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Diffstat (limited to 'contrib/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 1117 |
1 files changed, 1117 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/contrib/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp new file mode 100644 index 0000000..173f2bf --- /dev/null +++ b/contrib/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -0,0 +1,1117 @@ +//===- InstCombineMulDivRem.cpp -------------------------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements the visit functions for mul, fmul, sdiv, udiv, fdiv, +// srem, urem, frem. +// +//===----------------------------------------------------------------------===// + +#include "InstCombine.h" +#include "llvm/Analysis/InstructionSimplify.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/Support/PatternMatch.h" +using namespace llvm; +using namespace PatternMatch; + + +/// simplifyValueKnownNonZero - The specific integer value is used in a context +/// where it is known to be non-zero. If this allows us to simplify the +/// computation, do so and return the new operand, otherwise return null. +static Value *simplifyValueKnownNonZero(Value *V, InstCombiner &IC) { + // If V has multiple uses, then we would have to do more analysis to determine + // if this is safe. For example, the use could be in dynamically unreached + // code. + if (!V->hasOneUse()) return 0; + + bool MadeChange = false; + + // ((1 << A) >>u B) --> (1 << (A-B)) + // Because V cannot be zero, we know that B is less than A. + Value *A = 0, *B = 0, *PowerOf2 = 0; + if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(PowerOf2), m_Value(A))), + m_Value(B))) && + // The "1" can be any value known to be a power of 2. + isKnownToBeAPowerOfTwo(PowerOf2)) { + A = IC.Builder->CreateSub(A, B); + return IC.Builder->CreateShl(PowerOf2, A); + } + + // (PowerOfTwo >>u B) --> isExact since shifting out the result would make it + // inexact. Similarly for <<. + if (BinaryOperator *I = dyn_cast<BinaryOperator>(V)) + if (I->isLogicalShift() && isKnownToBeAPowerOfTwo(I->getOperand(0))) { + // We know that this is an exact/nuw shift and that the input is a + // non-zero context as well. + if (Value *V2 = simplifyValueKnownNonZero(I->getOperand(0), IC)) { + I->setOperand(0, V2); + MadeChange = true; + } + + if (I->getOpcode() == Instruction::LShr && !I->isExact()) { + I->setIsExact(); + MadeChange = true; + } + + if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) { + I->setHasNoUnsignedWrap(); + MadeChange = true; + } + } + + // TODO: Lots more we could do here: + // If V is a phi node, we can call this on each of its operands. + // "select cond, X, 0" can simplify to "X". + + return MadeChange ? V : 0; +} + + +/// MultiplyOverflows - True if the multiply can not be expressed in an int +/// this size. +static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) { + uint32_t W = C1->getBitWidth(); + APInt LHSExt = C1->getValue(), RHSExt = C2->getValue(); + if (sign) { + LHSExt = LHSExt.sext(W * 2); + RHSExt = RHSExt.sext(W * 2); + } else { + LHSExt = LHSExt.zext(W * 2); + RHSExt = RHSExt.zext(W * 2); + } + + APInt MulExt = LHSExt * RHSExt; + + if (!sign) + return MulExt.ugt(APInt::getLowBitsSet(W * 2, W)); + + APInt Min = APInt::getSignedMinValue(W).sext(W * 2); + APInt Max = APInt::getSignedMaxValue(W).sext(W * 2); + return MulExt.slt(Min) || MulExt.sgt(Max); +} + +Instruction *InstCombiner::visitMul(BinaryOperator &I) { + bool Changed = SimplifyAssociativeOrCommutative(I); + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifyMulInst(Op0, Op1, TD)) + return ReplaceInstUsesWith(I, V); + + if (Value *V = SimplifyUsingDistributiveLaws(I)) + return ReplaceInstUsesWith(I, V); + + if (match(Op1, m_AllOnes())) // X * -1 == 0 - X + return BinaryOperator::CreateNeg(Op0, I.getName()); + + if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) { + + // ((X << C1)*C2) == (X * (C2 << C1)) + if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op0)) + if (SI->getOpcode() == Instruction::Shl) + if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1))) + return BinaryOperator::CreateMul(SI->getOperand(0), + ConstantExpr::getShl(CI, ShOp)); + + const APInt &Val = CI->getValue(); + if (Val.isPowerOf2()) { // Replace X*(2^C) with X << C + Constant *NewCst = ConstantInt::get(Op0->getType(), Val.logBase2()); + BinaryOperator *Shl = BinaryOperator::CreateShl(Op0, NewCst); + if (I.hasNoSignedWrap()) Shl->setHasNoSignedWrap(); + if (I.hasNoUnsignedWrap()) Shl->setHasNoUnsignedWrap(); + return Shl; + } + + // Canonicalize (X+C1)*CI -> X*CI+C1*CI. + { Value *X; ConstantInt *C1; + if (Op0->hasOneUse() && + match(Op0, m_Add(m_Value(X), m_ConstantInt(C1)))) { + Value *Add = Builder->CreateMul(X, CI); + return BinaryOperator::CreateAdd(Add, Builder->CreateMul(C1, CI)); + } + } + + // (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n + // (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n + // The "* (2**n)" thus becomes a potential shifting opportunity. + { + const APInt & Val = CI->getValue(); + const APInt &PosVal = Val.abs(); + if (Val.isNegative() && PosVal.isPowerOf2()) { + Value *X = 0, *Y = 0; + if (Op0->hasOneUse()) { + ConstantInt *C1; + Value *Sub = 0; + if (match(Op0, m_Sub(m_Value(Y), m_Value(X)))) + Sub = Builder->CreateSub(X, Y, "suba"); + else if (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1)))) + Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc"); + if (Sub) + return + BinaryOperator::CreateMul(Sub, + ConstantInt::get(Y->getType(), PosVal)); + } + } + } + } + + // Simplify mul instructions with a constant RHS. + if (isa<Constant>(Op1)) { + // Try to fold constant mul into select arguments. + if (SelectInst *SI = dyn_cast<SelectInst>(Op0)) + if (Instruction *R = FoldOpIntoSelect(I, SI)) + return R; + + if (isa<PHINode>(Op0)) + if (Instruction *NV = FoldOpIntoPhi(I)) + return NV; + } + + if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y + if (Value *Op1v = dyn_castNegVal(Op1)) + return BinaryOperator::CreateMul(Op0v, Op1v); + + // (X / Y) * Y = X - (X % Y) + // (X / Y) * -Y = (X % Y) - X + { + Value *Op1C = Op1; + BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0); + if (!BO || + (BO->getOpcode() != Instruction::UDiv && + BO->getOpcode() != Instruction::SDiv)) { + Op1C = Op0; + BO = dyn_cast<BinaryOperator>(Op1); + } + Value *Neg = dyn_castNegVal(Op1C); + if (BO && BO->hasOneUse() && + (BO->getOperand(1) == Op1C || BO->getOperand(1) == Neg) && + (BO->getOpcode() == Instruction::UDiv || + BO->getOpcode() == Instruction::SDiv)) { + Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1); + + // If the division is exact, X % Y is zero, so we end up with X or -X. + if (PossiblyExactOperator *SDiv = dyn_cast<PossiblyExactOperator>(BO)) + if (SDiv->isExact()) { + if (Op1BO == Op1C) + return ReplaceInstUsesWith(I, Op0BO); + return BinaryOperator::CreateNeg(Op0BO); + } + + Value *Rem; + if (BO->getOpcode() == Instruction::UDiv) + Rem = Builder->CreateURem(Op0BO, Op1BO); + else + Rem = Builder->CreateSRem(Op0BO, Op1BO); + Rem->takeName(BO); + + if (Op1BO == Op1C) + return BinaryOperator::CreateSub(Op0BO, Rem); + return BinaryOperator::CreateSub(Rem, Op0BO); + } + } + + /// i1 mul -> i1 and. + if (I.getType()->isIntegerTy(1)) + return BinaryOperator::CreateAnd(Op0, Op1); + + // X*(1 << Y) --> X << Y + // (1 << Y)*X --> X << Y + { + Value *Y; + if (match(Op0, m_Shl(m_One(), m_Value(Y)))) + return BinaryOperator::CreateShl(Op1, Y); + if (match(Op1, m_Shl(m_One(), m_Value(Y)))) + return BinaryOperator::CreateShl(Op0, Y); + } + + // If one of the operands of the multiply is a cast from a boolean value, then + // we know the bool is either zero or one, so this is a 'masking' multiply. + // X * Y (where Y is 0 or 1) -> X & (0-Y) + if (!I.getType()->isVectorTy()) { + // -2 is "-1 << 1" so it is all bits set except the low one. + APInt Negative2(I.getType()->getPrimitiveSizeInBits(), (uint64_t)-2, true); + + Value *BoolCast = 0, *OtherOp = 0; + if (MaskedValueIsZero(Op0, Negative2)) + BoolCast = Op0, OtherOp = Op1; + else if (MaskedValueIsZero(Op1, Negative2)) + BoolCast = Op1, OtherOp = Op0; + + if (BoolCast) { + Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()), + BoolCast); + return BinaryOperator::CreateAnd(V, OtherOp); + } + } + + return Changed ? &I : 0; +} + +// +// Detect pattern: +// +// log2(Y*0.5) +// +// And check for corresponding fast math flags +// + +static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) { + + if (!Op->hasOneUse()) + return; + + IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op); + if (!II) + return; + if (II->getIntrinsicID() != Intrinsic::log2 || !II->hasUnsafeAlgebra()) + return; + Log2 = II; + + Value *OpLog2Of = II->getArgOperand(0); + if (!OpLog2Of->hasOneUse()) + return; + + Instruction *I = dyn_cast<Instruction>(OpLog2Of); + if (!I) + return; + if (I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra()) + return; + + ConstantFP *CFP = dyn_cast<ConstantFP>(I->getOperand(0)); + if (CFP && CFP->isExactlyValue(0.5)) { + Y = I->getOperand(1); + return; + } + CFP = dyn_cast<ConstantFP>(I->getOperand(1)); + if (CFP && CFP->isExactlyValue(0.5)) + Y = I->getOperand(0); +} + +/// Helper function of InstCombiner::visitFMul(BinaryOperator(). It returns +/// true iff the given value is FMul or FDiv with one and only one operand +/// being a normal constant (i.e. not Zero/NaN/Infinity). +static bool isFMulOrFDivWithConstant(Value *V) { + Instruction *I = dyn_cast<Instruction>(V); + if (!I || (I->getOpcode() != Instruction::FMul && + I->getOpcode() != Instruction::FDiv)) + return false; + + ConstantFP *C0 = dyn_cast<ConstantFP>(I->getOperand(0)); + ConstantFP *C1 = dyn_cast<ConstantFP>(I->getOperand(1)); + + if (C0 && C1) + return false; + + return (C0 && C0->getValueAPF().isNormal()) || + (C1 && C1->getValueAPF().isNormal()); +} + +static bool isNormalFp(const ConstantFP *C) { + const APFloat &Flt = C->getValueAPF(); + return Flt.isNormal() && !Flt.isDenormal(); +} + +/// foldFMulConst() is a helper routine of InstCombiner::visitFMul(). +/// The input \p FMulOrDiv is a FMul/FDiv with one and only one operand +/// being a constant (i.e. isFMulOrFDivWithConstant(FMulOrDiv) == true). +/// This function is to simplify "FMulOrDiv * C" and returns the +/// resulting expression. Note that this function could return NULL in +/// case the constants cannot be folded into a normal floating-point. +/// +Value *InstCombiner::foldFMulConst(Instruction *FMulOrDiv, ConstantFP *C, + Instruction *InsertBefore) { + assert(isFMulOrFDivWithConstant(FMulOrDiv) && "V is invalid"); + + Value *Opnd0 = FMulOrDiv->getOperand(0); + Value *Opnd1 = FMulOrDiv->getOperand(1); + + ConstantFP *C0 = dyn_cast<ConstantFP>(Opnd0); + ConstantFP *C1 = dyn_cast<ConstantFP>(Opnd1); + + BinaryOperator *R = 0; + + // (X * C0) * C => X * (C0*C) + if (FMulOrDiv->getOpcode() == Instruction::FMul) { + Constant *F = ConstantExpr::getFMul(C1 ? C1 : C0, C); + if (isNormalFp(cast<ConstantFP>(F))) + R = BinaryOperator::CreateFMul(C1 ? Opnd0 : Opnd1, F); + } else { + if (C0) { + // (C0 / X) * C => (C0 * C) / X + ConstantFP *F = cast<ConstantFP>(ConstantExpr::getFMul(C0, C)); + if (isNormalFp(F)) + R = BinaryOperator::CreateFDiv(F, Opnd1); + } else { + // (X / C1) * C => X * (C/C1) if C/C1 is not a denormal + ConstantFP *F = cast<ConstantFP>(ConstantExpr::getFDiv(C, C1)); + if (isNormalFp(F)) { + R = BinaryOperator::CreateFMul(Opnd0, F); + } else { + // (X / C1) * C => X / (C1/C) + Constant *F = ConstantExpr::getFDiv(C1, C); + if (isNormalFp(cast<ConstantFP>(F))) + R = BinaryOperator::CreateFDiv(Opnd0, F); + } + } + } + + if (R) { + R->setHasUnsafeAlgebra(true); + InsertNewInstWith(R, *InsertBefore); + } + + return R; +} + +Instruction *InstCombiner::visitFMul(BinaryOperator &I) { + bool Changed = SimplifyAssociativeOrCommutative(I); + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (isa<Constant>(Op0)) + std::swap(Op0, Op1); + + if (Value *V = SimplifyFMulInst(Op0, Op1, I.getFastMathFlags(), TD)) + return ReplaceInstUsesWith(I, V); + + bool AllowReassociate = I.hasUnsafeAlgebra(); + + // Simplify mul instructions with a constant RHS. + if (isa<Constant>(Op1)) { + // Try to fold constant mul into select arguments. + if (SelectInst *SI = dyn_cast<SelectInst>(Op0)) + if (Instruction *R = FoldOpIntoSelect(I, SI)) + return R; + + if (isa<PHINode>(Op0)) + if (Instruction *NV = FoldOpIntoPhi(I)) + return NV; + + ConstantFP *C = dyn_cast<ConstantFP>(Op1); + if (C && AllowReassociate && C->getValueAPF().isNormal()) { + // Let MDC denote an expression in one of these forms: + // X * C, C/X, X/C, where C is a constant. + // + // Try to simplify "MDC * Constant" + if (isFMulOrFDivWithConstant(Op0)) { + Value *V = foldFMulConst(cast<Instruction>(Op0), C, &I); + if (V) + return ReplaceInstUsesWith(I, V); + } + + // (MDC +/- C1) * C => (MDC * C) +/- (C1 * C) + Instruction *FAddSub = dyn_cast<Instruction>(Op0); + if (FAddSub && + (FAddSub->getOpcode() == Instruction::FAdd || + FAddSub->getOpcode() == Instruction::FSub)) { + Value *Opnd0 = FAddSub->getOperand(0); + Value *Opnd1 = FAddSub->getOperand(1); + ConstantFP *C0 = dyn_cast<ConstantFP>(Opnd0); + ConstantFP *C1 = dyn_cast<ConstantFP>(Opnd1); + bool Swap = false; + if (C0) { + std::swap(C0, C1); + std::swap(Opnd0, Opnd1); + Swap = true; + } + + if (C1 && C1->getValueAPF().isNormal() && + isFMulOrFDivWithConstant(Opnd0)) { + Value *M1 = ConstantExpr::getFMul(C1, C); + Value *M0 = isNormalFp(cast<ConstantFP>(M1)) ? + foldFMulConst(cast<Instruction>(Opnd0), C, &I) : + 0; + if (M0 && M1) { + if (Swap && FAddSub->getOpcode() == Instruction::FSub) + std::swap(M0, M1); + + Value *R = (FAddSub->getOpcode() == Instruction::FAdd) ? + BinaryOperator::CreateFAdd(M0, M1) : + BinaryOperator::CreateFSub(M0, M1); + Instruction *RI = cast<Instruction>(R); + RI->copyFastMathFlags(&I); + return RI; + } + } + } + } + } + + + // Under unsafe algebra do: + // X * log2(0.5*Y) = X*log2(Y) - X + if (I.hasUnsafeAlgebra()) { + Value *OpX = NULL; + Value *OpY = NULL; + IntrinsicInst *Log2; + detectLog2OfHalf(Op0, OpY, Log2); + if (OpY) { + OpX = Op1; + } else { + detectLog2OfHalf(Op1, OpY, Log2); + if (OpY) { + OpX = Op0; + } + } + // if pattern detected emit alternate sequence + if (OpX && OpY) { + Log2->setArgOperand(0, OpY); + Value *FMulVal = Builder->CreateFMul(OpX, Log2); + Instruction *FMul = cast<Instruction>(FMulVal); + FMul->copyFastMathFlags(Log2); + Instruction *FSub = BinaryOperator::CreateFSub(FMulVal, OpX); + FSub->copyFastMathFlags(Log2); + return FSub; + } + } + + // Handle symmetric situation in a 2-iteration loop + Value *Opnd0 = Op0; + Value *Opnd1 = Op1; + for (int i = 0; i < 2; i++) { + bool IgnoreZeroSign = I.hasNoSignedZeros(); + if (BinaryOperator::isFNeg(Opnd0, IgnoreZeroSign)) { + Value *N0 = dyn_castFNegVal(Opnd0, IgnoreZeroSign); + Value *N1 = dyn_castFNegVal(Opnd1, IgnoreZeroSign); + + // -X * -Y => X*Y + if (N1) + return BinaryOperator::CreateFMul(N0, N1); + + if (Opnd0->hasOneUse()) { + // -X * Y => -(X*Y) (Promote negation as high as possible) + Value *T = Builder->CreateFMul(N0, Opnd1); + cast<Instruction>(T)->setDebugLoc(I.getDebugLoc()); + Instruction *Neg = BinaryOperator::CreateFNeg(T); + if (I.getFastMathFlags().any()) { + cast<Instruction>(T)->copyFastMathFlags(&I); + Neg->copyFastMathFlags(&I); + } + return Neg; + } + } + + // (X*Y) * X => (X*X) * Y where Y != X + // The purpose is two-fold: + // 1) to form a power expression (of X). + // 2) potentially shorten the critical path: After transformation, the + // latency of the instruction Y is amortized by the expression of X*X, + // and therefore Y is in a "less critical" position compared to what it + // was before the transformation. + // + if (AllowReassociate) { + Value *Opnd0_0, *Opnd0_1; + if (Opnd0->hasOneUse() && + match(Opnd0, m_FMul(m_Value(Opnd0_0), m_Value(Opnd0_1)))) { + Value *Y = 0; + if (Opnd0_0 == Opnd1 && Opnd0_1 != Opnd1) + Y = Opnd0_1; + else if (Opnd0_1 == Opnd1 && Opnd0_0 != Opnd1) + Y = Opnd0_0; + + if (Y) { + Instruction *T = cast<Instruction>(Builder->CreateFMul(Opnd1, Opnd1)); + T->copyFastMathFlags(&I); + T->setDebugLoc(I.getDebugLoc()); + + Instruction *R = BinaryOperator::CreateFMul(T, Y); + R->copyFastMathFlags(&I); + return R; + } + } + } + + if (!isa<Constant>(Op1)) + std::swap(Opnd0, Opnd1); + else + break; + } + + return Changed ? &I : 0; +} + +/// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select +/// instruction. +bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) { + SelectInst *SI = cast<SelectInst>(I.getOperand(1)); + + // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y + int NonNullOperand = -1; + if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1))) + if (ST->isNullValue()) + NonNullOperand = 2; + // div/rem X, (Cond ? Y : 0) -> div/rem X, Y + if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2))) + if (ST->isNullValue()) + NonNullOperand = 1; + + if (NonNullOperand == -1) + return false; + + Value *SelectCond = SI->getOperand(0); + + // Change the div/rem to use 'Y' instead of the select. + I.setOperand(1, SI->getOperand(NonNullOperand)); + + // Okay, we know we replace the operand of the div/rem with 'Y' with no + // problem. However, the select, or the condition of the select may have + // multiple uses. Based on our knowledge that the operand must be non-zero, + // propagate the known value for the select into other uses of it, and + // propagate a known value of the condition into its other users. + + // If the select and condition only have a single use, don't bother with this, + // early exit. + if (SI->use_empty() && SelectCond->hasOneUse()) + return true; + + // Scan the current block backward, looking for other uses of SI. + BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin(); + + while (BBI != BBFront) { + --BBI; + // If we found a call to a function, we can't assume it will return, so + // information from below it cannot be propagated above it. + if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI)) + break; + + // Replace uses of the select or its condition with the known values. + for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end(); + I != E; ++I) { + if (*I == SI) { + *I = SI->getOperand(NonNullOperand); + Worklist.Add(BBI); + } else if (*I == SelectCond) { + *I = NonNullOperand == 1 ? ConstantInt::getTrue(BBI->getContext()) : + ConstantInt::getFalse(BBI->getContext()); + Worklist.Add(BBI); + } + } + + // If we past the instruction, quit looking for it. + if (&*BBI == SI) + SI = 0; + if (&*BBI == SelectCond) + SelectCond = 0; + + // If we ran out of things to eliminate, break out of the loop. + if (SelectCond == 0 && SI == 0) + break; + + } + return true; +} + + +/// This function implements the transforms common to both integer division +/// instructions (udiv and sdiv). It is called by the visitors to those integer +/// division instructions. +/// @brief Common integer divide transforms +Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + // The RHS is known non-zero. + if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) { + I.setOperand(1, V); + return &I; + } + + // Handle cases involving: [su]div X, (select Cond, Y, Z) + // This does not apply for fdiv. + if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I)) + return &I; + + if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) { + // (X / C1) / C2 -> X / (C1*C2) + if (Instruction *LHS = dyn_cast<Instruction>(Op0)) + if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode()) + if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) { + if (MultiplyOverflows(RHS, LHSRHS, + I.getOpcode()==Instruction::SDiv)) + return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); + return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0), + ConstantExpr::getMul(RHS, LHSRHS)); + } + + if (!RHS->isZero()) { // avoid X udiv 0 + if (SelectInst *SI = dyn_cast<SelectInst>(Op0)) + if (Instruction *R = FoldOpIntoSelect(I, SI)) + return R; + if (isa<PHINode>(Op0)) + if (Instruction *NV = FoldOpIntoPhi(I)) + return NV; + } + } + + // See if we can fold away this div instruction. + if (SimplifyDemandedInstructionBits(I)) + return &I; + + // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y + Value *X = 0, *Z = 0; + if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1 + bool isSigned = I.getOpcode() == Instruction::SDiv; + if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) || + (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1))))) + return BinaryOperator::Create(I.getOpcode(), X, Op1); + } + + return 0; +} + +/// dyn_castZExtVal - Checks if V is a zext or constant that can +/// be truncated to Ty without losing bits. +static Value *dyn_castZExtVal(Value *V, Type *Ty) { + if (ZExtInst *Z = dyn_cast<ZExtInst>(V)) { + if (Z->getSrcTy() == Ty) + return Z->getOperand(0); + } else if (ConstantInt *C = dyn_cast<ConstantInt>(V)) { + if (C->getValue().getActiveBits() <= cast<IntegerType>(Ty)->getBitWidth()) + return ConstantExpr::getTrunc(C, Ty); + } + return 0; +} + +Instruction *InstCombiner::visitUDiv(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifyUDivInst(Op0, Op1, TD)) + return ReplaceInstUsesWith(I, V); + + // Handle the integer div common cases + if (Instruction *Common = commonIDivTransforms(I)) + return Common; + + { + // X udiv 2^C -> X >> C + // Check to see if this is an unsigned division with an exact power of 2, + // if so, convert to a right shift. + const APInt *C; + if (match(Op1, m_Power2(C))) { + BinaryOperator *LShr = + BinaryOperator::CreateLShr(Op0, + ConstantInt::get(Op0->getType(), + C->logBase2())); + if (I.isExact()) LShr->setIsExact(); + return LShr; + } + } + + if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) { + // X udiv C, where C >= signbit + if (C->getValue().isNegative()) { + Value *IC = Builder->CreateICmpULT(Op0, C); + return SelectInst::Create(IC, Constant::getNullValue(I.getType()), + ConstantInt::get(I.getType(), 1)); + } + } + + // (x lshr C1) udiv C2 --> x udiv (C2 << C1) + if (ConstantInt *C2 = dyn_cast<ConstantInt>(Op1)) { + Value *X; + ConstantInt *C1; + if (match(Op0, m_LShr(m_Value(X), m_ConstantInt(C1)))) { + APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1)); + return BinaryOperator::CreateUDiv(X, Builder->getInt(NC)); + } + } + + // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2) + { const APInt *CI; Value *N; + if (match(Op1, m_Shl(m_Power2(CI), m_Value(N))) || + match(Op1, m_ZExt(m_Shl(m_Power2(CI), m_Value(N))))) { + if (*CI != 1) + N = Builder->CreateAdd(N, + ConstantInt::get(N->getType(), CI->logBase2())); + if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1)) + N = Builder->CreateZExt(N, Z->getDestTy()); + if (I.isExact()) + return BinaryOperator::CreateExactLShr(Op0, N); + return BinaryOperator::CreateLShr(Op0, N); + } + } + + // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2) + // where C1&C2 are powers of two. + { Value *Cond; const APInt *C1, *C2; + if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) { + // Construct the "on true" case of the select + Value *TSI = Builder->CreateLShr(Op0, C1->logBase2(), Op1->getName()+".t", + I.isExact()); + + // Construct the "on false" case of the select + Value *FSI = Builder->CreateLShr(Op0, C2->logBase2(), Op1->getName()+".f", + I.isExact()); + + // construct the select instruction and return it. + return SelectInst::Create(Cond, TSI, FSI); + } + } + + // (zext A) udiv (zext B) --> zext (A udiv B) + if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0)) + if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy())) + return new ZExtInst(Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div", + I.isExact()), + I.getType()); + + return 0; +} + +Instruction *InstCombiner::visitSDiv(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifySDivInst(Op0, Op1, TD)) + return ReplaceInstUsesWith(I, V); + + // Handle the integer div common cases + if (Instruction *Common = commonIDivTransforms(I)) + return Common; + + if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) { + // sdiv X, -1 == -X + if (RHS->isAllOnesValue()) + return BinaryOperator::CreateNeg(Op0); + + // sdiv X, C --> ashr exact X, log2(C) + if (I.isExact() && RHS->getValue().isNonNegative() && + RHS->getValue().isPowerOf2()) { + Value *ShAmt = llvm::ConstantInt::get(RHS->getType(), + RHS->getValue().exactLogBase2()); + return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName()); + } + + // -X/C --> X/-C provided the negation doesn't overflow. + if (SubOperator *Sub = dyn_cast<SubOperator>(Op0)) + if (match(Sub->getOperand(0), m_Zero()) && Sub->hasNoSignedWrap()) + return BinaryOperator::CreateSDiv(Sub->getOperand(1), + ConstantExpr::getNeg(RHS)); + } + + // If the sign bits of both operands are zero (i.e. we can prove they are + // unsigned inputs), turn this into a udiv. + if (I.getType()->isIntegerTy()) { + APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits())); + if (MaskedValueIsZero(Op0, Mask)) { + if (MaskedValueIsZero(Op1, Mask)) { + // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set + return BinaryOperator::CreateUDiv(Op0, Op1, I.getName()); + } + + if (match(Op1, m_Shl(m_Power2(), m_Value()))) { + // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y) + // Safe because the only negative value (1 << Y) can take on is + // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have + // the sign bit set. + return BinaryOperator::CreateUDiv(Op0, Op1, I.getName()); + } + } + } + + return 0; +} + +/// CvtFDivConstToReciprocal tries to convert X/C into X*1/C if C not a special +/// FP value and: +/// 1) 1/C is exact, or +/// 2) reciprocal is allowed. +/// If the convertion was successful, the simplified expression "X * 1/C" is +/// returned; otherwise, NULL is returned. +/// +static Instruction *CvtFDivConstToReciprocal(Value *Dividend, + ConstantFP *Divisor, + bool AllowReciprocal) { + const APFloat &FpVal = Divisor->getValueAPF(); + APFloat Reciprocal(FpVal.getSemantics()); + bool Cvt = FpVal.getExactInverse(&Reciprocal); + + if (!Cvt && AllowReciprocal && FpVal.isNormal()) { + Reciprocal = APFloat(FpVal.getSemantics(), 1.0f); + (void)Reciprocal.divide(FpVal, APFloat::rmNearestTiesToEven); + Cvt = !Reciprocal.isDenormal(); + } + + if (!Cvt) + return 0; + + ConstantFP *R; + R = ConstantFP::get(Dividend->getType()->getContext(), Reciprocal); + return BinaryOperator::CreateFMul(Dividend, R); +} + +Instruction *InstCombiner::visitFDiv(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifyFDivInst(Op0, Op1, TD)) + return ReplaceInstUsesWith(I, V); + + bool AllowReassociate = I.hasUnsafeAlgebra(); + bool AllowReciprocal = I.hasAllowReciprocal(); + + if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) { + if (AllowReassociate) { + ConstantFP *C1 = 0; + ConstantFP *C2 = Op1C; + Value *X; + Instruction *Res = 0; + + if (match(Op0, m_FMul(m_Value(X), m_ConstantFP(C1)))) { + // (X*C1)/C2 => X * (C1/C2) + // + Constant *C = ConstantExpr::getFDiv(C1, C2); + const APFloat &F = cast<ConstantFP>(C)->getValueAPF(); + if (F.isNormal() && !F.isDenormal()) + Res = BinaryOperator::CreateFMul(X, C); + } else if (match(Op0, m_FDiv(m_Value(X), m_ConstantFP(C1)))) { + // (X/C1)/C2 => X /(C2*C1) [=> X * 1/(C2*C1) if reciprocal is allowed] + // + Constant *C = ConstantExpr::getFMul(C1, C2); + const APFloat &F = cast<ConstantFP>(C)->getValueAPF(); + if (F.isNormal() && !F.isDenormal()) { + Res = CvtFDivConstToReciprocal(X, cast<ConstantFP>(C), + AllowReciprocal); + if (!Res) + Res = BinaryOperator::CreateFDiv(X, C); + } + } + + if (Res) { + Res->setFastMathFlags(I.getFastMathFlags()); + return Res; + } + } + + // X / C => X * 1/C + if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal)) + return T; + + return 0; + } + + if (AllowReassociate && isa<ConstantFP>(Op0)) { + ConstantFP *C1 = cast<ConstantFP>(Op0), *C2; + Constant *Fold = 0; + Value *X; + bool CreateDiv = true; + + // C1 / (X*C2) => (C1/C2) / X + if (match(Op1, m_FMul(m_Value(X), m_ConstantFP(C2)))) + Fold = ConstantExpr::getFDiv(C1, C2); + else if (match(Op1, m_FDiv(m_Value(X), m_ConstantFP(C2)))) { + // C1 / (X/C2) => (C1*C2) / X + Fold = ConstantExpr::getFMul(C1, C2); + } else if (match(Op1, m_FDiv(m_ConstantFP(C2), m_Value(X)))) { + // C1 / (C2/X) => (C1/C2) * X + Fold = ConstantExpr::getFDiv(C1, C2); + CreateDiv = false; + } + + if (Fold) { + const APFloat &FoldC = cast<ConstantFP>(Fold)->getValueAPF(); + if (FoldC.isNormal() && !FoldC.isDenormal()) { + Instruction *R = CreateDiv ? + BinaryOperator::CreateFDiv(Fold, X) : + BinaryOperator::CreateFMul(X, Fold); + R->setFastMathFlags(I.getFastMathFlags()); + return R; + } + } + return 0; + } + + if (AllowReassociate) { + Value *X, *Y; + Value *NewInst = 0; + Instruction *SimpR = 0; + + if (Op0->hasOneUse() && match(Op0, m_FDiv(m_Value(X), m_Value(Y)))) { + // (X/Y) / Z => X / (Y*Z) + // + if (!isa<ConstantFP>(Y) || !isa<ConstantFP>(Op1)) { + NewInst = Builder->CreateFMul(Y, Op1); + SimpR = BinaryOperator::CreateFDiv(X, NewInst); + } + } else if (Op1->hasOneUse() && match(Op1, m_FDiv(m_Value(X), m_Value(Y)))) { + // Z / (X/Y) => Z*Y / X + // + if (!isa<ConstantFP>(Y) || !isa<ConstantFP>(Op0)) { + NewInst = Builder->CreateFMul(Op0, Y); + SimpR = BinaryOperator::CreateFDiv(NewInst, X); + } + } + + if (NewInst) { + if (Instruction *T = dyn_cast<Instruction>(NewInst)) + T->setDebugLoc(I.getDebugLoc()); + SimpR->setFastMathFlags(I.getFastMathFlags()); + return SimpR; + } + } + + return 0; +} + +/// This function implements the transforms common to both integer remainder +/// instructions (urem and srem). It is called by the visitors to those integer +/// remainder instructions. +/// @brief Common integer remainder transforms +Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + // The RHS is known non-zero. + if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) { + I.setOperand(1, V); + return &I; + } + + // Handle cases involving: rem X, (select Cond, Y, Z) + if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I)) + return &I; + + if (isa<ConstantInt>(Op1)) { + if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) { + if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) { + if (Instruction *R = FoldOpIntoSelect(I, SI)) + return R; + } else if (isa<PHINode>(Op0I)) { + if (Instruction *NV = FoldOpIntoPhi(I)) + return NV; + } + + // See if we can fold away this rem instruction. + if (SimplifyDemandedInstructionBits(I)) + return &I; + } + } + + return 0; +} + +Instruction *InstCombiner::visitURem(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifyURemInst(Op0, Op1, TD)) + return ReplaceInstUsesWith(I, V); + + if (Instruction *common = commonIRemTransforms(I)) + return common; + + // X urem C^2 -> X and C-1 + { const APInt *C; + if (match(Op1, m_Power2(C))) + return BinaryOperator::CreateAnd(Op0, + ConstantInt::get(I.getType(), *C-1)); + } + + // Turn A % (C << N), where C is 2^k, into A & ((C << N)-1) + if (match(Op1, m_Shl(m_Power2(), m_Value()))) { + Constant *N1 = Constant::getAllOnesValue(I.getType()); + Value *Add = Builder->CreateAdd(Op1, N1); + return BinaryOperator::CreateAnd(Op0, Add); + } + + // urem X, (select Cond, 2^C1, 2^C2) --> + // select Cond, (and X, C1-1), (and X, C2-1) + // when C1&C2 are powers of two. + { Value *Cond; const APInt *C1, *C2; + if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) { + Value *TrueAnd = Builder->CreateAnd(Op0, *C1-1, Op1->getName()+".t"); + Value *FalseAnd = Builder->CreateAnd(Op0, *C2-1, Op1->getName()+".f"); + return SelectInst::Create(Cond, TrueAnd, FalseAnd); + } + } + + // (zext A) urem (zext B) --> zext (A urem B) + if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0)) + if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy())) + return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1), + I.getType()); + + return 0; +} + +Instruction *InstCombiner::visitSRem(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifySRemInst(Op0, Op1, TD)) + return ReplaceInstUsesWith(I, V); + + // Handle the integer rem common cases + if (Instruction *Common = commonIRemTransforms(I)) + return Common; + + if (Value *RHSNeg = dyn_castNegVal(Op1)) + if (!isa<Constant>(RHSNeg) || + (isa<ConstantInt>(RHSNeg) && + cast<ConstantInt>(RHSNeg)->getValue().isStrictlyPositive())) { + // X % -Y -> X % Y + Worklist.AddValue(I.getOperand(1)); + I.setOperand(1, RHSNeg); + return &I; + } + + // If the sign bits of both operands are zero (i.e. we can prove they are + // unsigned inputs), turn this into a urem. + if (I.getType()->isIntegerTy()) { + APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits())); + if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) { + // X srem Y -> X urem Y, iff X and Y don't have sign bit set + return BinaryOperator::CreateURem(Op0, Op1, I.getName()); + } + } + + // If it's a constant vector, flip any negative values positive. + if (isa<ConstantVector>(Op1) || isa<ConstantDataVector>(Op1)) { + Constant *C = cast<Constant>(Op1); + unsigned VWidth = C->getType()->getVectorNumElements(); + + bool hasNegative = false; + bool hasMissing = false; + for (unsigned i = 0; i != VWidth; ++i) { + Constant *Elt = C->getAggregateElement(i); + if (Elt == 0) { + hasMissing = true; + break; + } + + if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elt)) + if (RHS->isNegative()) + hasNegative = true; + } + + if (hasNegative && !hasMissing) { + SmallVector<Constant *, 16> Elts(VWidth); + for (unsigned i = 0; i != VWidth; ++i) { + Elts[i] = C->getAggregateElement(i); // Handle undef, etc. + if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elts[i])) { + if (RHS->isNegative()) + Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS)); + } + } + + Constant *NewRHSV = ConstantVector::get(Elts); + if (NewRHSV != C) { // Don't loop on -MININT + Worklist.AddValue(I.getOperand(1)); + I.setOperand(1, NewRHSV); + return &I; + } + } + } + + return 0; +} + +Instruction *InstCombiner::visitFRem(BinaryOperator &I) { + Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1); + + if (Value *V = SimplifyFRemInst(Op0, Op1, TD)) + return ReplaceInstUsesWith(I, V); + + // Handle cases involving: rem X, (select Cond, Y, Z) + if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I)) + return &I; + + return 0; +} |
