ConstantFold.cpp revision ac9dcb94dde5f166ee29372385c0e3b695227ab4
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/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 return 0; // MIN_INT / -1 -> overflow 579 return ConstantInt::get(C1->getType(), 580 CI1->getSExtValue() / CI2->getSExtValue()); 581 case Instruction::URem: 582 if (C2->isNullValue()) return 0; // X / 0 -> can't fold 583 return ConstantInt::get(C1->getType(), C1Val % C2Val); 584 case Instruction::SRem: 585 if (CI2->isNullValue()) return 0; // X % 0 -> can't fold 586 if (CI2->isAllOnesValue() && 587 (((CI1->getType()->getPrimitiveSizeInBits() == 64) && 588 (CI1->getSExtValue() == INT64_MIN)) || 589 (CI1->getSExtValue() == -CI1->getSExtValue()))) 590 return 0; // MIN_INT % -1 -> overflow 591 return ConstantInt::get(C1->getType(), 592 CI1->getSExtValue() % CI2->getSExtValue()); 593 case Instruction::And: 594 return ConstantInt::get(C1->getType(), C1Val & C2Val); 595 case Instruction::Or: 596 return ConstantInt::get(C1->getType(), C1Val | C2Val); 597 case Instruction::Xor: 598 return ConstantInt::get(C1->getType(), C1Val ^ C2Val); 599 case Instruction::Shl: 600 return ConstantInt::get(C1->getType(), C1Val << C2Val); 601 case Instruction::LShr: 602 return ConstantInt::get(C1->getType(), C1Val >> C2Val); 603 case Instruction::AShr: 604 return ConstantInt::get(C1->getType(), 605 CI1->getSExtValue() >> C2Val); 606 } 607 } 608 } else if (const ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 609 if (const ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 610 double C1Val = CFP1->getValue(); 611 double C2Val = CFP2->getValue(); 612 switch (Opcode) { 613 default: 614 break; 615 case Instruction::Add: 616 return ConstantFP::get(CFP1->getType(), C1Val + C2Val); 617 case Instruction::Sub: 618 return ConstantFP::get(CFP1->getType(), C1Val - C2Val); 619 case Instruction::Mul: 620 return ConstantFP::get(CFP1->getType(), C1Val * C2Val); 621 case Instruction::FDiv: 622 if (CFP2->isExactlyValue(0.0)) 623 return ConstantFP::get(CFP1->getType(), 624 std::numeric_limits<double>::infinity()); 625 if (CFP2->isExactlyValue(-0.0)) 626 return ConstantFP::get(CFP1->getType(), 627 -std::numeric_limits<double>::infinity()); 628 return ConstantFP::get(CFP1->getType(), C1Val / C2Val); 629 case Instruction::FRem: 630 if (CFP2->isNullValue()) 631 return 0; 632 return ConstantFP::get(CFP1->getType(), std::fmod(C1Val, C2Val)); 633 } 634 } 635 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) { 636 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) { 637 switch (Opcode) { 638 default: 639 break; 640 case Instruction::Add: 641 return EvalVectorOp(CP1, CP2, ConstantExpr::getAdd); 642 case Instruction::Sub: 643 return EvalVectorOp(CP1, CP2, ConstantExpr::getSub); 644 case Instruction::Mul: 645 return EvalVectorOp(CP1, CP2, ConstantExpr::getMul); 646 case Instruction::UDiv: 647 return EvalVectorOp(CP1, CP2, ConstantExpr::getUDiv); 648 case Instruction::SDiv: 649 return EvalVectorOp(CP1, CP2, ConstantExpr::getSDiv); 650 case Instruction::FDiv: 651 return EvalVectorOp(CP1, CP2, ConstantExpr::getFDiv); 652 case Instruction::URem: 653 return EvalVectorOp(CP1, CP2, ConstantExpr::getURem); 654 case Instruction::SRem: 655 return EvalVectorOp(CP1, CP2, ConstantExpr::getSRem); 656 case Instruction::FRem: 657 return EvalVectorOp(CP1, CP2, ConstantExpr::getFRem); 658 case Instruction::And: 659 return EvalVectorOp(CP1, CP2, ConstantExpr::getAnd); 660 case Instruction::Or: 661 return EvalVectorOp(CP1, CP2, ConstantExpr::getOr); 662 case Instruction::Xor: 663 return EvalVectorOp(CP1, CP2, ConstantExpr::getXor); 664 } 665 } 666 } 667 668 // We don't know how to fold this 669 return 0; 670} 671 672/// isZeroSizedType - This type is zero sized if its an array or structure of 673/// zero sized types. The only leaf zero sized type is an empty structure. 674static bool isMaybeZeroSizedType(const Type *Ty) { 675 if (isa<OpaqueType>(Ty)) return true; // Can't say. 676 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 677 678 // If all of elements have zero size, this does too. 679 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 680 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 681 return true; 682 683 } else if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 684 return isMaybeZeroSizedType(ATy->getElementType()); 685 } 686 return false; 687} 688 689/// IdxCompare - Compare the two constants as though they were getelementptr 690/// indices. This allows coersion of the types to be the same thing. 691/// 692/// If the two constants are the "same" (after coersion), return 0. If the 693/// first is less than the second, return -1, if the second is less than the 694/// first, return 1. If the constants are not integral, return -2. 695/// 696static int IdxCompare(Constant *C1, Constant *C2, const Type *ElTy) { 697 if (C1 == C2) return 0; 698 699 // Ok, we found a different index. If they are not ConstantInt, we can't do 700 // anything with them. 701 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 702 return -2; // don't know! 703 704 // Ok, we have two differing integer indices. Sign extend them to be the same 705 // type. Long is always big enough, so we use it. 706 if (C1->getType() != Type::Int64Ty) 707 C1 = ConstantExpr::getSExt(C1, Type::Int64Ty); 708 709 if (C2->getType() != Type::Int64Ty) 710 C2 = ConstantExpr::getSExt(C2, Type::Int64Ty); 711 712 if (C1 == C2) return 0; // They are equal 713 714 // If the type being indexed over is really just a zero sized type, there is 715 // no pointer difference being made here. 716 if (isMaybeZeroSizedType(ElTy)) 717 return -2; // dunno. 718 719 // If they are really different, now that they are the same type, then we 720 // found a difference! 721 if (cast<ConstantInt>(C1)->getSExtValue() < 722 cast<ConstantInt>(C2)->getSExtValue()) 723 return -1; 724 else 725 return 1; 726} 727 728/// evaluateFCmpRelation - This function determines if there is anything we can 729/// decide about the two constants provided. This doesn't need to handle simple 730/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 731/// If we can determine that the two constants have a particular relation to 732/// each other, we should return the corresponding FCmpInst predicate, 733/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 734/// ConstantFoldCompareInstruction. 735/// 736/// To simplify this code we canonicalize the relation so that the first 737/// operand is always the most "complex" of the two. We consider ConstantFP 738/// to be the simplest, and ConstantExprs to be the most complex. 739static FCmpInst::Predicate evaluateFCmpRelation(const Constant *V1, 740 const Constant *V2) { 741 assert(V1->getType() == V2->getType() && 742 "Cannot compare values of different types!"); 743 // Handle degenerate case quickly 744 if (V1 == V2) return FCmpInst::FCMP_OEQ; 745 746 if (!isa<ConstantExpr>(V1)) { 747 if (!isa<ConstantExpr>(V2)) { 748 // We distilled thisUse the standard constant folder for a few cases 749 ConstantInt *R = 0; 750 Constant *C1 = const_cast<Constant*>(V1); 751 Constant *C2 = const_cast<Constant*>(V2); 752 R = dyn_cast<ConstantInt>( 753 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, C1, C2)); 754 if (R && R->getZExtValue()) 755 return FCmpInst::FCMP_OEQ; 756 R = dyn_cast<ConstantInt>( 757 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, C1, C2)); 758 if (R && R->getZExtValue()) 759 return FCmpInst::FCMP_OLT; 760 R = dyn_cast<ConstantInt>( 761 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, C1, C2)); 762 if (R && R->getZExtValue()) 763 return FCmpInst::FCMP_OGT; 764 765 // Nothing more we can do 766 return FCmpInst::BAD_FCMP_PREDICATE; 767 } 768 769 // If the first operand is simple and second is ConstantExpr, swap operands. 770 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 771 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 772 return FCmpInst::getSwappedPredicate(SwappedRelation); 773 } else { 774 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 775 // constantexpr or a simple constant. 776 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 777 switch (CE1->getOpcode()) { 778 case Instruction::FPTrunc: 779 case Instruction::FPExt: 780 case Instruction::UIToFP: 781 case Instruction::SIToFP: 782 // We might be able to do something with these but we don't right now. 783 break; 784 default: 785 break; 786 } 787 } 788 // There are MANY other foldings that we could perform here. They will 789 // probably be added on demand, as they seem needed. 790 return FCmpInst::BAD_FCMP_PREDICATE; 791} 792 793/// evaluateICmpRelation - This function determines if there is anything we can 794/// decide about the two constants provided. This doesn't need to handle simple 795/// things like integer comparisons, but should instead handle ConstantExprs 796/// and GlobalValues. If we can determine that the two constants have a 797/// particular relation to each other, we should return the corresponding ICmp 798/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 799/// 800/// To simplify this code we canonicalize the relation so that the first 801/// operand is always the most "complex" of the two. We consider simple 802/// constants (like ConstantInt) to be the simplest, followed by 803/// GlobalValues, followed by ConstantExpr's (the most complex). 804/// 805static ICmpInst::Predicate evaluateICmpRelation(const Constant *V1, 806 const Constant *V2, 807 bool isSigned) { 808 assert(V1->getType() == V2->getType() && 809 "Cannot compare different types of values!"); 810 if (V1 == V2) return ICmpInst::ICMP_EQ; 811 812 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1)) { 813 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2)) { 814 // We distilled this down to a simple case, use the standard constant 815 // folder. 816 ConstantInt *R = 0; 817 Constant *C1 = const_cast<Constant*>(V1); 818 Constant *C2 = const_cast<Constant*>(V2); 819 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 820 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 821 if (R && R->getZExtValue()) 822 return pred; 823 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 824 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 825 if (R && R->getZExtValue()) 826 return pred; 827 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 828 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, C1, C2)); 829 if (R && R->getZExtValue()) 830 return pred; 831 832 // If we couldn't figure it out, bail. 833 return ICmpInst::BAD_ICMP_PREDICATE; 834 } 835 836 // If the first operand is simple, swap operands. 837 ICmpInst::Predicate SwappedRelation = 838 evaluateICmpRelation(V2, V1, isSigned); 839 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 840 return ICmpInst::getSwappedPredicate(SwappedRelation); 841 842 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(V1)) { 843 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 844 ICmpInst::Predicate SwappedRelation = 845 evaluateICmpRelation(V2, V1, isSigned); 846 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 847 return ICmpInst::getSwappedPredicate(SwappedRelation); 848 else 849 return ICmpInst::BAD_ICMP_PREDICATE; 850 } 851 852 // Now we know that the RHS is a GlobalValue or simple constant, 853 // which (since the types must match) means that it's a ConstantPointerNull. 854 if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 855 if (!CPR1->hasExternalWeakLinkage() || !CPR2->hasExternalWeakLinkage()) 856 return ICmpInst::ICMP_NE; 857 } else { 858 // GlobalVals can never be null. 859 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 860 if (!CPR1->hasExternalWeakLinkage()) 861 return ICmpInst::ICMP_NE; 862 } 863 } else { 864 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 865 // constantexpr, a CPR, or a simple constant. 866 const ConstantExpr *CE1 = cast<ConstantExpr>(V1); 867 const Constant *CE1Op0 = CE1->getOperand(0); 868 869 switch (CE1->getOpcode()) { 870 case Instruction::Trunc: 871 case Instruction::FPTrunc: 872 case Instruction::FPExt: 873 case Instruction::FPToUI: 874 case Instruction::FPToSI: 875 break; // We can't evaluate floating point casts or truncations. 876 877 case Instruction::UIToFP: 878 case Instruction::SIToFP: 879 case Instruction::IntToPtr: 880 case Instruction::BitCast: 881 case Instruction::ZExt: 882 case Instruction::SExt: 883 case Instruction::PtrToInt: 884 // If the cast is not actually changing bits, and the second operand is a 885 // null pointer, do the comparison with the pre-casted value. 886 if (V2->isNullValue() && 887 (isa<PointerType>(CE1->getType()) || CE1->getType()->isInteger())) { 888 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false : 889 (CE1->getOpcode() == Instruction::SExt ? true : 890 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned)); 891 return evaluateICmpRelation( 892 CE1Op0, Constant::getNullValue(CE1Op0->getType()), sgnd); 893 } 894 895 // If the dest type is a pointer type, and the RHS is a constantexpr cast 896 // from the same type as the src of the LHS, evaluate the inputs. This is 897 // important for things like "icmp eq (cast 4 to int*), (cast 5 to int*)", 898 // which happens a lot in compilers with tagged integers. 899 if (const ConstantExpr *CE2 = dyn_cast<ConstantExpr>(V2)) 900 if (CE2->isCast() && isa<PointerType>(CE1->getType()) && 901 CE1->getOperand(0)->getType() == CE2->getOperand(0)->getType() && 902 CE1->getOperand(0)->getType()->isInteger()) { 903 bool sgnd = CE1->getOpcode() == Instruction::ZExt ? false : 904 (CE1->getOpcode() == Instruction::SExt ? true : 905 (CE1->getOpcode() == Instruction::PtrToInt ? false : isSigned)); 906 return evaluateICmpRelation(CE1->getOperand(0), CE2->getOperand(0), 907 sgnd); 908 } 909 break; 910 911 case Instruction::GetElementPtr: 912 // Ok, since this is a getelementptr, we know that the constant has a 913 // pointer type. Check the various cases. 914 if (isa<ConstantPointerNull>(V2)) { 915 // If we are comparing a GEP to a null pointer, check to see if the base 916 // of the GEP equals the null pointer. 917 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 918 if (GV->hasExternalWeakLinkage()) 919 // Weak linkage GVals could be zero or not. We're comparing that 920 // to null pointer so its greater-or-equal 921 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 922 else 923 // If its not weak linkage, the GVal must have a non-zero address 924 // so the result is greater-than 925 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 926 } else if (isa<ConstantPointerNull>(CE1Op0)) { 927 // If we are indexing from a null pointer, check to see if we have any 928 // non-zero indices. 929 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 930 if (!CE1->getOperand(i)->isNullValue()) 931 // Offsetting from null, must not be equal. 932 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 933 // Only zero indexes from null, must still be zero. 934 return ICmpInst::ICMP_EQ; 935 } 936 // Otherwise, we can't really say if the first operand is null or not. 937 } else if (const GlobalValue *CPR2 = dyn_cast<GlobalValue>(V2)) { 938 if (isa<ConstantPointerNull>(CE1Op0)) { 939 if (CPR2->hasExternalWeakLinkage()) 940 // Weak linkage GVals could be zero or not. We're comparing it to 941 // a null pointer, so its less-or-equal 942 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 943 else 944 // If its not weak linkage, the GVal must have a non-zero address 945 // so the result is less-than 946 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 947 } else if (const GlobalValue *CPR1 = dyn_cast<GlobalValue>(CE1Op0)) { 948 if (CPR1 == CPR2) { 949 // If this is a getelementptr of the same global, then it must be 950 // different. Because the types must match, the getelementptr could 951 // only have at most one index, and because we fold getelementptr's 952 // with a single zero index, it must be nonzero. 953 assert(CE1->getNumOperands() == 2 && 954 !CE1->getOperand(1)->isNullValue() && 955 "Suprising getelementptr!"); 956 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 957 } else { 958 // If they are different globals, we don't know what the value is, 959 // but they can't be equal. 960 return ICmpInst::ICMP_NE; 961 } 962 } 963 } else { 964 const ConstantExpr *CE2 = cast<ConstantExpr>(V2); 965 const Constant *CE2Op0 = CE2->getOperand(0); 966 967 // There are MANY other foldings that we could perform here. They will 968 // probably be added on demand, as they seem needed. 969 switch (CE2->getOpcode()) { 970 default: break; 971 case Instruction::GetElementPtr: 972 // By far the most common case to handle is when the base pointers are 973 // obviously to the same or different globals. 974 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 975 if (CE1Op0 != CE2Op0) // Don't know relative ordering, but not equal 976 return ICmpInst::ICMP_NE; 977 // Ok, we know that both getelementptr instructions are based on the 978 // same global. From this, we can precisely determine the relative 979 // ordering of the resultant pointers. 980 unsigned i = 1; 981 982 // Compare all of the operands the GEP's have in common. 983 gep_type_iterator GTI = gep_type_begin(CE1); 984 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 985 ++i, ++GTI) 986 switch (IdxCompare(CE1->getOperand(i), CE2->getOperand(i), 987 GTI.getIndexedType())) { 988 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 989 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 990 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 991 } 992 993 // Ok, we ran out of things they have in common. If any leftovers 994 // are non-zero then we have a difference, otherwise we are equal. 995 for (; i < CE1->getNumOperands(); ++i) 996 if (!CE1->getOperand(i)->isNullValue()) 997 if (isa<ConstantInt>(CE1->getOperand(i))) 998 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 999 else 1000 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1001 1002 for (; i < CE2->getNumOperands(); ++i) 1003 if (!CE2->getOperand(i)->isNullValue()) 1004 if (isa<ConstantInt>(CE2->getOperand(i))) 1005 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1006 else 1007 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1008 return ICmpInst::ICMP_EQ; 1009 } 1010 } 1011 } 1012 default: 1013 break; 1014 } 1015 } 1016 1017 return ICmpInst::BAD_ICMP_PREDICATE; 1018} 1019 1020Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1021 const Constant *C1, 1022 const Constant *C2) { 1023 1024 // Handle some degenerate cases first 1025 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) 1026 return UndefValue::get(Type::Int1Ty); 1027 1028 // icmp eq/ne(null,GV) -> false/true 1029 if (C1->isNullValue()) { 1030 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1031 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null 1032 if (pred == ICmpInst::ICMP_EQ) 1033 return ConstantInt::getFalse(); 1034 else if (pred == ICmpInst::ICMP_NE) 1035 return ConstantInt::getTrue(); 1036 // icmp eq/ne(GV,null) -> false/true 1037 } else if (C2->isNullValue()) { 1038 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1039 if (!GV->hasExternalWeakLinkage()) // External weak GV can be null 1040 if (pred == ICmpInst::ICMP_EQ) 1041 return ConstantInt::getFalse(); 1042 else if (pred == ICmpInst::ICMP_NE) 1043 return ConstantInt::getTrue(); 1044 } 1045 1046 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1047 if (ICmpInst::isSignedPredicate(ICmpInst::Predicate(pred))) { 1048 int64_t V1 = cast<ConstantInt>(C1)->getSExtValue(); 1049 int64_t V2 = cast<ConstantInt>(C2)->getSExtValue(); 1050 switch (pred) { 1051 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1052 case ICmpInst::ICMP_SLT:return ConstantInt::get(Type::Int1Ty, V1 < V2); 1053 case ICmpInst::ICMP_SGT:return ConstantInt::get(Type::Int1Ty, V1 > V2); 1054 case ICmpInst::ICMP_SLE:return ConstantInt::get(Type::Int1Ty, V1 <= V2); 1055 case ICmpInst::ICMP_SGE:return ConstantInt::get(Type::Int1Ty, V1 >= V2); 1056 } 1057 } else { 1058 uint64_t V1 = cast<ConstantInt>(C1)->getZExtValue(); 1059 uint64_t V2 = cast<ConstantInt>(C2)->getZExtValue(); 1060 switch (pred) { 1061 default: assert(0 && "Invalid ICmp Predicate"); return 0; 1062 case ICmpInst::ICMP_EQ: return ConstantInt::get(Type::Int1Ty, V1 == V2); 1063 case ICmpInst::ICMP_NE: return ConstantInt::get(Type::Int1Ty, V1 != V2); 1064 case ICmpInst::ICMP_ULT:return ConstantInt::get(Type::Int1Ty, V1 < V2); 1065 case ICmpInst::ICMP_UGT:return ConstantInt::get(Type::Int1Ty, V1 > V2); 1066 case ICmpInst::ICMP_ULE:return ConstantInt::get(Type::Int1Ty, V1 <= V2); 1067 case ICmpInst::ICMP_UGE:return ConstantInt::get(Type::Int1Ty, V1 >= V2); 1068 } 1069 } 1070 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1071 double C1Val = cast<ConstantFP>(C1)->getValue(); 1072 double C2Val = cast<ConstantFP>(C2)->getValue(); 1073 switch (pred) { 1074 default: assert(0 && "Invalid FCmp Predicate"); return 0; 1075 case FCmpInst::FCMP_FALSE: return ConstantInt::getFalse(); 1076 case FCmpInst::FCMP_TRUE: return ConstantInt::getTrue(); 1077 case FCmpInst::FCMP_UNO: 1078 return ConstantInt::get(Type::Int1Ty, C1Val != C1Val || C2Val != C2Val); 1079 case FCmpInst::FCMP_ORD: 1080 return ConstantInt::get(Type::Int1Ty, C1Val == C1Val && C2Val == C2Val); 1081 case FCmpInst::FCMP_UEQ: 1082 if (C1Val != C1Val || C2Val != C2Val) 1083 return ConstantInt::getTrue(); 1084 /* FALL THROUGH */ 1085 case FCmpInst::FCMP_OEQ: 1086 return ConstantInt::get(Type::Int1Ty, C1Val == C2Val); 1087 case FCmpInst::FCMP_UNE: 1088 if (C1Val != C1Val || C2Val != C2Val) 1089 return ConstantInt::getTrue(); 1090 /* FALL THROUGH */ 1091 case FCmpInst::FCMP_ONE: 1092 return ConstantInt::get(Type::Int1Ty, C1Val != C2Val); 1093 case FCmpInst::FCMP_ULT: 1094 if (C1Val != C1Val || C2Val != C2Val) 1095 return ConstantInt::getTrue(); 1096 /* FALL THROUGH */ 1097 case FCmpInst::FCMP_OLT: 1098 return ConstantInt::get(Type::Int1Ty, C1Val < C2Val); 1099 case FCmpInst::FCMP_UGT: 1100 if (C1Val != C1Val || C2Val != C2Val) 1101 return ConstantInt::getTrue(); 1102 /* FALL THROUGH */ 1103 case FCmpInst::FCMP_OGT: 1104 return ConstantInt::get(Type::Int1Ty, C1Val > C2Val); 1105 case FCmpInst::FCMP_ULE: 1106 if (C1Val != C1Val || C2Val != C2Val) 1107 return ConstantInt::getTrue(); 1108 /* FALL THROUGH */ 1109 case FCmpInst::FCMP_OLE: 1110 return ConstantInt::get(Type::Int1Ty, C1Val <= C2Val); 1111 case FCmpInst::FCMP_UGE: 1112 if (C1Val != C1Val || C2Val != C2Val) 1113 return ConstantInt::getTrue(); 1114 /* FALL THROUGH */ 1115 case FCmpInst::FCMP_OGE: 1116 return ConstantInt::get(Type::Int1Ty, C1Val >= C2Val); 1117 } 1118 } else if (const ConstantVector *CP1 = dyn_cast<ConstantVector>(C1)) { 1119 if (const ConstantVector *CP2 = dyn_cast<ConstantVector>(C2)) { 1120 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) { 1121 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { 1122 Constant *C= ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, 1123 const_cast<Constant*>(CP1->getOperand(i)), 1124 const_cast<Constant*>(CP2->getOperand(i))); 1125 if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) 1126 return CB; 1127 } 1128 // Otherwise, could not decide from any element pairs. 1129 return 0; 1130 } else if (pred == ICmpInst::ICMP_EQ) { 1131 for (unsigned i = 0, e = CP1->getNumOperands(); i != e; ++i) { 1132 Constant *C = ConstantExpr::getICmp(ICmpInst::ICMP_EQ, 1133 const_cast<Constant*>(CP1->getOperand(i)), 1134 const_cast<Constant*>(CP2->getOperand(i))); 1135 if (ConstantInt *CB = dyn_cast<ConstantInt>(C)) 1136 return CB; 1137 } 1138 // Otherwise, could not decide from any element pairs. 1139 return 0; 1140 } 1141 } 1142 } 1143 1144 if (C1->getType()->isFloatingPoint()) { 1145 switch (evaluateFCmpRelation(C1, C2)) { 1146 default: assert(0 && "Unknown relation!"); 1147 case FCmpInst::FCMP_UNO: 1148 case FCmpInst::FCMP_ORD: 1149 case FCmpInst::FCMP_UEQ: 1150 case FCmpInst::FCMP_UNE: 1151 case FCmpInst::FCMP_ULT: 1152 case FCmpInst::FCMP_UGT: 1153 case FCmpInst::FCMP_ULE: 1154 case FCmpInst::FCMP_UGE: 1155 case FCmpInst::FCMP_TRUE: 1156 case FCmpInst::FCMP_FALSE: 1157 case FCmpInst::BAD_FCMP_PREDICATE: 1158 break; // Couldn't determine anything about these constants. 1159 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1160 return ConstantInt::get(Type::Int1Ty, 1161 pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1162 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1163 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1164 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1165 return ConstantInt::get(Type::Int1Ty, 1166 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1167 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1168 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1169 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1170 return ConstantInt::get(Type::Int1Ty, 1171 pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1172 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1173 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1174 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1175 // We can only partially decide this relation. 1176 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1177 return ConstantInt::getFalse(); 1178 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1179 return ConstantInt::getTrue(); 1180 break; 1181 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1182 // We can only partially decide this relation. 1183 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1184 return ConstantInt::getFalse(); 1185 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1186 return ConstantInt::getTrue(); 1187 break; 1188 case ICmpInst::ICMP_NE: // We know that C1 != C2 1189 // We can only partially decide this relation. 1190 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1191 return ConstantInt::getFalse(); 1192 if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1193 return ConstantInt::getTrue(); 1194 break; 1195 } 1196 } else { 1197 // Evaluate the relation between the two constants, per the predicate. 1198 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1199 default: assert(0 && "Unknown relational!"); 1200 case ICmpInst::BAD_ICMP_PREDICATE: 1201 break; // Couldn't determine anything about these constants. 1202 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1203 // If we know the constants are equal, we can decide the result of this 1204 // computation precisely. 1205 return ConstantInt::get(Type::Int1Ty, 1206 pred == ICmpInst::ICMP_EQ || 1207 pred == ICmpInst::ICMP_ULE || 1208 pred == ICmpInst::ICMP_SLE || 1209 pred == ICmpInst::ICMP_UGE || 1210 pred == ICmpInst::ICMP_SGE); 1211 case ICmpInst::ICMP_ULT: 1212 // If we know that C1 < C2, we can decide the result of this computation 1213 // precisely. 1214 return ConstantInt::get(Type::Int1Ty, 1215 pred == ICmpInst::ICMP_ULT || 1216 pred == ICmpInst::ICMP_NE || 1217 pred == ICmpInst::ICMP_ULE); 1218 case ICmpInst::ICMP_SLT: 1219 // If we know that C1 < C2, we can decide the result of this computation 1220 // precisely. 1221 return ConstantInt::get(Type::Int1Ty, 1222 pred == ICmpInst::ICMP_SLT || 1223 pred == ICmpInst::ICMP_NE || 1224 pred == ICmpInst::ICMP_SLE); 1225 case ICmpInst::ICMP_UGT: 1226 // If we know that C1 > C2, we can decide the result of this computation 1227 // precisely. 1228 return ConstantInt::get(Type::Int1Ty, 1229 pred == ICmpInst::ICMP_UGT || 1230 pred == ICmpInst::ICMP_NE || 1231 pred == ICmpInst::ICMP_UGE); 1232 case ICmpInst::ICMP_SGT: 1233 // If we know that C1 > C2, we can decide the result of this computation 1234 // precisely. 1235 return ConstantInt::get(Type::Int1Ty, 1236 pred == ICmpInst::ICMP_SGT || 1237 pred == ICmpInst::ICMP_NE || 1238 pred == ICmpInst::ICMP_SGE); 1239 case ICmpInst::ICMP_ULE: 1240 // If we know that C1 <= C2, we can only partially decide this relation. 1241 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getFalse(); 1242 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getTrue(); 1243 break; 1244 case ICmpInst::ICMP_SLE: 1245 // If we know that C1 <= C2, we can only partially decide this relation. 1246 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getFalse(); 1247 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getTrue(); 1248 break; 1249 1250 case ICmpInst::ICMP_UGE: 1251 // If we know that C1 >= C2, we can only partially decide this relation. 1252 if (pred == ICmpInst::ICMP_ULT) return ConstantInt::getFalse(); 1253 if (pred == ICmpInst::ICMP_UGT) return ConstantInt::getTrue(); 1254 break; 1255 case ICmpInst::ICMP_SGE: 1256 // If we know that C1 >= C2, we can only partially decide this relation. 1257 if (pred == ICmpInst::ICMP_SLT) return ConstantInt::getFalse(); 1258 if (pred == ICmpInst::ICMP_SGT) return ConstantInt::getTrue(); 1259 break; 1260 1261 case ICmpInst::ICMP_NE: 1262 // If we know that C1 != C2, we can only partially decide this relation. 1263 if (pred == ICmpInst::ICMP_EQ) return ConstantInt::getFalse(); 1264 if (pred == ICmpInst::ICMP_NE) return ConstantInt::getTrue(); 1265 break; 1266 } 1267 1268 if (!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) { 1269 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1270 // other way if possible. 1271 switch (pred) { 1272 case ICmpInst::ICMP_EQ: 1273 case ICmpInst::ICMP_NE: 1274 // No change of predicate required. 1275 return ConstantFoldCompareInstruction(pred, C2, C1); 1276 1277 case ICmpInst::ICMP_ULT: 1278 case ICmpInst::ICMP_SLT: 1279 case ICmpInst::ICMP_UGT: 1280 case ICmpInst::ICMP_SGT: 1281 case ICmpInst::ICMP_ULE: 1282 case ICmpInst::ICMP_SLE: 1283 case ICmpInst::ICMP_UGE: 1284 case ICmpInst::ICMP_SGE: 1285 // Change the predicate as necessary to swap the operands. 1286 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1287 return ConstantFoldCompareInstruction(pred, C2, C1); 1288 1289 default: // These predicates cannot be flopped around. 1290 break; 1291 } 1292 } 1293 } 1294 return 0; 1295} 1296 1297Constant *llvm::ConstantFoldGetElementPtr(const Constant *C, 1298 Constant* const *Idxs, 1299 unsigned NumIdx) { 1300 if (NumIdx == 0 || 1301 (NumIdx == 1 && Idxs[0]->isNullValue())) 1302 return const_cast<Constant*>(C); 1303 1304 if (isa<UndefValue>(C)) { 1305 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), 1306 (Value**)Idxs, NumIdx, 1307 true); 1308 assert(Ty != 0 && "Invalid indices for GEP!"); 1309 return UndefValue::get(PointerType::get(Ty)); 1310 } 1311 1312 Constant *Idx0 = Idxs[0]; 1313 if (C->isNullValue()) { 1314 bool isNull = true; 1315 for (unsigned i = 0, e = NumIdx; i != e; ++i) 1316 if (!Idxs[i]->isNullValue()) { 1317 isNull = false; 1318 break; 1319 } 1320 if (isNull) { 1321 const Type *Ty = GetElementPtrInst::getIndexedType(C->getType(), 1322 (Value**)Idxs, NumIdx, 1323 true); 1324 assert(Ty != 0 && "Invalid indices for GEP!"); 1325 return ConstantPointerNull::get(PointerType::get(Ty)); 1326 } 1327 } 1328 1329 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(const_cast<Constant*>(C))) { 1330 // Combine Indices - If the source pointer to this getelementptr instruction 1331 // is a getelementptr instruction, combine the indices of the two 1332 // getelementptr instructions into a single instruction. 1333 // 1334 if (CE->getOpcode() == Instruction::GetElementPtr) { 1335 const Type *LastTy = 0; 1336 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1337 I != E; ++I) 1338 LastTy = *I; 1339 1340 if ((LastTy && isa<ArrayType>(LastTy)) || Idx0->isNullValue()) { 1341 SmallVector<Value*, 16> NewIndices; 1342 NewIndices.reserve(NumIdx + CE->getNumOperands()); 1343 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 1344 NewIndices.push_back(CE->getOperand(i)); 1345 1346 // Add the last index of the source with the first index of the new GEP. 1347 // Make sure to handle the case when they are actually different types. 1348 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 1349 // Otherwise it must be an array. 1350 if (!Idx0->isNullValue()) { 1351 const Type *IdxTy = Combined->getType(); 1352 if (IdxTy != Idx0->getType()) { 1353 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Type::Int64Ty); 1354 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, 1355 Type::Int64Ty); 1356 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 1357 } else { 1358 Combined = 1359 ConstantExpr::get(Instruction::Add, Idx0, Combined); 1360 } 1361 } 1362 1363 NewIndices.push_back(Combined); 1364 NewIndices.insert(NewIndices.end(), Idxs+1, Idxs+NumIdx); 1365 return ConstantExpr::getGetElementPtr(CE->getOperand(0), &NewIndices[0], 1366 NewIndices.size()); 1367 } 1368 } 1369 1370 // Implement folding of: 1371 // int* getelementptr ([2 x int]* cast ([3 x int]* %X to [2 x int]*), 1372 // long 0, long 0) 1373 // To: int* getelementptr ([3 x int]* %X, long 0, long 0) 1374 // 1375 if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) 1376 if (const PointerType *SPT = 1377 dyn_cast<PointerType>(CE->getOperand(0)->getType())) 1378 if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType())) 1379 if (const ArrayType *CAT = 1380 dyn_cast<ArrayType>(cast<PointerType>(C->getType())->getElementType())) 1381 if (CAT->getElementType() == SAT->getElementType()) 1382 return ConstantExpr::getGetElementPtr( 1383 (Constant*)CE->getOperand(0), Idxs, NumIdx); 1384 } 1385 return 0; 1386} 1387 1388