InstCombineCasts.cpp revision aa76e9e2cf50af190de90bc778b7f7e42ef9ceff
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/Analysis/ConstantFolding.h" 16#include "llvm/DataLayout.h" 17#include "llvm/Target/TargetLibraryInfo.h" 18#include "llvm/Support/PatternMatch.h" 19using namespace llvm; 20using namespace PatternMatch; 21 22/// DecomposeSimpleLinearExpr - Analyze 'Val', seeing if it is a simple linear 23/// expression. If so, decompose it, returning some value X, such that Val is 24/// X*Scale+Offset. 25/// 26static Value *DecomposeSimpleLinearExpr(Value *Val, unsigned &Scale, 27 uint64_t &Offset) { 28 if (ConstantInt *CI = dyn_cast<ConstantInt>(Val)) { 29 Offset = CI->getZExtValue(); 30 Scale = 0; 31 return ConstantInt::get(Val->getType(), 0); 32 } 33 34 if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) { 35 // Cannot look past anything that might overflow. 36 OverflowingBinaryOperator *OBI = dyn_cast<OverflowingBinaryOperator>(Val); 37 if (OBI && !OBI->hasNoUnsignedWrap() && !OBI->hasNoSignedWrap()) { 38 Scale = 1; 39 Offset = 0; 40 return Val; 41 } 42 43 if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) { 44 if (I->getOpcode() == Instruction::Shl) { 45 // This is a value scaled by '1 << the shift amt'. 46 Scale = UINT64_C(1) << RHS->getZExtValue(); 47 Offset = 0; 48 return I->getOperand(0); 49 } 50 51 if (I->getOpcode() == Instruction::Mul) { 52 // This value is scaled by 'RHS'. 53 Scale = RHS->getZExtValue(); 54 Offset = 0; 55 return I->getOperand(0); 56 } 57 58 if (I->getOpcode() == Instruction::Add) { 59 // We have X+C. Check to see if we really have (X*C2)+C1, 60 // where C1 is divisible by C2. 61 unsigned SubScale; 62 Value *SubVal = 63 DecomposeSimpleLinearExpr(I->getOperand(0), SubScale, Offset); 64 Offset += RHS->getZExtValue(); 65 Scale = SubScale; 66 return SubVal; 67 } 68 } 69 } 70 71 // Otherwise, we can't look past this. 72 Scale = 1; 73 Offset = 0; 74 return Val; 75} 76 77/// PromoteCastOfAllocation - If we find a cast of an allocation instruction, 78/// try to eliminate the cast by moving the type information into the alloc. 79Instruction *InstCombiner::PromoteCastOfAllocation(BitCastInst &CI, 80 AllocaInst &AI) { 81 // This requires DataLayout to get the alloca alignment and size information. 82 if (!TD) return 0; 83 84 PointerType *PTy = cast<PointerType>(CI.getType()); 85 86 BuilderTy AllocaBuilder(*Builder); 87 AllocaBuilder.SetInsertPoint(AI.getParent(), &AI); 88 89 // Get the type really allocated and the type casted to. 90 Type *AllocElTy = AI.getAllocatedType(); 91 Type *CastElTy = PTy->getElementType(); 92 if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0; 93 94 unsigned AllocElTyAlign = TD->getABITypeAlignment(AllocElTy); 95 unsigned CastElTyAlign = TD->getABITypeAlignment(CastElTy); 96 if (CastElTyAlign < AllocElTyAlign) return 0; 97 98 // If the allocation has multiple uses, only promote it if we are strictly 99 // increasing the alignment of the resultant allocation. If we keep it the 100 // same, we open the door to infinite loops of various kinds. 101 if (!AI.hasOneUse() && CastElTyAlign == AllocElTyAlign) return 0; 102 103 uint64_t AllocElTySize = TD->getTypeAllocSize(AllocElTy); 104 uint64_t CastElTySize = TD->getTypeAllocSize(CastElTy); 105 if (CastElTySize == 0 || AllocElTySize == 0) return 0; 106 107 // See if we can satisfy the modulus by pulling a scale out of the array 108 // size argument. 109 unsigned ArraySizeScale; 110 uint64_t ArrayOffset; 111 Value *NumElements = // See if the array size is a decomposable linear expr. 112 DecomposeSimpleLinearExpr(AI.getOperand(0), ArraySizeScale, ArrayOffset); 113 114 // If we can now satisfy the modulus, by using a non-1 scale, we really can 115 // do the xform. 116 if ((AllocElTySize*ArraySizeScale) % CastElTySize != 0 || 117 (AllocElTySize*ArrayOffset ) % CastElTySize != 0) return 0; 118 119 unsigned Scale = (AllocElTySize*ArraySizeScale)/CastElTySize; 120 Value *Amt = 0; 121 if (Scale == 1) { 122 Amt = NumElements; 123 } else { 124 Amt = ConstantInt::get(AI.getArraySize()->getType(), Scale); 125 // Insert before the alloca, not before the cast. 126 Amt = AllocaBuilder.CreateMul(Amt, NumElements); 127 } 128 129 if (uint64_t Offset = (AllocElTySize*ArrayOffset)/CastElTySize) { 130 Value *Off = ConstantInt::get(AI.getArraySize()->getType(), 131 Offset, true); 132 Amt = AllocaBuilder.CreateAdd(Amt, Off); 133 } 134 135 AllocaInst *New = AllocaBuilder.CreateAlloca(CastElTy, Amt); 136 New->setAlignment(AI.getAlignment()); 137 New->takeName(&AI); 138 139 // If the allocation has multiple real uses, insert a cast and change all 140 // things that used it to use the new cast. This will also hack on CI, but it 141 // will die soon. 142 if (!AI.hasOneUse()) { 143 // New is the allocation instruction, pointer typed. AI is the original 144 // allocation instruction, also pointer typed. Thus, cast to use is BitCast. 145 Value *NewCast = AllocaBuilder.CreateBitCast(New, AI.getType(), "tmpcast"); 146 ReplaceInstUsesWith(AI, NewCast); 147 } 148 return ReplaceInstUsesWith(CI, New); 149} 150 151/// EvaluateInDifferentType - Given an expression that 152/// CanEvaluateTruncated or CanEvaluateSExtd returns true for, actually 153/// insert the code to evaluate the expression. 154Value *InstCombiner::EvaluateInDifferentType(Value *V, Type *Ty, 155 bool isSigned) { 156 if (Constant *C = dyn_cast<Constant>(V)) { 157 C = ConstantExpr::getIntegerCast(C, Ty, isSigned /*Sext or ZExt*/); 158 // If we got a constantexpr back, try to simplify it with TD info. 159 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 160 C = ConstantFoldConstantExpression(CE, TD, TLI); 161 return C; 162 } 163 164 // Otherwise, it must be an instruction. 165 Instruction *I = cast<Instruction>(V); 166 Instruction *Res = 0; 167 unsigned Opc = I->getOpcode(); 168 switch (Opc) { 169 case Instruction::Add: 170 case Instruction::Sub: 171 case Instruction::Mul: 172 case Instruction::And: 173 case Instruction::Or: 174 case Instruction::Xor: 175 case Instruction::AShr: 176 case Instruction::LShr: 177 case Instruction::Shl: 178 case Instruction::UDiv: 179 case Instruction::URem: { 180 Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned); 181 Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned); 182 Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS); 183 break; 184 } 185 case Instruction::Trunc: 186 case Instruction::ZExt: 187 case Instruction::SExt: 188 // If the source type of the cast is the type we're trying for then we can 189 // just return the source. There's no need to insert it because it is not 190 // new. 191 if (I->getOperand(0)->getType() == Ty) 192 return I->getOperand(0); 193 194 // Otherwise, must be the same type of cast, so just reinsert a new one. 195 // This also handles the case of zext(trunc(x)) -> zext(x). 196 Res = CastInst::CreateIntegerCast(I->getOperand(0), Ty, 197 Opc == Instruction::SExt); 198 break; 199 case Instruction::Select: { 200 Value *True = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned); 201 Value *False = EvaluateInDifferentType(I->getOperand(2), Ty, isSigned); 202 Res = SelectInst::Create(I->getOperand(0), True, False); 203 break; 204 } 205 case Instruction::PHI: { 206 PHINode *OPN = cast<PHINode>(I); 207 PHINode *NPN = PHINode::Create(Ty, OPN->getNumIncomingValues()); 208 for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; ++i) { 209 Value *V =EvaluateInDifferentType(OPN->getIncomingValue(i), Ty, isSigned); 210 NPN->addIncoming(V, OPN->getIncomingBlock(i)); 211 } 212 Res = NPN; 213 break; 214 } 215 default: 216 // TODO: Can handle more cases here. 217 llvm_unreachable("Unreachable!"); 218 } 219 220 Res->takeName(I); 221 return InsertNewInstWith(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 Type *DstTy, ///< The target type for the second cast instruction 232 DataLayout *TD ///< The target data for pointer size 233) { 234 235 Type *SrcTy = CI->getOperand(0)->getType(); // A from above 236 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 unsigned Res = CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, 242 DstTy, 243 TD ? TD->getIntPtrType(DstTy) : 0); 244 245 // We don't want to form an inttoptr or ptrtoint that converts to an integer 246 // type that differs from the pointer size. 247 if ((Res == Instruction::IntToPtr && 248 (!TD || SrcTy != TD->getIntPtrType(DstTy))) || 249 (Res == Instruction::PtrToInt && 250 (!TD || DstTy != TD->getIntPtrType(SrcTy)))) 251 Res = 0; 252 253 return Instruction::CastOps(Res); 254} 255 256/// ShouldOptimizeCast - Return true if the cast from "V to Ty" actually 257/// results in any code being generated and is interesting to optimize out. If 258/// the cast can be eliminated by some other simple transformation, we prefer 259/// to do the simplification first. 260bool InstCombiner::ShouldOptimizeCast(Instruction::CastOps opc, const Value *V, 261 Type *Ty) { 262 // Noop casts and casts of constants should be eliminated trivially. 263 if (V->getType() == Ty || isa<Constant>(V)) return false; 264 265 // If this is another cast that can be eliminated, we prefer to have it 266 // eliminated. 267 if (const CastInst *CI = dyn_cast<CastInst>(V)) 268 if (isEliminableCastPair(CI, opc, Ty, TD)) 269 return false; 270 271 // If this is a vector sext from a compare, then we don't want to break the 272 // idiom where each element of the extended vector is either zero or all ones. 273 if (opc == Instruction::SExt && isa<CmpInst>(V) && Ty->isVectorTy()) 274 return false; 275 276 return true; 277} 278 279 280/// @brief Implement the transforms common to all CastInst visitors. 281Instruction *InstCombiner::commonCastTransforms(CastInst &CI) { 282 Value *Src = CI.getOperand(0); 283 284 // Many cases of "cast of a cast" are eliminable. If it's eliminable we just 285 // eliminate it now. 286 if (CastInst *CSrc = dyn_cast<CastInst>(Src)) { // A->B->C cast 287 if (Instruction::CastOps opc = 288 isEliminableCastPair(CSrc, CI.getOpcode(), CI.getType(), TD)) { 289 // The first cast (CSrc) is eliminable so we need to fix up or replace 290 // the second cast (CI). CSrc will then have a good chance of being dead. 291 return CastInst::Create(opc, CSrc->getOperand(0), CI.getType()); 292 } 293 } 294 295 // If we are casting a select then fold the cast into the select 296 if (SelectInst *SI = dyn_cast<SelectInst>(Src)) 297 if (Instruction *NV = FoldOpIntoSelect(CI, SI)) 298 return NV; 299 300 // If we are casting a PHI then fold the cast into the PHI 301 if (isa<PHINode>(Src)) { 302 // We don't do this if this would create a PHI node with an illegal type if 303 // it is currently legal. 304 if (!Src->getType()->isIntegerTy() || 305 !CI.getType()->isIntegerTy() || 306 ShouldChangeType(CI.getType(), Src->getType())) 307 if (Instruction *NV = FoldOpIntoPhi(CI)) 308 return NV; 309 } 310 311 return 0; 312} 313 314/// CanEvaluateTruncated - Return true if we can evaluate the specified 315/// expression tree as type Ty instead of its larger type, and arrive with the 316/// same value. This is used by code that tries to eliminate truncates. 317/// 318/// Ty will always be a type smaller than V. We should return true if trunc(V) 319/// can be computed by computing V in the smaller type. If V is an instruction, 320/// then trunc(inst(x,y)) can be computed as inst(trunc(x),trunc(y)), which only 321/// makes sense if x and y can be efficiently truncated. 322/// 323/// This function works on both vectors and scalars. 324/// 325static bool CanEvaluateTruncated(Value *V, Type *Ty) { 326 // We can always evaluate constants in another type. 327 if (isa<Constant>(V)) 328 return true; 329 330 Instruction *I = dyn_cast<Instruction>(V); 331 if (!I) return false; 332 333 Type *OrigTy = V->getType(); 334 335 // If this is an extension from the dest type, we can eliminate it, even if it 336 // has multiple uses. 337 if ((isa<ZExtInst>(I) || isa<SExtInst>(I)) && 338 I->getOperand(0)->getType() == Ty) 339 return true; 340 341 // We can't extend or shrink something that has multiple uses: doing so would 342 // require duplicating the instruction in general, which isn't profitable. 343 if (!I->hasOneUse()) return false; 344 345 unsigned Opc = I->getOpcode(); 346 switch (Opc) { 347 case Instruction::Add: 348 case Instruction::Sub: 349 case Instruction::Mul: 350 case Instruction::And: 351 case Instruction::Or: 352 case Instruction::Xor: 353 // These operators can all arbitrarily be extended or truncated. 354 return CanEvaluateTruncated(I->getOperand(0), Ty) && 355 CanEvaluateTruncated(I->getOperand(1), Ty); 356 357 case Instruction::UDiv: 358 case Instruction::URem: { 359 // UDiv and URem can be truncated if all the truncated bits are zero. 360 uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits(); 361 uint32_t BitWidth = Ty->getScalarSizeInBits(); 362 if (BitWidth < OrigBitWidth) { 363 APInt Mask = APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth); 364 if (MaskedValueIsZero(I->getOperand(0), Mask) && 365 MaskedValueIsZero(I->getOperand(1), Mask)) { 366 return CanEvaluateTruncated(I->getOperand(0), Ty) && 367 CanEvaluateTruncated(I->getOperand(1), Ty); 368 } 369 } 370 break; 371 } 372 case Instruction::Shl: 373 // If we are truncating the result of this SHL, and if it's a shift of a 374 // constant amount, we can always perform a SHL in a smaller type. 375 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) { 376 uint32_t BitWidth = Ty->getScalarSizeInBits(); 377 if (CI->getLimitedValue(BitWidth) < BitWidth) 378 return CanEvaluateTruncated(I->getOperand(0), Ty); 379 } 380 break; 381 case Instruction::LShr: 382 // If this is a truncate of a logical shr, we can truncate it to a smaller 383 // lshr iff we know that the bits we would otherwise be shifting in are 384 // already zeros. 385 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) { 386 uint32_t OrigBitWidth = OrigTy->getScalarSizeInBits(); 387 uint32_t BitWidth = Ty->getScalarSizeInBits(); 388 if (MaskedValueIsZero(I->getOperand(0), 389 APInt::getHighBitsSet(OrigBitWidth, OrigBitWidth-BitWidth)) && 390 CI->getLimitedValue(BitWidth) < BitWidth) { 391 return CanEvaluateTruncated(I->getOperand(0), Ty); 392 } 393 } 394 break; 395 case Instruction::Trunc: 396 // trunc(trunc(x)) -> trunc(x) 397 return true; 398 case Instruction::ZExt: 399 case Instruction::SExt: 400 // trunc(ext(x)) -> ext(x) if the source type is smaller than the new dest 401 // trunc(ext(x)) -> trunc(x) if the source type is larger than the new dest 402 return true; 403 case Instruction::Select: { 404 SelectInst *SI = cast<SelectInst>(I); 405 return CanEvaluateTruncated(SI->getTrueValue(), Ty) && 406 CanEvaluateTruncated(SI->getFalseValue(), Ty); 407 } 408 case Instruction::PHI: { 409 // We can change a phi if we can change all operands. Note that we never 410 // get into trouble with cyclic PHIs here because we only consider 411 // instructions with a single use. 412 PHINode *PN = cast<PHINode>(I); 413 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 414 if (!CanEvaluateTruncated(PN->getIncomingValue(i), Ty)) 415 return false; 416 return true; 417 } 418 default: 419 // TODO: Can handle more cases here. 420 break; 421 } 422 423 return false; 424} 425 426Instruction *InstCombiner::visitTrunc(TruncInst &CI) { 427 if (Instruction *Result = commonCastTransforms(CI)) 428 return Result; 429 430 // See if we can simplify any instructions used by the input whose sole 431 // purpose is to compute bits we don't care about. 432 if (SimplifyDemandedInstructionBits(CI)) 433 return &CI; 434 435 Value *Src = CI.getOperand(0); 436 Type *DestTy = CI.getType(), *SrcTy = Src->getType(); 437 438 // Attempt to truncate the entire input expression tree to the destination 439 // type. Only do this if the dest type is a simple type, don't convert the 440 // expression tree to something weird like i93 unless the source is also 441 // strange. 442 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && 443 CanEvaluateTruncated(Src, DestTy)) { 444 445 // If this cast is a truncate, evaluting in a different type always 446 // eliminates the cast, so it is always a win. 447 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" 448 " to avoid cast: " << CI << '\n'); 449 Value *Res = EvaluateInDifferentType(Src, DestTy, false); 450 assert(Res->getType() == DestTy); 451 return ReplaceInstUsesWith(CI, Res); 452 } 453 454 // Canonicalize trunc x to i1 -> (icmp ne (and x, 1), 0), likewise for vector. 455 if (DestTy->getScalarSizeInBits() == 1) { 456 Constant *One = ConstantInt::get(Src->getType(), 1); 457 Src = Builder->CreateAnd(Src, One); 458 Value *Zero = Constant::getNullValue(Src->getType()); 459 return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero); 460 } 461 462 // Transform trunc(lshr (zext A), Cst) to eliminate one type conversion. 463 Value *A = 0; ConstantInt *Cst = 0; 464 if (Src->hasOneUse() && 465 match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) { 466 // We have three types to worry about here, the type of A, the source of 467 // the truncate (MidSize), and the destination of the truncate. We know that 468 // ASize < MidSize and MidSize > ResultSize, but don't know the relation 469 // between ASize and ResultSize. 470 unsigned ASize = A->getType()->getPrimitiveSizeInBits(); 471 472 // If the shift amount is larger than the size of A, then the result is 473 // known to be zero because all the input bits got shifted out. 474 if (Cst->getZExtValue() >= ASize) 475 return ReplaceInstUsesWith(CI, Constant::getNullValue(CI.getType())); 476 477 // Since we're doing an lshr and a zero extend, and know that the shift 478 // amount is smaller than ASize, it is always safe to do the shift in A's 479 // type, then zero extend or truncate to the result. 480 Value *Shift = Builder->CreateLShr(A, Cst->getZExtValue()); 481 Shift->takeName(Src); 482 return CastInst::CreateIntegerCast(Shift, CI.getType(), false); 483 } 484 485 // Transform "trunc (and X, cst)" -> "and (trunc X), cst" so long as the dest 486 // type isn't non-native. 487 if (Src->hasOneUse() && isa<IntegerType>(Src->getType()) && 488 ShouldChangeType(Src->getType(), CI.getType()) && 489 match(Src, m_And(m_Value(A), m_ConstantInt(Cst)))) { 490 Value *NewTrunc = Builder->CreateTrunc(A, CI.getType(), A->getName()+".tr"); 491 return BinaryOperator::CreateAnd(NewTrunc, 492 ConstantExpr::getTrunc(Cst, CI.getType())); 493 } 494 495 return 0; 496} 497 498/// transformZExtICmp - Transform (zext icmp) to bitwise / integer operations 499/// in order to eliminate the icmp. 500Instruction *InstCombiner::transformZExtICmp(ICmpInst *ICI, Instruction &CI, 501 bool DoXform) { 502 // If we are just checking for a icmp eq of a single bit and zext'ing it 503 // to an integer, then shift the bit to the appropriate place and then 504 // cast to integer to avoid the comparison. 505 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(ICI->getOperand(1))) { 506 const APInt &Op1CV = Op1C->getValue(); 507 508 // zext (x <s 0) to i32 --> x>>u31 true if signbit set. 509 // zext (x >s -1) to i32 --> (x>>u31)^1 true if signbit clear. 510 if ((ICI->getPredicate() == ICmpInst::ICMP_SLT && Op1CV == 0) || 511 (ICI->getPredicate() == ICmpInst::ICMP_SGT &&Op1CV.isAllOnesValue())) { 512 if (!DoXform) return ICI; 513 514 Value *In = ICI->getOperand(0); 515 Value *Sh = ConstantInt::get(In->getType(), 516 In->getType()->getScalarSizeInBits()-1); 517 In = Builder->CreateLShr(In, Sh, In->getName()+".lobit"); 518 if (In->getType() != CI.getType()) 519 In = Builder->CreateIntCast(In, CI.getType(), false/*ZExt*/); 520 521 if (ICI->getPredicate() == ICmpInst::ICMP_SGT) { 522 Constant *One = ConstantInt::get(In->getType(), 1); 523 In = Builder->CreateXor(In, One, In->getName()+".not"); 524 } 525 526 return ReplaceInstUsesWith(CI, In); 527 } 528 529 // zext (X == 0) to i32 --> X^1 iff X has only the low bit set. 530 // zext (X == 0) to i32 --> (X>>1)^1 iff X has only the 2nd bit set. 531 // zext (X == 1) to i32 --> X iff X has only the low bit set. 532 // zext (X == 2) to i32 --> X>>1 iff X has only the 2nd bit set. 533 // zext (X != 0) to i32 --> X iff X has only the low bit set. 534 // zext (X != 0) to i32 --> X>>1 iff X has only the 2nd bit set. 535 // zext (X != 1) to i32 --> X^1 iff X has only the low bit set. 536 // zext (X != 2) to i32 --> (X>>1)^1 iff X has only the 2nd bit set. 537 if ((Op1CV == 0 || Op1CV.isPowerOf2()) && 538 // This only works for EQ and NE 539 ICI->isEquality()) { 540 // If Op1C some other power of two, convert: 541 uint32_t BitWidth = Op1C->getType()->getBitWidth(); 542 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); 543 ComputeMaskedBits(ICI->getOperand(0), KnownZero, KnownOne); 544 545 APInt KnownZeroMask(~KnownZero); 546 if (KnownZeroMask.isPowerOf2()) { // Exactly 1 possible 1? 547 if (!DoXform) return ICI; 548 549 bool isNE = ICI->getPredicate() == ICmpInst::ICMP_NE; 550 if (Op1CV != 0 && (Op1CV != KnownZeroMask)) { 551 // (X&4) == 2 --> false 552 // (X&4) != 2 --> true 553 Constant *Res = ConstantInt::get(Type::getInt1Ty(CI.getContext()), 554 isNE); 555 Res = ConstantExpr::getZExt(Res, CI.getType()); 556 return ReplaceInstUsesWith(CI, Res); 557 } 558 559 uint32_t ShiftAmt = KnownZeroMask.logBase2(); 560 Value *In = ICI->getOperand(0); 561 if (ShiftAmt) { 562 // Perform a logical shr by shiftamt. 563 // Insert the shift to put the result in the low bit. 564 In = Builder->CreateLShr(In, ConstantInt::get(In->getType(),ShiftAmt), 565 In->getName()+".lobit"); 566 } 567 568 if ((Op1CV != 0) == isNE) { // Toggle the low bit. 569 Constant *One = ConstantInt::get(In->getType(), 1); 570 In = Builder->CreateXor(In, One); 571 } 572 573 if (CI.getType() == In->getType()) 574 return ReplaceInstUsesWith(CI, In); 575 return CastInst::CreateIntegerCast(In, CI.getType(), false/*ZExt*/); 576 } 577 } 578 } 579 580 // icmp ne A, B is equal to xor A, B when A and B only really have one bit. 581 // It is also profitable to transform icmp eq into not(xor(A, B)) because that 582 // may lead to additional simplifications. 583 if (ICI->isEquality() && CI.getType() == ICI->getOperand(0)->getType()) { 584 if (IntegerType *ITy = dyn_cast<IntegerType>(CI.getType())) { 585 uint32_t BitWidth = ITy->getBitWidth(); 586 Value *LHS = ICI->getOperand(0); 587 Value *RHS = ICI->getOperand(1); 588 589 APInt KnownZeroLHS(BitWidth, 0), KnownOneLHS(BitWidth, 0); 590 APInt KnownZeroRHS(BitWidth, 0), KnownOneRHS(BitWidth, 0); 591 ComputeMaskedBits(LHS, KnownZeroLHS, KnownOneLHS); 592 ComputeMaskedBits(RHS, KnownZeroRHS, KnownOneRHS); 593 594 if (KnownZeroLHS == KnownZeroRHS && KnownOneLHS == KnownOneRHS) { 595 APInt KnownBits = KnownZeroLHS | KnownOneLHS; 596 APInt UnknownBit = ~KnownBits; 597 if (UnknownBit.countPopulation() == 1) { 598 if (!DoXform) return ICI; 599 600 Value *Result = Builder->CreateXor(LHS, RHS); 601 602 // Mask off any bits that are set and won't be shifted away. 603 if (KnownOneLHS.uge(UnknownBit)) 604 Result = Builder->CreateAnd(Result, 605 ConstantInt::get(ITy, UnknownBit)); 606 607 // Shift the bit we're testing down to the lsb. 608 Result = Builder->CreateLShr( 609 Result, ConstantInt::get(ITy, UnknownBit.countTrailingZeros())); 610 611 if (ICI->getPredicate() == ICmpInst::ICMP_EQ) 612 Result = Builder->CreateXor(Result, ConstantInt::get(ITy, 1)); 613 Result->takeName(ICI); 614 return ReplaceInstUsesWith(CI, Result); 615 } 616 } 617 } 618 } 619 620 return 0; 621} 622 623/// CanEvaluateZExtd - Determine if the specified value can be computed in the 624/// specified wider type and produce the same low bits. If not, return false. 625/// 626/// If this function returns true, it can also return a non-zero number of bits 627/// (in BitsToClear) which indicates that the value it computes is correct for 628/// the zero extend, but that the additional BitsToClear bits need to be zero'd 629/// out. For example, to promote something like: 630/// 631/// %B = trunc i64 %A to i32 632/// %C = lshr i32 %B, 8 633/// %E = zext i32 %C to i64 634/// 635/// CanEvaluateZExtd for the 'lshr' will return true, and BitsToClear will be 636/// set to 8 to indicate that the promoted value needs to have bits 24-31 637/// cleared in addition to bits 32-63. Since an 'and' will be generated to 638/// clear the top bits anyway, doing this has no extra cost. 639/// 640/// This function works on both vectors and scalars. 641static bool CanEvaluateZExtd(Value *V, Type *Ty, unsigned &BitsToClear) { 642 BitsToClear = 0; 643 if (isa<Constant>(V)) 644 return true; 645 646 Instruction *I = dyn_cast<Instruction>(V); 647 if (!I) return false; 648 649 // If the input is a truncate from the destination type, we can trivially 650 // eliminate it. 651 if (isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty) 652 return true; 653 654 // We can't extend or shrink something that has multiple uses: doing so would 655 // require duplicating the instruction in general, which isn't profitable. 656 if (!I->hasOneUse()) return false; 657 658 unsigned Opc = I->getOpcode(), Tmp; 659 switch (Opc) { 660 case Instruction::ZExt: // zext(zext(x)) -> zext(x). 661 case Instruction::SExt: // zext(sext(x)) -> sext(x). 662 case Instruction::Trunc: // zext(trunc(x)) -> trunc(x) or zext(x) 663 return true; 664 case Instruction::And: 665 case Instruction::Or: 666 case Instruction::Xor: 667 case Instruction::Add: 668 case Instruction::Sub: 669 case Instruction::Mul: 670 case Instruction::Shl: 671 if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear) || 672 !CanEvaluateZExtd(I->getOperand(1), Ty, Tmp)) 673 return false; 674 // These can all be promoted if neither operand has 'bits to clear'. 675 if (BitsToClear == 0 && Tmp == 0) 676 return true; 677 678 // If the operation is an AND/OR/XOR and the bits to clear are zero in the 679 // other side, BitsToClear is ok. 680 if (Tmp == 0 && 681 (Opc == Instruction::And || Opc == Instruction::Or || 682 Opc == Instruction::Xor)) { 683 // We use MaskedValueIsZero here for generality, but the case we care 684 // about the most is constant RHS. 685 unsigned VSize = V->getType()->getScalarSizeInBits(); 686 if (MaskedValueIsZero(I->getOperand(1), 687 APInt::getHighBitsSet(VSize, BitsToClear))) 688 return true; 689 } 690 691 // Otherwise, we don't know how to analyze this BitsToClear case yet. 692 return false; 693 694 case Instruction::LShr: 695 // We can promote lshr(x, cst) if we can promote x. This requires the 696 // ultimate 'and' to clear out the high zero bits we're clearing out though. 697 if (ConstantInt *Amt = dyn_cast<ConstantInt>(I->getOperand(1))) { 698 if (!CanEvaluateZExtd(I->getOperand(0), Ty, BitsToClear)) 699 return false; 700 BitsToClear += Amt->getZExtValue(); 701 if (BitsToClear > V->getType()->getScalarSizeInBits()) 702 BitsToClear = V->getType()->getScalarSizeInBits(); 703 return true; 704 } 705 // Cannot promote variable LSHR. 706 return false; 707 case Instruction::Select: 708 if (!CanEvaluateZExtd(I->getOperand(1), Ty, Tmp) || 709 !CanEvaluateZExtd(I->getOperand(2), Ty, BitsToClear) || 710 // TODO: If important, we could handle the case when the BitsToClear are 711 // known zero in the disagreeing side. 712 Tmp != BitsToClear) 713 return false; 714 return true; 715 716 case Instruction::PHI: { 717 // We can change a phi if we can change all operands. Note that we never 718 // get into trouble with cyclic PHIs here because we only consider 719 // instructions with a single use. 720 PHINode *PN = cast<PHINode>(I); 721 if (!CanEvaluateZExtd(PN->getIncomingValue(0), Ty, BitsToClear)) 722 return false; 723 for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) 724 if (!CanEvaluateZExtd(PN->getIncomingValue(i), Ty, Tmp) || 725 // TODO: If important, we could handle the case when the BitsToClear 726 // are known zero in the disagreeing input. 727 Tmp != BitsToClear) 728 return false; 729 return true; 730 } 731 default: 732 // TODO: Can handle more cases here. 733 return false; 734 } 735} 736 737Instruction *InstCombiner::visitZExt(ZExtInst &CI) { 738 // If this zero extend is only used by a truncate, let the truncate by 739 // eliminated before we try to optimize this zext. 740 if (CI.hasOneUse() && isa<TruncInst>(CI.use_back())) 741 return 0; 742 743 // If one of the common conversion will work, do it. 744 if (Instruction *Result = commonCastTransforms(CI)) 745 return Result; 746 747 // See if we can simplify any instructions used by the input whose sole 748 // purpose is to compute bits we don't care about. 749 if (SimplifyDemandedInstructionBits(CI)) 750 return &CI; 751 752 Value *Src = CI.getOperand(0); 753 Type *SrcTy = Src->getType(), *DestTy = CI.getType(); 754 755 // Attempt to extend the entire input expression tree to the destination 756 // type. Only do this if the dest type is a simple type, don't convert the 757 // expression tree to something weird like i93 unless the source is also 758 // strange. 759 unsigned BitsToClear; 760 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && 761 CanEvaluateZExtd(Src, DestTy, BitsToClear)) { 762 assert(BitsToClear < SrcTy->getScalarSizeInBits() && 763 "Unreasonable BitsToClear"); 764 765 // Okay, we can transform this! Insert the new expression now. 766 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" 767 " to avoid zero extend: " << CI); 768 Value *Res = EvaluateInDifferentType(Src, DestTy, false); 769 assert(Res->getType() == DestTy); 770 771 uint32_t SrcBitsKept = SrcTy->getScalarSizeInBits()-BitsToClear; 772 uint32_t DestBitSize = DestTy->getScalarSizeInBits(); 773 774 // If the high bits are already filled with zeros, just replace this 775 // cast with the result. 776 if (MaskedValueIsZero(Res, APInt::getHighBitsSet(DestBitSize, 777 DestBitSize-SrcBitsKept))) 778 return ReplaceInstUsesWith(CI, Res); 779 780 // We need to emit an AND to clear the high bits. 781 Constant *C = ConstantInt::get(Res->getType(), 782 APInt::getLowBitsSet(DestBitSize, SrcBitsKept)); 783 return BinaryOperator::CreateAnd(Res, C); 784 } 785 786 // If this is a TRUNC followed by a ZEXT then we are dealing with integral 787 // types and if the sizes are just right we can convert this into a logical 788 // 'and' which will be much cheaper than the pair of casts. 789 if (TruncInst *CSrc = dyn_cast<TruncInst>(Src)) { // A->B->C cast 790 // TODO: Subsume this into EvaluateInDifferentType. 791 792 // Get the sizes of the types involved. We know that the intermediate type 793 // will be smaller than A or C, but don't know the relation between A and C. 794 Value *A = CSrc->getOperand(0); 795 unsigned SrcSize = A->getType()->getScalarSizeInBits(); 796 unsigned MidSize = CSrc->getType()->getScalarSizeInBits(); 797 unsigned DstSize = CI.getType()->getScalarSizeInBits(); 798 // If we're actually extending zero bits, then if 799 // SrcSize < DstSize: zext(a & mask) 800 // SrcSize == DstSize: a & mask 801 // SrcSize > DstSize: trunc(a) & mask 802 if (SrcSize < DstSize) { 803 APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize)); 804 Constant *AndConst = ConstantInt::get(A->getType(), AndValue); 805 Value *And = Builder->CreateAnd(A, AndConst, CSrc->getName()+".mask"); 806 return new ZExtInst(And, CI.getType()); 807 } 808 809 if (SrcSize == DstSize) { 810 APInt AndValue(APInt::getLowBitsSet(SrcSize, MidSize)); 811 return BinaryOperator::CreateAnd(A, ConstantInt::get(A->getType(), 812 AndValue)); 813 } 814 if (SrcSize > DstSize) { 815 Value *Trunc = Builder->CreateTrunc(A, CI.getType()); 816 APInt AndValue(APInt::getLowBitsSet(DstSize, MidSize)); 817 return BinaryOperator::CreateAnd(Trunc, 818 ConstantInt::get(Trunc->getType(), 819 AndValue)); 820 } 821 } 822 823 if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) 824 return transformZExtICmp(ICI, CI); 825 826 BinaryOperator *SrcI = dyn_cast<BinaryOperator>(Src); 827 if (SrcI && SrcI->getOpcode() == Instruction::Or) { 828 // zext (or icmp, icmp) --> or (zext icmp), (zext icmp) if at least one 829 // of the (zext icmp) will be transformed. 830 ICmpInst *LHS = dyn_cast<ICmpInst>(SrcI->getOperand(0)); 831 ICmpInst *RHS = dyn_cast<ICmpInst>(SrcI->getOperand(1)); 832 if (LHS && RHS && LHS->hasOneUse() && RHS->hasOneUse() && 833 (transformZExtICmp(LHS, CI, false) || 834 transformZExtICmp(RHS, CI, false))) { 835 Value *LCast = Builder->CreateZExt(LHS, CI.getType(), LHS->getName()); 836 Value *RCast = Builder->CreateZExt(RHS, CI.getType(), RHS->getName()); 837 return BinaryOperator::Create(Instruction::Or, LCast, RCast); 838 } 839 } 840 841 // zext(trunc(t) & C) -> (t & zext(C)). 842 if (SrcI && SrcI->getOpcode() == Instruction::And && SrcI->hasOneUse()) 843 if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1))) 844 if (TruncInst *TI = dyn_cast<TruncInst>(SrcI->getOperand(0))) { 845 Value *TI0 = TI->getOperand(0); 846 if (TI0->getType() == CI.getType()) 847 return 848 BinaryOperator::CreateAnd(TI0, 849 ConstantExpr::getZExt(C, CI.getType())); 850 } 851 852 // zext((trunc(t) & C) ^ C) -> ((t & zext(C)) ^ zext(C)). 853 if (SrcI && SrcI->getOpcode() == Instruction::Xor && SrcI->hasOneUse()) 854 if (ConstantInt *C = dyn_cast<ConstantInt>(SrcI->getOperand(1))) 855 if (BinaryOperator *And = dyn_cast<BinaryOperator>(SrcI->getOperand(0))) 856 if (And->getOpcode() == Instruction::And && And->hasOneUse() && 857 And->getOperand(1) == C) 858 if (TruncInst *TI = dyn_cast<TruncInst>(And->getOperand(0))) { 859 Value *TI0 = TI->getOperand(0); 860 if (TI0->getType() == CI.getType()) { 861 Constant *ZC = ConstantExpr::getZExt(C, CI.getType()); 862 Value *NewAnd = Builder->CreateAnd(TI0, ZC); 863 return BinaryOperator::CreateXor(NewAnd, ZC); 864 } 865 } 866 867 // zext (xor i1 X, true) to i32 --> xor (zext i1 X to i32), 1 868 Value *X; 869 if (SrcI && SrcI->hasOneUse() && SrcI->getType()->isIntegerTy(1) && 870 match(SrcI, m_Not(m_Value(X))) && 871 (!X->hasOneUse() || !isa<CmpInst>(X))) { 872 Value *New = Builder->CreateZExt(X, CI.getType()); 873 return BinaryOperator::CreateXor(New, ConstantInt::get(CI.getType(), 1)); 874 } 875 876 return 0; 877} 878 879/// transformSExtICmp - Transform (sext icmp) to bitwise / integer operations 880/// in order to eliminate the icmp. 881Instruction *InstCombiner::transformSExtICmp(ICmpInst *ICI, Instruction &CI) { 882 Value *Op0 = ICI->getOperand(0), *Op1 = ICI->getOperand(1); 883 ICmpInst::Predicate Pred = ICI->getPredicate(); 884 885 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) { 886 // (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if negative 887 // (x >s -1) ? -1 : 0 -> not (ashr x, 31) -> all ones if positive 888 if ((Pred == ICmpInst::ICMP_SLT && Op1C->isZero()) || 889 (Pred == ICmpInst::ICMP_SGT && Op1C->isAllOnesValue())) { 890 891 Value *Sh = ConstantInt::get(Op0->getType(), 892 Op0->getType()->getScalarSizeInBits()-1); 893 Value *In = Builder->CreateAShr(Op0, Sh, Op0->getName()+".lobit"); 894 if (In->getType() != CI.getType()) 895 In = Builder->CreateIntCast(In, CI.getType(), true/*SExt*/); 896 897 if (Pred == ICmpInst::ICMP_SGT) 898 In = Builder->CreateNot(In, In->getName()+".not"); 899 return ReplaceInstUsesWith(CI, In); 900 } 901 902 // If we know that only one bit of the LHS of the icmp can be set and we 903 // have an equality comparison with zero or a power of 2, we can transform 904 // the icmp and sext into bitwise/integer operations. 905 if (ICI->hasOneUse() && 906 ICI->isEquality() && (Op1C->isZero() || Op1C->getValue().isPowerOf2())){ 907 unsigned BitWidth = Op1C->getType()->getBitWidth(); 908 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); 909 ComputeMaskedBits(Op0, KnownZero, KnownOne); 910 911 APInt KnownZeroMask(~KnownZero); 912 if (KnownZeroMask.isPowerOf2()) { 913 Value *In = ICI->getOperand(0); 914 915 // If the icmp tests for a known zero bit we can constant fold it. 916 if (!Op1C->isZero() && Op1C->getValue() != KnownZeroMask) { 917 Value *V = Pred == ICmpInst::ICMP_NE ? 918 ConstantInt::getAllOnesValue(CI.getType()) : 919 ConstantInt::getNullValue(CI.getType()); 920 return ReplaceInstUsesWith(CI, V); 921 } 922 923 if (!Op1C->isZero() == (Pred == ICmpInst::ICMP_NE)) { 924 // sext ((x & 2^n) == 0) -> (x >> n) - 1 925 // sext ((x & 2^n) != 2^n) -> (x >> n) - 1 926 unsigned ShiftAmt = KnownZeroMask.countTrailingZeros(); 927 // Perform a right shift to place the desired bit in the LSB. 928 if (ShiftAmt) 929 In = Builder->CreateLShr(In, 930 ConstantInt::get(In->getType(), ShiftAmt)); 931 932 // At this point "In" is either 1 or 0. Subtract 1 to turn 933 // {1, 0} -> {0, -1}. 934 In = Builder->CreateAdd(In, 935 ConstantInt::getAllOnesValue(In->getType()), 936 "sext"); 937 } else { 938 // sext ((x & 2^n) != 0) -> (x << bitwidth-n) a>> bitwidth-1 939 // sext ((x & 2^n) == 2^n) -> (x << bitwidth-n) a>> bitwidth-1 940 unsigned ShiftAmt = KnownZeroMask.countLeadingZeros(); 941 // Perform a left shift to place the desired bit in the MSB. 942 if (ShiftAmt) 943 In = Builder->CreateShl(In, 944 ConstantInt::get(In->getType(), ShiftAmt)); 945 946 // Distribute the bit over the whole bit width. 947 In = Builder->CreateAShr(In, ConstantInt::get(In->getType(), 948 BitWidth - 1), "sext"); 949 } 950 951 if (CI.getType() == In->getType()) 952 return ReplaceInstUsesWith(CI, In); 953 return CastInst::CreateIntegerCast(In, CI.getType(), true/*SExt*/); 954 } 955 } 956 } 957 958 // vector (x <s 0) ? -1 : 0 -> ashr x, 31 -> all ones if signed. 959 if (VectorType *VTy = dyn_cast<VectorType>(CI.getType())) { 960 if (Pred == ICmpInst::ICMP_SLT && match(Op1, m_Zero()) && 961 Op0->getType() == CI.getType()) { 962 Type *EltTy = VTy->getElementType(); 963 964 // splat the shift constant to a constant vector. 965 Constant *VSh = ConstantInt::get(VTy, EltTy->getScalarSizeInBits()-1); 966 Value *In = Builder->CreateAShr(Op0, VSh, Op0->getName()+".lobit"); 967 return ReplaceInstUsesWith(CI, In); 968 } 969 } 970 971 return 0; 972} 973 974/// CanEvaluateSExtd - Return true if we can take the specified value 975/// and return it as type Ty without inserting any new casts and without 976/// changing the value of the common low bits. This is used by code that tries 977/// to promote integer operations to a wider types will allow us to eliminate 978/// the extension. 979/// 980/// This function works on both vectors and scalars. 981/// 982static bool CanEvaluateSExtd(Value *V, Type *Ty) { 983 assert(V->getType()->getScalarSizeInBits() < Ty->getScalarSizeInBits() && 984 "Can't sign extend type to a smaller type"); 985 // If this is a constant, it can be trivially promoted. 986 if (isa<Constant>(V)) 987 return true; 988 989 Instruction *I = dyn_cast<Instruction>(V); 990 if (!I) return false; 991 992 // If this is a truncate from the dest type, we can trivially eliminate it. 993 if (isa<TruncInst>(I) && I->getOperand(0)->getType() == Ty) 994 return true; 995 996 // We can't extend or shrink something that has multiple uses: doing so would 997 // require duplicating the instruction in general, which isn't profitable. 998 if (!I->hasOneUse()) return false; 999 1000 switch (I->getOpcode()) { 1001 case Instruction::SExt: // sext(sext(x)) -> sext(x) 1002 case Instruction::ZExt: // sext(zext(x)) -> zext(x) 1003 case Instruction::Trunc: // sext(trunc(x)) -> trunc(x) or sext(x) 1004 return true; 1005 case Instruction::And: 1006 case Instruction::Or: 1007 case Instruction::Xor: 1008 case Instruction::Add: 1009 case Instruction::Sub: 1010 case Instruction::Mul: 1011 // These operators can all arbitrarily be extended if their inputs can. 1012 return CanEvaluateSExtd(I->getOperand(0), Ty) && 1013 CanEvaluateSExtd(I->getOperand(1), Ty); 1014 1015 //case Instruction::Shl: TODO 1016 //case Instruction::LShr: TODO 1017 1018 case Instruction::Select: 1019 return CanEvaluateSExtd(I->getOperand(1), Ty) && 1020 CanEvaluateSExtd(I->getOperand(2), Ty); 1021 1022 case Instruction::PHI: { 1023 // We can change a phi if we can change all operands. Note that we never 1024 // get into trouble with cyclic PHIs here because we only consider 1025 // instructions with a single use. 1026 PHINode *PN = cast<PHINode>(I); 1027 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) 1028 if (!CanEvaluateSExtd(PN->getIncomingValue(i), Ty)) return false; 1029 return true; 1030 } 1031 default: 1032 // TODO: Can handle more cases here. 1033 break; 1034 } 1035 1036 return false; 1037} 1038 1039Instruction *InstCombiner::visitSExt(SExtInst &CI) { 1040 // If this sign extend is only used by a truncate, let the truncate by 1041 // eliminated before we try to optimize this zext. 1042 if (CI.hasOneUse() && isa<TruncInst>(CI.use_back())) 1043 return 0; 1044 1045 if (Instruction *I = commonCastTransforms(CI)) 1046 return I; 1047 1048 // See if we can simplify any instructions used by the input whose sole 1049 // purpose is to compute bits we don't care about. 1050 if (SimplifyDemandedInstructionBits(CI)) 1051 return &CI; 1052 1053 Value *Src = CI.getOperand(0); 1054 Type *SrcTy = Src->getType(), *DestTy = CI.getType(); 1055 1056 // Attempt to extend the entire input expression tree to the destination 1057 // type. Only do this if the dest type is a simple type, don't convert the 1058 // expression tree to something weird like i93 unless the source is also 1059 // strange. 1060 if ((DestTy->isVectorTy() || ShouldChangeType(SrcTy, DestTy)) && 1061 CanEvaluateSExtd(Src, DestTy)) { 1062 // Okay, we can transform this! Insert the new expression now. 1063 DEBUG(dbgs() << "ICE: EvaluateInDifferentType converting expression type" 1064 " to avoid sign extend: " << CI); 1065 Value *Res = EvaluateInDifferentType(Src, DestTy, true); 1066 assert(Res->getType() == DestTy); 1067 1068 uint32_t SrcBitSize = SrcTy->getScalarSizeInBits(); 1069 uint32_t DestBitSize = DestTy->getScalarSizeInBits(); 1070 1071 // If the high bits are already filled with sign bit, just replace this 1072 // cast with the result. 1073 if (ComputeNumSignBits(Res) > DestBitSize - SrcBitSize) 1074 return ReplaceInstUsesWith(CI, Res); 1075 1076 // We need to emit a shl + ashr to do the sign extend. 1077 Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize); 1078 return BinaryOperator::CreateAShr(Builder->CreateShl(Res, ShAmt, "sext"), 1079 ShAmt); 1080 } 1081 1082 // If this input is a trunc from our destination, then turn sext(trunc(x)) 1083 // into shifts. 1084 if (TruncInst *TI = dyn_cast<TruncInst>(Src)) 1085 if (TI->hasOneUse() && TI->getOperand(0)->getType() == DestTy) { 1086 uint32_t SrcBitSize = SrcTy->getScalarSizeInBits(); 1087 uint32_t DestBitSize = DestTy->getScalarSizeInBits(); 1088 1089 // We need to emit a shl + ashr to do the sign extend. 1090 Value *ShAmt = ConstantInt::get(DestTy, DestBitSize-SrcBitSize); 1091 Value *Res = Builder->CreateShl(TI->getOperand(0), ShAmt, "sext"); 1092 return BinaryOperator::CreateAShr(Res, ShAmt); 1093 } 1094 1095 if (ICmpInst *ICI = dyn_cast<ICmpInst>(Src)) 1096 return transformSExtICmp(ICI, CI); 1097 1098 // If the input is a shl/ashr pair of a same constant, then this is a sign 1099 // extension from a smaller value. If we could trust arbitrary bitwidth 1100 // integers, we could turn this into a truncate to the smaller bit and then 1101 // use a sext for the whole extension. Since we don't, look deeper and check 1102 // for a truncate. If the source and dest are the same type, eliminate the 1103 // trunc and extend and just do shifts. For example, turn: 1104 // %a = trunc i32 %i to i8 1105 // %b = shl i8 %a, 6 1106 // %c = ashr i8 %b, 6 1107 // %d = sext i8 %c to i32 1108 // into: 1109 // %a = shl i32 %i, 30 1110 // %d = ashr i32 %a, 30 1111 Value *A = 0; 1112 // TODO: Eventually this could be subsumed by EvaluateInDifferentType. 1113 ConstantInt *BA = 0, *CA = 0; 1114 if (match(Src, m_AShr(m_Shl(m_Trunc(m_Value(A)), m_ConstantInt(BA)), 1115 m_ConstantInt(CA))) && 1116 BA == CA && A->getType() == CI.getType()) { 1117 unsigned MidSize = Src->getType()->getScalarSizeInBits(); 1118 unsigned SrcDstSize = CI.getType()->getScalarSizeInBits(); 1119 unsigned ShAmt = CA->getZExtValue()+SrcDstSize-MidSize; 1120 Constant *ShAmtV = ConstantInt::get(CI.getType(), ShAmt); 1121 A = Builder->CreateShl(A, ShAmtV, CI.getName()); 1122 return BinaryOperator::CreateAShr(A, ShAmtV); 1123 } 1124 1125 return 0; 1126} 1127 1128 1129/// FitsInFPType - Return a Constant* for the specified FP constant if it fits 1130/// in the specified FP type without changing its value. 1131static Constant *FitsInFPType(ConstantFP *CFP, const fltSemantics &Sem) { 1132 bool losesInfo; 1133 APFloat F = CFP->getValueAPF(); 1134 (void)F.convert(Sem, APFloat::rmNearestTiesToEven, &losesInfo); 1135 if (!losesInfo) 1136 return ConstantFP::get(CFP->getContext(), F); 1137 return 0; 1138} 1139 1140/// LookThroughFPExtensions - If this is an fp extension instruction, look 1141/// through it until we get the source value. 1142static Value *LookThroughFPExtensions(Value *V) { 1143 if (Instruction *I = dyn_cast<Instruction>(V)) 1144 if (I->getOpcode() == Instruction::FPExt) 1145 return LookThroughFPExtensions(I->getOperand(0)); 1146 1147 // If this value is a constant, return the constant in the smallest FP type 1148 // that can accurately represent it. This allows us to turn 1149 // (float)((double)X+2.0) into x+2.0f. 1150 if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) { 1151 if (CFP->getType() == Type::getPPC_FP128Ty(V->getContext())) 1152 return V; // No constant folding of this. 1153 // See if the value can be truncated to half and then reextended. 1154 if (Value *V = FitsInFPType(CFP, APFloat::IEEEhalf)) 1155 return V; 1156 // See if the value can be truncated to float and then reextended. 1157 if (Value *V = FitsInFPType(CFP, APFloat::IEEEsingle)) 1158 return V; 1159 if (CFP->getType()->isDoubleTy()) 1160 return V; // Won't shrink. 1161 if (Value *V = FitsInFPType(CFP, APFloat::IEEEdouble)) 1162 return V; 1163 // Don't try to shrink to various long double types. 1164 } 1165 1166 return V; 1167} 1168 1169Instruction *InstCombiner::visitFPTrunc(FPTruncInst &CI) { 1170 if (Instruction *I = commonCastTransforms(CI)) 1171 return I; 1172 1173 // If we have fptrunc(fadd (fpextend x), (fpextend y)), where x and y are 1174 // smaller than the destination type, we can eliminate the truncate by doing 1175 // the add as the smaller type. This applies to fadd/fsub/fmul/fdiv as well 1176 // as many builtins (sqrt, etc). 1177 BinaryOperator *OpI = dyn_cast<BinaryOperator>(CI.getOperand(0)); 1178 if (OpI && OpI->hasOneUse()) { 1179 switch (OpI->getOpcode()) { 1180 default: break; 1181 case Instruction::FAdd: 1182 case Instruction::FSub: 1183 case Instruction::FMul: 1184 case Instruction::FDiv: 1185 case Instruction::FRem: 1186 Type *SrcTy = OpI->getType(); 1187 Value *LHSTrunc = LookThroughFPExtensions(OpI->getOperand(0)); 1188 Value *RHSTrunc = LookThroughFPExtensions(OpI->getOperand(1)); 1189 if (LHSTrunc->getType() != SrcTy && 1190 RHSTrunc->getType() != SrcTy) { 1191 unsigned DstSize = CI.getType()->getScalarSizeInBits(); 1192 // If the source types were both smaller than the destination type of 1193 // the cast, do this xform. 1194 if (LHSTrunc->getType()->getScalarSizeInBits() <= DstSize && 1195 RHSTrunc->getType()->getScalarSizeInBits() <= DstSize) { 1196 LHSTrunc = Builder->CreateFPExt(LHSTrunc, CI.getType()); 1197 RHSTrunc = Builder->CreateFPExt(RHSTrunc, CI.getType()); 1198 return BinaryOperator::Create(OpI->getOpcode(), LHSTrunc, RHSTrunc); 1199 } 1200 } 1201 break; 1202 } 1203 } 1204 1205 // Fold (fptrunc (sqrt (fpext x))) -> (sqrtf x) 1206 CallInst *Call = dyn_cast<CallInst>(CI.getOperand(0)); 1207 if (Call && Call->getCalledFunction() && TLI->has(LibFunc::sqrtf) && 1208 Call->getCalledFunction()->getName() == TLI->getName(LibFunc::sqrt) && 1209 Call->getNumArgOperands() == 1 && 1210 Call->hasOneUse()) { 1211 CastInst *Arg = dyn_cast<CastInst>(Call->getArgOperand(0)); 1212 if (Arg && Arg->getOpcode() == Instruction::FPExt && 1213 CI.getType()->isFloatTy() && 1214 Call->getType()->isDoubleTy() && 1215 Arg->getType()->isDoubleTy() && 1216 Arg->getOperand(0)->getType()->isFloatTy()) { 1217 Function *Callee = Call->getCalledFunction(); 1218 Module *M = CI.getParent()->getParent()->getParent(); 1219 Constant *SqrtfFunc = M->getOrInsertFunction("sqrtf", 1220 Callee->getAttributes(), 1221 Builder->getFloatTy(), 1222 Builder->getFloatTy(), 1223 NULL); 1224 CallInst *ret = CallInst::Create(SqrtfFunc, Arg->getOperand(0), 1225 "sqrtfcall"); 1226 ret->setAttributes(Callee->getAttributes()); 1227 1228 1229 // Remove the old Call. With -fmath-errno, it won't get marked readnone. 1230 ReplaceInstUsesWith(*Call, UndefValue::get(Call->getType())); 1231 EraseInstFromFunction(*Call); 1232 return ret; 1233 } 1234 } 1235 1236 return 0; 1237} 1238 1239Instruction *InstCombiner::visitFPExt(CastInst &CI) { 1240 return commonCastTransforms(CI); 1241} 1242 1243Instruction *InstCombiner::visitFPToUI(FPToUIInst &FI) { 1244 Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0)); 1245 if (OpI == 0) 1246 return commonCastTransforms(FI); 1247 1248 // fptoui(uitofp(X)) --> X 1249 // fptoui(sitofp(X)) --> X 1250 // This is safe if the intermediate type has enough bits in its mantissa to 1251 // accurately represent all values of X. For example, do not do this with 1252 // i64->float->i64. This is also safe for sitofp case, because any negative 1253 // 'X' value would cause an undefined result for the fptoui. 1254 if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) && 1255 OpI->getOperand(0)->getType() == FI.getType() && 1256 (int)FI.getType()->getScalarSizeInBits() < /*extra bit for sign */ 1257 OpI->getType()->getFPMantissaWidth()) 1258 return ReplaceInstUsesWith(FI, OpI->getOperand(0)); 1259 1260 return commonCastTransforms(FI); 1261} 1262 1263Instruction *InstCombiner::visitFPToSI(FPToSIInst &FI) { 1264 Instruction *OpI = dyn_cast<Instruction>(FI.getOperand(0)); 1265 if (OpI == 0) 1266 return commonCastTransforms(FI); 1267 1268 // fptosi(sitofp(X)) --> X 1269 // fptosi(uitofp(X)) --> X 1270 // This is safe if the intermediate type has enough bits in its mantissa to 1271 // accurately represent all values of X. For example, do not do this with 1272 // i64->float->i64. This is also safe for sitofp case, because any negative 1273 // 'X' value would cause an undefined result for the fptoui. 1274 if ((isa<UIToFPInst>(OpI) || isa<SIToFPInst>(OpI)) && 1275 OpI->getOperand(0)->getType() == FI.getType() && 1276 (int)FI.getType()->getScalarSizeInBits() <= 1277 OpI->getType()->getFPMantissaWidth()) 1278 return ReplaceInstUsesWith(FI, OpI->getOperand(0)); 1279 1280 return commonCastTransforms(FI); 1281} 1282 1283Instruction *InstCombiner::visitUIToFP(CastInst &CI) { 1284 return commonCastTransforms(CI); 1285} 1286 1287Instruction *InstCombiner::visitSIToFP(CastInst &CI) { 1288 return commonCastTransforms(CI); 1289} 1290 1291Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) { 1292 // If the source integer type is not the intptr_t type for this target, do a 1293 // trunc or zext to the intptr_t type, then inttoptr of it. This allows the 1294 // cast to be exposed to other transforms. 1295 unsigned AS = CI.getAddressSpace(); 1296 if (TD) { 1297 if (CI.getOperand(0)->getType()->getScalarSizeInBits() > 1298 TD->getPointerSizeInBits(AS)) { 1299 Value *P = Builder->CreateTrunc(CI.getOperand(0), 1300 TD->getIntPtrType(CI.getType())); 1301 return new IntToPtrInst(P, CI.getType()); 1302 } 1303 if (CI.getOperand(0)->getType()->getScalarSizeInBits() < 1304 TD->getPointerSizeInBits(AS)) { 1305 Value *P = Builder->CreateZExt(CI.getOperand(0), 1306 TD->getIntPtrType(CI.getType())); 1307 return new IntToPtrInst(P, CI.getType()); 1308 } 1309 } 1310 1311 if (Instruction *I = commonCastTransforms(CI)) 1312 return I; 1313 1314 return 0; 1315} 1316 1317/// @brief Implement the transforms for cast of pointer (bitcast/ptrtoint) 1318Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) { 1319 Value *Src = CI.getOperand(0); 1320 1321 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Src)) { 1322 // If casting the result of a getelementptr instruction with no offset, turn 1323 // this into a cast of the original pointer! 1324 if (GEP->hasAllZeroIndices()) { 1325 // Changing the cast operand is usually not a good idea but it is safe 1326 // here because the pointer operand is being replaced with another 1327 // pointer operand so the opcode doesn't need to change. 1328 Worklist.Add(GEP); 1329 CI.setOperand(0, GEP->getOperand(0)); 1330 return &CI; 1331 } 1332 1333 // If the GEP has a single use, and the base pointer is a bitcast, and the 1334 // GEP computes a constant offset, see if we can convert these three 1335 // instructions into fewer. This typically happens with unions and other 1336 // non-type-safe code. 1337 if (TD && GEP->hasOneUse() && isa<BitCastInst>(GEP->getOperand(0)) && 1338 GEP->hasAllConstantIndices()) { 1339 SmallVector<Value*, 8> Ops(GEP->idx_begin(), GEP->idx_end()); 1340 int64_t Offset = TD->getIndexedOffset(GEP->getPointerOperandType(), Ops); 1341 1342 // Get the base pointer input of the bitcast, and the type it points to. 1343 Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0); 1344 Type *GEPIdxTy = 1345 cast<PointerType>(OrigBase->getType())->getElementType(); 1346 SmallVector<Value*, 8> NewIndices; 1347 Type *IntPtrTy = TD->getIntPtrType(OrigBase->getType()); 1348 if (FindElementAtOffset(GEPIdxTy, Offset, IntPtrTy, NewIndices)) { 1349 // If we were able to index down into an element, create the GEP 1350 // and bitcast the result. This eliminates one bitcast, potentially 1351 // two. 1352 Value *NGEP = cast<GEPOperator>(GEP)->isInBounds() ? 1353 Builder->CreateInBoundsGEP(OrigBase, NewIndices) : 1354 Builder->CreateGEP(OrigBase, NewIndices); 1355 NGEP->takeName(GEP); 1356 1357 if (isa<BitCastInst>(CI)) 1358 return new BitCastInst(NGEP, CI.getType()); 1359 assert(isa<PtrToIntInst>(CI)); 1360 return new PtrToIntInst(NGEP, CI.getType()); 1361 } 1362 } 1363 } 1364 1365 return commonCastTransforms(CI); 1366} 1367 1368Instruction *InstCombiner::visitPtrToInt(PtrToIntInst &CI) { 1369 // If the destination integer type is not the intptr_t type for this target, 1370 // do a ptrtoint to intptr_t then do a trunc or zext. This allows the cast 1371 // to be exposed to other transforms. 1372 unsigned AS = CI.getPointerAddressSpace(); 1373 if (TD) { 1374 if (CI.getType()->getScalarSizeInBits() < TD->getPointerSizeInBits(AS)) { 1375 Value *P = Builder->CreatePtrToInt(CI.getOperand(0), 1376 TD->getIntPtrType(CI.getContext(), AS)); 1377 return new TruncInst(P, CI.getType()); 1378 } 1379 if (CI.getType()->getScalarSizeInBits() > TD->getPointerSizeInBits(AS)) { 1380 Value *P = Builder->CreatePtrToInt(CI.getOperand(0), 1381 TD->getIntPtrType(CI.getContext(), AS)); 1382 return new ZExtInst(P, CI.getType()); 1383 } 1384 } 1385 1386 return commonPointerCastTransforms(CI); 1387} 1388 1389/// OptimizeVectorResize - This input value (which is known to have vector type) 1390/// is being zero extended or truncated to the specified vector type. Try to 1391/// replace it with a shuffle (and vector/vector bitcast) if possible. 1392/// 1393/// The source and destination vector types may have different element types. 1394static Instruction *OptimizeVectorResize(Value *InVal, VectorType *DestTy, 1395 InstCombiner &IC) { 1396 // We can only do this optimization if the output is a multiple of the input 1397 // element size, or the input is a multiple of the output element size. 1398 // Convert the input type to have the same element type as the output. 1399 VectorType *SrcTy = cast<VectorType>(InVal->getType()); 1400 1401 if (SrcTy->getElementType() != DestTy->getElementType()) { 1402 // The input types don't need to be identical, but for now they must be the 1403 // same size. There is no specific reason we couldn't handle things like 1404 // <4 x i16> -> <4 x i32> by bitcasting to <2 x i32> but haven't gotten 1405 // there yet. 1406 if (SrcTy->getElementType()->getPrimitiveSizeInBits() != 1407 DestTy->getElementType()->getPrimitiveSizeInBits()) 1408 return 0; 1409 1410 SrcTy = VectorType::get(DestTy->getElementType(), SrcTy->getNumElements()); 1411 InVal = IC.Builder->CreateBitCast(InVal, SrcTy); 1412 } 1413 1414 // Now that the element types match, get the shuffle mask and RHS of the 1415 // shuffle to use, which depends on whether we're increasing or decreasing the 1416 // size of the input. 1417 SmallVector<uint32_t, 16> ShuffleMask; 1418 Value *V2; 1419 1420 if (SrcTy->getNumElements() > DestTy->getNumElements()) { 1421 // If we're shrinking the number of elements, just shuffle in the low 1422 // elements from the input and use undef as the second shuffle input. 1423 V2 = UndefValue::get(SrcTy); 1424 for (unsigned i = 0, e = DestTy->getNumElements(); i != e; ++i) 1425 ShuffleMask.push_back(i); 1426 1427 } else { 1428 // If we're increasing the number of elements, shuffle in all of the 1429 // elements from InVal and fill the rest of the result elements with zeros 1430 // from a constant zero. 1431 V2 = Constant::getNullValue(SrcTy); 1432 unsigned SrcElts = SrcTy->getNumElements(); 1433 for (unsigned i = 0, e = SrcElts; i != e; ++i) 1434 ShuffleMask.push_back(i); 1435 1436 // The excess elements reference the first element of the zero input. 1437 for (unsigned i = 0, e = DestTy->getNumElements()-SrcElts; i != e; ++i) 1438 ShuffleMask.push_back(SrcElts); 1439 } 1440 1441 return new ShuffleVectorInst(InVal, V2, 1442 ConstantDataVector::get(V2->getContext(), 1443 ShuffleMask)); 1444} 1445 1446static bool isMultipleOfTypeSize(unsigned Value, Type *Ty) { 1447 return Value % Ty->getPrimitiveSizeInBits() == 0; 1448} 1449 1450static unsigned getTypeSizeIndex(unsigned Value, Type *Ty) { 1451 return Value / Ty->getPrimitiveSizeInBits(); 1452} 1453 1454/// CollectInsertionElements - V is a value which is inserted into a vector of 1455/// VecEltTy. Look through the value to see if we can decompose it into 1456/// insertions into the vector. See the example in the comment for 1457/// OptimizeIntegerToVectorInsertions for the pattern this handles. 1458/// The type of V is always a non-zero multiple of VecEltTy's size. 1459/// 1460/// This returns false if the pattern can't be matched or true if it can, 1461/// filling in Elements with the elements found here. 1462static bool CollectInsertionElements(Value *V, unsigned ElementIndex, 1463 SmallVectorImpl<Value*> &Elements, 1464 Type *VecEltTy) { 1465 // Undef values never contribute useful bits to the result. 1466 if (isa<UndefValue>(V)) return true; 1467 1468 // If we got down to a value of the right type, we win, try inserting into the 1469 // right element. 1470 if (V->getType() == VecEltTy) { 1471 // Inserting null doesn't actually insert any elements. 1472 if (Constant *C = dyn_cast<Constant>(V)) 1473 if (C->isNullValue()) 1474 return true; 1475 1476 // Fail if multiple elements are inserted into this slot. 1477 if (ElementIndex >= Elements.size() || Elements[ElementIndex] != 0) 1478 return false; 1479 1480 Elements[ElementIndex] = V; 1481 return true; 1482 } 1483 1484 if (Constant *C = dyn_cast<Constant>(V)) { 1485 // Figure out the # elements this provides, and bitcast it or slice it up 1486 // as required. 1487 unsigned NumElts = getTypeSizeIndex(C->getType()->getPrimitiveSizeInBits(), 1488 VecEltTy); 1489 // If the constant is the size of a vector element, we just need to bitcast 1490 // it to the right type so it gets properly inserted. 1491 if (NumElts == 1) 1492 return CollectInsertionElements(ConstantExpr::getBitCast(C, VecEltTy), 1493 ElementIndex, Elements, VecEltTy); 1494 1495 // Okay, this is a constant that covers multiple elements. Slice it up into 1496 // pieces and insert each element-sized piece into the vector. 1497 if (!isa<IntegerType>(C->getType())) 1498 C = ConstantExpr::getBitCast(C, IntegerType::get(V->getContext(), 1499 C->getType()->getPrimitiveSizeInBits())); 1500 unsigned ElementSize = VecEltTy->getPrimitiveSizeInBits(); 1501 Type *ElementIntTy = IntegerType::get(C->getContext(), ElementSize); 1502 1503 for (unsigned i = 0; i != NumElts; ++i) { 1504 Constant *Piece = ConstantExpr::getLShr(C, ConstantInt::get(C->getType(), 1505 i*ElementSize)); 1506 Piece = ConstantExpr::getTrunc(Piece, ElementIntTy); 1507 if (!CollectInsertionElements(Piece, ElementIndex+i, Elements, VecEltTy)) 1508 return false; 1509 } 1510 return true; 1511 } 1512 1513 if (!V->hasOneUse()) return false; 1514 1515 Instruction *I = dyn_cast<Instruction>(V); 1516 if (I == 0) return false; 1517 switch (I->getOpcode()) { 1518 default: return false; // Unhandled case. 1519 case Instruction::BitCast: 1520 return CollectInsertionElements(I->getOperand(0), ElementIndex, 1521 Elements, VecEltTy); 1522 case Instruction::ZExt: 1523 if (!isMultipleOfTypeSize( 1524 I->getOperand(0)->getType()->getPrimitiveSizeInBits(), 1525 VecEltTy)) 1526 return false; 1527 return CollectInsertionElements(I->getOperand(0), ElementIndex, 1528 Elements, VecEltTy); 1529 case Instruction::Or: 1530 return CollectInsertionElements(I->getOperand(0), ElementIndex, 1531 Elements, VecEltTy) && 1532 CollectInsertionElements(I->getOperand(1), ElementIndex, 1533 Elements, VecEltTy); 1534 case Instruction::Shl: { 1535 // Must be shifting by a constant that is a multiple of the element size. 1536 ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1)); 1537 if (CI == 0) return false; 1538 if (!isMultipleOfTypeSize(CI->getZExtValue(), VecEltTy)) return false; 1539 unsigned IndexShift = getTypeSizeIndex(CI->getZExtValue(), VecEltTy); 1540 1541 return CollectInsertionElements(I->getOperand(0), ElementIndex+IndexShift, 1542 Elements, VecEltTy); 1543 } 1544 1545 } 1546} 1547 1548 1549/// OptimizeIntegerToVectorInsertions - If the input is an 'or' instruction, we 1550/// may be doing shifts and ors to assemble the elements of the vector manually. 1551/// Try to rip the code out and replace it with insertelements. This is to 1552/// optimize code like this: 1553/// 1554/// %tmp37 = bitcast float %inc to i32 1555/// %tmp38 = zext i32 %tmp37 to i64 1556/// %tmp31 = bitcast float %inc5 to i32 1557/// %tmp32 = zext i32 %tmp31 to i64 1558/// %tmp33 = shl i64 %tmp32, 32 1559/// %ins35 = or i64 %tmp33, %tmp38 1560/// %tmp43 = bitcast i64 %ins35 to <2 x float> 1561/// 1562/// Into two insertelements that do "buildvector{%inc, %inc5}". 1563static Value *OptimizeIntegerToVectorInsertions(BitCastInst &CI, 1564 InstCombiner &IC) { 1565 VectorType *DestVecTy = cast<VectorType>(CI.getType()); 1566 Value *IntInput = CI.getOperand(0); 1567 1568 SmallVector<Value*, 8> Elements(DestVecTy->getNumElements()); 1569 if (!CollectInsertionElements(IntInput, 0, Elements, 1570 DestVecTy->getElementType())) 1571 return 0; 1572 1573 // If we succeeded, we know that all of the element are specified by Elements 1574 // or are zero if Elements has a null entry. Recast this as a set of 1575 // insertions. 1576 Value *Result = Constant::getNullValue(CI.getType()); 1577 for (unsigned i = 0, e = Elements.size(); i != e; ++i) { 1578 if (Elements[i] == 0) continue; // Unset element. 1579 1580 Result = IC.Builder->CreateInsertElement(Result, Elements[i], 1581 IC.Builder->getInt32(i)); 1582 } 1583 1584 return Result; 1585} 1586 1587 1588/// OptimizeIntToFloatBitCast - See if we can optimize an integer->float/double 1589/// bitcast. The various long double bitcasts can't get in here. 1590static Instruction *OptimizeIntToFloatBitCast(BitCastInst &CI,InstCombiner &IC){ 1591 Value *Src = CI.getOperand(0); 1592 Type *DestTy = CI.getType(); 1593 1594 // If this is a bitcast from int to float, check to see if the int is an 1595 // extraction from a vector. 1596 Value *VecInput = 0; 1597 // bitcast(trunc(bitcast(somevector))) 1598 if (match(Src, m_Trunc(m_BitCast(m_Value(VecInput)))) && 1599 isa<VectorType>(VecInput->getType())) { 1600 VectorType *VecTy = cast<VectorType>(VecInput->getType()); 1601 unsigned DestWidth = DestTy->getPrimitiveSizeInBits(); 1602 1603 if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0) { 1604 // If the element type of the vector doesn't match the result type, 1605 // bitcast it to be a vector type we can extract from. 1606 if (VecTy->getElementType() != DestTy) { 1607 VecTy = VectorType::get(DestTy, 1608 VecTy->getPrimitiveSizeInBits() / DestWidth); 1609 VecInput = IC.Builder->CreateBitCast(VecInput, VecTy); 1610 } 1611 1612 return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(0)); 1613 } 1614 } 1615 1616 // bitcast(trunc(lshr(bitcast(somevector), cst)) 1617 ConstantInt *ShAmt = 0; 1618 if (match(Src, m_Trunc(m_LShr(m_BitCast(m_Value(VecInput)), 1619 m_ConstantInt(ShAmt)))) && 1620 isa<VectorType>(VecInput->getType())) { 1621 VectorType *VecTy = cast<VectorType>(VecInput->getType()); 1622 unsigned DestWidth = DestTy->getPrimitiveSizeInBits(); 1623 if (VecTy->getPrimitiveSizeInBits() % DestWidth == 0 && 1624 ShAmt->getZExtValue() % DestWidth == 0) { 1625 // If the element type of the vector doesn't match the result type, 1626 // bitcast it to be a vector type we can extract from. 1627 if (VecTy->getElementType() != DestTy) { 1628 VecTy = VectorType::get(DestTy, 1629 VecTy->getPrimitiveSizeInBits() / DestWidth); 1630 VecInput = IC.Builder->CreateBitCast(VecInput, VecTy); 1631 } 1632 1633 unsigned Elt = ShAmt->getZExtValue() / DestWidth; 1634 return ExtractElementInst::Create(VecInput, IC.Builder->getInt32(Elt)); 1635 } 1636 } 1637 return 0; 1638} 1639 1640Instruction *InstCombiner::visitBitCast(BitCastInst &CI) { 1641 // If the operands are integer typed then apply the integer transforms, 1642 // otherwise just apply the common ones. 1643 Value *Src = CI.getOperand(0); 1644 Type *SrcTy = Src->getType(); 1645 Type *DestTy = CI.getType(); 1646 1647 // Get rid of casts from one type to the same type. These are useless and can 1648 // be replaced by the operand. 1649 if (DestTy == Src->getType()) 1650 return ReplaceInstUsesWith(CI, Src); 1651 1652 if (PointerType *DstPTy = dyn_cast<PointerType>(DestTy)) { 1653 PointerType *SrcPTy = cast<PointerType>(SrcTy); 1654 Type *DstElTy = DstPTy->getElementType(); 1655 Type *SrcElTy = SrcPTy->getElementType(); 1656 1657 // If the address spaces don't match, don't eliminate the bitcast, which is 1658 // required for changing types. 1659 if (SrcPTy->getAddressSpace() != DstPTy->getAddressSpace()) 1660 return 0; 1661 1662 // If we are casting a alloca to a pointer to a type of the same 1663 // size, rewrite the allocation instruction to allocate the "right" type. 1664 // There is no need to modify malloc calls because it is their bitcast that 1665 // needs to be cleaned up. 1666 if (AllocaInst *AI = dyn_cast<AllocaInst>(Src)) 1667 if (Instruction *V = PromoteCastOfAllocation(CI, *AI)) 1668 return V; 1669 1670 // If the source and destination are pointers, and this cast is equivalent 1671 // to a getelementptr X, 0, 0, 0... turn it into the appropriate gep. 1672 // This can enhance SROA and other transforms that want type-safe pointers. 1673 Constant *ZeroUInt = 1674 Constant::getNullValue(Type::getInt32Ty(CI.getContext())); 1675 unsigned NumZeros = 0; 1676 while (SrcElTy != DstElTy && 1677 isa<CompositeType>(SrcElTy) && !SrcElTy->isPointerTy() && 1678 SrcElTy->getNumContainedTypes() /* not "{}" */) { 1679 SrcElTy = cast<CompositeType>(SrcElTy)->getTypeAtIndex(ZeroUInt); 1680 ++NumZeros; 1681 } 1682 1683 // If we found a path from the src to dest, create the getelementptr now. 1684 if (SrcElTy == DstElTy) { 1685 SmallVector<Value*, 8> Idxs(NumZeros+1, ZeroUInt); 1686 return GetElementPtrInst::CreateInBounds(Src, Idxs); 1687 } 1688 } 1689 1690 // Try to optimize int -> float bitcasts. 1691 if ((DestTy->isFloatTy() || DestTy->isDoubleTy()) && isa<IntegerType>(SrcTy)) 1692 if (Instruction *I = OptimizeIntToFloatBitCast(CI, *this)) 1693 return I; 1694 1695 if (VectorType *DestVTy = dyn_cast<VectorType>(DestTy)) { 1696 if (DestVTy->getNumElements() == 1 && !SrcTy->isVectorTy()) { 1697 Value *Elem = Builder->CreateBitCast(Src, DestVTy->getElementType()); 1698 return InsertElementInst::Create(UndefValue::get(DestTy), Elem, 1699 Constant::getNullValue(Type::getInt32Ty(CI.getContext()))); 1700 // FIXME: Canonicalize bitcast(insertelement) -> insertelement(bitcast) 1701 } 1702 1703 if (isa<IntegerType>(SrcTy)) { 1704 // If this is a cast from an integer to vector, check to see if the input 1705 // is a trunc or zext of a bitcast from vector. If so, we can replace all 1706 // the casts with a shuffle and (potentially) a bitcast. 1707 if (isa<TruncInst>(Src) || isa<ZExtInst>(Src)) { 1708 CastInst *SrcCast = cast<CastInst>(Src); 1709 if (BitCastInst *BCIn = dyn_cast<BitCastInst>(SrcCast->getOperand(0))) 1710 if (isa<VectorType>(BCIn->getOperand(0)->getType())) 1711 if (Instruction *I = OptimizeVectorResize(BCIn->getOperand(0), 1712 cast<VectorType>(DestTy), *this)) 1713 return I; 1714 } 1715 1716 // If the input is an 'or' instruction, we may be doing shifts and ors to 1717 // assemble the elements of the vector manually. Try to rip the code out 1718 // and replace it with insertelements. 1719 if (Value *V = OptimizeIntegerToVectorInsertions(CI, *this)) 1720 return ReplaceInstUsesWith(CI, V); 1721 } 1722 } 1723 1724 if (VectorType *SrcVTy = dyn_cast<VectorType>(SrcTy)) { 1725 if (SrcVTy->getNumElements() == 1 && !DestTy->isVectorTy()) { 1726 Value *Elem = 1727 Builder->CreateExtractElement(Src, 1728 Constant::getNullValue(Type::getInt32Ty(CI.getContext()))); 1729 return CastInst::Create(Instruction::BitCast, Elem, DestTy); 1730 } 1731 } 1732 1733 if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(Src)) { 1734 // Okay, we have (bitcast (shuffle ..)). Check to see if this is 1735 // a bitcast to a vector with the same # elts. 1736 if (SVI->hasOneUse() && DestTy->isVectorTy() && 1737 cast<VectorType>(DestTy)->getNumElements() == 1738 SVI->getType()->getNumElements() && 1739 SVI->getType()->getNumElements() == 1740 cast<VectorType>(SVI->getOperand(0)->getType())->getNumElements()) { 1741 BitCastInst *Tmp; 1742 // If either of the operands is a cast from CI.getType(), then 1743 // evaluating the shuffle in the casted destination's type will allow 1744 // us to eliminate at least one cast. 1745 if (((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(0))) && 1746 Tmp->getOperand(0)->getType() == DestTy) || 1747 ((Tmp = dyn_cast<BitCastInst>(SVI->getOperand(1))) && 1748 Tmp->getOperand(0)->getType() == DestTy)) { 1749 Value *LHS = Builder->CreateBitCast(SVI->getOperand(0), DestTy); 1750 Value *RHS = Builder->CreateBitCast(SVI->getOperand(1), DestTy); 1751 // Return a new shuffle vector. Use the same element ID's, as we 1752 // know the vector types match #elts. 1753 return new ShuffleVectorInst(LHS, RHS, SVI->getOperand(2)); 1754 } 1755 } 1756 } 1757 1758 if (SrcTy->isPointerTy()) 1759 return commonPointerCastTransforms(CI); 1760 return commonCastTransforms(CI); 1761} 1762