MachineFrameInfo.h revision 198892
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/DenseSet.h" 19#include "llvm/System/DataTypes.h" 20#include <cassert> 21#include <vector> 22 23namespace llvm { 24class raw_ostream; 25class TargetData; 26class TargetRegisterClass; 27class Type; 28class MachineModuleInfo; 29class MachineFunction; 30class MachineBasicBlock; 31class TargetFrameInfo; 32 33/// The CalleeSavedInfo class tracks the information need to locate where a 34/// callee saved register in the current frame. 35class CalleeSavedInfo { 36 37private: 38 unsigned Reg; 39 const TargetRegisterClass *RegClass; 40 int FrameIdx; 41 42public: 43 CalleeSavedInfo(unsigned R, const TargetRegisterClass *RC, int FI = 0) 44 : Reg(R) 45 , RegClass(RC) 46 , FrameIdx(FI) 47 {} 48 49 // Accessors. 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; } 54}; 55 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. 61/// 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 67/// indexes. 68/// 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 77/// objects). 78/// 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 82/// the program. 83/// 84/// @brief Abstract Stack Frame Information 85class MachineFrameInfo { 86 87 // StackObject - Represent a single object allocated on the stack. 88 struct StackObject { 89 // SPOffset - The offset of this object from the stack pointer on entry to 90 // the function. This field has no meaning for a variable sized element. 91 int64_t SPOffset; 92 93 // The size of this object on the stack. 0 means a variable sized object, 94 // ~0ULL means a dead object. 95 uint64_t Size; 96 97 // Alignment - The required alignment of this stack slot. 98 unsigned Alignment; 99 100 // isImmutable - If true, the value of the stack object is set before 101 // entering the function and is not modified inside the function. By 102 // default, fixed objects are immutable unless marked otherwise. 103 bool isImmutable; 104 105 // isSpillSlot - If true, the stack object is used as spill slot. It 106 // cannot alias any other memory objects. 107 bool isSpillSlot; 108 109 StackObject(uint64_t Sz, unsigned Al, int64_t SP = 0, bool IM = false, 110 bool isSS = false) 111 : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM), 112 isSpillSlot(isSS) {} 113 }; 114 115 /// Objects - The list of stack objects allocated... 116 /// 117 std::vector<StackObject> Objects; 118 119 /// NumFixedObjects - This contains the number of fixed objects contained on 120 /// the stack. Because fixed objects are stored at a negative index in the 121 /// Objects list, this is also the index to the 0th object in the list. 122 /// 123 unsigned NumFixedObjects; 124 125 /// HasVarSizedObjects - This boolean keeps track of whether any variable 126 /// sized objects have been allocated yet. 127 /// 128 bool HasVarSizedObjects; 129 130 /// FrameAddressTaken - This boolean keeps track of whether there is a call 131 /// to builtin \@llvm.frameaddress. 132 bool FrameAddressTaken; 133 134 /// StackSize - The prolog/epilog code inserter calculates the final stack 135 /// offsets for all of the fixed size objects, updating the Objects list 136 /// above. It then updates StackSize to contain the number of bytes that need 137 /// to be allocated on entry to the function. 138 /// 139 uint64_t StackSize; 140 141 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to 142 /// have the actual offset from the stack/frame pointer. The exact usage of 143 /// this is target-dependent, but it is typically used to adjust between 144 /// SP-relative and FP-relative offsets. E.G., if objects are accessed via 145 /// SP then OffsetAdjustment is zero; if FP is used, OffsetAdjustment is set 146 /// to the distance between the initial SP and the value in FP. For many 147 /// targets, this value is only used when generating debug info (via 148 /// TargetRegisterInfo::getFrameIndexOffset); when generating code, the 149 /// corresponding adjustments are performed directly. 150 int OffsetAdjustment; 151 152 /// MaxAlignment - The prolog/epilog code inserter may process objects 153 /// that require greater alignment than the default alignment the target 154 /// provides. To handle this, MaxAlignment is set to the maximum alignment 155 /// needed by the objects on the current frame. If this is greater than the 156 /// native alignment maintained by the compiler, dynamic alignment code will 157 /// be needed. 158 /// 159 unsigned MaxAlignment; 160 161 /// HasCalls - Set to true if this function has any function calls. This is 162 /// only valid during and after prolog/epilog code insertion. 163 bool HasCalls; 164 165 /// StackProtectorIdx - The frame index for the stack protector. 166 int StackProtectorIdx; 167 168 /// MaxCallFrameSize - This contains the size of the largest call frame if the 169 /// target uses frame setup/destroy pseudo instructions (as defined in the 170 /// TargetFrameInfo class). This information is important for frame pointer 171 /// elimination. If is only valid during and after prolog/epilog code 172 /// insertion. 173 /// 174 unsigned MaxCallFrameSize; 175 176 /// CSInfo - The prolog/epilog code inserter fills in this vector with each 177 /// callee saved register saved in the frame. Beyond its use by the prolog/ 178 /// epilog code inserter, this data used for debug info and exception 179 /// handling. 180 std::vector<CalleeSavedInfo> CSInfo; 181 182 /// CSIValid - Has CSInfo been set yet? 183 bool CSIValid; 184 185 /// MMI - This field is set (via setMachineModuleInfo) by a module info 186 /// consumer (ex. DwarfWriter) to indicate that frame layout information 187 /// should be acquired. Typically, it's the responsibility of the target's 188 /// TargetRegisterInfo prologue/epilogue emitting code to inform 189 /// MachineModuleInfo of frame layouts. 190 MachineModuleInfo *MMI; 191 192 /// TargetFrameInfo - Target information about frame layout. 193 /// 194 const TargetFrameInfo &TFI; 195public: 196 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) { 197 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0; 198 HasVarSizedObjects = false; 199 FrameAddressTaken = false; 200 HasCalls = false; 201 StackProtectorIdx = -1; 202 MaxCallFrameSize = 0; 203 CSIValid = false; 204 MMI = 0; 205 } 206 207 /// hasStackObjects - Return true if there are any stack objects in this 208 /// function. 209 /// 210 bool hasStackObjects() const { return !Objects.empty(); } 211 212 /// hasVarSizedObjects - This method may be called any time after instruction 213 /// selection is complete to determine if the stack frame for this function 214 /// contains any variable sized objects. 215 /// 216 bool hasVarSizedObjects() const { return HasVarSizedObjects; } 217 218 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the 219 /// stack protector object. 220 /// 221 int getStackProtectorIndex() const { return StackProtectorIdx; } 222 void setStackProtectorIndex(int I) { StackProtectorIdx = I; } 223 224 /// isFrameAddressTaken - This method may be called any time after instruction 225 /// selection is complete to determine if there is a call to 226 /// \@llvm.frameaddress in this function. 227 bool isFrameAddressTaken() const { return FrameAddressTaken; } 228 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; } 229 230 /// getObjectIndexBegin - Return the minimum frame object index. 231 /// 232 int getObjectIndexBegin() const { return -NumFixedObjects; } 233 234 /// getObjectIndexEnd - Return one past the maximum frame object index. 235 /// 236 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; } 237 238 /// getNumFixedObjects() - Return the number of fixed objects. 239 unsigned getNumFixedObjects() const { return NumFixedObjects; } 240 241 /// getNumObjects() - Return the number of objects. 242 /// 243 unsigned getNumObjects() const { return Objects.size(); } 244 245 /// getObjectSize - Return the size of the specified object. 246 /// 247 int64_t getObjectSize(int ObjectIdx) const { 248 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 249 "Invalid Object Idx!"); 250 return Objects[ObjectIdx+NumFixedObjects].Size; 251 } 252 253 /// setObjectSize - Change the size of the specified stack object. 254 void setObjectSize(int ObjectIdx, int64_t Size) { 255 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 256 "Invalid Object Idx!"); 257 Objects[ObjectIdx+NumFixedObjects].Size = Size; 258 } 259 260 /// getObjectAlignment - Return the alignment of the specified stack object. 261 unsigned getObjectAlignment(int ObjectIdx) const { 262 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 263 "Invalid Object Idx!"); 264 return Objects[ObjectIdx+NumFixedObjects].Alignment; 265 } 266 267 /// setObjectAlignment - Change the alignment of the specified stack object. 268 void setObjectAlignment(int ObjectIdx, unsigned Align) { 269 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 270 "Invalid Object Idx!"); 271 Objects[ObjectIdx+NumFixedObjects].Alignment = Align; 272 } 273 274 /// getObjectOffset - Return the assigned stack offset of the specified object 275 /// from the incoming stack pointer. 276 /// 277 int64_t getObjectOffset(int ObjectIdx) const { 278 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 279 "Invalid Object Idx!"); 280 assert(!isDeadObjectIndex(ObjectIdx) && 281 "Getting frame offset for a dead object?"); 282 return Objects[ObjectIdx+NumFixedObjects].SPOffset; 283 } 284 285 /// setObjectOffset - Set the stack frame offset of the specified object. The 286 /// offset is relative to the stack pointer on entry to the function. 287 /// 288 void setObjectOffset(int ObjectIdx, int64_t SPOffset) { 289 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 290 "Invalid Object Idx!"); 291 assert(!isDeadObjectIndex(ObjectIdx) && 292 "Setting frame offset for a dead object?"); 293 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset; 294 } 295 296 /// getStackSize - Return the number of bytes that must be allocated to hold 297 /// all of the fixed size frame objects. This is only valid after 298 /// Prolog/Epilog code insertion has finalized the stack frame layout. 299 /// 300 uint64_t getStackSize() const { return StackSize; } 301 302 /// setStackSize - Set the size of the stack... 303 /// 304 void setStackSize(uint64_t Size) { StackSize = Size; } 305 306 /// getOffsetAdjustment - Return the correction for frame offsets. 307 /// 308 int getOffsetAdjustment() const { return OffsetAdjustment; } 309 310 /// setOffsetAdjustment - Set the correction for frame offsets. 311 /// 312 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; } 313 314 /// getMaxAlignment - Return the alignment in bytes that this function must be 315 /// aligned to, which is greater than the default stack alignment provided by 316 /// the target. 317 /// 318 unsigned getMaxAlignment() const { return MaxAlignment; } 319 320 /// setMaxAlignment - Set the preferred alignment. 321 /// 322 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; } 323 324 /// hasCalls - Return true if the current function has no function calls. 325 /// This is only valid during or after prolog/epilog code emission. 326 /// 327 bool hasCalls() const { return HasCalls; } 328 void setHasCalls(bool V) { HasCalls = V; } 329 330 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be 331 /// allocated for an outgoing function call. This is only available if 332 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and 333 /// then only during or after prolog/epilog code insertion. 334 /// 335 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; } 336 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; } 337 338 /// CreateFixedObject - Create a new object at a fixed location on the stack. 339 /// All fixed objects should be created before other objects are created for 340 /// efficiency. By default, fixed objects are immutable. This returns an 341 /// index with a negative value. 342 /// 343 int CreateFixedObject(uint64_t Size, int64_t SPOffset, 344 bool Immutable = true); 345 346 347 /// isFixedObjectIndex - Returns true if the specified index corresponds to a 348 /// fixed stack object. 349 bool isFixedObjectIndex(int ObjectIdx) const { 350 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects); 351 } 352 353 /// isImmutableObjectIndex - Returns true if the specified index corresponds 354 /// to an immutable object. 355 bool isImmutableObjectIndex(int ObjectIdx) const { 356 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 357 "Invalid Object Idx!"); 358 return Objects[ObjectIdx+NumFixedObjects].isImmutable; 359 } 360 361 /// isSpillSlotObjectIndex - Returns true if the specified index corresponds 362 /// to a spill slot.. 363 bool isSpillSlotObjectIndex(int ObjectIdx) const { 364 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 365 "Invalid Object Idx!"); 366 return Objects[ObjectIdx+NumFixedObjects].isSpillSlot;; 367 } 368 369 /// isDeadObjectIndex - Returns true if the specified index corresponds to 370 /// a dead object. 371 bool isDeadObjectIndex(int ObjectIdx) const { 372 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 373 "Invalid Object Idx!"); 374 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL; 375 } 376 377 /// CreateStackObject - Create a new statically sized stack object, returning 378 /// a nonnegative identifier to represent it. 379 /// 380 int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSS = false) { 381 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 382 Objects.push_back(StackObject(Size, Alignment, 0, false, isSS)); 383 return (int)Objects.size()-NumFixedObjects-1; 384 } 385 386 /// RemoveStackObject - Remove or mark dead a statically sized stack object. 387 /// 388 void RemoveStackObject(int ObjectIdx) { 389 // Mark it dead. 390 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL; 391 } 392 393 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a 394 /// variable sized object has been created. This must be created whenever a 395 /// variable sized object is created, whether or not the index returned is 396 /// actually used. 397 /// 398 int CreateVariableSizedObject() { 399 HasVarSizedObjects = true; 400 Objects.push_back(StackObject(0, 1)); 401 return (int)Objects.size()-NumFixedObjects-1; 402 } 403 404 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the 405 /// current function. 406 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const { 407 return CSInfo; 408 } 409 410 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's 411 /// callee saved information. 412 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) { 413 CSInfo = CSI; 414 } 415 416 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet? 417 bool isCalleeSavedInfoValid() const { return CSIValid; } 418 419 void setCalleeSavedInfoValid(bool v) { CSIValid = v; } 420 421 /// getPristineRegs - Return a set of physical registers that are pristine on 422 /// entry to the MBB. 423 /// 424 /// Pristine registers hold a value that is useless to the current function, 425 /// but that must be preserved - they are callee saved registers that have not 426 /// been saved yet. 427 /// 428 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this 429 /// method always returns an empty set. 430 BitVector getPristineRegs(const MachineBasicBlock *MBB) const; 431 432 /// getMachineModuleInfo - Used by a prologue/epilogue 433 /// emitter (TargetRegisterInfo) to provide frame layout information. 434 MachineModuleInfo *getMachineModuleInfo() const { return MMI; } 435 436 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to 437 /// indicate that frame layout information should be gathered. 438 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; } 439 440 /// print - Used by the MachineFunction printer to print information about 441 /// stack objects. Implemented in MachineFunction.cpp 442 /// 443 void print(const MachineFunction &MF, raw_ostream &OS) const; 444 445 /// dump - Print the function to stderr. 446 void dump(const MachineFunction &MF) const; 447}; 448 449} // End llvm namespace 450 451#endif 452