MachineFrameInfo.h revision 193323
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/Support/DataTypes.h" 18#include <cassert> 19#include <iosfwd> 20#include <vector> 21 22namespace llvm { 23class TargetData; 24class TargetRegisterClass; 25class Type; 26class MachineModuleInfo; 27class MachineFunction; 28class TargetFrameInfo; 29 30/// The CalleeSavedInfo class tracks the information need to locate where a 31/// callee saved register in the current frame. 32class CalleeSavedInfo { 33 34private: 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) 42 , RegClass(RC) 43 , FrameIdx(FI) 44 {} 45 46 // Accessors. 47 unsigned getReg() const { return Reg; } 48 const TargetRegisterClass *getRegClass() const { return RegClass; } 49 int getFrameIdx() const { return FrameIdx; } 50 void setFrameIdx(int FI) { FrameIdx = FI; } 51}; 52 53/// The MachineFrameInfo class represents an abstract stack frame until 54/// prolog/epilog code is inserted. This class is key to allowing stack frame 55/// representation optimizations, such as frame pointer elimination. It also 56/// allows more mundane (but still important) optimizations, such as reordering 57/// of abstract objects on the stack frame. 58/// 59/// To support this, the class assigns unique integer identifiers to stack 60/// objects requested clients. These identifiers are negative integers for 61/// fixed stack objects (such as arguments passed on the stack) or nonnegative 62/// for objects that may be reordered. Instructions which refer to stack 63/// objects use a special MO_FrameIndex operand to represent these frame 64/// indexes. 65/// 66/// Because this class keeps track of all references to the stack frame, it 67/// knows when a variable sized object is allocated on the stack. This is the 68/// sole condition which prevents frame pointer elimination, which is an 69/// important optimization on register-poor architectures. Because original 70/// variable sized alloca's in the source program are the only source of 71/// variable sized stack objects, it is safe to decide whether there will be 72/// any variable sized objects before all stack objects are known (for 73/// example, register allocator spill code never needs variable sized 74/// objects). 75/// 76/// When prolog/epilog code emission is performed, the final stack frame is 77/// built and the machine instructions are modified to refer to the actual 78/// stack offsets of the object, eliminating all MO_FrameIndex operands from 79/// the program. 80/// 81/// @brief Abstract Stack Frame Information 82class MachineFrameInfo { 83 84 // StackObject - Represent a single object allocated on the stack. 85 struct StackObject { 86 // The size of this object on the stack. 0 means a variable sized object, 87 // ~0ULL means a dead object. 88 uint64_t Size; 89 90 // Alignment - The required alignment of this stack slot. 91 unsigned Alignment; 92 93 // isImmutable - If true, the value of the stack object is set before 94 // entering the function and is not modified inside the function. By 95 // default, fixed objects are immutable unless marked otherwise. 96 bool isImmutable; 97 98 // SPOffset - The offset of this object from the stack pointer on entry to 99 // the function. This field has no meaning for a variable sized element. 100 int64_t SPOffset; 101 102 StackObject(uint64_t Sz, unsigned Al, int64_t SP = 0, bool IM = false) 103 : Size(Sz), Alignment(Al), isImmutable(IM), SPOffset(SP) {} 104 }; 105 106 /// Objects - The list of stack objects allocated... 107 /// 108 std::vector<StackObject> Objects; 109 110 /// NumFixedObjects - This contains the number of fixed objects contained on 111 /// the stack. Because fixed objects are stored at a negative index in the 112 /// Objects list, this is also the index to the 0th object in the list. 113 /// 114 unsigned NumFixedObjects; 115 116 /// HasVarSizedObjects - This boolean keeps track of whether any variable 117 /// sized objects have been allocated yet. 118 /// 119 bool HasVarSizedObjects; 120 121 /// FrameAddressTaken - This boolean keeps track of whether there is a call 122 /// to builtin \@llvm.frameaddress. 123 bool FrameAddressTaken; 124 125 /// StackSize - The prolog/epilog code inserter calculates the final stack 126 /// offsets for all of the fixed size objects, updating the Objects list 127 /// above. It then updates StackSize to contain the number of bytes that need 128 /// to be allocated on entry to the function. 129 /// 130 uint64_t StackSize; 131 132 /// OffsetAdjustment - The amount that a frame offset needs to be adjusted to 133 /// have the actual offset from the stack/frame pointer. The calculation is 134 /// MFI->getObjectOffset(Index) + StackSize - TFI.getOffsetOfLocalArea() + 135 /// OffsetAdjustment. If OffsetAdjustment is zero (default) then offsets are 136 /// away from TOS. If OffsetAdjustment == StackSize then offsets are toward 137 /// TOS. 138 int OffsetAdjustment; 139 140 /// MaxAlignment - The prolog/epilog code inserter may process objects 141 /// that require greater alignment than the default alignment the target 142 /// provides. To handle this, MaxAlignment is set to the maximum alignment 143 /// needed by the objects on the current frame. If this is greater than the 144 /// native alignment maintained by the compiler, dynamic alignment code will 145 /// be needed. 146 /// 147 unsigned MaxAlignment; 148 149 /// HasCalls - Set to true if this function has any function calls. This is 150 /// only valid during and after prolog/epilog code insertion. 151 bool HasCalls; 152 153 /// StackProtectorIdx - The frame index for the stack protector. 154 int StackProtectorIdx; 155 156 /// MaxCallFrameSize - This contains the size of the largest call frame if the 157 /// target uses frame setup/destroy pseudo instructions (as defined in the 158 /// TargetFrameInfo class). This information is important for frame pointer 159 /// elimination. If is only valid during and after prolog/epilog code 160 /// insertion. 161 /// 162 unsigned MaxCallFrameSize; 163 164 /// CSInfo - The prolog/epilog code inserter fills in this vector with each 165 /// callee saved register saved in the frame. Beyond its use by the prolog/ 166 /// epilog code inserter, this data used for debug info and exception 167 /// handling. 168 std::vector<CalleeSavedInfo> CSInfo; 169 170 /// MMI - This field is set (via setMachineModuleInfo) by a module info 171 /// consumer (ex. DwarfWriter) to indicate that frame layout information 172 /// should be acquired. Typically, it's the responsibility of the target's 173 /// TargetRegisterInfo prologue/epilogue emitting code to inform 174 /// MachineModuleInfo of frame layouts. 175 MachineModuleInfo *MMI; 176 177 /// TargetFrameInfo - Target information about frame layout. 178 /// 179 const TargetFrameInfo &TFI; 180public: 181 explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) { 182 StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0; 183 HasVarSizedObjects = false; 184 FrameAddressTaken = false; 185 HasCalls = false; 186 StackProtectorIdx = -1; 187 MaxCallFrameSize = 0; 188 MMI = 0; 189 } 190 191 /// hasStackObjects - Return true if there are any stack objects in this 192 /// function. 193 /// 194 bool hasStackObjects() const { return !Objects.empty(); } 195 196 /// hasVarSizedObjects - This method may be called any time after instruction 197 /// selection is complete to determine if the stack frame for this function 198 /// contains any variable sized objects. 199 /// 200 bool hasVarSizedObjects() const { return HasVarSizedObjects; } 201 202 /// getStackProtectorIndex/setStackProtectorIndex - Return the index for the 203 /// stack protector object. 204 /// 205 int getStackProtectorIndex() const { return StackProtectorIdx; } 206 void setStackProtectorIndex(int I) { StackProtectorIdx = I; } 207 208 /// isFrameAddressTaken - This method may be called any time after instruction 209 /// selection is complete to determine if there is a call to 210 /// \@llvm.frameaddress in this function. 211 bool isFrameAddressTaken() const { return FrameAddressTaken; } 212 void setFrameAddressIsTaken(bool T) { FrameAddressTaken = T; } 213 214 /// getObjectIndexBegin - Return the minimum frame object index. 215 /// 216 int getObjectIndexBegin() const { return -NumFixedObjects; } 217 218 /// getObjectIndexEnd - Return one past the maximum frame object index. 219 /// 220 int getObjectIndexEnd() const { return (int)Objects.size()-NumFixedObjects; } 221 222 /// getNumFixedObjects() - Return the number of fixed objects. 223 unsigned getNumFixedObjects() const { return NumFixedObjects; } 224 225 /// getNumObjects() - Return the number of objects. 226 /// 227 unsigned getNumObjects() const { return Objects.size(); } 228 229 /// getObjectSize - Return the size of the specified object. 230 /// 231 int64_t getObjectSize(int ObjectIdx) const { 232 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 233 "Invalid Object Idx!"); 234 return Objects[ObjectIdx+NumFixedObjects].Size; 235 } 236 237 /// setObjectSize - Change the size of the specified stack object. 238 void setObjectSize(int ObjectIdx, int64_t Size) { 239 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 240 "Invalid Object Idx!"); 241 Objects[ObjectIdx+NumFixedObjects].Size = Size; 242 } 243 244 /// getObjectAlignment - Return the alignment of the specified stack object. 245 unsigned getObjectAlignment(int ObjectIdx) const { 246 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 247 "Invalid Object Idx!"); 248 return Objects[ObjectIdx+NumFixedObjects].Alignment; 249 } 250 251 /// setObjectAlignment - Change the alignment of the specified stack object. 252 void setObjectAlignment(int ObjectIdx, unsigned Align) { 253 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 254 "Invalid Object Idx!"); 255 Objects[ObjectIdx+NumFixedObjects].Alignment = Align; 256 } 257 258 /// getObjectOffset - Return the assigned stack offset of the specified object 259 /// from the incoming stack pointer. 260 /// 261 int64_t getObjectOffset(int ObjectIdx) const { 262 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 263 "Invalid Object Idx!"); 264 assert(!isDeadObjectIndex(ObjectIdx) && 265 "Getting frame offset for a dead object?"); 266 return Objects[ObjectIdx+NumFixedObjects].SPOffset; 267 } 268 269 /// setObjectOffset - Set the stack frame offset of the specified object. The 270 /// offset is relative to the stack pointer on entry to the function. 271 /// 272 void setObjectOffset(int ObjectIdx, int64_t SPOffset) { 273 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 274 "Invalid Object Idx!"); 275 assert(!isDeadObjectIndex(ObjectIdx) && 276 "Setting frame offset for a dead object?"); 277 Objects[ObjectIdx+NumFixedObjects].SPOffset = SPOffset; 278 } 279 280 /// getStackSize - Return the number of bytes that must be allocated to hold 281 /// all of the fixed size frame objects. This is only valid after 282 /// Prolog/Epilog code insertion has finalized the stack frame layout. 283 /// 284 uint64_t getStackSize() const { return StackSize; } 285 286 /// setStackSize - Set the size of the stack... 287 /// 288 void setStackSize(uint64_t Size) { StackSize = Size; } 289 290 /// getOffsetAdjustment - Return the correction for frame offsets. 291 /// 292 int getOffsetAdjustment() const { return OffsetAdjustment; } 293 294 /// setOffsetAdjustment - Set the correction for frame offsets. 295 /// 296 void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; } 297 298 /// getMaxAlignment - Return the alignment in bytes that this function must be 299 /// aligned to, which is greater than the default stack alignment provided by 300 /// the target. 301 /// 302 unsigned getMaxAlignment() const { return MaxAlignment; } 303 304 /// setMaxAlignment - Set the preferred alignment. 305 /// 306 void setMaxAlignment(unsigned Align) { MaxAlignment = Align; } 307 308 /// hasCalls - Return true if the current function has no function calls. 309 /// This is only valid during or after prolog/epilog code emission. 310 /// 311 bool hasCalls() const { return HasCalls; } 312 void setHasCalls(bool V) { HasCalls = V; } 313 314 /// getMaxCallFrameSize - Return the maximum size of a call frame that must be 315 /// allocated for an outgoing function call. This is only available if 316 /// CallFrameSetup/Destroy pseudo instructions are used by the target, and 317 /// then only during or after prolog/epilog code insertion. 318 /// 319 unsigned getMaxCallFrameSize() const { return MaxCallFrameSize; } 320 void setMaxCallFrameSize(unsigned S) { MaxCallFrameSize = S; } 321 322 /// CreateFixedObject - Create a new object at a fixed location on the stack. 323 /// All fixed objects should be created before other objects are created for 324 /// efficiency. By default, fixed objects are immutable. This returns an 325 /// index with a negative value. 326 /// 327 int CreateFixedObject(uint64_t Size, int64_t SPOffset, 328 bool Immutable = true); 329 330 331 /// isFixedObjectIndex - Returns true if the specified index corresponds to a 332 /// fixed stack object. 333 bool isFixedObjectIndex(int ObjectIdx) const { 334 return ObjectIdx < 0 && (ObjectIdx >= -(int)NumFixedObjects); 335 } 336 337 /// isImmutableObjectIndex - Returns true if the specified index corresponds 338 /// to an immutable object. 339 bool isImmutableObjectIndex(int ObjectIdx) const { 340 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 341 "Invalid Object Idx!"); 342 return Objects[ObjectIdx+NumFixedObjects].isImmutable; 343 } 344 345 /// isDeadObjectIndex - Returns true if the specified index corresponds to 346 /// a dead object. 347 bool isDeadObjectIndex(int ObjectIdx) const { 348 assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() && 349 "Invalid Object Idx!"); 350 return Objects[ObjectIdx+NumFixedObjects].Size == ~0ULL; 351 } 352 353 /// CreateStackObject - Create a new statically sized stack object, returning 354 /// a nonnegative identifier to represent it. 355 /// 356 int CreateStackObject(uint64_t Size, unsigned Alignment) { 357 assert(Size != 0 && "Cannot allocate zero size stack objects!"); 358 Objects.push_back(StackObject(Size, Alignment)); 359 return (int)Objects.size()-NumFixedObjects-1; 360 } 361 362 /// RemoveStackObject - Remove or mark dead a statically sized stack object. 363 /// 364 void RemoveStackObject(int ObjectIdx) { 365 // Mark it dead. 366 Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL; 367 } 368 369 /// CreateVariableSizedObject - Notify the MachineFrameInfo object that a 370 /// variable sized object has been created. This must be created whenever a 371 /// variable sized object is created, whether or not the index returned is 372 /// actually used. 373 /// 374 int CreateVariableSizedObject() { 375 HasVarSizedObjects = true; 376 Objects.push_back(StackObject(0, 1)); 377 return (int)Objects.size()-NumFixedObjects-1; 378 } 379 380 /// getCalleeSavedInfo - Returns a reference to call saved info vector for the 381 /// current function. 382 const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const { 383 return CSInfo; 384 } 385 386 /// setCalleeSavedInfo - Used by prolog/epilog inserter to set the function's 387 /// callee saved information. 388 void setCalleeSavedInfo(const std::vector<CalleeSavedInfo> &CSI) { 389 CSInfo = CSI; 390 } 391 392 /// getMachineModuleInfo - Used by a prologue/epilogue 393 /// emitter (TargetRegisterInfo) to provide frame layout information. 394 MachineModuleInfo *getMachineModuleInfo() const { return MMI; } 395 396 /// setMachineModuleInfo - Used by a meta info consumer (DwarfWriter) to 397 /// indicate that frame layout information should be gathered. 398 void setMachineModuleInfo(MachineModuleInfo *mmi) { MMI = mmi; } 399 400 /// print - Used by the MachineFunction printer to print information about 401 /// stack objects. Implemented in MachineFunction.cpp 402 /// 403 void print(const MachineFunction &MF, std::ostream &OS) const; 404 405 /// dump - Call print(MF, std::cerr) to be called from the debugger. 406 void dump(const MachineFunction &MF) const; 407}; 408 409} // End llvm namespace 410 411#endif 412