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 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
99 bool Changed = SimplifyAssociativeOrCommutative(I);
100 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
102 if (Value *V = SimplifyMulInst(Op0, Op1, TD))
103 return ReplaceInstUsesWith(I, V);
105 if (Value *V = SimplifyUsingDistributiveLaws(I))
106 return ReplaceInstUsesWith(I, V);
108 if (match(Op1, m_AllOnes())) // X * -1 == 0 - X
109 return BinaryOperator::CreateNeg(Op0, I.getName());
111 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
113 // ((X << C1)*C2) == (X * (C2 << C1))
114 if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op0))
115 if (SI->getOpcode() == Instruction::Shl)
116 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
117 return BinaryOperator::CreateMul(SI->getOperand(0),
118 ConstantExpr::getShl(CI, ShOp));
120 const APInt &Val = CI->getValue();
121 if (Val.isPowerOf2()) { // Replace X*(2^C) with X << C
122 Constant *NewCst = ConstantInt::get(Op0->getType(), Val.logBase2());
123 BinaryOperator *Shl = BinaryOperator::CreateShl(Op0, NewCst);
124 if (I.hasNoSignedWrap()) Shl->setHasNoSignedWrap();
125 if (I.hasNoUnsignedWrap()) Shl->setHasNoUnsignedWrap();
129 // Canonicalize (X+C1)*CI -> X*CI+C1*CI.
130 { Value *X; ConstantInt *C1;
131 if (Op0->hasOneUse() &&
132 match(Op0, m_Add(m_Value(X), m_ConstantInt(C1)))) {
133 Value *Add = Builder->CreateMul(X, CI);
134 return BinaryOperator::CreateAdd(Add, Builder->CreateMul(C1, CI));
138 // (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
139 // (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
140 // The "* (2**n)" thus becomes a potential shifting opportunity.
142 const APInt & Val = CI->getValue();
143 const APInt &PosVal = Val.abs();
144 if (Val.isNegative() && PosVal.isPowerOf2()) {
145 Value *X = 0, *Y = 0;
146 if (Op0->hasOneUse()) {
149 if (match(Op0, m_Sub(m_Value(Y), m_Value(X))))
150 Sub = Builder->CreateSub(X, Y, "suba");
151 else if (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))
152 Sub = Builder->CreateSub(Builder->CreateNeg(C1), Y, "subc");
155 BinaryOperator::CreateMul(Sub,
156 ConstantInt::get(Y->getType(), PosVal));
162 // Simplify mul instructions with a constant RHS.
163 if (isa<Constant>(Op1)) {
164 // Try to fold constant mul into select arguments.
165 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
166 if (Instruction *R = FoldOpIntoSelect(I, SI))
169 if (isa<PHINode>(Op0))
170 if (Instruction *NV = FoldOpIntoPhi(I))
174 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
175 if (Value *Op1v = dyn_castNegVal(Op1))
176 return BinaryOperator::CreateMul(Op0v, Op1v);
178 // (X / Y) * Y = X - (X % Y)
179 // (X / Y) * -Y = (X % Y) - X
182 BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0);
184 (BO->getOpcode() != Instruction::UDiv &&
185 BO->getOpcode() != Instruction::SDiv)) {
187 BO = dyn_cast<BinaryOperator>(Op1);
189 Value *Neg = dyn_castNegVal(Op1C);
190 if (BO && BO->hasOneUse() &&
191 (BO->getOperand(1) == Op1C || BO->getOperand(1) == Neg) &&
192 (BO->getOpcode() == Instruction::UDiv ||
193 BO->getOpcode() == Instruction::SDiv)) {
194 Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
196 // If the division is exact, X % Y is zero, so we end up with X or -X.
197 if (PossiblyExactOperator *SDiv = dyn_cast<PossiblyExactOperator>(BO))
198 if (SDiv->isExact()) {
200 return ReplaceInstUsesWith(I, Op0BO);
201 return BinaryOperator::CreateNeg(Op0BO);
205 if (BO->getOpcode() == Instruction::UDiv)
206 Rem = Builder->CreateURem(Op0BO, Op1BO);
208 Rem = Builder->CreateSRem(Op0BO, Op1BO);
212 return BinaryOperator::CreateSub(Op0BO, Rem);
213 return BinaryOperator::CreateSub(Rem, Op0BO);
217 /// i1 mul -> i1 and.
218 if (I.getType()->isIntegerTy(1))
219 return BinaryOperator::CreateAnd(Op0, Op1);
221 // X*(1 << Y) --> X << Y
222 // (1 << Y)*X --> X << Y
225 if (match(Op0, m_Shl(m_One(), m_Value(Y))))
226 return BinaryOperator::CreateShl(Op1, Y);
227 if (match(Op1, m_Shl(m_One(), m_Value(Y))))
228 return BinaryOperator::CreateShl(Op0, Y);
231 // If one of the operands of the multiply is a cast from a boolean value, then
232 // we know the bool is either zero or one, so this is a 'masking' multiply.
233 // X * Y (where Y is 0 or 1) -> X & (0-Y)
234 if (!I.getType()->isVectorTy()) {
235 // -2 is "-1 << 1" so it is all bits set except the low one.
236 APInt Negative2(I.getType()->getPrimitiveSizeInBits(), (uint64_t)-2, true);
238 Value *BoolCast = 0, *OtherOp = 0;
239 if (MaskedValueIsZero(Op0, Negative2))
240 BoolCast = Op0, OtherOp = Op1;
241 else if (MaskedValueIsZero(Op1, Negative2))
242 BoolCast = Op1, OtherOp = Op0;
245 Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()),
247 return BinaryOperator::CreateAnd(V, OtherOp);
251 return Changed ? &I : 0;
259 // And check for corresponding fast math flags
262 static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) {
264 if (!Op->hasOneUse())
267 IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op);
270 if (II->getIntrinsicID() != Intrinsic::log2 || !II->hasUnsafeAlgebra())
274 Value *OpLog2Of = II->getArgOperand(0);
275 if (!OpLog2Of->hasOneUse())
278 Instruction *I = dyn_cast<Instruction>(OpLog2Of);
281 if (I->getOpcode() != Instruction::FMul || !I->hasUnsafeAlgebra())
284 ConstantFP *CFP = dyn_cast<ConstantFP>(I->getOperand(0));
285 if (CFP && CFP->isExactlyValue(0.5)) {
286 Y = I->getOperand(1);
289 CFP = dyn_cast<ConstantFP>(I->getOperand(1));
290 if (CFP && CFP->isExactlyValue(0.5))
291 Y = I->getOperand(0);
294 /// Helper function of InstCombiner::visitFMul(BinaryOperator(). It returns
295 /// true iff the given value is FMul or FDiv with one and only one operand
296 /// being a normal constant (i.e. not Zero/NaN/Infinity).
297 static bool isFMulOrFDivWithConstant(Value *V) {
298 Instruction *I = dyn_cast<Instruction>(V);
299 if (!I || (I->getOpcode() != Instruction::FMul &&
300 I->getOpcode() != Instruction::FDiv)) {
304 ConstantFP *C0 = dyn_cast<ConstantFP>(I->getOperand(0));
305 ConstantFP *C1 = dyn_cast<ConstantFP>(I->getOperand(1));
310 return (C0 && C0->getValueAPF().isNormal()) ||
311 (C1 && C1->getValueAPF().isNormal());
314 static bool isNormalFp(const ConstantFP *C) {
315 const APFloat &Flt = C->getValueAPF();
316 return Flt.isNormal() && !Flt.isDenormal();
319 /// foldFMulConst() is a helper routine of InstCombiner::visitFMul().
320 /// The input \p FMulOrDiv is a FMul/FDiv with one and only one operand
321 /// being a constant (i.e. isFMulOrFDivWithConstant(FMulOrDiv) == true).
322 /// This function is to simplify "FMulOrDiv * C" and returns the
323 /// resulting expression. Note that this function could return NULL in
324 /// case the constants cannot be folded into a normal floating-point.
326 Value *InstCombiner::foldFMulConst
327 (Instruction *FMulOrDiv, ConstantFP *C, Instruction *InsertBefore) {
328 assert(isFMulOrFDivWithConstant(FMulOrDiv) && "V is invalid");
330 Value *Opnd0 = FMulOrDiv->getOperand(0);
331 Value *Opnd1 = FMulOrDiv->getOperand(1);
333 ConstantFP *C0 = dyn_cast<ConstantFP>(Opnd0);
334 ConstantFP *C1 = dyn_cast<ConstantFP>(Opnd1);
336 BinaryOperator *R = 0;
338 // (X * C0) * C => X * (C0*C)
339 if (FMulOrDiv->getOpcode() == Instruction::FMul) {
340 Constant *F = ConstantExpr::getFMul(C1 ? C1 : C0, C);
341 if (isNormalFp(cast<ConstantFP>(F)))
342 R = BinaryOperator::CreateFMul(C1 ? Opnd0 : Opnd1, F);
345 // (C0 / X) * C => (C0 * C) / X
346 ConstantFP *F = cast<ConstantFP>(ConstantExpr::getFMul(C0, C));
348 R = BinaryOperator::CreateFDiv(F, Opnd1);
350 // (X / C1) * C => X * (C/C1) if C/C1 is not a denormal
351 ConstantFP *F = cast<ConstantFP>(ConstantExpr::getFDiv(C, C1));
353 R = BinaryOperator::CreateFMul(Opnd0, F);
355 // (X / C1) * C => X / (C1/C)
356 Constant *F = ConstantExpr::getFDiv(C1, C);
357 if (isNormalFp(cast<ConstantFP>(F)))
358 R = BinaryOperator::CreateFDiv(Opnd0, F);
364 R->setHasUnsafeAlgebra(true);
365 InsertNewInstWith(R, *InsertBefore);
371 Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
372 bool Changed = SimplifyAssociativeOrCommutative(I);
373 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
375 if (isa<Constant>(Op0))
378 if (Value *V = SimplifyFMulInst(Op0, Op1, I.getFastMathFlags(), TD))
379 return ReplaceInstUsesWith(I, V);
381 // Simplify mul instructions with a constant RHS.
382 if (isa<Constant>(Op1)) {
383 // Try to fold constant mul into select arguments.
384 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
385 if (Instruction *R = FoldOpIntoSelect(I, SI))
388 if (isa<PHINode>(Op0))
389 if (Instruction *NV = FoldOpIntoPhi(I))
392 ConstantFP *C = dyn_cast<ConstantFP>(Op1);
393 if (C && I.hasUnsafeAlgebra() && C->getValueAPF().isNormal()) {
394 // Let MDC denote an expression in one of these forms:
395 // X * C, C/X, X/C, where C is a constant.
397 // Try to simplify "MDC * Constant"
398 if (isFMulOrFDivWithConstant(Op0)) {
399 Value *V = foldFMulConst(cast<Instruction>(Op0), C, &I);
401 return ReplaceInstUsesWith(I, V);
404 // (MDC +/- C1) * C2 => (MDC * C2) +/- (C1 * C2)
405 Instruction *FAddSub = dyn_cast<Instruction>(Op0);
407 (FAddSub->getOpcode() == Instruction::FAdd ||
408 FAddSub->getOpcode() == Instruction::FSub)) {
409 Value *Opnd0 = FAddSub->getOperand(0);
410 Value *Opnd1 = FAddSub->getOperand(1);
411 ConstantFP *C0 = dyn_cast<ConstantFP>(Opnd0);
412 ConstantFP *C1 = dyn_cast<ConstantFP>(Opnd1);
415 std::swap(C0, C1); std::swap(Opnd0, Opnd1); Swap = true;
418 if (C1 && C1->getValueAPF().isNormal() &&
419 isFMulOrFDivWithConstant(Opnd0)) {
420 Value *M0 = ConstantExpr::getFMul(C1, C);
421 Value *M1 = isNormalFp(cast<ConstantFP>(M0)) ?
422 foldFMulConst(cast<Instruction>(Opnd0), C, &I) :
425 if (Swap && FAddSub->getOpcode() == Instruction::FSub)
428 Value *R = (FAddSub->getOpcode() == Instruction::FAdd) ?
429 BinaryOperator::CreateFAdd(M0, M1) :
430 BinaryOperator::CreateFSub(M0, M1);
431 Instruction *RI = cast<Instruction>(R);
432 RI->setHasUnsafeAlgebra(true);
440 if (Value *Op0v = dyn_castFNegVal(Op0)) // -X * -Y = X*Y
441 if (Value *Op1v = dyn_castFNegVal(Op1))
442 return BinaryOperator::CreateFMul(Op0v, Op1v);
444 // Under unsafe algebra do:
445 // X * log2(0.5*Y) = X*log2(Y) - X
446 if (I.hasUnsafeAlgebra()) {
450 detectLog2OfHalf(Op0, OpY, Log2);
454 detectLog2OfHalf(Op1, OpY, Log2);
459 // if pattern detected emit alternate sequence
461 Log2->setArgOperand(0, OpY);
462 Value *FMulVal = Builder->CreateFMul(OpX, Log2);
463 Instruction *FMul = cast<Instruction>(FMulVal);
464 FMul->copyFastMathFlags(Log2);
465 Instruction *FSub = BinaryOperator::CreateFSub(FMulVal, OpX);
466 FSub->copyFastMathFlags(Log2);
471 // X * cond ? 1.0 : 0.0 => cond ? X : 0.0
472 if (I.hasNoNaNs() && I.hasNoSignedZeros()) {
473 Value *V0 = I.getOperand(0);
474 Value *V1 = I.getOperand(1);
475 Value *Cond, *SLHS, *SRHS;
478 if (match(V0, m_Select(m_Value(Cond), m_Value(SLHS), m_Value(SRHS)))) {
480 } else if (match(V1, m_Select(m_Value(Cond), m_Value(SLHS),
487 ConstantFP *C0 = dyn_cast<ConstantFP>(SLHS);
488 ConstantFP *C1 = dyn_cast<ConstantFP>(SRHS);
491 ((C0->isZero() && C1->isExactlyValue(1.0)) ||
492 (C1->isZero() && C0->isExactlyValue(1.0)))) {
495 T = Builder->CreateSelect(Cond, SLHS, V1);
497 T = Builder->CreateSelect(Cond, V1, SRHS);
498 return ReplaceInstUsesWith(I, T);
503 return Changed ? &I : 0;
506 /// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
508 bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
509 SelectInst *SI = cast<SelectInst>(I.getOperand(1));
511 // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
512 int NonNullOperand = -1;
513 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
514 if (ST->isNullValue())
516 // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
517 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
518 if (ST->isNullValue())
521 if (NonNullOperand == -1)
524 Value *SelectCond = SI->getOperand(0);
526 // Change the div/rem to use 'Y' instead of the select.
527 I.setOperand(1, SI->getOperand(NonNullOperand));
529 // Okay, we know we replace the operand of the div/rem with 'Y' with no
530 // problem. However, the select, or the condition of the select may have
531 // multiple uses. Based on our knowledge that the operand must be non-zero,
532 // propagate the known value for the select into other uses of it, and
533 // propagate a known value of the condition into its other users.
535 // If the select and condition only have a single use, don't bother with this,
537 if (SI->use_empty() && SelectCond->hasOneUse())
540 // Scan the current block backward, looking for other uses of SI.
541 BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
543 while (BBI != BBFront) {
545 // If we found a call to a function, we can't assume it will return, so
546 // information from below it cannot be propagated above it.
547 if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
550 // Replace uses of the select or its condition with the known values.
551 for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
554 *I = SI->getOperand(NonNullOperand);
556 } else if (*I == SelectCond) {
557 *I = NonNullOperand == 1 ? ConstantInt::getTrue(BBI->getContext()) :
558 ConstantInt::getFalse(BBI->getContext());
563 // If we past the instruction, quit looking for it.
566 if (&*BBI == SelectCond)
569 // If we ran out of things to eliminate, break out of the loop.
570 if (SelectCond == 0 && SI == 0)
578 /// This function implements the transforms common to both integer division
579 /// instructions (udiv and sdiv). It is called by the visitors to those integer
580 /// division instructions.
581 /// @brief Common integer divide transforms
582 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
583 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
585 // The RHS is known non-zero.
586 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) {
591 // Handle cases involving: [su]div X, (select Cond, Y, Z)
592 // This does not apply for fdiv.
593 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
596 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
597 // (X / C1) / C2 -> X / (C1*C2)
598 if (Instruction *LHS = dyn_cast<Instruction>(Op0))
599 if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode())
600 if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
601 if (MultiplyOverflows(RHS, LHSRHS,
602 I.getOpcode()==Instruction::SDiv))
603 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
604 return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0),
605 ConstantExpr::getMul(RHS, LHSRHS));
608 if (!RHS->isZero()) { // avoid X udiv 0
609 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
610 if (Instruction *R = FoldOpIntoSelect(I, SI))
612 if (isa<PHINode>(Op0))
613 if (Instruction *NV = FoldOpIntoPhi(I))
618 // See if we can fold away this div instruction.
619 if (SimplifyDemandedInstructionBits(I))
622 // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
623 Value *X = 0, *Z = 0;
624 if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
625 bool isSigned = I.getOpcode() == Instruction::SDiv;
626 if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
627 (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
628 return BinaryOperator::Create(I.getOpcode(), X, Op1);
634 /// dyn_castZExtVal - Checks if V is a zext or constant that can
635 /// be truncated to Ty without losing bits.
636 static Value *dyn_castZExtVal(Value *V, Type *Ty) {
637 if (ZExtInst *Z = dyn_cast<ZExtInst>(V)) {
638 if (Z->getSrcTy() == Ty)
639 return Z->getOperand(0);
640 } else if (ConstantInt *C = dyn_cast<ConstantInt>(V)) {
641 if (C->getValue().getActiveBits() <= cast<IntegerType>(Ty)->getBitWidth())
642 return ConstantExpr::getTrunc(C, Ty);
647 Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
648 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
650 if (Value *V = SimplifyUDivInst(Op0, Op1, TD))
651 return ReplaceInstUsesWith(I, V);
653 // Handle the integer div common cases
654 if (Instruction *Common = commonIDivTransforms(I))
658 // X udiv 2^C -> X >> C
659 // Check to see if this is an unsigned division with an exact power of 2,
660 // if so, convert to a right shift.
662 if (match(Op1, m_Power2(C))) {
663 BinaryOperator *LShr =
664 BinaryOperator::CreateLShr(Op0,
665 ConstantInt::get(Op0->getType(),
667 if (I.isExact()) LShr->setIsExact();
672 if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
673 // X udiv C, where C >= signbit
674 if (C->getValue().isNegative()) {
675 Value *IC = Builder->CreateICmpULT(Op0, C);
676 return SelectInst::Create(IC, Constant::getNullValue(I.getType()),
677 ConstantInt::get(I.getType(), 1));
681 // (x lshr C1) udiv C2 --> x udiv (C2 << C1)
682 if (ConstantInt *C2 = dyn_cast<ConstantInt>(Op1)) {
685 if (match(Op0, m_LShr(m_Value(X), m_ConstantInt(C1)))) {
686 APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1));
687 return BinaryOperator::CreateUDiv(X, Builder->getInt(NC));
691 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
692 { const APInt *CI; Value *N;
693 if (match(Op1, m_Shl(m_Power2(CI), m_Value(N))) ||
694 match(Op1, m_ZExt(m_Shl(m_Power2(CI), m_Value(N))))) {
696 N = Builder->CreateAdd(N,
697 ConstantInt::get(N->getType(), CI->logBase2()));
698 if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
699 N = Builder->CreateZExt(N, Z->getDestTy());
701 return BinaryOperator::CreateExactLShr(Op0, N);
702 return BinaryOperator::CreateLShr(Op0, N);
706 // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2)
707 // where C1&C2 are powers of two.
708 { Value *Cond; const APInt *C1, *C2;
709 if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) {
710 // Construct the "on true" case of the select
711 Value *TSI = Builder->CreateLShr(Op0, C1->logBase2(), Op1->getName()+".t",
714 // Construct the "on false" case of the select
715 Value *FSI = Builder->CreateLShr(Op0, C2->logBase2(), Op1->getName()+".f",
718 // construct the select instruction and return it.
719 return SelectInst::Create(Cond, TSI, FSI);
723 // (zext A) udiv (zext B) --> zext (A udiv B)
724 if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
725 if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
726 return new ZExtInst(Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div",
733 Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
734 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
736 if (Value *V = SimplifySDivInst(Op0, Op1, TD))
737 return ReplaceInstUsesWith(I, V);
739 // Handle the integer div common cases
740 if (Instruction *Common = commonIDivTransforms(I))
743 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
745 if (RHS->isAllOnesValue())
746 return BinaryOperator::CreateNeg(Op0);
748 // sdiv X, C --> ashr exact X, log2(C)
749 if (I.isExact() && RHS->getValue().isNonNegative() &&
750 RHS->getValue().isPowerOf2()) {
751 Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
752 RHS->getValue().exactLogBase2());
753 return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName());
756 // -X/C --> X/-C provided the negation doesn't overflow.
757 if (SubOperator *Sub = dyn_cast<SubOperator>(Op0))
758 if (match(Sub->getOperand(0), m_Zero()) && Sub->hasNoSignedWrap())
759 return BinaryOperator::CreateSDiv(Sub->getOperand(1),
760 ConstantExpr::getNeg(RHS));
763 // If the sign bits of both operands are zero (i.e. we can prove they are
764 // unsigned inputs), turn this into a udiv.
765 if (I.getType()->isIntegerTy()) {
766 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
767 if (MaskedValueIsZero(Op0, Mask)) {
768 if (MaskedValueIsZero(Op1, Mask)) {
769 // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
770 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
773 if (match(Op1, m_Shl(m_Power2(), m_Value()))) {
774 // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
775 // Safe because the only negative value (1 << Y) can take on is
776 // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
778 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
786 Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
787 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
789 if (Value *V = SimplifyFDivInst(Op0, Op1, TD))
790 return ReplaceInstUsesWith(I, V);
792 if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) {
793 const APFloat &Op1F = Op1C->getValueAPF();
795 // If the divisor has an exact multiplicative inverse we can turn the fdiv
796 // into a cheaper fmul.
797 APFloat Reciprocal(Op1F.getSemantics());
798 if (Op1F.getExactInverse(&Reciprocal)) {
799 ConstantFP *RFP = ConstantFP::get(Builder->getContext(), Reciprocal);
800 return BinaryOperator::CreateFMul(Op0, RFP);
807 /// This function implements the transforms common to both integer remainder
808 /// instructions (urem and srem). It is called by the visitors to those integer
809 /// remainder instructions.
810 /// @brief Common integer remainder transforms
811 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
812 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
814 // The RHS is known non-zero.
815 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) {
820 // Handle cases involving: rem X, (select Cond, Y, Z)
821 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
824 if (isa<ConstantInt>(Op1)) {
825 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
826 if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
827 if (Instruction *R = FoldOpIntoSelect(I, SI))
829 } else if (isa<PHINode>(Op0I)) {
830 if (Instruction *NV = FoldOpIntoPhi(I))
834 // See if we can fold away this rem instruction.
835 if (SimplifyDemandedInstructionBits(I))
843 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
844 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
846 if (Value *V = SimplifyURemInst(Op0, Op1, TD))
847 return ReplaceInstUsesWith(I, V);
849 if (Instruction *common = commonIRemTransforms(I))
852 // X urem C^2 -> X and C-1
854 if (match(Op1, m_Power2(C)))
855 return BinaryOperator::CreateAnd(Op0,
856 ConstantInt::get(I.getType(), *C-1));
859 // Turn A % (C << N), where C is 2^k, into A & ((C << N)-1)
860 if (match(Op1, m_Shl(m_Power2(), m_Value()))) {
861 Constant *N1 = Constant::getAllOnesValue(I.getType());
862 Value *Add = Builder->CreateAdd(Op1, N1);
863 return BinaryOperator::CreateAnd(Op0, Add);
866 // urem X, (select Cond, 2^C1, 2^C2) -->
867 // select Cond, (and X, C1-1), (and X, C2-1)
868 // when C1&C2 are powers of two.
869 { Value *Cond; const APInt *C1, *C2;
870 if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) {
871 Value *TrueAnd = Builder->CreateAnd(Op0, *C1-1, Op1->getName()+".t");
872 Value *FalseAnd = Builder->CreateAnd(Op0, *C2-1, Op1->getName()+".f");
873 return SelectInst::Create(Cond, TrueAnd, FalseAnd);
877 // (zext A) urem (zext B) --> zext (A urem B)
878 if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
879 if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
880 return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
886 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
887 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
889 if (Value *V = SimplifySRemInst(Op0, Op1, TD))
890 return ReplaceInstUsesWith(I, V);
892 // Handle the integer rem common cases
893 if (Instruction *Common = commonIRemTransforms(I))
896 if (Value *RHSNeg = dyn_castNegVal(Op1))
897 if (!isa<Constant>(RHSNeg) ||
898 (isa<ConstantInt>(RHSNeg) &&
899 cast<ConstantInt>(RHSNeg)->getValue().isStrictlyPositive())) {
901 Worklist.AddValue(I.getOperand(1));
902 I.setOperand(1, RHSNeg);
906 // If the sign bits of both operands are zero (i.e. we can prove they are
907 // unsigned inputs), turn this into a urem.
908 if (I.getType()->isIntegerTy()) {
909 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
910 if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
911 // X srem Y -> X urem Y, iff X and Y don't have sign bit set
912 return BinaryOperator::CreateURem(Op0, Op1, I.getName());
916 // If it's a constant vector, flip any negative values positive.
917 if (isa<ConstantVector>(Op1) || isa<ConstantDataVector>(Op1)) {
918 Constant *C = cast<Constant>(Op1);
919 unsigned VWidth = C->getType()->getVectorNumElements();
921 bool hasNegative = false;
922 bool hasMissing = false;
923 for (unsigned i = 0; i != VWidth; ++i) {
924 Constant *Elt = C->getAggregateElement(i);
930 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elt))
931 if (RHS->isNegative())
935 if (hasNegative && !hasMissing) {
936 SmallVector<Constant *, 16> Elts(VWidth);
937 for (unsigned i = 0; i != VWidth; ++i) {
938 Elts[i] = C->getAggregateElement(i); // Handle undef, etc.
939 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elts[i])) {
940 if (RHS->isNegative())
941 Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
945 Constant *NewRHSV = ConstantVector::get(Elts);
946 if (NewRHSV != C) { // Don't loop on -MININT
947 Worklist.AddValue(I.getOperand(1));
948 I.setOperand(1, NewRHSV);
957 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
958 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
960 if (Value *V = SimplifyFRemInst(Op0, Op1, TD))
961 return ReplaceInstUsesWith(I, V);
963 // Handle cases involving: rem X, (select Cond, Y, Z)
964 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))