TargetLowering.h revision a8fbee6f09f06ae224d855e07093c5e70b3fb694
1//===-- llvm/Target/TargetLowering.h - Target Lowering Info -----*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file describes how to lower LLVM code to machine code. This has two 11// main components: 12// 13// 1. Which ValueTypes are natively supported by the target. 14// 2. Which operations are supported for supported ValueTypes. 15// 3. Cost thresholds for alternative implementations of certain operations. 16// 17// In addition it has a few other components, like information about FP 18// immediates. 19// 20//===----------------------------------------------------------------------===// 21 22#ifndef LLVM_TARGET_TARGETLOWERING_H 23#define LLVM_TARGET_TARGETLOWERING_H 24 25#include "llvm/Type.h" 26#include "llvm/CodeGen/ValueTypes.h" 27#include <vector> 28 29namespace llvm { 30 class Value; 31 class Function; 32 class TargetMachine; 33 class TargetData; 34 class TargetRegisterClass; 35 class SDNode; 36 class SDOperand; 37 class SelectionDAG; 38 39//===----------------------------------------------------------------------===// 40/// TargetLowering - This class defines information used to lower LLVM code to 41/// legal SelectionDAG operators that the target instruction selector can accept 42/// natively. 43/// 44/// This class also defines callbacks that targets must implement to lower 45/// target-specific constructs to SelectionDAG operators. 46/// 47class TargetLowering { 48public: 49 /// LegalizeAction - This enum indicates whether operations are valid for a 50 /// target, and if not, what action should be used to make them valid. 51 enum LegalizeAction { 52 Legal, // The target natively supports this operation. 53 Promote, // This operation should be executed in a larger type. 54 Expand, // Try to expand this to other ops, otherwise use a libcall. 55 Custom, // Use the LowerOperation hook to implement custom lowering. 56 }; 57 58 enum OutOfRangeShiftAmount { 59 Undefined, // Oversized shift amounts are undefined (default). 60 Mask, // Shift amounts are auto masked (anded) to value size. 61 Extend, // Oversized shift pulls in zeros or sign bits. 62 }; 63 64 enum SetCCResultValue { 65 UndefinedSetCCResult, // SetCC returns a garbage/unknown extend. 66 ZeroOrOneSetCCResult, // SetCC returns a zero extended result. 67 ZeroOrNegativeOneSetCCResult, // SetCC returns a sign extended result. 68 }; 69 70 TargetLowering(TargetMachine &TM); 71 virtual ~TargetLowering(); 72 73 TargetMachine &getTargetMachine() const { return TM; } 74 const TargetData &getTargetData() const { return TD; } 75 76 bool isLittleEndian() const { return IsLittleEndian; } 77 MVT::ValueType getPointerTy() const { return PointerTy; } 78 MVT::ValueType getShiftAmountTy() const { return ShiftAmountTy; } 79 OutOfRangeShiftAmount getShiftAmountFlavor() const {return ShiftAmtHandling; } 80 81 /// isSetCCExpensive - Return true if the setcc operation is expensive for 82 /// this target. 83 bool isSetCCExpensive() const { return SetCCIsExpensive; } 84 85 /// getSetCCResultTy - Return the ValueType of the result of setcc operations. 86 /// 87 MVT::ValueType getSetCCResultTy() const { return SetCCResultTy; } 88 89 /// getSetCCResultContents - For targets without boolean registers, this flag 90 /// returns information about the contents of the high-bits in the setcc 91 /// result register. 92 SetCCResultValue getSetCCResultContents() const { return SetCCResultContents;} 93 94 /// getRegClassFor - Return the register class that should be used for the 95 /// specified value type. This may only be called on legal types. 96 TargetRegisterClass *getRegClassFor(MVT::ValueType VT) const { 97 TargetRegisterClass *RC = RegClassForVT[VT]; 98 assert(RC && "This value type is not natively supported!"); 99 return RC; 100 } 101 102 /// isTypeLegal - Return true if the target has native support for the 103 /// specified value type. This means that it has a register that directly 104 /// holds it without promotions or expansions. 105 bool isTypeLegal(MVT::ValueType VT) const { 106 return RegClassForVT[VT] != 0; 107 } 108 109 /// getTypeAction - Return how we should legalize values of this type, either 110 /// it is already legal (return 'Legal') or we need to promote it to a larger 111 /// type (return 'Promote'), or we need to expand it into multiple registers 112 /// of smaller integer type (return 'Expand'). 'Custom' is not an option. 113 LegalizeAction getTypeAction(MVT::ValueType VT) const { 114 return (LegalizeAction)((ValueTypeActions >> (2*VT)) & 3); 115 } 116 unsigned getValueTypeActions() const { return ValueTypeActions; } 117 118 /// getTypeToTransformTo - For types supported by the target, this is an 119 /// identity function. For types that must be promoted to larger types, this 120 /// returns the larger type to promote to. For types that are larger than the 121 /// largest integer register, this contains one step in the expansion to get 122 /// to the smaller register. 123 MVT::ValueType getTypeToTransformTo(MVT::ValueType VT) const { 124 return TransformToType[VT]; 125 } 126 127 typedef std::vector<double>::const_iterator legal_fpimm_iterator; 128 legal_fpimm_iterator legal_fpimm_begin() const { 129 return LegalFPImmediates.begin(); 130 } 131 legal_fpimm_iterator legal_fpimm_end() const { 132 return LegalFPImmediates.end(); 133 } 134 135 /// getOperationAction - Return how this operation should be treated: either 136 /// it is legal, needs to be promoted to a larger size, needs to be 137 /// expanded to some other code sequence, or the target has a custom expander 138 /// for it. 139 LegalizeAction getOperationAction(unsigned Op, MVT::ValueType VT) const { 140 return (LegalizeAction)((OpActions[Op] >> (2*VT)) & 3); 141 } 142 143 /// isOperationLegal - Return true if the specified operation is legal on this 144 /// target. 145 bool isOperationLegal(unsigned Op, MVT::ValueType VT) const { 146 return getOperationAction(Op, VT) == Legal; 147 } 148 149 /// getTypeToPromoteTo - If the action for this operation is to promote, this 150 /// method returns the ValueType to promote to. 151 MVT::ValueType getTypeToPromoteTo(unsigned Op, MVT::ValueType VT) const { 152 assert(getOperationAction(Op, VT) == Promote && 153 "This operation isn't promoted!"); 154 MVT::ValueType NVT = VT; 155 do { 156 NVT = (MVT::ValueType)(NVT+1); 157 assert(MVT::isInteger(NVT) == MVT::isInteger(VT) && NVT != MVT::isVoid && 158 "Didn't find type to promote to!"); 159 } while (!isTypeLegal(NVT) || 160 getOperationAction(Op, NVT) == Promote); 161 return NVT; 162 } 163 164 /// getValueType - Return the MVT::ValueType corresponding to this LLVM type. 165 /// This is fixed by the LLVM operations except for the pointer size. 166 MVT::ValueType getValueType(const Type *Ty) const { 167 switch (Ty->getTypeID()) { 168 default: assert(0 && "Unknown type!"); 169 case Type::VoidTyID: return MVT::isVoid; 170 case Type::BoolTyID: return MVT::i1; 171 case Type::UByteTyID: 172 case Type::SByteTyID: return MVT::i8; 173 case Type::ShortTyID: 174 case Type::UShortTyID: return MVT::i16; 175 case Type::IntTyID: 176 case Type::UIntTyID: return MVT::i32; 177 case Type::LongTyID: 178 case Type::ULongTyID: return MVT::i64; 179 case Type::FloatTyID: return MVT::f32; 180 case Type::DoubleTyID: return MVT::f64; 181 case Type::PointerTyID: return PointerTy; 182 } 183 } 184 185 /// getNumElements - Return the number of registers that this ValueType will 186 /// eventually require. This is always one for all non-integer types, is 187 /// one for any types promoted to live in larger registers, but may be more 188 /// than one for types (like i64) that are split into pieces. 189 unsigned getNumElements(MVT::ValueType VT) const { 190 return NumElementsForVT[VT]; 191 } 192 193 /// This function returns the maximum number of store operations permitted 194 /// to replace a call to llvm.memset. The value is set by the target at the 195 /// performance threshold for such a replacement. 196 /// @brief Get maximum # of store operations permitted for llvm.memset 197 unsigned getMaxStoresPerMemSet() const { return maxStoresPerMemSet; } 198 199 /// This function returns the maximum number of store operations permitted 200 /// to replace a call to llvm.memcpy. The value is set by the target at the 201 /// performance threshold for such a replacement. 202 /// @brief Get maximum # of store operations permitted for llvm.memcpy 203 unsigned getMaxStoresPerMemCpy() const { return maxStoresPerMemCpy; } 204 205 /// This function returns the maximum number of store operations permitted 206 /// to replace a call to llvm.memmove. The value is set by the target at the 207 /// performance threshold for such a replacement. 208 /// @brief Get maximum # of store operations permitted for llvm.memmove 209 unsigned getMaxStoresPerMemMove() const { return maxStoresPerMemMove; } 210 211 /// This function returns true if the target allows unaligned stores. This is 212 /// used in situations where an array copy/move/set is converted to a sequence 213 /// of store operations. It ensures that such replacements don't generate 214 /// code that causes an alignment error (trap) on the target machine. 215 /// @brief Determine if the target supports unaligned stores. 216 bool allowsUnalignedStores() const { return allowUnalignedStores; } 217 218 //===--------------------------------------------------------------------===// 219 // TargetLowering Configuration Methods - These methods should be invoked by 220 // the derived class constructor to configure this object for the target. 221 // 222 223protected: 224 225 /// setShiftAmountType - Describe the type that should be used for shift 226 /// amounts. This type defaults to the pointer type. 227 void setShiftAmountType(MVT::ValueType VT) { ShiftAmountTy = VT; } 228 229 /// setSetCCResultType - Describe the type that shoudl be used as the result 230 /// of a setcc operation. This defaults to the pointer type. 231 void setSetCCResultType(MVT::ValueType VT) { SetCCResultTy = VT; } 232 233 /// setSetCCResultContents - Specify how the target extends the result of a 234 /// setcc operation in a register. 235 void setSetCCResultContents(SetCCResultValue Ty) { SetCCResultContents = Ty; } 236 237 /// setShiftAmountFlavor - Describe how the target handles out of range shift 238 /// amounts. 239 void setShiftAmountFlavor(OutOfRangeShiftAmount OORSA) { 240 ShiftAmtHandling = OORSA; 241 } 242 243 /// setSetCCIxExpensive - This is a short term hack for targets that codegen 244 /// setcc as a conditional branch. This encourages the code generator to fold 245 /// setcc operations into other operations if possible. 246 void setSetCCIsExpensive() { SetCCIsExpensive = true; } 247 248 /// addRegisterClass - Add the specified register class as an available 249 /// regclass for the specified value type. This indicates the selector can 250 /// handle values of that class natively. 251 void addRegisterClass(MVT::ValueType VT, TargetRegisterClass *RC) { 252 AvailableRegClasses.push_back(std::make_pair(VT, RC)); 253 RegClassForVT[VT] = RC; 254 } 255 256 /// computeRegisterProperties - Once all of the register classes are added, 257 /// this allows us to compute derived properties we expose. 258 void computeRegisterProperties(); 259 260 /// setOperationAction - Indicate that the specified operation does not work 261 /// with the specified type and indicate what to do about it. 262 void setOperationAction(unsigned Op, MVT::ValueType VT, 263 LegalizeAction Action) { 264 assert(VT < 16 && Op < sizeof(OpActions)/sizeof(OpActions[0]) && 265 "Table isn't big enough!"); 266 OpActions[Op] |= Action << VT*2; 267 } 268 269 /// addLegalFPImmediate - Indicate that this target can instruction select 270 /// the specified FP immediate natively. 271 void addLegalFPImmediate(double Imm) { 272 LegalFPImmediates.push_back(Imm); 273 } 274 275public: 276 277 //===--------------------------------------------------------------------===// 278 // Lowering methods - These methods must be implemented by targets so that 279 // the SelectionDAGLowering code knows how to lower these. 280 // 281 282 /// LowerArguments - This hook must be implemented to indicate how we should 283 /// lower the arguments for the specified function, into the specified DAG. 284 virtual std::vector<SDOperand> 285 LowerArguments(Function &F, SelectionDAG &DAG) = 0; 286 287 /// LowerCallTo - This hook lowers an abstract call to a function into an 288 /// actual call. This returns a pair of operands. The first element is the 289 /// return value for the function (if RetTy is not VoidTy). The second 290 /// element is the outgoing token chain. 291 typedef std::vector<std::pair<SDOperand, const Type*> > ArgListTy; 292 virtual std::pair<SDOperand, SDOperand> 293 LowerCallTo(SDOperand Chain, const Type *RetTy, bool isVarArg, 294 unsigned CallingConv, bool isTailCall, SDOperand Callee, 295 ArgListTy &Args, SelectionDAG &DAG) = 0; 296 297 /// LowerVAStart - This lowers the llvm.va_start intrinsic. If not 298 /// implemented, this method prints a message and aborts. This method should 299 /// return the modified chain value. Note that VAListPtr* correspond to the 300 /// llvm.va_start operand. 301 virtual SDOperand LowerVAStart(SDOperand Chain, SDOperand VAListP, 302 Value *VAListV, SelectionDAG &DAG); 303 304 /// LowerVAEnd - This lowers llvm.va_end and returns the resultant chain. If 305 /// not implemented, this defaults to a noop. 306 virtual SDOperand LowerVAEnd(SDOperand Chain, SDOperand LP, Value *LV, 307 SelectionDAG &DAG); 308 309 /// LowerVACopy - This lowers llvm.va_copy and returns the resultant chain. 310 /// If not implemented, this defaults to loading a pointer from the input and 311 /// storing it to the output. 312 virtual SDOperand LowerVACopy(SDOperand Chain, SDOperand SrcP, Value *SrcV, 313 SDOperand DestP, Value *DestV, 314 SelectionDAG &DAG); 315 316 /// LowerVAArg - This lowers the vaarg instruction. If not implemented, this 317 /// prints a message and aborts. 318 virtual std::pair<SDOperand,SDOperand> 319 LowerVAArg(SDOperand Chain, SDOperand VAListP, Value *VAListV, 320 const Type *ArgTy, SelectionDAG &DAG); 321 322 /// LowerFrameReturnAddress - This hook lowers a call to llvm.returnaddress or 323 /// llvm.frameaddress (depending on the value of the first argument). The 324 /// return values are the result pointer and the resultant token chain. If 325 /// not implemented, both of these intrinsics will return null. 326 virtual std::pair<SDOperand, SDOperand> 327 LowerFrameReturnAddress(bool isFrameAddr, SDOperand Chain, unsigned Depth, 328 SelectionDAG &DAG); 329 330 /// LowerOperation - For operations that are unsupported by the target, and 331 /// which are registered to use 'custom' lowering. This callback is invoked. 332 /// If the target has no operations that require custom lowering, it need not 333 /// implement this. The default implementation of this aborts. 334 virtual SDOperand LowerOperation(SDOperand Op, SelectionDAG &DAG); 335 336 //===--------------------------------------------------------------------===// 337 // Scheduler hooks 338 // 339 340 // InsertAtEndOfBasicBlock - This method should be implemented by targets that 341 // mark instructions with the 'usesCustomDAGSChedInserter' flag. These 342 // instructions are special in various ways, which require special support to 343 // insert. The specified MachineInstr is created but not inserted into any 344 // basic blocks, and the scheduler passes ownership of it to this method. 345 virtual MachineBasicBlock *InsertAtEndOfBasicBlock(MachineInstr *MI, 346 MachineBasicBlock *MBB); 347 348private: 349 TargetMachine &TM; 350 const TargetData &TD; 351 352 /// IsLittleEndian - True if this is a little endian target. 353 /// 354 bool IsLittleEndian; 355 356 /// PointerTy - The type to use for pointers, usually i32 or i64. 357 /// 358 MVT::ValueType PointerTy; 359 360 /// ShiftAmountTy - The type to use for shift amounts, usually i8 or whatever 361 /// PointerTy is. 362 MVT::ValueType ShiftAmountTy; 363 364 OutOfRangeShiftAmount ShiftAmtHandling; 365 366 /// SetCCIsExpensive - This is a short term hack for targets that codegen 367 /// setcc as a conditional branch. This encourages the code generator to fold 368 /// setcc operations into other operations if possible. 369 bool SetCCIsExpensive; 370 371 /// SetCCResultTy - The type that SetCC operations use. This defaults to the 372 /// PointerTy. 373 MVT::ValueType SetCCResultTy; 374 375 /// SetCCResultContents - Information about the contents of the high-bits in 376 /// the result of a setcc comparison operation. 377 SetCCResultValue SetCCResultContents; 378 379 /// RegClassForVT - This indicates the default register class to use for 380 /// each ValueType the target supports natively. 381 TargetRegisterClass *RegClassForVT[MVT::LAST_VALUETYPE]; 382 unsigned char NumElementsForVT[MVT::LAST_VALUETYPE]; 383 384 /// ValueTypeActions - This is a bitvector that contains two bits for each 385 /// value type, where the two bits correspond to the LegalizeAction enum. 386 /// This can be queried with "getTypeAction(VT)". 387 unsigned ValueTypeActions; 388 389 /// TransformToType - For any value types we are promoting or expanding, this 390 /// contains the value type that we are changing to. For Expanded types, this 391 /// contains one step of the expand (e.g. i64 -> i32), even if there are 392 /// multiple steps required (e.g. i64 -> i16). For types natively supported 393 /// by the system, this holds the same type (e.g. i32 -> i32). 394 MVT::ValueType TransformToType[MVT::LAST_VALUETYPE]; 395 396 /// OpActions - For each operation and each value type, keep a LegalizeAction 397 /// that indicates how instruction selection should deal with the operation. 398 /// Most operations are Legal (aka, supported natively by the target), but 399 /// operations that are not should be described. Note that operations on 400 /// non-legal value types are not described here. 401 unsigned OpActions[128]; 402 403 std::vector<double> LegalFPImmediates; 404 405 std::vector<std::pair<MVT::ValueType, 406 TargetRegisterClass*> > AvailableRegClasses; 407 408protected: 409 /// When lowering %llvm.memset this field specifies the maximum number of 410 /// store operations that may be substituted for the call to memset. Targets 411 /// must set this value based on the cost threshold for that target. Targets 412 /// should assume that the memset will be done using as many of the largest 413 /// store operations first, followed by smaller ones, if necessary, per 414 /// alignment restrictions. For example, storing 9 bytes on a 32-bit machine 415 /// with 16-bit alignment would result in four 2-byte stores and one 1-byte 416 /// store. This only applies to setting a constant array of a constant size. 417 /// @brief Specify maximum number of store instructions per memset call. 418 unsigned maxStoresPerMemSet; 419 420 /// When lowering %llvm.memcpy this field specifies the maximum number of 421 /// store operations that may be substituted for a call to memcpy. Targets 422 /// must set this value based on the cost threshold for that target. Targets 423 /// should assume that the memcpy will be done using as many of the largest 424 /// store operations first, followed by smaller ones, if necessary, per 425 /// alignment restrictions. For example, storing 7 bytes on a 32-bit machine 426 /// with 32-bit alignment would result in one 4-byte store, a one 2-byte store 427 /// and one 1-byte store. This only applies to copying a constant array of 428 /// constant size. 429 /// @brief Specify maximum bytes of store instructions per memcpy call. 430 unsigned maxStoresPerMemCpy; 431 432 /// When lowering %llvm.memmove this field specifies the maximum number of 433 /// store instructions that may be substituted for a call to memmove. Targets 434 /// must set this value based on the cost threshold for that target. Targets 435 /// should assume that the memmove will be done using as many of the largest 436 /// store operations first, followed by smaller ones, if necessary, per 437 /// alignment restrictions. For example, moving 9 bytes on a 32-bit machine 438 /// with 8-bit alignment would result in nine 1-byte stores. This only 439 /// applies to copying a constant array of constant size. 440 /// @brief Specify maximum bytes of store instructions per memmove call. 441 unsigned maxStoresPerMemMove; 442 443 /// This field specifies whether the target machine permits unaligned stores. 444 /// This is used to determine the size of store operations for copying 445 /// small arrays and other similar tasks. 446 /// @brief Indicate whether the target machine permits unaligned stores. 447 bool allowUnalignedStores; 448}; 449} // end llvm namespace 450 451#endif 452