MachineFrameInfo.h revision 203954
1//===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// The file defines the MachineFrameInfo class. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H 15#define LLVM_CODEGEN_MACHINEFRAMEINFO_H 16 17#include "llvm/ADT/BitVector.h" 18#include "llvm/ADT/DenseMap.h" 19#include "llvm/ADT/SmallVector.h" 20#include "llvm/System/DataTypes.h" 21#include <cassert> 22#include <limits> 23#include <vector> 24 25namespace llvm { 26class raw_ostream; 27class TargetData; 28class TargetRegisterClass; 29class Type; 30class MachineModuleInfo; 31class MachineFunction; 32class MachineBasicBlock; 33class TargetFrameInfo; 34 35/// The CalleeSavedInfo class tracks the information need to locate where a 36/// callee saved register in the current frame. 37class CalleeSavedInfo { 38 39private: 40 unsigned Reg; 41 const TargetRegisterClass *RegClass; 42 int FrameIdx; 43 44public: 45 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0) 46 : Reg(R) 47 , RegClass(RC) 48 , FrameIdx(FI) 49 {} 50 51 // Accessors. 52 unsigned getReg() const { return Reg; } 53 const TargetRegisterClass *getRegClass() const { return RegClass; } 54 int getFrameIdx() const { return FrameIdx; } 55 void setFrameIdx(int FI) { FrameIdx = FI; } 56}; 57 58/// The MachineFrameInfo class represents an abstract stack frame until 59/// prolog/epilog code is inserted. This class is key to allowing stack frame 60/// representation optimizations, such as frame pointer elimination. It also 61/// allows more mundane (but still important) optimizations, such as reordering 62/// of abstract objects on the stack frame. 63/// 64/// To support this, the class assigns unique integer identifiers to stack 65/// objects requested clients. These identifiers are negative integers for 66/// fixed stack objects (such as arguments passed on the stack) or nonnegative 67/// for objects that may be reordered. Instructions which refer to stack 68/// objects use a special MO_FrameIndex operand to represent these frame 69/// indexes. 70/// 71/// Because this class keeps track of all references to the stack frame, it 72/// knows when a variable sized object is allocated on the stack. This is the 73/// sole condition which prevents frame pointer elimination, which is an 74/// important optimization on register-poor architectures. Because original 75/// variable sized alloca's in the source program are the only source of 76/// variable sized stack objects, it is safe to decide whether there will be 77/// any variable sized objects before all stack objects are known (for 78/// example, register allocator spill code never needs variable sized 79/// objects). 80/// 81/// When prolog/epilog code emission is performed, the final stack frame is 82/// built and the machine instructions are modified to refer to the actual 83/// stack offsets of the object, eliminating all MO_FrameIndex operands from 84/// the program. 85/// 86/// @brief Abstract Stack Frame Information 87class MachineFrameInfo { 88 89 // StackObject - Represent a single object allocated on the stack. 90 struct StackObject { 91 // SPOffset - The offset of this object from the stack pointer on entry to 92 // the function. This field has no meaning for a variable sized element. 93 int64_t SPOffset; 94 95 // The size of this object on the stack. 0 means a variable sized object, 96 // ~0ULL means a dead object. 97 uint64_t Size; 98 99 // Alignment - The required alignment of this stack slot. 100 unsigned Alignment; 101 102 // isImmutable - If true, the value of the stack object is set before 103 // entering the function and is not modified inside the function. By 104 // default, fixed objects are immutable unless marked otherwise. 105 bool isImmutable; 106 107 // isSpillSlot - If true, the stack object is used as spill slot. It 108 // cannot alias any other memory objects. 109 bool isSpillSlot; 110 111 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM, 112 bool isSS) 113 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM), 114 isSpillSlot(isSS) {} 115 }; 116 117 /// Objects - The list of stack objects allocated... 118 /// 119 std::vector<StackObject> Objects; 120 121 /// NumFixedObjects - This contains the number of fixed objects contained on 122 /// the stack. Because fixed objects are stored at a negative index in the 123 /// Objects list, this is also the index to the 0th object in the list. 124 /// 125 unsigned NumFixedObjects; 126 127 /// HasVarSizedObjects - This boolean keeps track of whether any variable 128 /// sized objects have been allocated yet. 129 /// 130 bool HasVarSizedObjects; 131 132 /// FrameAddressTaken - This boolean keeps track of whether there is a call 133 /// to builtin \@llvm.frameaddress. 134 bool FrameAddressTaken; 135 136 /// StackSize - The prolog/epilog code inserter calculates the final stack 137 /// offsets for all of the fixed size objects, updating the Objects list 138 /// above. It then updates StackSize to contain the number of bytes that need 139 /// to be allocated on entry to the function. 140 /// 141 uint64_t StackSize; 142 143 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to 144 /// have the actual offset from the stack/frame pointer. The exact usage of 145 /// this is target-dependent, but it is typically used to adjust between 146 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via 147 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set 148 /// to the distance between the initial SP and the value in FP. For many 149 /// targets, this value is only used when generating debug info (via 150 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the 151 /// corresponding adjustments are performed directly. 152 int OffsetAdjustment; 153 154 /// MaxAlignment - The prolog/epilog code inserter may process objects 155 /// that require greater alignment than the default alignment the target 156 /// provides. To handle this, MaxAlignment is set to the maximum alignment 157 /// needed by the objects on the current frame. If this is greater than the 158 /// native alignment maintained by the compiler, dynamic alignment code will 159 /// be needed. 160 /// 161 unsigned MaxAlignment; 162 163 /// HasCalls - Set to true if this function has any function calls. This is 164 /// only valid during and after prolog/epilog code insertion. 165 bool HasCalls; 166 167 /// StackProtectorIdx - The frame index for the stack protector. 168 int StackProtectorIdx; 169 170 /// MaxCallFrameSize - This contains the size of the largest call frame if the 171 /// target uses frame setup/destroy pseudo instructions (as defined in the 172 /// TargetFrameInfo class). This information is important for frame pointer 173 /// elimination. If is only valid during and after prolog/epilog code 174 /// insertion. 175 /// 176 unsigned MaxCallFrameSize; 177 178 /// CSInfo - The prolog/epilog code inserter fills in this vector with each 179 /// callee saved register saved in the frame. Beyond its use by the prolog/ 180 /// epilog code inserter, this data used for debug info and exception 181 /// handling. 182 std::vector<CalleeSavedInfo> CSInfo; 183 184 /// CSIValid - Has CSInfo been set yet? 185 bool CSIValid; 186 187 /// SpillObjects - A vector indicating which frame indices refer to 188 /// spill slots. 189 SmallVector<bool, 8> SpillObjects; 190 191 /// MMI - This field is set (via setMachineModuleInfo) by a module info 192 /// consumer (ex. DwarfWriter) to indicate that frame layout information 193 /// should be acquired. Typically, it's the responsibility of the target's 194 /// TargetRegisterInfo prologue/epilogue emitting code to inform 195 /// MachineModuleInfo of frame layouts. 196 MachineModuleInfo *MMI; 197 198 /// TargetFrameInfo - Target information about frame layout. 199 /// 200 const TargetFrameInfo &TFI; 201 202public: 203 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) { 204 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0; 205 HasVarSizedObjects = false; 206 FrameAddressTaken = false; 207 HasCalls = false; 208 StackProtectorIdx = -1; 209 MaxCallFrameSize = 0; 210 CSIValid = false; 211 MMI = 0; 212 } 213 214 /// hasStackObjects - Return true if there are any stack objects in this 215 /// function. 216 /// 217 bool hasStackObjects() const { return !Objects.empty(); } 218 219 /// hasVarSizedObjects - This method may be called any time after instruction 220 /// selection is complete to determine if the stack frame for this function 221 /// contains any variable sized objects. 222 /// 223 bool hasVarSizedObjects() const { return HasVarSizedObjects; } 224 225 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the 226 /// stack protector object. 227 /// 228 int getStackProtectorIndex() const { return StackProtectorIdx; } 229 void setStackProtectorIndex(int I) { StackProtectorIdx = I; } 230 231 /// isFrameAddressTaken - This method may be called any time after instruction 232 /// selection is complete to determine if there is a call to 233 /// \@llvm.frameaddress in this function. 234 bool isFrameAddressTaken() const { return FrameAddressTaken; } 235 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; } 236 237 /// getObjectIndexBegin - Return the minimum frame object index. 238 /// 239 int getObjectIndexBegin() const { return -NumFixedObjects; } 240 241 /// getObjectIndexEnd - Return one past the maximum frame object index. 242 /// 243 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; } 244 245 /// getNumFixedObjects() - Return the number of fixed objects. 246 unsigned getNumFixedObjects() const { return NumFixedObjects; } 247 248 /// getNumObjects() - Return the number of objects. 249 /// 250 unsigned getNumObjects() const { return Objects.size(); } 251 252 /// getObjectSize - Return the size of the specified object. 253 /// 254 int64_t getObjectSize(int ObjectIdx) const { 255 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 256 "Invalid Object Idx!"); 257 return Objects[ObjectIdx+NumFixedObjects].Size; 258 } 259 260 /// setObjectSize - Change the size of the specified stack object. 261 void setObjectSize(int ObjectIdx, int64_t Size) { 262 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 263 "Invalid Object Idx!"); 264 Objects[ObjectIdx+NumFixedObjects].Size = Size; 265 } 266 267 /// getObjectAlignment - Return the alignment of the specified stack object. 268 unsigned getObjectAlignment(int ObjectIdx) const { 269 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 270 "Invalid Object Idx!"); 271 return Objects[ObjectIdx+NumFixedObjects].Alignment; 272 } 273 274 /// setObjectAlignment - Change the alignment of the specified stack object. 275 void setObjectAlignment(int ObjectIdx, unsigned Align) { 276 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 277 "Invalid Object Idx!"); 278 Objects[ObjectIdx+NumFixedObjects].Alignment = Align; 279 MaxAlignment = std::max(MaxAlignment, Align); 280 } 281 282 /// getObjectOffset - Return the assigned stack offset of the specified object 283 /// from the incoming stack pointer. 284 /// 285 int64_t getObjectOffset(int ObjectIdx) const { 286 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 287 "Invalid Object Idx!"); 288 assert(!isDeadObjectIndex(ObjectIdx) && 289 "Getting frame offset for a dead object?"); 290 return Objects[ObjectIdx+NumFixedObjects].SPOffset; 291 } 292 293 /// setObjectOffset - Set the stack frame offset of the specified object. The 294 /// offset is relative to the stack pointer on entry to the function. 295 /// 296 void setObjectOffset(int ObjectIdx, int64_t SPOffset) { 297 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 298 "Invalid Object Idx!"); 299 assert(!isDeadObjectIndex(ObjectIdx) && 300 "Setting frame offset for a dead object?"); 301 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset; 302 } 303 304 /// getStackSize - Return the number of bytes that must be allocated to hold 305 /// all of the fixed size frame objects. This is only valid after 306 /// Prolog/Epilog code insertion has finalized the stack frame layout. 307 /// 308 uint64_t getStackSize() const { return StackSize; } 309 310 /// setStackSize - Set the size of the stack... 311 /// 312 void setStackSize(uint64_t Size) { StackSize = Size; } 313 314 /// getOffsetAdjustment - Return the correction for frame offsets. 315 /// 316 int getOffsetAdjustment() const { return OffsetAdjustment; } 317 318 /// setOffsetAdjustment - Set the correction for frame offsets. 319 /// 320 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; } 321 322 /// getMaxAlignment - Return the alignment in bytes that this function must be 323 /// aligned to, which is greater than the default stack alignment provided by 324 /// the target. 325 /// 326 unsigned getMaxAlignment() const { return MaxAlignment; } 327 328 /// setMaxAlignment - Set the preferred alignment. 329 /// 330 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; } 331 332 /// hasCalls - Return true if the current function has no function calls. 333 /// This is only valid during or after prolog/epilog code emission. 334 /// 335 bool hasCalls() const { return HasCalls; } 336 void setHasCalls(bool V) { HasCalls = V; } 337 338 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be 339 /// allocated for an outgoing function call. This is only available if 340 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and 341 /// then only during or after prolog/epilog code insertion. 342 /// 343 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; } 344 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; } 345 346 /// CreateFixedObject - Create a new object at a fixed location on the stack. 347 /// All fixed objects should be created before other objects are created for 348 /// efficiency. By default, fixed objects are immutable. This returns an 349 /// index with a negative value. 350 /// 351 int CreateFixedObject(uint64_t Size, int64_t SPOffset, 352 bool Immutable, bool isSS); 353 354 355 /// isFixedObjectIndex - Returns true if the specified index corresponds to a 356 /// fixed stack object. 357 bool isFixedObjectIndex(int ObjectIdx) const { 358 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects); 359 } 360 361 /// isImmutableObjectIndex - Returns true if the specified index corresponds 362 /// to an immutable object. 363 bool isImmutableObjectIndex(int ObjectIdx) const { 364 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 365 "Invalid Object Idx!"); 366 return Objects[ObjectIdx+NumFixedObjects].isImmutable; 367 } 368 369 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds 370 /// to a spill slot.. 371 bool isSpillSlotObjectIndex(int ObjectIdx) const { 372 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 373 "Invalid Object Idx!"); 374 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;; 375 } 376 377 /// isDeadObjectIndex - Returns true if the specified index corresponds to 378 /// a dead object. 379 bool isDeadObjectIndex(int ObjectIdx) const { 380 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 381 "Invalid Object Idx!"); 382 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL; 383 } 384 385 /// CreateStackObject - Create a new statically sized stack object, 386 /// returning a nonnegative identifier to represent it. 387 /// 388 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS) { 389 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 390 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS)); 391 int Index = (int)Objects.size()-NumFixedObjects-1; 392 assert(Index >= 0 && "Bad frame index!"); 393 MaxAlignment = std::max(MaxAlignment, Alignment); 394 return Index; 395 } 396 397 /// CreateSpillStackObject - Create a new statically sized stack 398 /// object that represents a spill slot, returning a nonnegative 399 /// identifier to represent it. 400 /// 401 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) { 402 CreateStackObject(Size, Alignment, true); 403 int Index = (int)Objects.size()-NumFixedObjects-1; 404 MaxAlignment = std::max(MaxAlignment, Alignment); 405 return Index; 406 } 407 408 /// RemoveStackObject - Remove or mark dead a statically sized stack object. 409 /// 410 void RemoveStackObject(int ObjectIdx) { 411 // Mark it dead. 412 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL; 413 } 414 415 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a 416 /// variable sized object has been created. This must be created whenever a 417 /// variable sized object is created, whether or not the index returned is 418 /// actually used. 419 /// 420 int CreateVariableSizedObject() { 421 HasVarSizedObjects = true; 422 Objects.push_back(StackObject(0, 1, 0, false, false)); 423 return (int)Objects.size()-NumFixedObjects-1; 424 } 425 426 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the 427 /// current function. 428 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const { 429 return CSInfo; 430 } 431 432 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's 433 /// callee saved information. 434 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) { 435 CSInfo = CSI; 436 } 437 438 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet? 439 bool isCalleeSavedInfoValid() const { return CSIValid; } 440 441 void setCalleeSavedInfoValid(bool v) { CSIValid = v; } 442 443 /// getPristineRegs - Return a set of physical registers that are pristine on 444 /// entry to the MBB. 445 /// 446 /// Pristine registers hold a value that is useless to the current function, 447 /// but that must be preserved - they are callee saved registers that have not 448 /// been saved yet. 449 /// 450 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this 451 /// method always returns an empty set. 452 BitVector getPristineRegs(const MachineBasicBlock *MBB) const; 453 454 /// getMachineModuleInfo - Used by a prologue/epilogue 455 /// emitter (TargetRegisterInfo) to provide frame layout information. 456 MachineModuleInfo *getMachineModuleInfo() const { return MMI; } 457 458 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to 459 /// indicate that frame layout information should be gathered. 460 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; } 461 462 /// print - Used by the MachineFunction printer to print information about 463 /// stack objects. Implemented in MachineFunction.cpp 464 /// 465 void print(const MachineFunction &MF, raw_ostream &OS) const; 466 467 /// dump - Print the function to stderr. 468 void dump(const MachineFunction &MF) const; 469}; 470 471} // End llvm namespace 472 473#endif 474