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/Support/PatternMatch.h"
19 using namespace PatternMatch;
21 /// SubOne - Subtract one from a ConstantInt.
22 static Constant *SubOne(ConstantInt *C) {
23 return ConstantInt::get(C->getContext(), C->getValue()-1);
26 /// MultiplyOverflows - True if the multiply can not be expressed in an int
28 static bool MultiplyOverflows(ConstantInt *C1, ConstantInt *C2, bool sign) {
29 uint32_t W = C1->getBitWidth();
30 APInt LHSExt = C1->getValue(), RHSExt = C2->getValue();
32 LHSExt = LHSExt.sext(W * 2);
33 RHSExt = RHSExt.sext(W * 2);
35 LHSExt = LHSExt.zext(W * 2);
36 RHSExt = RHSExt.zext(W * 2);
39 APInt MulExt = LHSExt * RHSExt;
42 return MulExt.ugt(APInt::getLowBitsSet(W * 2, W));
44 APInt Min = APInt::getSignedMinValue(W).sext(W * 2);
45 APInt Max = APInt::getSignedMaxValue(W).sext(W * 2);
46 return MulExt.slt(Min) || MulExt.sgt(Max);
49 Instruction *InstCombiner::visitMul(BinaryOperator &I) {
50 bool Changed = SimplifyAssociativeOrCommutative(I);
51 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
53 if (isa<UndefValue>(Op1)) // undef * X -> 0
54 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
56 // Simplify mul instructions with a constant RHS.
57 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
58 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1C)) {
60 // ((X << C1)*C2) == (X * (C2 << C1))
61 if (BinaryOperator *SI = dyn_cast<BinaryOperator>(Op0))
62 if (SI->getOpcode() == Instruction::Shl)
63 if (Constant *ShOp = dyn_cast<Constant>(SI->getOperand(1)))
64 return BinaryOperator::CreateMul(SI->getOperand(0),
65 ConstantExpr::getShl(CI, ShOp));
68 return ReplaceInstUsesWith(I, Op1C); // X * 0 == 0
69 if (CI->equalsInt(1)) // X * 1 == X
70 return ReplaceInstUsesWith(I, Op0);
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 on div instructions that work
308 /// regardless of the kind of div instruction it is (udiv, sdiv, or fdiv). It is
309 /// used by the visitors to those instructions.
310 /// @brief Transforms common to all three div instructions
311 Instruction *InstCombiner::commonDivTransforms(BinaryOperator &I) {
312 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
314 // undef / X -> 0 for integer.
315 // undef / X -> undef for FP (the undef could be a snan).
316 if (isa<UndefValue>(Op0)) {
317 if (Op0->getType()->isFPOrFPVectorTy())
318 return ReplaceInstUsesWith(I, Op0);
319 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
322 // X / undef -> undef
323 if (isa<UndefValue>(Op1))
324 return ReplaceInstUsesWith(I, Op1);
329 /// This function implements the transforms common to both integer division
330 /// instructions (udiv and sdiv). It is called by the visitors to those integer
331 /// division instructions.
332 /// @brief Common integer divide transforms
333 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
334 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
336 // (sdiv X, X) --> 1 (udiv X, X) --> 1
338 if (const VectorType *Ty = dyn_cast<VectorType>(I.getType())) {
339 Constant *CI = ConstantInt::get(Ty->getElementType(), 1);
340 std::vector<Constant*> Elts(Ty->getNumElements(), CI);
341 return ReplaceInstUsesWith(I, ConstantVector::get(Elts));
344 Constant *CI = ConstantInt::get(I.getType(), 1);
345 return ReplaceInstUsesWith(I, CI);
348 if (Instruction *Common = commonDivTransforms(I))
351 // Handle cases involving: [su]div X, (select Cond, Y, Z)
352 // This does not apply for fdiv.
353 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
356 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
358 if (RHS->equalsInt(1))
359 return ReplaceInstUsesWith(I, Op0);
361 // (X / C1) / C2 -> X / (C1*C2)
362 if (Instruction *LHS = dyn_cast<Instruction>(Op0))
363 if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode())
364 if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
365 if (MultiplyOverflows(RHS, LHSRHS,
366 I.getOpcode()==Instruction::SDiv))
367 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
369 return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0),
370 ConstantExpr::getMul(RHS, LHSRHS));
373 if (!RHS->isZero()) { // avoid X udiv 0
374 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
375 if (Instruction *R = FoldOpIntoSelect(I, SI))
377 if (isa<PHINode>(Op0))
378 if (Instruction *NV = FoldOpIntoPhi(I))
383 // 0 / X == 0, we don't need to preserve faults!
384 if (ConstantInt *LHS = dyn_cast<ConstantInt>(Op0))
385 if (LHS->equalsInt(0))
386 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
388 // It can't be division by zero, hence it must be division by one.
389 if (I.getType()->isIntegerTy(1))
390 return ReplaceInstUsesWith(I, Op0);
392 if (ConstantVector *Op1V = dyn_cast<ConstantVector>(Op1)) {
393 if (ConstantInt *X = cast_or_null<ConstantInt>(Op1V->getSplatValue()))
396 return ReplaceInstUsesWith(I, Op0);
402 Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
403 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
405 // Handle the integer div common cases
406 if (Instruction *Common = commonIDivTransforms(I))
409 if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
410 // X udiv 2^C -> X >> C
411 // Check to see if this is an unsigned division with an exact power of 2,
412 // if so, convert to a right shift.
413 if (C->getValue().isPowerOf2()) // 0 not included in isPowerOf2
414 return BinaryOperator::CreateLShr(Op0,
415 ConstantInt::get(Op0->getType(), C->getValue().logBase2()));
417 // X udiv C, where C >= signbit
418 if (C->getValue().isNegative()) {
419 Value *IC = Builder->CreateICmpULT( Op0, C);
420 return SelectInst::Create(IC, Constant::getNullValue(I.getType()),
421 ConstantInt::get(I.getType(), 1));
425 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
426 if (BinaryOperator *RHSI = dyn_cast<BinaryOperator>(I.getOperand(1))) {
427 if (RHSI->getOpcode() == Instruction::Shl &&
428 isa<ConstantInt>(RHSI->getOperand(0))) {
429 const APInt& C1 = cast<ConstantInt>(RHSI->getOperand(0))->getValue();
430 if (C1.isPowerOf2()) {
431 Value *N = RHSI->getOperand(1);
432 const Type *NTy = N->getType();
433 if (uint32_t C2 = C1.logBase2())
434 N = Builder->CreateAdd(N, ConstantInt::get(NTy, C2), "tmp");
435 return BinaryOperator::CreateLShr(Op0, N);
440 // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2)
441 // where C1&C2 are powers of two.
442 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
443 if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
444 if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
445 const APInt &TVA = STO->getValue(), &FVA = SFO->getValue();
446 if (TVA.isPowerOf2() && FVA.isPowerOf2()) {
447 // Compute the shift amounts
448 uint32_t TSA = TVA.logBase2(), FSA = FVA.logBase2();
449 // Construct the "on true" case of the select
450 Constant *TC = ConstantInt::get(Op0->getType(), TSA);
451 Value *TSI = Builder->CreateLShr(Op0, TC, SI->getName()+".t");
453 // Construct the "on false" case of the select
454 Constant *FC = ConstantInt::get(Op0->getType(), FSA);
455 Value *FSI = Builder->CreateLShr(Op0, FC, SI->getName()+".f");
457 // construct the select instruction and return it.
458 return SelectInst::Create(SI->getOperand(0), TSI, FSI, SI->getName());
464 Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
465 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
467 // Handle the integer div common cases
468 if (Instruction *Common = commonIDivTransforms(I))
471 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
473 if (RHS->isAllOnesValue())
474 return BinaryOperator::CreateNeg(Op0);
476 // sdiv X, C --> ashr X, log2(C)
477 if (cast<SDivOperator>(&I)->isExact() &&
478 RHS->getValue().isNonNegative() &&
479 RHS->getValue().isPowerOf2()) {
480 Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
481 RHS->getValue().exactLogBase2());
482 return BinaryOperator::CreateAShr(Op0, ShAmt, I.getName());
485 // -X/C --> X/-C provided the negation doesn't overflow.
486 if (SubOperator *Sub = dyn_cast<SubOperator>(Op0))
487 if (isa<Constant>(Sub->getOperand(0)) &&
488 cast<Constant>(Sub->getOperand(0))->isNullValue() &&
489 Sub->hasNoSignedWrap())
490 return BinaryOperator::CreateSDiv(Sub->getOperand(1),
491 ConstantExpr::getNeg(RHS));
494 // If the sign bits of both operands are zero (i.e. we can prove they are
495 // unsigned inputs), turn this into a udiv.
496 if (I.getType()->isIntegerTy()) {
497 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
498 if (MaskedValueIsZero(Op0, Mask)) {
499 if (MaskedValueIsZero(Op1, Mask)) {
500 // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
501 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
503 ConstantInt *ShiftedInt;
504 if (match(Op1, m_Shl(m_ConstantInt(ShiftedInt), m_Value())) &&
505 ShiftedInt->getValue().isPowerOf2()) {
506 // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
507 // Safe because the only negative value (1 << Y) can take on is
508 // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
510 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
518 Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
519 return commonDivTransforms(I);
522 /// This function implements the transforms on rem instructions that work
523 /// regardless of the kind of rem instruction it is (urem, srem, or frem). It
524 /// is used by the visitors to those instructions.
525 /// @brief Transforms common to all three rem instructions
526 Instruction *InstCombiner::commonRemTransforms(BinaryOperator &I) {
527 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
529 if (isa<UndefValue>(Op0)) { // undef % X -> 0
530 if (I.getType()->isFPOrFPVectorTy())
531 return ReplaceInstUsesWith(I, Op0); // X % undef -> undef (could be SNaN)
532 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
534 if (isa<UndefValue>(Op1))
535 return ReplaceInstUsesWith(I, Op1); // X % undef -> undef
537 // Handle cases involving: rem X, (select Cond, Y, Z)
538 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
544 /// This function implements the transforms common to both integer remainder
545 /// instructions (urem and srem). It is called by the visitors to those integer
546 /// remainder instructions.
547 /// @brief Common integer remainder transforms
548 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
549 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
551 if (Instruction *common = commonRemTransforms(I))
556 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
558 // 0 % X == 0 for integer, we don't need to preserve faults!
559 if (Constant *LHS = dyn_cast<Constant>(Op0))
560 if (LHS->isNullValue())
561 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
563 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
564 // X % 0 == undef, we don't need to preserve faults!
565 if (RHS->equalsInt(0))
566 return ReplaceInstUsesWith(I, UndefValue::get(I.getType()));
568 if (RHS->equalsInt(1)) // X % 1 == 0
569 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
571 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
572 if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
573 if (Instruction *R = FoldOpIntoSelect(I, SI))
575 } else if (isa<PHINode>(Op0I)) {
576 if (Instruction *NV = FoldOpIntoPhi(I))
580 // See if we can fold away this rem instruction.
581 if (SimplifyDemandedInstructionBits(I))
589 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
590 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
592 if (Instruction *common = commonIRemTransforms(I))
595 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
596 // X urem C^2 -> X and C
597 // Check to see if this is an unsigned remainder with an exact power of 2,
598 // if so, convert to a bitwise and.
599 if (ConstantInt *C = dyn_cast<ConstantInt>(RHS))
600 if (C->getValue().isPowerOf2())
601 return BinaryOperator::CreateAnd(Op0, SubOne(C));
604 if (Instruction *RHSI = dyn_cast<Instruction>(I.getOperand(1))) {
605 // Turn A % (C << N), where C is 2^k, into A & ((C << N)-1)
606 if (RHSI->getOpcode() == Instruction::Shl &&
607 isa<ConstantInt>(RHSI->getOperand(0))) {
608 if (cast<ConstantInt>(RHSI->getOperand(0))->getValue().isPowerOf2()) {
609 Constant *N1 = Constant::getAllOnesValue(I.getType());
610 Value *Add = Builder->CreateAdd(RHSI, N1, "tmp");
611 return BinaryOperator::CreateAnd(Op0, Add);
616 // urem X, (select Cond, 2^C1, 2^C2) --> select Cond, (and X, C1), (and X, C2)
617 // where C1&C2 are powers of two.
618 if (SelectInst *SI = dyn_cast<SelectInst>(Op1)) {
619 if (ConstantInt *STO = dyn_cast<ConstantInt>(SI->getOperand(1)))
620 if (ConstantInt *SFO = dyn_cast<ConstantInt>(SI->getOperand(2))) {
621 // STO == 0 and SFO == 0 handled above.
622 if ((STO->getValue().isPowerOf2()) &&
623 (SFO->getValue().isPowerOf2())) {
624 Value *TrueAnd = Builder->CreateAnd(Op0, SubOne(STO),
626 Value *FalseAnd = Builder->CreateAnd(Op0, SubOne(SFO),
628 return SelectInst::Create(SI->getOperand(0), TrueAnd, FalseAnd);
636 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
637 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
639 // Handle the integer rem common cases
640 if (Instruction *Common = commonIRemTransforms(I))
643 if (Value *RHSNeg = dyn_castNegVal(Op1))
644 if (!isa<Constant>(RHSNeg) ||
645 (isa<ConstantInt>(RHSNeg) &&
646 cast<ConstantInt>(RHSNeg)->getValue().isStrictlyPositive())) {
648 Worklist.AddValue(I.getOperand(1));
649 I.setOperand(1, RHSNeg);
653 // If the sign bits of both operands are zero (i.e. we can prove they are
654 // unsigned inputs), turn this into a urem.
655 if (I.getType()->isIntegerTy()) {
656 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
657 if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
658 // X srem Y -> X urem Y, iff X and Y don't have sign bit set
659 return BinaryOperator::CreateURem(Op0, Op1, I.getName());
663 // If it's a constant vector, flip any negative values positive.
664 if (ConstantVector *RHSV = dyn_cast<ConstantVector>(Op1)) {
665 unsigned VWidth = RHSV->getNumOperands();
667 bool hasNegative = false;
668 for (unsigned i = 0; !hasNegative && i != VWidth; ++i)
669 if (ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV->getOperand(i)))
670 if (RHS->getValue().isNegative())
674 std::vector<Constant *> Elts(VWidth);
675 for (unsigned i = 0; i != VWidth; ++i) {
676 if (ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV->getOperand(i))) {
677 if (RHS->getValue().isNegative())
678 Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
684 Constant *NewRHSV = ConstantVector::get(Elts);
685 if (NewRHSV != RHSV) {
686 Worklist.AddValue(I.getOperand(1));
687 I.setOperand(1, NewRHSV);
696 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
697 return commonRemTransforms(I);