MachineFrameInfo.h revision 239462
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/SmallVector.h" 18#include "llvm/Support/DataTypes.h" 19#include <cassert> 20#include <vector> 21 22namespace llvm { 23class raw_ostream; 24class TargetData; 25class TargetRegisterClass; 26class Type; 27class MachineFunction; 28class MachineBasicBlock; 29class TargetFrameLowering; 30class BitVector; 31 32/// The CalleeSavedInfo class tracks the information need to locate where a 33/// callee saved register is in the current frame. 34class CalleeSavedInfo { 35 unsigned Reg; 36 int FrameIdx; 37 38public: 39 explicit CalleeSavedInfo(unsigned R, int FI = 0) 40 : Reg(R), FrameIdx(FI) {} 41 42 // Accessors. 43 unsigned getReg() const { return Reg; } 44 int getFrameIdx() const { return FrameIdx; } 45 void setFrameIdx(int FI) { FrameIdx = FI; } 46}; 47 48/// The MachineFrameInfo class represents an abstract stack frame until 49/// prolog/epilog code is inserted. This class is key to allowing stack frame 50/// representation optimizations, such as frame pointer elimination. It also 51/// allows more mundane (but still important) optimizations, such as reordering 52/// of abstract objects on the stack frame. 53/// 54/// To support this, the class assigns unique integer identifiers to stack 55/// objects requested clients. These identifiers are negative integers for 56/// fixed stack objects (such as arguments passed on the stack) or nonnegative 57/// for objects that may be reordered. Instructions which refer to stack 58/// objects use a special MO_FrameIndex operand to represent these frame 59/// indexes. 60/// 61/// Because this class keeps track of all references to the stack frame, it 62/// knows when a variable sized object is allocated on the stack. This is the 63/// sole condition which prevents frame pointer elimination, which is an 64/// important optimization on register-poor architectures. Because original 65/// variable sized alloca's in the source program are the only source of 66/// variable sized stack objects, it is safe to decide whether there will be 67/// any variable sized objects before all stack objects are known (for 68/// example, register allocator spill code never needs variable sized 69/// objects). 70/// 71/// When prolog/epilog code emission is performed, the final stack frame is 72/// built and the machine instructions are modified to refer to the actual 73/// stack offsets of the object, eliminating all MO_FrameIndex operands from 74/// the program. 75/// 76/// @brief Abstract Stack Frame Information 77class MachineFrameInfo { 78 79 // StackObject - Represent a single object allocated on the stack. 80 struct StackObject { 81 // SPOffset - The offset of this object from the stack pointer on entry to 82 // the function. This field has no meaning for a variable sized element. 83 int64_t SPOffset; 84 85 // The size of this object on the stack. 0 means a variable sized object, 86 // ~0ULL means a dead object. 87 uint64_t Size; 88 89 // Alignment - The required alignment of this stack slot. 90 unsigned Alignment; 91 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. 95 bool isImmutable; 96 97 // isSpillSlot - If true the stack object is used as spill slot. It 98 // cannot alias any other memory objects. 99 bool isSpillSlot; 100 101 // MayNeedSP - If true the stack object triggered the creation of the stack 102 // protector. We should allocate this object right after the stack 103 // protector. 104 bool MayNeedSP; 105 106 // PreAllocated - If true, the object was mapped into the local frame 107 // block and doesn't need additional handling for allocation beyond that. 108 bool PreAllocated; 109 110 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM, 111 bool isSS, bool NSP) 112 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM), 113 isSpillSlot(isSS), MayNeedSP(NSP), PreAllocated(false) {} 114 }; 115 116 /// Objects - The list of stack objects allocated... 117 /// 118 std::vector<StackObject> Objects; 119 120 /// NumFixedObjects - This contains the number of fixed objects contained on 121 /// the stack. Because fixed objects are stored at a negative index in the 122 /// Objects list, this is also the index to the 0th object in the list. 123 /// 124 unsigned NumFixedObjects; 125 126 /// HasVarSizedObjects - This boolean keeps track of whether any variable 127 /// sized objects have been allocated yet. 128 /// 129 bool HasVarSizedObjects; 130 131 /// FrameAddressTaken - This boolean keeps track of whether there is a call 132 /// to builtin \@llvm.frameaddress. 133 bool FrameAddressTaken; 134 135 /// ReturnAddressTaken - This boolean keeps track of whether there is a call 136 /// to builtin \@llvm.returnaddress. 137 bool ReturnAddressTaken; 138 139 /// StackSize - The prolog/epilog code inserter calculates the final stack 140 /// offsets for all of the fixed size objects, updating the Objects list 141 /// above. It then updates StackSize to contain the number of bytes that need 142 /// to be allocated on entry to the function. 143 /// 144 uint64_t StackSize; 145 146 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to 147 /// have the actual offset from the stack/frame pointer. The exact usage of 148 /// this is target-dependent, but it is typically used to adjust between 149 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via 150 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set 151 /// to the distance between the initial SP and the value in FP. For many 152 /// targets, this value is only used when generating debug info (via 153 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the 154 /// corresponding adjustments are performed directly. 155 int OffsetAdjustment; 156 157 /// MaxAlignment - The prolog/epilog code inserter may process objects 158 /// that require greater alignment than the default alignment the target 159 /// provides. To handle this, MaxAlignment is set to the maximum alignment 160 /// needed by the objects on the current frame. If this is greater than the 161 /// native alignment maintained by the compiler, dynamic alignment code will 162 /// be needed. 163 /// 164 unsigned MaxAlignment; 165 166 /// AdjustsStack - Set to true if this function adjusts the stack -- e.g., 167 /// when calling another function. This is only valid during and after 168 /// prolog/epilog code insertion. 169 bool AdjustsStack; 170 171 /// HasCalls - Set to true if this function has any function calls. 172 bool HasCalls; 173 174 /// StackProtectorIdx - The frame index for the stack protector. 175 int StackProtectorIdx; 176 177 /// FunctionContextIdx - The frame index for the function context. Used for 178 /// SjLj exceptions. 179 int FunctionContextIdx; 180 181 /// MaxCallFrameSize - This contains the size of the largest call frame if the 182 /// target uses frame setup/destroy pseudo instructions (as defined in the 183 /// TargetFrameInfo class). This information is important for frame pointer 184 /// elimination. If is only valid during and after prolog/epilog code 185 /// insertion. 186 /// 187 unsigned MaxCallFrameSize; 188 189 /// CSInfo - The prolog/epilog code inserter fills in this vector with each 190 /// callee saved register saved in the frame. Beyond its use by the prolog/ 191 /// epilog code inserter, this data used for debug info and exception 192 /// handling. 193 std::vector<CalleeSavedInfo> CSInfo; 194 195 /// CSIValid - Has CSInfo been set yet? 196 bool CSIValid; 197 198 /// TargetFrameLowering - Target information about frame layout. 199 /// 200 const TargetFrameLowering &TFI; 201 202 /// LocalFrameObjects - References to frame indices which are mapped 203 /// into the local frame allocation block. <FrameIdx, LocalOffset> 204 SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects; 205 206 /// LocalFrameSize - Size of the pre-allocated local frame block. 207 int64_t LocalFrameSize; 208 209 /// Required alignment of the local object blob, which is the strictest 210 /// alignment of any object in it. 211 unsigned LocalFrameMaxAlign; 212 213 /// Whether the local object blob needs to be allocated together. If not, 214 /// PEI should ignore the isPreAllocated flags on the stack objects and 215 /// just allocate them normally. 216 bool UseLocalStackAllocationBlock; 217 218public: 219 explicit MachineFrameInfo(const TargetFrameLowering &tfi) : TFI(tfi) { 220 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0; 221 HasVarSizedObjects = false; 222 FrameAddressTaken = false; 223 ReturnAddressTaken = false; 224 AdjustsStack = false; 225 HasCalls = false; 226 StackProtectorIdx = -1; 227 FunctionContextIdx = -1; 228 MaxCallFrameSize = 0; 229 CSIValid = false; 230 LocalFrameSize = 0; 231 LocalFrameMaxAlign = 0; 232 UseLocalStackAllocationBlock = false; 233 } 234 235 /// hasStackObjects - Return true if there are any stack objects in this 236 /// function. 237 /// 238 bool hasStackObjects() const { return !Objects.empty(); } 239 240 /// hasVarSizedObjects - This method may be called any time after instruction 241 /// selection is complete to determine if the stack frame for this function 242 /// contains any variable sized objects. 243 /// 244 bool hasVarSizedObjects() const { return HasVarSizedObjects; } 245 246 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the 247 /// stack protector object. 248 /// 249 int getStackProtectorIndex() const { return StackProtectorIdx; } 250 void setStackProtectorIndex(int I) { StackProtectorIdx = I; } 251 252 /// getFunctionContextIndex/setFunctionContextIndex - Return the index for the 253 /// function context object. This object is used for SjLj exceptions. 254 int getFunctionContextIndex() const { return FunctionContextIdx; } 255 void setFunctionContextIndex(int I) { FunctionContextIdx = I; } 256 257 /// isFrameAddressTaken - This method may be called any time after instruction 258 /// selection is complete to determine if there is a call to 259 /// \@llvm.frameaddress in this function. 260 bool isFrameAddressTaken() const { return FrameAddressTaken; } 261 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; } 262 263 /// isReturnAddressTaken - This method may be called any time after 264 /// instruction selection is complete to determine if there is a call to 265 /// \@llvm.returnaddress in this function. 266 bool isReturnAddressTaken() const { return ReturnAddressTaken; } 267 void setReturnAddressIsTaken(bool s) { ReturnAddressTaken = s; } 268 269 /// getObjectIndexBegin - Return the minimum frame object index. 270 /// 271 int getObjectIndexBegin() const { return -NumFixedObjects; } 272 273 /// getObjectIndexEnd - Return one past the maximum frame object index. 274 /// 275 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; } 276 277 /// getNumFixedObjects - Return the number of fixed objects. 278 unsigned getNumFixedObjects() const { return NumFixedObjects; } 279 280 /// getNumObjects - Return the number of objects. 281 /// 282 unsigned getNumObjects() const { return Objects.size(); } 283 284 /// mapLocalFrameObject - Map a frame index into the local object block 285 void mapLocalFrameObject(int ObjectIndex, int64_t Offset) { 286 LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset)); 287 Objects[ObjectIndex + NumFixedObjects].PreAllocated = true; 288 } 289 290 /// getLocalFrameObjectMap - Get the local offset mapping for a for an object 291 std::pair<int, int64_t> getLocalFrameObjectMap(int i) { 292 assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() && 293 "Invalid local object reference!"); 294 return LocalFrameObjects[i]; 295 } 296 297 /// getLocalFrameObjectCount - Return the number of objects allocated into 298 /// the local object block. 299 int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); } 300 301 /// setLocalFrameSize - Set the size of the local object blob. 302 void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; } 303 304 /// getLocalFrameSize - Get the size of the local object blob. 305 int64_t getLocalFrameSize() const { return LocalFrameSize; } 306 307 /// setLocalFrameMaxAlign - Required alignment of the local object blob, 308 /// which is the strictest alignment of any object in it. 309 void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; } 310 311 /// getLocalFrameMaxAlign - Return the required alignment of the local 312 /// object blob. 313 unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; } 314 315 /// getUseLocalStackAllocationBlock - Get whether the local allocation blob 316 /// should be allocated together or let PEI allocate the locals in it 317 /// directly. 318 bool getUseLocalStackAllocationBlock() {return UseLocalStackAllocationBlock;} 319 320 /// setUseLocalStackAllocationBlock - Set whether the local allocation blob 321 /// should be allocated together or let PEI allocate the locals in it 322 /// directly. 323 void setUseLocalStackAllocationBlock(bool v) { 324 UseLocalStackAllocationBlock = v; 325 } 326 327 /// isObjectPreAllocated - Return true if the object was pre-allocated into 328 /// the local block. 329 bool isObjectPreAllocated(int ObjectIdx) const { 330 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 331 "Invalid Object Idx!"); 332 return Objects[ObjectIdx+NumFixedObjects].PreAllocated; 333 } 334 335 /// getObjectSize - Return the size of the specified object. 336 /// 337 int64_t getObjectSize(int ObjectIdx) const { 338 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 339 "Invalid Object Idx!"); 340 return Objects[ObjectIdx+NumFixedObjects].Size; 341 } 342 343 /// setObjectSize - Change the size of the specified stack object. 344 void setObjectSize(int ObjectIdx, int64_t Size) { 345 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 346 "Invalid Object Idx!"); 347 Objects[ObjectIdx+NumFixedObjects].Size = Size; 348 } 349 350 /// getObjectAlignment - Return the alignment of the specified stack object. 351 unsigned getObjectAlignment(int ObjectIdx) const { 352 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 353 "Invalid Object Idx!"); 354 return Objects[ObjectIdx+NumFixedObjects].Alignment; 355 } 356 357 /// setObjectAlignment - Change the alignment of the specified stack object. 358 void setObjectAlignment(int ObjectIdx, unsigned Align) { 359 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 360 "Invalid Object Idx!"); 361 Objects[ObjectIdx+NumFixedObjects].Alignment = Align; 362 ensureMaxAlignment(Align); 363 } 364 365 /// NeedsStackProtector - Returns true if the object may need stack 366 /// protectors. 367 bool MayNeedStackProtector(int ObjectIdx) const { 368 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 369 "Invalid Object Idx!"); 370 return Objects[ObjectIdx+NumFixedObjects].MayNeedSP; 371 } 372 373 /// getObjectOffset - Return the assigned stack offset of the specified object 374 /// from the incoming stack pointer. 375 /// 376 int64_t getObjectOffset(int ObjectIdx) const { 377 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 378 "Invalid Object Idx!"); 379 assert(!isDeadObjectIndex(ObjectIdx) && 380 "Getting frame offset for a dead object?"); 381 return Objects[ObjectIdx+NumFixedObjects].SPOffset; 382 } 383 384 /// setObjectOffset - Set the stack frame offset of the specified object. The 385 /// offset is relative to the stack pointer on entry to the function. 386 /// 387 void setObjectOffset(int ObjectIdx, int64_t SPOffset) { 388 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 389 "Invalid Object Idx!"); 390 assert(!isDeadObjectIndex(ObjectIdx) && 391 "Setting frame offset for a dead object?"); 392 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset; 393 } 394 395 /// getStackSize - Return the number of bytes that must be allocated to hold 396 /// all of the fixed size frame objects. This is only valid after 397 /// Prolog/Epilog code insertion has finalized the stack frame layout. 398 /// 399 uint64_t getStackSize() const { return StackSize; } 400 401 /// setStackSize - Set the size of the stack... 402 /// 403 void setStackSize(uint64_t Size) { StackSize = Size; } 404 405 /// getOffsetAdjustment - Return the correction for frame offsets. 406 /// 407 int getOffsetAdjustment() const { return OffsetAdjustment; } 408 409 /// setOffsetAdjustment - Set the correction for frame offsets. 410 /// 411 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; } 412 413 /// getMaxAlignment - Return the alignment in bytes that this function must be 414 /// aligned to, which is greater than the default stack alignment provided by 415 /// the target. 416 /// 417 unsigned getMaxAlignment() const { return MaxAlignment; } 418 419 /// ensureMaxAlignment - Make sure the function is at least Align bytes 420 /// aligned. 421 void ensureMaxAlignment(unsigned Align) { 422 if (MaxAlignment < Align) MaxAlignment = Align; 423 } 424 425 /// AdjustsStack - Return true if this function adjusts the stack -- e.g., 426 /// when calling another function. This is only valid during and after 427 /// prolog/epilog code insertion. 428 bool adjustsStack() const { return AdjustsStack; } 429 void setAdjustsStack(bool V) { AdjustsStack = V; } 430 431 /// hasCalls - Return true if the current function has any function calls. 432 bool hasCalls() const { return HasCalls; } 433 void setHasCalls(bool V) { HasCalls = V; } 434 435 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be 436 /// allocated for an outgoing function call. This is only available if 437 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and 438 /// then only during or after prolog/epilog code insertion. 439 /// 440 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; } 441 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; } 442 443 /// CreateFixedObject - Create a new object at a fixed location on the stack. 444 /// All fixed objects should be created before other objects are created for 445 /// efficiency. By default, fixed objects are immutable. This returns an 446 /// index with a negative value. 447 /// 448 int CreateFixedObject(uint64_t Size, int64_t SPOffset, bool Immutable); 449 450 451 /// isFixedObjectIndex - Returns true if the specified index corresponds to a 452 /// fixed stack object. 453 bool isFixedObjectIndex(int ObjectIdx) const { 454 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects); 455 } 456 457 /// isImmutableObjectIndex - Returns true if the specified index corresponds 458 /// to an immutable object. 459 bool isImmutableObjectIndex(int ObjectIdx) const { 460 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 461 "Invalid Object Idx!"); 462 return Objects[ObjectIdx+NumFixedObjects].isImmutable; 463 } 464 465 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds 466 /// to a spill slot.. 467 bool isSpillSlotObjectIndex(int ObjectIdx) const { 468 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 469 "Invalid Object Idx!"); 470 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot; 471 } 472 473 /// isDeadObjectIndex - Returns true if the specified index corresponds to 474 /// a dead object. 475 bool isDeadObjectIndex(int ObjectIdx) const { 476 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 477 "Invalid Object Idx!"); 478 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL; 479 } 480 481 /// CreateStackObject - Create a new statically sized stack object, returning 482 /// a nonnegative identifier to represent it. 483 /// 484 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS, 485 bool MayNeedSP = false) { 486 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 487 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS, MayNeedSP)); 488 int Index = (int)Objects.size() - NumFixedObjects - 1; 489 assert(Index >= 0 && "Bad frame index!"); 490 ensureMaxAlignment(Alignment); 491 return Index; 492 } 493 494 /// CreateSpillStackObject - Create a new statically sized stack object that 495 /// represents a spill slot, returning a nonnegative identifier to represent 496 /// it. 497 /// 498 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) { 499 CreateStackObject(Size, Alignment, true, false); 500 int Index = (int)Objects.size() - NumFixedObjects - 1; 501 ensureMaxAlignment(Alignment); 502 return Index; 503 } 504 505 /// RemoveStackObject - Remove or mark dead a statically sized stack object. 506 /// 507 void RemoveStackObject(int ObjectIdx) { 508 // Mark it dead. 509 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL; 510 } 511 512 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a 513 /// variable sized object has been created. This must be created whenever a 514 /// variable sized object is created, whether or not the index returned is 515 /// actually used. 516 /// 517 int CreateVariableSizedObject(unsigned Alignment) { 518 HasVarSizedObjects = true; 519 Objects.push_back(StackObject(0, Alignment, 0, false, false, true)); 520 ensureMaxAlignment(Alignment); 521 return (int)Objects.size()-NumFixedObjects-1; 522 } 523 524 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the 525 /// current function. 526 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const { 527 return CSInfo; 528 } 529 530 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's 531 /// callee saved information. 532 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) { 533 CSInfo = CSI; 534 } 535 536 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet? 537 bool isCalleeSavedInfoValid() const { return CSIValid; } 538 539 void setCalleeSavedInfoValid(bool v) { CSIValid = v; } 540 541 /// getPristineRegs - Return a set of physical registers that are pristine on 542 /// entry to the MBB. 543 /// 544 /// Pristine registers hold a value that is useless to the current function, 545 /// but that must be preserved - they are callee saved registers that have not 546 /// been saved yet. 547 /// 548 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this 549 /// method always returns an empty set. 550 BitVector getPristineRegs(const MachineBasicBlock *MBB) const; 551 552 /// print - Used by the MachineFunction printer to print information about 553 /// stack objects. Implemented in MachineFunction.cpp 554 /// 555 void print(const MachineFunction &MF, raw_ostream &OS) const; 556 557 /// dump - Print the function to stderr. 558 void dump(const MachineFunction &MF) const; 559}; 560 561} // End llvm namespace 562 563#endif 564