MachineFrameInfo.h revision 198090
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/Support/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 // The size of this object on the stack. 0 means a variable sized object, 90 // ~0ULL means a dead object. 91 uint64_t Size; 92 93 // Alignment - The required alignment of this stack slot. 94 unsigned Alignment; 95 96 // isImmutable - If true, the value of the stack object is set before 97 // entering the function and is not modified inside the function. By 98 // default, fixed objects are immutable unless marked otherwise. 99 bool isImmutable; 100 101 // SPOffset - The offset of this object from the stack pointer on entry to 102 // the function. This field has no meaning for a variable sized element. 103 int64_t SPOffset; 104 105 StackObject(uint64_t Sz, unsigned Al, int64_t SP = 0, bool IM = false) 106 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {} 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 /// MMI - This field is set (via setMachineModuleInfo) by a module info 180 /// consumer (ex. DwarfWriter) to indicate that frame layout information 181 /// should be acquired. Typically, it's the responsibility of the target's 182 /// TargetRegisterInfo prologue/epilogue emitting code to inform 183 /// MachineModuleInfo of frame layouts. 184 MachineModuleInfo *MMI; 185 186 /// TargetFrameInfo - Target information about frame layout. 187 /// 188 const TargetFrameInfo &TFI; 189public: 190 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) { 191 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0; 192 HasVarSizedObjects = false; 193 FrameAddressTaken = false; 194 HasCalls = false; 195 StackProtectorIdx = -1; 196 MaxCallFrameSize = 0; 197 CSIValid = false; 198 MMI = 0; 199 } 200 201 /// hasStackObjects - Return true if there are any stack objects in this 202 /// function. 203 /// 204 bool hasStackObjects() const { return !Objects.empty(); } 205 206 /// hasVarSizedObjects - This method may be called any time after instruction 207 /// selection is complete to determine if the stack frame for this function 208 /// contains any variable sized objects. 209 /// 210 bool hasVarSizedObjects() const { return HasVarSizedObjects; } 211 212 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the 213 /// stack protector object. 214 /// 215 int getStackProtectorIndex() const { return StackProtectorIdx; } 216 void setStackProtectorIndex(int I) { StackProtectorIdx = I; } 217 218 /// isFrameAddressTaken - This method may be called any time after instruction 219 /// selection is complete to determine if there is a call to 220 /// \@llvm.frameaddress in this function. 221 bool isFrameAddressTaken() const { return FrameAddressTaken; } 222 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; } 223 224 /// getObjectIndexBegin - Return the minimum frame object index. 225 /// 226 int getObjectIndexBegin() const { return -NumFixedObjects; } 227 228 /// getObjectIndexEnd - Return one past the maximum frame object index. 229 /// 230 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; } 231 232 /// getNumFixedObjects() - Return the number of fixed objects. 233 unsigned getNumFixedObjects() const { return NumFixedObjects; } 234 235 /// getNumObjects() - Return the number of objects. 236 /// 237 unsigned getNumObjects() const { return Objects.size(); } 238 239 /// getObjectSize - Return the size of the specified object. 240 /// 241 int64_t getObjectSize(int ObjectIdx) const { 242 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 243 "Invalid Object Idx!"); 244 return Objects[ObjectIdx+NumFixedObjects].Size; 245 } 246 247 /// setObjectSize - Change the size of the specified stack object. 248 void setObjectSize(int ObjectIdx, int64_t Size) { 249 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 250 "Invalid Object Idx!"); 251 Objects[ObjectIdx+NumFixedObjects].Size = Size; 252 } 253 254 /// getObjectAlignment - Return the alignment of the specified stack object. 255 unsigned getObjectAlignment(int ObjectIdx) const { 256 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 257 "Invalid Object Idx!"); 258 return Objects[ObjectIdx+NumFixedObjects].Alignment; 259 } 260 261 /// setObjectAlignment - Change the alignment of the specified stack object. 262 void setObjectAlignment(int ObjectIdx, unsigned Align) { 263 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 264 "Invalid Object Idx!"); 265 Objects[ObjectIdx+NumFixedObjects].Alignment = Align; 266 } 267 268 /// getObjectOffset - Return the assigned stack offset of the specified object 269 /// from the incoming stack pointer. 270 /// 271 int64_t getObjectOffset(int ObjectIdx) const { 272 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 273 "Invalid Object Idx!"); 274 assert(!isDeadObjectIndex(ObjectIdx) && 275 "Getting frame offset for a dead object?"); 276 return Objects[ObjectIdx+NumFixedObjects].SPOffset; 277 } 278 279 /// setObjectOffset - Set the stack frame offset of the specified object. The 280 /// offset is relative to the stack pointer on entry to the function. 281 /// 282 void setObjectOffset(int ObjectIdx, int64_t SPOffset) { 283 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 284 "Invalid Object Idx!"); 285 assert(!isDeadObjectIndex(ObjectIdx) && 286 "Setting frame offset for a dead object?"); 287 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset; 288 } 289 290 /// getStackSize - Return the number of bytes that must be allocated to hold 291 /// all of the fixed size frame objects. This is only valid after 292 /// Prolog/Epilog code insertion has finalized the stack frame layout. 293 /// 294 uint64_t getStackSize() const { return StackSize; } 295 296 /// setStackSize - Set the size of the stack... 297 /// 298 void setStackSize(uint64_t Size) { StackSize = Size; } 299 300 /// getOffsetAdjustment - Return the correction for frame offsets. 301 /// 302 int getOffsetAdjustment() const { return OffsetAdjustment; } 303 304 /// setOffsetAdjustment - Set the correction for frame offsets. 305 /// 306 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; } 307 308 /// getMaxAlignment - Return the alignment in bytes that this function must be 309 /// aligned to, which is greater than the default stack alignment provided by 310 /// the target. 311 /// 312 unsigned getMaxAlignment() const { return MaxAlignment; } 313 314 /// setMaxAlignment - Set the preferred alignment. 315 /// 316 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; } 317 318 /// hasCalls - Return true if the current function has no function calls. 319 /// This is only valid during or after prolog/epilog code emission. 320 /// 321 bool hasCalls() const { return HasCalls; } 322 void setHasCalls(bool V) { HasCalls = V; } 323 324 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be 325 /// allocated for an outgoing function call. This is only available if 326 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and 327 /// then only during or after prolog/epilog code insertion. 328 /// 329 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; } 330 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; } 331 332 /// CreateFixedObject - Create a new object at a fixed location on the stack. 333 /// All fixed objects should be created before other objects are created for 334 /// efficiency. By default, fixed objects are immutable. This returns an 335 /// index with a negative value. 336 /// 337 int CreateFixedObject(uint64_t Size, int64_t SPOffset, 338 bool Immutable = true); 339 340 341 /// isFixedObjectIndex - Returns true if the specified index corresponds to a 342 /// fixed stack object. 343 bool isFixedObjectIndex(int ObjectIdx) const { 344 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects); 345 } 346 347 /// isImmutableObjectIndex - Returns true if the specified index corresponds 348 /// to an immutable object. 349 bool isImmutableObjectIndex(int ObjectIdx) const { 350 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 351 "Invalid Object Idx!"); 352 return Objects[ObjectIdx+NumFixedObjects].isImmutable; 353 } 354 355 /// isDeadObjectIndex - Returns true if the specified index corresponds to 356 /// a dead object. 357 bool isDeadObjectIndex(int ObjectIdx) const { 358 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 359 "Invalid Object Idx!"); 360 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL; 361 } 362 363 /// CreateStackObject - Create a new statically sized stack object, returning 364 /// a nonnegative identifier to represent it. 365 /// 366 int CreateStackObject(uint64_t Size, unsigned Alignment) { 367 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 368 Objects.push_back(StackObject(Size, Alignment)); 369 return (int)Objects.size()-NumFixedObjects-1; 370 } 371 372 /// RemoveStackObject - Remove or mark dead a statically sized stack object. 373 /// 374 void RemoveStackObject(int ObjectIdx) { 375 // Mark it dead. 376 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL; 377 } 378 379 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a 380 /// variable sized object has been created. This must be created whenever a 381 /// variable sized object is created, whether or not the index returned is 382 /// actually used. 383 /// 384 int CreateVariableSizedObject() { 385 HasVarSizedObjects = true; 386 Objects.push_back(StackObject(0, 1)); 387 return (int)Objects.size()-NumFixedObjects-1; 388 } 389 390 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the 391 /// current function. 392 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const { 393 return CSInfo; 394 } 395 396 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's 397 /// callee saved information. 398 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) { 399 CSInfo = CSI; 400 } 401 402 /// isCalleeSavedInfoValid - Has the callee saved info been calculated yet? 403 bool isCalleeSavedInfoValid() const { return CSIValid; } 404 405 void setCalleeSavedInfoValid(bool v) { CSIValid = v; } 406 407 /// getPristineRegs - Return a set of physical registers that are pristine on 408 /// entry to the MBB. 409 /// 410 /// Pristine registers hold a value that is useless to the current function, 411 /// but that must be preserved - they are callee saved registers that have not 412 /// been saved yet. 413 /// 414 /// Before the PrologueEpilogueInserter has placed the CSR spill code, this 415 /// method always returns an empty set. 416 BitVector getPristineRegs(const MachineBasicBlock *MBB) const; 417 418 /// getMachineModuleInfo - Used by a prologue/epilogue 419 /// emitter (TargetRegisterInfo) to provide frame layout information. 420 MachineModuleInfo *getMachineModuleInfo() const { return MMI; } 421 422 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to 423 /// indicate that frame layout information should be gathered. 424 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; } 425 426 /// print - Used by the MachineFunction printer to print information about 427 /// stack objects. Implemented in MachineFunction.cpp 428 /// 429 void print(const MachineFunction &MF, raw_ostream &OS) const; 430 431 /// dump - Print the function to stderr. 432 void dump(const MachineFunction &MF) const; 433}; 434 435} // End llvm namespace 436 437#endif 438