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))
303 ConstantFP *C0 = dyn_cast<ConstantFP>(I->getOperand(0));
304 ConstantFP *C1 = dyn_cast<ConstantFP>(I->getOperand(1));
309 return (C0 && C0->getValueAPF().isNormal()) ||
310 (C1 && C1->getValueAPF().isNormal());
313 static bool isNormalFp(const ConstantFP *C) {
314 const APFloat &Flt = C->getValueAPF();
315 return Flt.isNormal() && !Flt.isDenormal();
318 /// foldFMulConst() is a helper routine of InstCombiner::visitFMul().
319 /// The input \p FMulOrDiv is a FMul/FDiv with one and only one operand
320 /// being a constant (i.e. isFMulOrFDivWithConstant(FMulOrDiv) == true).
321 /// This function is to simplify "FMulOrDiv * C" and returns the
322 /// resulting expression. Note that this function could return NULL in
323 /// case the constants cannot be folded into a normal floating-point.
325 Value *InstCombiner::foldFMulConst(Instruction *FMulOrDiv, ConstantFP *C,
326 Instruction *InsertBefore) {
327 assert(isFMulOrFDivWithConstant(FMulOrDiv) && "V is invalid");
329 Value *Opnd0 = FMulOrDiv->getOperand(0);
330 Value *Opnd1 = FMulOrDiv->getOperand(1);
332 ConstantFP *C0 = dyn_cast<ConstantFP>(Opnd0);
333 ConstantFP *C1 = dyn_cast<ConstantFP>(Opnd1);
335 BinaryOperator *R = 0;
337 // (X * C0) * C => X * (C0*C)
338 if (FMulOrDiv->getOpcode() == Instruction::FMul) {
339 Constant *F = ConstantExpr::getFMul(C1 ? C1 : C0, C);
340 if (isNormalFp(cast<ConstantFP>(F)))
341 R = BinaryOperator::CreateFMul(C1 ? Opnd0 : Opnd1, F);
344 // (C0 / X) * C => (C0 * C) / X
345 ConstantFP *F = cast<ConstantFP>(ConstantExpr::getFMul(C0, C));
347 R = BinaryOperator::CreateFDiv(F, Opnd1);
349 // (X / C1) * C => X * (C/C1) if C/C1 is not a denormal
350 ConstantFP *F = cast<ConstantFP>(ConstantExpr::getFDiv(C, C1));
352 R = BinaryOperator::CreateFMul(Opnd0, F);
354 // (X / C1) * C => X / (C1/C)
355 Constant *F = ConstantExpr::getFDiv(C1, C);
356 if (isNormalFp(cast<ConstantFP>(F)))
357 R = BinaryOperator::CreateFDiv(Opnd0, F);
363 R->setHasUnsafeAlgebra(true);
364 InsertNewInstWith(R, *InsertBefore);
370 Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
371 bool Changed = SimplifyAssociativeOrCommutative(I);
372 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
374 if (isa<Constant>(Op0))
377 if (Value *V = SimplifyFMulInst(Op0, Op1, I.getFastMathFlags(), TD))
378 return ReplaceInstUsesWith(I, V);
380 bool AllowReassociate = I.hasUnsafeAlgebra();
382 // Simplify mul instructions with a constant RHS.
383 if (isa<Constant>(Op1)) {
384 // Try to fold constant mul into select arguments.
385 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
386 if (Instruction *R = FoldOpIntoSelect(I, SI))
389 if (isa<PHINode>(Op0))
390 if (Instruction *NV = FoldOpIntoPhi(I))
393 ConstantFP *C = dyn_cast<ConstantFP>(Op1);
394 if (C && AllowReassociate && C->getValueAPF().isNormal()) {
395 // Let MDC denote an expression in one of these forms:
396 // X * C, C/X, X/C, where C is a constant.
398 // Try to simplify "MDC * Constant"
399 if (isFMulOrFDivWithConstant(Op0)) {
400 Value *V = foldFMulConst(cast<Instruction>(Op0), C, &I);
402 return ReplaceInstUsesWith(I, V);
405 // (MDC +/- C1) * C => (MDC * C) +/- (C1 * C)
406 Instruction *FAddSub = dyn_cast<Instruction>(Op0);
408 (FAddSub->getOpcode() == Instruction::FAdd ||
409 FAddSub->getOpcode() == Instruction::FSub)) {
410 Value *Opnd0 = FAddSub->getOperand(0);
411 Value *Opnd1 = FAddSub->getOperand(1);
412 ConstantFP *C0 = dyn_cast<ConstantFP>(Opnd0);
413 ConstantFP *C1 = dyn_cast<ConstantFP>(Opnd1);
417 std::swap(Opnd0, Opnd1);
421 if (C1 && C1->getValueAPF().isNormal() &&
422 isFMulOrFDivWithConstant(Opnd0)) {
423 Value *M1 = ConstantExpr::getFMul(C1, C);
424 Value *M0 = isNormalFp(cast<ConstantFP>(M1)) ?
425 foldFMulConst(cast<Instruction>(Opnd0), C, &I) :
428 if (Swap && FAddSub->getOpcode() == Instruction::FSub)
431 Value *R = (FAddSub->getOpcode() == Instruction::FAdd) ?
432 BinaryOperator::CreateFAdd(M0, M1) :
433 BinaryOperator::CreateFSub(M0, M1);
434 Instruction *RI = cast<Instruction>(R);
435 RI->copyFastMathFlags(&I);
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 // Handle symmetric situation in a 2-iteration loop
474 for (int i = 0; i < 2; i++) {
475 bool IgnoreZeroSign = I.hasNoSignedZeros();
476 if (BinaryOperator::isFNeg(Opnd0, IgnoreZeroSign)) {
477 Value *N0 = dyn_castFNegVal(Opnd0, IgnoreZeroSign);
478 Value *N1 = dyn_castFNegVal(Opnd1, IgnoreZeroSign);
482 return BinaryOperator::CreateFMul(N0, N1);
484 if (Opnd0->hasOneUse()) {
485 // -X * Y => -(X*Y) (Promote negation as high as possible)
486 Value *T = Builder->CreateFMul(N0, Opnd1);
487 cast<Instruction>(T)->setDebugLoc(I.getDebugLoc());
488 Instruction *Neg = BinaryOperator::CreateFNeg(T);
489 if (I.getFastMathFlags().any()) {
490 cast<Instruction>(T)->copyFastMathFlags(&I);
491 Neg->copyFastMathFlags(&I);
497 // (X*Y) * X => (X*X) * Y where Y != X
498 // The purpose is two-fold:
499 // 1) to form a power expression (of X).
500 // 2) potentially shorten the critical path: After transformation, the
501 // latency of the instruction Y is amortized by the expression of X*X,
502 // and therefore Y is in a "less critical" position compared to what it
503 // was before the transformation.
505 if (AllowReassociate) {
506 Value *Opnd0_0, *Opnd0_1;
507 if (Opnd0->hasOneUse() &&
508 match(Opnd0, m_FMul(m_Value(Opnd0_0), m_Value(Opnd0_1)))) {
510 if (Opnd0_0 == Opnd1 && Opnd0_1 != Opnd1)
512 else if (Opnd0_1 == Opnd1 && Opnd0_0 != Opnd1)
516 Instruction *T = cast<Instruction>(Builder->CreateFMul(Opnd1, Opnd1));
517 T->copyFastMathFlags(&I);
518 T->setDebugLoc(I.getDebugLoc());
520 Instruction *R = BinaryOperator::CreateFMul(T, Y);
521 R->copyFastMathFlags(&I);
527 if (!isa<Constant>(Op1))
528 std::swap(Opnd0, Opnd1);
533 return Changed ? &I : 0;
536 /// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
538 bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
539 SelectInst *SI = cast<SelectInst>(I.getOperand(1));
541 // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
542 int NonNullOperand = -1;
543 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
544 if (ST->isNullValue())
546 // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
547 if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
548 if (ST->isNullValue())
551 if (NonNullOperand == -1)
554 Value *SelectCond = SI->getOperand(0);
556 // Change the div/rem to use 'Y' instead of the select.
557 I.setOperand(1, SI->getOperand(NonNullOperand));
559 // Okay, we know we replace the operand of the div/rem with 'Y' with no
560 // problem. However, the select, or the condition of the select may have
561 // multiple uses. Based on our knowledge that the operand must be non-zero,
562 // propagate the known value for the select into other uses of it, and
563 // propagate a known value of the condition into its other users.
565 // If the select and condition only have a single use, don't bother with this,
567 if (SI->use_empty() && SelectCond->hasOneUse())
570 // Scan the current block backward, looking for other uses of SI.
571 BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
573 while (BBI != BBFront) {
575 // If we found a call to a function, we can't assume it will return, so
576 // information from below it cannot be propagated above it.
577 if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
580 // Replace uses of the select or its condition with the known values.
581 for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
584 *I = SI->getOperand(NonNullOperand);
586 } else if (*I == SelectCond) {
587 *I = NonNullOperand == 1 ? ConstantInt::getTrue(BBI->getContext()) :
588 ConstantInt::getFalse(BBI->getContext());
593 // If we past the instruction, quit looking for it.
596 if (&*BBI == SelectCond)
599 // If we ran out of things to eliminate, break out of the loop.
600 if (SelectCond == 0 && SI == 0)
608 /// This function implements the transforms common to both integer division
609 /// instructions (udiv and sdiv). It is called by the visitors to those integer
610 /// division instructions.
611 /// @brief Common integer divide transforms
612 Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
613 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
615 // The RHS is known non-zero.
616 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) {
621 // Handle cases involving: [su]div X, (select Cond, Y, Z)
622 // This does not apply for fdiv.
623 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
626 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
627 // (X / C1) / C2 -> X / (C1*C2)
628 if (Instruction *LHS = dyn_cast<Instruction>(Op0))
629 if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode())
630 if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) {
631 if (MultiplyOverflows(RHS, LHSRHS,
632 I.getOpcode()==Instruction::SDiv))
633 return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
634 return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0),
635 ConstantExpr::getMul(RHS, LHSRHS));
638 if (!RHS->isZero()) { // avoid X udiv 0
639 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
640 if (Instruction *R = FoldOpIntoSelect(I, SI))
642 if (isa<PHINode>(Op0))
643 if (Instruction *NV = FoldOpIntoPhi(I))
648 // See if we can fold away this div instruction.
649 if (SimplifyDemandedInstructionBits(I))
652 // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
653 Value *X = 0, *Z = 0;
654 if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
655 bool isSigned = I.getOpcode() == Instruction::SDiv;
656 if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
657 (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
658 return BinaryOperator::Create(I.getOpcode(), X, Op1);
664 /// dyn_castZExtVal - Checks if V is a zext or constant that can
665 /// be truncated to Ty without losing bits.
666 static Value *dyn_castZExtVal(Value *V, Type *Ty) {
667 if (ZExtInst *Z = dyn_cast<ZExtInst>(V)) {
668 if (Z->getSrcTy() == Ty)
669 return Z->getOperand(0);
670 } else if (ConstantInt *C = dyn_cast<ConstantInt>(V)) {
671 if (C->getValue().getActiveBits() <= cast<IntegerType>(Ty)->getBitWidth())
672 return ConstantExpr::getTrunc(C, Ty);
677 Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
678 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
680 if (Value *V = SimplifyUDivInst(Op0, Op1, TD))
681 return ReplaceInstUsesWith(I, V);
683 // Handle the integer div common cases
684 if (Instruction *Common = commonIDivTransforms(I))
688 // X udiv 2^C -> X >> C
689 // Check to see if this is an unsigned division with an exact power of 2,
690 // if so, convert to a right shift.
692 if (match(Op1, m_Power2(C))) {
693 BinaryOperator *LShr =
694 BinaryOperator::CreateLShr(Op0,
695 ConstantInt::get(Op0->getType(),
697 if (I.isExact()) LShr->setIsExact();
702 if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
703 // X udiv C, where C >= signbit
704 if (C->getValue().isNegative()) {
705 Value *IC = Builder->CreateICmpULT(Op0, C);
706 return SelectInst::Create(IC, Constant::getNullValue(I.getType()),
707 ConstantInt::get(I.getType(), 1));
711 // (x lshr C1) udiv C2 --> x udiv (C2 << C1)
712 if (ConstantInt *C2 = dyn_cast<ConstantInt>(Op1)) {
715 if (match(Op0, m_LShr(m_Value(X), m_ConstantInt(C1)))) {
716 APInt NC = C2->getValue().shl(C1->getLimitedValue(C1->getBitWidth()-1));
717 return BinaryOperator::CreateUDiv(X, Builder->getInt(NC));
721 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
722 { const APInt *CI; Value *N;
723 if (match(Op1, m_Shl(m_Power2(CI), m_Value(N))) ||
724 match(Op1, m_ZExt(m_Shl(m_Power2(CI), m_Value(N))))) {
726 N = Builder->CreateAdd(N,
727 ConstantInt::get(N->getType(), CI->logBase2()));
728 if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
729 N = Builder->CreateZExt(N, Z->getDestTy());
731 return BinaryOperator::CreateExactLShr(Op0, N);
732 return BinaryOperator::CreateLShr(Op0, N);
736 // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2)
737 // where C1&C2 are powers of two.
738 { Value *Cond; const APInt *C1, *C2;
739 if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) {
740 // Construct the "on true" case of the select
741 Value *TSI = Builder->CreateLShr(Op0, C1->logBase2(), Op1->getName()+".t",
744 // Construct the "on false" case of the select
745 Value *FSI = Builder->CreateLShr(Op0, C2->logBase2(), Op1->getName()+".f",
748 // construct the select instruction and return it.
749 return SelectInst::Create(Cond, TSI, FSI);
753 // (zext A) udiv (zext B) --> zext (A udiv B)
754 if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
755 if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
756 return new ZExtInst(Builder->CreateUDiv(ZOp0->getOperand(0), ZOp1, "div",
763 Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
764 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
766 if (Value *V = SimplifySDivInst(Op0, Op1, TD))
767 return ReplaceInstUsesWith(I, V);
769 // Handle the integer div common cases
770 if (Instruction *Common = commonIDivTransforms(I))
773 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Op1)) {
775 if (RHS->isAllOnesValue())
776 return BinaryOperator::CreateNeg(Op0);
778 // sdiv X, C --> ashr exact X, log2(C)
779 if (I.isExact() && RHS->getValue().isNonNegative() &&
780 RHS->getValue().isPowerOf2()) {
781 Value *ShAmt = llvm::ConstantInt::get(RHS->getType(),
782 RHS->getValue().exactLogBase2());
783 return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName());
786 // -X/C --> X/-C provided the negation doesn't overflow.
787 if (SubOperator *Sub = dyn_cast<SubOperator>(Op0))
788 if (match(Sub->getOperand(0), m_Zero()) && Sub->hasNoSignedWrap())
789 return BinaryOperator::CreateSDiv(Sub->getOperand(1),
790 ConstantExpr::getNeg(RHS));
793 // If the sign bits of both operands are zero (i.e. we can prove they are
794 // unsigned inputs), turn this into a udiv.
795 if (I.getType()->isIntegerTy()) {
796 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
797 if (MaskedValueIsZero(Op0, Mask)) {
798 if (MaskedValueIsZero(Op1, Mask)) {
799 // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
800 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
803 if (match(Op1, m_Shl(m_Power2(), m_Value()))) {
804 // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
805 // Safe because the only negative value (1 << Y) can take on is
806 // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
808 return BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
816 /// CvtFDivConstToReciprocal tries to convert X/C into X*1/C if C not a special
818 /// 1) 1/C is exact, or
819 /// 2) reciprocal is allowed.
820 /// If the convertion was successful, the simplified expression "X * 1/C" is
821 /// returned; otherwise, NULL is returned.
823 static Instruction *CvtFDivConstToReciprocal(Value *Dividend,
825 bool AllowReciprocal) {
826 const APFloat &FpVal = Divisor->getValueAPF();
827 APFloat Reciprocal(FpVal.getSemantics());
828 bool Cvt = FpVal.getExactInverse(&Reciprocal);
830 if (!Cvt && AllowReciprocal && FpVal.isNormal()) {
831 Reciprocal = APFloat(FpVal.getSemantics(), 1.0f);
832 (void)Reciprocal.divide(FpVal, APFloat::rmNearestTiesToEven);
833 Cvt = !Reciprocal.isDenormal();
840 R = ConstantFP::get(Dividend->getType()->getContext(), Reciprocal);
841 return BinaryOperator::CreateFMul(Dividend, R);
844 Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
845 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
847 if (Value *V = SimplifyFDivInst(Op0, Op1, TD))
848 return ReplaceInstUsesWith(I, V);
850 bool AllowReassociate = I.hasUnsafeAlgebra();
851 bool AllowReciprocal = I.hasAllowReciprocal();
853 if (ConstantFP *Op1C = dyn_cast<ConstantFP>(Op1)) {
854 if (AllowReassociate) {
856 ConstantFP *C2 = Op1C;
858 Instruction *Res = 0;
860 if (match(Op0, m_FMul(m_Value(X), m_ConstantFP(C1)))) {
861 // (X*C1)/C2 => X * (C1/C2)
863 Constant *C = ConstantExpr::getFDiv(C1, C2);
864 const APFloat &F = cast<ConstantFP>(C)->getValueAPF();
865 if (F.isNormal() && !F.isDenormal())
866 Res = BinaryOperator::CreateFMul(X, C);
867 } else if (match(Op0, m_FDiv(m_Value(X), m_ConstantFP(C1)))) {
868 // (X/C1)/C2 => X /(C2*C1) [=> X * 1/(C2*C1) if reciprocal is allowed]
870 Constant *C = ConstantExpr::getFMul(C1, C2);
871 const APFloat &F = cast<ConstantFP>(C)->getValueAPF();
872 if (F.isNormal() && !F.isDenormal()) {
873 Res = CvtFDivConstToReciprocal(X, cast<ConstantFP>(C),
876 Res = BinaryOperator::CreateFDiv(X, C);
881 Res->setFastMathFlags(I.getFastMathFlags());
887 if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal))
893 if (AllowReassociate && isa<ConstantFP>(Op0)) {
894 ConstantFP *C1 = cast<ConstantFP>(Op0), *C2;
897 bool CreateDiv = true;
899 // C1 / (X*C2) => (C1/C2) / X
900 if (match(Op1, m_FMul(m_Value(X), m_ConstantFP(C2))))
901 Fold = ConstantExpr::getFDiv(C1, C2);
902 else if (match(Op1, m_FDiv(m_Value(X), m_ConstantFP(C2)))) {
903 // C1 / (X/C2) => (C1*C2) / X
904 Fold = ConstantExpr::getFMul(C1, C2);
905 } else if (match(Op1, m_FDiv(m_ConstantFP(C2), m_Value(X)))) {
906 // C1 / (C2/X) => (C1/C2) * X
907 Fold = ConstantExpr::getFDiv(C1, C2);
912 const APFloat &FoldC = cast<ConstantFP>(Fold)->getValueAPF();
913 if (FoldC.isNormal() && !FoldC.isDenormal()) {
914 Instruction *R = CreateDiv ?
915 BinaryOperator::CreateFDiv(Fold, X) :
916 BinaryOperator::CreateFMul(X, Fold);
917 R->setFastMathFlags(I.getFastMathFlags());
924 if (AllowReassociate) {
927 Instruction *SimpR = 0;
929 if (Op0->hasOneUse() && match(Op0, m_FDiv(m_Value(X), m_Value(Y)))) {
930 // (X/Y) / Z => X / (Y*Z)
932 if (!isa<ConstantFP>(Y) || !isa<ConstantFP>(Op1)) {
933 NewInst = Builder->CreateFMul(Y, Op1);
934 SimpR = BinaryOperator::CreateFDiv(X, NewInst);
936 } else if (Op1->hasOneUse() && match(Op1, m_FDiv(m_Value(X), m_Value(Y)))) {
937 // Z / (X/Y) => Z*Y / X
939 if (!isa<ConstantFP>(Y) || !isa<ConstantFP>(Op0)) {
940 NewInst = Builder->CreateFMul(Op0, Y);
941 SimpR = BinaryOperator::CreateFDiv(NewInst, X);
946 if (Instruction *T = dyn_cast<Instruction>(NewInst))
947 T->setDebugLoc(I.getDebugLoc());
948 SimpR->setFastMathFlags(I.getFastMathFlags());
956 /// This function implements the transforms common to both integer remainder
957 /// instructions (urem and srem). It is called by the visitors to those integer
958 /// remainder instructions.
959 /// @brief Common integer remainder transforms
960 Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
961 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
963 // The RHS is known non-zero.
964 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this)) {
969 // Handle cases involving: rem X, (select Cond, Y, Z)
970 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))
973 if (isa<ConstantInt>(Op1)) {
974 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
975 if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
976 if (Instruction *R = FoldOpIntoSelect(I, SI))
978 } else if (isa<PHINode>(Op0I)) {
979 if (Instruction *NV = FoldOpIntoPhi(I))
983 // See if we can fold away this rem instruction.
984 if (SimplifyDemandedInstructionBits(I))
992 Instruction *InstCombiner::visitURem(BinaryOperator &I) {
993 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
995 if (Value *V = SimplifyURemInst(Op0, Op1, TD))
996 return ReplaceInstUsesWith(I, V);
998 if (Instruction *common = commonIRemTransforms(I))
1001 // X urem C^2 -> X and C-1
1003 if (match(Op1, m_Power2(C)))
1004 return BinaryOperator::CreateAnd(Op0,
1005 ConstantInt::get(I.getType(), *C-1));
1008 // Turn A % (C << N), where C is 2^k, into A & ((C << N)-1)
1009 if (match(Op1, m_Shl(m_Power2(), m_Value()))) {
1010 Constant *N1 = Constant::getAllOnesValue(I.getType());
1011 Value *Add = Builder->CreateAdd(Op1, N1);
1012 return BinaryOperator::CreateAnd(Op0, Add);
1015 // urem X, (select Cond, 2^C1, 2^C2) -->
1016 // select Cond, (and X, C1-1), (and X, C2-1)
1017 // when C1&C2 are powers of two.
1018 { Value *Cond; const APInt *C1, *C2;
1019 if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) {
1020 Value *TrueAnd = Builder->CreateAnd(Op0, *C1-1, Op1->getName()+".t");
1021 Value *FalseAnd = Builder->CreateAnd(Op0, *C2-1, Op1->getName()+".f");
1022 return SelectInst::Create(Cond, TrueAnd, FalseAnd);
1026 // (zext A) urem (zext B) --> zext (A urem B)
1027 if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
1028 if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
1029 return new ZExtInst(Builder->CreateURem(ZOp0->getOperand(0), ZOp1),
1035 Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
1036 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1038 if (Value *V = SimplifySRemInst(Op0, Op1, TD))
1039 return ReplaceInstUsesWith(I, V);
1041 // Handle the integer rem common cases
1042 if (Instruction *Common = commonIRemTransforms(I))
1045 if (Value *RHSNeg = dyn_castNegVal(Op1))
1046 if (!isa<Constant>(RHSNeg) ||
1047 (isa<ConstantInt>(RHSNeg) &&
1048 cast<ConstantInt>(RHSNeg)->getValue().isStrictlyPositive())) {
1050 Worklist.AddValue(I.getOperand(1));
1051 I.setOperand(1, RHSNeg);
1055 // If the sign bits of both operands are zero (i.e. we can prove they are
1056 // unsigned inputs), turn this into a urem.
1057 if (I.getType()->isIntegerTy()) {
1058 APInt Mask(APInt::getSignBit(I.getType()->getPrimitiveSizeInBits()));
1059 if (MaskedValueIsZero(Op1, Mask) && MaskedValueIsZero(Op0, Mask)) {
1060 // X srem Y -> X urem Y, iff X and Y don't have sign bit set
1061 return BinaryOperator::CreateURem(Op0, Op1, I.getName());
1065 // If it's a constant vector, flip any negative values positive.
1066 if (isa<ConstantVector>(Op1) || isa<ConstantDataVector>(Op1)) {
1067 Constant *C = cast<Constant>(Op1);
1068 unsigned VWidth = C->getType()->getVectorNumElements();
1070 bool hasNegative = false;
1071 bool hasMissing = false;
1072 for (unsigned i = 0; i != VWidth; ++i) {
1073 Constant *Elt = C->getAggregateElement(i);
1079 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elt))
1080 if (RHS->isNegative())
1084 if (hasNegative && !hasMissing) {
1085 SmallVector<Constant *, 16> Elts(VWidth);
1086 for (unsigned i = 0; i != VWidth; ++i) {
1087 Elts[i] = C->getAggregateElement(i); // Handle undef, etc.
1088 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elts[i])) {
1089 if (RHS->isNegative())
1090 Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
1094 Constant *NewRHSV = ConstantVector::get(Elts);
1095 if (NewRHSV != C) { // Don't loop on -MININT
1096 Worklist.AddValue(I.getOperand(1));
1097 I.setOperand(1, NewRHSV);
1106 Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
1107 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1109 if (Value *V = SimplifyFRemInst(Op0, Op1, TD))
1110 return ReplaceInstUsesWith(I, V);
1112 // Handle cases involving: rem X, (select Cond, Y, Z)
1113 if (isa<SelectInst>(Op1) && SimplifyDivRemOfSelect(I))