be created before other objects are created for
334 /// efficiency. By default, fixed objects are immutable. This returns an
335 /// index with a negative value.
337 int CreateFixedObject(uint64_t Size, int64_t SPOffset,
338 bool Immutable = true);
341 /// isFixedObjectIndex - Returns true if the specified index corresponds to a
342 /// fixed stack object.
343 bool isFixedObjectIndex(int ObjectIdx) const {
344 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects);
347 /// isImmutableObjectIndex - Returns true if the specified index corresponds
348 /// to an immutable object.
349 bool isImmutableObjectIndex(int ObjectIdx) const {
350 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
351 "Invalid Object Idx!");
352 return Objects[ObjectIdx+NumFixedObjects].isImmutable;
355 /// isDeadObjectIndex - Returns true if the specified index corresponds to
357 bool isDeadObjectIndex(int ObjectIdx) const {
358 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
359 "Invalid Object Idx!");
360 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL;
363 /// CreateStackObject - Create a new statically sized stack object, returning
364 /// a nonnegative identifier to represent it.
366 int CreateStackObject(uint64_t Size, unsigned Alignment) {
367 assert(Size != 0 && "Cannot allocate zero size stack objects!");
368 Objects.push_back(StackObject(Size, Alignment));
369 return (int)Objects.size()-NumFixedObjects-1;
372 /// RemoveStackObject - Remove or mark dead a statically sized stack object.
374 void RemoveStackObject(int ObjectIdx) {
376 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
379 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a
380 /// variable sized object has been created. This must be created whenever a
381 /// variable sized object is created, whether or not the index returned is
384 int CreateVariableSizedObject() {
385 HasVarSizedObjects = true;
386 Objects.push_back(StackObject(0, 1));
387 return (int)Objects.size()-NumFixedObjects-1;
390 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the
391 /// current function.
392 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
396 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's
397 /// callee saved information.
398 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) {
402 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet?
403 bool isCalleeSavedInfoValid() const { return CSIValid; }
405 void setCalleeSavedInfoValid(bool v) { CSIValid = v; }
407 /// getPristineRegs - Return a set of physical registers that are pristine on
408 /// entry to the MBB.
410 /// Pristine registers hold a value that is useless to the current function,
411 /// but that must be preserved - they are callee saved registers that have not
414 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this
415 /// method always returns an empty set.
416 BitVector getPristineRegs(const MachineBasicBlock *MBB) const;
418 /// getMachineModuleInfo - Used by a prologue/epilogue
419 /// emitter (TargetRegisterInfo) to provide frame layout information.
420 MachineModuleInfo *getMachineModuleInfo() const { return MMI; }
422 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to
423 /// indicate that frame layout information should be gathered.
424 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; }
426 /// print - Used by the MachineFunction printer to print information about
427 /// stack objects. Implemented in MachineFunction.cpp
429 void print(const MachineFunction &MF, raw_ostream &OS) const;
431 /// dump - Print the function to stderr.
432 void dump(const MachineFunction &MF) const;
435 } // End llvm namespace