MachineFrameInfo.h revision 206274
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/System/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 TargetFrameInfo; 30class BitVector; 31 32/// The CalleeSavedInfo class tracks the information need to locate where a 33/// callee saved register in the current frame. 34class CalleeSavedInfo { 35 unsigned Reg; 36 const TargetRegisterClass *RegClass; 37 int FrameIdx; 38 39public: 40 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0) 41 : Reg(R), RegClass(RC), FrameIdx(FI) {} 42 43 // Accessors. 44 unsigned getReg() const { return Reg; } 45 const TargetRegisterClass *getRegClass() const { return RegClass; } 46 int getFrameIdx() const { return FrameIdx; } 47 void setFrameIdx(int FI) { FrameIdx = FI; } 48}; 49 50/// The MachineFrameInfo class represents an abstract stack frame until 51/// prolog/epilog code is inserted. This class is key to allowing stack frame 52/// representation optimizations, such as frame pointer elimination. It also 53/// allows more mundane (but still important) optimizations, such as reordering 54/// of abstract objects on the stack frame. 55/// 56/// To support this, the class assigns unique integer identifiers to stack 57/// objects requested clients. These identifiers are negative integers for 58/// fixed stack objects (such as arguments passed on the stack) or nonnegative 59/// for objects that may be reordered. Instructions which refer to stack 60/// objects use a special MO_FrameIndex operand to represent these frame 61/// indexes. 62/// 63/// Because this class keeps track of all references to the stack frame, it 64/// knows when a variable sized object is allocated on the stack. This is the 65/// sole condition which prevents frame pointer elimination, which is an 66/// important optimization on register-poor architectures. Because original 67/// variable sized alloca's in the source program are the only source of 68/// variable sized stack objects, it is safe to decide whether there will be 69/// any variable sized objects before all stack objects are known (for 70/// example, register allocator spill code never needs variable sized 71/// objects). 72/// 73/// When prolog/epilog code emission is performed, the final stack frame is 74/// built and the machine instructions are modified to refer to the actual 75/// stack offsets of the object, eliminating all MO_FrameIndex operands from 76/// the program. 77/// 78/// @brief Abstract Stack Frame Information 79class MachineFrameInfo { 80 81 // StackObject - Represent a single object allocated on the stack. 82 struct StackObject { 83 // SPOffset - The offset of this object from the stack pointer on entry to 84 // the function. This field has no meaning for a variable sized element. 85 int64_t SPOffset; 86 87 // The size of this object on the stack. 0 means a variable sized object, 88 // ~0ULL means a dead object. 89 uint64_t Size; 90 91 // Alignment - The required alignment of this stack slot. 92 unsigned Alignment; 93 94 // isImmutable - If true, the value of the stack object is set before 95 // entering the function and is not modified inside the function. By 96 // default, fixed objects are immutable unless marked otherwise. 97 bool isImmutable; 98 99 // isSpillSlot - If true, the stack object is used as spill slot. It 100 // cannot alias any other memory objects. 101 bool isSpillSlot; 102 103 StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM, 104 bool isSS) 105 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM), 106 isSpillSlot(isSS) {} 107 }; 108 109 /// Objects - The list of stack objects allocated... 110 /// 111 std::vector<StackObject> Objects; 112 113 /// 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. 116 /// 117 unsigned NumFixedObjects; 118 119 /// HasVarSizedObjects - This boolean keeps track of whether any variable 120 /// sized objects have been allocated yet. 121 /// 122 bool HasVarSizedObjects; 123 124 /// FrameAddressTaken - This boolean keeps track of whether there is a call 125 /// to builtin \@llvm.frameaddress. 126 bool FrameAddressTaken; 127 128 /// 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. 132 /// 133 uint64_t StackSize; 134 135 /// 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; 145 146 /// 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 151 /// be needed. 152 /// 153 unsigned MaxAlignment; 154 155 /// HasCalls - Set to true if this function has any function calls. This is 156 /// only valid during and after prolog/epilog code insertion. 157 bool HasCalls; 158 159 /// StackProtectorIdx - The frame index for the stack protector. 160 int StackProtectorIdx; 161 162 /// 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 166 /// insertion. 167 /// 168 unsigned MaxCallFrameSize; 169 170 /// 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 173 /// handling. 174 std::vector<CalleeSavedInfo> CSInfo; 175 176 /// CSIValid - Has CSInfo been set yet? 177 bool CSIValid; 178 179 /// SpillObjects - A vector indicating which frame indices refer to 180 /// spill slots. 181 SmallVector<bool, 8> SpillObjects; 182 183 /// TargetFrameInfo - Target information about frame layout. 184 /// 185 const TargetFrameInfo &TFI; 186 187public: 188 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) { 189 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0; 190 HasVarSizedObjects = false; 191 FrameAddressTaken = false; 192 HasCalls = false; 193 StackProtectorIdx = -1; 194 MaxCallFrameSize = 0; 195 CSIValid = false; 196 } 197 198 /// hasStackObjects - Return true if there are any stack objects in this 199 /// function. 200 /// 201 bool hasStackObjects() const { return !Objects.empty(); } 202 203 /// hasVarSizedObjects - This method may be called any time after instruction 204 /// selection is complete to determine if the stack frame for this function 205 /// contains any variable sized objects. 206 /// 207 bool hasVarSizedObjects() const { return HasVarSizedObjects; } 208 209 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the 210 /// stack protector object. 211 /// 212 int getStackProtectorIndex() const { return StackProtectorIdx; } 213 void setStackProtectorIndex(int I) { StackProtectorIdx = I; } 214 215 /// isFrameAddressTaken - This method may be called any time after instruction 216 /// selection is complete to determine if there is a call to 217 /// \@llvm.frameaddress in this function. 218 bool isFrameAddressTaken() const { return FrameAddressTaken; } 219 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; } 220 221 /// getObjectIndexBegin - Return the minimum frame object index. 222 /// 223 int getObjectIndexBegin() const { return -NumFixedObjects; } 224 225 /// getObjectIndexEnd - Return one past the maximum frame object index. 226 /// 227 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; } 228 229 /// getNumFixedObjects() - Return the number of fixed objects. 230 unsigned getNumFixedObjects() const { return NumFixedObjects; } 231 232 /// getNumObjects() - Return the number of objects. 233 /// 234 unsigned getNumObjects() const { return Objects.size(); } 235 236 /// getObjectSize - Return the size of the specified object. 237 /// 238 int64_t getObjectSize(int ObjectIdx) const { 239 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 240 "Invalid Object Idx!"); 241 return Objects[ObjectIdx+NumFixedObjects].Size; 242 } 243 244 /// setObjectSize - Change the size of the specified stack object. 245 void setObjectSize(int ObjectIdx, int64_t Size) { 246 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 247 "Invalid Object Idx!"); 248 Objects[ObjectIdx+NumFixedObjects].Size = Size; 249 } 250 251 /// getObjectAlignment - Return the alignment of the specified stack object. 252 unsigned getObjectAlignment(int ObjectIdx) const { 253 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 254 "Invalid Object Idx!"); 255 return Objects[ObjectIdx+NumFixedObjects].Alignment; 256 } 257 258 /// setObjectAlignment - Change the alignment of the specified stack object. 259 void setObjectAlignment(int ObjectIdx, unsigned Align) { 260 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 261 "Invalid Object Idx!"); 262 Objects[ObjectIdx+NumFixedObjects].Alignment = Align; 263 MaxAlignment = std::max(MaxAlignment, Align); 264 } 265 266 /// getObjectOffset - Return the assigned stack offset of the specified object 267 /// from the incoming stack pointer. 268 /// 269 int64_t getObjectOffset(int ObjectIdx) const { 270 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 271 "Invalid Object Idx!"); 272 assert(!isDeadObjectIndex(ObjectIdx) && 273 "Getting frame offset for a dead object?"); 274 return Objects[ObjectIdx+NumFixedObjects].SPOffset; 275 } 276 277 /// setObjectOffset - Set the stack frame offset of the specified object. The 278 /// offset is relative to the stack pointer on entry to the function. 279 /// 280 void setObjectOffset(int ObjectIdx, int64_t SPOffset) { 281 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 282 "Invalid Object Idx!"); 283 assert(!isDeadObjectIndex(ObjectIdx) && 284 "Setting frame offset for a dead object?"); 285 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset; 286 } 287 288 /// getStackSize - Return the number of bytes that must be allocated to hold 289 /// all of the fixed size frame objects. This is only valid after 290 /// Prolog/Epilog code insertion has finalized the stack frame layout. 291 /// 292 uint64_t getStackSize() const { return StackSize; } 293 294 /// setStackSize - Set the size of the stack... 295 /// 296 void setStackSize(uint64_t Size) { StackSize = Size; } 297 298 /// getOffsetAdjustment - Return the correction for frame offsets. 299 /// 300 int getOffsetAdjustment() const { return OffsetAdjustment; } 301 302 /// setOffsetAdjustment - Set the correction for frame offsets. 303 /// 304 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; } 305 306 /// getMaxAlignment - Return the alignment in bytes that this function must be 307 /// aligned to, which is greater than the default stack alignment provided by 308 /// the target. 309 /// 310 unsigned getMaxAlignment() const { return MaxAlignment; } 311 312 /// setMaxAlignment - Set the preferred alignment. 313 /// 314 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; } 315 316 /// hasCalls - Return true if the current function has no function calls. 317 /// This is only valid during or after prolog/epilog code emission. 318 /// 319 bool hasCalls() const { return HasCalls; } 320 void setHasCalls(bool V) { HasCalls = V; } 321 322 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be 323 /// allocated for an outgoing function call. This is only available if 324 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and 325 /// then only during or after prolog/epilog code insertion. 326 /// 327 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; } 328 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; } 329 330 /// CreateFixedObject - Create a new object at a fixed location on the stack. 331 /// All fixed objects should be created before other objects are created for 332 /// efficiency. By default, fixed objects are immutable. This returns an 333 /// index with a negative value. 334 /// 335 int CreateFixedObject(uint64_t Size, int64_t SPOffset, 336 bool Immutable, bool isSS); 337 338 339 /// isFixedObjectIndex - Returns true if the specified index corresponds to a 340 /// fixed stack object. 341 bool isFixedObjectIndex(int ObjectIdx) const { 342 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects); 343 } 344 345 /// isImmutableObjectIndex - Returns true if the specified index corresponds 346 /// to an immutable object. 347 bool isImmutableObjectIndex(int ObjectIdx) const { 348 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 349 "Invalid Object Idx!"); 350 return Objects[ObjectIdx+NumFixedObjects].isImmutable; 351 } 352 353 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds 354 /// to a spill slot.. 355 bool isSpillSlotObjectIndex(int ObjectIdx) const { 356 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 357 "Invalid Object Idx!"); 358 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;; 359 } 360 361 /// isDeadObjectIndex - Returns true if the specified index corresponds to 362 /// a dead object. 363 bool isDeadObjectIndex(int ObjectIdx) const { 364 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 365 "Invalid Object Idx!"); 366 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL; 367 } 368 369 /// CreateStackObject - Create a new statically sized stack object, 370 /// returning a nonnegative identifier to represent it. 371 /// 372 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS) { 373 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 374 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS)); 375 int Index = (int)Objects.size()-NumFixedObjects-1; 376 assert(Index >= 0 && "Bad frame index!"); 377 MaxAlignment = std::max(MaxAlignment, Alignment); 378 return Index; 379 } 380 381 /// CreateSpillStackObject - Create a new statically sized stack 382 /// object that represents a spill slot, returning a nonnegative 383 /// identifier to represent it. 384 /// 385 int CreateSpillStackObject(uint64_t Size, unsigned Alignment) { 386 CreateStackObject(Size, Alignment, true); 387 int Index = (int)Objects.size()-NumFixedObjects-1; 388 MaxAlignment = std::max(MaxAlignment, Alignment); 389 return Index; 390 } 391 392 /// RemoveStackObject - Remove or mark dead a statically sized stack object. 393 /// 394 void RemoveStackObject(int ObjectIdx) { 395 // Mark it dead. 396 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL; 397 } 398 399 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a 400 /// variable sized object has been created. This must be created whenever a 401 /// variable sized object is created, whether or not the index returned is 402 /// actually used. 403 /// 404 int CreateVariableSizedObject() { 405 HasVarSizedObjects = true; 406 Objects.push_back(StackObject(0, 1, 0, false, false)); 407 return (int)Objects.size()-NumFixedObjects-1; 408 } 409 410 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the 411 /// current function. 412 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const { 413 return CSInfo; 414 } 415 416 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's 417 /// callee saved information. 418 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) { 419 CSInfo = CSI; 420 } 421 422 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet? 423 bool isCalleeSavedInfoValid() const { return CSIValid; } 424 425 void setCalleeSavedInfoValid(bool v) { CSIValid = v; } 426 427 /// getPristineRegs - Return a set of physical registers that are pristine on 428 /// entry to the MBB. 429 /// 430 /// Pristine registers hold a value that is useless to the current function, 431 /// but that must be preserved - they are callee saved registers that have not 432 /// been saved yet. 433 /// 434 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this 435 /// method always returns an empty set. 436 BitVector getPristineRegs(const MachineBasicBlock *MBB) const; 437 438 /// print - Used by the MachineFunction printer to print information about 439 /// stack objects. Implemented in MachineFunction.cpp 440 /// 441 void print(const MachineFunction &MF, raw_ostream &OS) const; 442 443 /// dump - Print the function to stderr. 444 void dump(const MachineFunction &MF) const; 445}; 446 447} // End llvm namespace 448 449#endif 450