1 //===- InstCombineMulDivRem.cpp -------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the visit functions for mul, fmul, sdiv, udiv, fdiv,
13 //===----------------------------------------------------------------------===//
15 #include "InstCombine.h"
16 #include "llvm/Analysis/InstructionSimplify.h"
17 #include "llvm/IR/IntrinsicInst.h"
18 #include "llvm/Support/PatternMatch.h"
20 using namespace PatternMatch;
23 /// simplifyValueKnownNonZero - The specific integer value is used in a context
24 /// where it is known to be non-zero. If this allows us to simplify the
25 /// computation, do so and return the new operand, otherwise return null.
26 static Value *simplifyValueKnownNonZero(Value *V, InstCombiner &IC) {
27 // If V has multiple uses, then we would have to do more analysis to determine
28 // if this is safe. For example, the use could be in dynamically unreached
30 if (!V->hasOneUse()) return 0;
32 bool MadeChange = false;
34 // ((1 << A) >>u B) --> (1 << (A-B))
35 // Because V cannot be zero, we know that B is less than A.
36 Value *A = 0, *B = 0, *PowerOf2 = 0;
37 if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(PowerOf2), m_Value(A))),
39 // The "1" can be any value known to be a power of 2.
40 isKnownToBeAPowerOfTwo(PowerOf2)) {
41 A = IC.Builder->CreateSub(A, B);
42 return IC.Builder->CreateShl(PowerOf2, A);
45 // (PowerOfTwo >>u B) --> isExact since shifting out the result would make it
46 // inexact. Similarly for <<.
47 if (BinaryOperator *I = dyn_cast<BinaryOperator>(V))
48 if (I->isLogicalShift() && isKnownToBeAPowerOfTwo(I->getOperand(0))) {
49 // We know that this is an exact/nuw shift and that the input is a
50 // non-zero context as well.
51 if (Value *V2 = simplifyValueKnownNonZero(I->getOperand(0), IC)) {
56 if (I->getOpcode() == Instruction::LShr && !I->isExact()) {
61 if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
62 I->setHasNoUnsignedWrap();
67 // TODO: Lots more we could do here:
68 // If V is a phi node, we can call this on each of its operands.
69 // "select cond, X, 0" can simplify to "X".
71 return MadeChange ? V : 0;
75 /// MultiplyOverflows - True if the multiply can not be expressed in an int
77 static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) {
78 uint32_t W = C1->getBitWidth();
79 APInt LHSExt = C1->getValue(), RHSExt = C2->getValue();
81 LHSExt = LHSExt.sext(W * 2);
82 RHSExt = RHSExt.sext(W * 2);
84 LHSExt = LHSExt.zext(W * 2);
85 RHSExt = RHSExt.zext(W * 2);
88 APInt MulExt = LHSExt * RHSExt;
91 return MulExt.ugt(APInt::getLowBitsSet(W * 2, W));
93 APInt Min = APInt::getSignedMinValue(W).sext(W * 2);
94 APInt Max = APInt::getSignedMaxValue(W).sext(W * 2);
95 return MulExt.slt(Min) || MulExt.sgt(Max);
98 /// \brief A helper routine of InstCombiner::visitMul().
100 /// If C is a vector of known powers of 2, then this function returns
101 /// a new vector obtained from C replacing each element with its logBase2.
102 /// Return a null pointer otherwise.
103 static Constant *getLogBase2Vector(ConstantDataVector *CV) {
105 SmallVector<Constant *, 4> Elts;
107 for (unsigned I = 0, E = CV->getNumElements(); I != E; ++I) {
108 Constant *Elt = CV->getElementAsConstant(I);
109 if (!match(Elt, m_APInt(IVal)) || !IVal->isPowerOf2())
111 Elts.push_back(ConstantInt::get(Elt->getType(), IVal->logBase2()));
114 return ConstantVector::get(Elts);
117 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
118 bool Changed = SimplifyAssociativeOrCommutative(I);
119 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
121 if (Value *V = SimplifyMulInst(Op0, Op1, TD))
122 return ReplaceInstUsesWith(I, V);
124 if (Value *V = SimplifyUsingDistributiveLaws(I))
125 return ReplaceInstUsesWith(I, V);
127 if (match(Op1, m_AllOnes())) // X * -1 == 0 - X
128 return BinaryOperator::CreateNeg(Op0, I.getName());
130 // Also allow combining multiply instructions on vectors.
135 if (match(&I, m_Mul(m_Shl(m_Value(NewOp), m_Constant(C2)),
137 match(C1, m_APInt(IVal)))
138 // ((X << C1)*C2) == (X * (C2 << C1))
139 return BinaryOperator::CreateMul(NewOp, ConstantExpr::getShl(C1, C2));
141 if (match(&I, m_Mul(m_Value(NewOp), m_Constant(C1)))) {
142 Constant *NewCst = 0;
143 if (match(C1, m_APInt(IVal)) && IVal->isPowerOf2())
144 // Replace X*(2^C) with X << C, where C is either a scalar or a splat.
145 NewCst = ConstantInt::get(NewOp->getType(), IVal->logBase2());
146 else if (ConstantDataVector *CV = dyn_cast<ConstantDataVector>(C1))
147 // Replace X*(2^C) with X << C, where C is a vector of known
148 // constant powers of 2.
149 NewCst = getLogBase2Vector(CV);
152 BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
153 if (I.hasNoSignedWrap()) Shl->setHasNoSignedWrap();
154 if (I.hasNoUnsignedWrap()) Shl->setHasNoUnsignedWrap();
160 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
161 // Canonicalize (X+C1)*CI -> X*CI+C1*CI.
162 { Value *X; ConstantInt *C1;
163 if (Op0->hasOneUse() &&
164 match(Op0, m_Add(m_Value(X), m_ConstantInt(C1)))) {
165 Value *Add = Builder->CreateMul(X, CI);
166 return BinaryOperator::CreateAdd(Add, Builder->CreateMul(C1, CI));
170 // (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
171 // (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
172 // The "* (2**n)" thus becomes a potential shifting opportunity.
174 const APInt & Val = CI->getValue();
175 const APInt &PosVal = Val.abs();
176 if (Val.isNegative() && PosVal.isPowerOf2()) {
177 Value *X = 0, *Y = 0;
178 if (Op0->hasOneUse()) {
181 if (match(Op0, m_Sub(m_Value(Y), m_Value(X))))
182 Sub = Builder->CreateSub(X, Y, "suba");
183 else if (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))
184 Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc");
187 BinaryOperator::CreateMul(Sub,
188 ConstantInt::get(Y->getType(), PosVal));
194 // Simplify mul instructions with a constant RHS.
195 if (isa<Constant>(Op1)) {
196 // Try to fold constant mul into select arguments.
197 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
198 if (Instruction *R = FoldOpIntoSelect(I, SI))
201 if (isa<PHINode>(Op0))
202 if (Instruction *NV = FoldOpIntoPhi(I))
206 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
207 if (Value *Op1v = dyn_castNegVal(Op1))
208 return BinaryOperator::CreateMul(Op0v, Op1v);
210 // (X / Y) * Y = X - (X % Y)
211 // (X / Y) * -Y = (X % Y) - X
214 BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0);
216 (BO->getOpcode() != Instruction::UDiv &&
217 BO->getOpcode() != Instruction::SDiv)) {
219 BO = dyn_cast<BinaryOperator>(Op1);
221 Value *Neg = dyn_castNegVal(Op1C);
222 if (BO && BO->hasOneUse() &&
223 (BO->getOperand(1) == Op1C || BO->getOperand(1) == Neg) &&
224 (BO->getOpcode() == Instruction::UDiv ||
225 BO->getOpcode() == Instruction::SDiv)) {
226 Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
228 // If the division is exact, X % Y is zero, so we end up with X or -X.
229 if (PossiblyExactOperator *SDiv = dyn_cast<PossiblyExactOperator>(BO))
230 if (SDiv->isExact()) {
232 return ReplaceInstUsesWith(I, Op0BO);
233 return BinaryOperator::CreateNeg(Op0BO);
237 if (BO->getOpcode() == Instruction::UDiv)
238 Rem = Builder->CreateURem(Op0BO, Op1BO);
240 Rem = Builder->CreateSRem(Op0BO, Op1BO);
244 return BinaryOperator::CreateSub(Op0BO, Rem);
245 return BinaryOperator::CreateSub(Rem, Op0BO);
249 /// i1 mul -> i1 and.
250 if (I.getType()->isIntegerTy(1))
251 return BinaryOperator::CreateAnd(Op0, Op1);
253 // X*(1 << Y) --> X << Y
254 // (1 << Y)*X --> X << Y
257 if (match(Op0, m_Shl(m_One(), m_Value(Y))))
258 return BinaryOperator::CreateShl(Op1, Y);
259 if (match(Op1, m_Shl(m_One(), m_Value(Y))))
260 return BinaryOperator::CreateShl(Op0, Y);
263 // If one of the operands of the multiply is a cast from a boolean value, then
264 // we know the bool is either zero or one, so this is a 'masking' multiply.
265 // X * Y (where Y is 0 or 1) -> X & (0-Y)
266 if (!I.getType()->isVectorTy()) {
267 // -2 is "-1 << 1" so it is all bits set except the low one.
268 APInt Negative2(I.getType()->getPrimitiveSizeInBits(), (uint64_t)-2, true);
270 Value *BoolCast = 0, *OtherOp = 0;
271 if (MaskedValueIsZero(Op0, Negative2))
272 BoolCast = Op0, OtherOp = Op1;
273 else if (MaskedValueIsZero(Op1, Negative2))
274 BoolCast = Op1, OtherOp = Op0;
277 Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()),
279 return BinaryOperator::CreateAnd(V, OtherOp);
283 return Changed ? &I : 0;
291 // And check for corresponding fast math flags
294 static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) {
296 if (!Op->hasOneUse())
299 IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op);
302 if (II->getIntrinsicID() != Intrinsic::log2 || !II->hasUnsafeAlgebra())
306 Value *OpLog2Of = II->getArgOperand(0);
307 if (!OpLog2Of->hasOneUse())
310 Instruction *I = dyn_cast<Instruction>(OpLog2Of);
313 if (I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra())
316 ConstantFP *CFP = dyn_cast<ConstantFP>(I->getOperand(0));
317 if (CFP && CFP->isExactlyValue(0.5)) {
318 Y = I->getOperand(1);
321 CFP = dyn_cast<ConstantFP>(I->getOperand(1));
322 if (CFP && CFP->isExactlyValue(0.5))
323 Y = I->getOperand(0);
326 /// Helper function of InstCombiner::visitFMul(BinaryOperator(). It returns
327 /// true iff the given value is FMul or FDiv with one and only one operand
328 /// being a normal constant (i.e. not Zero/NaN/Infinity).
329 static bool isFMulOrFDivWithConstant(Value *V) {
330 Instruction *I = dyn_cast<Instruction>(V);
331 if (!I || (I->getOpcode() != Instruction::FMul &&
332 I->getOpcode() != Instruction::FDiv))
335 ConstantFP *C0 = dyn_cast<ConstantFP>(I->getOperand(0));
336 ConstantFP *C1 = dyn_cast<ConstantFP>(I->getOperand(1));
341 return (C0 && C0->getValueAPF().isFiniteNonZero()) ||
342 (C1 && C1->getValueAPF().isFiniteNonZero());
345 static bool isNormalFp(const ConstantFP *C) {
346 const APFloat &Flt = C->getValueAPF();
347 return Flt.isNormal();
350 /// foldFMulConst() is a helper routine of InstCombiner::visitFMul().
351 /// The input \p FMulOrDiv is a FMul/FDiv with one and only one operand
352 /// being a constant (i.e. isFMulOrFDivWithConstant(FMulOrDiv) == true).
353 /// This function is to simplify "FMulOrDiv * C" and returns the
354 /// resulting expression. Note that this function could return NULL in
355 /// case the constants cannot be folded into a normal floating-point.
357 Value *InstCombiner::foldFMulConst(Instruction *FMulOrDiv, ConstantFP *C,
358 Instruction *InsertBefore) {
359 assert(isFMulOrFDivWithConstant(FMulOrDiv) && "V is invalid");
361 Value *Opnd0 = FMulOrDiv->getOperand(0);
362 Value *Opnd1 = FMulOrDiv->getOperand(1);
364 ConstantFP *C0 = dyn_cast<ConstantFP>(Opnd0);
365 ConstantFP *C1 = dyn_cast<ConstantFP>(Opnd1);
367 BinaryOperator *R = 0;
369 // (X * C0) * C => X * (C0*C)
370 if (FMulOrDiv->getOpcode() == Instruction::FMul) {
371 Constant *F = ConstantExpr::getFMul(C1 ? C1 : C0, C);
372 if (isNormalFp(cast<ConstantFP>(F)))
373 R = BinaryOperator::CreateFMul(C1 ? Opnd0 : Opnd1, F);
376 // (C0 / X) * C => (C0 * C) / X
377 if (FMulOrDiv->hasOneUse()) {
378 // It would otherwise introduce another div.
379 ConstantFP *F = cast<ConstantFP>(ConstantExpr::getFMul(C0, C));
381 R = BinaryOperator::CreateFDiv(F, Opnd1);
384 // (X / C1) * C => X * (C/C1) if C/C1 is not a denormal
385 ConstantFP *F = cast<ConstantFP>(ConstantExpr::getFDiv(C, C1));
387 R = BinaryOperator::CreateFMul(Opnd0, F);
389 // (X / C1) * C => X / (C1/C)
390 Constant *F = ConstantExpr::getFDiv(C1, C);
391 if (isNormalFp(cast<ConstantFP>(F)))
392 R = BinaryOperator::CreateFDiv(Opnd0, F);
398 R->setHasUnsafeAlgebra(true);
399 InsertNewInstWith(R, *InsertBefore);
405 Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
406 bool Changed = SimplifyAssociativeOrCommutative(I);
407 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
409 if (isa<Constant>(Op0))
412 if (Value *V = SimplifyFMulInst(Op0, Op1, I.getFastMathFlags(), TD))
413 return ReplaceInstUsesWith(I, V);
415 bool AllowReassociate = I.hasUnsafeAlgebra();
417 // Simplify mul instructions with a constant RHS.
418 if (isa<Constant>(Op1)) {
419 // Try to fold constant mul into select arguments.
420 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
421 if (Instruction *R = FoldOpIntoSelect(I, SI))
424 if (isa<PHINode>(Op0))
425 if (Instruction *NV = FoldOpIntoPhi(I))
428 ConstantFP *C = dyn_cast<ConstantFP>(Op1);
429 if (C && AllowReassociate && C->getValueAPF().isFiniteNonZero()) {
430 // Let MDC denote an expression in one of these forms:
431 // X * C, C/X, X/C, where C is a constant.
433 // Try to simplify "MDC * Constant"
434 if (isFMulOrFDivWithConstant(Op0)) {
435 Value *V = foldFMulConst(cast<Instruction>(Op0), C, &I);
437 return ReplaceInstUsesWith(I, V);
440 // (MDC +/- C1) * C => (MDC * C) +/- (C1 * C)
441 Instruction *FAddSub = dyn_cast<Instruction>(Op0);
443 (FAddSub->getOpcode() == Instruction::FAdd ||
444 FAddSub->getOpcode() == Instruction::FSub)) {
445 Value *Opnd0 = FAddSub->getOperand(0);
446 Value *Opnd1 = FAddSub->getOperand(1);
447 ConstantFP *C0 = dyn_cast<ConstantFP>(Opnd0);
448 ConstantFP *C1 = dyn_cast<ConstantFP>(Opnd1);
452 std::swap(Opnd0, Opnd1);
456 if (C1 && C1->getValueAPF().isFiniteNonZero() &&
457 isFMulOrFDivWithConstant(Opnd0)) {
458 Value *M1 = ConstantExpr::getFMul(C1, C);
459 Value *M0 = isNormalFp(cast<ConstantFP>(M1)) ?
460 foldFMulConst(cast<Instruction>(Opnd0), C, &I) :
463 if (Swap && FAddSub->getOpcode() == Instruction::FSub)
466 Instruction *RI = (FAddSub->getOpcode() == Instruction::FAdd)
467 ? BinaryOperator::CreateFAdd(M0, M1)
468 : BinaryOperator::CreateFSub(M0, M1);
469 RI->copyFastMathFlags(&I);
478 // Under unsafe algebra do:
479 // X * log2(0.5*Y) = X*log2(Y) - X
480 if (I.hasUnsafeAlgebra()) {
484 detectLog2OfHalf(Op0, OpY, Log2);
488 detectLog2OfHalf(Op1, OpY, Log2);
493 // if pattern detected emit alternate sequence
495 BuilderTy::FastMathFlagGuard Guard(*Builder);
496 Builder->SetFastMathFlags(Log2->getFastMathFlags());
497 Log2->setArgOperand(0, OpY);
498 Value *FMulVal = Builder->CreateFMul(OpX, Log2);
499 Value *FSub = Builder->CreateFSub(FMulVal, OpX);
501 return ReplaceInstUsesWith(I, FSub);
505 // Handle symmetric situation in a 2-iteration loop
508 for (int i = 0; i < 2; i++) {
509 bool IgnoreZeroSign = I.hasNoSignedZeros();
510 if (BinaryOperator::isFNeg(Opnd0, IgnoreZeroSign)) {
511 BuilderTy::FastMathFlagGuard Guard(*Builder);
512 Builder->SetFastMathFlags(I.getFastMathFlags());
514 Value *N0 = dyn_castFNegVal(Opnd0, IgnoreZeroSign);
515 Value *N1 = dyn_castFNegVal(Opnd1, IgnoreZeroSign);
519 return BinaryOperator::CreateFMul(N0, N1);
521 if (Opnd0->hasOneUse()) {
522 // -X * Y => -(X*Y) (Promote negation as high as possible)
523 Value *T = Builder->CreateFMul(N0, Opnd1);
524 Value *Neg = Builder->CreateFNeg(T);
526 return ReplaceInstUsesWith(I, Neg);
530 // (X*Y) * X => (X*X) * Y where Y != X
531 // The purpose is two-fold:
532 // 1) to form a power expression (of X).
533 // 2) potentially shorten the critical path: After transformation, the
534 // latency of the instruction Y is amortized by the expression of X*X,
535 // and therefore Y is in a "less critical" position compared to what it
536 // was before the transformation.
538 if (AllowReassociate) {
539 Value *Opnd0_0, *Opnd0_1;
540 if (Opnd0->hasOneUse() &&
541 match(Opnd0, m_FMul(m_Value(Opnd0_0), m_Value(Opnd0_1)))) {
543 if (Opnd0_0 == Opnd1 && Opnd0_1 != Opnd1)
545 else if (Opnd0_1 == Opnd1 && Opnd0_0 != Opnd1)
549 BuilderTy::FastMathFlagGuard Guard(*Builder);
550 Builder->SetFastMathFlags(I.getFastMathFlags());
551 Value *T = Builder->CreateFMul(Opnd1, Opnd1);
553 Value *R = Builder->CreateFMul(T, Y);
555 return ReplaceInstUsesWith(I, R);
560 // B * (uitofp i1 C) -> select C, B, 0
561 if (I.hasNoNaNs() && I.hasNoInfs() && I.hasNoSignedZeros()) {
562 Value *LHS = Op0, *RHS = Op1;
564 if (!match(RHS, m_UIToFP(m_Value(C))))
567 if (match(RHS, m_UIToFP(m_Value(C))) && C->getType()->isIntegerTy(1)) {
569 Value *Zero = ConstantFP::getNegativeZero(B->getType());
570 return SelectInst::Create(C, B, Zero);
574 // A * (1 - uitofp i1 C) -> select C, 0, A
575 if (I.hasNoNaNs() && I.hasNoInfs() && I.hasNoSignedZeros()) {
576 Value *LHS = Op0, *RHS = Op1;
578 if (!match(RHS, m_FSub(m_FPOne(), m_UIToFP(m_Value(C)))))
581 if (match(RHS, m_FSub(m_FPOne(), m_UIToFP(m_Value(C)))) &&
582 C->getType()->isIntegerTy(1)) {
584 Value *Zero = ConstantFP::getNegativeZero(A->getType());
585 return SelectInst::Create(C, Zero, A);
589 if (!isa<Constant>(Op1))
590 std::swap(Opnd0, Opnd1);
595 return Changed ? &I : 0;
598 /// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
600 bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
601 SelectInst *SI = cast<SelectInst>(I.getOperand(1));
603 // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
604 int NonNullOperand = -1;
605 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
606 if (ST->isNullValue())
608 // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
609 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
610 if (ST->isNullValue())
613 if (NonNullOperand == -1)
616 Value *SelectCond = SI->getOperand(0);
618 // Change the div/rem to use 'Y' instead of the select.
619 I.setOperand(1, SI->getOperand(NonNullOperand));
621 // Okay, we know we replace the operand of the div/rem with 'Y' with no
622 // problem. However, the select, or the condition of the select may have
623 // multiple uses. Based on our knowledge that the operand must be non-zero,
624 // propagate the known value for the select into other uses of it, and
625 // propagate a known value of the condition into its other users.
627 // If the select and condition only have a single use, don't bother with this,
629 if (SI->use_empty() && SelectCond->hasOneUse())
632 // Scan the current block backward, looking for other uses of SI.
633 BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
635 while (BBI != BBFront) {
637 // If we found a call to a function, we can't assume it will return, so
638 // information from below it cannot be propagated above it.
639 if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
642 // Replace uses of the select or its condition with the known values.
643 for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
646 *I = SI->getOperand(NonNullOperand);
648 } else if (*I == SelectCond) {
649 *I = Builder->getInt1(NonNullOperand == 1);
654 // If we past the instruction, quit looking for it.
657 if (&*BBI == SelectCond)
660 // If we ran out of things to eliminate, break out of the loop.
661 if (SelectCond == 0 && SI == 0)
669 /// This function implements the transforms common to both integer division
670 /// instructions (udiv and sdiv). It is called by the visitors to those integer
671 /// division instructions.
672 /// @brief Common integer divide transforms
673 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
674 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
676 // The RHS is known non-zero.
677 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) {
682 // Handle cases involving: [su]div X, (select Cond, Y, Z)
683 // This does not apply for fdiv.
684 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
687 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
688 // (X / C1) / C2 -> X / (C1*C2)
689 if (Instruction *LHS = dyn_cast<Instruction>(Op0))
690 if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode())
691 if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
692 if (MultiplyOverflows(RHS, LHSRHS,
693 I.getOpcode()==Instruction::SDiv))
694 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
695 return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0),
696 ConstantExpr::getMul(RHS, LHSRHS));
699 if (!RHS->isZero()) { // avoid X udiv 0
700 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
701 if (Instruction *R = FoldOpIntoSelect(I, SI))
703 if (isa<PHINode>(Op0))
704 if (Instruction *NV = FoldOpIntoPhi(I))
709 // See if we can fold away this div instruction.
710 if (SimplifyDemandedInstructionBits(I))
713 // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
714 Value *X = 0, *Z = 0;
715 if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
716 bool isSigned = I.getOpcode() == Instruction::SDiv;
717 if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
718 (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
719 return BinaryOperator::Create(I.getOpcode(), X, Op1);
725 /// dyn_castZExtVal - Checks if V is a zext or constant that can
726 /// be truncated to Ty without losing bits.
727 static Value *dyn_castZExtVal(Value *V, Type *Ty) {
728 if (ZExtInst *Z = dyn_cast<ZExtInst>(V)) {
729 if (Z->getSrcTy() == Ty)
730 return Z->getOperand(0);
731 } else if (ConstantInt *C = dyn_cast<ConstantInt>(V)) {
732 if (C->getValue().getActiveBits() <= cast<IntegerType>(Ty)->getBitWidth())
733 return ConstantExpr::getTrunc(C, Ty);
739 const unsigned MaxDepth = 6;
740 typedef Instruction *(*FoldUDivOperandCb)(Value *Op0, Value *Op1,
741 const BinaryOperator &I,
744 /// \brief Used to maintain state for visitUDivOperand().
745 struct UDivFoldAction {
746 FoldUDivOperandCb FoldAction; ///< Informs visitUDiv() how to fold this
747 ///< operand. This can be zero if this action
748 ///< joins two actions together.
750 Value *OperandToFold; ///< Which operand to fold.
752 Instruction *FoldResult; ///< The instruction returned when FoldAction is
755 size_t SelectLHSIdx; ///< Stores the LHS action index if this action
756 ///< joins two actions together.
759 UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand)
760 : FoldAction(FA), OperandToFold(InputOperand), FoldResult(0) {}
761 UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand, size_t SLHS)
762 : FoldAction(FA), OperandToFold(InputOperand), SelectLHSIdx(SLHS) {}
766 // X udiv 2^C -> X >> C
767 static Instruction *foldUDivPow2Cst(Value *Op0, Value *Op1,
768 const BinaryOperator &I, InstCombiner &IC) {
769 const APInt &C = cast<Constant>(Op1)->getUniqueInteger();
770 BinaryOperator *LShr = BinaryOperator::CreateLShr(
771 Op0, ConstantInt::get(Op0->getType(), C.logBase2()));
772 if (I.isExact()) LShr->setIsExact();
776 // X udiv C, where C >= signbit
777 static Instruction *foldUDivNegCst(Value *Op0, Value *Op1,
778 const BinaryOperator &I, InstCombiner &IC) {
779 Value *ICI = IC.Builder->CreateICmpULT(Op0, cast<ConstantInt>(Op1));
781 return SelectInst::Create(ICI, Constant::getNullValue(I.getType()),
782 ConstantInt::get(I.getType(), 1));
785 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
786 static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
788 Instruction *ShiftLeft = cast<Instruction>(Op1);
789 if (isa<ZExtInst>(ShiftLeft))
790 ShiftLeft = cast<Instruction>(ShiftLeft->getOperand(0));
793 cast<Constant>(ShiftLeft->getOperand(0))->getUniqueInteger();
794 Value *N = ShiftLeft->getOperand(1);
796 N = IC.Builder->CreateAdd(N, ConstantInt::get(N->getType(), CI.logBase2()));
797 if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
798 N = IC.Builder->CreateZExt(N, Z->getDestTy());
799 BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N);
800 if (I.isExact()) LShr->setIsExact();
804 // \brief Recursively visits the possible right hand operands of a udiv
805 // instruction, seeing through select instructions, to determine if we can
806 // replace the udiv with something simpler. If we find that an operand is not
807 // able to simplify the udiv, we abort the entire transformation.
808 static size_t visitUDivOperand(Value *Op0, Value *Op1, const BinaryOperator &I,
809 SmallVectorImpl<UDivFoldAction> &Actions,
810 unsigned Depth = 0) {
811 // Check to see if this is an unsigned division with an exact power of 2,
812 // if so, convert to a right shift.
813 if (match(Op1, m_Power2())) {
814 Actions.push_back(UDivFoldAction(foldUDivPow2Cst, Op1));
815 return Actions.size();
818 if (ConstantInt *C = dyn_cast<ConstantInt>(Op1))
819 // X udiv C, where C >= signbit
820 if (C->getValue().isNegative()) {
821 Actions.push_back(UDivFoldAction(foldUDivNegCst, C));
822 return Actions.size();
825 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
826 if (match(Op1, m_Shl(m_Power2(), m_Value())) ||
827 match(Op1, m_ZExt(m_Shl(m_Power2(), m_Value())))) {
828 Actions.push_back(UDivFoldAction(foldUDivShl, Op1));
829 return Actions.size();
832 // The remaining tests are all recursive, so bail out if we hit the limit.
833 if (Depth++ == MaxDepth)
836 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
837 if (size_t LHSIdx = visitUDivOperand(Op0, SI->getOperand(1), I, Actions))
838 if (visitUDivOperand(Op0, SI->getOperand(2), I, Actions)) {
839 Actions.push_back(UDivFoldAction((FoldUDivOperandCb)0, Op1, LHSIdx-1));
840 return Actions.size();
846 Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
847 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
849 if (Value *V = SimplifyUDivInst(Op0, Op1, TD))
850 return ReplaceInstUsesWith(I, V);
852 // Handle the integer div common cases
853 if (Instruction *Common = commonIDivTransforms(I))
856 // (x lshr C1) udiv C2 --> x udiv (C2 << C1)
857 if (ConstantInt *C2 = dyn_cast<ConstantInt>(Op1)) {
860 if (match(Op0, m_LShr(m_Value(X), m_ConstantInt(C1)))) {
861 APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1));
862 return BinaryOperator::CreateUDiv(X, Builder->getInt(NC));
866 // (zext A) udiv (zext B) --> zext (A udiv B)
867 if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
868 if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
869 return new ZExtInst(Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div",
873 // (LHS udiv (select (select (...)))) -> (LHS >> (select (select (...))))
874 SmallVector<UDivFoldAction, 6> UDivActions;
875 if (visitUDivOperand(Op0, Op1, I, UDivActions))
876 for (unsigned i = 0, e = UDivActions.size(); i != e; ++i) {
877 FoldUDivOperandCb Action = UDivActions[i].FoldAction;
878 Value *ActionOp1 = UDivActions[i].OperandToFold;
881 Inst = Action(Op0, ActionOp1, I, *this);
883 // This action joins two actions together. The RHS of this action is
884 // simply the last action we processed, we saved the LHS action index in
885 // the joining action.
886 size_t SelectRHSIdx = i - 1;
887 Value *SelectRHS = UDivActions[SelectRHSIdx].FoldResult;
888 size_t SelectLHSIdx = UDivActions[i].SelectLHSIdx;
889 Value *SelectLHS = UDivActions[SelectLHSIdx].FoldResult;
890 Inst = SelectInst::Create(cast<SelectInst>(ActionOp1)->getCondition(),
891 SelectLHS, SelectRHS);
894 // If this is the last action to process, return it to the InstCombiner.
895 // Otherwise, we insert it before the UDiv and record it so that we may
896 // use it as part of a joining action (i.e., a SelectInst).
898 Inst->insertBefore(&I);
899 UDivActions[i].FoldResult = Inst;
907 Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
908 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
910 if (Value *V = SimplifySDivInst(Op0, Op1, TD))
911 return ReplaceInstUsesWith(I, V);
913 // Handle the integer div common cases
914 if (Instruction *Common = commonIDivTransforms(I))
917 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
919 if (RHS->isAllOnesValue())
920 return BinaryOperator::CreateNeg(Op0);
922 // sdiv X, C --> ashr exact X, log2(C)
923 if (I.isExact() && RHS->getValue().isNonNegative() &&
924 RHS->getValue().isPowerOf2()) {
925 Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
926 RHS->getValue().exactLogBase2());
927 return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName());
930 // -X/C --> X/-C provided the negation doesn't overflow.
931 if (SubOperator *Sub = dyn_cast<SubOperator>(Op0))
932 if (match(Sub->getOperand(0), m_Zero()) && Sub->hasNoSignedWrap())
933 return BinaryOperator::CreateSDiv(Sub->getOperand(1),
934 ConstantExpr::getNeg(RHS));
937 // If the sign bits of both operands are zero (i.e. we can prove they are
938 // unsigned inputs), turn this into a udiv.
939 if (I.getType()->isIntegerTy()) {
940 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
941 if (MaskedValueIsZero(Op0, Mask)) {
942 if (MaskedValueIsZero(Op1, Mask)) {
943 // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
944 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
947 if (match(Op1, m_Shl(m_Power2(), m_Value()))) {
948 // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
949 // Safe because the only negative value (1 << Y) can take on is
950 // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
952 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
960 /// CvtFDivConstToReciprocal tries to convert X/C into X*1/C if C not a special
962 /// 1) 1/C is exact, or
963 /// 2) reciprocal is allowed.
964 /// If the conversion was successful, the simplified expression "X * 1/C" is
965 /// returned; otherwise, NULL is returned.
967 static Instruction *CvtFDivConstToReciprocal(Value *Dividend,
969 bool AllowReciprocal) {
970 const APFloat &FpVal = Divisor->getValueAPF();
971 APFloat Reciprocal(FpVal.getSemantics());
972 bool Cvt = FpVal.getExactInverse(&Reciprocal);
974 if (!Cvt && AllowReciprocal && FpVal.isFiniteNonZero()) {
975 Reciprocal = APFloat(FpVal.getSemantics(), 1.0f);
976 (void)Reciprocal.divide(FpVal, APFloat::rmNearestTiesToEven);
977 Cvt = !Reciprocal.isDenormal();
984 R = ConstantFP::get(Dividend->getType()->getContext(), Reciprocal);
985 return BinaryOperator::CreateFMul(Dividend, R);
988 Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
989 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
991 if (Value *V = SimplifyFDivInst(Op0, Op1, TD))
992 return ReplaceInstUsesWith(I, V);
994 if (isa<Constant>(Op0))
995 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
996 if (Instruction *R = FoldOpIntoSelect(I, SI))
999 bool AllowReassociate = I.hasUnsafeAlgebra();
1000 bool AllowReciprocal = I.hasAllowReciprocal();
1002 if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) {
1003 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1004 if (Instruction *R = FoldOpIntoSelect(I, SI))
1007 if (AllowReassociate) {
1009 ConstantFP *C2 = Op1C;
1011 Instruction *Res = 0;
1013 if (match(Op0, m_FMul(m_Value(X), m_ConstantFP(C1)))) {
1014 // (X*C1)/C2 => X * (C1/C2)
1016 Constant *C = ConstantExpr::getFDiv(C1, C2);
1017 const APFloat &F = cast<ConstantFP>(C)->getValueAPF();
1019 Res = BinaryOperator::CreateFMul(X, C);
1020 } else if (match(Op0, m_FDiv(m_Value(X), m_ConstantFP(C1)))) {
1021 // (X/C1)/C2 => X /(C2*C1) [=> X * 1/(C2*C1) if reciprocal is allowed]
1023 Constant *C = ConstantExpr::getFMul(C1, C2);
1024 const APFloat &F = cast<ConstantFP>(C)->getValueAPF();
1026 Res = CvtFDivConstToReciprocal(X, cast<ConstantFP>(C),
1029 Res = BinaryOperator::CreateFDiv(X, C);
1034 Res->setFastMathFlags(I.getFastMathFlags());
1040 if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal))
1046 if (AllowReassociate && isa<ConstantFP>(Op0)) {
1047 ConstantFP *C1 = cast<ConstantFP>(Op0), *C2;
1050 bool CreateDiv = true;
1052 // C1 / (X*C2) => (C1/C2) / X
1053 if (match(Op1, m_FMul(m_Value(X), m_ConstantFP(C2))))
1054 Fold = ConstantExpr::getFDiv(C1, C2);
1055 else if (match(Op1, m_FDiv(m_Value(X), m_ConstantFP(C2)))) {
1056 // C1 / (X/C2) => (C1*C2) / X
1057 Fold = ConstantExpr::getFMul(C1, C2);
1058 } else if (match(Op1, m_FDiv(m_ConstantFP(C2), m_Value(X)))) {
1059 // C1 / (C2/X) => (C1/C2) * X
1060 Fold = ConstantExpr::getFDiv(C1, C2);
1065 const APFloat &FoldC = cast<ConstantFP>(Fold)->getValueAPF();
1066 if (FoldC.isNormal()) {
1067 Instruction *R = CreateDiv ?
1068 BinaryOperator::CreateFDiv(Fold, X) :
1069 BinaryOperator::CreateFMul(X, Fold);
1070 R->setFastMathFlags(I.getFastMathFlags());
1077 if (AllowReassociate) {
1080 Instruction *SimpR = 0;
1082 if (Op0->hasOneUse() && match(Op0, m_FDiv(m_Value(X), m_Value(Y)))) {
1083 // (X/Y) / Z => X / (Y*Z)
1085 if (!isa<ConstantFP>(Y) || !isa<ConstantFP>(Op1)) {
1086 NewInst = Builder->CreateFMul(Y, Op1);
1087 SimpR = BinaryOperator::CreateFDiv(X, NewInst);
1089 } else if (Op1->hasOneUse() && match(Op1, m_FDiv(m_Value(X), m_Value(Y)))) {
1090 // Z / (X/Y) => Z*Y / X
1092 if (!isa<ConstantFP>(Y) || !isa<ConstantFP>(Op0)) {
1093 NewInst = Builder->CreateFMul(Op0, Y);
1094 SimpR = BinaryOperator::CreateFDiv(NewInst, X);
1099 if (Instruction *T = dyn_cast<Instruction>(NewInst))
1100 T->setDebugLoc(I.getDebugLoc());
1101 SimpR->setFastMathFlags(I.getFastMathFlags());
1109 /// This function implements the transforms common to both integer remainder
1110 /// instructions (urem and srem). It is called by the visitors to those integer
1111 /// remainder instructions.
1112 /// @brief Common integer remainder transforms
1113 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
1114 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1116 // The RHS is known non-zero.
1117 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) {
1122 // Handle cases involving: rem X, (select Cond, Y, Z)
1123 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
1126 if (isa<ConstantInt>(Op1)) {
1127 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1128 if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
1129 if (Instruction *R = FoldOpIntoSelect(I, SI))
1131 } else if (isa<PHINode>(Op0I)) {
1132 if (Instruction *NV = FoldOpIntoPhi(I))
1136 // See if we can fold away this rem instruction.
1137 if (SimplifyDemandedInstructionBits(I))
1145 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
1146 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1148 if (Value *V = SimplifyURemInst(Op0, Op1, TD))
1149 return ReplaceInstUsesWith(I, V);
1151 if (Instruction *common = commonIRemTransforms(I))
1154 // (zext A) urem (zext B) --> zext (A urem B)
1155 if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
1156 if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
1157 return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
1160 // X urem Y -> X and Y-1, where Y is a power of 2,
1161 if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/true)) {
1162 Constant *N1 = Constant::getAllOnesValue(I.getType());
1163 Value *Add = Builder->CreateAdd(Op1, N1);
1164 return BinaryOperator::CreateAnd(Op0, Add);
1167 // 1 urem X -> zext(X != 1)
1168 if (match(Op0, m_One())) {
1169 Value *Cmp = Builder->CreateICmpNE(Op1, Op0);
1170 Value *Ext = Builder->CreateZExt(Cmp, I.getType());
1171 return ReplaceInstUsesWith(I, Ext);
1177 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
1178 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1180 if (Value *V = SimplifySRemInst(Op0, Op1, TD))
1181 return ReplaceInstUsesWith(I, V);
1183 // Handle the integer rem common cases
1184 if (Instruction *Common = commonIRemTransforms(I))
1187 if (Value *RHSNeg = dyn_castNegVal(Op1))
1188 if (!isa<Constant>(RHSNeg) ||
1189 (isa<ConstantInt>(RHSNeg) &&
1190 cast<ConstantInt>(RHSNeg)->getValue().isStrictlyPositive())) {
1192 Worklist.AddValue(I.getOperand(1));
1193 I.setOperand(1, RHSNeg);
1197 // If the sign bits of both operands are zero (i.e. we can prove they are
1198 // unsigned inputs), turn this into a urem.
1199 if (I.getType()->isIntegerTy()) {
1200 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
1201 if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
1202 // X srem Y -> X urem Y, iff X and Y don't have sign bit set
1203 return BinaryOperator::CreateURem(Op0, Op1, I.getName());
1207 // If it's a constant vector, flip any negative values positive.
1208 if (isa<ConstantVector>(Op1) || isa<ConstantDataVector>(Op1)) {
1209 Constant *C = cast<Constant>(Op1);
1210 unsigned VWidth = C->getType()->getVectorNumElements();
1212 bool hasNegative = false;
1213 bool hasMissing = false;
1214 for (unsigned i = 0; i != VWidth; ++i) {
1215 Constant *Elt = C->getAggregateElement(i);
1221 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elt))
1222 if (RHS->isNegative())
1226 if (hasNegative && !hasMissing) {
1227 SmallVector<Constant *, 16> Elts(VWidth);
1228 for (unsigned i = 0; i != VWidth; ++i) {
1229 Elts[i] = C->getAggregateElement(i); // Handle undef, etc.
1230 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elts[i])) {
1231 if (RHS->isNegative())
1232 Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
1236 Constant *NewRHSV = ConstantVector::get(Elts);
1237 if (NewRHSV != C) { // Don't loop on -MININT
1238 Worklist.AddValue(I.getOperand(1));
1239 I.setOperand(1, NewRHSV);
1248 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
1249 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1251 if (Value *V = SimplifyFRemInst(Op0, Op1, TD))
1252 return ReplaceInstUsesWith(I, V);
1254 // Handle cases involving: rem X, (select Cond, Y, Z)
1255 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))