ConstantFold.cpp revision 92f6feaf792469130eec7196854ff01215955964
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 "ConstantFold.h" 22#include "llvm/Constants.h" 23#include "llvm/Instructions.h" 24#include "llvm/DerivedTypes.h" 25#include "llvm/Function.h" 26#include "llvm/ADT/SmallVector.h" 27#include "llvm/Support/Compiler.h" 28#include "llvm/Support/GetElementPtrTypeIterator.h" 29#include "llvm/Support/ManagedStatic.h" 30#include "llvm/Support/MathExtras.h" 31#include <limits> 32using namespace llvm; 33 34//===----------------------------------------------------------------------===// 35// ConstantFold*Instruction Implementations 36//===----------------------------------------------------------------------===// 37 38/// CastConstantVector - Convert the specified ConstantVector node to the 39/// specified vector type. At this point, we know that the elements of the 40/// input packed constant are all simple integer or FP values. 41static Constant *CastConstantVector(ConstantVector *CP, 42 const VectorType *DstTy) { 43 unsigned SrcNumElts = CP->getType()->getNumElements(); 44 unsigned DstNumElts = DstTy->getNumElements(); 45 const Type *SrcEltTy = CP->getType()->getElementType(); 46 const Type *DstEltTy = DstTy->getElementType(); 47 48 // If both vectors have the same number of elements (thus, the elements 49 // are the same size), perform the conversion now. 50 if (SrcNumElts == DstNumElts) { 51 std::vector<Constant*> Result; 52 53 // If the src and dest elements are both integers, or both floats, we can 54 // just BitCast each element because the elements are the same size. 55 if ((SrcEltTy->isInteger() && DstEltTy->isInteger()) || 56 (SrcEltTy->isFloatingPoint() && DstEltTy->isFloatingPoint())) { 57 for (unsigned i = 0; i != SrcNumElts; ++i) 58 Result.push_back( 59 ConstantExpr::getBitCast(CP->getOperand(i), DstEltTy)); 60 return ConstantVector::get(Result); 61 } 62 63 // If this is an int-to-fp cast .. 64 if (SrcEltTy->isInteger()) { 65 // Ensure that it is int-to-fp cast 66 assert(DstEltTy->isFloatingPoint()); 67 if (DstEltTy->getTypeID() == Type::DoubleTyID) { 68 for (unsigned i = 0; i != SrcNumElts; ++i) { 69 double V = 70 BitsToDouble(cast<ConstantInt>(CP->getOperand(i))->getZExtValue()); 71 Result.push_back(ConstantFP::get(Type::DoubleTy, V)); 72 } 73 return ConstantVector::get(Result); 74 } 75 assert(DstEltTy == Type::FloatTy && "Unknown fp type!"); 76 for (unsigned i = 0; i != SrcNumElts; ++i) { 77 float V = 78 BitsToFloat(cast<ConstantInt>(CP->getOperand(i))->getZExtValue()); 79 Result.push_back(ConstantFP::get(Type::FloatTy, V)); 80 } 81 return ConstantVector::get(Result); 82 } 83 84 // Otherwise, this is an fp-to-int cast. 85 assert(SrcEltTy->isFloatingPoint() && DstEltTy->isInteger()); 86 87 if (SrcEltTy->getTypeID() == Type::DoubleTyID) { 88 for (unsigned i = 0; i != SrcNumElts; ++i) { 89 uint64_t V = 90 DoubleToBits(cast<ConstantFP>(CP->getOperand(i))->getValue()); 91 Constant *C = ConstantInt::get(Type::Int64Ty, V); 92 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy )); 93 } 94 return ConstantVector::get(Result); 95 } 96 97 assert(SrcEltTy->getTypeID() == Type::FloatTyID); 98 for (unsigned i = 0; i != SrcNumElts; ++i) { 99 uint32_t V = FloatToBits(cast<ConstantFP>(CP->getOperand(i))->getValue()); 100 Constant *C = ConstantInt::get(Type::Int32Ty, V); 101 Result.push_back(ConstantExpr::getBitCast(C, DstEltTy)); 102 } 103 return ConstantVector::get(Result); 104 } 105 106 // Otherwise, this is a cast that changes element count and size. Handle 107 // casts which shrink the elements here. 108 109 // FIXME: We need to know endianness to do this! 110 111 return 0; 112} 113 114/// This function determines which opcode to use to fold two constant cast 115/// expressions together. It uses CastInst::isEliminableCastPair to determine 116/// the opcode. Consequently its just a wrapper around that function. 117/// @Determine if it is valid to fold a cast of a cast 118static unsigned 119foldConstantCastPair( 120 unsigned opc, ///< opcode of the second cast constant expression 121 const ConstantExpr*Op, ///< the first cast constant expression 122 const Type *DstTy ///< desintation type of the first cast 123) { 124 assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); 125 assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); 126 assert(CastInst::isCast(opc) && "Invalid cast opcode"); 127 128 // The the types and opcodes for the two Cast constant expressions 129 const Type *SrcTy = Op->getOperand(0)->getType(); 130 const Type *MidTy = Op->getType(); 131 Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); 132 Instruction::CastOps secondOp = Instruction::CastOps(opc); 133 134 // Let CastInst::isEliminableCastPair do the heavy lifting. 135 return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, 136 Type::Int64Ty); 137} 138 139Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V, 140 const Type *DestTy) { 141 const Type *SrcTy = V->getType(); 142 143 if (isa<UndefValue>(V)) 144 return UndefValue::get(DestTy); 145 146 // If the cast operand is a constant expression, there's a few things we can 147 // do to try to simplify it. 148 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 149 if (CE->isCast()) { 150 // Try hard to fold cast of cast because they are often eliminable. 151 if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 152 return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 153 } else if (CE->getOpcode() == Instruction::GetElementPtr) { 154 // If all of the indexes in the GEP are null values, there is no pointer 155 // adjustment going on. We might as well cast the source pointer. 156 bool isAllNull = true; 157 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 158 if (!CE->getOperand(i)->isNullValue()) { 159 isAllNull = false; 160 break; 161 } 162 if (isAllNull) 163 // This is casting one pointer type to another, always BitCast 164 return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 165 } 166 } 167 168 // We actually have to do a cast now. Perform the cast according to the 169 // opcode specified. 170 switch (opc) { 171 case Instruction::FPTrunc: 172 case Instruction::FPExt: 173 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) 174 return ConstantFP::get(DestTy, FPC->getValue()); 175 return 0; // Can't fold. 176 case Instruction::FPToUI: 177 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) 178 return ConstantInt::get(DestTy,(uint64_t) FPC->getValue()); 179 return 0; // Can't fold. 180 case Instruction::FPToSI: 181 if (const ConstantFP *FPC = dyn_cast<ConstantFP>(V)) 182 return ConstantInt::get(DestTy,(int64_t) FPC->getValue()); 183 return 0; // Can't fold. 184 case Instruction::IntToPtr: //always treated as unsigned 185 if (V->isNullValue()) // Is it an integral null value? 186 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 187 return 0; // Other pointer types cannot be casted 188 case Instruction::PtrToInt: // always treated as unsigned 189 if (V->isNullValue()) // is it a null pointer value? 190 return ConstantInt::get(DestTy, 0); 191 return 0; // Other pointer types cannot be casted 192 case Instruction::UIToFP: 193 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) 194 return ConstantFP::get(DestTy, double(CI->getZExtValue())); 195 return 0; 196 case Instruction::SIToFP: 197 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) 198 return ConstantFP::get(DestTy, double(CI->getSExtValue())); 199 return 0; 200 case Instruction::ZExt: 201 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) 202 return ConstantInt::get(DestTy, CI->getZExtValue()); 203 return 0; 204 case Instruction::SExt: 205 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) 206 return ConstantInt::get(DestTy, CI->getSExtValue()); 207 return 0; 208 case Instruction::Trunc: 209 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) // Can't trunc a bool 210 return ConstantInt::get(DestTy, CI->getZExtValue()); 211 return 0; 212 case Instruction::BitCast: 213 if (SrcTy == DestTy) 214 return (Constant*)V; // no-op cast 215 216 // Check to see if we are casting a pointer to an aggregate to a pointer to 217 // the first element. If so, return the appropriate GEP instruction. 218 if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) 219 if (const PointerType *DPTy = dyn_cast<PointerType>(DestTy)) { 220 SmallVector<Value*, 8> IdxList; 221 IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); 222 const Type *ElTy = PTy->getElementType(); 223 while (ElTy != DPTy->getElementType()) { 224 if (const StructType *STy = dyn_cast<StructType>(ElTy)) { 225 if (STy->getNumElements() == 0) break; 226 ElTy = STy->getElementType(0); 227 IdxList.push_back(Constant::getNullValue(Type::Int32Ty)); 228 } else if (const SequentialType *STy = 229 dyn_cast<SequentialType>(ElTy)) { 230 if (isa<PointerType>(ElTy)) break; // Can't index into pointers! 231 ElTy = STy->getElementType(); 232 IdxList.push_back(IdxList[0]); 233 } else { 234 break; 235 } 236 } 237 238 if (ElTy == DPTy->getElementType()) 239 return ConstantExpr::getGetElementPtr( 240 const_cast<Constant*>(V), &IdxList[0], IdxList.size()); 241 } 242 243 // Handle casts from one packed constant to another. We know that the src 244 // and dest type have the same size (otherwise its an illegal cast). 245 if (const VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { 246 if (const VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { 247 assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && 248 "Not cast between same sized vectors!"); 249 // First, check for null and undef 250 if (isa<ConstantAggregateZero>(V)) 251 return Constant::getNullValue(DestTy); 252 if (isa<UndefValue>(V)) 253 return UndefValue::get(DestTy); 254 255 if (const ConstantVector *CP = dyn_cast<ConstantVector>(V)) { 256 // This is a cast from a ConstantVector of one type to a 257 // ConstantVector of another type. Check to see if all elements of 258 // the input are simple. 259 bool AllSimpleConstants = true; 260 for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i) { 261 if (!isa<ConstantInt>(CP->getOperand(i)) && 262 !isa<ConstantFP>(CP->getOperand(i))) { 263 AllSimpleConstants = false; 264 break; 265 } 266 } 267 268 // If all of the elements are simple constants, we can fold this. 269 if (AllSimpleConstants) 270 return CastConstantVector(const_cast<ConstantVector*>(CP), DestPTy); 271 } 272 } 273 } 274 275 // Finally, implement bitcast folding now. The code below doesn't handle 276 // bitcast right. 277 if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 278 return ConstantPointerNull::get(cast<PointerType>(DestTy)); 279 280 // Handle integral constant input. 281 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 282 // Integral -> Integral, must be changing sign. 283 if (DestTy->isInteger()) 284 return ConstantInt::get(DestTy, CI->getZExtValue()); 285 286 if (DestTy->isFloatingPoint()) { 287 if (DestTy == Type::FloatTy) 288 return ConstantFP::get(DestTy, BitsToFloat(CI->getZExtValue())); 289 assert(DestTy == Type::DoubleTy && "Unknown FP type!"); 290 return ConstantFP::get(DestTy, BitsToDouble(CI->getZExtValue())); 291 } 292 // Otherwise, can't fold this (packed?) 293 return 0; 294 } 295 296 // Handle ConstantFP input. 297 if (const ConstantFP *FP = dyn_cast<ConstantFP>(V)) { 298 // FP -> Integral. 299 if (DestTy == Type::Int32Ty) { 300 return ConstantInt::get(DestTy, FloatToBits(FP->getValue())); 301 } else { 302 assert(DestTy == Type::Int64Ty && "only support f32/f64 for now!"); 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<VectorType>(Val->getType())->getElementType()); 333 if (Val->isNullValue()) // ee(zero, x) -> zero 334 return Constant::getNullValue( 335 cast<VectorType>(Val->getType())->getElementType()); 336 337 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(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<VectorType>(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 ConstantVector::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<VectorType>(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 ConstantVector::get(Ops); 389 } 390 if (const ConstantVector *CVal = dyn_cast<ConstantVector>(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 ConstantVector::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 ConstantVector 413/// constant. 414static Constant *EvalVectorOp(const ConstantVector *V1, 415 const ConstantVector *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 ConstantVector::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 VectorType *PTy = dyn_cast<VectorType>(C1->getType())) 448 return ConstantVector::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 uint64_t C1Val = CI1->getZExtValue(); 558 uint64_t C2Val = CI2->getZExtValue(); 559 switch (Opcode) { 560 default: 561 break; 562 case Instruction::Add: 563 return ConstantInt::get(C1->getType(), C1Val + C2Val); 564 case Instruction::Sub: 565 return ConstantInt::get(C1->getType(), C1Val - C2Val); 566 case Instruction::Mul: 567 return ConstantInt::get(C1->getType(), C1Val * C2Val); 568 case Instruction::UDiv: 569 if (CI2->isNullValue()) // X / 0 -> can't fold 570 return 0; 571 return ConstantInt::get(C1->getType(), C1Val / C2Val); 572 case Instruction::SDiv: 573 if (CI2->isNullValue()) return 0; // X / 0 -> can't fold 574 if (CI2->isAllOnesValue() && 575 (((CI1->getType()->getPrimitiveSizeInBits() == 64) && 576 (CI1->getSExtValue() == INT64_MIN)) || 577 (CI1->getSExtValue() == -CI1->getSExtValue() && 578 CI1->getSExtValue()))) 579 return 0; // MIN_INT / -1 -> overflow 580 return ConstantInt::get(C1->getType(), 581 CI1->getSExtValue() / CI2->getSExtValue()); 582 case Instruction::URem: 583 if (C2->isNullValue()) return 0; // X / 0 -> can't fold 584 return ConstantInt::get(C1->getType(), C1Val % C2Val); 585 case Instruction::SRem: 586 if (CI2->isNullValue()) return 0; // X % 0 -> can't fold 587 if (CI2->isAllOnesValue() && 588 (((CI1->getType()->getPrimitiveSizeInBits() == 64) && 589 (CI1->getSExtValue() == INT64_MIN)) || 590 (CI1->getSExtValue() == -CI1->getSExtValue()))) 591 return 0; // MIN_INT % -1 -> overflow 592 return ConstantInt::get(C1->getType(), 593 CI1->getSExtValue() % CI2->getSExtValue()); 594 case Instruction::And: 595 return ConstantInt::get(C1->getType(), C1Val & C2Val); 596 case Instruction::Or: 597 return ConstantInt::get(C1->getType(), C1Val | C2Val); 598 case Instruction::Xor: 599 return ConstantInt::get(C1->getType(), C1Val ^ C2Val); 600 case Instruction::Shl: 601 return ConstantInt::get(C1->getType(), C1Val << C2Val); 602 case Instruction::LShr: 603 return ConstantInt::get(C1->getType(), C1Val >> C2Val); 604 case Instruction::AShr: 605 return ConstantInt::get(C1->getType(), 606 CI1->getSExtValue() >> C2Val); 607 } 608 } 609 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 610 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 611 double C1Val = CFP1->getValue(); 612 double C2Val = CFP2->getValue(); 613 switch (Opcode) { 614 default: 615 break; 616 case Instruction::Add: 617 return ConstantFP::get(CFP1->getType(), C1Val + C2Val); 618 case Instruction::Sub: 619 return ConstantFP::get(CFP1->getType(), C1Val - C2Val); 620 case Instruction::Mul: 621 return ConstantFP::get(CFP1->getType(), C1Val * C2Val); 622 case Instruction::FDiv: 623 if (CFP2->isExactlyValue(0.0)) 624 return ConstantFP::get(CFP1->getType(), 625 std::numeric_limits<double>::infinity()); 626 if (CFP2->isExactlyValue(-0.0)) 627 return ConstantFP::get(CFP1->getType(), 628 -std::numeric_limits<double>::infinity()); 629 return ConstantFP::get(CFP1->getType(), C1Val / C2Val); 630 case Instruction::FRem: 631 if (CFP2->isNullValue()) 632 return 0; 633 return ConstantFP::get(CFP1->getType(), std::fmod(C1Val, C2Val)); 634 } 635 } 636 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) { 637 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) { 638 switch (Opcode) { 639 default: 640 break; 641 case Instruction::Add: 642 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd); 643 case Instruction::Sub: 644 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub); 645 case Instruction::Mul: 646 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul); 647 case Instruction::UDiv: 648 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv); 649 case Instruction::SDiv: 650 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv); 651 case Instruction::FDiv: 652 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv); 653 case Instruction::URem: 654 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem); 655 case Instruction::SRem: 656 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem); 657 case Instruction::FRem: 658 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem); 659 case Instruction::And: 660 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd); 661 case Instruction::Or: 662 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr); 663 case Instruction::Xor: 664 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor); 665 } 666 } 667 } 668 669 // We don't know how to fold this 670 return 0; 671} 672 673/// isZeroSizedType - This type is zero sized if its an array or structure of 674/// zero sized types. The only leaf zero sized type is an empty structure. 675static bool isMaybeZeroSizedType(const Type *Ty) { 676 if (isa<OpaqueType>(Ty)) return true; // Can't say. 677 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 678 679 // If all of elements have zero size, this does too. 680 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 681 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 682 return true; 683 684 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 685 return isMaybeZeroSizedType(ATy->getElementType()); 686 } 687 return false; 688} 689 690/// IdxCompare - Compare the two constants as though they were getelementptr 691/// indices. This allows coersion of the types to be the same thing. 692/// 693/// If the two constants are the "same" (after coersion), return 0. If the 694/// first is less than the second, return -1, if the second is less than the 695/// first, return 1. If the constants are not integral, return -2. 696/// 697static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 698 if (C1 == C2) return 0; 699 700 // Ok, we found a different index. If they are not ConstantInt, we can't do 701 // anything with them. 702 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 703 return -2; // don't know! 704 705 // Ok, we have two differing integer indices. Sign extend them to be the same 706 // type. Long is always big enough, so we use it. 707 if (C1->getType() != Type::Int64Ty) 708 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); 709 710 if (C2->getType() != Type::Int64Ty) 711 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); 712 713 if (C1 == C2) return 0; // They are equal 714 715 // If the type being indexed over is really just a zero sized type, there is 716 // no pointer difference being made here. 717 if (isMaybeZeroSizedType(ElTy)) 718 return -2; // dunno. 719 720 // If they are really different, now that they are the same type, then we 721 // found a difference! 722 if (cast<ConstantInt>(C1)->getSExtValue() < 723 cast<ConstantInt>(C2)->getSExtValue()) 724 return -1; 725 else 726 return 1; 727} 728 729/// evaluateFCmpRelation - This function determines if there is anything we can 730/// decide about the two constants provided. This doesn't need to handle simple 731/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 732/// If we can determine that the two constants have a particular relation to 733/// each other, we should return the corresponding FCmpInst predicate, 734/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 735/// ConstantFoldCompareInstruction. 736/// 737/// To simplify this code we canonicalize the relation so that the first 738/// operand is always the most "complex" of the two. We consider ConstantFP 739/// to be the simplest, and ConstantExprs to be the most complex. 740static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, 741 const Constant *V2) { 742 assert(V1->getType() == V2->getType() && 743 "Cannot compare values of different types!"); 744 // Handle degenerate case quickly 745 if (V1 == V2) return FCmpInst::FCMP_OEQ; 746 747 if (!isa<ConstantExpr>(V1)) { 748 if (!isa<ConstantExpr>(V2)) { 749 // We distilled thisUse the standard constant folder for a few cases 750 ConstantInt *R = 0; 751 Constant *C1 = const_cast<Constant*>(V1); 752 Constant *C2 = const_cast<Constant*>(V2); 753 R = dyn_cast<ConstantInt>( 754 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); 755 if (R && R->getZExtValue()) 756 return FCmpInst::FCMP_OEQ; 757 R = dyn_cast<ConstantInt>( 758 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); 759 if (R && R->getZExtValue()) 760 return FCmpInst::FCMP_OLT; 761 R = dyn_cast<ConstantInt>( 762 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); 763 if (R && R->getZExtValue()) 764 return FCmpInst::FCMP_OGT; 765 766 // Nothing more we can do 767 return FCmpInst::BAD_FCMP_PREDICATE; 768 } 769 770 // If the first operand is simple and second is ConstantExpr, swap operands. 771 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 772 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 773 return FCmpInst::getSwappedPredicate(SwappedRelation); 774 } else { 775 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 776 // constantexpr or a simple constant. 777 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 778 switch (CE1->getOpcode()) { 779 case Instruction::FPTrunc: 780 case Instruction::FPExt: 781 case Instruction::UIToFP: 782 case Instruction::SIToFP: 783 // We might be able to do something with these but we don't right now. 784 break; 785 default: 786 break; 787 } 788 } 789 // There are MANY other foldings that we could perform here. They will 790 // probably be added on demand, as they seem needed. 791 return FCmpInst::BAD_FCMP_PREDICATE; 792} 793 794/// evaluateICmpRelation - This function determines if there is anything we can 795/// decide about the two constants provided. This doesn't need to handle simple 796/// things like integer comparisons, but should instead handle ConstantExprs 797/// and GlobalValues. If we can determine that the two constants have a 798/// particular relation to each other, we should return the corresponding ICmp 799/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 800/// 801/// To simplify this code we canonicalize the relation so that the first 802/// operand is always the most "complex" of the two. We consider simple 803/// constants (like ConstantInt) to be the simplest, followed by 804/// GlobalValues, followed by ConstantExpr's (the most complex). 805/// 806static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, 807 const Constant *V2, 808 bool isSigned) { 809 assert(V1->getType() == V2->getType() && 810 "Cannot compare different types of values!"); 811 if (V1 == V2) return ICmpInst::ICMP_EQ; 812 813 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 814 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { 815 // We distilled this down to a simple case, use the standard constant 816 // folder. 817 ConstantInt *R = 0; 818 Constant *C1 = const_cast<Constant*>(V1); 819 Constant *C2 = const_cast<Constant*>(V2); 820 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 821 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 822 if (R && R->getZExtValue()) 823 return pred; 824 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 825 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 826 if (R && R->getZExtValue()) 827 return pred; 828 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 829 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 830 if (R && R->getZExtValue()) 831 return pred; 832 833 // If we couldn't figure it out, bail. 834 return ICmpInst::BAD_ICMP_PREDICATE; 835 } 836 837 // If the first operand is simple, swap operands. 838 ICmpInst::Predicate SwappedRelation = 839 evaluateICmpRelation(V2, V1, isSigned); 840 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 841 return ICmpInst::getSwappedPredicate(SwappedRelation); 842 843 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { 844 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 845 ICmpInst::Predicate SwappedRelation = 846 evaluateICmpRelation(V2, V1, isSigned); 847 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 848 return ICmpInst::getSwappedPredicate(SwappedRelation); 849 else 850 return ICmpInst::BAD_ICMP_PREDICATE; 851 } 852 853 // Now we know that the RHS is a GlobalValue or simple constant, 854 // which (since the types must match) means that it's a ConstantPointerNull. 855 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 856 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) 857 return ICmpInst::ICMP_NE; 858 } else { 859 // GlobalVals can never be null. 860 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 861 if (!CPR1->hasExternalWeakLinkage()) 862 return ICmpInst::ICMP_NE; 863 } 864 } else { 865 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 866 // constantexpr, a CPR, or a simple constant. 867 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 868 const Constant *CE1Op0 = CE1->getOperand(0); 869 870 switch (CE1->getOpcode()) { 871 case Instruction::Trunc: 872 case Instruction::FPTrunc: 873 case Instruction::FPExt: 874 case Instruction::FPToUI: 875 case Instruction::FPToSI: 876 break; // We can't evaluate floating point casts or truncations. 877 878 case Instruction::UIToFP: 879 case Instruction::SIToFP: 880 case Instruction::IntToPtr: 881 case Instruction::BitCast: 882 case Instruction::ZExt: 883 case Instruction::SExt: 884 case Instruction::PtrToInt: 885 // If the cast is not actually changing bits, and the second operand is a 886 // null pointer, do the comparison with the pre-casted value. 887 if (V2->isNullValue() && 888 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) { 889 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false : 890 (CE1->getOpcode() == Instruction::SExt ? true : 891 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned)); 892 return evaluateICmpRelation( 893 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd); 894 } 895 896 // If the dest type is a pointer type, and the RHS is a constantexpr cast 897 // from the same type as the src of the LHS, evaluate the inputs. This is 898 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", 899 // which happens a lot in compilers with tagged integers. 900 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) 901 if (CE2->isCast() && isa<PointerType>(CE1->getType()) && 902 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && 903 CE1->getOperand(0)->getType()->isInteger()) { 904 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false : 905 (CE1->getOpcode() == Instruction::SExt ? true : 906 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned)); 907 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), 908 sgnd); 909 } 910 break; 911 912 case Instruction::GetElementPtr: 913 // Ok, since this is a getelementptr, we know that the constant has a 914 // pointer type. Check the various cases. 915 if (isa<ConstantPointerNull>(V2)) { 916 // If we are comparing a GEP to a null pointer, check to see if the base 917 // of the GEP equals the null pointer. 918 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 919 if (GV->hasExternalWeakLinkage()) 920 // Weak linkage GVals could be zero or not. We're comparing that 921 // to null pointer so its greater-or-equal 922 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 923 else 924 // If its not weak linkage, the GVal must have a non-zero address 925 // so the result is greater-than 926 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 927 } else if (isa<ConstantPointerNull>(CE1Op0)) { 928 // If we are indexing from a null pointer, check to see if we have any 929 // non-zero indices. 930 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 931 if (!CE1->getOperand(i)->isNullValue()) 932 // Offsetting from null, must not be equal. 933 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 934 // Only zero indexes from null, must still be zero. 935 return ICmpInst::ICMP_EQ; 936 } 937 // Otherwise, we can't really say if the first operand is null or not. 938 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 939 if (isa<ConstantPointerNull>(CE1Op0)) { 940 if (CPR2->hasExternalWeakLinkage()) 941 // Weak linkage GVals could be zero or not. We're comparing it to 942 // a null pointer, so its less-or-equal 943 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 944 else 945 // If its not weak linkage, the GVal must have a non-zero address 946 // so the result is less-than 947 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 948 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 949 if (CPR1 == CPR2) { 950 // If this is a getelementptr of the same global, then it must be 951 // different. Because the types must match, the getelementptr could 952 // only have at most one index, and because we fold getelementptr's 953 // with a single zero index, it must be nonzero. 954 assert(CE1->getNumOperands() == 2 && 955 !CE1->getOperand(1)->isNullValue() && 956 "Suprising getelementptr!"); 957 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 958 } else { 959 // If they are different globals, we don't know what the value is, 960 // but they can't be equal. 961 return ICmpInst::ICMP_NE; 962 } 963 } 964 } else { 965 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 966 const Constant *CE2Op0 = CE2->getOperand(0); 967 968 // There are MANY other foldings that we could perform here. They will 969 // probably be added on demand, as they seem needed. 970 switch (CE2->getOpcode()) { 971 default: break; 972 case Instruction::GetElementPtr: 973 // By far the most common case to handle is when the base pointers are 974 // obviously to the same or different globals. 975 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 976 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 977 return ICmpInst::ICMP_NE; 978 // Ok, we know that both getelementptr instructions are based on the 979 // same global. From this, we can precisely determine the relative 980 // ordering of the resultant pointers. 981 unsigned i = 1; 982 983 // Compare all of the operands the GEP's have in common. 984 gep_type_iterator GTI = gep_type_begin(CE1); 985 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 986 ++i, ++GTI) 987 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), 988 GTI.getIndexedType())) { 989 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 990 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 991 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 992 } 993 994 // Ok, we ran out of things they have in common. If any leftovers 995 // are non-zero then we have a difference, otherwise we are equal. 996 for (; i < CE1->getNumOperands(); ++i) 997 if (!CE1->getOperand(i)->isNullValue()) 998 if (isa<ConstantInt>(CE1->getOperand(i))) 999 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1000 else 1001 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1002 1003 for (; i < CE2->getNumOperands(); ++i) 1004 if (!CE2->getOperand(i)->isNullValue()) 1005 if (isa<ConstantInt>(CE2->getOperand(i))) 1006 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1007 else 1008 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1009 return ICmpInst::ICMP_EQ; 1010 } 1011 } 1012 } 1013 default: 1014 break; 1015 } 1016 } 1017 1018 return ICmpInst::BAD_ICMP_PREDICATE; 1019} 1020 1021Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1022 const Constant *C1, 1023 const Constant *C2) { 1024 1025 // Handle some degenerate cases first 1026 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) 1027 return UndefValue::get(Type::Int1Ty); 1028 1029 // icmp eq/ne(null,GV) -> false/true 1030 if (C1->isNullValue()) { 1031 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1032 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null 1033 if (pred == ICmpInst::ICMP_EQ) 1034 return ConstantInt::getFalse(); 1035 else if (pred == ICmpInst::ICMP_NE) 1036 return ConstantInt::getTrue(); 1037 // icmp eq/ne(GV,null) -> false/true 1038 } else if (C2->isNullValue()) { 1039 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1040 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null 1041 if (pred == ICmpInst::ICMP_EQ) 1042 return ConstantInt::getFalse(); 1043 else if (pred == ICmpInst::ICMP_NE) 1044 return ConstantInt::getTrue(); 1045 } 1046 1047 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1048 if (ICmpInst::isSignedPredicate(ICmpInst::Predicate(pred))) { 1049 int64_t V1 = cast<ConstantInt>(C1)->getSExtValue(); 1050 int64_t V2 = cast<ConstantInt>(C2)->getSExtValue(); 1051 switch (pred) { 1052 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1053 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1 < V2); 1054 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1 > V2); 1055 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1 <= V2); 1056 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1 >= V2); 1057 } 1058 } else { 1059 uint64_t V1 = cast<ConstantInt>(C1)->getZExtValue(); 1060 uint64_t V2 = cast<ConstantInt>(C2)->getZExtValue(); 1061 switch (pred) { 1062 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1063 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); 1064 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); 1065 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1 < V2); 1066 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1 > V2); 1067 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1 <= V2); 1068 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1 >= V2); 1069 } 1070 } 1071 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1072 double C1Val = cast<ConstantFP>(C1)->getValue(); 1073 double C2Val = cast<ConstantFP>(C2)->getValue(); 1074 switch (pred) { 1075 default: assert(0 && "Invalid FCmp Predicate"); return 0; 1076 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); 1077 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); 1078 case FCmpInst::FCMP_UNO: 1079 return ConstantInt::get(Type::Int1Ty, C1Val != C1Val || C2Val != C2Val); 1080 case FCmpInst::FCMP_ORD: 1081 return ConstantInt::get(Type::Int1Ty, C1Val == C1Val && C2Val == C2Val); 1082 case FCmpInst::FCMP_UEQ: 1083 if (C1Val != C1Val || C2Val != C2Val) 1084 return ConstantInt::getTrue(); 1085 /* FALL THROUGH */ 1086 case FCmpInst::FCMP_OEQ: 1087 return ConstantInt::get(Type::Int1Ty, C1Val == C2Val); 1088 case FCmpInst::FCMP_UNE: 1089 if (C1Val != C1Val || C2Val != C2Val) 1090 return ConstantInt::getTrue(); 1091 /* FALL THROUGH */ 1092 case FCmpInst::FCMP_ONE: 1093 return ConstantInt::get(Type::Int1Ty, C1Val != C2Val); 1094 case FCmpInst::FCMP_ULT: 1095 if (C1Val != C1Val || C2Val != C2Val) 1096 return ConstantInt::getTrue(); 1097 /* FALL THROUGH */ 1098 case FCmpInst::FCMP_OLT: 1099 return ConstantInt::get(Type::Int1Ty, C1Val < C2Val); 1100 case FCmpInst::FCMP_UGT: 1101 if (C1Val != C1Val || C2Val != C2Val) 1102 return ConstantInt::getTrue(); 1103 /* FALL THROUGH */ 1104 case FCmpInst::FCMP_OGT: 1105 return ConstantInt::get(Type::Int1Ty, C1Val > C2Val); 1106 case FCmpInst::FCMP_ULE: 1107 if (C1Val != C1Val || C2Val != C2Val) 1108 return ConstantInt::getTrue(); 1109 /* FALL THROUGH */ 1110 case FCmpInst::FCMP_OLE: 1111 return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val); 1112 case FCmpInst::FCMP_UGE: 1113 if (C1Val != C1Val || C2Val != C2Val) 1114 return ConstantInt::getTrue(); 1115 /* FALL THROUGH */ 1116 case FCmpInst::FCMP_OGE: 1117 return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val); 1118 } 1119 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) { 1120 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) { 1121 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) { 1122 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { 1123 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, 1124 const_cast<Constant*>(CP1->getOperand(i)), 1125 const_cast<Constant*>(CP2->getOperand(i))); 1126 if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) 1127 return CB; 1128 } 1129 // Otherwise, could not decide from any element pairs. 1130 return 0; 1131 } else if (pred == ICmpInst::ICMP_EQ) { 1132 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { 1133 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ, 1134 const_cast<Constant*>(CP1->getOperand(i)), 1135 const_cast<Constant*>(CP2->getOperand(i))); 1136 if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) 1137 return CB; 1138 } 1139 // Otherwise, could not decide from any element pairs. 1140 return 0; 1141 } 1142 } 1143 } 1144 1145 if (C1->getType()->isFloatingPoint()) { 1146 switch (evaluateFCmpRelation(C1, C2)) { 1147 default: assert(0 && "Unknown relation!"); 1148 case FCmpInst::FCMP_UNO: 1149 case FCmpInst::FCMP_ORD: 1150 case FCmpInst::FCMP_UEQ: 1151 case FCmpInst::FCMP_UNE: 1152 case FCmpInst::FCMP_ULT: 1153 case FCmpInst::FCMP_UGT: 1154 case FCmpInst::FCMP_ULE: 1155 case FCmpInst::FCMP_UGE: 1156 case FCmpInst::FCMP_TRUE: 1157 case FCmpInst::FCMP_FALSE: 1158 case FCmpInst::BAD_FCMP_PREDICATE: 1159 break; // Couldn't determine anything about these constants. 1160 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1161 return ConstantInt::get(Type::Int1Ty, 1162 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1163 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1164 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1165 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1166 return ConstantInt::get(Type::Int1Ty, 1167 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1168 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1169 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1170 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1171 return ConstantInt::get(Type::Int1Ty, 1172 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1173 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1174 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1175 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1176 // We can only partially decide this relation. 1177 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1178 return ConstantInt::getFalse(); 1179 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1180 return ConstantInt::getTrue(); 1181 break; 1182 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1183 // We can only partially decide this relation. 1184 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1185 return ConstantInt::getFalse(); 1186 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1187 return ConstantInt::getTrue(); 1188 break; 1189 case ICmpInst::ICMP_NE: // We know that C1 != C2 1190 // We can only partially decide this relation. 1191 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1192 return ConstantInt::getFalse(); 1193 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1194 return ConstantInt::getTrue(); 1195 break; 1196 } 1197 } else { 1198 // Evaluate the relation between the two constants, per the predicate. 1199 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1200 default: assert(0 && "Unknown relational!"); 1201 case ICmpInst::BAD_ICMP_PREDICATE: 1202 break; // Couldn't determine anything about these constants. 1203 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1204 // If we know the constants are equal, we can decide the result of this 1205 // computation precisely. 1206 return ConstantInt::get(Type::Int1Ty, 1207 pred == ICmpInst::ICMP_EQ || 1208 pred == ICmpInst::ICMP_ULE || 1209 pred == ICmpInst::ICMP_SLE || 1210 pred == ICmpInst::ICMP_UGE || 1211 pred == ICmpInst::ICMP_SGE); 1212 case ICmpInst::ICMP_ULT: 1213 // If we know that C1 < C2, we can decide the result of this computation 1214 // precisely. 1215 return ConstantInt::get(Type::Int1Ty, 1216 pred == ICmpInst::ICMP_ULT || 1217 pred == ICmpInst::ICMP_NE || 1218 pred == ICmpInst::ICMP_ULE); 1219 case ICmpInst::ICMP_SLT: 1220 // If we know that C1 < C2, we can decide the result of this computation 1221 // precisely. 1222 return ConstantInt::get(Type::Int1Ty, 1223 pred == ICmpInst::ICMP_SLT || 1224 pred == ICmpInst::ICMP_NE || 1225 pred == ICmpInst::ICMP_SLE); 1226 case ICmpInst::ICMP_UGT: 1227 // If we know that C1 > C2, we can decide the result of this computation 1228 // precisely. 1229 return ConstantInt::get(Type::Int1Ty, 1230 pred == ICmpInst::ICMP_UGT || 1231 pred == ICmpInst::ICMP_NE || 1232 pred == ICmpInst::ICMP_UGE); 1233 case ICmpInst::ICMP_SGT: 1234 // If we know that C1 > C2, we can decide the result of this computation 1235 // precisely. 1236 return ConstantInt::get(Type::Int1Ty, 1237 pred == ICmpInst::ICMP_SGT || 1238 pred == ICmpInst::ICMP_NE || 1239 pred == ICmpInst::ICMP_SGE); 1240 case ICmpInst::ICMP_ULE: 1241 // If we know that C1 <= C2, we can only partially decide this relation. 1242 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse(); 1243 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue(); 1244 break; 1245 case ICmpInst::ICMP_SLE: 1246 // If we know that C1 <= C2, we can only partially decide this relation. 1247 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse(); 1248 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue(); 1249 break; 1250 1251 case ICmpInst::ICMP_UGE: 1252 // If we know that C1 >= C2, we can only partially decide this relation. 1253 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse(); 1254 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue(); 1255 break; 1256 case ICmpInst::ICMP_SGE: 1257 // If we know that C1 >= C2, we can only partially decide this relation. 1258 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse(); 1259 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue(); 1260 break; 1261 1262 case ICmpInst::ICMP_NE: 1263 // If we know that C1 != C2, we can only partially decide this relation. 1264 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(); 1265 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(); 1266 break; 1267 } 1268 1269 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) { 1270 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1271 // other way if possible. 1272 switch (pred) { 1273 case ICmpInst::ICMP_EQ: 1274 case ICmpInst::ICMP_NE: 1275 // No change of predicate required. 1276 return ConstantFoldCompareInstruction(pred, C2, C1); 1277 1278 case ICmpInst::ICMP_ULT: 1279 case ICmpInst::ICMP_SLT: 1280 case ICmpInst::ICMP_UGT: 1281 case ICmpInst::ICMP_SGT: 1282 case ICmpInst::ICMP_ULE: 1283 case ICmpInst::ICMP_SLE: 1284 case ICmpInst::ICMP_UGE: 1285 case ICmpInst::ICMP_SGE: 1286 // Change the predicate as necessary to swap the operands. 1287 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1288 return ConstantFoldCompareInstruction(pred, C2, C1); 1289 1290 default: // These predicates cannot be flopped around. 1291 break; 1292 } 1293 } 1294 } 1295 return 0; 1296} 1297 1298Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 1299 Constant* const *Idxs, 1300 unsigned NumIdx) { 1301 if (NumIdx == 0 || 1302 (NumIdx == 1 && Idxs[0]->isNullValue())) 1303 return const_cast<Constant*>(C); 1304 1305 if (isa<UndefValue>(C)) { 1306 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), 1307 (Value**)Idxs, NumIdx, 1308 true); 1309 assert(Ty != 0 && "Invalid indices for GEP!"); 1310 return UndefValue::get(PointerType::get(Ty)); 1311 } 1312 1313 Constant *Idx0 = Idxs[0]; 1314 if (C->isNullValue()) { 1315 bool isNull = true; 1316 for (unsigned i = 0, e = NumIdx; i != e; ++i) 1317 if (!Idxs[i]->isNullValue()) { 1318 isNull = false; 1319 break; 1320 } 1321 if (isNull) { 1322 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), 1323 (Value**)Idxs, NumIdx, 1324 true); 1325 assert(Ty != 0 && "Invalid indices for GEP!"); 1326 return ConstantPointerNull::get(PointerType::get(Ty)); 1327 } 1328 } 1329 1330 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 1331 // Combine Indices - If the source pointer to this getelementptr instruction 1332 // is a getelementptr instruction, combine the indices of the two 1333 // getelementptr instructions into a single instruction. 1334 // 1335 if (CE->getOpcode() == Instruction::GetElementPtr) { 1336 const Type *LastTy = 0; 1337 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1338 I != E; ++I) 1339 LastTy = *I; 1340 1341 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 1342 SmallVector<Value*, 16> NewIndices; 1343 NewIndices.reserve(NumIdx + CE->getNumOperands()); 1344 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 1345 NewIndices.push_back(CE->getOperand(i)); 1346 1347 // Add the last index of the source with the first index of the new GEP. 1348 // Make sure to handle the case when they are actually different types. 1349 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 1350 // Otherwise it must be an array. 1351 if (!Idx0->isNullValue()) { 1352 const Type *IdxTy = Combined->getType(); 1353 if (IdxTy != Idx0->getType()) { 1354 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); 1355 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, 1356 Type::Int64Ty); 1357 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 1358 } else { 1359 Combined = 1360 ConstantExpr::get(Instruction::Add, Idx0, Combined); 1361 } 1362 } 1363 1364 NewIndices.push_back(Combined); 1365 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); 1366 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], 1367 NewIndices.size()); 1368 } 1369 } 1370 1371 // Implement folding of: 1372 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 1373 // long 0, long 0) 1374 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 1375 // 1376 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) 1377 if (const PointerType *SPT = 1378 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 1379 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 1380 if (const ArrayType *CAT = 1381 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 1382 if (CAT->getElementType() == SAT->getElementType()) 1383 return ConstantExpr::getGetElementPtr( 1384 (Constant*)CE->getOperand(0), Idxs, NumIdx); 1385 } 1386 return 0; 1387} 1388 1389