InstCombineCasts.cpp revision 75831904220042260c4faece8507a2807acba47f
1//===- InstCombineCasts.cpp -----------------------------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file implements the visit functions for cast operations. 11// 12//===----------------------------------------------------------------------===// 13 14#include "InstCombine.h" 15#include "llvm/Target/TargetData.h" 16#include "llvm/Support/PatternMatch.h" 17using namespace llvm; 18using namespace PatternMatch; 19 20/// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear 21/// expression. If so, decompose it, returning some value X, such that Val is 22/// X*Scale+Offset. 23/// 24static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale, 25 uint64_t &Offset) { 26 if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) { 27 Offset = CI->getZExtValue(); 28 Scale = 0; 29 return ConstantInt::get(Val->getType(), 0); 30 } 31 32 if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) { 33 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) { 34 if (I->getOpcode() == Instruction::Shl) { 35 // This is a value scaled by '1 << the shift amt'. 36 Scale = UINT64_C(1) << RHS->getZExtValue(); 37 Offset = 0; 38 return I->getOperand(0); 39 } 40 41 if (I->getOpcode() == Instruction::Mul) { 42 // This value is scaled by 'RHS'. 43 Scale = RHS->getZExtValue(); 44 Offset = 0; 45 return I->getOperand(0); 46 } 47 48 if (I->getOpcode() == Instruction::Add) { 49 // We have X+C. Check to see if we really have (X*C2)+C1, 50 // where C1 is divisible by C2. 51 unsigned SubScale; 52 Value *SubVal = 53 DecomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset); 54 Offset += RHS->getZExtValue(); 55 Scale = SubScale; 56 return SubVal; 57 } 58 } 59 } 60 61 // Otherwise, we can't look past this. 62 Scale = 1; 63 Offset = 0; 64 return Val; 65} 66 67/// PromoteCastOfAllocation - If we find a cast of an allocation instruction, 68/// try to eliminate the cast by moving the type information into the alloc. 69Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI, 70 AllocaInst &AI) { 71 // This requires TargetData to get the alloca alignment and size information. 72 if (!TD) return 0; 73 74 const PointerType *PTy = cast<PointerType>(CI.getType()); 75 76 BuilderTy AllocaBuilder(*Builder); 77 AllocaBuilder.SetInsertPoint(AI.getParent(), &AI); 78 79 // Get the type really allocated and the type casted to. 80 const Type *AllocElTy = AI.getAllocatedType(); 81 const Type *CastElTy = PTy->getElementType(); 82 if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0; 83 84 unsigned AllocElTyAlign = TD->getABITypeAlignment(AllocElTy); 85 unsigned CastElTyAlign = TD->getABITypeAlignment(CastElTy); 86 if (CastElTyAlign < AllocElTyAlign) return 0; 87 88 // If the allocation has multiple uses, only promote it if we are strictly 89 // increasing the alignment of the resultant allocation. If we keep it the 90 // same, we open the door to infinite loops of various kinds. (A reference 91 // from a dbg.declare doesn't count as a use for this purpose.) 92 if (!AI.hasOneUse() && !hasOneUsePlusDeclare(&AI) && 93 CastElTyAlign == AllocElTyAlign) return 0; 94 95 uint64_t AllocElTySize = TD->getTypeAllocSize(AllocElTy); 96 uint64_t CastElTySize = TD->getTypeAllocSize(CastElTy); 97 if (CastElTySize == 0 || AllocElTySize == 0) return 0; 98 99 // See if we can satisfy the modulus by pulling a scale out of the array 100 // size argument. 101 unsigned ArraySizeScale; 102 uint64_t ArrayOffset; 103 Value *NumElements = // See if the array size is a decomposable linear expr. 104 DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset); 105 106 // If we can now satisfy the modulus, by using a non-1 scale, we really can 107 // do the xform. 108 if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 || 109 (AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0; 110 111 unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize; 112 Value *Amt = 0; 113 if (Scale == 1) { 114 Amt = NumElements; 115 } else { 116 Amt = ConstantInt::get(AI.getArraySize()->getType(), Scale); 117 // Insert before the alloca, not before the cast. 118 Amt = AllocaBuilder.CreateMul(Amt, NumElements, "tmp"); 119 } 120 121 if (uint64_t Offset = (AllocElTySize*ArrayOffset)/CastElTySize) { 122 Value *Off = ConstantInt::get(AI.getArraySize()->getType(), 123 Offset, true); 124 Amt = AllocaBuilder.CreateAdd(Amt, Off, "tmp"); 125 } 126 127 AllocaInst *New = AllocaBuilder.CreateAlloca(CastElTy, Amt); 128 New->setAlignment(AI.getAlignment()); 129 New->takeName(&AI); 130 131 // If the allocation has one real use plus a dbg.declare, just remove the 132 // declare. 133 if (DbgDeclareInst *DI = hasOneUsePlusDeclare(&AI)) { 134 EraseInstFromFunction(*(Instruction*)DI); 135 } 136 // If the allocation has multiple real uses, insert a cast and change all 137 // things that used it to use the new cast. This will also hack on CI, but it 138 // will die soon. 139 else if (!AI.hasOneUse()) { 140 // New is the allocation instruction, pointer typed. AI is the original 141 // allocation instruction, also pointer typed. Thus, cast to use is BitCast. 142 Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast"); 143 AI.replaceAllUsesWith(NewCast); 144 } 145 return ReplaceInstUsesWith(CI, New); 146} 147 148 149 150/// EvaluateInDifferentType - Given an expression that 151/// CanEvaluateTruncated or CanEvaluateSExtd returns true for, actually 152/// insert the code to evaluate the expression. 153Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type *Ty, 154 bool isSigned) { 155 if (Constant *C = dyn_cast<Constant>(V)) { 156 C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/); 157 // If we got a constantexpr back, try to simplify it with TD info. 158 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 159 C = ConstantFoldConstantExpression(CE, TD); 160 return C; 161 } 162 163 // Otherwise, it must be an instruction. 164 Instruction *I = cast<Instruction>(V); 165 Instruction *Res = 0; 166 unsigned Opc = I->getOpcode(); 167 switch (Opc) { 168 case Instruction::Add: 169 case Instruction::Sub: 170 case Instruction::Mul: 171 case Instruction::And: 172 case Instruction::Or: 173 case Instruction::Xor: 174 case Instruction::AShr: 175 case Instruction::LShr: 176 case Instruction::Shl: 177 case Instruction::UDiv: 178 case Instruction::URem: { 179 Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned); 180 Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned); 181 Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS); 182 break; 183 } 184 case Instruction::Trunc: 185 case Instruction::ZExt: 186 case Instruction::SExt: 187 // If the source type of the cast is the type we're trying for then we can 188 // just return the source. There's no need to insert it because it is not 189 // new. 190 if (I->getOperand(0)->getType() == Ty) 191 return I->getOperand(0); 192 193 // Otherwise, must be the same type of cast, so just reinsert a new one. 194 // This also handles the case of zext(trunc(x)) -> zext(x). 195 Res = CastInst::CreateIntegerCast(I->getOperand(0), Ty, 196 Opc == Instruction::SExt); 197 break; 198 case Instruction::Select: { 199 Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned); 200 Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned); 201 Res = SelectInst::Create(I->getOperand(0), True, False); 202 break; 203 } 204 case Instruction::PHI: { 205 PHINode *OPN = cast<PHINode>(I); 206 PHINode *NPN = PHINode::Create(Ty); 207 for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) { 208 Value *V =EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned); 209 NPN->addIncoming(V, OPN->getIncomingBlock(i)); 210 } 211 Res = NPN; 212 break; 213 } 214 default: 215 // TODO: Can handle more cases here. 216 llvm_unreachable("Unreachable!"); 217 break; 218 } 219 220 Res->takeName(I); 221 return InsertNewInstBefore(Res, *I); 222} 223 224 225/// This function is a wrapper around CastInst::isEliminableCastPair. It 226/// simply extracts arguments and returns what that function returns. 227static Instruction::CastOps 228isEliminableCastPair( 229 const CastInst *CI, ///< The first cast instruction 230 unsigned opcode, ///< The opcode of the second cast instruction 231 const Type *DstTy, ///< The target type for the second cast instruction 232 TargetData *TD ///< The target data for pointer size 233) { 234 235 const Type *SrcTy = CI->getOperand(0)->getType(); // A from above 236 const Type *MidTy = CI->getType(); // B from above 237 238 // Get the opcodes of the two Cast instructions 239 Instruction::CastOps firstOp = Instruction::CastOps(CI->getOpcode()); 240 Instruction::CastOps secondOp = Instruction::CastOps(opcode); 241 242 unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, 243 DstTy, 244 TD ? TD->getIntPtrType(CI->getContext()) : 0); 245 246 // We don't want to form an inttoptr or ptrtoint that converts to an integer 247 // type that differs from the pointer size. 248 if ((Res == Instruction::IntToPtr && 249 (!TD || SrcTy != TD->getIntPtrType(CI->getContext()))) || 250 (Res == Instruction::PtrToInt && 251 (!TD || DstTy != TD->getIntPtrType(CI->getContext())))) 252 Res = 0; 253 254 return Instruction::CastOps(Res); 255} 256 257/// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually 258/// results in any code being generated and is interesting to optimize out. If 259/// the cast can be eliminated by some other simple transformation, we prefer 260/// to do the simplification first. 261bool InstCombiner::ShouldOptimizeCast(Instruction::CastOps opc, const Value *V, 262 const Type *Ty) { 263 // Noop casts and casts of constants should be eliminated trivially. 264 if (V->getType() == Ty || isa<Constant>(V)) return false; 265 266 // If this is another cast that can be eliminated, we prefer to have it 267 // eliminated. 268 if (const CastInst *CI = dyn_cast<CastInst>(V)) 269 if (isEliminableCastPair(CI, opc, Ty, TD)) 270 return false; 271 272 // If this is a vector sext from a compare, then we don't want to break the 273 // idiom where each element of the extended vector is either zero or all ones. 274 if (opc == Instruction::SExt && isa<CmpInst>(V) && Ty->isVectorTy()) 275 return false; 276 277 return true; 278} 279 280 281/// @brief Implement the transforms common to all CastInst visitors. 282Instruction *InstCombiner::commonCastTransforms(CastInst &CI) { 283 Value *Src = CI.getOperand(0); 284 285 // Many cases of "cast of a cast" are eliminable. If it's eliminable we just 286 // eliminate it now. 287 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast 288 if (Instruction::CastOps opc = 289 isEliminableCastPair(CSrc, CI.getOpcode(), CI.getType(), TD)) { 290 // The first cast (CSrc) is eliminable so we need to fix up or replace 291 // the second cast (CI). CSrc will then have a good chance of being dead. 292 return CastInst::Create(opc, CSrc->getOperand(0), CI.getType()); 293 } 294 } 295 296 // If we are casting a select then fold the cast into the select 297 if (SelectInst *SI = dyn_cast<SelectInst>(Src)) 298 if (Instruction *NV = FoldOpIntoSelect(CI, SI)) 299 return NV; 300 301 // If we are casting a PHI then fold the cast into the PHI 302 if (isa<PHINode>(Src)) { 303 // We don't do this if this would create a PHI node with an illegal type if 304 // it is currently legal. 305 if (!Src->getType()->isIntegerTy() || 306 !CI.getType()->isIntegerTy() || 307 ShouldChangeType(CI.getType(), Src->getType())) 308 if (Instruction *NV = FoldOpIntoPhi(CI)) 309 return NV; 310 } 311 312 return 0; 313} 314 315/// CanEvaluateTruncated - Return true if we can evaluate the specified 316/// expression tree as type Ty instead of its larger type, and arrive with the 317/// same value. This is used by code that tries to eliminate truncates. 318/// 319/// Ty will always be a type smaller than V. We should return true if trunc(V) 320/// can be computed by computing V in the smaller type. If V is an instruction, 321/// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only 322/// makes sense if x and y can be efficiently truncated. 323/// 324/// This function works on both vectors and scalars. 325/// 326static bool CanEvaluateTruncated(Value *V, const Type *Ty) { 327 // We can always evaluate constants in another type. 328 if (isa<Constant>(V)) 329 return true; 330 331 Instruction *I = dyn_cast<Instruction>(V); 332 if (!I) return false; 333 334 const Type *OrigTy = V->getType(); 335 336 // If this is an extension from the dest type, we can eliminate it, even if it 337 // has multiple uses. 338 if ((isa<ZExtInst>(I) || isa<SExtInst>(I)) && 339 I->getOperand(0)->getType() == Ty) 340 return true; 341 342 // We can't extend or shrink something that has multiple uses: doing so would 343 // require duplicating the instruction in general, which isn't profitable. 344 if (!I->hasOneUse()) return false; 345 346 unsigned Opc = I->getOpcode(); 347 switch (Opc) { 348 case Instruction::Add: 349 case Instruction::Sub: 350 case Instruction::Mul: 351 case Instruction::And: 352 case Instruction::Or: 353 case Instruction::Xor: 354 // These operators can all arbitrarily be extended or truncated. 355 return CanEvaluateTruncated(I->getOperand(0), Ty) && 356 CanEvaluateTruncated(I->getOperand(1), Ty); 357 358 case Instruction::UDiv: 359 case Instruction::URem: { 360 // UDiv and URem can be truncated if all the truncated bits are zero. 361 uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits(); 362 uint32_t BitWidth = Ty->getScalarSizeInBits(); 363 if (BitWidth < OrigBitWidth) { 364 APInt Mask = APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth); 365 if (MaskedValueIsZero(I->getOperand(0), Mask) && 366 MaskedValueIsZero(I->getOperand(1), Mask)) { 367 return CanEvaluateTruncated(I->getOperand(0), Ty) && 368 CanEvaluateTruncated(I->getOperand(1), Ty); 369 } 370 } 371 break; 372 } 373 case Instruction::Shl: 374 // If we are truncating the result of this SHL, and if it's a shift of a 375 // constant amount, we can always perform a SHL in a smaller type. 376 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) { 377 uint32_t BitWidth = Ty->getScalarSizeInBits(); 378 if (CI->getLimitedValue(BitWidth) < BitWidth) 379 return CanEvaluateTruncated(I->getOperand(0), Ty); 380 } 381 break; 382 case Instruction::LShr: 383 // If this is a truncate of a logical shr, we can truncate it to a smaller 384 // lshr iff we know that the bits we would otherwise be shifting in are 385 // already zeros. 386 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) { 387 uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits(); 388 uint32_t BitWidth = Ty->getScalarSizeInBits(); 389 if (MaskedValueIsZero(I->getOperand(0), 390 APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth)) && 391 CI->getLimitedValue(BitWidth) < BitWidth) { 392 return CanEvaluateTruncated(I->getOperand(0), Ty); 393 } 394 } 395 break; 396 case Instruction::Trunc: 397 // trunc(trunc(x)) -> trunc(x) 398 return true; 399 case Instruction::ZExt: 400 case Instruction::SExt: 401 // trunc(ext(x)) -> ext(x) if the source type is smaller than the new dest 402 // trunc(ext(x)) -> trunc(x) if the source type is larger than the new dest 403 return true; 404 case Instruction::Select: { 405 SelectInst *SI = cast<SelectInst>(I); 406 return CanEvaluateTruncated(SI->getTrueValue(), Ty) && 407 CanEvaluateTruncated(SI->getFalseValue(), Ty); 408 } 409 case Instruction::PHI: { 410 // We can change a phi if we can change all operands. Note that we never 411 // get into trouble with cyclic PHIs here because we only consider 412 // instructions with a single use. 413 PHINode *PN = cast<PHINode>(I); 414 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 415 if (!CanEvaluateTruncated(PN->getIncomingValue(i), Ty)) 416 return false; 417 return true; 418 } 419 default: 420 // TODO: Can handle more cases here. 421 break; 422 } 423 424 return false; 425} 426 427Instruction *InstCombiner::visitTrunc(TruncInst &CI) { 428 if (Instruction *Result = commonCastTransforms(CI)) 429 return Result; 430 431 // See if we can simplify any instructions used by the input whose sole 432 // purpose is to compute bits we don't care about. 433 if (SimplifyDemandedInstructionBits(CI)) 434 return &CI; 435 436 Value *Src = CI.getOperand(0); 437 const Type *DestTy = CI.getType(), *SrcTy = Src->getType(); 438 439 // Attempt to truncate the entire input expression tree to the destination 440 // type. Only do this if the dest type is a simple type, don't convert the 441 // expression tree to something weird like i93 unless the source is also 442 // strange. 443 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && 444 CanEvaluateTruncated(Src, DestTy)) { 445 446 // If this cast is a truncate, evaluting in a different type always 447 // eliminates the cast, so it is always a win. 448 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" 449 " to avoid cast: " << CI << '\n'); 450 Value *Res = EvaluateInDifferentType(Src, DestTy, false); 451 assert(Res->getType() == DestTy); 452 return ReplaceInstUsesWith(CI, Res); 453 } 454 455 // Canonicalize trunc x to i1 -> (icmp ne (and x, 1), 0), likewise for vector. 456 if (DestTy->getScalarSizeInBits() == 1) { 457 Constant *One = ConstantInt::get(Src->getType(), 1); 458 Src = Builder->CreateAnd(Src, One, "tmp"); 459 Value *Zero = Constant::getNullValue(Src->getType()); 460 return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero); 461 } 462 463 // Transform trunc(lshr (zext A), Cst) to eliminate one type conversion. 464 Value *A = 0; ConstantInt *Cst = 0; 465 if (Src->hasOneUse() && 466 match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) { 467 // We have three types to worry about here, the type of A, the source of 468 // the truncate (MidSize), and the destination of the truncate. We know that 469 // ASize < MidSize and MidSize > ResultSize, but don't know the relation 470 // between ASize and ResultSize. 471 unsigned ASize = A->getType()->getPrimitiveSizeInBits(); 472 473 // If the shift amount is larger than the size of A, then the result is 474 // known to be zero because all the input bits got shifted out. 475 if (Cst->getZExtValue() >= ASize) 476 return ReplaceInstUsesWith(CI, Constant::getNullValue(CI.getType())); 477 478 // Since we're doing an lshr and a zero extend, and know that the shift 479 // amount is smaller than ASize, it is always safe to do the shift in A's 480 // type, then zero extend or truncate to the result. 481 Value *Shift = Builder->CreateLShr(A, Cst->getZExtValue()); 482 Shift->takeName(Src); 483 return CastInst::CreateIntegerCast(Shift, CI.getType(), false); 484 } 485 486 // Transform "trunc (and X, cst)" -> "and (trunc X), cst" so long as the dest 487 // type isn't non-native. 488 if (Src->hasOneUse() && isa<IntegerType>(Src->getType()) && 489 ShouldChangeType(Src->getType(), CI.getType()) && 490 match(Src, m_And(m_Value(A), m_ConstantInt(Cst)))) { 491 Value *NewTrunc = Builder->CreateTrunc(A, CI.getType(), A->getName()+".tr"); 492 return BinaryOperator::CreateAnd(NewTrunc, 493 ConstantExpr::getTrunc(Cst, CI.getType())); 494 } 495 496 return 0; 497} 498 499/// transformZExtICmp - Transform (zext icmp) to bitwise / integer operations 500/// in order to eliminate the icmp. 501Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI, 502 bool DoXform) { 503 // If we are just checking for a icmp eq of a single bit and zext'ing it 504 // to an integer, then shift the bit to the appropriate place and then 505 // cast to integer to avoid the comparison. 506 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) { 507 const APInt &Op1CV = Op1C->getValue(); 508 509 // zext (x <s 0) to i32 --> x>>u31 true if signbit set. 510 // zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear. 511 if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) || 512 (ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())) { 513 if (!DoXform) return ICI; 514 515 Value *In = ICI->getOperand(0); 516 Value *Sh = ConstantInt::get(In->getType(), 517 In->getType()->getScalarSizeInBits()-1); 518 In = Builder->CreateLShr(In, Sh, In->getName()+".lobit"); 519 if (In->getType() != CI.getType()) 520 In = Builder->CreateIntCast(In, CI.getType(), false/*ZExt*/, "tmp"); 521 522 if (ICI->getPredicate() == ICmpInst::ICMP_SGT) { 523 Constant *One = ConstantInt::get(In->getType(), 1); 524 In = Builder->CreateXor(In, One, In->getName()+".not"); 525 } 526 527 return ReplaceInstUsesWith(CI, In); 528 } 529 530 531 532 // zext (X == 0) to i32 --> X^1 iff X has only the low bit set. 533 // zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set. 534 // zext (X == 1) to i32 --> X iff X has only the low bit set. 535 // zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set. 536 // zext (X != 0) to i32 --> X iff X has only the low bit set. 537 // zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set. 538 // zext (X != 1) to i32 --> X^1 iff X has only the low bit set. 539 // zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set. 540 if ((Op1CV == 0 || Op1CV.isPowerOf2()) && 541 // This only works for EQ and NE 542 ICI->isEquality()) { 543 // If Op1C some other power of two, convert: 544 uint32_t BitWidth = Op1C->getType()->getBitWidth(); 545 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); 546 APInt TypeMask(APInt::getAllOnesValue(BitWidth)); 547 ComputeMaskedBits(ICI->getOperand(0), TypeMask, KnownZero, KnownOne); 548 549 APInt KnownZeroMask(~KnownZero); 550 if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1? 551 if (!DoXform) return ICI; 552 553 bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE; 554 if (Op1CV != 0 && (Op1CV != KnownZeroMask)) { 555 // (X&4) == 2 --> false 556 // (X&4) != 2 --> true 557 Constant *Res = ConstantInt::get(Type::getInt1Ty(CI.getContext()), 558 isNE); 559 Res = ConstantExpr::getZExt(Res, CI.getType()); 560 return ReplaceInstUsesWith(CI, Res); 561 } 562 563 uint32_t ShiftAmt = KnownZeroMask.logBase2(); 564 Value *In = ICI->getOperand(0); 565 if (ShiftAmt) { 566 // Perform a logical shr by shiftamt. 567 // Insert the shift to put the result in the low bit. 568 In = Builder->CreateLShr(In, ConstantInt::get(In->getType(),ShiftAmt), 569 In->getName()+".lobit"); 570 } 571 572 if ((Op1CV != 0) == isNE) { // Toggle the low bit. 573 Constant *One = ConstantInt::get(In->getType(), 1); 574 In = Builder->CreateXor(In, One, "tmp"); 575 } 576 577 if (CI.getType() == In->getType()) 578 return ReplaceInstUsesWith(CI, In); 579 return CastInst::CreateIntegerCast(In, CI.getType(), false/*ZExt*/); 580 } 581 } 582 } 583 584 // icmp ne A, B is equal to xor A, B when A and B only really have one bit. 585 // It is also profitable to transform icmp eq into not(xor(A, B)) because that 586 // may lead to additional simplifications. 587 if (ICI->isEquality() && CI.getType() == ICI->getOperand(0)->getType()) { 588 if (const IntegerType *ITy = dyn_cast<IntegerType>(CI.getType())) { 589 uint32_t BitWidth = ITy->getBitWidth(); 590 Value *LHS = ICI->getOperand(0); 591 Value *RHS = ICI->getOperand(1); 592 593 APInt KnownZeroLHS(BitWidth, 0), KnownOneLHS(BitWidth, 0); 594 APInt KnownZeroRHS(BitWidth, 0), KnownOneRHS(BitWidth, 0); 595 APInt TypeMask(APInt::getAllOnesValue(BitWidth)); 596 ComputeMaskedBits(LHS, TypeMask, KnownZeroLHS, KnownOneLHS); 597 ComputeMaskedBits(RHS, TypeMask, KnownZeroRHS, KnownOneRHS); 598 599 if (KnownZeroLHS == KnownZeroRHS && KnownOneLHS == KnownOneRHS) { 600 APInt KnownBits = KnownZeroLHS | KnownOneLHS; 601 APInt UnknownBit = ~KnownBits; 602 if (UnknownBit.countPopulation() == 1) { 603 if (!DoXform) return ICI; 604 605 Value *Result = Builder->CreateXor(LHS, RHS); 606 607 // Mask off any bits that are set and won't be shifted away. 608 if (KnownOneLHS.uge(UnknownBit)) 609 Result = Builder->CreateAnd(Result, 610 ConstantInt::get(ITy, UnknownBit)); 611 612 // Shift the bit we're testing down to the lsb. 613 Result = Builder->CreateLShr( 614 Result, ConstantInt::get(ITy, UnknownBit.countTrailingZeros())); 615 616 if (ICI->getPredicate() == ICmpInst::ICMP_EQ) 617 Result = Builder->CreateXor(Result, ConstantInt::get(ITy, 1)); 618 Result->takeName(ICI); 619 return ReplaceInstUsesWith(CI, Result); 620 } 621 } 622 } 623 } 624 625 return 0; 626} 627 628/// CanEvaluateZExtd - Determine if the specified value can be computed in the 629/// specified wider type and produce the same low bits. If not, return false. 630/// 631/// If this function returns true, it can also return a non-zero number of bits 632/// (in BitsToClear) which indicates that the value it computes is correct for 633/// the zero extend, but that the additional BitsToClear bits need to be zero'd 634/// out. For example, to promote something like: 635/// 636/// %B = trunc i64 %A to i32 637/// %C = lshr i32 %B, 8 638/// %E = zext i32 %C to i64 639/// 640/// CanEvaluateZExtd for the 'lshr' will return true, and BitsToClear will be 641/// set to 8 to indicate that the promoted value needs to have bits 24-31 642/// cleared in addition to bits 32-63. Since an 'and' will be generated to 643/// clear the top bits anyway, doing this has no extra cost. 644/// 645/// This function works on both vectors and scalars. 646static bool CanEvaluateZExtd(Value *V, const Type *Ty, unsigned &BitsToClear) { 647 BitsToClear = 0; 648 if (isa<Constant>(V)) 649 return true; 650 651 Instruction *I = dyn_cast<Instruction>(V); 652 if (!I) return false; 653 654 // If the input is a truncate from the destination type, we can trivially 655 // eliminate it, even if it has multiple uses. 656 // FIXME: This is currently disabled until codegen can handle this without 657 // pessimizing code, PR5997. 658 if (0 && isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty) 659 return true; 660 661 // We can't extend or shrink something that has multiple uses: doing so would 662 // require duplicating the instruction in general, which isn't profitable. 663 if (!I->hasOneUse()) return false; 664 665 unsigned Opc = I->getOpcode(), Tmp; 666 switch (Opc) { 667 case Instruction::ZExt: // zext(zext(x)) -> zext(x). 668 case Instruction::SExt: // zext(sext(x)) -> sext(x). 669 case Instruction::Trunc: // zext(trunc(x)) -> trunc(x) or zext(x) 670 return true; 671 case Instruction::And: 672 case Instruction::Or: 673 case Instruction::Xor: 674 case Instruction::Add: 675 case Instruction::Sub: 676 case Instruction::Mul: 677 case Instruction::Shl: 678 if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear) || 679 !CanEvaluateZExtd(I->getOperand(1), Ty, Tmp)) 680 return false; 681 // These can all be promoted if neither operand has 'bits to clear'. 682 if (BitsToClear == 0 && Tmp == 0) 683 return true; 684 685 // If the operation is an AND/OR/XOR and the bits to clear are zero in the 686 // other side, BitsToClear is ok. 687 if (Tmp == 0 && 688 (Opc == Instruction::And || Opc == Instruction::Or || 689 Opc == Instruction::Xor)) { 690 // We use MaskedValueIsZero here for generality, but the case we care 691 // about the most is constant RHS. 692 unsigned VSize = V->getType()->getScalarSizeInBits(); 693 if (MaskedValueIsZero(I->getOperand(1), 694 APInt::getHighBitsSet(VSize, BitsToClear))) 695 return true; 696 } 697 698 // Otherwise, we don't know how to analyze this BitsToClear case yet. 699 return false; 700 701 case Instruction::LShr: 702 // We can promote lshr(x, cst) if we can promote x. This requires the 703 // ultimate 'and' to clear out the high zero bits we're clearing out though. 704 if (ConstantInt *Amt = dyn_cast<ConstantInt>(I->getOperand(1))) { 705 if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear)) 706 return false; 707 BitsToClear += Amt->getZExtValue(); 708 if (BitsToClear > V->getType()->getScalarSizeInBits()) 709 BitsToClear = V->getType()->getScalarSizeInBits(); 710 return true; 711 } 712 // Cannot promote variable LSHR. 713 return false; 714 case Instruction::Select: 715 if (!CanEvaluateZExtd(I->getOperand(1), Ty, Tmp) || 716 !CanEvaluateZExtd(I->getOperand(2), Ty, BitsToClear) || 717 // TODO: If important, we could handle the case when the BitsToClear are 718 // known zero in the disagreeing side. 719 Tmp != BitsToClear) 720 return false; 721 return true; 722 723 case Instruction::PHI: { 724 // We can change a phi if we can change all operands. Note that we never 725 // get into trouble with cyclic PHIs here because we only consider 726 // instructions with a single use. 727 PHINode *PN = cast<PHINode>(I); 728 if (!CanEvaluateZExtd(PN->getIncomingValue(0), Ty, BitsToClear)) 729 return false; 730 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) 731 if (!CanEvaluateZExtd(PN->getIncomingValue(i), Ty, Tmp) || 732 // TODO: If important, we could handle the case when the BitsToClear 733 // are known zero in the disagreeing input. 734 Tmp != BitsToClear) 735 return false; 736 return true; 737 } 738 default: 739 // TODO: Can handle more cases here. 740 return false; 741 } 742} 743 744Instruction *InstCombiner::visitZExt(ZExtInst &CI) { 745 // If this zero extend is only used by a truncate, let the truncate by 746 // eliminated before we try to optimize this zext. 747 if (CI.hasOneUse() && isa<TruncInst>(CI.use_back())) 748 return 0; 749 750 // If one of the common conversion will work, do it. 751 if (Instruction *Result = commonCastTransforms(CI)) 752 return Result; 753 754 // See if we can simplify any instructions used by the input whose sole 755 // purpose is to compute bits we don't care about. 756 if (SimplifyDemandedInstructionBits(CI)) 757 return &CI; 758 759 Value *Src = CI.getOperand(0); 760 const Type *SrcTy = Src->getType(), *DestTy = CI.getType(); 761 762 // Attempt to extend the entire input expression tree to the destination 763 // type. Only do this if the dest type is a simple type, don't convert the 764 // expression tree to something weird like i93 unless the source is also 765 // strange. 766 unsigned BitsToClear; 767 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && 768 CanEvaluateZExtd(Src, DestTy, BitsToClear)) { 769 assert(BitsToClear < SrcTy->getScalarSizeInBits() && 770 "Unreasonable BitsToClear"); 771 772 // Okay, we can transform this! Insert the new expression now. 773 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" 774 " to avoid zero extend: " << CI); 775 Value *Res = EvaluateInDifferentType(Src, DestTy, false); 776 assert(Res->getType() == DestTy); 777 778 uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits()-BitsToClear; 779 uint32_t DestBitSize = DestTy->getScalarSizeInBits(); 780 781 // If the high bits are already filled with zeros, just replace this 782 // cast with the result. 783 if (MaskedValueIsZero(Res, APInt::getHighBitsSet(DestBitSize, 784 DestBitSize-SrcBitsKept))) 785 return ReplaceInstUsesWith(CI, Res); 786 787 // We need to emit an AND to clear the high bits. 788 Constant *C = ConstantInt::get(Res->getType(), 789 APInt::getLowBitsSet(DestBitSize, SrcBitsKept)); 790 return BinaryOperator::CreateAnd(Res, C); 791 } 792 793 // If this is a TRUNC followed by a ZEXT then we are dealing with integral 794 // types and if the sizes are just right we can convert this into a logical 795 // 'and' which will be much cheaper than the pair of casts. 796 if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast 797 // TODO: Subsume this into EvaluateInDifferentType. 798 799 // Get the sizes of the types involved. We know that the intermediate type 800 // will be smaller than A or C, but don't know the relation between A and C. 801 Value *A = CSrc->getOperand(0); 802 unsigned SrcSize = A->getType()->getScalarSizeInBits(); 803 unsigned MidSize = CSrc->getType()->getScalarSizeInBits(); 804 unsigned DstSize = CI.getType()->getScalarSizeInBits(); 805 // If we're actually extending zero bits, then if 806 // SrcSize < DstSize: zext(a & mask) 807 // SrcSize == DstSize: a & mask 808 // SrcSize > DstSize: trunc(a) & mask 809 if (SrcSize < DstSize) { 810 APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize)); 811 Constant *AndConst = ConstantInt::get(A->getType(), AndValue); 812 Value *And = Builder->CreateAnd(A, AndConst, CSrc->getName()+".mask"); 813 return new ZExtInst(And, CI.getType()); 814 } 815 816 if (SrcSize == DstSize) { 817 APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize)); 818 return BinaryOperator::CreateAnd(A, ConstantInt::get(A->getType(), 819 AndValue)); 820 } 821 if (SrcSize > DstSize) { 822 Value *Trunc = Builder->CreateTrunc(A, CI.getType(), "tmp"); 823 APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize)); 824 return BinaryOperator::CreateAnd(Trunc, 825 ConstantInt::get(Trunc->getType(), 826 AndValue)); 827 } 828 } 829 830 if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) 831 return transformZExtICmp(ICI, CI); 832 833 BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src); 834 if (SrcI && SrcI->getOpcode() == Instruction::Or) { 835 // zext (or icmp, icmp) --> or (zext icmp), (zext icmp) if at least one 836 // of the (zext icmp) will be transformed. 837 ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0)); 838 ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1)); 839 if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() && 840 (transformZExtICmp(LHS, CI, false) || 841 transformZExtICmp(RHS, CI, false))) { 842 Value *LCast = Builder->CreateZExt(LHS, CI.getType(), LHS->getName()); 843 Value *RCast = Builder->CreateZExt(RHS, CI.getType(), RHS->getName()); 844 return BinaryOperator::Create(Instruction::Or, LCast, RCast); 845 } 846 } 847 848 // zext(trunc(t) & C) -> (t & zext(C)). 849 if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse()) 850 if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1))) 851 if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) { 852 Value *TI0 = TI->getOperand(0); 853 if (TI0->getType() == CI.getType()) 854 return 855 BinaryOperator::CreateAnd(TI0, 856 ConstantExpr::getZExt(C, CI.getType())); 857 } 858 859 // zext((trunc(t) & C) ^ C) -> ((t & zext(C)) ^ zext(C)). 860 if (SrcI && SrcI->getOpcode() == Instruction::Xor && SrcI->hasOneUse()) 861 if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1))) 862 if (BinaryOperator *And = dyn_cast<BinaryOperator>(SrcI->getOperand(0))) 863 if (And->getOpcode() == Instruction::And && And->hasOneUse() && 864 And->getOperand(1) == C) 865 if (TruncInst *TI = dyn_cast<TruncInst>(And->getOperand(0))) { 866 Value *TI0 = TI->getOperand(0); 867 if (TI0->getType() == CI.getType()) { 868 Constant *ZC = ConstantExpr::getZExt(C, CI.getType()); 869 Value *NewAnd = Builder->CreateAnd(TI0, ZC, "tmp"); 870 return BinaryOperator::CreateXor(NewAnd, ZC); 871 } 872 } 873 874 // zext (xor i1 X, true) to i32 --> xor (zext i1 X to i32), 1 875 Value *X; 876 if (SrcI && SrcI->hasOneUse() && SrcI->getType()->isIntegerTy(1) && 877 match(SrcI, m_Not(m_Value(X))) && 878 (!X->hasOneUse() || !isa<CmpInst>(X))) { 879 Value *New = Builder->CreateZExt(X, CI.getType()); 880 return BinaryOperator::CreateXor(New, ConstantInt::get(CI.getType(), 1)); 881 } 882 883 return 0; 884} 885 886/// CanEvaluateSExtd - Return true if we can take the specified value 887/// and return it as type Ty without inserting any new casts and without 888/// changing the value of the common low bits. This is used by code that tries 889/// to promote integer operations to a wider types will allow us to eliminate 890/// the extension. 891/// 892/// This function works on both vectors and scalars. 893/// 894static bool CanEvaluateSExtd(Value *V, const Type *Ty) { 895 assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() && 896 "Can't sign extend type to a smaller type"); 897 // If this is a constant, it can be trivially promoted. 898 if (isa<Constant>(V)) 899 return true; 900 901 Instruction *I = dyn_cast<Instruction>(V); 902 if (!I) return false; 903 904 // If this is a truncate from the dest type, we can trivially eliminate it, 905 // even if it has multiple uses. 906 // FIXME: This is currently disabled until codegen can handle this without 907 // pessimizing code, PR5997. 908 if (0 && isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty) 909 return true; 910 911 // We can't extend or shrink something that has multiple uses: doing so would 912 // require duplicating the instruction in general, which isn't profitable. 913 if (!I->hasOneUse()) return false; 914 915 switch (I->getOpcode()) { 916 case Instruction::SExt: // sext(sext(x)) -> sext(x) 917 case Instruction::ZExt: // sext(zext(x)) -> zext(x) 918 case Instruction::Trunc: // sext(trunc(x)) -> trunc(x) or sext(x) 919 return true; 920 case Instruction::And: 921 case Instruction::Or: 922 case Instruction::Xor: 923 case Instruction::Add: 924 case Instruction::Sub: 925 case Instruction::Mul: 926 // These operators can all arbitrarily be extended if their inputs can. 927 return CanEvaluateSExtd(I->getOperand(0), Ty) && 928 CanEvaluateSExtd(I->getOperand(1), Ty); 929 930 //case Instruction::Shl: TODO 931 //case Instruction::LShr: TODO 932 933 case Instruction::Select: 934 return CanEvaluateSExtd(I->getOperand(1), Ty) && 935 CanEvaluateSExtd(I->getOperand(2), Ty); 936 937 case Instruction::PHI: { 938 // We can change a phi if we can change all operands. Note that we never 939 // get into trouble with cyclic PHIs here because we only consider 940 // instructions with a single use. 941 PHINode *PN = cast<PHINode>(I); 942 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 943 if (!CanEvaluateSExtd(PN->getIncomingValue(i), Ty)) return false; 944 return true; 945 } 946 default: 947 // TODO: Can handle more cases here. 948 break; 949 } 950 951 return false; 952} 953 954Instruction *InstCombiner::visitSExt(SExtInst &CI) { 955 // If this sign extend is only used by a truncate, let the truncate by 956 // eliminated before we try to optimize this zext. 957 if (CI.hasOneUse() && isa<TruncInst>(CI.use_back())) 958 return 0; 959 960 if (Instruction *I = commonCastTransforms(CI)) 961 return I; 962 963 // See if we can simplify any instructions used by the input whose sole 964 // purpose is to compute bits we don't care about. 965 if (SimplifyDemandedInstructionBits(CI)) 966 return &CI; 967 968 Value *Src = CI.getOperand(0); 969 const Type *SrcTy = Src->getType(), *DestTy = CI.getType(); 970 971 // Attempt to extend the entire input expression tree to the destination 972 // type. Only do this if the dest type is a simple type, don't convert the 973 // expression tree to something weird like i93 unless the source is also 974 // strange. 975 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && 976 CanEvaluateSExtd(Src, DestTy)) { 977 // Okay, we can transform this! Insert the new expression now. 978 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" 979 " to avoid sign extend: " << CI); 980 Value *Res = EvaluateInDifferentType(Src, DestTy, true); 981 assert(Res->getType() == DestTy); 982 983 uint32_t SrcBitSize = SrcTy->getScalarSizeInBits(); 984 uint32_t DestBitSize = DestTy->getScalarSizeInBits(); 985 986 // If the high bits are already filled with sign bit, just replace this 987 // cast with the result. 988 if (ComputeNumSignBits(Res) > DestBitSize - SrcBitSize) 989 return ReplaceInstUsesWith(CI, Res); 990 991 // We need to emit a shl + ashr to do the sign extend. 992 Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize); 993 return BinaryOperator::CreateAShr(Builder->CreateShl(Res, ShAmt, "sext"), 994 ShAmt); 995 } 996 997 // If this input is a trunc from our destination, then turn sext(trunc(x)) 998 // into shifts. 999 if (TruncInst *TI = dyn_cast<TruncInst>(Src)) 1000 if (TI->hasOneUse() && TI->getOperand(0)->getType() == DestTy) { 1001 uint32_t SrcBitSize = SrcTy->getScalarSizeInBits(); 1002 uint32_t DestBitSize = DestTy->getScalarSizeInBits(); 1003 1004 // We need to emit a shl + ashr to do the sign extend. 1005 Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize); 1006 Value *Res = Builder->CreateShl(TI->getOperand(0), ShAmt, "sext"); 1007 return BinaryOperator::CreateAShr(Res, ShAmt); 1008 } 1009 1010 1011 // (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if signed 1012 // (x >s -1) ? -1 : 0 -> ashr x, 31 -> all ones if not signed 1013 { 1014 ICmpInst::Predicate Pred; Value *CmpLHS; ConstantInt *CmpRHS; 1015 if (match(Src, m_ICmp(Pred, m_Value(CmpLHS), m_ConstantInt(CmpRHS)))) { 1016 // sext (x <s 0) to i32 --> x>>s31 true if signbit set. 1017 // sext (x >s -1) to i32 --> (x>>s31)^-1 true if signbit clear. 1018 if ((Pred == ICmpInst::ICMP_SLT && CmpRHS->isZero()) || 1019 (Pred == ICmpInst::ICMP_SGT && CmpRHS->isAllOnesValue())) { 1020 Value *Sh = ConstantInt::get(CmpLHS->getType(), 1021 CmpLHS->getType()->getScalarSizeInBits()-1); 1022 Value *In = Builder->CreateAShr(CmpLHS, Sh, CmpLHS->getName()+".lobit"); 1023 if (In->getType() != CI.getType()) 1024 In = Builder->CreateIntCast(In, CI.getType(), true/*SExt*/, "tmp"); 1025 1026 if (Pred == ICmpInst::ICMP_SGT) 1027 In = Builder->CreateNot(In, In->getName()+".not"); 1028 return ReplaceInstUsesWith(CI, In); 1029 } 1030 } 1031 } 1032 1033 // vector (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if signed. 1034 if (const VectorType *VTy = dyn_cast<VectorType>(DestTy)) { 1035 ICmpInst::Predicate Pred; Value *CmpLHS; 1036 if (match(Src, m_ICmp(Pred, m_Value(CmpLHS), m_Zero()))) { 1037 if (Pred == ICmpInst::ICMP_SLT && CmpLHS->getType() == DestTy) { 1038 const Type *EltTy = VTy->getElementType(); 1039 1040 // splat the shift constant to a cosntant vector 1041 Constant *Sh = ConstantInt::get(EltTy, EltTy->getScalarSizeInBits()-1); 1042 std::vector<Constant *> Elts(VTy->getNumElements(), Sh); 1043 Constant *VSh = ConstantVector::get(Elts); 1044 1045 Value *In = Builder->CreateAShr(CmpLHS, VSh,CmpLHS->getName()+".lobit"); 1046 return ReplaceInstUsesWith(CI, In); 1047 } 1048 } 1049 } 1050 1051 // If the input is a shl/ashr pair of a same constant, then this is a sign 1052 // extension from a smaller value. If we could trust arbitrary bitwidth 1053 // integers, we could turn this into a truncate to the smaller bit and then 1054 // use a sext for the whole extension. Since we don't, look deeper and check 1055 // for a truncate. If the source and dest are the same type, eliminate the 1056 // trunc and extend and just do shifts. For example, turn: 1057 // %a = trunc i32 %i to i8 1058 // %b = shl i8 %a, 6 1059 // %c = ashr i8 %b, 6 1060 // %d = sext i8 %c to i32 1061 // into: 1062 // %a = shl i32 %i, 30 1063 // %d = ashr i32 %a, 30 1064 Value *A = 0; 1065 // TODO: Eventually this could be subsumed by EvaluateInDifferentType. 1066 ConstantInt *BA = 0, *CA = 0; 1067 if (match(Src, m_AShr(m_Shl(m_Trunc(m_Value(A)), m_ConstantInt(BA)), 1068 m_ConstantInt(CA))) && 1069 BA == CA && A->getType() == CI.getType()) { 1070 unsigned MidSize = Src->getType()->getScalarSizeInBits(); 1071 unsigned SrcDstSize = CI.getType()->getScalarSizeInBits(); 1072 unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize; 1073 Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt); 1074 A = Builder->CreateShl(A, ShAmtV, CI.getName()); 1075 return BinaryOperator::CreateAShr(A, ShAmtV); 1076 } 1077 1078 return 0; 1079} 1080 1081 1082/// FitsInFPType - Return a Constant* for the specified FP constant if it fits 1083/// in the specified FP type without changing its value. 1084static Constant *FitsInFPType(ConstantFP *CFP, const fltSemantics &Sem) { 1085 bool losesInfo; 1086 APFloat F = CFP->getValueAPF(); 1087 (void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo); 1088 if (!losesInfo) 1089 return ConstantFP::get(CFP->getContext(), F); 1090 return 0; 1091} 1092 1093/// LookThroughFPExtensions - If this is an fp extension instruction, look 1094/// through it until we get the source value. 1095static Value *LookThroughFPExtensions(Value *V) { 1096 if (Instruction *I = dyn_cast<Instruction>(V)) 1097 if (I->getOpcode() == Instruction::FPExt) 1098 return LookThroughFPExtensions(I->getOperand(0)); 1099 1100 // If this value is a constant, return the constant in the smallest FP type 1101 // that can accurately represent it. This allows us to turn 1102 // (float)((double)X+2.0) into x+2.0f. 1103 if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) { 1104 if (CFP->getType() == Type::getPPC_FP128Ty(V->getContext())) 1105 return V; // No constant folding of this. 1106 // See if the value can be truncated to float and then reextended. 1107 if (Value *V = FitsInFPType(CFP, APFloat::IEEEsingle)) 1108 return V; 1109 if (CFP->getType()->isDoubleTy()) 1110 return V; // Won't shrink. 1111 if (Value *V = FitsInFPType(CFP, APFloat::IEEEdouble)) 1112 return V; 1113 // Don't try to shrink to various long double types. 1114 } 1115 1116 return V; 1117} 1118 1119Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) { 1120 if (Instruction *I = commonCastTransforms(CI)) 1121 return I; 1122 1123 // If we have fptrunc(fadd (fpextend x), (fpextend y)), where x and y are 1124 // smaller than the destination type, we can eliminate the truncate by doing 1125 // the add as the smaller type. This applies to fadd/fsub/fmul/fdiv as well 1126 // as many builtins (sqrt, etc). 1127 BinaryOperator *OpI = dyn_cast<BinaryOperator>(CI.getOperand(0)); 1128 if (OpI && OpI->hasOneUse()) { 1129 switch (OpI->getOpcode()) { 1130 default: break; 1131 case Instruction::FAdd: 1132 case Instruction::FSub: 1133 case Instruction::FMul: 1134 case Instruction::FDiv: 1135 case Instruction::FRem: 1136 const Type *SrcTy = OpI->getType(); 1137 Value *LHSTrunc = LookThroughFPExtensions(OpI->getOperand(0)); 1138 Value *RHSTrunc = LookThroughFPExtensions(OpI->getOperand(1)); 1139 if (LHSTrunc->getType() != SrcTy && 1140 RHSTrunc->getType() != SrcTy) { 1141 unsigned DstSize = CI.getType()->getScalarSizeInBits(); 1142 // If the source types were both smaller than the destination type of 1143 // the cast, do this xform. 1144 if (LHSTrunc->getType()->getScalarSizeInBits() <= DstSize && 1145 RHSTrunc->getType()->getScalarSizeInBits() <= DstSize) { 1146 LHSTrunc = Builder->CreateFPExt(LHSTrunc, CI.getType()); 1147 RHSTrunc = Builder->CreateFPExt(RHSTrunc, CI.getType()); 1148 return BinaryOperator::Create(OpI->getOpcode(), LHSTrunc, RHSTrunc); 1149 } 1150 } 1151 break; 1152 } 1153 } 1154 1155 // Fold (fptrunc (sqrt (fpext x))) -> (sqrtf x) 1156 // NOTE: This should be disabled by -fno-builtin-sqrt if we ever support it. 1157 CallInst *Call = dyn_cast<CallInst>(CI.getOperand(0)); 1158 if (Call && Call->getCalledFunction() && 1159 Call->getCalledFunction()->getName() == "sqrt" && 1160 Call->getNumArgOperands() == 1) { 1161 CastInst *Arg = dyn_cast<CastInst>(Call->getArgOperand(0)); 1162 if (Arg && Arg->getOpcode() == Instruction::FPExt && 1163 CI.getType()->isFloatTy() && 1164 Call->getType()->isDoubleTy() && 1165 Arg->getType()->isDoubleTy() && 1166 Arg->getOperand(0)->getType()->isFloatTy()) { 1167 Function *Callee = Call->getCalledFunction(); 1168 Module *M = CI.getParent()->getParent()->getParent(); 1169 Constant *SqrtfFunc = M->getOrInsertFunction("sqrtf", 1170 Callee->getAttributes(), 1171 Builder->getFloatTy(), 1172 Builder->getFloatTy(), 1173 NULL); 1174 CallInst *ret = CallInst::Create(SqrtfFunc, Arg->getOperand(0), 1175 "sqrtfcall"); 1176 ret->setAttributes(Callee->getAttributes()); 1177 1178 1179 // Remove the old Call. With -fmath-errno, it won't get marked readnone. 1180 Call->replaceAllUsesWith(UndefValue::get(Call->getType())); 1181 EraseInstFromFunction(*Call); 1182 return ret; 1183 } 1184 } 1185 1186 return 0; 1187} 1188 1189Instruction *InstCombiner::visitFPExt(CastInst &CI) { 1190 return commonCastTransforms(CI); 1191} 1192 1193Instruction *InstCombiner::visitFPToUI(FPToUIInst &FI) { 1194 Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0)); 1195 if (OpI == 0) 1196 return commonCastTransforms(FI); 1197 1198 // fptoui(uitofp(X)) --> X 1199 // fptoui(sitofp(X)) --> X 1200 // This is safe if the intermediate type has enough bits in its mantissa to 1201 // accurately represent all values of X. For example, do not do this with 1202 // i64->float->i64. This is also safe for sitofp case, because any negative 1203 // 'X' value would cause an undefined result for the fptoui. 1204 if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) && 1205 OpI->getOperand(0)->getType() == FI.getType() && 1206 (int)FI.getType()->getScalarSizeInBits() < /*extra bit for sign */ 1207 OpI->getType()->getFPMantissaWidth()) 1208 return ReplaceInstUsesWith(FI, OpI->getOperand(0)); 1209 1210 return commonCastTransforms(FI); 1211} 1212 1213Instruction *InstCombiner::visitFPToSI(FPToSIInst &FI) { 1214 Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0)); 1215 if (OpI == 0) 1216 return commonCastTransforms(FI); 1217 1218 // fptosi(sitofp(X)) --> X 1219 // fptosi(uitofp(X)) --> X 1220 // This is safe if the intermediate type has enough bits in its mantissa to 1221 // accurately represent all values of X. For example, do not do this with 1222 // i64->float->i64. This is also safe for sitofp case, because any negative 1223 // 'X' value would cause an undefined result for the fptoui. 1224 if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) && 1225 OpI->getOperand(0)->getType() == FI.getType() && 1226 (int)FI.getType()->getScalarSizeInBits() <= 1227 OpI->getType()->getFPMantissaWidth()) 1228 return ReplaceInstUsesWith(FI, OpI->getOperand(0)); 1229 1230 return commonCastTransforms(FI); 1231} 1232 1233Instruction *InstCombiner::visitUIToFP(CastInst &CI) { 1234 return commonCastTransforms(CI); 1235} 1236 1237Instruction *InstCombiner::visitSIToFP(CastInst &CI) { 1238 return commonCastTransforms(CI); 1239} 1240 1241Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) { 1242 // If the source integer type is not the intptr_t type for this target, do a 1243 // trunc or zext to the intptr_t type, then inttoptr of it. This allows the 1244 // cast to be exposed to other transforms. 1245 if (TD) { 1246 if (CI.getOperand(0)->getType()->getScalarSizeInBits() > 1247 TD->getPointerSizeInBits()) { 1248 Value *P = Builder->CreateTrunc(CI.getOperand(0), 1249 TD->getIntPtrType(CI.getContext()), "tmp"); 1250 return new IntToPtrInst(P, CI.getType()); 1251 } 1252 if (CI.getOperand(0)->getType()->getScalarSizeInBits() < 1253 TD->getPointerSizeInBits()) { 1254 Value *P = Builder->CreateZExt(CI.getOperand(0), 1255 TD->getIntPtrType(CI.getContext()), "tmp"); 1256 return new IntToPtrInst(P, CI.getType()); 1257 } 1258 } 1259 1260 if (Instruction *I = commonCastTransforms(CI)) 1261 return I; 1262 1263 return 0; 1264} 1265 1266/// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint) 1267Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) { 1268 Value *Src = CI.getOperand(0); 1269 1270 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) { 1271 // If casting the result of a getelementptr instruction with no offset, turn 1272 // this into a cast of the original pointer! 1273 if (GEP->hasAllZeroIndices()) { 1274 // Changing the cast operand is usually not a good idea but it is safe 1275 // here because the pointer operand is being replaced with another 1276 // pointer operand so the opcode doesn't need to change. 1277 Worklist.Add(GEP); 1278 CI.setOperand(0, GEP->getOperand(0)); 1279 return &CI; 1280 } 1281 1282 // If the GEP has a single use, and the base pointer is a bitcast, and the 1283 // GEP computes a constant offset, see if we can convert these three 1284 // instructions into fewer. This typically happens with unions and other 1285 // non-type-safe code. 1286 if (TD && GEP->hasOneUse() && isa<BitCastInst>(GEP->getOperand(0)) && 1287 GEP->hasAllConstantIndices()) { 1288 // We are guaranteed to get a constant from EmitGEPOffset. 1289 ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(GEP)); 1290 int64_t Offset = OffsetV->getSExtValue(); 1291 1292 // Get the base pointer input of the bitcast, and the type it points to. 1293 Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0); 1294 const Type *GEPIdxTy = 1295 cast<PointerType>(OrigBase->getType())->getElementType(); 1296 SmallVector<Value*, 8> NewIndices; 1297 if (FindElementAtOffset(GEPIdxTy, Offset, NewIndices)) { 1298 // If we were able to index down into an element, create the GEP 1299 // and bitcast the result. This eliminates one bitcast, potentially 1300 // two. 1301 Value *NGEP = cast<GEPOperator>(GEP)->isInBounds() ? 1302 Builder->CreateInBoundsGEP(OrigBase, 1303 NewIndices.begin(), NewIndices.end()) : 1304 Builder->CreateGEP(OrigBase, NewIndices.begin(), NewIndices.end()); 1305 NGEP->takeName(GEP); 1306 1307 if (isa<BitCastInst>(CI)) 1308 return new BitCastInst(NGEP, CI.getType()); 1309 assert(isa<PtrToIntInst>(CI)); 1310 return new PtrToIntInst(NGEP, CI.getType()); 1311 } 1312 } 1313 } 1314 1315 return commonCastTransforms(CI); 1316} 1317 1318Instruction *InstCombiner::visitPtrToInt(PtrToIntInst &CI) { 1319 // If the destination integer type is not the intptr_t type for this target, 1320 // do a ptrtoint to intptr_t then do a trunc or zext. This allows the cast 1321 // to be exposed to other transforms. 1322 if (TD) { 1323 if (CI.getType()->getScalarSizeInBits() < TD->getPointerSizeInBits()) { 1324 Value *P = Builder->CreatePtrToInt(CI.getOperand(0), 1325 TD->getIntPtrType(CI.getContext()), 1326 "tmp"); 1327 return new TruncInst(P, CI.getType()); 1328 } 1329 if (CI.getType()->getScalarSizeInBits() > TD->getPointerSizeInBits()) { 1330 Value *P = Builder->CreatePtrToInt(CI.getOperand(0), 1331 TD->getIntPtrType(CI.getContext()), 1332 "tmp"); 1333 return new ZExtInst(P, CI.getType()); 1334 } 1335 } 1336 1337 return commonPointerCastTransforms(CI); 1338} 1339 1340/// OptimizeVectorResize - This input value (which is known to have vector type) 1341/// is being zero extended or truncated to the specified vector type. Try to 1342/// replace it with a shuffle (and vector/vector bitcast) if possible. 1343/// 1344/// The source and destination vector types may have different element types. 1345static Instruction *OptimizeVectorResize(Value *InVal, const VectorType *DestTy, 1346 InstCombiner &IC) { 1347 // We can only do this optimization if the output is a multiple of the input 1348 // element size, or the input is a multiple of the output element size. 1349 // Convert the input type to have the same element type as the output. 1350 const VectorType *SrcTy = cast<VectorType>(InVal->getType()); 1351 1352 if (SrcTy->getElementType() != DestTy->getElementType()) { 1353 // The input types don't need to be identical, but for now they must be the 1354 // same size. There is no specific reason we couldn't handle things like 1355 // <4 x i16> -> <4 x i32> by bitcasting to <2 x i32> but haven't gotten 1356 // there yet. 1357 if (SrcTy->getElementType()->getPrimitiveSizeInBits() != 1358 DestTy->getElementType()->getPrimitiveSizeInBits()) 1359 return 0; 1360 1361 SrcTy = VectorType::get(DestTy->getElementType(), SrcTy->getNumElements()); 1362 InVal = IC.Builder->CreateBitCast(InVal, SrcTy); 1363 } 1364 1365 // Now that the element types match, get the shuffle mask and RHS of the 1366 // shuffle to use, which depends on whether we're increasing or decreasing the 1367 // size of the input. 1368 SmallVector<Constant*, 16> ShuffleMask; 1369 Value *V2; 1370 const IntegerType *Int32Ty = Type::getInt32Ty(SrcTy->getContext()); 1371 1372 if (SrcTy->getNumElements() > DestTy->getNumElements()) { 1373 // If we're shrinking the number of elements, just shuffle in the low 1374 // elements from the input and use undef as the second shuffle input. 1375 V2 = UndefValue::get(SrcTy); 1376 for (unsigned i = 0, e = DestTy->getNumElements(); i != e; ++i) 1377 ShuffleMask.push_back(ConstantInt::get(Int32Ty, i)); 1378 1379 } else { 1380 // If we're increasing the number of elements, shuffle in all of the 1381 // elements from InVal and fill the rest of the result elements with zeros 1382 // from a constant zero. 1383 V2 = Constant::getNullValue(SrcTy); 1384 unsigned SrcElts = SrcTy->getNumElements(); 1385 for (unsigned i = 0, e = SrcElts; i != e; ++i) 1386 ShuffleMask.push_back(ConstantInt::get(Int32Ty, i)); 1387 1388 // The excess elements reference the first element of the zero input. 1389 ShuffleMask.append(DestTy->getNumElements()-SrcElts, 1390 ConstantInt::get(Int32Ty, SrcElts)); 1391 } 1392 1393 Constant *Mask = ConstantVector::get(ShuffleMask.data(), ShuffleMask.size()); 1394 return new ShuffleVectorInst(InVal, V2, Mask); 1395} 1396 1397static bool isMultipleOfTypeSize(unsigned Value, const Type *Ty) { 1398 return Value % Ty->getPrimitiveSizeInBits() == 0; 1399} 1400 1401static unsigned getTypeSizeIndex(unsigned Value, const Type *Ty) { 1402 return Value / Ty->getPrimitiveSizeInBits(); 1403} 1404 1405/// CollectInsertionElements - V is a value which is inserted into a vector of 1406/// VecEltTy. Look through the value to see if we can decompose it into 1407/// insertions into the vector. See the example in the comment for 1408/// OptimizeIntegerToVectorInsertions for the pattern this handles. 1409/// The type of V is always a non-zero multiple of VecEltTy's size. 1410/// 1411/// This returns false if the pattern can't be matched or true if it can, 1412/// filling in Elements with the elements found here. 1413static bool CollectInsertionElements(Value *V, unsigned ElementIndex, 1414 SmallVectorImpl<Value*> &Elements, 1415 const Type *VecEltTy) { 1416 // Undef values never contribute useful bits to the result. 1417 if (isa<UndefValue>(V)) return true; 1418 1419 // If we got down to a value of the right type, we win, try inserting into the 1420 // right element. 1421 if (V->getType() == VecEltTy) { 1422 // Inserting null doesn't actually insert any elements. 1423 if (Constant *C = dyn_cast<Constant>(V)) 1424 if (C->isNullValue()) 1425 return true; 1426 1427 // Fail if multiple elements are inserted into this slot. 1428 if (ElementIndex >= Elements.size() || Elements[ElementIndex] != 0) 1429 return false; 1430 1431 Elements[ElementIndex] = V; 1432 return true; 1433 } 1434 1435 if (Constant *C = dyn_cast<Constant>(V)) { 1436 // Figure out the # elements this provides, and bitcast it or slice it up 1437 // as required. 1438 unsigned NumElts = getTypeSizeIndex(C->getType()->getPrimitiveSizeInBits(), 1439 VecEltTy); 1440 // If the constant is the size of a vector element, we just need to bitcast 1441 // it to the right type so it gets properly inserted. 1442 if (NumElts == 1) 1443 return CollectInsertionElements(ConstantExpr::getBitCast(C, VecEltTy), 1444 ElementIndex, Elements, VecEltTy); 1445 1446 // Okay, this is a constant that covers multiple elements. Slice it up into 1447 // pieces and insert each element-sized piece into the vector. 1448 if (!isa<IntegerType>(C->getType())) 1449 C = ConstantExpr::getBitCast(C, IntegerType::get(V->getContext(), 1450 C->getType()->getPrimitiveSizeInBits())); 1451 unsigned ElementSize = VecEltTy->getPrimitiveSizeInBits(); 1452 const Type *ElementIntTy = IntegerType::get(C->getContext(), ElementSize); 1453 1454 for (unsigned i = 0; i != NumElts; ++i) { 1455 Constant *Piece = ConstantExpr::getLShr(C, ConstantInt::get(C->getType(), 1456 i*ElementSize)); 1457 Piece = ConstantExpr::getTrunc(Piece, ElementIntTy); 1458 if (!CollectInsertionElements(Piece, ElementIndex+i, Elements, VecEltTy)) 1459 return false; 1460 } 1461 return true; 1462 } 1463 1464 if (!V->hasOneUse()) return false; 1465 1466 Instruction *I = dyn_cast<Instruction>(V); 1467 if (I == 0) return false; 1468 switch (I->getOpcode()) { 1469 default: return false; // Unhandled case. 1470 case Instruction::BitCast: 1471 return CollectInsertionElements(I->getOperand(0), ElementIndex, 1472 Elements, VecEltTy); 1473 case Instruction::ZExt: 1474 if (!isMultipleOfTypeSize( 1475 I->getOperand(0)->getType()->getPrimitiveSizeInBits(), 1476 VecEltTy)) 1477 return false; 1478 return CollectInsertionElements(I->getOperand(0), ElementIndex, 1479 Elements, VecEltTy); 1480 case Instruction::Or: 1481 return CollectInsertionElements(I->getOperand(0), ElementIndex, 1482 Elements, VecEltTy) && 1483 CollectInsertionElements(I->getOperand(1), ElementIndex, 1484 Elements, VecEltTy); 1485 case Instruction::Shl: { 1486 // Must be shifting by a constant that is a multiple of the element size. 1487 ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1)); 1488 if (CI == 0) return false; 1489 if (!isMultipleOfTypeSize(CI->getZExtValue(), VecEltTy)) return false; 1490 unsigned IndexShift = getTypeSizeIndex(CI->getZExtValue(), VecEltTy); 1491 1492 return CollectInsertionElements(I->getOperand(0), ElementIndex+IndexShift, 1493 Elements, VecEltTy); 1494 } 1495 1496 } 1497} 1498 1499 1500/// OptimizeIntegerToVectorInsertions - If the input is an 'or' instruction, we 1501/// may be doing shifts and ors to assemble the elements of the vector manually. 1502/// Try to rip the code out and replace it with insertelements. This is to 1503/// optimize code like this: 1504/// 1505/// %tmp37 = bitcast float %inc to i32 1506/// %tmp38 = zext i32 %tmp37 to i64 1507/// %tmp31 = bitcast float %inc5 to i32 1508/// %tmp32 = zext i32 %tmp31 to i64 1509/// %tmp33 = shl i64 %tmp32, 32 1510/// %ins35 = or i64 %tmp33, %tmp38 1511/// %tmp43 = bitcast i64 %ins35 to <2 x float> 1512/// 1513/// Into two insertelements that do "buildvector{%inc, %inc5}". 1514static Value *OptimizeIntegerToVectorInsertions(BitCastInst &CI, 1515 InstCombiner &IC) { 1516 const VectorType *DestVecTy = cast<VectorType>(CI.getType()); 1517 Value *IntInput = CI.getOperand(0); 1518 1519 SmallVector<Value*, 8> Elements(DestVecTy->getNumElements()); 1520 if (!CollectInsertionElements(IntInput, 0, Elements, 1521 DestVecTy->getElementType())) 1522 return 0; 1523 1524 // If we succeeded, we know that all of the element are specified by Elements 1525 // or are zero if Elements has a null entry. Recast this as a set of 1526 // insertions. 1527 Value *Result = Constant::getNullValue(CI.getType()); 1528 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 1529 if (Elements[i] == 0) continue; // Unset element. 1530 1531 Result = IC.Builder->CreateInsertElement(Result, Elements[i], 1532 IC.Builder->getInt32(i)); 1533 } 1534 1535 return Result; 1536} 1537 1538 1539/// OptimizeIntToFloatBitCast - See if we can optimize an integer->float/double 1540/// bitcast. The various long double bitcasts can't get in here. 1541static Instruction *OptimizeIntToFloatBitCast(BitCastInst &CI,InstCombiner &IC){ 1542 Value *Src = CI.getOperand(0); 1543 const Type *DestTy = CI.getType(); 1544 1545 // If this is a bitcast from int to float, check to see if the int is an 1546 // extraction from a vector. 1547 Value *VecInput = 0; 1548 // bitcast(trunc(bitcast(somevector))) 1549 if (match(Src, m_Trunc(m_BitCast(m_Value(VecInput)))) && 1550 isa<VectorType>(VecInput->getType())) { 1551 const VectorType *VecTy = cast<VectorType>(VecInput->getType()); 1552 unsigned DestWidth = DestTy->getPrimitiveSizeInBits(); 1553 1554 if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0) { 1555 // If the element type of the vector doesn't match the result type, 1556 // bitcast it to be a vector type we can extract from. 1557 if (VecTy->getElementType() != DestTy) { 1558 VecTy = VectorType::get(DestTy, 1559 VecTy->getPrimitiveSizeInBits() / DestWidth); 1560 VecInput = IC.Builder->CreateBitCast(VecInput, VecTy); 1561 } 1562 1563 return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(0)); 1564 } 1565 } 1566 1567 // bitcast(trunc(lshr(bitcast(somevector), cst)) 1568 ConstantInt *ShAmt = 0; 1569 if (match(Src, m_Trunc(m_LShr(m_BitCast(m_Value(VecInput)), 1570 m_ConstantInt(ShAmt)))) && 1571 isa<VectorType>(VecInput->getType())) { 1572 const VectorType *VecTy = cast<VectorType>(VecInput->getType()); 1573 unsigned DestWidth = DestTy->getPrimitiveSizeInBits(); 1574 if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0 && 1575 ShAmt->getZExtValue() % DestWidth == 0) { 1576 // If the element type of the vector doesn't match the result type, 1577 // bitcast it to be a vector type we can extract from. 1578 if (VecTy->getElementType() != DestTy) { 1579 VecTy = VectorType::get(DestTy, 1580 VecTy->getPrimitiveSizeInBits() / DestWidth); 1581 VecInput = IC.Builder->CreateBitCast(VecInput, VecTy); 1582 } 1583 1584 unsigned Elt = ShAmt->getZExtValue() / DestWidth; 1585 return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt)); 1586 } 1587 } 1588 return 0; 1589} 1590 1591Instruction *InstCombiner::visitBitCast(BitCastInst &CI) { 1592 // If the operands are integer typed then apply the integer transforms, 1593 // otherwise just apply the common ones. 1594 Value *Src = CI.getOperand(0); 1595 const Type *SrcTy = Src->getType(); 1596 const Type *DestTy = CI.getType(); 1597 1598 // Get rid of casts from one type to the same type. These are useless and can 1599 // be replaced by the operand. 1600 if (DestTy == Src->getType()) 1601 return ReplaceInstUsesWith(CI, Src); 1602 1603 if (const PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) { 1604 const PointerType *SrcPTy = cast<PointerType>(SrcTy); 1605 const Type *DstElTy = DstPTy->getElementType(); 1606 const Type *SrcElTy = SrcPTy->getElementType(); 1607 1608 // If the address spaces don't match, don't eliminate the bitcast, which is 1609 // required for changing types. 1610 if (SrcPTy->getAddressSpace() != DstPTy->getAddressSpace()) 1611 return 0; 1612 1613 // If we are casting a alloca to a pointer to a type of the same 1614 // size, rewrite the allocation instruction to allocate the "right" type. 1615 // There is no need to modify malloc calls because it is their bitcast that 1616 // needs to be cleaned up. 1617 if (AllocaInst *AI = dyn_cast<AllocaInst>(Src)) 1618 if (Instruction *V = PromoteCastOfAllocation(CI, *AI)) 1619 return V; 1620 1621 // If the source and destination are pointers, and this cast is equivalent 1622 // to a getelementptr X, 0, 0, 0... turn it into the appropriate gep. 1623 // This can enhance SROA and other transforms that want type-safe pointers. 1624 Constant *ZeroUInt = 1625 Constant::getNullValue(Type::getInt32Ty(CI.getContext())); 1626 unsigned NumZeros = 0; 1627 while (SrcElTy != DstElTy && 1628 isa<CompositeType>(SrcElTy) && !SrcElTy->isPointerTy() && 1629 SrcElTy->getNumContainedTypes() /* not "{}" */) { 1630 SrcElTy = cast<CompositeType>(SrcElTy)->getTypeAtIndex(ZeroUInt); 1631 ++NumZeros; 1632 } 1633 1634 // If we found a path from the src to dest, create the getelementptr now. 1635 if (SrcElTy == DstElTy) { 1636 SmallVector<Value*, 8> Idxs(NumZeros+1, ZeroUInt); 1637 return GetElementPtrInst::CreateInBounds(Src, Idxs.begin(), Idxs.end(),"", 1638 ((Instruction*)NULL)); 1639 } 1640 } 1641 1642 // Try to optimize int -> float bitcasts. 1643 if ((DestTy->isFloatTy() || DestTy->isDoubleTy()) && isa<IntegerType>(SrcTy)) 1644 if (Instruction *I = OptimizeIntToFloatBitCast(CI, *this)) 1645 return I; 1646 1647 if (const VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) { 1648 if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) { 1649 Value *Elem = Builder->CreateBitCast(Src, DestVTy->getElementType()); 1650 return InsertElementInst::Create(UndefValue::get(DestTy), Elem, 1651 Constant::getNullValue(Type::getInt32Ty(CI.getContext()))); 1652 // FIXME: Canonicalize bitcast(insertelement) -> insertelement(bitcast) 1653 } 1654 1655 if (isa<IntegerType>(SrcTy)) { 1656 // If this is a cast from an integer to vector, check to see if the input 1657 // is a trunc or zext of a bitcast from vector. If so, we can replace all 1658 // the casts with a shuffle and (potentially) a bitcast. 1659 if (isa<TruncInst>(Src) || isa<ZExtInst>(Src)) { 1660 CastInst *SrcCast = cast<CastInst>(Src); 1661 if (BitCastInst *BCIn = dyn_cast<BitCastInst>(SrcCast->getOperand(0))) 1662 if (isa<VectorType>(BCIn->getOperand(0)->getType())) 1663 if (Instruction *I = OptimizeVectorResize(BCIn->getOperand(0), 1664 cast<VectorType>(DestTy), *this)) 1665 return I; 1666 } 1667 1668 // If the input is an 'or' instruction, we may be doing shifts and ors to 1669 // assemble the elements of the vector manually. Try to rip the code out 1670 // and replace it with insertelements. 1671 if (Value *V = OptimizeIntegerToVectorInsertions(CI, *this)) 1672 return ReplaceInstUsesWith(CI, V); 1673 } 1674 } 1675 1676 if (const VectorType *SrcVTy = dyn_cast<VectorType>(SrcTy)) { 1677 if (SrcVTy->getNumElements() == 1 && !DestTy->isVectorTy()) { 1678 Value *Elem = 1679 Builder->CreateExtractElement(Src, 1680 Constant::getNullValue(Type::getInt32Ty(CI.getContext()))); 1681 return CastInst::Create(Instruction::BitCast, Elem, DestTy); 1682 } 1683 } 1684 1685 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(Src)) { 1686 // Okay, we have (bitcast (shuffle ..)). Check to see if this is 1687 // a bitcast to a vector with the same # elts. 1688 if (SVI->hasOneUse() && DestTy->isVectorTy() && 1689 cast<VectorType>(DestTy)->getNumElements() == 1690 SVI->getType()->getNumElements() && 1691 SVI->getType()->getNumElements() == 1692 cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements()) { 1693 BitCastInst *Tmp; 1694 // If either of the operands is a cast from CI.getType(), then 1695 // evaluating the shuffle in the casted destination's type will allow 1696 // us to eliminate at least one cast. 1697 if (((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(0))) && 1698 Tmp->getOperand(0)->getType() == DestTy) || 1699 ((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(1))) && 1700 Tmp->getOperand(0)->getType() == DestTy)) { 1701 Value *LHS = Builder->CreateBitCast(SVI->getOperand(0), DestTy); 1702 Value *RHS = Builder->CreateBitCast(SVI->getOperand(1), DestTy); 1703 // Return a new shuffle vector. Use the same element ID's, as we 1704 // know the vector types match #elts. 1705 return new ShuffleVectorInst(LHS, RHS, SVI->getOperand(2)); 1706 } 1707 } 1708 } 1709 1710 if (SrcTy->isPointerTy()) 1711 return commonPointerCastTransforms(CI); 1712 return commonCastTransforms(CI); 1713} 1714