MachineFrameInfo.h revision 200581
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 } 280 281 /// getObjectOffset - Return the assigned stack offset of the specified object 282 /// from the incoming stack pointer. 283 /// 284 int64_t getObjectOffset(int ObjectIdx) const { 285 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 286 "Invalid Object Idx!"); 287 assert(!isDeadObjectIndex(ObjectIdx) && 288 "Getting frame offset for a dead object?"); 289 return Objects[ObjectIdx+NumFixedObjects].SPOffset; 290 } 291 292 /// setObjectOffset - Set the stack frame offset of the specified object. The 293 /// offset is relative to the stack pointer on entry to the function. 294 /// 295 void setObjectOffset(int ObjectIdx, int64_t SPOffset) { 296 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 297 "Invalid Object Idx!"); 298 assert(!isDeadObjectIndex(ObjectIdx) && 299 "Setting frame offset for a dead object?"); 300 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset; 301 } 302 303 /// getStackSize - Return the number of bytes that must be allocated to hold 304 /// all of the fixed size frame objects. This is only valid after 305 /// Prolog/Epilog code insertion has finalized the stack frame layout. 306 /// 307 uint64_t getStackSize() const { return StackSize; } 308 309 /// setStackSize - Set the size of the stack... 310 /// 311 void setStackSize(uint64_t Size) { StackSize = Size; } 312 313 /// getOffsetAdjustment - Return the correction for frame offsets. 314 /// 315 int getOffsetAdjustment() const { return OffsetAdjustment; } 316 317 /// setOffsetAdjustment - Set the correction for frame offsets. 318 /// 319 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; } 320 321 /// getMaxAlignment - Return the alignment in bytes that this function must be 322 /// aligned to, which is greater than the default stack alignment provided by 323 /// the target. 324 /// 325 unsigned getMaxAlignment() const { return MaxAlignment; } 326 327 /// setMaxAlignment - Set the preferred alignment. 328 /// 329 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; } 330 331 /// calculateMaxStackAlignment() - If there is a local object which requires 332 /// greater alignment than the current max alignment, adjust accordingly. 333 void calculateMaxStackAlignment() { 334 for (int i = getObjectIndexBegin(), 335 e = getObjectIndexEnd(); i != e; ++i) { 336 if (isDeadObjectIndex(i)) 337 continue; 338 339 unsigned Align = getObjectAlignment(i); 340 MaxAlignment = std::max(MaxAlignment, Align); 341 } 342 } 343 344 /// hasCalls - Return true if the current function has no function calls. 345 /// This is only valid during or after prolog/epilog code emission. 346 /// 347 bool hasCalls() const { return HasCalls; } 348 void setHasCalls(bool V) { HasCalls = V; } 349 350 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be 351 /// allocated for an outgoing function call. This is only available if 352 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and 353 /// then only during or after prolog/epilog code insertion. 354 /// 355 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; } 356 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; } 357 358 /// CreateFixedObject - Create a new object at a fixed location on the stack. 359 /// All fixed objects should be created before other objects are created for 360 /// efficiency. By default, fixed objects are immutable. This returns an 361 /// index with a negative value. 362 /// 363 int CreateFixedObject(uint64_t Size, int64_t SPOffset, 364 bool Immutable, bool isSS); 365 366 367 /// isFixedObjectIndex - Returns true if the specified index corresponds to a 368 /// fixed stack object. 369 bool isFixedObjectIndex(int ObjectIdx) const { 370 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects); 371 } 372 373 /// isImmutableObjectIndex - Returns true if the specified index corresponds 374 /// to an immutable object. 375 bool isImmutableObjectIndex(int ObjectIdx) const { 376 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 377 "Invalid Object Idx!"); 378 return Objects[ObjectIdx+NumFixedObjects].isImmutable; 379 } 380 381 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds 382 /// to a spill slot.. 383 bool isSpillSlotObjectIndex(int ObjectIdx) const { 384 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 385 "Invalid Object Idx!"); 386 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;; 387 } 388 389 /// isDeadObjectIndex - Returns true if the specified index corresponds to 390 /// a dead object. 391 bool isDeadObjectIndex(int ObjectIdx) const { 392 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 393 "Invalid Object Idx!"); 394 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL; 395 } 396 397 /// CreateStackObject - Create a new statically sized stack object, 398 /// returning a nonnegative identifier to represent it. 399 /// 400 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS) { 401 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 402 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS)); 403 int Index = (int)Objects.size()-NumFixedObjects-1; 404 assert(Index >= 0 && "Bad frame index!"); 405 return Index; 406 } 407 408 /// CreateSpillStackObject - Create a new statically sized stack 409 /// object that represents a spill slot, returning a nonnegative 410 /// identifier to represent it. 411 /// 412 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) { 413 CreateStackObject(Size, Alignment, true); 414 int Index = (int)Objects.size()-NumFixedObjects-1; 415 return Index; 416 } 417 418 /// RemoveStackObject - Remove or mark dead a statically sized stack object. 419 /// 420 void RemoveStackObject(int ObjectIdx) { 421 // Mark it dead. 422 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL; 423 } 424 425 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a 426 /// variable sized object has been created. This must be created whenever a 427 /// variable sized object is created, whether or not the index returned is 428 /// actually used. 429 /// 430 int CreateVariableSizedObject() { 431 HasVarSizedObjects = true; 432 Objects.push_back(StackObject(0, 1, 0, false, false)); 433 return (int)Objects.size()-NumFixedObjects-1; 434 } 435 436 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the 437 /// current function. 438 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const { 439 return CSInfo; 440 } 441 442 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's 443 /// callee saved information. 444 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) { 445 CSInfo = CSI; 446 } 447 448 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet? 449 bool isCalleeSavedInfoValid() const { return CSIValid; } 450 451 void setCalleeSavedInfoValid(bool v) { CSIValid = v; } 452 453 /// getPristineRegs - Return a set of physical registers that are pristine on 454 /// entry to the MBB. 455 /// 456 /// Pristine registers hold a value that is useless to the current function, 457 /// but that must be preserved - they are callee saved registers that have not 458 /// been saved yet. 459 /// 460 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this 461 /// method always returns an empty set. 462 BitVector getPristineRegs(const MachineBasicBlock *MBB) const; 463 464 /// getMachineModuleInfo - Used by a prologue/epilogue 465 /// emitter (TargetRegisterInfo) to provide frame layout information. 466 MachineModuleInfo *getMachineModuleInfo() const { return MMI; } 467 468 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to 469 /// indicate that frame layout information should be gathered. 470 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; } 471 472 /// print - Used by the MachineFunction printer to print information about 473 /// stack objects. Implemented in MachineFunction.cpp 474 /// 475 void print(const MachineFunction &MF, raw_ostream &OS) const; 476 477 /// dump - Print the function to stderr. 478 void dump(const MachineFunction &MF) const; 479}; 480 481} // End llvm namespace 482 483#endif 484