src/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

   1 //===- InstCombineMulDivRem.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 mul, fmul, sdiv, udiv, fdiv,
  11 // srem, urem, frem.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "InstCombine.h"
  16 #include "llvm/Analysis/InstructionSimplify.h"
  17 #include "llvm/IR/IntrinsicInst.h"
  18 #include "llvm/IR/PatternMatch.h"
  19 using namespace llvm;
  20 using namespace PatternMatch;
  21
  22 #define DEBUG_TYPE "instcombine"
  23
  24
  25 /// simplifyValueKnownNonZero - The specific integer value is used in a context
  26 /// where it is known to be non-zero.  If this allows us to simplify the
  27 /// computation, do so and return the new operand, otherwise return null.
  28 static Value *simplifyValueKnownNonZero(Value *V, InstCombiner &IC,
  29                                         Instruction *CxtI) {
  30   // If V has multiple uses, then we would have to do more analysis to determine
  31   // if this is safe.  For example, the use could be in dynamically unreached
  32   // code.
  33   if (!V->hasOneUse()) return nullptr;
  34
  35   bool MadeChange = false;
  36
  37   // ((1 << A) >>u B) --> (1 << (A-B))
  38   // Because V cannot be zero, we know that B is less than A.
  39   Value *A = nullptr, *B = nullptr, *One = nullptr;
  40   if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(One), m_Value(A))), m_Value(B))) &&
  41       match(One, m_One())) {
  42     A = IC.Builder->CreateSub(A, B);
  43     return IC.Builder->CreateShl(One, A);
  44   }
  45
  46   // (PowerOfTwo >>u B) --> isExact since shifting out the result would make it
  47   // inexact.  Similarly for <<.
  48   if (BinaryOperator *I = dyn_cast<BinaryOperator>(V))
  49     if (I->isLogicalShift() &&
  50         isKnownToBeAPowerOfTwo(I->getOperand(0), false, 0,
  51                                IC.getAssumptionCache(), CxtI,
  52                                IC.getDominatorTree())) {
  53       // We know that this is an exact/nuw shift and that the input is a
  54       // non-zero context as well.
  55       if (Value *V2 = simplifyValueKnownNonZero(I->getOperand(0), IC, CxtI)) {
  56         I->setOperand(0, V2);
  57         MadeChange = true;
  58       }
  59
  60       if (I->getOpcode() == Instruction::LShr && !I->isExact()) {
  61         I->setIsExact();
  62         MadeChange = true;
  63       }
  64
  65       if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
  66         I->setHasNoUnsignedWrap();
  67         MadeChange = true;
  68       }
  69     }
  70
  71   // TODO: Lots more we could do here:
  72   //    If V is a phi node, we can call this on each of its operands.
  73   //    "select cond, X, 0" can simplify to "X".
  74
  75   return MadeChange ? V : nullptr;
  76 }
  77
  78
  79 /// MultiplyOverflows - True if the multiply can not be expressed in an int
  80 /// this size.
  81 static bool MultiplyOverflows(const APInt &C1, const APInt &C2, APInt &Product,
  82                               bool IsSigned) {
  83   bool Overflow;
  84   if (IsSigned)
  85     Product = C1.smul_ov(C2, Overflow);
  86   else
  87     Product = C1.umul_ov(C2, Overflow);
  88
  89   return Overflow;
  90 }
  91
  92 /// \brief True if C2 is a multiple of C1. Quotient contains C2/C1.
  93 static bool IsMultiple(const APInt &C1, const APInt &C2, APInt &Quotient,
  94                        bool IsSigned) {
  95   assert(C1.getBitWidth() == C2.getBitWidth() &&
  96          "Inconsistent width of constants!");
  97
  98   APInt Remainder(C1.getBitWidth(), /*Val=*/0ULL, IsSigned);
  99   if (IsSigned)
 100     APInt::sdivrem(C1, C2, Quotient, Remainder);
 101   else
 102     APInt::udivrem(C1, C2, Quotient, Remainder);
 103
 104   return Remainder.isMinValue();
 105 }
 106
 107 /// \brief A helper routine of InstCombiner::visitMul().
 108 ///
 109 /// If C is a vector of known powers of 2, then this function returns
 110 /// a new vector obtained from C replacing each element with its logBase2.
 111 /// Return a null pointer otherwise.
 112 static Constant *getLogBase2Vector(ConstantDataVector *CV) {
 113   const APInt *IVal;
 114   SmallVector<Constant *, 4> Elts;
 115
 116   for (unsigned I = 0, E = CV->getNumElements(); I != E; ++I) {
 117     Constant *Elt = CV->getElementAsConstant(I);
 118     if (!match(Elt, m_APInt(IVal)) || !IVal->isPowerOf2())
 119       return nullptr;
 120     Elts.push_back(ConstantInt::get(Elt->getType(), IVal->logBase2()));
 121   }
 122
 123   return ConstantVector::get(Elts);
 124 }
 125
 126 /// \brief Return true if we can prove that:
 127 ///    (mul LHS, RHS)  === (mul nsw LHS, RHS)
 128 bool InstCombiner::WillNotOverflowSignedMul(Value *LHS, Value *RHS,
 129                                             Instruction *CxtI) {
 130   // Multiplying n * m significant bits yields a result of n + m significant
 131   // bits. If the total number of significant bits does not exceed the
 132   // result bit width (minus 1), there is no overflow.
 133   // This means if we have enough leading sign bits in the operands
 134   // we can guarantee that the result does not overflow.
 135   // Ref: "Hacker's Delight" by Henry Warren
 136   unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
 137
 138   // Note that underestimating the number of sign bits gives a more
 139   // conservative answer.
 140   unsigned SignBits = ComputeNumSignBits(LHS, 0, CxtI) +
 141                       ComputeNumSignBits(RHS, 0, CxtI);
 142
 143   // First handle the easy case: if we have enough sign bits there's
 144   // definitely no overflow.
 145   if (SignBits > BitWidth + 1)
 146     return true;
 147
 148   // There are two ambiguous cases where there can be no overflow:
 149   //   SignBits == BitWidth + 1    and
 150   //   SignBits == BitWidth
 151   // The second case is difficult to check, therefore we only handle the
 152   // first case.
 153   if (SignBits == BitWidth + 1) {
 154     // It overflows only when both arguments are negative and the true
 155     // product is exactly the minimum negative number.
 156     // E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
 157     // For simplicity we just check if at least one side is not negative.
 158     bool LHSNonNegative, LHSNegative;
 159     bool RHSNonNegative, RHSNegative;
 160     ComputeSignBit(LHS, LHSNonNegative, LHSNegative, /*Depth=*/0, CxtI);
 161     ComputeSignBit(RHS, RHSNonNegative, RHSNegative, /*Depth=*/0, CxtI);
 162     if (LHSNonNegative || RHSNonNegative)
 163       return true;
 164   }
 165   return false;
 166 }
 167
 168 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
 169   bool Changed = SimplifyAssociativeOrCommutative(I);
 170   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 171
 172   if (Value *V = SimplifyVectorOp(I))
 173     return ReplaceInstUsesWith(I, V);
 174
 175   if (Value *V = SimplifyMulInst(Op0, Op1, DL, TLI, DT, AC))
 176     return ReplaceInstUsesWith(I, V);
 177
 178   if (Value *V = SimplifyUsingDistributiveLaws(I))
 179     return ReplaceInstUsesWith(I, V);
 180
 181   // X * -1 == 0 - X
 182   if (match(Op1, m_AllOnes())) {
 183     BinaryOperator *BO = BinaryOperator::CreateNeg(Op0, I.getName());
 184     if (I.hasNoSignedWrap())
 185       BO->setHasNoSignedWrap();
 186     return BO;
 187   }
 188
 189   // Also allow combining multiply instructions on vectors.
 190   {
 191     Value *NewOp;
 192     Constant *C1, *C2;
 193     const APInt *IVal;
 194     if (match(&I, m_Mul(m_Shl(m_Value(NewOp), m_Constant(C2)),
 195                         m_Constant(C1))) &&
 196         match(C1, m_APInt(IVal))) {
 197       // ((X << C2)*C1) == (X * (C1 << C2))
 198       Constant *Shl = ConstantExpr::getShl(C1, C2);
 199       BinaryOperator *Mul = cast<BinaryOperator>(I.getOperand(0));
 200       BinaryOperator *BO = BinaryOperator::CreateMul(NewOp, Shl);
 201       if (I.hasNoUnsignedWrap() && Mul->hasNoUnsignedWrap())
 202         BO->setHasNoUnsignedWrap();
 203       if (I.hasNoSignedWrap() && Mul->hasNoSignedWrap() &&
 204           Shl->isNotMinSignedValue())
 205         BO->setHasNoSignedWrap();
 206       return BO;
 207     }
 208
 209     if (match(&I, m_Mul(m_Value(NewOp), m_Constant(C1)))) {
 210       Constant *NewCst = nullptr;
 211       if (match(C1, m_APInt(IVal)) && IVal->isPowerOf2())
 212         // Replace X*(2^C) with X << C, where C is either a scalar or a splat.
 213         NewCst = ConstantInt::get(NewOp->getType(), IVal->logBase2());
 214       else if (ConstantDataVector *CV = dyn_cast<ConstantDataVector>(C1))
 215         // Replace X*(2^C) with X << C, where C is a vector of known
 216         // constant powers of 2.
 217         NewCst = getLogBase2Vector(CV);
 218
 219       if (NewCst) {
 220         BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
 221
 222         if (I.hasNoUnsignedWrap())
 223           Shl->setHasNoUnsignedWrap();
 224         if (I.hasNoSignedWrap() && NewCst->isNotMinSignedValue())
 225           Shl->setHasNoSignedWrap();
 226
 227         return Shl;
 228       }
 229     }
 230   }
 231
 232   if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
 233     // (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
 234     // (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
 235     // The "* (2**n)" thus becomes a potential shifting opportunity.
 236     {
 237       const APInt &   Val = CI->getValue();
 238       const APInt &PosVal = Val.abs();
 239       if (Val.isNegative() && PosVal.isPowerOf2()) {
 240         Value *X = nullptr, *Y = nullptr;
 241         if (Op0->hasOneUse()) {
 242           ConstantInt *C1;
 243           Value *Sub = nullptr;
 244           if (match(Op0, m_Sub(m_Value(Y), m_Value(X))))
 245             Sub = Builder->CreateSub(X, Y, "suba");
 246           else if (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))
 247             Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc");
 248           if (Sub)
 249             return
 250               BinaryOperator::CreateMul(Sub,
 251                                         ConstantInt::get(Y->getType(), PosVal));
 252         }
 253       }
 254     }
 255   }
 256
 257   // Simplify mul instructions with a constant RHS.
 258   if (isa<Constant>(Op1)) {
 259     // Try to fold constant mul into select arguments.
 260     if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
 261       if (Instruction *R = FoldOpIntoSelect(I, SI))
 262         return R;
 263
 264     if (isa<PHINode>(Op0))
 265       if (Instruction *NV = FoldOpIntoPhi(I))
 266         return NV;
 267
 268     // Canonicalize (X+C1)*CI -> X*CI+C1*CI.
 269     {
 270       Value *X;
 271       Constant *C1;
 272       if (match(Op0, m_OneUse(m_Add(m_Value(X), m_Constant(C1))))) {
 273         Value *Mul = Builder->CreateMul(C1, Op1);
 274         // Only go forward with the transform if C1*CI simplifies to a tidier
 275         // constant.
 276         if (!match(Mul, m_Mul(m_Value(), m_Value())))
 277           return BinaryOperator::CreateAdd(Builder->CreateMul(X, Op1), Mul);
 278       }
 279     }
 280   }
 281
 282   if (Value *Op0v = dyn_castNegVal(Op0)) {   // -X * -Y = X*Y
 283     if (Value *Op1v = dyn_castNegVal(Op1)) {
 284       BinaryOperator *BO = BinaryOperator::CreateMul(Op0v, Op1v);
 285       if (I.hasNoSignedWrap() &&
 286           match(Op0, m_NSWSub(m_Value(), m_Value())) &&
 287           match(Op1, m_NSWSub(m_Value(), m_Value())))
 288         BO->setHasNoSignedWrap();
 289       return BO;
 290     }
 291   }
 292
 293   // (X / Y) *  Y = X - (X % Y)
 294   // (X / Y) * -Y = (X % Y) - X
 295   {
 296     Value *Op1C = Op1;
 297     BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0);
 298     if (!BO ||
 299         (BO->getOpcode() != Instruction::UDiv &&
 300          BO->getOpcode() != Instruction::SDiv)) {
 301       Op1C = Op0;
 302       BO = dyn_cast<BinaryOperator>(Op1);
 303     }
 304     Value *Neg = dyn_castNegVal(Op1C);
 305     if (BO && BO->hasOneUse() &&
 306         (BO->getOperand(1) == Op1C || BO->getOperand(1) == Neg) &&
 307         (BO->getOpcode() == Instruction::UDiv ||
 308          BO->getOpcode() == Instruction::SDiv)) {
 309       Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
 310
 311       // If the division is exact, X % Y is zero, so we end up with X or -X.
 312       if (PossiblyExactOperator *SDiv = dyn_cast<PossiblyExactOperator>(BO))
 313         if (SDiv->isExact()) {
 314           if (Op1BO == Op1C)
 315             return ReplaceInstUsesWith(I, Op0BO);
 316           return BinaryOperator::CreateNeg(Op0BO);
 317         }
 318
 319       Value *Rem;
 320       if (BO->getOpcode() == Instruction::UDiv)
 321         Rem = Builder->CreateURem(Op0BO, Op1BO);
 322       else
 323         Rem = Builder->CreateSRem(Op0BO, Op1BO);
 324       Rem->takeName(BO);
 325
 326       if (Op1BO == Op1C)
 327         return BinaryOperator::CreateSub(Op0BO, Rem);
 328       return BinaryOperator::CreateSub(Rem, Op0BO);
 329     }
 330   }
 331
 332   /// i1 mul -> i1 and.
 333   if (I.getType()->getScalarType()->isIntegerTy(1))
 334     return BinaryOperator::CreateAnd(Op0, Op1);
 335
 336   // X*(1 << Y) --> X << Y
 337   // (1 << Y)*X --> X << Y
 338   {
 339     Value *Y;
 340     BinaryOperator *BO = nullptr;
 341     bool ShlNSW = false;
 342     if (match(Op0, m_Shl(m_One(), m_Value(Y)))) {
 343       BO = BinaryOperator::CreateShl(Op1, Y);
 344       ShlNSW = cast<ShlOperator>(Op0)->hasNoSignedWrap();
 345     } else if (match(Op1, m_Shl(m_One(), m_Value(Y)))) {
 346       BO = BinaryOperator::CreateShl(Op0, Y);
 347       ShlNSW = cast<ShlOperator>(Op1)->hasNoSignedWrap();
 348     }
 349     if (BO) {
 350       if (I.hasNoUnsignedWrap())
 351         BO->setHasNoUnsignedWrap();
 352       if (I.hasNoSignedWrap() && ShlNSW)
 353         BO->setHasNoSignedWrap();
 354       return BO;
 355     }
 356   }
 357
 358   // If one of the operands of the multiply is a cast from a boolean value, then
 359   // we know the bool is either zero or one, so this is a 'masking' multiply.
 360   //   X * Y (where Y is 0 or 1) -> X & (0-Y)
 361   if (!I.getType()->isVectorTy()) {
 362     // -2 is "-1 << 1" so it is all bits set except the low one.
 363     APInt Negative2(I.getType()->getPrimitiveSizeInBits(), (uint64_t)-2, true);
 364
 365     Value *BoolCast = nullptr, *OtherOp = nullptr;
 366     if (MaskedValueIsZero(Op0, Negative2, 0, &I))
 367       BoolCast = Op0, OtherOp = Op1;
 368     else if (MaskedValueIsZero(Op1, Negative2, 0, &I))
 369       BoolCast = Op1, OtherOp = Op0;
 370
 371     if (BoolCast) {
 372       Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()),
 373                                     BoolCast);
 374       return BinaryOperator::CreateAnd(V, OtherOp);
 375     }
 376   }
 377
 378   if (!I.hasNoSignedWrap() && WillNotOverflowSignedMul(Op0, Op1, &I)) {
 379     Changed = true;
 380     I.setHasNoSignedWrap(true);
 381   }
 382
 383   if (!I.hasNoUnsignedWrap() &&
 384       computeOverflowForUnsignedMul(Op0, Op1, &I) ==
 385           OverflowResult::NeverOverflows) {
 386     Changed = true;
 387     I.setHasNoUnsignedWrap(true);
 388   }
 389
 390   return Changed ? &I : nullptr;
 391 }
 392
 393 /// Detect pattern log2(Y * 0.5) with corresponding fast math flags.
 394 static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) {
 395   if (!Op->hasOneUse())
 396     return;
 397
 398   IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op);
 399   if (!II)
 400     return;
 401   if (II->getIntrinsicID() != Intrinsic::log2 || !II->hasUnsafeAlgebra())
 402     return;
 403   Log2 = II;
 404
 405   Value *OpLog2Of = II->getArgOperand(0);
 406   if (!OpLog2Of->hasOneUse())
 407     return;
 408
 409   Instruction *I = dyn_cast<Instruction>(OpLog2Of);
 410   if (!I)
 411     return;
 412   if (I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra())
 413     return;
 414
 415   if (match(I->getOperand(0), m_SpecificFP(0.5)))
 416     Y = I->getOperand(1);
 417   else if (match(I->getOperand(1), m_SpecificFP(0.5)))
 418     Y = I->getOperand(0);
 419 }
 420
 421 static bool isFiniteNonZeroFp(Constant *C) {
 422   if (C->getType()->isVectorTy()) {
 423     for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E;
 424          ++I) {
 425       ConstantFP *CFP = dyn_cast<ConstantFP>(C->getAggregateElement(I));
 426       if (!CFP || !CFP->getValueAPF().isFiniteNonZero())
 427         return false;
 428     }
 429     return true;
 430   }
 431
 432   return isa<ConstantFP>(C) &&
 433          cast<ConstantFP>(C)->getValueAPF().isFiniteNonZero();
 434 }
 435
 436 static bool isNormalFp(Constant *C) {
 437   if (C->getType()->isVectorTy()) {
 438     for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E;
 439          ++I) {
 440       ConstantFP *CFP = dyn_cast<ConstantFP>(C->getAggregateElement(I));
 441       if (!CFP || !CFP->getValueAPF().isNormal())
 442         return false;
 443     }
 444     return true;
 445   }
 446
 447   return isa<ConstantFP>(C) && cast<ConstantFP>(C)->getValueAPF().isNormal();
 448 }
 449
 450 /// Helper function of InstCombiner::visitFMul(BinaryOperator(). It returns
 451 /// true iff the given value is FMul or FDiv with one and only one operand
 452 /// being a normal constant (i.e. not Zero/NaN/Infinity).
 453 static bool isFMulOrFDivWithConstant(Value *V) {
 454   Instruction *I = dyn_cast<Instruction>(V);
 455   if (!I || (I->getOpcode() != Instruction::FMul &&
 456              I->getOpcode() != Instruction::FDiv))
 457     return false;
 458
 459   Constant *C0 = dyn_cast<Constant>(I->getOperand(0));
 460   Constant *C1 = dyn_cast<Constant>(I->getOperand(1));
 461
 462   if (C0 && C1)
 463     return false;
 464
 465   return (C0 && isFiniteNonZeroFp(C0)) || (C1 && isFiniteNonZeroFp(C1));
 466 }
 467
 468 /// foldFMulConst() is a helper routine of InstCombiner::visitFMul().
 469 /// The input \p FMulOrDiv is a FMul/FDiv with one and only one operand
 470 /// being a constant (i.e. isFMulOrFDivWithConstant(FMulOrDiv) == true).
 471 /// This function is to simplify "FMulOrDiv * C" and returns the
 472 /// resulting expression. Note that this function could return NULL in
 473 /// case the constants cannot be folded into a normal floating-point.
 474 ///
 475 Value *InstCombiner::foldFMulConst(Instruction *FMulOrDiv, Constant *C,
 476                                    Instruction *InsertBefore) {
 477   assert(isFMulOrFDivWithConstant(FMulOrDiv) && "V is invalid");
 478
 479   Value *Opnd0 = FMulOrDiv->getOperand(0);
 480   Value *Opnd1 = FMulOrDiv->getOperand(1);
 481
 482   Constant *C0 = dyn_cast<Constant>(Opnd0);
 483   Constant *C1 = dyn_cast<Constant>(Opnd1);
 484
 485   BinaryOperator *R = nullptr;
 486
 487   // (X * C0) * C => X * (C0*C)
 488   if (FMulOrDiv->getOpcode() == Instruction::FMul) {
 489     Constant *F = ConstantExpr::getFMul(C1 ? C1 : C0, C);
 490     if (isNormalFp(F))
 491       R = BinaryOperator::CreateFMul(C1 ? Opnd0 : Opnd1, F);
 492   } else {
 493     if (C0) {
 494       // (C0 / X) * C => (C0 * C) / X
 495       if (FMulOrDiv->hasOneUse()) {
 496         // It would otherwise introduce another div.
 497         Constant *F = ConstantExpr::getFMul(C0, C);
 498         if (isNormalFp(F))
 499           R = BinaryOperator::CreateFDiv(F, Opnd1);
 500       }
 501     } else {
 502       // (X / C1) * C => X * (C/C1) if C/C1 is not a denormal
 503       Constant *F = ConstantExpr::getFDiv(C, C1);
 504       if (isNormalFp(F)) {
 505         R = BinaryOperator::CreateFMul(Opnd0, F);
 506       } else {
 507         // (X / C1) * C => X / (C1/C)
 508         Constant *F = ConstantExpr::getFDiv(C1, C);
 509         if (isNormalFp(F))
 510           R = BinaryOperator::CreateFDiv(Opnd0, F);
 511       }
 512     }
 513   }
 514
 515   if (R) {
 516     R->setHasUnsafeAlgebra(true);
 517     InsertNewInstWith(R, *InsertBefore);
 518   }
 519
 520   return R;
 521 }
 522
 523 Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
 524   bool Changed = SimplifyAssociativeOrCommutative(I);
 525   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 526
 527   if (Value *V = SimplifyVectorOp(I))
 528     return ReplaceInstUsesWith(I, V);
 529
 530   if (isa<Constant>(Op0))
 531     std::swap(Op0, Op1);
 532
 533   if (Value *V =
 534           SimplifyFMulInst(Op0, Op1, I.getFastMathFlags(), DL, TLI, DT, AC))
 535     return ReplaceInstUsesWith(I, V);
 536
 537   bool AllowReassociate = I.hasUnsafeAlgebra();
 538
 539   // Simplify mul instructions with a constant RHS.
 540   if (isa<Constant>(Op1)) {
 541     // Try to fold constant mul into select arguments.
 542     if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
 543       if (Instruction *R = FoldOpIntoSelect(I, SI))
 544         return R;
 545
 546     if (isa<PHINode>(Op0))
 547       if (Instruction *NV = FoldOpIntoPhi(I))
 548         return NV;
 549
 550     // (fmul X, -1.0) --> (fsub -0.0, X)
 551     if (match(Op1, m_SpecificFP(-1.0))) {
 552       Constant *NegZero = ConstantFP::getNegativeZero(Op1->getType());
 553       Instruction *RI = BinaryOperator::CreateFSub(NegZero, Op0);
 554       RI->copyFastMathFlags(&I);
 555       return RI;
 556     }
 557
 558     Constant *C = cast<Constant>(Op1);
 559     if (AllowReassociate && isFiniteNonZeroFp(C)) {
 560       // Let MDC denote an expression in one of these forms:
 561       // X * C, C/X, X/C, where C is a constant.
 562       //
 563       // Try to simplify "MDC * Constant"
 564       if (isFMulOrFDivWithConstant(Op0))
 565         if (Value *V = foldFMulConst(cast<Instruction>(Op0), C, &I))
 566           return ReplaceInstUsesWith(I, V);
 567
 568       // (MDC +/- C1) * C => (MDC * C) +/- (C1 * C)
 569       Instruction *FAddSub = dyn_cast<Instruction>(Op0);
 570       if (FAddSub &&
 571           (FAddSub->getOpcode() == Instruction::FAdd ||
 572            FAddSub->getOpcode() == Instruction::FSub)) {
 573         Value *Opnd0 = FAddSub->getOperand(0);
 574         Value *Opnd1 = FAddSub->getOperand(1);
 575         Constant *C0 = dyn_cast<Constant>(Opnd0);
 576         Constant *C1 = dyn_cast<Constant>(Opnd1);
 577         bool Swap = false;
 578         if (C0) {
 579           std::swap(C0, C1);
 580           std::swap(Opnd0, Opnd1);
 581           Swap = true;
 582         }
 583
 584         if (C1 && isFiniteNonZeroFp(C1) && isFMulOrFDivWithConstant(Opnd0)) {
 585           Value *M1 = ConstantExpr::getFMul(C1, C);
 586           Value *M0 = isNormalFp(cast<Constant>(M1)) ?
 587                       foldFMulConst(cast<Instruction>(Opnd0), C, &I) :
 588                       nullptr;
 589           if (M0 && M1) {
 590             if (Swap && FAddSub->getOpcode() == Instruction::FSub)
 591               std::swap(M0, M1);
 592
 593             Instruction *RI = (FAddSub->getOpcode() == Instruction::FAdd)
 594                                   ? BinaryOperator::CreateFAdd(M0, M1)
 595                                   : BinaryOperator::CreateFSub(M0, M1);
 596             RI->copyFastMathFlags(&I);
 597             return RI;
 598           }
 599         }
 600       }
 601     }
 602   }
 603
 604   // sqrt(X) * sqrt(X) -> X
 605   if (AllowReassociate && (Op0 == Op1))
 606     if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0))
 607       if (II->getIntrinsicID() == Intrinsic::sqrt)
 608         return ReplaceInstUsesWith(I, II->getOperand(0));
 609
 610   // Under unsafe algebra do:
 611   // X * log2(0.5*Y) = X*log2(Y) - X
 612   if (AllowReassociate) {
 613     Value *OpX = nullptr;
 614     Value *OpY = nullptr;
 615     IntrinsicInst *Log2;
 616     detectLog2OfHalf(Op0, OpY, Log2);
 617     if (OpY) {
 618       OpX = Op1;
 619     } else {
 620       detectLog2OfHalf(Op1, OpY, Log2);
 621       if (OpY) {
 622         OpX = Op0;
 623       }
 624     }
 625     // if pattern detected emit alternate sequence
 626     if (OpX && OpY) {
 627       BuilderTy::FastMathFlagGuard Guard(*Builder);
 628       Builder->SetFastMathFlags(Log2->getFastMathFlags());
 629       Log2->setArgOperand(0, OpY);
 630       Value *FMulVal = Builder->CreateFMul(OpX, Log2);
 631       Value *FSub = Builder->CreateFSub(FMulVal, OpX);
 632       FSub->takeName(&I);
 633       return ReplaceInstUsesWith(I, FSub);
 634     }
 635   }
 636
 637   // Handle symmetric situation in a 2-iteration loop
 638   Value *Opnd0 = Op0;
 639   Value *Opnd1 = Op1;
 640   for (int i = 0; i < 2; i++) {
 641     bool IgnoreZeroSign = I.hasNoSignedZeros();
 642     if (BinaryOperator::isFNeg(Opnd0, IgnoreZeroSign)) {
 643       BuilderTy::FastMathFlagGuard Guard(*Builder);
 644       Builder->SetFastMathFlags(I.getFastMathFlags());
 645
 646       Value *N0 = dyn_castFNegVal(Opnd0, IgnoreZeroSign);
 647       Value *N1 = dyn_castFNegVal(Opnd1, IgnoreZeroSign);
 648
 649       // -X * -Y => X*Y
 650       if (N1) {
 651         Value *FMul = Builder->CreateFMul(N0, N1);
 652         FMul->takeName(&I);
 653         return ReplaceInstUsesWith(I, FMul);
 654       }
 655
 656       if (Opnd0->hasOneUse()) {
 657         // -X * Y => -(X*Y) (Promote negation as high as possible)
 658         Value *T = Builder->CreateFMul(N0, Opnd1);
 659         Value *Neg = Builder->CreateFNeg(T);
 660         Neg->takeName(&I);
 661         return ReplaceInstUsesWith(I, Neg);
 662       }
 663     }
 664
 665     // (X*Y) * X => (X*X) * Y where Y != X
 666     //  The purpose is two-fold:
 667     //   1) to form a power expression (of X).
 668     //   2) potentially shorten the critical path: After transformation, the
 669     //  latency of the instruction Y is amortized by the expression of X*X,
 670     //  and therefore Y is in a "less critical" position compared to what it
 671     //  was before the transformation.
 672     //
 673     if (AllowReassociate) {
 674       Value *Opnd0_0, *Opnd0_1;
 675       if (Opnd0->hasOneUse() &&
 676           match(Opnd0, m_FMul(m_Value(Opnd0_0), m_Value(Opnd0_1)))) {
 677         Value *Y = nullptr;
 678         if (Opnd0_0 == Opnd1 && Opnd0_1 != Opnd1)
 679           Y = Opnd0_1;
 680         else if (Opnd0_1 == Opnd1 && Opnd0_0 != Opnd1)
 681           Y = Opnd0_0;
 682
 683         if (Y) {
 684           BuilderTy::FastMathFlagGuard Guard(*Builder);
 685           Builder->SetFastMathFlags(I.getFastMathFlags());
 686           Value *T = Builder->CreateFMul(Opnd1, Opnd1);
 687
 688           Value *R = Builder->CreateFMul(T, Y);
 689           R->takeName(&I);
 690           return ReplaceInstUsesWith(I, R);
 691         }
 692       }
 693     }
 694
 695     if (!isa<Constant>(Op1))
 696       std::swap(Opnd0, Opnd1);
 697     else
 698       break;
 699   }
 700
 701   return Changed ? &I : nullptr;
 702 }
 703
 704 /// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
 705 /// instruction.
 706 bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
 707   SelectInst *SI = cast<SelectInst>(I.getOperand(1));
 708
 709   // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
 710   int NonNullOperand = -1;
 711   if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
 712     if (ST->isNullValue())
 713       NonNullOperand = 2;
 714   // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
 715   if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
 716     if (ST->isNullValue())
 717       NonNullOperand = 1;
 718
 719   if (NonNullOperand == -1)
 720     return false;
 721
 722   Value *SelectCond = SI->getOperand(0);
 723
 724   // Change the div/rem to use 'Y' instead of the select.
 725   I.setOperand(1, SI->getOperand(NonNullOperand));
 726
 727   // Okay, we know we replace the operand of the div/rem with 'Y' with no
 728   // problem.  However, the select, or the condition of the select may have
 729   // multiple uses.  Based on our knowledge that the operand must be non-zero,
 730   // propagate the known value for the select into other uses of it, and
 731   // propagate a known value of the condition into its other users.
 732
 733   // If the select and condition only have a single use, don't bother with this,
 734   // early exit.
 735   if (SI->use_empty() && SelectCond->hasOneUse())
 736     return true;
 737
 738   // Scan the current block backward, looking for other uses of SI.
 739   BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
 740
 741   while (BBI != BBFront) {
 742     --BBI;
 743     // If we found a call to a function, we can't assume it will return, so
 744     // information from below it cannot be propagated above it.
 745     if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
 746       break;
 747
 748     // Replace uses of the select or its condition with the known values.
 749     for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
 750          I != E; ++I) {
 751       if (*I == SI) {
 752         *I = SI->getOperand(NonNullOperand);
 753         Worklist.Add(BBI);
 754       } else if (*I == SelectCond) {
 755         *I = Builder->getInt1(NonNullOperand == 1);
 756         Worklist.Add(BBI);
 757       }
 758     }
 759
 760     // If we past the instruction, quit looking for it.
 761     if (&*BBI == SI)
 762       SI = nullptr;
 763     if (&*BBI == SelectCond)
 764       SelectCond = nullptr;
 765
 766     // If we ran out of things to eliminate, break out of the loop.
 767     if (!SelectCond && !SI)
 768       break;
 769
 770   }
 771   return true;
 772 }
 773
 774
 775 /// This function implements the transforms common to both integer division
 776 /// instructions (udiv and sdiv). It is called by the visitors to those integer
 777 /// division instructions.
 778 /// @brief Common integer divide transforms
 779 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
 780   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
 781
 782   // The RHS is known non-zero.
 783   if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, &I)) {
 784     I.setOperand(1, V);
 785     return &I;
 786   }
 787
 788   // Handle cases involving: [su]div X, (select Cond, Y, Z)
 789   // This does not apply for fdiv.
 790   if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
 791     return &I;
 792
 793   if (Instruction *LHS = dyn_cast<Instruction>(Op0)) {
 794     const APInt *C2;
 795     if (match(Op1, m_APInt(C2))) {
 796       Value *X;
 797       const APInt *C1;
 798       bool IsSigned = I.getOpcode() == Instruction::SDiv;
 799
 800       // (X / C1) / C2  -> X / (C1*C2)
 801       if ((IsSigned && match(LHS, m_SDiv(m_Value(X), m_APInt(C1)))) ||
 802           (!IsSigned && match(LHS, m_UDiv(m_Value(X), m_APInt(C1))))) {
 803         APInt Product(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
 804         if (!MultiplyOverflows(*C1, *C2, Product, IsSigned))
 805           return BinaryOperator::Create(I.getOpcode(), X,
 806                                         ConstantInt::get(I.getType(), Product));
 807       }
 808
 809       if ((IsSigned && match(LHS, m_NSWMul(m_Value(X), m_APInt(C1)))) ||
 810           (!IsSigned && match(LHS, m_NUWMul(m_Value(X), m_APInt(C1))))) {
 811         APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
 812
 813         // (X * C1) / C2 -> X / (C2 / C1) if C2 is a multiple of C1.
 814         if (IsMultiple(*C2, *C1, Quotient, IsSigned)) {
 815           BinaryOperator *BO = BinaryOperator::Create(
 816               I.getOpcode(), X, ConstantInt::get(X->getType(), Quotient));
 817           BO->setIsExact(I.isExact());
 818           return BO;
 819         }
 820
 821         // (X * C1) / C2 -> X * (C1 / C2) if C1 is a multiple of C2.
 822         if (IsMultiple(*C1, *C2, Quotient, IsSigned)) {
 823           BinaryOperator *BO = BinaryOperator::Create(
 824               Instruction::Mul, X, ConstantInt::get(X->getType(), Quotient));
 825           BO->setHasNoUnsignedWrap(
 826               !IsSigned &&
 827               cast<OverflowingBinaryOperator>(LHS)->hasNoUnsignedWrap());
 828           BO->setHasNoSignedWrap(
 829               cast<OverflowingBinaryOperator>(LHS)->hasNoSignedWrap());
 830           return BO;
 831         }
 832       }
 833
 834       if ((IsSigned && match(LHS, m_NSWShl(m_Value(X), m_APInt(C1))) &&
 835            *C1 != C1->getBitWidth() - 1) ||
 836           (!IsSigned && match(LHS, m_NUWShl(m_Value(X), m_APInt(C1))))) {
 837         APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
 838         APInt C1Shifted = APInt::getOneBitSet(
 839             C1->getBitWidth(), static_cast<unsigned>(C1->getLimitedValue()));
 840
 841         // (X << C1) / C2 -> X / (C2 >> C1) if C2 is a multiple of C1.
 842         if (IsMultiple(*C2, C1Shifted, Quotient, IsSigned)) {
 843           BinaryOperator *BO = BinaryOperator::Create(
 844               I.getOpcode(), X, ConstantInt::get(X->getType(), Quotient));
 845           BO->setIsExact(I.isExact());
 846           return BO;
 847         }
 848
 849         // (X << C1) / C2 -> X * (C2 >> C1) if C1 is a multiple of C2.
 850         if (IsMultiple(C1Shifted, *C2, Quotient, IsSigned)) {
 851           BinaryOperator *BO = BinaryOperator::Create(
 852               Instruction::Mul, X, ConstantInt::get(X->getType(), Quotient));
 853           BO->setHasNoUnsignedWrap(
 854               !IsSigned &&
 855               cast<OverflowingBinaryOperator>(LHS)->hasNoUnsignedWrap());
 856           BO->setHasNoSignedWrap(
 857               cast<OverflowingBinaryOperator>(LHS)->hasNoSignedWrap());
 858           return BO;
 859         }
 860       }
 861
 862       if (*C2 != 0) { // avoid X udiv 0
 863         if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
 864           if (Instruction *R = FoldOpIntoSelect(I, SI))
 865             return R;
 866         if (isa<PHINode>(Op0))
 867           if (Instruction *NV = FoldOpIntoPhi(I))
 868             return NV;
 869       }
 870     }
 871   }
 872
 873   if (ConstantInt *One = dyn_cast<ConstantInt>(Op0)) {
 874     if (One->isOne() && !I.getType()->isIntegerTy(1)) {
 875       bool isSigned = I.getOpcode() == Instruction::SDiv;
 876       if (isSigned) {
 877         // If Op1 is 0 then it's undefined behaviour, if Op1 is 1 then the
 878         // result is one, if Op1 is -1 then the result is minus one, otherwise
 879         // it's zero.
 880         Value *Inc = Builder->CreateAdd(Op1, One);
 881         Value *Cmp = Builder->CreateICmpULT(
 882                          Inc, ConstantInt::get(I.getType(), 3));
 883         return SelectInst::Create(Cmp, Op1, ConstantInt::get(I.getType(), 0));
 884       } else {
 885         // If Op1 is 0 then it's undefined behaviour. If Op1 is 1 then the
 886         // result is one, otherwise it's zero.
 887         return new ZExtInst(Builder->CreateICmpEQ(Op1, One), I.getType());
 888       }
 889     }
 890   }
 891
 892   // See if we can fold away this div instruction.
 893   if (SimplifyDemandedInstructionBits(I))
 894     return &I;
 895
 896   // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
 897   Value *X = nullptr, *Z = nullptr;
 898   if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
 899     bool isSigned = I.getOpcode() == Instruction::SDiv;
 900     if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
 901         (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
 902       return BinaryOperator::Create(I.getOpcode(), X, Op1);
 903   }
 904
 905   return nullptr;
 906 }
 907
 908 /// dyn_castZExtVal - Checks if V is a zext or constant that can
 909 /// be truncated to Ty without losing bits.
 910 static Value *dyn_castZExtVal(Value *V, Type *Ty) {
 911   if (ZExtInst *Z = dyn_cast<ZExtInst>(V)) {
 912     if (Z->getSrcTy() == Ty)
 913       return Z->getOperand(0);
 914   } else if (ConstantInt *C = dyn_cast<ConstantInt>(V)) {
 915     if (C->getValue().getActiveBits() <= cast<IntegerType>(Ty)->getBitWidth())
 916       return ConstantExpr::getTrunc(C, Ty);
 917   }
 918   return nullptr;
 919 }
 920
 921 namespace {
 922 const unsigned MaxDepth = 6;
 923 typedef Instruction *(*FoldUDivOperandCb)(Value *Op0, Value *Op1,
 924                                           const BinaryOperator &I,
 925                                           InstCombiner &IC);
 926
 927 /// \brief Used to maintain state for visitUDivOperand().
 928 struct UDivFoldAction {
 929   FoldUDivOperandCb FoldAction; ///< Informs visitUDiv() how to fold this
 930                                 ///< operand.  This can be zero if this action
 931                                 ///< joins two actions together.
 932
 933   Value *OperandToFold;         ///< Which operand to fold.
 934   union {
 935     Instruction *FoldResult;    ///< The instruction returned when FoldAction is
 936                                 ///< invoked.
 937
 938     size_t SelectLHSIdx;        ///< Stores the LHS action index if this action
 939                                 ///< joins two actions together.
 940   };
 941
 942   UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand)
 943       : FoldAction(FA), OperandToFold(InputOperand), FoldResult(nullptr) {}
 944   UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand, size_t SLHS)
 945       : FoldAction(FA), OperandToFold(InputOperand), SelectLHSIdx(SLHS) {}
 946 };
 947 }
 948
 949 // X udiv 2^C -> X >> C
 950 static Instruction *foldUDivPow2Cst(Value *Op0, Value *Op1,
 951                                     const BinaryOperator &I, InstCombiner &IC) {
 952   const APInt &C = cast<Constant>(Op1)->getUniqueInteger();
 953   BinaryOperator *LShr = BinaryOperator::CreateLShr(
 954       Op0, ConstantInt::get(Op0->getType(), C.logBase2()));
 955   if (I.isExact())
 956     LShr->setIsExact();
 957   return LShr;
 958 }
 959
 960 // X udiv C, where C >= signbit
 961 static Instruction *foldUDivNegCst(Value *Op0, Value *Op1,
 962                                    const BinaryOperator &I, InstCombiner &IC) {
 963   Value *ICI = IC.Builder->CreateICmpULT(Op0, cast<ConstantInt>(Op1));
 964
 965   return SelectInst::Create(ICI, Constant::getNullValue(I.getType()),
 966                             ConstantInt::get(I.getType(), 1));
 967 }
 968
 969 // X udiv (C1 << N), where C1 is "1<<C2"  -->  X >> (N+C2)
 970 static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
 971                                 InstCombiner &IC) {
 972   Instruction *ShiftLeft = cast<Instruction>(Op1);
 973   if (isa<ZExtInst>(ShiftLeft))
 974     ShiftLeft = cast<Instruction>(ShiftLeft->getOperand(0));
 975
 976   const APInt &CI =
 977       cast<Constant>(ShiftLeft->getOperand(0))->getUniqueInteger();
 978   Value *N = ShiftLeft->getOperand(1);
 979   if (CI != 1)
 980     N = IC.Builder->CreateAdd(N, ConstantInt::get(N->getType(), CI.logBase2()));
 981   if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
 982     N = IC.Builder->CreateZExt(N, Z->getDestTy());
 983   BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N);
 984   if (I.isExact())
 985     LShr->setIsExact();
 986   return LShr;
 987 }
 988
 989 // \brief Recursively visits the possible right hand operands of a udiv
 990 // instruction, seeing through select instructions, to determine if we can
 991 // replace the udiv with something simpler.  If we find that an operand is not
 992 // able to simplify the udiv, we abort the entire transformation.
 993 static size_t visitUDivOperand(Value *Op0, Value *Op1, const BinaryOperator &I,
 994                                SmallVectorImpl<UDivFoldAction> &Actions,
 995                                unsigned Depth = 0) {
 996   // Check to see if this is an unsigned division with an exact power of 2,
 997   // if so, convert to a right shift.
 998   if (match(Op1, m_Power2())) {
 999     Actions.push_back(UDivFoldAction(foldUDivPow2Cst, Op1));
1000     return Actions.size();
1001   }
1002
1003   if (ConstantInt *C = dyn_cast<ConstantInt>(Op1))
1004     // X udiv C, where C >= signbit
1005     if (C->getValue().isNegative()) {
1006       Actions.push_back(UDivFoldAction(foldUDivNegCst, C));
1007       return Actions.size();
1008     }
1009
1010   // X udiv (C1 << N), where C1 is "1<<C2"  -->  X >> (N+C2)
1011   if (match(Op1, m_Shl(m_Power2(), m_Value())) ||
1012       match(Op1, m_ZExt(m_Shl(m_Power2(), m_Value())))) {
1013     Actions.push_back(UDivFoldAction(foldUDivShl, Op1));
1014     return Actions.size();
1015   }
1016
1017   // The remaining tests are all recursive, so bail out if we hit the limit.
1018   if (Depth++ == MaxDepth)
1019     return 0;
1020
1021   if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1022     if (size_t LHSIdx =
1023             visitUDivOperand(Op0, SI->getOperand(1), I, Actions, Depth))
1024       if (visitUDivOperand(Op0, SI->getOperand(2), I, Actions, Depth)) {
1025         Actions.push_back(UDivFoldAction(nullptr, Op1, LHSIdx - 1));
1026         return Actions.size();
1027       }
1028
1029   return 0;
1030 }
1031
1032 Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
1033   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1034
1035   if (Value *V = SimplifyVectorOp(I))
1036     return ReplaceInstUsesWith(I, V);
1037
1038   if (Value *V = SimplifyUDivInst(Op0, Op1, DL, TLI, DT, AC))
1039     return ReplaceInstUsesWith(I, V);
1040
1041   // Handle the integer div common cases
1042   if (Instruction *Common = commonIDivTransforms(I))
1043     return Common;
1044
1045   // (x lshr C1) udiv C2 --> x udiv (C2 << C1)
1046   {
1047     Value *X;
1048     const APInt *C1, *C2;
1049     if (match(Op0, m_LShr(m_Value(X), m_APInt(C1))) &&
1050         match(Op1, m_APInt(C2))) {
1051       bool Overflow;
1052       APInt C2ShlC1 = C2->ushl_ov(*C1, Overflow);
1053       if (!Overflow) {
1054         bool IsExact = I.isExact() && match(Op0, m_Exact(m_Value()));
1055         BinaryOperator *BO = BinaryOperator::CreateUDiv(
1056             X, ConstantInt::get(X->getType(), C2ShlC1));
1057         if (IsExact)
1058           BO->setIsExact();
1059         return BO;
1060       }
1061     }
1062   }
1063
1064   // (zext A) udiv (zext B) --> zext (A udiv B)
1065   if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
1066     if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
1067       return new ZExtInst(
1068           Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div", I.isExact()),
1069           I.getType());
1070
1071   // (LHS udiv (select (select (...)))) -> (LHS >> (select (select (...))))
1072   SmallVector<UDivFoldAction, 6> UDivActions;
1073   if (visitUDivOperand(Op0, Op1, I, UDivActions))
1074     for (unsigned i = 0, e = UDivActions.size(); i != e; ++i) {
1075       FoldUDivOperandCb Action = UDivActions[i].FoldAction;
1076       Value *ActionOp1 = UDivActions[i].OperandToFold;
1077       Instruction *Inst;
1078       if (Action)
1079         Inst = Action(Op0, ActionOp1, I, *this);
1080       else {
1081         // This action joins two actions together.  The RHS of this action is
1082         // simply the last action we processed, we saved the LHS action index in
1083         // the joining action.
1084         size_t SelectRHSIdx = i - 1;
1085         Value *SelectRHS = UDivActions[SelectRHSIdx].FoldResult;
1086         size_t SelectLHSIdx = UDivActions[i].SelectLHSIdx;
1087         Value *SelectLHS = UDivActions[SelectLHSIdx].FoldResult;
1088         Inst = SelectInst::Create(cast<SelectInst>(ActionOp1)->getCondition(),
1089                                   SelectLHS, SelectRHS);
1090       }
1091
1092       // If this is the last action to process, return it to the InstCombiner.
1093       // Otherwise, we insert it before the UDiv and record it so that we may
1094       // use it as part of a joining action (i.e., a SelectInst).
1095       if (e - i != 1) {
1096         Inst->insertBefore(&I);
1097         UDivActions[i].FoldResult = Inst;
1098       } else
1099         return Inst;
1100     }
1101
1102   return nullptr;
1103 }
1104
1105 Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
1106   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1107
1108   if (Value *V = SimplifyVectorOp(I))
1109     return ReplaceInstUsesWith(I, V);
1110
1111   if (Value *V = SimplifySDivInst(Op0, Op1, DL, TLI, DT, AC))
1112     return ReplaceInstUsesWith(I, V);
1113
1114   // Handle the integer div common cases
1115   if (Instruction *Common = commonIDivTransforms(I))
1116     return Common;
1117
1118   // sdiv X, -1 == -X
1119   if (match(Op1, m_AllOnes()))
1120     return BinaryOperator::CreateNeg(Op0);
1121
1122   if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
1123     // sdiv X, C  -->  ashr exact X, log2(C)
1124     if (I.isExact() && RHS->getValue().isNonNegative() &&
1125         RHS->getValue().isPowerOf2()) {
1126       Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
1127                                             RHS->getValue().exactLogBase2());
1128       return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName());
1129     }
1130   }
1131
1132   if (Constant *RHS = dyn_cast<Constant>(Op1)) {
1133     // X/INT_MIN -> X == INT_MIN
1134     if (RHS->isMinSignedValue())
1135       return new ZExtInst(Builder->CreateICmpEQ(Op0, Op1), I.getType());
1136
1137     // -X/C  -->  X/-C  provided the negation doesn't overflow.
1138     Value *X;
1139     if (match(Op0, m_NSWSub(m_Zero(), m_Value(X)))) {
1140       auto *BO = BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(RHS));
1141       BO->setIsExact(I.isExact());
1142       return BO;
1143     }
1144   }
1145
1146   // If the sign bits of both operands are zero (i.e. we can prove they are
1147   // unsigned inputs), turn this into a udiv.
1148   if (I.getType()->isIntegerTy()) {
1149     APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
1150     if (MaskedValueIsZero(Op0, Mask, 0, &I)) {
1151       if (MaskedValueIsZero(Op1, Mask, 0, &I)) {
1152         // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
1153         auto *BO = BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
1154         BO->setIsExact(I.isExact());
1155         return BO;
1156       }
1157
1158       if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/ true, 0, AC, &I, DT)) {
1159         // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
1160         // Safe because the only negative value (1 << Y) can take on is
1161         // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
1162         // the sign bit set.
1163         auto *BO = BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
1164         BO->setIsExact(I.isExact());
1165         return BO;
1166       }
1167     }
1168   }
1169
1170   return nullptr;
1171 }
1172
1173 /// CvtFDivConstToReciprocal tries to convert X/C into X*1/C if C not a special
1174 /// FP value and:
1175 ///    1) 1/C is exact, or
1176 ///    2) reciprocal is allowed.
1177 /// If the conversion was successful, the simplified expression "X * 1/C" is
1178 /// returned; otherwise, NULL is returned.
1179 ///
1180 static Instruction *CvtFDivConstToReciprocal(Value *Dividend, Constant *Divisor,
1181                                              bool AllowReciprocal) {
1182   if (!isa<ConstantFP>(Divisor)) // TODO: handle vectors.
1183     return nullptr;
1184
1185   const APFloat &FpVal = cast<ConstantFP>(Divisor)->getValueAPF();
1186   APFloat Reciprocal(FpVal.getSemantics());
1187   bool Cvt = FpVal.getExactInverse(&Reciprocal);
1188
1189   if (!Cvt && AllowReciprocal && FpVal.isFiniteNonZero()) {
1190     Reciprocal = APFloat(FpVal.getSemantics(), 1.0f);
1191     (void)Reciprocal.divide(FpVal, APFloat::rmNearestTiesToEven);
1192     Cvt = !Reciprocal.isDenormal();
1193   }
1194
1195   if (!Cvt)
1196     return nullptr;
1197
1198   ConstantFP *R;
1199   R = ConstantFP::get(Dividend->getType()->getContext(), Reciprocal);
1200   return BinaryOperator::CreateFMul(Dividend, R);
1201 }
1202
1203 Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
1204   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1205
1206   if (Value *V = SimplifyVectorOp(I))
1207     return ReplaceInstUsesWith(I, V);
1208
1209   if (Value *V = SimplifyFDivInst(Op0, Op1, DL, TLI, DT, AC))
1210     return ReplaceInstUsesWith(I, V);
1211
1212   if (isa<Constant>(Op0))
1213     if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1214       if (Instruction *R = FoldOpIntoSelect(I, SI))
1215         return R;
1216
1217   bool AllowReassociate = I.hasUnsafeAlgebra();
1218   bool AllowReciprocal = I.hasAllowReciprocal();
1219
1220   if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1221     if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1222       if (Instruction *R = FoldOpIntoSelect(I, SI))
1223         return R;
1224
1225     if (AllowReassociate) {
1226       Constant *C1 = nullptr;
1227       Constant *C2 = Op1C;
1228       Value *X;
1229       Instruction *Res = nullptr;
1230
1231       if (match(Op0, m_FMul(m_Value(X), m_Constant(C1)))) {
1232         // (X*C1)/C2 => X * (C1/C2)
1233         //
1234         Constant *C = ConstantExpr::getFDiv(C1, C2);
1235         if (isNormalFp(C))
1236           Res = BinaryOperator::CreateFMul(X, C);
1237       } else if (match(Op0, m_FDiv(m_Value(X), m_Constant(C1)))) {
1238         // (X/C1)/C2 => X /(C2*C1) [=> X * 1/(C2*C1) if reciprocal is allowed]
1239         //
1240         Constant *C = ConstantExpr::getFMul(C1, C2);
1241         if (isNormalFp(C)) {
1242           Res = CvtFDivConstToReciprocal(X, C, AllowReciprocal);
1243           if (!Res)
1244             Res = BinaryOperator::CreateFDiv(X, C);
1245         }
1246       }
1247
1248       if (Res) {
1249         Res->setFastMathFlags(I.getFastMathFlags());
1250         return Res;
1251       }
1252     }
1253
1254     // X / C => X * 1/C
1255     if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal)) {
1256       T->copyFastMathFlags(&I);
1257       return T;
1258     }
1259
1260     return nullptr;
1261   }
1262
1263   if (AllowReassociate && isa<Constant>(Op0)) {
1264     Constant *C1 = cast<Constant>(Op0), *C2;
1265     Constant *Fold = nullptr;
1266     Value *X;
1267     bool CreateDiv = true;
1268
1269     // C1 / (X*C2) => (C1/C2) / X
1270     if (match(Op1, m_FMul(m_Value(X), m_Constant(C2))))
1271       Fold = ConstantExpr::getFDiv(C1, C2);
1272     else if (match(Op1, m_FDiv(m_Value(X), m_Constant(C2)))) {
1273       // C1 / (X/C2) => (C1*C2) / X
1274       Fold = ConstantExpr::getFMul(C1, C2);
1275     } else if (match(Op1, m_FDiv(m_Constant(C2), m_Value(X)))) {
1276       // C1 / (C2/X) => (C1/C2) * X
1277       Fold = ConstantExpr::getFDiv(C1, C2);
1278       CreateDiv = false;
1279     }
1280
1281     if (Fold && isNormalFp(Fold)) {
1282       Instruction *R = CreateDiv ? BinaryOperator::CreateFDiv(Fold, X)
1283                                  : BinaryOperator::CreateFMul(X, Fold);
1284       R->setFastMathFlags(I.getFastMathFlags());
1285       return R;
1286     }
1287     return nullptr;
1288   }
1289
1290   if (AllowReassociate) {
1291     Value *X, *Y;
1292     Value *NewInst = nullptr;
1293     Instruction *SimpR = nullptr;
1294
1295     if (Op0->hasOneUse() && match(Op0, m_FDiv(m_Value(X), m_Value(Y)))) {
1296       // (X/Y) / Z => X / (Y*Z)
1297       //
1298       if (!isa<Constant>(Y) || !isa<Constant>(Op1)) {
1299         NewInst = Builder->CreateFMul(Y, Op1);
1300         if (Instruction *RI = dyn_cast<Instruction>(NewInst)) {
1301           FastMathFlags Flags = I.getFastMathFlags();
1302           Flags &= cast<Instruction>(Op0)->getFastMathFlags();
1303           RI->setFastMathFlags(Flags);
1304         }
1305         SimpR = BinaryOperator::CreateFDiv(X, NewInst);
1306       }
1307     } else if (Op1->hasOneUse() && match(Op1, m_FDiv(m_Value(X), m_Value(Y)))) {
1308       // Z / (X/Y) => Z*Y / X
1309       //
1310       if (!isa<Constant>(Y) || !isa<Constant>(Op0)) {
1311         NewInst = Builder->CreateFMul(Op0, Y);
1312         if (Instruction *RI = dyn_cast<Instruction>(NewInst)) {
1313           FastMathFlags Flags = I.getFastMathFlags();
1314           Flags &= cast<Instruction>(Op1)->getFastMathFlags();
1315           RI->setFastMathFlags(Flags);
1316         }
1317         SimpR = BinaryOperator::CreateFDiv(NewInst, X);
1318       }
1319     }
1320
1321     if (NewInst) {
1322       if (Instruction *T = dyn_cast<Instruction>(NewInst))
1323         T->setDebugLoc(I.getDebugLoc());
1324       SimpR->setFastMathFlags(I.getFastMathFlags());
1325       return SimpR;
1326     }
1327   }
1328
1329   return nullptr;
1330 }
1331
1332 /// This function implements the transforms common to both integer remainder
1333 /// instructions (urem and srem). It is called by the visitors to those integer
1334 /// remainder instructions.
1335 /// @brief Common integer remainder transforms
1336 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
1337   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1338
1339   // The RHS is known non-zero.
1340   if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, &I)) {
1341     I.setOperand(1, V);
1342     return &I;
1343   }
1344
1345   // Handle cases involving: rem X, (select Cond, Y, Z)
1346   if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
1347     return &I;
1348
1349   if (isa<Constant>(Op1)) {
1350     if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1351       if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
1352         if (Instruction *R = FoldOpIntoSelect(I, SI))
1353           return R;
1354       } else if (isa<PHINode>(Op0I)) {
1355         if (Instruction *NV = FoldOpIntoPhi(I))
1356           return NV;
1357       }
1358
1359       // See if we can fold away this rem instruction.
1360       if (SimplifyDemandedInstructionBits(I))
1361         return &I;
1362     }
1363   }
1364
1365   return nullptr;
1366 }
1367
1368 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
1369   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1370
1371   if (Value *V = SimplifyVectorOp(I))
1372     return ReplaceInstUsesWith(I, V);
1373
1374   if (Value *V = SimplifyURemInst(Op0, Op1, DL, TLI, DT, AC))
1375     return ReplaceInstUsesWith(I, V);
1376
1377   if (Instruction *common = commonIRemTransforms(I))
1378     return common;
1379
1380   // (zext A) urem (zext B) --> zext (A urem B)
1381   if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
1382     if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
1383       return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
1384                           I.getType());
1385
1386   // X urem Y -> X and Y-1, where Y is a power of 2,
1387   if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/ true, 0, AC, &I, DT)) {
1388     Constant *N1 = Constant::getAllOnesValue(I.getType());
1389     Value *Add = Builder->CreateAdd(Op1, N1);
1390     return BinaryOperator::CreateAnd(Op0, Add);
1391   }
1392
1393   // 1 urem X -> zext(X != 1)
1394   if (match(Op0, m_One())) {
1395     Value *Cmp = Builder->CreateICmpNE(Op1, Op0);
1396     Value *Ext = Builder->CreateZExt(Cmp, I.getType());
1397     return ReplaceInstUsesWith(I, Ext);
1398   }
1399
1400   return nullptr;
1401 }
1402
1403 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
1404   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1405
1406   if (Value *V = SimplifyVectorOp(I))
1407     return ReplaceInstUsesWith(I, V);
1408
1409   if (Value *V = SimplifySRemInst(Op0, Op1, DL, TLI, DT, AC))
1410     return ReplaceInstUsesWith(I, V);
1411
1412   // Handle the integer rem common cases
1413   if (Instruction *Common = commonIRemTransforms(I))
1414     return Common;
1415
1416   {
1417     const APInt *Y;
1418     // X % -Y -> X % Y
1419     if (match(Op1, m_APInt(Y)) && Y->isNegative() && !Y->isMinSignedValue()) {
1420       Worklist.AddValue(I.getOperand(1));
1421       I.setOperand(1, ConstantInt::get(I.getType(), -*Y));
1422       return &I;
1423     }
1424   }
1425
1426   // If the sign bits of both operands are zero (i.e. we can prove they are
1427   // unsigned inputs), turn this into a urem.
1428   if (I.getType()->isIntegerTy()) {
1429     APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
1430     if (MaskedValueIsZero(Op1, Mask, 0, &I) &&
1431         MaskedValueIsZero(Op0, Mask, 0, &I)) {
1432       // X srem Y -> X urem Y, iff X and Y don't have sign bit set
1433       return BinaryOperator::CreateURem(Op0, Op1, I.getName());
1434     }
1435   }
1436
1437   // If it's a constant vector, flip any negative values positive.
1438   if (isa<ConstantVector>(Op1) || isa<ConstantDataVector>(Op1)) {
1439     Constant *C = cast<Constant>(Op1);
1440     unsigned VWidth = C->getType()->getVectorNumElements();
1441
1442     bool hasNegative = false;
1443     bool hasMissing = false;
1444     for (unsigned i = 0; i != VWidth; ++i) {
1445       Constant *Elt = C->getAggregateElement(i);
1446       if (!Elt) {
1447         hasMissing = true;
1448         break;
1449       }
1450
1451       if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elt))
1452         if (RHS->isNegative())
1453           hasNegative = true;
1454     }
1455
1456     if (hasNegative && !hasMissing) {
1457       SmallVector<Constant *, 16> Elts(VWidth);
1458       for (unsigned i = 0; i != VWidth; ++i) {
1459         Elts[i] = C->getAggregateElement(i);  // Handle undef, etc.
1460         if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elts[i])) {
1461           if (RHS->isNegative())
1462             Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
1463         }
1464       }
1465
1466       Constant *NewRHSV = ConstantVector::get(Elts);
1467       if (NewRHSV != C) {  // Don't loop on -MININT
1468         Worklist.AddValue(I.getOperand(1));
1469         I.setOperand(1, NewRHSV);
1470         return &I;
1471       }
1472     }
1473   }
1474
1475   return nullptr;
1476 }
1477
1478 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
1479   Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1480
1481   if (Value *V = SimplifyVectorOp(I))
1482     return ReplaceInstUsesWith(I, V);
1483
1484   if (Value *V = SimplifyFRemInst(Op0, Op1, DL, TLI, DT, AC))
1485     return ReplaceInstUsesWith(I, V);
1486
1487   // Handle cases involving: rem X, (select Cond, Y, Z)
1488   if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
1489     return &I;
1490
1491   return nullptr;
1492 }