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/IntrinsicInst.h"
17 #include "llvm/Analysis/InstructionSimplify.h"
18 #include "llvm/Support/PatternMatch.h"
20 using namespace PatternMatch;
22 /// SubOne - Subtract one from a ConstantInt.
23 static Constant *SubOne(ConstantInt *C) {
24 return ConstantInt::get(C->getContext(), C->getValue()-1);
27 /// MultiplyOverflows - True if the multiply can not be expressed in an int
29 static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) {
30 uint32_t W = C1->getBitWidth();
31 APInt LHSExt = C1->getValue(), RHSExt = C2->getValue();
33 LHSExt = LHSExt.sext(W * 2);
34 RHSExt = RHSExt.sext(W * 2);
36 LHSExt = LHSExt.zext(W * 2);
37 RHSExt = RHSExt.zext(W * 2);
40 APInt MulExt = LHSExt * RHSExt;
43 return MulExt.ugt(APInt::getLowBitsSet(W * 2, W));
45 APInt Min = APInt::getSignedMinValue(W).sext(W * 2);
46 APInt Max = APInt::getSignedMaxValue(W).sext(W * 2);
47 return MulExt.slt(Min) || MulExt.sgt(Max);
50 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
51 bool Changed = SimplifyAssociativeOrCommutative(I);
52 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
54 if (Value *V = SimplifyMulInst(Op0, Op1, TD))
55 return ReplaceInstUsesWith(I, V);
57 if (Value *V = SimplifyUsingDistributiveLaws(I))
58 return ReplaceInstUsesWith(I, V);
60 // Simplify mul instructions with a constant RHS.
61 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
62 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1C)) {
64 // ((X << C1)*C2) == (X * (C2 << C1))
65 if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op0))
66 if (SI->getOpcode() == Instruction::Shl)
67 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
68 return BinaryOperator::CreateMul(SI->getOperand(0),
69 ConstantExpr::getShl(CI, ShOp));
71 if (CI->isAllOnesValue()) // X * -1 == 0 - X
72 return BinaryOperator::CreateNeg(Op0, I.getName());
74 const APInt& Val = cast<ConstantInt>(CI)->getValue();
75 if (Val.isPowerOf2()) { // Replace X*(2^C) with X << C
76 return BinaryOperator::CreateShl(Op0,
77 ConstantInt::get(Op0->getType(), Val.logBase2()));
79 } else if (Op1C->getType()->isVectorTy()) {
80 if (Op1C->isNullValue())
81 return ReplaceInstUsesWith(I, Op1C);
83 if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1C)) {
84 if (Op1V->isAllOnesValue()) // X * -1 == 0 - X
85 return BinaryOperator::CreateNeg(Op0, I.getName());
87 // As above, vector X*splat(1.0) -> X in all defined cases.
88 if (Constant *Splat = Op1V->getSplatValue()) {
89 if (ConstantInt *CI = dyn_cast<ConstantInt>(Splat))
91 return ReplaceInstUsesWith(I, Op0);
96 if (BinaryOperator *Op0I = dyn_cast<BinaryOperator>(Op0))
97 if (Op0I->getOpcode() == Instruction::Add && Op0I->hasOneUse() &&
98 isa<ConstantInt>(Op0I->getOperand(1)) && isa<ConstantInt>(Op1C)) {
99 // Canonicalize (X+C1)*C2 -> X*C2+C1*C2.
100 Value *Add = Builder->CreateMul(Op0I->getOperand(0), Op1C, "tmp");
101 Value *C1C2 = Builder->CreateMul(Op1C, Op0I->getOperand(1));
102 return BinaryOperator::CreateAdd(Add, C1C2);
106 // Try to fold constant mul into select arguments.
107 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
108 if (Instruction *R = FoldOpIntoSelect(I, SI))
111 if (isa<PHINode>(Op0))
112 if (Instruction *NV = FoldOpIntoPhi(I))
116 if (Value *Op0v = dyn_castNegVal(Op0)) // -X * -Y = X*Y
117 if (Value *Op1v = dyn_castNegVal(Op1))
118 return BinaryOperator::CreateMul(Op0v, Op1v);
120 // (X / Y) * Y = X - (X % Y)
121 // (X / Y) * -Y = (X % Y) - X
124 BinaryOperator *BO = dyn_cast<BinaryOperator>(Op0);
126 (BO->getOpcode() != Instruction::UDiv &&
127 BO->getOpcode() != Instruction::SDiv)) {
129 BO = dyn_cast<BinaryOperator>(Op1);
131 Value *Neg = dyn_castNegVal(Op1C);
132 if (BO && BO->hasOneUse() &&
133 (BO->getOperand(1) == Op1C || BO->getOperand(1) == Neg) &&
134 (BO->getOpcode() == Instruction::UDiv ||
135 BO->getOpcode() == Instruction::SDiv)) {
136 Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
138 // If the division is exact, X % Y is zero.
139 if (SDivOperator *SDiv = dyn_cast<SDivOperator>(BO))
140 if (SDiv->isExact()) {
142 return ReplaceInstUsesWith(I, Op0BO);
143 return BinaryOperator::CreateNeg(Op0BO);
147 if (BO->getOpcode() == Instruction::UDiv)
148 Rem = Builder->CreateURem(Op0BO, Op1BO);
150 Rem = Builder->CreateSRem(Op0BO, Op1BO);
154 return BinaryOperator::CreateSub(Op0BO, Rem);
155 return BinaryOperator::CreateSub(Rem, Op0BO);
159 /// i1 mul -> i1 and.
160 if (I.getType()->isIntegerTy(1))
161 return BinaryOperator::CreateAnd(Op0, Op1);
163 // X*(1 << Y) --> X << Y
164 // (1 << Y)*X --> X << Y
167 if (match(Op0, m_Shl(m_One(), m_Value(Y))))
168 return BinaryOperator::CreateShl(Op1, Y);
169 if (match(Op1, m_Shl(m_One(), m_Value(Y))))
170 return BinaryOperator::CreateShl(Op0, Y);
173 // If one of the operands of the multiply is a cast from a boolean value, then
174 // we know the bool is either zero or one, so this is a 'masking' multiply.
175 // X * Y (where Y is 0 or 1) -> X & (0-Y)
176 if (!I.getType()->isVectorTy()) {
177 // -2 is "-1 << 1" so it is all bits set except the low one.
178 APInt Negative2(I.getType()->getPrimitiveSizeInBits(), (uint64_t)-2, true);
180 Value *BoolCast = 0, *OtherOp = 0;
181 if (MaskedValueIsZero(Op0, Negative2))
182 BoolCast = Op0, OtherOp = Op1;
183 else if (MaskedValueIsZero(Op1, Negative2))
184 BoolCast = Op1, OtherOp = Op0;
187 Value *V = Builder->CreateSub(Constant::getNullValue(I.getType()),
189 return BinaryOperator::CreateAnd(V, OtherOp);
193 return Changed ? &I : 0;
196 Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
197 bool Changed = SimplifyAssociativeOrCommutative(I);
198 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
200 // Simplify mul instructions with a constant RHS...
201 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
202 if (ConstantFP *Op1F = dyn_cast<ConstantFP>(Op1C)) {
203 // "In IEEE floating point, x*1 is not equivalent to x for nans. However,
204 // ANSI says we can drop signals, so we can do this anyway." (from GCC)
205 if (Op1F->isExactlyValue(1.0))
206 return ReplaceInstUsesWith(I, Op0); // Eliminate 'fmul double %X, 1.0'
207 } else if (Op1C->getType()->isVectorTy()) {
208 if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1C)) {
209 // As above, vector X*splat(1.0) -> X in all defined cases.
210 if (Constant *Splat = Op1V->getSplatValue()) {
211 if (ConstantFP *F = dyn_cast<ConstantFP>(Splat))
212 if (F->isExactlyValue(1.0))
213 return ReplaceInstUsesWith(I, Op0);
218 // Try to fold constant mul into select arguments.
219 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
220 if (Instruction *R = FoldOpIntoSelect(I, SI))
223 if (isa<PHINode>(Op0))
224 if (Instruction *NV = FoldOpIntoPhi(I))
228 if (Value *Op0v = dyn_castFNegVal(Op0)) // -X * -Y = X*Y
229 if (Value *Op1v = dyn_castFNegVal(Op1))
230 return BinaryOperator::CreateFMul(Op0v, Op1v);
232 return Changed ? &I : 0;
235 /// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
237 bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
238 SelectInst *SI = cast<SelectInst>(I.getOperand(1));
240 // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
241 int NonNullOperand = -1;
242 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
243 if (ST->isNullValue())
245 // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
246 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
247 if (ST->isNullValue())
250 if (NonNullOperand == -1)
253 Value *SelectCond = SI->getOperand(0);
255 // Change the div/rem to use 'Y' instead of the select.
256 I.setOperand(1, SI->getOperand(NonNullOperand));
258 // Okay, we know we replace the operand of the div/rem with 'Y' with no
259 // problem. However, the select, or the condition of the select may have
260 // multiple uses. Based on our knowledge that the operand must be non-zero,
261 // propagate the known value for the select into other uses of it, and
262 // propagate a known value of the condition into its other users.
264 // If the select and condition only have a single use, don't bother with this,
266 if (SI->use_empty() && SelectCond->hasOneUse())
269 // Scan the current block backward, looking for other uses of SI.
270 BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
272 while (BBI != BBFront) {
274 // If we found a call to a function, we can't assume it will return, so
275 // information from below it cannot be propagated above it.
276 if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
279 // Replace uses of the select or its condition with the known values.
280 for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
283 *I = SI->getOperand(NonNullOperand);
285 } else if (*I == SelectCond) {
286 *I = NonNullOperand == 1 ? ConstantInt::getTrue(BBI->getContext()) :
287 ConstantInt::getFalse(BBI->getContext());
292 // If we past the instruction, quit looking for it.
295 if (&*BBI == SelectCond)
298 // If we ran out of things to eliminate, break out of the loop.
299 if (SelectCond == 0 && SI == 0)
307 /// This function implements the transforms common to both integer division
308 /// instructions (udiv and sdiv). It is called by the visitors to those integer
309 /// division instructions.
310 /// @brief Common integer divide transforms
311 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
312 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
314 // Handle cases involving: [su]div X, (select Cond, Y, Z)
315 // This does not apply for fdiv.
316 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
319 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
320 // (X / C1) / C2 -> X / (C1*C2)
321 if (Instruction *LHS = dyn_cast<Instruction>(Op0))
322 if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode())
323 if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
324 if (MultiplyOverflows(RHS, LHSRHS,
325 I.getOpcode()==Instruction::SDiv))
326 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
328 return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0),
329 ConstantExpr::getMul(RHS, LHSRHS));
332 if (!RHS->isZero()) { // avoid X udiv 0
333 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
334 if (Instruction *R = FoldOpIntoSelect(I, SI))
336 if (isa<PHINode>(Op0))
337 if (Instruction *NV = FoldOpIntoPhi(I))
342 // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
343 Value *X = 0, *Z = 0;
344 if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
345 bool isSigned = I.getOpcode() == Instruction::SDiv;
346 if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
347 (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
348 return BinaryOperator::Create(I.getOpcode(), X, Op1);
354 Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
355 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
357 if (Value *V = SimplifyUDivInst(Op0, Op1, TD))
358 return ReplaceInstUsesWith(I, V);
360 // Handle the integer div common cases
361 if (Instruction *Common = commonIDivTransforms(I))
364 if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
365 // X udiv 2^C -> X >> C
366 // Check to see if this is an unsigned division with an exact power of 2,
367 // if so, convert to a right shift.
368 if (C->getValue().isPowerOf2()) // 0 not included in isPowerOf2
369 return BinaryOperator::CreateLShr(Op0,
370 ConstantInt::get(Op0->getType(), C->getValue().logBase2()));
372 // X udiv C, where C >= signbit
373 if (C->getValue().isNegative()) {
374 Value *IC = Builder->CreateICmpULT( Op0, C);
375 return SelectInst::Create(IC, Constant::getNullValue(I.getType()),
376 ConstantInt::get(I.getType(), 1));
380 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
381 if (BinaryOperator *RHSI = dyn_cast<BinaryOperator>(I.getOperand(1))) {
382 if (RHSI->getOpcode() == Instruction::Shl &&
383 isa<ConstantInt>(RHSI->getOperand(0))) {
384 const APInt& C1 = cast<ConstantInt>(RHSI->getOperand(0))->getValue();
385 if (C1.isPowerOf2()) {
386 Value *N = RHSI->getOperand(1);
387 const Type *NTy = N->getType();
388 if (uint32_t C2 = C1.logBase2())
389 N = Builder->CreateAdd(N, ConstantInt::get(NTy, C2), "tmp");
390 return BinaryOperator::CreateLShr(Op0, N);
395 // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2)
396 // where C1&C2 are powers of two.
397 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
398 if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
399 if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
400 const APInt &TVA = STO->getValue(), &FVA = SFO->getValue();
401 if (TVA.isPowerOf2() && FVA.isPowerOf2()) {
402 // Compute the shift amounts
403 uint32_t TSA = TVA.logBase2(), FSA = FVA.logBase2();
404 // Construct the "on true" case of the select
405 Constant *TC = ConstantInt::get(Op0->getType(), TSA);
406 Value *TSI = Builder->CreateLShr(Op0, TC, SI->getName()+".t");
408 // Construct the "on false" case of the select
409 Constant *FC = ConstantInt::get(Op0->getType(), FSA);
410 Value *FSI = Builder->CreateLShr(Op0, FC, SI->getName()+".f");
412 // construct the select instruction and return it.
413 return SelectInst::Create(SI->getOperand(0), TSI, FSI, SI->getName());
419 Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
420 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
422 if (Value *V = SimplifySDivInst(Op0, Op1, TD))
423 return ReplaceInstUsesWith(I, V);
425 // Handle the integer div common cases
426 if (Instruction *Common = commonIDivTransforms(I))
429 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
431 if (RHS->isAllOnesValue())
432 return BinaryOperator::CreateNeg(Op0);
434 // sdiv X, C --> ashr X, log2(C)
435 if (cast<SDivOperator>(&I)->isExact() &&
436 RHS->getValue().isNonNegative() &&
437 RHS->getValue().isPowerOf2()) {
438 Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
439 RHS->getValue().exactLogBase2());
440 return BinaryOperator::CreateAShr(Op0, ShAmt, I.getName());
443 // -X/C --> X/-C provided the negation doesn't overflow.
444 if (SubOperator *Sub = dyn_cast<SubOperator>(Op0))
445 if (isa<Constant>(Sub->getOperand(0)) &&
446 cast<Constant>(Sub->getOperand(0))->isNullValue() &&
447 Sub->hasNoSignedWrap())
448 return BinaryOperator::CreateSDiv(Sub->getOperand(1),
449 ConstantExpr::getNeg(RHS));
452 // If the sign bits of both operands are zero (i.e. we can prove they are
453 // unsigned inputs), turn this into a udiv.
454 if (I.getType()->isIntegerTy()) {
455 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
456 if (MaskedValueIsZero(Op0, Mask)) {
457 if (MaskedValueIsZero(Op1, Mask)) {
458 // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
459 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
461 ConstantInt *ShiftedInt;
462 if (match(Op1, m_Shl(m_ConstantInt(ShiftedInt), m_Value())) &&
463 ShiftedInt->getValue().isPowerOf2()) {
464 // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
465 // Safe because the only negative value (1 << Y) can take on is
466 // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
468 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
476 /// This function implements the transforms on rem instructions that work
477 /// regardless of the kind of rem instruction it is (urem, srem, or frem). It
478 /// is used by the visitors to those instructions.
479 /// @brief Transforms common to all three rem instructions
480 Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
481 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
483 if (isa<UndefValue>(Op0)) { // undef % X -> 0
484 if (I.getType()->isFPOrFPVectorTy())
485 return ReplaceInstUsesWith(I, Op0); // X % undef -> undef (could be SNaN)
486 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
488 if (isa<UndefValue>(Op1))
489 return ReplaceInstUsesWith(I, Op1); // X % undef -> undef
491 // Handle cases involving: rem X, (select Cond, Y, Z)
492 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
498 /// This function implements the transforms common to both integer remainder
499 /// instructions (urem and srem). It is called by the visitors to those integer
500 /// remainder instructions.
501 /// @brief Common integer remainder transforms
502 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
503 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
505 if (Instruction *common = commonRemTransforms(I))
510 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
512 // 0 % X == 0 for integer, we don't need to preserve faults!
513 if (Constant *LHS = dyn_cast<Constant>(Op0))
514 if (LHS->isNullValue())
515 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
517 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
518 // X % 0 == undef, we don't need to preserve faults!
519 if (RHS->equalsInt(0))
520 return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
522 if (RHS->equalsInt(1)) // X % 1 == 0
523 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
525 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
526 if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
527 if (Instruction *R = FoldOpIntoSelect(I, SI))
529 } else if (isa<PHINode>(Op0I)) {
530 if (Instruction *NV = FoldOpIntoPhi(I))
534 // See if we can fold away this rem instruction.
535 if (SimplifyDemandedInstructionBits(I))
543 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
544 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
546 if (Instruction *common = commonIRemTransforms(I))
549 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
550 // X urem C^2 -> X and C
551 // Check to see if this is an unsigned remainder with an exact power of 2,
552 // if so, convert to a bitwise and.
553 if (ConstantInt *C = dyn_cast<ConstantInt>(RHS))
554 if (C->getValue().isPowerOf2())
555 return BinaryOperator::CreateAnd(Op0, SubOne(C));
558 if (Instruction *RHSI = dyn_cast<Instruction>(I.getOperand(1))) {
559 // Turn A % (C << N), where C is 2^k, into A & ((C << N)-1)
560 if (RHSI->getOpcode() == Instruction::Shl &&
561 isa<ConstantInt>(RHSI->getOperand(0))) {
562 if (cast<ConstantInt>(RHSI->getOperand(0))->getValue().isPowerOf2()) {
563 Constant *N1 = Constant::getAllOnesValue(I.getType());
564 Value *Add = Builder->CreateAdd(RHSI, N1, "tmp");
565 return BinaryOperator::CreateAnd(Op0, Add);
570 // urem X, (select Cond, 2^C1, 2^C2) --> select Cond, (and X, C1), (and X, C2)
571 // where C1&C2 are powers of two.
572 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
573 if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
574 if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
575 // STO == 0 and SFO == 0 handled above.
576 if ((STO->getValue().isPowerOf2()) &&
577 (SFO->getValue().isPowerOf2())) {
578 Value *TrueAnd = Builder->CreateAnd(Op0, SubOne(STO),
580 Value *FalseAnd = Builder->CreateAnd(Op0, SubOne(SFO),
582 return SelectInst::Create(SI->getOperand(0), TrueAnd, FalseAnd);
590 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
591 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
593 // Handle the integer rem common cases
594 if (Instruction *Common = commonIRemTransforms(I))
597 if (Value *RHSNeg = dyn_castNegVal(Op1))
598 if (!isa<Constant>(RHSNeg) ||
599 (isa<ConstantInt>(RHSNeg) &&
600 cast<ConstantInt>(RHSNeg)->getValue().isStrictlyPositive())) {
602 Worklist.AddValue(I.getOperand(1));
603 I.setOperand(1, RHSNeg);
607 // If the sign bits of both operands are zero (i.e. we can prove they are
608 // unsigned inputs), turn this into a urem.
609 if (I.getType()->isIntegerTy()) {
610 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
611 if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
612 // X srem Y -> X urem Y, iff X and Y don't have sign bit set
613 return BinaryOperator::CreateURem(Op0, Op1, I.getName());
617 // If it's a constant vector, flip any negative values positive.
618 if (ConstantVector *RHSV = dyn_cast<ConstantVector>(Op1)) {
619 unsigned VWidth = RHSV->getNumOperands();
621 bool hasNegative = false;
622 for (unsigned i = 0; !hasNegative && i != VWidth; ++i)
623 if (ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV->getOperand(i)))
624 if (RHS->getValue().isNegative())
628 std::vector<Constant *> Elts(VWidth);
629 for (unsigned i = 0; i != VWidth; ++i) {
630 if (ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV->getOperand(i))) {
631 if (RHS->getValue().isNegative())
632 Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
638 Constant *NewRHSV = ConstantVector::get(Elts);
639 if (NewRHSV != RHSV) {
640 Worklist.AddValue(I.getOperand(1));
641 I.setOperand(1, NewRHSV);
650 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
651 return commonRemTransforms(I);