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/IR/PatternMatch.h"
20 using namespace PatternMatch;
22 #define DEBUG_TYPE "instcombine"
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,
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
33 if (!V->hasOneUse()) return nullptr;
35 bool MadeChange = false;
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);
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() && isKnownToBeAPowerOfTwo(I->getOperand(0), false,
50 0, IC.getAssumptionTracker(),
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)) {
60 if (I->getOpcode() == Instruction::LShr && !I->isExact()) {
65 if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
66 I->setHasNoUnsignedWrap();
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".
75 return MadeChange ? V : nullptr;
79 /// MultiplyOverflows - True if the multiply can not be expressed in an int
81 static bool MultiplyOverflows(const APInt &C1, const APInt &C2, APInt &Product,
85 Product = C1.smul_ov(C2, Overflow);
87 Product = C1.umul_ov(C2, Overflow);
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,
95 assert(C1.getBitWidth() == C2.getBitWidth() &&
96 "Inconsistent width of constants!");
98 APInt Remainder(C1.getBitWidth(), /*Val=*/0ULL, IsSigned);
100 APInt::sdivrem(C1, C2, Quotient, Remainder);
102 APInt::udivrem(C1, C2, Quotient, Remainder);
104 return Remainder.isMinValue();
107 /// \brief A helper routine of InstCombiner::visitMul().
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) {
114 SmallVector<Constant *, 4> Elts;
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())
120 Elts.push_back(ConstantInt::get(Elt->getType(), IVal->logBase2()));
123 return ConstantVector::get(Elts);
126 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
127 bool Changed = SimplifyAssociativeOrCommutative(I);
128 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
130 if (Value *V = SimplifyVectorOp(I))
131 return ReplaceInstUsesWith(I, V);
133 if (Value *V = SimplifyMulInst(Op0, Op1, DL, TLI, DT, AT))
134 return ReplaceInstUsesWith(I, V);
136 if (Value *V = SimplifyUsingDistributiveLaws(I))
137 return ReplaceInstUsesWith(I, V);
140 if (match(Op1, m_AllOnes())) {
141 BinaryOperator *BO = BinaryOperator::CreateNeg(Op0, I.getName());
142 if (I.hasNoSignedWrap())
143 BO->setHasNoSignedWrap();
147 // Also allow combining multiply instructions on vectors.
152 if (match(&I, m_Mul(m_Shl(m_Value(NewOp), m_Constant(C2)),
154 match(C1, m_APInt(IVal))) {
155 // ((X << C2)*C1) == (X * (C1 << C2))
156 Constant *Shl = ConstantExpr::getShl(C1, C2);
157 BinaryOperator *Mul = cast<BinaryOperator>(I.getOperand(0));
158 BinaryOperator *BO = BinaryOperator::CreateMul(NewOp, Shl);
159 if (I.hasNoUnsignedWrap() && Mul->hasNoUnsignedWrap())
160 BO->setHasNoUnsignedWrap();
161 if (I.hasNoSignedWrap() && Mul->hasNoSignedWrap() &&
162 Shl->isNotMinSignedValue())
163 BO->setHasNoSignedWrap();
167 if (match(&I, m_Mul(m_Value(NewOp), m_Constant(C1)))) {
168 Constant *NewCst = nullptr;
169 if (match(C1, m_APInt(IVal)) && IVal->isPowerOf2())
170 // Replace X*(2^C) with X << C, where C is either a scalar or a splat.
171 NewCst = ConstantInt::get(NewOp->getType(), IVal->logBase2());
172 else if (ConstantDataVector *CV = dyn_cast<ConstantDataVector>(C1))
173 // Replace X*(2^C) with X << C, where C is a vector of known
174 // constant powers of 2.
175 NewCst = getLogBase2Vector(CV);
178 BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
180 if (I.hasNoUnsignedWrap())
181 Shl->setHasNoUnsignedWrap();
182 if (I.hasNoSignedWrap() && NewCst->isNotMinSignedValue())
183 Shl->setHasNoSignedWrap();
190 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
191 // (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
192 // (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
193 // The "* (2**n)" thus becomes a potential shifting opportunity.
195 const APInt & Val = CI->getValue();
196 const APInt &PosVal = Val.abs();
197 if (Val.isNegative() && PosVal.isPowerOf2()) {
198 Value *X = nullptr, *Y = nullptr;
199 if (Op0->hasOneUse()) {
201 Value *Sub = nullptr;
202 if (match(Op0, m_Sub(m_Value(Y), m_Value(X))))
203 Sub = Builder->CreateSub(X, Y, "suba");
204 else if (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))
205 Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc");
208 BinaryOperator::CreateMul(Sub,
209 ConstantInt::get(Y->getType(), PosVal));
215 // Simplify mul instructions with a constant RHS.
216 if (isa<Constant>(Op1)) {
217 // Try to fold constant mul into select arguments.
218 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
219 if (Instruction *R = FoldOpIntoSelect(I, SI))
222 if (isa<PHINode>(Op0))
223 if (Instruction *NV = FoldOpIntoPhi(I))
226 // Canonicalize (X+C1)*CI -> X*CI+C1*CI.
230 if (match(Op0, m_OneUse(m_Add(m_Value(X), m_Constant(C1))))) {
231 Value *Mul = Builder->CreateMul(C1, Op1);
232 // Only go forward with the transform if C1*CI simplifies to a tidier
234 if (!match(Mul, m_Mul(m_Value(), m_Value())))
235 return BinaryOperator::CreateAdd(Builder->CreateMul(X, Op1), Mul);
240 if (Value *Op0v = dyn_castNegVal(Op0)) { // -X * -Y = X*Y
241 if (Value *Op1v = dyn_castNegVal(Op1)) {
242 BinaryOperator *BO = BinaryOperator::CreateMul(Op0v, Op1v);
243 if (I.hasNoSignedWrap() &&
244 match(Op0, m_NSWSub(m_Value(), m_Value())) &&
245 match(Op1, m_NSWSub(m_Value(), m_Value())))
246 BO->setHasNoSignedWrap();
251 // (X / Y) * Y = X - (X % Y)
252 // (X / Y) * -Y = (X % Y) - X
255 BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0);
257 (BO->getOpcode() != Instruction::UDiv &&
258 BO->getOpcode() != Instruction::SDiv)) {
260 BO = dyn_cast<BinaryOperator>(Op1);
262 Value *Neg = dyn_castNegVal(Op1C);
263 if (BO && BO->hasOneUse() &&
264 (BO->getOperand(1) == Op1C || BO->getOperand(1) == Neg) &&
265 (BO->getOpcode() == Instruction::UDiv ||
266 BO->getOpcode() == Instruction::SDiv)) {
267 Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
269 // If the division is exact, X % Y is zero, so we end up with X or -X.
270 if (PossiblyExactOperator *SDiv = dyn_cast<PossiblyExactOperator>(BO))
271 if (SDiv->isExact()) {
273 return ReplaceInstUsesWith(I, Op0BO);
274 return BinaryOperator::CreateNeg(Op0BO);
278 if (BO->getOpcode() == Instruction::UDiv)
279 Rem = Builder->CreateURem(Op0BO, Op1BO);
281 Rem = Builder->CreateSRem(Op0BO, Op1BO);
285 return BinaryOperator::CreateSub(Op0BO, Rem);
286 return BinaryOperator::CreateSub(Rem, Op0BO);
290 /// i1 mul -> i1 and.
291 if (I.getType()->getScalarType()->isIntegerTy(1))
292 return BinaryOperator::CreateAnd(Op0, Op1);
294 // X*(1 << Y) --> X << Y
295 // (1 << Y)*X --> X << Y
298 BinaryOperator *BO = nullptr;
300 if (match(Op0, m_Shl(m_One(), m_Value(Y)))) {
301 BO = BinaryOperator::CreateShl(Op1, Y);
302 ShlNSW = cast<BinaryOperator>(Op0)->hasNoSignedWrap();
304 if (match(Op1, m_Shl(m_One(), m_Value(Y)))) {
305 BO = BinaryOperator::CreateShl(Op0, Y);
306 ShlNSW = cast<BinaryOperator>(Op1)->hasNoSignedWrap();
309 if (I.hasNoUnsignedWrap())
310 BO->setHasNoUnsignedWrap();
311 if (I.hasNoSignedWrap() && ShlNSW)
312 BO->setHasNoSignedWrap();
317 // If one of the operands of the multiply is a cast from a boolean value, then
318 // we know the bool is either zero or one, so this is a 'masking' multiply.
319 // X * Y (where Y is 0 or 1) -> X & (0-Y)
320 if (!I.getType()->isVectorTy()) {
321 // -2 is "-1 << 1" so it is all bits set except the low one.
322 APInt Negative2(I.getType()->getPrimitiveSizeInBits(), (uint64_t)-2, true);
324 Value *BoolCast = nullptr, *OtherOp = nullptr;
325 if (MaskedValueIsZero(Op0, Negative2, 0, &I))
326 BoolCast = Op0, OtherOp = Op1;
327 else if (MaskedValueIsZero(Op1, Negative2, 0, &I))
328 BoolCast = Op1, OtherOp = Op0;
331 Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()),
333 return BinaryOperator::CreateAnd(V, OtherOp);
337 return Changed ? &I : nullptr;
340 /// Detect pattern log2(Y * 0.5) with corresponding fast math flags.
341 static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) {
342 if (!Op->hasOneUse())
345 IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op);
348 if (II->getIntrinsicID() != Intrinsic::log2 || !II->hasUnsafeAlgebra())
352 Value *OpLog2Of = II->getArgOperand(0);
353 if (!OpLog2Of->hasOneUse())
356 Instruction *I = dyn_cast<Instruction>(OpLog2Of);
359 if (I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra())
362 if (match(I->getOperand(0), m_SpecificFP(0.5)))
363 Y = I->getOperand(1);
364 else if (match(I->getOperand(1), m_SpecificFP(0.5)))
365 Y = I->getOperand(0);
368 static bool isFiniteNonZeroFp(Constant *C) {
369 if (C->getType()->isVectorTy()) {
370 for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E;
372 ConstantFP *CFP = dyn_cast<ConstantFP>(C->getAggregateElement(I));
373 if (!CFP || !CFP->getValueAPF().isFiniteNonZero())
379 return isa<ConstantFP>(C) &&
380 cast<ConstantFP>(C)->getValueAPF().isFiniteNonZero();
383 static bool isNormalFp(Constant *C) {
384 if (C->getType()->isVectorTy()) {
385 for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E;
387 ConstantFP *CFP = dyn_cast<ConstantFP>(C->getAggregateElement(I));
388 if (!CFP || !CFP->getValueAPF().isNormal())
394 return isa<ConstantFP>(C) && cast<ConstantFP>(C)->getValueAPF().isNormal();
397 /// Helper function of InstCombiner::visitFMul(BinaryOperator(). It returns
398 /// true iff the given value is FMul or FDiv with one and only one operand
399 /// being a normal constant (i.e. not Zero/NaN/Infinity).
400 static bool isFMulOrFDivWithConstant(Value *V) {
401 Instruction *I = dyn_cast<Instruction>(V);
402 if (!I || (I->getOpcode() != Instruction::FMul &&
403 I->getOpcode() != Instruction::FDiv))
406 Constant *C0 = dyn_cast<Constant>(I->getOperand(0));
407 Constant *C1 = dyn_cast<Constant>(I->getOperand(1));
412 return (C0 && isFiniteNonZeroFp(C0)) || (C1 && isFiniteNonZeroFp(C1));
415 /// foldFMulConst() is a helper routine of InstCombiner::visitFMul().
416 /// The input \p FMulOrDiv is a FMul/FDiv with one and only one operand
417 /// being a constant (i.e. isFMulOrFDivWithConstant(FMulOrDiv) == true).
418 /// This function is to simplify "FMulOrDiv * C" and returns the
419 /// resulting expression. Note that this function could return NULL in
420 /// case the constants cannot be folded into a normal floating-point.
422 Value *InstCombiner::foldFMulConst(Instruction *FMulOrDiv, Constant *C,
423 Instruction *InsertBefore) {
424 assert(isFMulOrFDivWithConstant(FMulOrDiv) && "V is invalid");
426 Value *Opnd0 = FMulOrDiv->getOperand(0);
427 Value *Opnd1 = FMulOrDiv->getOperand(1);
429 Constant *C0 = dyn_cast<Constant>(Opnd0);
430 Constant *C1 = dyn_cast<Constant>(Opnd1);
432 BinaryOperator *R = nullptr;
434 // (X * C0) * C => X * (C0*C)
435 if (FMulOrDiv->getOpcode() == Instruction::FMul) {
436 Constant *F = ConstantExpr::getFMul(C1 ? C1 : C0, C);
438 R = BinaryOperator::CreateFMul(C1 ? Opnd0 : Opnd1, F);
441 // (C0 / X) * C => (C0 * C) / X
442 if (FMulOrDiv->hasOneUse()) {
443 // It would otherwise introduce another div.
444 Constant *F = ConstantExpr::getFMul(C0, C);
446 R = BinaryOperator::CreateFDiv(F, Opnd1);
449 // (X / C1) * C => X * (C/C1) if C/C1 is not a denormal
450 Constant *F = ConstantExpr::getFDiv(C, C1);
452 R = BinaryOperator::CreateFMul(Opnd0, F);
454 // (X / C1) * C => X / (C1/C)
455 Constant *F = ConstantExpr::getFDiv(C1, C);
457 R = BinaryOperator::CreateFDiv(Opnd0, F);
463 R->setHasUnsafeAlgebra(true);
464 InsertNewInstWith(R, *InsertBefore);
470 Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
471 bool Changed = SimplifyAssociativeOrCommutative(I);
472 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
474 if (Value *V = SimplifyVectorOp(I))
475 return ReplaceInstUsesWith(I, V);
477 if (isa<Constant>(Op0))
480 if (Value *V = SimplifyFMulInst(Op0, Op1, I.getFastMathFlags(), DL, TLI,
482 return ReplaceInstUsesWith(I, V);
484 bool AllowReassociate = I.hasUnsafeAlgebra();
486 // Simplify mul instructions with a constant RHS.
487 if (isa<Constant>(Op1)) {
488 // Try to fold constant mul into select arguments.
489 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
490 if (Instruction *R = FoldOpIntoSelect(I, SI))
493 if (isa<PHINode>(Op0))
494 if (Instruction *NV = FoldOpIntoPhi(I))
497 // (fmul X, -1.0) --> (fsub -0.0, X)
498 if (match(Op1, m_SpecificFP(-1.0))) {
499 Constant *NegZero = ConstantFP::getNegativeZero(Op1->getType());
500 Instruction *RI = BinaryOperator::CreateFSub(NegZero, Op0);
501 RI->copyFastMathFlags(&I);
505 Constant *C = cast<Constant>(Op1);
506 if (AllowReassociate && isFiniteNonZeroFp(C)) {
507 // Let MDC denote an expression in one of these forms:
508 // X * C, C/X, X/C, where C is a constant.
510 // Try to simplify "MDC * Constant"
511 if (isFMulOrFDivWithConstant(Op0))
512 if (Value *V = foldFMulConst(cast<Instruction>(Op0), C, &I))
513 return ReplaceInstUsesWith(I, V);
515 // (MDC +/- C1) * C => (MDC * C) +/- (C1 * C)
516 Instruction *FAddSub = dyn_cast<Instruction>(Op0);
518 (FAddSub->getOpcode() == Instruction::FAdd ||
519 FAddSub->getOpcode() == Instruction::FSub)) {
520 Value *Opnd0 = FAddSub->getOperand(0);
521 Value *Opnd1 = FAddSub->getOperand(1);
522 Constant *C0 = dyn_cast<Constant>(Opnd0);
523 Constant *C1 = dyn_cast<Constant>(Opnd1);
527 std::swap(Opnd0, Opnd1);
531 if (C1 && isFiniteNonZeroFp(C1) && isFMulOrFDivWithConstant(Opnd0)) {
532 Value *M1 = ConstantExpr::getFMul(C1, C);
533 Value *M0 = isNormalFp(cast<Constant>(M1)) ?
534 foldFMulConst(cast<Instruction>(Opnd0), C, &I) :
537 if (Swap && FAddSub->getOpcode() == Instruction::FSub)
540 Instruction *RI = (FAddSub->getOpcode() == Instruction::FAdd)
541 ? BinaryOperator::CreateFAdd(M0, M1)
542 : BinaryOperator::CreateFSub(M0, M1);
543 RI->copyFastMathFlags(&I);
551 // sqrt(X) * sqrt(X) -> X
552 if (AllowReassociate && (Op0 == Op1))
553 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0))
554 if (II->getIntrinsicID() == Intrinsic::sqrt)
555 return ReplaceInstUsesWith(I, II->getOperand(0));
557 // Under unsafe algebra do:
558 // X * log2(0.5*Y) = X*log2(Y) - X
559 if (AllowReassociate) {
560 Value *OpX = nullptr;
561 Value *OpY = nullptr;
563 detectLog2OfHalf(Op0, OpY, Log2);
567 detectLog2OfHalf(Op1, OpY, Log2);
572 // if pattern detected emit alternate sequence
574 BuilderTy::FastMathFlagGuard Guard(*Builder);
575 Builder->SetFastMathFlags(Log2->getFastMathFlags());
576 Log2->setArgOperand(0, OpY);
577 Value *FMulVal = Builder->CreateFMul(OpX, Log2);
578 Value *FSub = Builder->CreateFSub(FMulVal, OpX);
580 return ReplaceInstUsesWith(I, FSub);
584 // Handle symmetric situation in a 2-iteration loop
587 for (int i = 0; i < 2; i++) {
588 bool IgnoreZeroSign = I.hasNoSignedZeros();
589 if (BinaryOperator::isFNeg(Opnd0, IgnoreZeroSign)) {
590 BuilderTy::FastMathFlagGuard Guard(*Builder);
591 Builder->SetFastMathFlags(I.getFastMathFlags());
593 Value *N0 = dyn_castFNegVal(Opnd0, IgnoreZeroSign);
594 Value *N1 = dyn_castFNegVal(Opnd1, IgnoreZeroSign);
598 Value *FMul = Builder->CreateFMul(N0, N1);
600 return ReplaceInstUsesWith(I, FMul);
603 if (Opnd0->hasOneUse()) {
604 // -X * Y => -(X*Y) (Promote negation as high as possible)
605 Value *T = Builder->CreateFMul(N0, Opnd1);
606 Value *Neg = Builder->CreateFNeg(T);
608 return ReplaceInstUsesWith(I, Neg);
612 // (X*Y) * X => (X*X) * Y where Y != X
613 // The purpose is two-fold:
614 // 1) to form a power expression (of X).
615 // 2) potentially shorten the critical path: After transformation, the
616 // latency of the instruction Y is amortized by the expression of X*X,
617 // and therefore Y is in a "less critical" position compared to what it
618 // was before the transformation.
620 if (AllowReassociate) {
621 Value *Opnd0_0, *Opnd0_1;
622 if (Opnd0->hasOneUse() &&
623 match(Opnd0, m_FMul(m_Value(Opnd0_0), m_Value(Opnd0_1)))) {
625 if (Opnd0_0 == Opnd1 && Opnd0_1 != Opnd1)
627 else if (Opnd0_1 == Opnd1 && Opnd0_0 != Opnd1)
631 BuilderTy::FastMathFlagGuard Guard(*Builder);
632 Builder->SetFastMathFlags(I.getFastMathFlags());
633 Value *T = Builder->CreateFMul(Opnd1, Opnd1);
635 Value *R = Builder->CreateFMul(T, Y);
637 return ReplaceInstUsesWith(I, R);
642 if (!isa<Constant>(Op1))
643 std::swap(Opnd0, Opnd1);
648 return Changed ? &I : nullptr;
651 /// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
653 bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
654 SelectInst *SI = cast<SelectInst>(I.getOperand(1));
656 // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
657 int NonNullOperand = -1;
658 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
659 if (ST->isNullValue())
661 // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
662 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
663 if (ST->isNullValue())
666 if (NonNullOperand == -1)
669 Value *SelectCond = SI->getOperand(0);
671 // Change the div/rem to use 'Y' instead of the select.
672 I.setOperand(1, SI->getOperand(NonNullOperand));
674 // Okay, we know we replace the operand of the div/rem with 'Y' with no
675 // problem. However, the select, or the condition of the select may have
676 // multiple uses. Based on our knowledge that the operand must be non-zero,
677 // propagate the known value for the select into other uses of it, and
678 // propagate a known value of the condition into its other users.
680 // If the select and condition only have a single use, don't bother with this,
682 if (SI->use_empty() && SelectCond->hasOneUse())
685 // Scan the current block backward, looking for other uses of SI.
686 BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
688 while (BBI != BBFront) {
690 // If we found a call to a function, we can't assume it will return, so
691 // information from below it cannot be propagated above it.
692 if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
695 // Replace uses of the select or its condition with the known values.
696 for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
699 *I = SI->getOperand(NonNullOperand);
701 } else if (*I == SelectCond) {
702 *I = Builder->getInt1(NonNullOperand == 1);
707 // If we past the instruction, quit looking for it.
710 if (&*BBI == SelectCond)
711 SelectCond = nullptr;
713 // If we ran out of things to eliminate, break out of the loop.
714 if (!SelectCond && !SI)
722 /// This function implements the transforms common to both integer division
723 /// instructions (udiv and sdiv). It is called by the visitors to those integer
724 /// division instructions.
725 /// @brief Common integer divide transforms
726 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
727 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
729 // The RHS is known non-zero.
730 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, &I)) {
735 // Handle cases involving: [su]div X, (select Cond, Y, Z)
736 // This does not apply for fdiv.
737 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
740 if (Instruction *LHS = dyn_cast<Instruction>(Op0)) {
742 if (match(Op1, m_APInt(C2))) {
745 bool IsSigned = I.getOpcode() == Instruction::SDiv;
747 // (X / C1) / C2 -> X / (C1*C2)
748 if ((IsSigned && match(LHS, m_SDiv(m_Value(X), m_APInt(C1)))) ||
749 (!IsSigned && match(LHS, m_UDiv(m_Value(X), m_APInt(C1))))) {
750 APInt Product(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
751 if (!MultiplyOverflows(*C1, *C2, Product, IsSigned))
752 return BinaryOperator::Create(I.getOpcode(), X,
753 ConstantInt::get(I.getType(), Product));
756 if ((IsSigned && match(LHS, m_NSWMul(m_Value(X), m_APInt(C1)))) ||
757 (!IsSigned && match(LHS, m_NUWMul(m_Value(X), m_APInt(C1))))) {
758 APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
760 // (X * C1) / C2 -> X / (C2 / C1) if C2 is a multiple of C1.
761 if (IsMultiple(*C2, *C1, Quotient, IsSigned)) {
762 BinaryOperator *BO = BinaryOperator::Create(
763 I.getOpcode(), X, ConstantInt::get(X->getType(), Quotient));
764 BO->setIsExact(I.isExact());
768 // (X * C1) / C2 -> X * (C1 / C2) if C1 is a multiple of C2.
769 if (IsMultiple(*C1, *C2, Quotient, IsSigned)) {
770 BinaryOperator *BO = BinaryOperator::Create(
771 Instruction::Mul, X, ConstantInt::get(X->getType(), Quotient));
772 BO->setHasNoUnsignedWrap(
774 cast<OverflowingBinaryOperator>(LHS)->hasNoUnsignedWrap());
775 BO->setHasNoSignedWrap(
776 cast<OverflowingBinaryOperator>(LHS)->hasNoSignedWrap());
781 if ((IsSigned && match(LHS, m_NSWShl(m_Value(X), m_APInt(C1))) &&
782 *C1 != C1->getBitWidth() - 1) ||
783 (!IsSigned && match(LHS, m_NUWShl(m_Value(X), m_APInt(C1))))) {
784 APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
785 APInt C1Shifted = APInt::getOneBitSet(
786 C1->getBitWidth(), static_cast<unsigned>(C1->getLimitedValue()));
788 // (X << C1) / C2 -> X / (C2 >> C1) if C2 is a multiple of C1.
789 if (IsMultiple(*C2, C1Shifted, Quotient, IsSigned)) {
790 BinaryOperator *BO = BinaryOperator::Create(
791 I.getOpcode(), X, ConstantInt::get(X->getType(), Quotient));
792 BO->setIsExact(I.isExact());
796 // (X << C1) / C2 -> X * (C2 >> C1) if C1 is a multiple of C2.
797 if (IsMultiple(C1Shifted, *C2, Quotient, IsSigned)) {
798 BinaryOperator *BO = BinaryOperator::Create(
799 Instruction::Mul, X, ConstantInt::get(X->getType(), Quotient));
800 BO->setHasNoUnsignedWrap(
802 cast<OverflowingBinaryOperator>(LHS)->hasNoUnsignedWrap());
803 BO->setHasNoSignedWrap(
804 cast<OverflowingBinaryOperator>(LHS)->hasNoSignedWrap());
809 if (*C2 != 0) { // avoid X udiv 0
810 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
811 if (Instruction *R = FoldOpIntoSelect(I, SI))
813 if (isa<PHINode>(Op0))
814 if (Instruction *NV = FoldOpIntoPhi(I))
820 if (ConstantInt *One = dyn_cast<ConstantInt>(Op0)) {
821 if (One->isOne() && !I.getType()->isIntegerTy(1)) {
822 bool isSigned = I.getOpcode() == Instruction::SDiv;
824 // If Op1 is 0 then it's undefined behaviour, if Op1 is 1 then the
825 // result is one, if Op1 is -1 then the result is minus one, otherwise
827 Value *Inc = Builder->CreateAdd(Op1, One);
828 Value *Cmp = Builder->CreateICmpULT(
829 Inc, ConstantInt::get(I.getType(), 3));
830 return SelectInst::Create(Cmp, Op1, ConstantInt::get(I.getType(), 0));
832 // If Op1 is 0 then it's undefined behaviour. If Op1 is 1 then the
833 // result is one, otherwise it's zero.
834 return new ZExtInst(Builder->CreateICmpEQ(Op1, One), I.getType());
839 // See if we can fold away this div instruction.
840 if (SimplifyDemandedInstructionBits(I))
843 // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
844 Value *X = nullptr, *Z = nullptr;
845 if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
846 bool isSigned = I.getOpcode() == Instruction::SDiv;
847 if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
848 (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
849 return BinaryOperator::Create(I.getOpcode(), X, Op1);
855 /// dyn_castZExtVal - Checks if V is a zext or constant that can
856 /// be truncated to Ty without losing bits.
857 static Value *dyn_castZExtVal(Value *V, Type *Ty) {
858 if (ZExtInst *Z = dyn_cast<ZExtInst>(V)) {
859 if (Z->getSrcTy() == Ty)
860 return Z->getOperand(0);
861 } else if (ConstantInt *C = dyn_cast<ConstantInt>(V)) {
862 if (C->getValue().getActiveBits() <= cast<IntegerType>(Ty)->getBitWidth())
863 return ConstantExpr::getTrunc(C, Ty);
869 const unsigned MaxDepth = 6;
870 typedef Instruction *(*FoldUDivOperandCb)(Value *Op0, Value *Op1,
871 const BinaryOperator &I,
874 /// \brief Used to maintain state for visitUDivOperand().
875 struct UDivFoldAction {
876 FoldUDivOperandCb FoldAction; ///< Informs visitUDiv() how to fold this
877 ///< operand. This can be zero if this action
878 ///< joins two actions together.
880 Value *OperandToFold; ///< Which operand to fold.
882 Instruction *FoldResult; ///< The instruction returned when FoldAction is
885 size_t SelectLHSIdx; ///< Stores the LHS action index if this action
886 ///< joins two actions together.
889 UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand)
890 : FoldAction(FA), OperandToFold(InputOperand), FoldResult(nullptr) {}
891 UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand, size_t SLHS)
892 : FoldAction(FA), OperandToFold(InputOperand), SelectLHSIdx(SLHS) {}
896 // X udiv 2^C -> X >> C
897 static Instruction *foldUDivPow2Cst(Value *Op0, Value *Op1,
898 const BinaryOperator &I, InstCombiner &IC) {
899 const APInt &C = cast<Constant>(Op1)->getUniqueInteger();
900 BinaryOperator *LShr = BinaryOperator::CreateLShr(
901 Op0, ConstantInt::get(Op0->getType(), C.logBase2()));
907 // X udiv C, where C >= signbit
908 static Instruction *foldUDivNegCst(Value *Op0, Value *Op1,
909 const BinaryOperator &I, InstCombiner &IC) {
910 Value *ICI = IC.Builder->CreateICmpULT(Op0, cast<ConstantInt>(Op1));
912 return SelectInst::Create(ICI, Constant::getNullValue(I.getType()),
913 ConstantInt::get(I.getType(), 1));
916 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
917 static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
919 Instruction *ShiftLeft = cast<Instruction>(Op1);
920 if (isa<ZExtInst>(ShiftLeft))
921 ShiftLeft = cast<Instruction>(ShiftLeft->getOperand(0));
924 cast<Constant>(ShiftLeft->getOperand(0))->getUniqueInteger();
925 Value *N = ShiftLeft->getOperand(1);
927 N = IC.Builder->CreateAdd(N, ConstantInt::get(N->getType(), CI.logBase2()));
928 if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
929 N = IC.Builder->CreateZExt(N, Z->getDestTy());
930 BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N);
936 // \brief Recursively visits the possible right hand operands of a udiv
937 // instruction, seeing through select instructions, to determine if we can
938 // replace the udiv with something simpler. If we find that an operand is not
939 // able to simplify the udiv, we abort the entire transformation.
940 static size_t visitUDivOperand(Value *Op0, Value *Op1, const BinaryOperator &I,
941 SmallVectorImpl<UDivFoldAction> &Actions,
942 unsigned Depth = 0) {
943 // Check to see if this is an unsigned division with an exact power of 2,
944 // if so, convert to a right shift.
945 if (match(Op1, m_Power2())) {
946 Actions.push_back(UDivFoldAction(foldUDivPow2Cst, Op1));
947 return Actions.size();
950 if (ConstantInt *C = dyn_cast<ConstantInt>(Op1))
951 // X udiv C, where C >= signbit
952 if (C->getValue().isNegative()) {
953 Actions.push_back(UDivFoldAction(foldUDivNegCst, C));
954 return Actions.size();
957 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
958 if (match(Op1, m_Shl(m_Power2(), m_Value())) ||
959 match(Op1, m_ZExt(m_Shl(m_Power2(), m_Value())))) {
960 Actions.push_back(UDivFoldAction(foldUDivShl, Op1));
961 return Actions.size();
964 // The remaining tests are all recursive, so bail out if we hit the limit.
965 if (Depth++ == MaxDepth)
968 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
970 visitUDivOperand(Op0, SI->getOperand(1), I, Actions, Depth))
971 if (visitUDivOperand(Op0, SI->getOperand(2), I, Actions, Depth)) {
972 Actions.push_back(UDivFoldAction(nullptr, Op1, LHSIdx - 1));
973 return Actions.size();
979 Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
980 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
982 if (Value *V = SimplifyVectorOp(I))
983 return ReplaceInstUsesWith(I, V);
985 if (Value *V = SimplifyUDivInst(Op0, Op1, DL, TLI, DT, AT))
986 return ReplaceInstUsesWith(I, V);
988 // Handle the integer div common cases
989 if (Instruction *Common = commonIDivTransforms(I))
992 // (x lshr C1) udiv C2 --> x udiv (C2 << C1)
995 const APInt *C1, *C2;
996 if (match(Op0, m_LShr(m_Value(X), m_APInt(C1))) &&
997 match(Op1, m_APInt(C2))) {
999 APInt C2ShlC1 = C2->ushl_ov(*C1, Overflow);
1001 bool IsExact = I.isExact() && match(Op0, m_Exact(m_Value()));
1002 BinaryOperator *BO = BinaryOperator::CreateUDiv(
1003 X, ConstantInt::get(X->getType(), C2ShlC1));
1011 // (zext A) udiv (zext B) --> zext (A udiv B)
1012 if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
1013 if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
1014 return new ZExtInst(
1015 Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div", I.isExact()),
1018 // (LHS udiv (select (select (...)))) -> (LHS >> (select (select (...))))
1019 SmallVector<UDivFoldAction, 6> UDivActions;
1020 if (visitUDivOperand(Op0, Op1, I, UDivActions))
1021 for (unsigned i = 0, e = UDivActions.size(); i != e; ++i) {
1022 FoldUDivOperandCb Action = UDivActions[i].FoldAction;
1023 Value *ActionOp1 = UDivActions[i].OperandToFold;
1026 Inst = Action(Op0, ActionOp1, I, *this);
1028 // This action joins two actions together. The RHS of this action is
1029 // simply the last action we processed, we saved the LHS action index in
1030 // the joining action.
1031 size_t SelectRHSIdx = i - 1;
1032 Value *SelectRHS = UDivActions[SelectRHSIdx].FoldResult;
1033 size_t SelectLHSIdx = UDivActions[i].SelectLHSIdx;
1034 Value *SelectLHS = UDivActions[SelectLHSIdx].FoldResult;
1035 Inst = SelectInst::Create(cast<SelectInst>(ActionOp1)->getCondition(),
1036 SelectLHS, SelectRHS);
1039 // If this is the last action to process, return it to the InstCombiner.
1040 // Otherwise, we insert it before the UDiv and record it so that we may
1041 // use it as part of a joining action (i.e., a SelectInst).
1043 Inst->insertBefore(&I);
1044 UDivActions[i].FoldResult = Inst;
1052 Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
1053 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1055 if (Value *V = SimplifyVectorOp(I))
1056 return ReplaceInstUsesWith(I, V);
1058 if (Value *V = SimplifySDivInst(Op0, Op1, DL, TLI, DT, AT))
1059 return ReplaceInstUsesWith(I, V);
1061 // Handle the integer div common cases
1062 if (Instruction *Common = commonIDivTransforms(I))
1066 if (match(Op1, m_AllOnes()))
1067 return BinaryOperator::CreateNeg(Op0);
1069 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
1070 // sdiv X, C --> ashr exact X, log2(C)
1071 if (I.isExact() && RHS->getValue().isNonNegative() &&
1072 RHS->getValue().isPowerOf2()) {
1073 Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
1074 RHS->getValue().exactLogBase2());
1075 return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName());
1079 if (Constant *RHS = dyn_cast<Constant>(Op1)) {
1080 // X/INT_MIN -> X == INT_MIN
1081 if (RHS->isMinSignedValue())
1082 return new ZExtInst(Builder->CreateICmpEQ(Op0, Op1), I.getType());
1084 // -X/C --> X/-C provided the negation doesn't overflow.
1085 if (SubOperator *Sub = dyn_cast<SubOperator>(Op0))
1086 if (match(Sub->getOperand(0), m_Zero()) && Sub->hasNoSignedWrap())
1087 return BinaryOperator::CreateSDiv(Sub->getOperand(1),
1088 ConstantExpr::getNeg(RHS));
1091 // If the sign bits of both operands are zero (i.e. we can prove they are
1092 // unsigned inputs), turn this into a udiv.
1093 if (I.getType()->isIntegerTy()) {
1094 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
1095 if (MaskedValueIsZero(Op0, Mask, 0, &I)) {
1096 if (MaskedValueIsZero(Op1, Mask, 0, &I)) {
1097 // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
1098 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
1101 if (match(Op1, m_Shl(m_Power2(), m_Value()))) {
1102 // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
1103 // Safe because the only negative value (1 << Y) can take on is
1104 // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
1105 // the sign bit set.
1106 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
1114 /// CvtFDivConstToReciprocal tries to convert X/C into X*1/C if C not a special
1116 /// 1) 1/C is exact, or
1117 /// 2) reciprocal is allowed.
1118 /// If the conversion was successful, the simplified expression "X * 1/C" is
1119 /// returned; otherwise, NULL is returned.
1121 static Instruction *CvtFDivConstToReciprocal(Value *Dividend, Constant *Divisor,
1122 bool AllowReciprocal) {
1123 if (!isa<ConstantFP>(Divisor)) // TODO: handle vectors.
1126 const APFloat &FpVal = cast<ConstantFP>(Divisor)->getValueAPF();
1127 APFloat Reciprocal(FpVal.getSemantics());
1128 bool Cvt = FpVal.getExactInverse(&Reciprocal);
1130 if (!Cvt && AllowReciprocal && FpVal.isFiniteNonZero()) {
1131 Reciprocal = APFloat(FpVal.getSemantics(), 1.0f);
1132 (void)Reciprocal.divide(FpVal, APFloat::rmNearestTiesToEven);
1133 Cvt = !Reciprocal.isDenormal();
1140 R = ConstantFP::get(Dividend->getType()->getContext(), Reciprocal);
1141 return BinaryOperator::CreateFMul(Dividend, R);
1144 Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
1145 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1147 if (Value *V = SimplifyVectorOp(I))
1148 return ReplaceInstUsesWith(I, V);
1150 if (Value *V = SimplifyFDivInst(Op0, Op1, DL, TLI, DT, AT))
1151 return ReplaceInstUsesWith(I, V);
1153 if (isa<Constant>(Op0))
1154 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1155 if (Instruction *R = FoldOpIntoSelect(I, SI))
1158 bool AllowReassociate = I.hasUnsafeAlgebra();
1159 bool AllowReciprocal = I.hasAllowReciprocal();
1161 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1162 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1163 if (Instruction *R = FoldOpIntoSelect(I, SI))
1166 if (AllowReassociate) {
1167 Constant *C1 = nullptr;
1168 Constant *C2 = Op1C;
1170 Instruction *Res = nullptr;
1172 if (match(Op0, m_FMul(m_Value(X), m_Constant(C1)))) {
1173 // (X*C1)/C2 => X * (C1/C2)
1175 Constant *C = ConstantExpr::getFDiv(C1, C2);
1177 Res = BinaryOperator::CreateFMul(X, C);
1178 } else if (match(Op0, m_FDiv(m_Value(X), m_Constant(C1)))) {
1179 // (X/C1)/C2 => X /(C2*C1) [=> X * 1/(C2*C1) if reciprocal is allowed]
1181 Constant *C = ConstantExpr::getFMul(C1, C2);
1182 if (isNormalFp(C)) {
1183 Res = CvtFDivConstToReciprocal(X, C, AllowReciprocal);
1185 Res = BinaryOperator::CreateFDiv(X, C);
1190 Res->setFastMathFlags(I.getFastMathFlags());
1196 if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal)) {
1197 T->copyFastMathFlags(&I);
1204 if (AllowReassociate && isa<Constant>(Op0)) {
1205 Constant *C1 = cast<Constant>(Op0), *C2;
1206 Constant *Fold = nullptr;
1208 bool CreateDiv = true;
1210 // C1 / (X*C2) => (C1/C2) / X
1211 if (match(Op1, m_FMul(m_Value(X), m_Constant(C2))))
1212 Fold = ConstantExpr::getFDiv(C1, C2);
1213 else if (match(Op1, m_FDiv(m_Value(X), m_Constant(C2)))) {
1214 // C1 / (X/C2) => (C1*C2) / X
1215 Fold = ConstantExpr::getFMul(C1, C2);
1216 } else if (match(Op1, m_FDiv(m_Constant(C2), m_Value(X)))) {
1217 // C1 / (C2/X) => (C1/C2) * X
1218 Fold = ConstantExpr::getFDiv(C1, C2);
1222 if (Fold && isNormalFp(Fold)) {
1223 Instruction *R = CreateDiv ? BinaryOperator::CreateFDiv(Fold, X)
1224 : BinaryOperator::CreateFMul(X, Fold);
1225 R->setFastMathFlags(I.getFastMathFlags());
1231 if (AllowReassociate) {
1233 Value *NewInst = nullptr;
1234 Instruction *SimpR = nullptr;
1236 if (Op0->hasOneUse() && match(Op0, m_FDiv(m_Value(X), m_Value(Y)))) {
1237 // (X/Y) / Z => X / (Y*Z)
1239 if (!isa<Constant>(Y) || !isa<Constant>(Op1)) {
1240 NewInst = Builder->CreateFMul(Y, Op1);
1241 if (Instruction *RI = dyn_cast<Instruction>(NewInst)) {
1242 FastMathFlags Flags = I.getFastMathFlags();
1243 Flags &= cast<Instruction>(Op0)->getFastMathFlags();
1244 RI->setFastMathFlags(Flags);
1246 SimpR = BinaryOperator::CreateFDiv(X, NewInst);
1248 } else if (Op1->hasOneUse() && match(Op1, m_FDiv(m_Value(X), m_Value(Y)))) {
1249 // Z / (X/Y) => Z*Y / X
1251 if (!isa<Constant>(Y) || !isa<Constant>(Op0)) {
1252 NewInst = Builder->CreateFMul(Op0, Y);
1253 if (Instruction *RI = dyn_cast<Instruction>(NewInst)) {
1254 FastMathFlags Flags = I.getFastMathFlags();
1255 Flags &= cast<Instruction>(Op1)->getFastMathFlags();
1256 RI->setFastMathFlags(Flags);
1258 SimpR = BinaryOperator::CreateFDiv(NewInst, X);
1263 if (Instruction *T = dyn_cast<Instruction>(NewInst))
1264 T->setDebugLoc(I.getDebugLoc());
1265 SimpR->setFastMathFlags(I.getFastMathFlags());
1273 /// This function implements the transforms common to both integer remainder
1274 /// instructions (urem and srem). It is called by the visitors to those integer
1275 /// remainder instructions.
1276 /// @brief Common integer remainder transforms
1277 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
1278 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1280 // The RHS is known non-zero.
1281 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, &I)) {
1286 // Handle cases involving: rem X, (select Cond, Y, Z)
1287 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
1290 if (isa<Constant>(Op1)) {
1291 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1292 if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
1293 if (Instruction *R = FoldOpIntoSelect(I, SI))
1295 } else if (isa<PHINode>(Op0I)) {
1296 if (Instruction *NV = FoldOpIntoPhi(I))
1300 // See if we can fold away this rem instruction.
1301 if (SimplifyDemandedInstructionBits(I))
1309 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
1310 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1312 if (Value *V = SimplifyVectorOp(I))
1313 return ReplaceInstUsesWith(I, V);
1315 if (Value *V = SimplifyURemInst(Op0, Op1, DL, TLI, DT, AT))
1316 return ReplaceInstUsesWith(I, V);
1318 if (Instruction *common = commonIRemTransforms(I))
1321 // (zext A) urem (zext B) --> zext (A urem B)
1322 if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
1323 if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
1324 return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
1327 // X urem Y -> X and Y-1, where Y is a power of 2,
1328 if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/true, 0, AT, &I, DT)) {
1329 Constant *N1 = Constant::getAllOnesValue(I.getType());
1330 Value *Add = Builder->CreateAdd(Op1, N1);
1331 return BinaryOperator::CreateAnd(Op0, Add);
1334 // 1 urem X -> zext(X != 1)
1335 if (match(Op0, m_One())) {
1336 Value *Cmp = Builder->CreateICmpNE(Op1, Op0);
1337 Value *Ext = Builder->CreateZExt(Cmp, I.getType());
1338 return ReplaceInstUsesWith(I, Ext);
1344 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
1345 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1347 if (Value *V = SimplifyVectorOp(I))
1348 return ReplaceInstUsesWith(I, V);
1350 if (Value *V = SimplifySRemInst(Op0, Op1, DL, TLI, DT, AT))
1351 return ReplaceInstUsesWith(I, V);
1353 // Handle the integer rem common cases
1354 if (Instruction *Common = commonIRemTransforms(I))
1360 if (match(Op1, m_APInt(Y)) && Y->isNegative() && !Y->isMinSignedValue()) {
1361 Worklist.AddValue(I.getOperand(1));
1362 I.setOperand(1, ConstantInt::get(I.getType(), -*Y));
1367 // If the sign bits of both operands are zero (i.e. we can prove they are
1368 // unsigned inputs), turn this into a urem.
1369 if (I.getType()->isIntegerTy()) {
1370 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
1371 if (MaskedValueIsZero(Op1, Mask, 0, &I) &&
1372 MaskedValueIsZero(Op0, Mask, 0, &I)) {
1373 // X srem Y -> X urem Y, iff X and Y don't have sign bit set
1374 return BinaryOperator::CreateURem(Op0, Op1, I.getName());
1378 // If it's a constant vector, flip any negative values positive.
1379 if (isa<ConstantVector>(Op1) || isa<ConstantDataVector>(Op1)) {
1380 Constant *C = cast<Constant>(Op1);
1381 unsigned VWidth = C->getType()->getVectorNumElements();
1383 bool hasNegative = false;
1384 bool hasMissing = false;
1385 for (unsigned i = 0; i != VWidth; ++i) {
1386 Constant *Elt = C->getAggregateElement(i);
1392 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elt))
1393 if (RHS->isNegative())
1397 if (hasNegative && !hasMissing) {
1398 SmallVector<Constant *, 16> Elts(VWidth);
1399 for (unsigned i = 0; i != VWidth; ++i) {
1400 Elts[i] = C->getAggregateElement(i); // Handle undef, etc.
1401 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elts[i])) {
1402 if (RHS->isNegative())
1403 Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
1407 Constant *NewRHSV = ConstantVector::get(Elts);
1408 if (NewRHSV != C) { // Don't loop on -MININT
1409 Worklist.AddValue(I.getOperand(1));
1410 I.setOperand(1, NewRHSV);
1419 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
1420 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1422 if (Value *V = SimplifyVectorOp(I))
1423 return ReplaceInstUsesWith(I, V);
1425 if (Value *V = SimplifyFRemInst(Op0, Op1, DL, TLI, DT, AT))
1426 return ReplaceInstUsesWith(I, V);
1428 // Handle cases involving: rem X, (select Cond, Y, Z)
1429 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))