ConstantFold.cpp revision 579dca12c2cfd60bc18aaadbd5331897d48fec29
1//===- ConstantFolding.cpp - LLVM constant folder -------------------------===// 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 implements folding of constants for LLVM. This implements the 11// (internal) ConstantFolding.h interface, which is used by the 12// ConstantExpr::get* methods to automatically fold constants when possible. 13// 14// The current constant folding implementation is implemented in two pieces: the 15// template-based folder for simple primitive constants like ConstantInt, and 16// the special case hackery that we use to symbolically evaluate expressions 17// that use ConstantExprs. 18// 19//===----------------------------------------------------------------------===// 20 21#include "ConstantFolding.h" 22#include "llvm/Constants.h" 23#include "llvm/Instructions.h" 24#include "llvm/DerivedTypes.h" 25#include "llvm/Function.h" 26#include "llvm/Support/Compiler.h" 27#include "llvm/Support/GetElementPtrTypeIterator.h" 28#include "llvm/Support/ManagedStatic.h" 29#include "llvm/Support/MathExtras.h" 30#include <limits> 31using namespace llvm; 32 33//===----------------------------------------------------------------------===// 34// ConstantFold*Instruction Implementations 35//===----------------------------------------------------------------------===// 36 37/// CastConstantPacked - Convert the specified ConstantPacked node to the 38/// specified packed type. At this point, we know that the elements of the 39/// input packed constant are all simple integer or FP values. 40static Constant *CastConstantPacked(ConstantPacked *CP, 41 const PackedType *DstTy) { 42 unsigned SrcNumElts = CP->getType()->getNumElements(); 43 unsigned DstNumElts = DstTy->getNumElements(); 44 const Type *SrcEltTy = CP->getType()->getElementType(); 45 const Type *DstEltTy = DstTy->getElementType(); 46 47 // If both vectors have the same number of elements (thus, the elements 48 // are the same size), perform the conversion now. 49 if (SrcNumElts == DstNumElts) { 50 std::vector<Constant*> Result; 51 52 // If the src and dest elements are both integers, or both floats, we can 53 // just BitCast each element because the elements are the same size. 54 if ((SrcEltTy->isIntegral() && DstEltTy->isIntegral()) || 55 (SrcEltTy->isFloatingPoint() && DstEltTy->isFloatingPoint())) { 56 for (unsigned i = 0; i != SrcNumElts; ++i) 57 Result.push_back( 58 ConstantExpr::getBitCast(CP->getOperand(i), DstEltTy)); 59 return ConstantPacked::get(Result); 60 } 61 62 // If this is an int-to-fp cast .. 63 if (SrcEltTy->isIntegral()) { 64 // Ensure that it is int-to-fp cast 65 assert(DstEltTy->isFloatingPoint()); 66 if (DstEltTy->getTypeID() == Type::DoubleTyID) { 67 for (unsigned i = 0; i != SrcNumElts; ++i) { 68 double V = 69 BitsToDouble(cast<ConstantInt>(CP->getOperand(i))->getZExtValue()); 70 Result.push_back(ConstantFP::get(Type::DoubleTy, V)); 71 } 72 return ConstantPacked::get(Result); 73 } 74 assert(DstEltTy == Type::FloatTy && "Unknown fp type!"); 75 for (unsigned i = 0; i != SrcNumElts; ++i) { 76 float V = 77 BitsToFloat(cast<ConstantInt>(CP->getOperand(i))->getZExtValue()); 78 Result.push_back(ConstantFP::get(Type::FloatTy, V)); 79 } 80 return ConstantPacked::get(Result); 81 } 82 83 // Otherwise, this is an fp-to-int cast. 84 assert(SrcEltTy->isFloatingPoint() && DstEltTy->isIntegral()); 85 86 if (SrcEltTy->getTypeID() == Type::DoubleTyID) { 87 for (unsigned i = 0; i != SrcNumElts; ++i) { 88 uint64_t V = 89 DoubleToBits(cast<ConstantFP>(CP->getOperand(i))->getValue()); 90 Constant *C = ConstantInt::get(Type::Int64Ty, V); 91 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy )); 92 } 93 return ConstantPacked::get(Result); 94 } 95 96 assert(SrcEltTy->getTypeID() == Type::FloatTyID); 97 for (unsigned i = 0; i != SrcNumElts; ++i) { 98 uint32_t V = FloatToBits(cast<ConstantFP>(CP->getOperand(i))->getValue()); 99 Constant *C = ConstantInt::get(Type::Int32Ty, V); 100 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy)); 101 } 102 return ConstantPacked::get(Result); 103 } 104 105 // Otherwise, this is a cast that changes element count and size. Handle 106 // casts which shrink the elements here. 107 108 // FIXME: We need to know endianness to do this! 109 110 return 0; 111} 112 113/// This function determines which opcode to use to fold two constant cast 114/// expressions together. It uses CastInst::isEliminableCastPair to determine 115/// the opcode. Consequently its just a wrapper around that function. 116/// @Determine if it is valid to fold a cast of a cast 117static unsigned 118foldConstantCastPair( 119 unsigned opc, ///< opcode of the second cast constant expression 120 const ConstantExpr*Op, ///< the first cast constant expression 121 const Type *DstTy ///< desintation type of the first cast 122) { 123 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); 124 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); 125 assert(CastInst::isCast(opc) && "Invalid cast opcode"); 126 127 // The the types and opcodes for the two Cast constant expressions 128 const Type *SrcTy = Op->getOperand(0)->getType(); 129 const Type *MidTy = Op->getType(); 130 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); 131 Instruction::CastOps secondOp = Instruction::CastOps(opc); 132 133 // Let CastInst::isEliminableCastPair do the heavy lifting. 134 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, 135 Type::Int64Ty); 136} 137 138Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V, 139 const Type *DestTy) { 140 const Type *SrcTy = V->getType(); 141 142 if (isa<UndefValue>(V)) 143 return UndefValue::get(DestTy); 144 145 // If the cast operand is a constant expression, there's a few things we can 146 // do to try to simplify it. 147 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 148 if (CE->isCast()) { 149 // Try hard to fold cast of cast because they are often eliminable. 150 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 151 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 152 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 153 // If all of the indexes in the GEP are null values, there is no pointer 154 // adjustment going on. We might as well cast the source pointer. 155 bool isAllNull = true; 156 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 157 if (!CE->getOperand(i)->isNullValue()) { 158 isAllNull = false; 159 break; 160 } 161 if (isAllNull) 162 // This is casting one pointer type to another, always BitCast 163 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 164 } 165 } 166 167 // We actually have to do a cast now. Perform the cast according to the 168 // opcode specified. 169 switch (opc) { 170 case Instruction::FPTrunc: 171 case Instruction::FPExt: 172 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) 173 return ConstantFP::get(DestTy, FPC->getValue()); 174 return 0; // Can't fold. 175 case Instruction::FPToUI: 176 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) 177 return ConstantInt::get(DestTy,(uint64_t) FPC->getValue()); 178 return 0; // Can't fold. 179 case Instruction::FPToSI: 180 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) 181 return ConstantInt::get(DestTy,(int64_t) FPC->getValue()); 182 return 0; // Can't fold. 183 case Instruction::IntToPtr: //always treated as unsigned 184 if (V->isNullValue()) // Is it an integral null value? 185 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 186 return 0; // Other pointer types cannot be casted 187 case Instruction::PtrToInt: // always treated as unsigned 188 if (V->isNullValue()) // is it a null pointer value? 189 return ConstantInt::get(DestTy, 0); 190 return 0; // Other pointer types cannot be casted 191 case Instruction::UIToFP: 192 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) 193 return ConstantFP::get(DestTy, double(CI->getZExtValue())); 194 return 0; 195 case Instruction::SIToFP: 196 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) 197 return ConstantFP::get(DestTy, double(CI->getSExtValue())); 198 return 0; 199 case Instruction::ZExt: 200 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) 201 return ConstantInt::get(DestTy, CI->getZExtValue()); 202 return 0; 203 case Instruction::SExt: 204 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) 205 return ConstantInt::get(DestTy, CI->getSExtValue()); 206 return 0; 207 case Instruction::Trunc: 208 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) // Can't trunc a bool 209 return ConstantInt::get(DestTy, CI->getZExtValue()); 210 return 0; 211 case Instruction::BitCast: 212 if (SrcTy == DestTy) 213 return (Constant*)V; // no-op cast 214 215 // Check to see if we are casting a pointer to an aggregate to a pointer to 216 // the first element. If so, return the appropriate GEP instruction. 217 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) 218 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) { 219 std::vector<Value*> IdxList; 220 IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); 221 const Type *ElTy = PTy->getElementType(); 222 while (ElTy != DPTy->getElementType()) { 223 if (const StructType *STy = dyn_cast<StructType>(ElTy)) { 224 if (STy->getNumElements() == 0) break; 225 ElTy = STy->getElementType(0); 226 IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); 227 } else if (const SequentialType *STy = 228 dyn_cast<SequentialType>(ElTy)) { 229 if (isa<PointerType>(ElTy)) break; // Can't index into pointers! 230 ElTy = STy->getElementType(); 231 IdxList.push_back(IdxList[0]); 232 } else { 233 break; 234 } 235 } 236 237 if (ElTy == DPTy->getElementType()) 238 return ConstantExpr::getGetElementPtr( 239 const_cast<Constant*>(V),IdxList); 240 } 241 242 // Handle casts from one packed constant to another. We know that the src 243 // and dest type have the same size (otherwise its an illegal cast). 244 if (const PackedType *DestPTy = dyn_cast<PackedType>(DestTy)) { 245 if (const PackedType *SrcTy = dyn_cast<PackedType>(V->getType())) { 246 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && 247 "Not cast between same sized vectors!"); 248 // First, check for null and undef 249 if (isa<ConstantAggregateZero>(V)) 250 return Constant::getNullValue(DestTy); 251 if (isa<UndefValue>(V)) 252 return UndefValue::get(DestTy); 253 254 if (const ConstantPacked *CP = dyn_cast<ConstantPacked>(V)) { 255 // This is a cast from a ConstantPacked of one type to a 256 // ConstantPacked of another type. Check to see if all elements of 257 // the input are simple. 258 bool AllSimpleConstants = true; 259 for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i) { 260 if (!isa<ConstantInt>(CP->getOperand(i)) && 261 !isa<ConstantFP>(CP->getOperand(i))) { 262 AllSimpleConstants = false; 263 break; 264 } 265 } 266 267 // If all of the elements are simple constants, we can fold this. 268 if (AllSimpleConstants) 269 return CastConstantPacked(const_cast<ConstantPacked*>(CP), DestPTy); 270 } 271 } 272 } 273 274 // Finally, implement bitcast folding now. The code below doesn't handle 275 // bitcast right. 276 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 277 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 278 279 // Handle integral constant input. 280 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 281 // Integral -> Integral, must be changing sign. 282 if (DestTy->isIntegral()) 283 return ConstantInt::get(DestTy, CI->getZExtValue()); 284 285 if (DestTy->isFloatingPoint()) { 286 if (DestTy == Type::FloatTy) 287 return ConstantFP::get(DestTy, BitsToFloat(CI->getZExtValue())); 288 assert(DestTy == Type::DoubleTy && "Unknown FP type!"); 289 return ConstantFP::get(DestTy, BitsToDouble(CI->getZExtValue())); 290 } 291 // Otherwise, can't fold this (packed?) 292 return 0; 293 } 294 295 // Handle ConstantFP input. 296 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) { 297 // FP -> Integral. 298 if (DestTy->isIntegral()) { 299 if (DestTy == Type::Int32Ty) 300 return ConstantInt::get(DestTy, FloatToBits(FP->getValue())); 301 assert(DestTy == Type::Int64Ty && 302 "Incorrect integer type for bitcast!"); 303 return ConstantInt::get(DestTy, DoubleToBits(FP->getValue())); 304 } 305 } 306 return 0; 307 default: 308 assert(!"Invalid CE CastInst opcode"); 309 break; 310 } 311 312 assert(0 && "Failed to cast constant expression"); 313 return 0; 314} 315 316Constant *llvm::ConstantFoldSelectInstruction(const Constant *Cond, 317 const Constant *V1, 318 const Constant *V2) { 319 if (const ConstantInt *CB = dyn_cast<ConstantInt>(Cond)) 320 return const_cast<Constant*>(CB->getZExtValue() ? V1 : V2); 321 322 if (isa<UndefValue>(V1)) return const_cast<Constant*>(V2); 323 if (isa<UndefValue>(V2)) return const_cast<Constant*>(V1); 324 if (isa<UndefValue>(Cond)) return const_cast<Constant*>(V1); 325 if (V1 == V2) return const_cast<Constant*>(V1); 326 return 0; 327} 328 329Constant *llvm::ConstantFoldExtractElementInstruction(const Constant *Val, 330 const Constant *Idx) { 331 if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 332 return UndefValue::get(cast<PackedType>(Val->getType())->getElementType()); 333 if (Val->isNullValue()) // ee(zero, x) -> zero 334 return Constant::getNullValue( 335 cast<PackedType>(Val->getType())->getElementType()); 336 337 if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) { 338 if (const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 339 return const_cast<Constant*>(CVal->getOperand(CIdx->getZExtValue())); 340 } else if (isa<UndefValue>(Idx)) { 341 // ee({w,x,y,z}, undef) -> w (an arbitrary value). 342 return const_cast<Constant*>(CVal->getOperand(0)); 343 } 344 } 345 return 0; 346} 347 348Constant *llvm::ConstantFoldInsertElementInstruction(const Constant *Val, 349 const Constant *Elt, 350 const Constant *Idx) { 351 const ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 352 if (!CIdx) return 0; 353 uint64_t idxVal = CIdx->getZExtValue(); 354 if (isa<UndefValue>(Val)) { 355 // Insertion of scalar constant into packed undef 356 // Optimize away insertion of undef 357 if (isa<UndefValue>(Elt)) 358 return const_cast<Constant*>(Val); 359 // Otherwise break the aggregate undef into multiple undefs and do 360 // the insertion 361 unsigned numOps = 362 cast<PackedType>(Val->getType())->getNumElements(); 363 std::vector<Constant*> Ops; 364 Ops.reserve(numOps); 365 for (unsigned i = 0; i < numOps; ++i) { 366 const Constant *Op = 367 (i == idxVal) ? Elt : UndefValue::get(Elt->getType()); 368 Ops.push_back(const_cast<Constant*>(Op)); 369 } 370 return ConstantPacked::get(Ops); 371 } 372 if (isa<ConstantAggregateZero>(Val)) { 373 // Insertion of scalar constant into packed aggregate zero 374 // Optimize away insertion of zero 375 if (Elt->isNullValue()) 376 return const_cast<Constant*>(Val); 377 // Otherwise break the aggregate zero into multiple zeros and do 378 // the insertion 379 unsigned numOps = 380 cast<PackedType>(Val->getType())->getNumElements(); 381 std::vector<Constant*> Ops; 382 Ops.reserve(numOps); 383 for (unsigned i = 0; i < numOps; ++i) { 384 const Constant *Op = 385 (i == idxVal) ? Elt : Constant::getNullValue(Elt->getType()); 386 Ops.push_back(const_cast<Constant*>(Op)); 387 } 388 return ConstantPacked::get(Ops); 389 } 390 if (const ConstantPacked *CVal = dyn_cast<ConstantPacked>(Val)) { 391 // Insertion of scalar constant into packed constant 392 std::vector<Constant*> Ops; 393 Ops.reserve(CVal->getNumOperands()); 394 for (unsigned i = 0; i < CVal->getNumOperands(); ++i) { 395 const Constant *Op = 396 (i == idxVal) ? Elt : cast<Constant>(CVal->getOperand(i)); 397 Ops.push_back(const_cast<Constant*>(Op)); 398 } 399 return ConstantPacked::get(Ops); 400 } 401 return 0; 402} 403 404Constant *llvm::ConstantFoldShuffleVectorInstruction(const Constant *V1, 405 const Constant *V2, 406 const Constant *Mask) { 407 // TODO: 408 return 0; 409} 410 411/// EvalVectorOp - Given two packed constants and a function pointer, apply the 412/// function pointer to each element pair, producing a new ConstantPacked 413/// constant. 414static Constant *EvalVectorOp(const ConstantPacked *V1, 415 const ConstantPacked *V2, 416 Constant *(*FP)(Constant*, Constant*)) { 417 std::vector<Constant*> Res; 418 for (unsigned i = 0, e = V1->getNumOperands(); i != e; ++i) 419 Res.push_back(FP(const_cast<Constant*>(V1->getOperand(i)), 420 const_cast<Constant*>(V2->getOperand(i)))); 421 return ConstantPacked::get(Res); 422} 423 424Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 425 const Constant *C1, 426 const Constant *C2) { 427 // Handle UndefValue up front 428 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 429 switch (Opcode) { 430 case Instruction::Add: 431 case Instruction::Sub: 432 case Instruction::Xor: 433 return UndefValue::get(C1->getType()); 434 case Instruction::Mul: 435 case Instruction::And: 436 return Constant::getNullValue(C1->getType()); 437 case Instruction::UDiv: 438 case Instruction::SDiv: 439 case Instruction::FDiv: 440 case Instruction::URem: 441 case Instruction::SRem: 442 case Instruction::FRem: 443 if (!isa<UndefValue>(C2)) // undef / X -> 0 444 return Constant::getNullValue(C1->getType()); 445 return const_cast<Constant*>(C2); // X / undef -> undef 446 case Instruction::Or: // X | undef -> -1 447 if (const PackedType *PTy = dyn_cast<PackedType>(C1->getType())) 448 return ConstantPacked::getAllOnesValue(PTy); 449 return ConstantInt::getAllOnesValue(C1->getType()); 450 case Instruction::LShr: 451 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 452 return const_cast<Constant*>(C1); // undef lshr undef -> undef 453 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 454 // undef lshr X -> 0 455 case Instruction::AShr: 456 if (!isa<UndefValue>(C2)) 457 return const_cast<Constant*>(C1); // undef ashr X --> undef 458 else if (isa<UndefValue>(C1)) 459 return const_cast<Constant*>(C1); // undef ashr undef -> undef 460 else 461 return const_cast<Constant*>(C1); // X ashr undef --> X 462 case Instruction::Shl: 463 // undef << X -> 0 or X << undef -> 0 464 return Constant::getNullValue(C1->getType()); 465 } 466 } 467 468 if (const ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 469 if (isa<ConstantExpr>(C2)) { 470 // There are many possible foldings we could do here. We should probably 471 // at least fold add of a pointer with an integer into the appropriate 472 // getelementptr. This will improve alias analysis a bit. 473 } else { 474 // Just implement a couple of simple identities. 475 switch (Opcode) { 476 case Instruction::Add: 477 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X + 0 == X 478 break; 479 case Instruction::Sub: 480 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X - 0 == X 481 break; 482 case Instruction::Mul: 483 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X * 0 == 0 484 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) 485 if (CI->getZExtValue() == 1) 486 return const_cast<Constant*>(C1); // X * 1 == X 487 break; 488 case Instruction::UDiv: 489 case Instruction::SDiv: 490 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) 491 if (CI->getZExtValue() == 1) 492 return const_cast<Constant*>(C1); // X / 1 == X 493 break; 494 case Instruction::URem: 495 case Instruction::SRem: 496 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) 497 if (CI->getZExtValue() == 1) 498 return Constant::getNullValue(CI->getType()); // X % 1 == 0 499 break; 500 case Instruction::And: 501 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) 502 if (CI->isAllOnesValue()) 503 return const_cast<Constant*>(C1); // X & -1 == X 504 if (C2->isNullValue()) return const_cast<Constant*>(C2); // X & 0 == 0 505 if (CE1->isCast() && isa<GlobalValue>(CE1->getOperand(0))) { 506 GlobalValue *CPR = cast<GlobalValue>(CE1->getOperand(0)); 507 508 // Functions are at least 4-byte aligned. If and'ing the address of a 509 // function with a constant < 4, fold it to zero. 510 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) 511 if (CI->getZExtValue() < 4 && isa<Function>(CPR)) 512 return Constant::getNullValue(CI->getType()); 513 } 514 break; 515 case Instruction::Or: 516 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X | 0 == X 517 if (const ConstantInt *CI = dyn_cast<ConstantInt>(C2)) 518 if (CI->isAllOnesValue()) 519 return const_cast<Constant*>(C2); // X | -1 == -1 520 break; 521 case Instruction::Xor: 522 if (C2->isNullValue()) return const_cast<Constant*>(C1); // X ^ 0 == X 523 break; 524 } 525 } 526 } else if (isa<ConstantExpr>(C2)) { 527 // If C2 is a constant expr and C1 isn't, flop them around and fold the 528 // other way if possible. 529 switch (Opcode) { 530 case Instruction::Add: 531 case Instruction::Mul: 532 case Instruction::And: 533 case Instruction::Or: 534 case Instruction::Xor: 535 // No change of opcode required. 536 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 537 538 case Instruction::Shl: 539 case Instruction::LShr: 540 case Instruction::AShr: 541 case Instruction::Sub: 542 case Instruction::SDiv: 543 case Instruction::UDiv: 544 case Instruction::FDiv: 545 case Instruction::URem: 546 case Instruction::SRem: 547 case Instruction::FRem: 548 default: // These instructions cannot be flopped around. 549 return 0; 550 } 551 } 552 553 // At this point we know neither constant is an UndefValue nor a ConstantExpr 554 // so look at directly computing the value. 555 if (const ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 556 if (const ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 557 if (CI1->getType() == Type::Int1Ty && CI2->getType() == Type::Int1Ty) { 558 switch (Opcode) { 559 default: 560 break; 561 case Instruction::And: 562 return ConstantInt::get(Type::Int1Ty, 563 CI1->getZExtValue() & CI2->getZExtValue()); 564 case Instruction::Or: 565 return ConstantInt::get(Type::Int1Ty, 566 CI1->getZExtValue() | CI2->getZExtValue()); 567 case Instruction::Xor: 568 return ConstantInt::get(Type::Int1Ty, 569 CI1->getZExtValue() ^ CI2->getZExtValue()); 570 } 571 } else { 572 uint64_t C1Val = CI1->getZExtValue(); 573 uint64_t C2Val = CI2->getZExtValue(); 574 switch (Opcode) { 575 default: 576 break; 577 case Instruction::Add: 578 return ConstantInt::get(C1->getType(), C1Val + C2Val); 579 case Instruction::Sub: 580 return ConstantInt::get(C1->getType(), C1Val - C2Val); 581 case Instruction::Mul: 582 return ConstantInt::get(C1->getType(), C1Val * C2Val); 583 case Instruction::UDiv: 584 if (CI2->isNullValue()) // X / 0 -> can't fold 585 return 0; 586 return ConstantInt::get(C1->getType(), C1Val / C2Val); 587 case Instruction::SDiv: 588 if (CI2->isNullValue()) return 0; // X / 0 -> can't fold 589 if (CI2->isAllOnesValue() && 590 (((CI1->getType()->getPrimitiveSizeInBits() == 64) && 591 (CI1->getSExtValue() == INT64_MIN)) || 592 (CI1->getSExtValue() == -CI1->getSExtValue()))) 593 return 0; // MIN_INT / -1 -> overflow 594 return ConstantInt::get(C1->getType(), 595 CI1->getSExtValue() / CI2->getSExtValue()); 596 case Instruction::URem: 597 if (C2->isNullValue()) return 0; // X / 0 -> can't fold 598 return ConstantInt::get(C1->getType(), C1Val % C2Val); 599 case Instruction::SRem: 600 if (CI2->isNullValue()) return 0; // X % 0 -> can't fold 601 if (CI2->isAllOnesValue() && 602 (((CI1->getType()->getPrimitiveSizeInBits() == 64) && 603 (CI1->getSExtValue() == INT64_MIN)) || 604 (CI1->getSExtValue() == -CI1->getSExtValue()))) 605 return 0; // MIN_INT % -1 -> overflow 606 return ConstantInt::get(C1->getType(), 607 CI1->getSExtValue() % CI2->getSExtValue()); 608 case Instruction::And: 609 return ConstantInt::get(C1->getType(), C1Val & C2Val); 610 case Instruction::Or: 611 return ConstantInt::get(C1->getType(), C1Val | C2Val); 612 case Instruction::Xor: 613 return ConstantInt::get(C1->getType(), C1Val ^ C2Val); 614 case Instruction::Shl: 615 return ConstantInt::get(C1->getType(), C1Val << C2Val); 616 case Instruction::LShr: 617 return ConstantInt::get(C1->getType(), C1Val >> C2Val); 618 case Instruction::AShr: 619 return ConstantInt::get(C1->getType(), 620 CI1->getSExtValue() >> C2Val); 621 } 622 } 623 } 624 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 625 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 626 double C1Val = CFP1->getValue(); 627 double C2Val = CFP2->getValue(); 628 switch (Opcode) { 629 default: 630 break; 631 case Instruction::Add: 632 return ConstantFP::get(CFP1->getType(), C1Val + C2Val); 633 case Instruction::Sub: 634 return ConstantFP::get(CFP1->getType(), C1Val - C2Val); 635 case Instruction::Mul: 636 return ConstantFP::get(CFP1->getType(), C1Val * C2Val); 637 case Instruction::FDiv: 638 if (CFP2->isExactlyValue(0.0)) 639 return ConstantFP::get(CFP1->getType(), 640 std::numeric_limits<double>::infinity()); 641 if (CFP2->isExactlyValue(-0.0)) 642 return ConstantFP::get(CFP1->getType(), 643 -std::numeric_limits<double>::infinity()); 644 return ConstantFP::get(CFP1->getType(), C1Val / C2Val); 645 case Instruction::FRem: 646 if (CFP2->isNullValue()) 647 return 0; 648 return ConstantFP::get(CFP1->getType(), std::fmod(C1Val, C2Val)); 649 } 650 } 651 } else if (const ConstantPacked *CP1 = dyn_cast<ConstantPacked>(C1)) { 652 if (const ConstantPacked *CP2 = dyn_cast<ConstantPacked>(C2)) { 653 switch (Opcode) { 654 default: 655 break; 656 case Instruction::Add: 657 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd); 658 case Instruction::Sub: 659 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub); 660 case Instruction::Mul: 661 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul); 662 case Instruction::UDiv: 663 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv); 664 case Instruction::SDiv: 665 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv); 666 case Instruction::FDiv: 667 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv); 668 case Instruction::URem: 669 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem); 670 case Instruction::SRem: 671 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem); 672 case Instruction::FRem: 673 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem); 674 case Instruction::And: 675 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd); 676 case Instruction::Or: 677 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr); 678 case Instruction::Xor: 679 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor); 680 } 681 } 682 } 683 684 // We don't know how to fold this 685 return 0; 686} 687 688/// isZeroSizedType - This type is zero sized if its an array or structure of 689/// zero sized types. The only leaf zero sized type is an empty structure. 690static bool isMaybeZeroSizedType(const Type *Ty) { 691 if (isa<OpaqueType>(Ty)) return true; // Can't say. 692 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 693 694 // If all of elements have zero size, this does too. 695 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 696 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 697 return true; 698 699 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 700 return isMaybeZeroSizedType(ATy->getElementType()); 701 } 702 return false; 703} 704 705/// IdxCompare - Compare the two constants as though they were getelementptr 706/// indices. This allows coersion of the types to be the same thing. 707/// 708/// If the two constants are the "same" (after coersion), return 0. If the 709/// first is less than the second, return -1, if the second is less than the 710/// first, return 1. If the constants are not integral, return -2. 711/// 712static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 713 if (C1 == C2) return 0; 714 715 // Ok, we found a different index. If they are not ConstantInt, we can't do 716 // anything with them. 717 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 718 return -2; // don't know! 719 720 // Ok, we have two differing integer indices. Sign extend them to be the same 721 // type. Long is always big enough, so we use it. 722 if (C1->getType() != Type::Int64Ty) 723 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); 724 725 if (C2->getType() != Type::Int64Ty) 726 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); 727 728 if (C1 == C2) return 0; // They are equal 729 730 // If the type being indexed over is really just a zero sized type, there is 731 // no pointer difference being made here. 732 if (isMaybeZeroSizedType(ElTy)) 733 return -2; // dunno. 734 735 // If they are really different, now that they are the same type, then we 736 // found a difference! 737 if (cast<ConstantInt>(C1)->getSExtValue() < 738 cast<ConstantInt>(C2)->getSExtValue()) 739 return -1; 740 else 741 return 1; 742} 743 744/// evaluateFCmpRelation - This function determines if there is anything we can 745/// decide about the two constants provided. This doesn't need to handle simple 746/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 747/// If we can determine that the two constants have a particular relation to 748/// each other, we should return the corresponding FCmpInst predicate, 749/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 750/// ConstantFoldCompareInstruction. 751/// 752/// To simplify this code we canonicalize the relation so that the first 753/// operand is always the most "complex" of the two. We consider ConstantFP 754/// to be the simplest, and ConstantExprs to be the most complex. 755static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, 756 const Constant *V2) { 757 assert(V1->getType() == V2->getType() && 758 "Cannot compare values of different types!"); 759 // Handle degenerate case quickly 760 if (V1 == V2) return FCmpInst::FCMP_OEQ; 761 762 if (!isa<ConstantExpr>(V1)) { 763 if (!isa<ConstantExpr>(V2)) { 764 // We distilled thisUse the standard constant folder for a few cases 765 ConstantInt *R = 0; 766 Constant *C1 = const_cast<Constant*>(V1); 767 Constant *C2 = const_cast<Constant*>(V2); 768 R = dyn_cast<ConstantInt>( 769 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); 770 if (R && R->getZExtValue()) 771 return FCmpInst::FCMP_OEQ; 772 R = dyn_cast<ConstantInt>( 773 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); 774 if (R && R->getZExtValue()) 775 return FCmpInst::FCMP_OLT; 776 R = dyn_cast<ConstantInt>( 777 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); 778 if (R && R->getZExtValue()) 779 return FCmpInst::FCMP_OGT; 780 781 // Nothing more we can do 782 return FCmpInst::BAD_FCMP_PREDICATE; 783 } 784 785 // If the first operand is simple and second is ConstantExpr, swap operands. 786 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 787 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 788 return FCmpInst::getSwappedPredicate(SwappedRelation); 789 } else { 790 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 791 // constantexpr or a simple constant. 792 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 793 switch (CE1->getOpcode()) { 794 case Instruction::FPTrunc: 795 case Instruction::FPExt: 796 case Instruction::UIToFP: 797 case Instruction::SIToFP: 798 // We might be able to do something with these but we don't right now. 799 break; 800 default: 801 break; 802 } 803 } 804 // There are MANY other foldings that we could perform here. They will 805 // probably be added on demand, as they seem needed. 806 return FCmpInst::BAD_FCMP_PREDICATE; 807} 808 809/// evaluateICmpRelation - This function determines if there is anything we can 810/// decide about the two constants provided. This doesn't need to handle simple 811/// things like integer comparisons, but should instead handle ConstantExprs 812/// and GlobalValues. If we can determine that the two constants have a 813/// particular relation to each other, we should return the corresponding ICmp 814/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 815/// 816/// To simplify this code we canonicalize the relation so that the first 817/// operand is always the most "complex" of the two. We consider simple 818/// constants (like ConstantInt) to be the simplest, followed by 819/// GlobalValues, followed by ConstantExpr's (the most complex). 820/// 821static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, 822 const Constant *V2, 823 bool isSigned) { 824 assert(V1->getType() == V2->getType() && 825 "Cannot compare different types of values!"); 826 if (V1 == V2) return ICmpInst::ICMP_EQ; 827 828 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 829 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { 830 // We distilled this down to a simple case, use the standard constant 831 // folder. 832 ConstantInt *R = 0; 833 Constant *C1 = const_cast<Constant*>(V1); 834 Constant *C2 = const_cast<Constant*>(V2); 835 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 836 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 837 if (R && R->getZExtValue()) 838 return pred; 839 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 840 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 841 if (R && R->getZExtValue()) 842 return pred; 843 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 844 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 845 if (R && R->getZExtValue()) 846 return pred; 847 848 // If we couldn't figure it out, bail. 849 return ICmpInst::BAD_ICMP_PREDICATE; 850 } 851 852 // If the first operand is simple, swap operands. 853 ICmpInst::Predicate SwappedRelation = 854 evaluateICmpRelation(V2, V1, isSigned); 855 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 856 return ICmpInst::getSwappedPredicate(SwappedRelation); 857 858 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { 859 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 860 ICmpInst::Predicate SwappedRelation = 861 evaluateICmpRelation(V2, V1, isSigned); 862 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 863 return ICmpInst::getSwappedPredicate(SwappedRelation); 864 else 865 return ICmpInst::BAD_ICMP_PREDICATE; 866 } 867 868 // Now we know that the RHS is a GlobalValue or simple constant, 869 // which (since the types must match) means that it's a ConstantPointerNull. 870 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 871 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) 872 return ICmpInst::ICMP_NE; 873 } else { 874 // GlobalVals can never be null. 875 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 876 if (!CPR1->hasExternalWeakLinkage()) 877 return ICmpInst::ICMP_NE; 878 } 879 } else { 880 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 881 // constantexpr, a CPR, or a simple constant. 882 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 883 const Constant *CE1Op0 = CE1->getOperand(0); 884 885 switch (CE1->getOpcode()) { 886 case Instruction::Trunc: 887 case Instruction::FPTrunc: 888 case Instruction::FPExt: 889 case Instruction::FPToUI: 890 case Instruction::FPToSI: 891 break; // We can't evaluate floating point casts or truncations. 892 893 case Instruction::UIToFP: 894 case Instruction::SIToFP: 895 case Instruction::IntToPtr: 896 case Instruction::BitCast: 897 case Instruction::ZExt: 898 case Instruction::SExt: 899 case Instruction::PtrToInt: 900 // If the cast is not actually changing bits, and the second operand is a 901 // null pointer, do the comparison with the pre-casted value. 902 if (V2->isNullValue() && 903 (isa<PointerType>(CE1->getType()) || CE1->getType()->isIntegral())) { 904 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false : 905 (CE1->getOpcode() == Instruction::SExt ? true : 906 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned)); 907 return evaluateICmpRelation( 908 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd); 909 } 910 911 // If the dest type is a pointer type, and the RHS is a constantexpr cast 912 // from the same type as the src of the LHS, evaluate the inputs. This is 913 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", 914 // which happens a lot in compilers with tagged integers. 915 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) 916 if (CE2->isCast() && isa<PointerType>(CE1->getType()) && 917 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && 918 CE1->getOperand(0)->getType()->isIntegral()) { 919 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false : 920 (CE1->getOpcode() == Instruction::SExt ? true : 921 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned)); 922 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), 923 sgnd); 924 } 925 break; 926 927 case Instruction::GetElementPtr: 928 // Ok, since this is a getelementptr, we know that the constant has a 929 // pointer type. Check the various cases. 930 if (isa<ConstantPointerNull>(V2)) { 931 // If we are comparing a GEP to a null pointer, check to see if the base 932 // of the GEP equals the null pointer. 933 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 934 if (GV->hasExternalWeakLinkage()) 935 // Weak linkage GVals could be zero or not. We're comparing that 936 // to null pointer so its greater-or-equal 937 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 938 else 939 // If its not weak linkage, the GVal must have a non-zero address 940 // so the result is greater-than 941 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 942 } else if (isa<ConstantPointerNull>(CE1Op0)) { 943 // If we are indexing from a null pointer, check to see if we have any 944 // non-zero indices. 945 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 946 if (!CE1->getOperand(i)->isNullValue()) 947 // Offsetting from null, must not be equal. 948 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 949 // Only zero indexes from null, must still be zero. 950 return ICmpInst::ICMP_EQ; 951 } 952 // Otherwise, we can't really say if the first operand is null or not. 953 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 954 if (isa<ConstantPointerNull>(CE1Op0)) { 955 if (CPR2->hasExternalWeakLinkage()) 956 // Weak linkage GVals could be zero or not. We're comparing it to 957 // a null pointer, so its less-or-equal 958 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 959 else 960 // If its not weak linkage, the GVal must have a non-zero address 961 // so the result is less-than 962 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 963 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 964 if (CPR1 == CPR2) { 965 // If this is a getelementptr of the same global, then it must be 966 // different. Because the types must match, the getelementptr could 967 // only have at most one index, and because we fold getelementptr's 968 // with a single zero index, it must be nonzero. 969 assert(CE1->getNumOperands() == 2 && 970 !CE1->getOperand(1)->isNullValue() && 971 "Suprising getelementptr!"); 972 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 973 } else { 974 // If they are different globals, we don't know what the value is, 975 // but they can't be equal. 976 return ICmpInst::ICMP_NE; 977 } 978 } 979 } else { 980 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 981 const Constant *CE2Op0 = CE2->getOperand(0); 982 983 // There are MANY other foldings that we could perform here. They will 984 // probably be added on demand, as they seem needed. 985 switch (CE2->getOpcode()) { 986 default: break; 987 case Instruction::GetElementPtr: 988 // By far the most common case to handle is when the base pointers are 989 // obviously to the same or different globals. 990 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 991 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 992 return ICmpInst::ICMP_NE; 993 // Ok, we know that both getelementptr instructions are based on the 994 // same global. From this, we can precisely determine the relative 995 // ordering of the resultant pointers. 996 unsigned i = 1; 997 998 // Compare all of the operands the GEP's have in common. 999 gep_type_iterator GTI = gep_type_begin(CE1); 1000 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1001 ++i, ++GTI) 1002 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), 1003 GTI.getIndexedType())) { 1004 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1005 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1006 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1007 } 1008 1009 // Ok, we ran out of things they have in common. If any leftovers 1010 // are non-zero then we have a difference, otherwise we are equal. 1011 for (; i < CE1->getNumOperands(); ++i) 1012 if (!CE1->getOperand(i)->isNullValue()) 1013 if (isa<ConstantInt>(CE1->getOperand(i))) 1014 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1015 else 1016 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1017 1018 for (; i < CE2->getNumOperands(); ++i) 1019 if (!CE2->getOperand(i)->isNullValue()) 1020 if (isa<ConstantInt>(CE2->getOperand(i))) 1021 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1022 else 1023 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1024 return ICmpInst::ICMP_EQ; 1025 } 1026 } 1027 } 1028 default: 1029 break; 1030 } 1031 } 1032 1033 return ICmpInst::BAD_ICMP_PREDICATE; 1034} 1035 1036Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1037 const Constant *C1, 1038 const Constant *C2) { 1039 1040 // Handle some degenerate cases first 1041 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) 1042 return UndefValue::get(Type::Int1Ty); 1043 1044 // icmp eq/ne(null,GV) -> false/true 1045 if (C1->isNullValue()) { 1046 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1047 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null 1048 if (pred == ICmpInst::ICMP_EQ) 1049 return ConstantInt::getFalse(); 1050 else if (pred == ICmpInst::ICMP_NE) 1051 return ConstantInt::getTrue(); 1052 // icmp eq/ne(GV,null) -> false/true 1053 } else if (C2->isNullValue()) { 1054 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1055 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null 1056 if (pred == ICmpInst::ICMP_EQ) 1057 return ConstantInt::getFalse(); 1058 else if (pred == ICmpInst::ICMP_NE) 1059 return ConstantInt::getTrue(); 1060 } 1061 1062 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2) && 1063 C1->getType() == Type::Int1Ty && C2->getType() == Type::Int1Ty) { 1064 bool C1Val = cast<ConstantInt>(C1)->getZExtValue(); 1065 bool C2Val = cast<ConstantInt>(C2)->getZExtValue(); 1066 switch (pred) { 1067 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1068 case ICmpInst::ICMP_EQ: 1069 return ConstantInt::get(Type::Int1Ty, C1Val == C2Val); 1070 case ICmpInst::ICMP_NE: 1071 return ConstantInt::get(Type::Int1Ty, C1Val != C2Val); 1072 case ICmpInst::ICMP_ULT: 1073 return ConstantInt::get(Type::Int1Ty, C1Val < C2Val); 1074 case ICmpInst::ICMP_UGT: 1075 return ConstantInt::get(Type::Int1Ty, C1Val > C2Val); 1076 case ICmpInst::ICMP_ULE: 1077 return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val); 1078 case ICmpInst::ICMP_UGE: 1079 return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val); 1080 case ICmpInst::ICMP_SLT: 1081 return ConstantInt::get(Type::Int1Ty, C1Val < C2Val); 1082 case ICmpInst::ICMP_SGT: 1083 return ConstantInt::get(Type::Int1Ty, C1Val > C2Val); 1084 case ICmpInst::ICMP_SLE: 1085 return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val); 1086 case ICmpInst::ICMP_SGE: 1087 return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val); 1088 } 1089 } else if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1090 if (ICmpInst::isSignedPredicate(ICmpInst::Predicate(pred))) { 1091 int64_t V1 = cast<ConstantInt>(C1)->getSExtValue(); 1092 int64_t V2 = cast<ConstantInt>(C2)->getSExtValue(); 1093 switch (pred) { 1094 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1095 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1 < V2); 1096 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1 > V2); 1097 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1 <= V2); 1098 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1 >= V2); 1099 } 1100 } else { 1101 uint64_t V1 = cast<ConstantInt>(C1)->getZExtValue(); 1102 uint64_t V2 = cast<ConstantInt>(C2)->getZExtValue(); 1103 switch (pred) { 1104 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1105 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); 1106 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); 1107 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1 < V2); 1108 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1 > V2); 1109 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1 <= V2); 1110 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1 >= V2); 1111 } 1112 } 1113 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1114 double C1Val = cast<ConstantFP>(C1)->getValue(); 1115 double C2Val = cast<ConstantFP>(C2)->getValue(); 1116 switch (pred) { 1117 default: assert(0 && "Invalid FCmp Predicate"); return 0; 1118 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); 1119 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); 1120 case FCmpInst::FCMP_UNO: 1121 return ConstantInt::get(Type::Int1Ty, C1Val != C1Val || C2Val != C2Val); 1122 case FCmpInst::FCMP_ORD: 1123 return ConstantInt::get(Type::Int1Ty, C1Val == C1Val && C2Val == C2Val); 1124 case FCmpInst::FCMP_UEQ: 1125 if (C1Val != C1Val || C2Val != C2Val) 1126 return ConstantInt::getTrue(); 1127 /* FALL THROUGH */ 1128 case FCmpInst::FCMP_OEQ: 1129 return ConstantInt::get(Type::Int1Ty, C1Val == C2Val); 1130 case FCmpInst::FCMP_UNE: 1131 if (C1Val != C1Val || C2Val != C2Val) 1132 return ConstantInt::getTrue(); 1133 /* FALL THROUGH */ 1134 case FCmpInst::FCMP_ONE: 1135 return ConstantInt::get(Type::Int1Ty, C1Val != C2Val); 1136 case FCmpInst::FCMP_ULT: 1137 if (C1Val != C1Val || C2Val != C2Val) 1138 return ConstantInt::getTrue(); 1139 /* FALL THROUGH */ 1140 case FCmpInst::FCMP_OLT: 1141 return ConstantInt::get(Type::Int1Ty, C1Val < C2Val); 1142 case FCmpInst::FCMP_UGT: 1143 if (C1Val != C1Val || C2Val != C2Val) 1144 return ConstantInt::getTrue(); 1145 /* FALL THROUGH */ 1146 case FCmpInst::FCMP_OGT: 1147 return ConstantInt::get(Type::Int1Ty, C1Val > C2Val); 1148 case FCmpInst::FCMP_ULE: 1149 if (C1Val != C1Val || C2Val != C2Val) 1150 return ConstantInt::getTrue(); 1151 /* FALL THROUGH */ 1152 case FCmpInst::FCMP_OLE: 1153 return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val); 1154 case FCmpInst::FCMP_UGE: 1155 if (C1Val != C1Val || C2Val != C2Val) 1156 return ConstantInt::getTrue(); 1157 /* FALL THROUGH */ 1158 case FCmpInst::FCMP_OGE: 1159 return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val); 1160 } 1161 } else if (const ConstantPacked *CP1 = dyn_cast<ConstantPacked>(C1)) { 1162 if (const ConstantPacked *CP2 = dyn_cast<ConstantPacked>(C2)) { 1163 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) { 1164 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { 1165 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, 1166 const_cast<Constant*>(CP1->getOperand(i)), 1167 const_cast<Constant*>(CP2->getOperand(i))); 1168 if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) 1169 return CB; 1170 } 1171 // Otherwise, could not decide from any element pairs. 1172 return 0; 1173 } else if (pred == ICmpInst::ICMP_EQ) { 1174 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { 1175 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ, 1176 const_cast<Constant*>(CP1->getOperand(i)), 1177 const_cast<Constant*>(CP2->getOperand(i))); 1178 if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) 1179 return CB; 1180 } 1181 // Otherwise, could not decide from any element pairs. 1182 return 0; 1183 } 1184 } 1185 } 1186 1187 if (C1->getType()->isFloatingPoint()) { 1188 switch (evaluateFCmpRelation(C1, C2)) { 1189 default: assert(0 && "Unknown relation!"); 1190 case FCmpInst::FCMP_UNO: 1191 case FCmpInst::FCMP_ORD: 1192 case FCmpInst::FCMP_UEQ: 1193 case FCmpInst::FCMP_UNE: 1194 case FCmpInst::FCMP_ULT: 1195 case FCmpInst::FCMP_UGT: 1196 case FCmpInst::FCMP_ULE: 1197 case FCmpInst::FCMP_UGE: 1198 case FCmpInst::FCMP_TRUE: 1199 case FCmpInst::FCMP_FALSE: 1200 case FCmpInst::BAD_FCMP_PREDICATE: 1201 break; // Couldn't determine anything about these constants. 1202 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1203 return ConstantInt::get(Type::Int1Ty, 1204 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1205 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1206 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1207 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1208 return ConstantInt::get(Type::Int1Ty, 1209 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1210 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1211 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1212 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1213 return ConstantInt::get(Type::Int1Ty, 1214 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1215 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1216 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1217 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1218 // We can only partially decide this relation. 1219 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1220 return ConstantInt::getFalse(); 1221 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1222 return ConstantInt::getTrue(); 1223 break; 1224 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1225 // We can only partially decide this relation. 1226 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1227 return ConstantInt::getFalse(); 1228 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1229 return ConstantInt::getTrue(); 1230 break; 1231 case ICmpInst::ICMP_NE: // We know that C1 != C2 1232 // We can only partially decide this relation. 1233 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1234 return ConstantInt::getFalse(); 1235 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1236 return ConstantInt::getTrue(); 1237 break; 1238 } 1239 } else { 1240 // Evaluate the relation between the two constants, per the predicate. 1241 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1242 default: assert(0 && "Unknown relational!"); 1243 case ICmpInst::BAD_ICMP_PREDICATE: 1244 break; // Couldn't determine anything about these constants. 1245 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1246 // If we know the constants are equal, we can decide the result of this 1247 // computation precisely. 1248 return ConstantInt::get(Type::Int1Ty, 1249 pred == ICmpInst::ICMP_EQ || 1250 pred == ICmpInst::ICMP_ULE || 1251 pred == ICmpInst::ICMP_SLE || 1252 pred == ICmpInst::ICMP_UGE || 1253 pred == ICmpInst::ICMP_SGE); 1254 case ICmpInst::ICMP_ULT: 1255 // If we know that C1 < C2, we can decide the result of this computation 1256 // precisely. 1257 return ConstantInt::get(Type::Int1Ty, 1258 pred == ICmpInst::ICMP_ULT || 1259 pred == ICmpInst::ICMP_NE || 1260 pred == ICmpInst::ICMP_ULE); 1261 case ICmpInst::ICMP_SLT: 1262 // If we know that C1 < C2, we can decide the result of this computation 1263 // precisely. 1264 return ConstantInt::get(Type::Int1Ty, 1265 pred == ICmpInst::ICMP_SLT || 1266 pred == ICmpInst::ICMP_NE || 1267 pred == ICmpInst::ICMP_SLE); 1268 case ICmpInst::ICMP_UGT: 1269 // If we know that C1 > C2, we can decide the result of this computation 1270 // precisely. 1271 return ConstantInt::get(Type::Int1Ty, 1272 pred == ICmpInst::ICMP_UGT || 1273 pred == ICmpInst::ICMP_NE || 1274 pred == ICmpInst::ICMP_UGE); 1275 case ICmpInst::ICMP_SGT: 1276 // If we know that C1 > C2, we can decide the result of this computation 1277 // precisely. 1278 return ConstantInt::get(Type::Int1Ty, 1279 pred == ICmpInst::ICMP_SGT || 1280 pred == ICmpInst::ICMP_NE || 1281 pred == ICmpInst::ICMP_SGE); 1282 case ICmpInst::ICMP_ULE: 1283 // If we know that C1 <= C2, we can only partially decide this relation. 1284 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse(); 1285 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue(); 1286 break; 1287 case ICmpInst::ICMP_SLE: 1288 // If we know that C1 <= C2, we can only partially decide this relation. 1289 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse(); 1290 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue(); 1291 break; 1292 1293 case ICmpInst::ICMP_UGE: 1294 // If we know that C1 >= C2, we can only partially decide this relation. 1295 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse(); 1296 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue(); 1297 break; 1298 case ICmpInst::ICMP_SGE: 1299 // If we know that C1 >= C2, we can only partially decide this relation. 1300 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse(); 1301 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue(); 1302 break; 1303 1304 case ICmpInst::ICMP_NE: 1305 // If we know that C1 != C2, we can only partially decide this relation. 1306 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(); 1307 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(); 1308 break; 1309 } 1310 1311 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) { 1312 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1313 // other way if possible. 1314 switch (pred) { 1315 case ICmpInst::ICMP_EQ: 1316 case ICmpInst::ICMP_NE: 1317 // No change of predicate required. 1318 return ConstantFoldCompareInstruction(pred, C2, C1); 1319 1320 case ICmpInst::ICMP_ULT: 1321 case ICmpInst::ICMP_SLT: 1322 case ICmpInst::ICMP_UGT: 1323 case ICmpInst::ICMP_SGT: 1324 case ICmpInst::ICMP_ULE: 1325 case ICmpInst::ICMP_SLE: 1326 case ICmpInst::ICMP_UGE: 1327 case ICmpInst::ICMP_SGE: 1328 // Change the predicate as necessary to swap the operands. 1329 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1330 return ConstantFoldCompareInstruction(pred, C2, C1); 1331 1332 default: // These predicates cannot be flopped around. 1333 break; 1334 } 1335 } 1336 } 1337 return 0; 1338} 1339 1340Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 1341 const std::vector<Value*> &IdxList) { 1342 if (IdxList.size() == 0 || 1343 (IdxList.size() == 1 && cast<Constant>(IdxList[0])->isNullValue())) 1344 return const_cast<Constant*>(C); 1345 1346 if (isa<UndefValue>(C)) { 1347 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList, 1348 true); 1349 assert(Ty != 0 && "Invalid indices for GEP!"); 1350 return UndefValue::get(PointerType::get(Ty)); 1351 } 1352 1353 Constant *Idx0 = cast<Constant>(IdxList[0]); 1354 if (C->isNullValue()) { 1355 bool isNull = true; 1356 for (unsigned i = 0, e = IdxList.size(); i != e; ++i) 1357 if (!cast<Constant>(IdxList[i])->isNullValue()) { 1358 isNull = false; 1359 break; 1360 } 1361 if (isNull) { 1362 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), IdxList, 1363 true); 1364 assert(Ty != 0 && "Invalid indices for GEP!"); 1365 return ConstantPointerNull::get(PointerType::get(Ty)); 1366 } 1367 1368 if (IdxList.size() == 1) { 1369 const Type *ElTy = cast<PointerType>(C->getType())->getElementType(); 1370 if (uint32_t ElSize = ElTy->getPrimitiveSize()) { 1371 // gep null, C is equal to C*sizeof(nullty). If nullty is a known llvm 1372 // type, we can statically fold this. 1373 Constant *R = ConstantInt::get(Type::Int32Ty, ElSize); 1374 // We know R is unsigned, Idx0 is signed because it must be an index 1375 // through a sequential type (gep pointer operand) which is always 1376 // signed. 1377 R = ConstantExpr::getSExtOrBitCast(R, Idx0->getType()); 1378 R = ConstantExpr::getMul(R, Idx0); // signed multiply 1379 // R is a signed integer, C is the GEP pointer so -> IntToPtr 1380 return ConstantExpr::getIntToPtr(R, C->getType()); 1381 } 1382 } 1383 } 1384 1385 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 1386 // Combine Indices - If the source pointer to this getelementptr instruction 1387 // is a getelementptr instruction, combine the indices of the two 1388 // getelementptr instructions into a single instruction. 1389 // 1390 if (CE->getOpcode() == Instruction::GetElementPtr) { 1391 const Type *LastTy = 0; 1392 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1393 I != E; ++I) 1394 LastTy = *I; 1395 1396 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 1397 std::vector<Value*> NewIndices; 1398 NewIndices.reserve(IdxList.size() + CE->getNumOperands()); 1399 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 1400 NewIndices.push_back(CE->getOperand(i)); 1401 1402 // Add the last index of the source with the first index of the new GEP. 1403 // Make sure to handle the case when they are actually different types. 1404 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 1405 // Otherwise it must be an array. 1406 if (!Idx0->isNullValue()) { 1407 const Type *IdxTy = Combined->getType(); 1408 if (IdxTy != Idx0->getType()) { 1409 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); 1410 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, 1411 Type::Int64Ty); 1412 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 1413 } else { 1414 Combined = 1415 ConstantExpr::get(Instruction::Add, Idx0, Combined); 1416 } 1417 } 1418 1419 NewIndices.push_back(Combined); 1420 NewIndices.insert(NewIndices.end(), IdxList.begin()+1, IdxList.end()); 1421 return ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices); 1422 } 1423 } 1424 1425 // Implement folding of: 1426 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 1427 // long 0, long 0) 1428 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 1429 // 1430 if (CE->isCast() && IdxList.size() > 1 && Idx0->isNullValue()) 1431 if (const PointerType *SPT = 1432 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 1433 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 1434 if (const ArrayType *CAT = 1435 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 1436 if (CAT->getElementType() == SAT->getElementType()) 1437 return ConstantExpr::getGetElementPtr( 1438 (Constant*)CE->getOperand(0), IdxList); 1439 } 1440 return 0; 1441} 1442 1443