Bug Summary

File:lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
Warning:line 847, column 14
Called C++ object pointer is null

Annotated Source Code

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1//===- InstCombineMulDivRem.cpp -------------------------------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the visit functions for mul, fmul, sdiv, udiv, fdiv,
11// srem, urem, frem.
12//
13//===----------------------------------------------------------------------===//
14
15#include "InstCombineInternal.h"
16#include "llvm/ADT/APFloat.h"
17#include "llvm/ADT/APInt.h"
18#include "llvm/ADT/SmallVector.h"
19#include "llvm/Analysis/InstructionSimplify.h"
20#include "llvm/IR/BasicBlock.h"
21#include "llvm/IR/Constant.h"
22#include "llvm/IR/Constants.h"
23#include "llvm/IR/InstrTypes.h"
24#include "llvm/IR/Instruction.h"
25#include "llvm/IR/Instructions.h"
26#include "llvm/IR/IntrinsicInst.h"
27#include "llvm/IR/Intrinsics.h"
28#include "llvm/IR/Operator.h"
29#include "llvm/IR/PatternMatch.h"
30#include "llvm/IR/Type.h"
31#include "llvm/IR/Value.h"
32#include "llvm/Support/Casting.h"
33#include "llvm/Support/ErrorHandling.h"
34#include "llvm/Support/KnownBits.h"
35#include "llvm/Transforms/InstCombine/InstCombineWorklist.h"
36#include <cassert>
37#include <cstddef>
38#include <cstdint>
39#include <utility>
40
41using namespace llvm;
42using namespace PatternMatch;
43
44#define DEBUG_TYPE"instcombine" "instcombine"
45
46/// The specific integer value is used in a context where it is known to be
47/// non-zero. If this allows us to simplify the computation, do so and return
48/// the new operand, otherwise return null.
49static Value *simplifyValueKnownNonZero(Value *V, InstCombiner &IC,
50 Instruction &CxtI) {
51 // If V has multiple uses, then we would have to do more analysis to determine
52 // if this is safe. For example, the use could be in dynamically unreached
53 // code.
54 if (!V->hasOneUse()) return nullptr;
55
56 bool MadeChange = false;
57
58 // ((1 << A) >>u B) --> (1 << (A-B))
59 // Because V cannot be zero, we know that B is less than A.
60 Value *A = nullptr, *B = nullptr, *One = nullptr;
61 if (match(V, m_LShr(m_OneUse(m_Shl(m_Value(One), m_Value(A))), m_Value(B))) &&
62 match(One, m_One())) {
63 A = IC.Builder.CreateSub(A, B);
64 return IC.Builder.CreateShl(One, A);
65 }
66
67 // (PowerOfTwo >>u B) --> isExact since shifting out the result would make it
68 // inexact. Similarly for <<.
69 BinaryOperator *I = dyn_cast<BinaryOperator>(V);
70 if (I && I->isLogicalShift() &&
71 IC.isKnownToBeAPowerOfTwo(I->getOperand(0), false, 0, &CxtI)) {
72 // We know that this is an exact/nuw shift and that the input is a
73 // non-zero context as well.
74 if (Value *V2 = simplifyValueKnownNonZero(I->getOperand(0), IC, CxtI)) {
75 I->setOperand(0, V2);
76 MadeChange = true;
77 }
78
79 if (I->getOpcode() == Instruction::LShr && !I->isExact()) {
80 I->setIsExact();
81 MadeChange = true;
82 }
83
84 if (I->getOpcode() == Instruction::Shl && !I->hasNoUnsignedWrap()) {
85 I->setHasNoUnsignedWrap();
86 MadeChange = true;
87 }
88 }
89
90 // TODO: Lots more we could do here:
91 // If V is a phi node, we can call this on each of its operands.
92 // "select cond, X, 0" can simplify to "X".
93
94 return MadeChange ? V : nullptr;
95}
96
97/// True if the multiply can not be expressed in an int this size.
98static bool MultiplyOverflows(const APInt &C1, const APInt &C2, APInt &Product,
99 bool IsSigned) {
100 bool Overflow;
101 if (IsSigned)
102 Product = C1.smul_ov(C2, Overflow);
103 else
104 Product = C1.umul_ov(C2, Overflow);
105
106 return Overflow;
107}
108
109/// \brief True if C2 is a multiple of C1. Quotient contains C2/C1.
110static bool IsMultiple(const APInt &C1, const APInt &C2, APInt &Quotient,
111 bool IsSigned) {
112 assert(C1.getBitWidth() == C2.getBitWidth() &&(static_cast <bool> (C1.getBitWidth() == C2.getBitWidth
() && "Inconsistent width of constants!") ? void (0) :
__assert_fail ("C1.getBitWidth() == C2.getBitWidth() && \"Inconsistent width of constants!\""
, "/build/llvm-toolchain-snapshot-6.0~svn321459/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp"
, 113, __extension__ __PRETTY_FUNCTION__))
113 "Inconsistent width of constants!")(static_cast <bool> (C1.getBitWidth() == C2.getBitWidth
() && "Inconsistent width of constants!") ? void (0) :
__assert_fail ("C1.getBitWidth() == C2.getBitWidth() && \"Inconsistent width of constants!\""
, "/build/llvm-toolchain-snapshot-6.0~svn321459/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp"
, 113, __extension__ __PRETTY_FUNCTION__));
114
115 // Bail if we will divide by zero.
116 if (C2.isMinValue())
117 return false;
118
119 // Bail if we would divide INT_MIN by -1.
120 if (IsSigned && C1.isMinSignedValue() && C2.isAllOnesValue())
121 return false;
122
123 APInt Remainder(C1.getBitWidth(), /*Val=*/0ULL, IsSigned);
124 if (IsSigned)
125 APInt::sdivrem(C1, C2, Quotient, Remainder);
126 else
127 APInt::udivrem(C1, C2, Quotient, Remainder);
128
129 return Remainder.isMinValue();
130}
131
132/// \brief A helper routine of InstCombiner::visitMul().
133///
134/// If C is a vector of known powers of 2, then this function returns
135/// a new vector obtained from C replacing each element with its logBase2.
136/// Return a null pointer otherwise.
137static Constant *getLogBase2Vector(ConstantDataVector *CV) {
138 const APInt *IVal;
139 SmallVector<Constant *, 4> Elts;
140
141 for (unsigned I = 0, E = CV->getNumElements(); I != E; ++I) {
142 Constant *Elt = CV->getElementAsConstant(I);
143 if (!match(Elt, m_APInt(IVal)) || !IVal->isPowerOf2())
144 return nullptr;
145 Elts.push_back(ConstantInt::get(Elt->getType(), IVal->logBase2()));
146 }
147
148 return ConstantVector::get(Elts);
149}
150
151/// \brief Return true if we can prove that:
152/// (mul LHS, RHS) === (mul nsw LHS, RHS)
153bool InstCombiner::willNotOverflowSignedMul(const Value *LHS,
154 const Value *RHS,
155 const Instruction &CxtI) const {
156 // Multiplying n * m significant bits yields a result of n + m significant
157 // bits. If the total number of significant bits does not exceed the
158 // result bit width (minus 1), there is no overflow.
159 // This means if we have enough leading sign bits in the operands
160 // we can guarantee that the result does not overflow.
161 // Ref: "Hacker's Delight" by Henry Warren
162 unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
163
164 // Note that underestimating the number of sign bits gives a more
165 // conservative answer.
166 unsigned SignBits =
167 ComputeNumSignBits(LHS, 0, &CxtI) + ComputeNumSignBits(RHS, 0, &CxtI);
168
169 // First handle the easy case: if we have enough sign bits there's
170 // definitely no overflow.
171 if (SignBits > BitWidth + 1)
172 return true;
173
174 // There are two ambiguous cases where there can be no overflow:
175 // SignBits == BitWidth + 1 and
176 // SignBits == BitWidth
177 // The second case is difficult to check, therefore we only handle the
178 // first case.
179 if (SignBits == BitWidth + 1) {
180 // It overflows only when both arguments are negative and the true
181 // product is exactly the minimum negative number.
182 // E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
183 // For simplicity we just check if at least one side is not negative.
184 KnownBits LHSKnown = computeKnownBits(LHS, /*Depth=*/0, &CxtI);
185 KnownBits RHSKnown = computeKnownBits(RHS, /*Depth=*/0, &CxtI);
186 if (LHSKnown.isNonNegative() || RHSKnown.isNonNegative())
187 return true;
188 }
189 return false;
190}
191
192Instruction *InstCombiner::visitMul(BinaryOperator &I) {
193 bool Changed = SimplifyAssociativeOrCommutative(I);
194 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
195
196 if (Value *V = SimplifyVectorOp(I))
197 return replaceInstUsesWith(I, V);
198
199 if (Value *V = SimplifyMulInst(Op0, Op1, SQ.getWithInstruction(&I)))
200 return replaceInstUsesWith(I, V);
201
202 if (Value *V = SimplifyUsingDistributiveLaws(I))
203 return replaceInstUsesWith(I, V);
204
205 // X * -1 == 0 - X
206 if (match(Op1, m_AllOnes())) {
207 BinaryOperator *BO = BinaryOperator::CreateNeg(Op0, I.getName());
208 if (I.hasNoSignedWrap())
209 BO->setHasNoSignedWrap();
210 return BO;
211 }
212
213 // Also allow combining multiply instructions on vectors.
214 {
215 Value *NewOp;
216 Constant *C1, *C2;
217 const APInt *IVal;
218 if (match(&I, m_Mul(m_Shl(m_Value(NewOp), m_Constant(C2)),
219 m_Constant(C1))) &&
220 match(C1, m_APInt(IVal))) {
221 // ((X << C2)*C1) == (X * (C1 << C2))
222 Constant *Shl = ConstantExpr::getShl(C1, C2);
223 BinaryOperator *Mul = cast<BinaryOperator>(I.getOperand(0));
224 BinaryOperator *BO = BinaryOperator::CreateMul(NewOp, Shl);
225 if (I.hasNoUnsignedWrap() && Mul->hasNoUnsignedWrap())
226 BO->setHasNoUnsignedWrap();
227 if (I.hasNoSignedWrap() && Mul->hasNoSignedWrap() &&
228 Shl->isNotMinSignedValue())
229 BO->setHasNoSignedWrap();
230 return BO;
231 }
232
233 if (match(&I, m_Mul(m_Value(NewOp), m_Constant(C1)))) {
234 Constant *NewCst = nullptr;
235 if (match(C1, m_APInt(IVal)) && IVal->isPowerOf2())
236 // Replace X*(2^C) with X << C, where C is either a scalar or a splat.
237 NewCst = ConstantInt::get(NewOp->getType(), IVal->logBase2());
238 else if (ConstantDataVector *CV = dyn_cast<ConstantDataVector>(C1))
239 // Replace X*(2^C) with X << C, where C is a vector of known
240 // constant powers of 2.
241 NewCst = getLogBase2Vector(CV);
242
243 if (NewCst) {
244 unsigned Width = NewCst->getType()->getPrimitiveSizeInBits();
245 BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
246
247 if (I.hasNoUnsignedWrap())
248 Shl->setHasNoUnsignedWrap();
249 if (I.hasNoSignedWrap()) {
250 const APInt *V;
251 if (match(NewCst, m_APInt(V)) && *V != Width - 1)
252 Shl->setHasNoSignedWrap();
253 }
254
255 return Shl;
256 }
257 }
258 }
259
260 if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
261 // (Y - X) * (-(2**n)) -> (X - Y) * (2**n), for positive nonzero n
262 // (Y + const) * (-(2**n)) -> (-constY) * (2**n), for positive nonzero n
263 // The "* (2**n)" thus becomes a potential shifting opportunity.
264 {
265 const APInt & Val = CI->getValue();
266 const APInt &PosVal = Val.abs();
267 if (Val.isNegative() && PosVal.isPowerOf2()) {
268 Value *X = nullptr, *Y = nullptr;
269 if (Op0->hasOneUse()) {
270 ConstantInt *C1;
271 Value *Sub = nullptr;
272 if (match(Op0, m_Sub(m_Value(Y), m_Value(X))))
273 Sub = Builder.CreateSub(X, Y, "suba");
274 else if (match(Op0, m_Add(m_Value(Y), m_ConstantInt(C1))))
275 Sub = Builder.CreateSub(Builder.CreateNeg(C1), Y, "subc");
276 if (Sub)
277 return
278 BinaryOperator::CreateMul(Sub,
279 ConstantInt::get(Y->getType(), PosVal));
280 }
281 }
282 }
283 }
284
285 // Simplify mul instructions with a constant RHS.
286 if (isa<Constant>(Op1)) {
287 if (Instruction *FoldedMul = foldOpWithConstantIntoOperand(I))
288 return FoldedMul;
289
290 // Canonicalize (X+C1)*CI -> X*CI+C1*CI.
291 {
292 Value *X;
293 Constant *C1;
294 if (match(Op0, m_OneUse(m_Add(m_Value(X), m_Constant(C1))))) {
295 Value *Mul = Builder.CreateMul(C1, Op1);
296 // Only go forward with the transform if C1*CI simplifies to a tidier
297 // constant.
298 if (!match(Mul, m_Mul(m_Value(), m_Value())))
299 return BinaryOperator::CreateAdd(Builder.CreateMul(X, Op1), Mul);
300 }
301 }
302 }
303
304 if (Value *Op0v = dyn_castNegVal(Op0)) { // -X * -Y = X*Y
305 if (Value *Op1v = dyn_castNegVal(Op1)) {
306 BinaryOperator *BO = BinaryOperator::CreateMul(Op0v, Op1v);
307 if (I.hasNoSignedWrap() &&
308 match(Op0, m_NSWSub(m_Value(), m_Value())) &&
309 match(Op1, m_NSWSub(m_Value(), m_Value())))
310 BO->setHasNoSignedWrap();
311 return BO;
312 }
313 }
314
315 // (X / Y) * Y = X - (X % Y)
316 // (X / Y) * -Y = (X % Y) - X
317 {
318 Value *Y = Op1;
319 BinaryOperator *Div = dyn_cast<BinaryOperator>(Op0);
320 if (!Div || (Div->getOpcode() != Instruction::UDiv &&
321 Div->getOpcode() != Instruction::SDiv)) {
322 Y = Op0;
323 Div = dyn_cast<BinaryOperator>(Op1);
324 }
325 Value *Neg = dyn_castNegVal(Y);
326 if (Div && Div->hasOneUse() &&
327 (Div->getOperand(1) == Y || Div->getOperand(1) == Neg) &&
328 (Div->getOpcode() == Instruction::UDiv ||
329 Div->getOpcode() == Instruction::SDiv)) {
330 Value *X = Div->getOperand(0), *DivOp1 = Div->getOperand(1);
331
332 // If the division is exact, X % Y is zero, so we end up with X or -X.
333 if (Div->isExact()) {
334 if (DivOp1 == Y)
335 return replaceInstUsesWith(I, X);
336 return BinaryOperator::CreateNeg(X);
337 }
338
339 auto RemOpc = Div->getOpcode() == Instruction::UDiv ? Instruction::URem
340 : Instruction::SRem;
341 Value *Rem = Builder.CreateBinOp(RemOpc, X, DivOp1);
342 if (DivOp1 == Y)
343 return BinaryOperator::CreateSub(X, Rem);
344 return BinaryOperator::CreateSub(Rem, X);
345 }
346 }
347
348 /// i1 mul -> i1 and.
349 if (I.getType()->isIntOrIntVectorTy(1))
350 return BinaryOperator::CreateAnd(Op0, Op1);
351
352 // X*(1 << Y) --> X << Y
353 // (1 << Y)*X --> X << Y
354 {
355 Value *Y;
356 BinaryOperator *BO = nullptr;
357 bool ShlNSW = false;
358 if (match(Op0, m_Shl(m_One(), m_Value(Y)))) {
359 BO = BinaryOperator::CreateShl(Op1, Y);
360 ShlNSW = cast<ShlOperator>(Op0)->hasNoSignedWrap();
361 } else if (match(Op1, m_Shl(m_One(), m_Value(Y)))) {
362 BO = BinaryOperator::CreateShl(Op0, Y);
363 ShlNSW = cast<ShlOperator>(Op1)->hasNoSignedWrap();
364 }
365 if (BO) {
366 if (I.hasNoUnsignedWrap())
367 BO->setHasNoUnsignedWrap();
368 if (I.hasNoSignedWrap() && ShlNSW)
369 BO->setHasNoSignedWrap();
370 return BO;
371 }
372 }
373
374 // If one of the operands of the multiply is a cast from a boolean value, then
375 // we know the bool is either zero or one, so this is a 'masking' multiply.
376 // X * Y (where Y is 0 or 1) -> X & (0-Y)
377 if (!I.getType()->isVectorTy()) {
378 // -2 is "-1 << 1" so it is all bits set except the low one.
379 APInt Negative2(I.getType()->getPrimitiveSizeInBits(), (uint64_t)-2, true);
380
381 Value *BoolCast = nullptr, *OtherOp = nullptr;
382 if (MaskedValueIsZero(Op0, Negative2, 0, &I)) {
383 BoolCast = Op0;
384 OtherOp = Op1;
385 } else if (MaskedValueIsZero(Op1, Negative2, 0, &I)) {
386 BoolCast = Op1;
387 OtherOp = Op0;
388 }
389
390 if (BoolCast) {
391 Value *V = Builder.CreateSub(Constant::getNullValue(I.getType()),
392 BoolCast);
393 return BinaryOperator::CreateAnd(V, OtherOp);
394 }
395 }
396
397 // Check for (mul (sext x), y), see if we can merge this into an
398 // integer mul followed by a sext.
399 if (SExtInst *Op0Conv = dyn_cast<SExtInst>(Op0)) {
400 // (mul (sext x), cst) --> (sext (mul x, cst'))
401 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
402 if (Op0Conv->hasOneUse()) {
403 Constant *CI =
404 ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)->getType());
405 if (ConstantExpr::getSExt(CI, I.getType()) == Op1C &&
406 willNotOverflowSignedMul(Op0Conv->getOperand(0), CI, I)) {
407 // Insert the new, smaller mul.
408 Value *NewMul =
409 Builder.CreateNSWMul(Op0Conv->getOperand(0), CI, "mulconv");
410 return new SExtInst(NewMul, I.getType());
411 }
412 }
413 }
414
415 // (mul (sext x), (sext y)) --> (sext (mul int x, y))
416 if (SExtInst *Op1Conv = dyn_cast<SExtInst>(Op1)) {
417 // Only do this if x/y have the same type, if at last one of them has a
418 // single use (so we don't increase the number of sexts), and if the
419 // integer mul will not overflow.
420 if (Op0Conv->getOperand(0)->getType() ==
421 Op1Conv->getOperand(0)->getType() &&
422 (Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&
423 willNotOverflowSignedMul(Op0Conv->getOperand(0),
424 Op1Conv->getOperand(0), I)) {
425 // Insert the new integer mul.
426 Value *NewMul = Builder.CreateNSWMul(
427 Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
428 return new SExtInst(NewMul, I.getType());
429 }
430 }
431 }
432
433 // Check for (mul (zext x), y), see if we can merge this into an
434 // integer mul followed by a zext.
435 if (auto *Op0Conv = dyn_cast<ZExtInst>(Op0)) {
436 // (mul (zext x), cst) --> (zext (mul x, cst'))
437 if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
438 if (Op0Conv->hasOneUse()) {
439 Constant *CI =
440 ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)->getType());
441 if (ConstantExpr::getZExt(CI, I.getType()) == Op1C &&
442 willNotOverflowUnsignedMul(Op0Conv->getOperand(0), CI, I)) {
443 // Insert the new, smaller mul.
444 Value *NewMul =
445 Builder.CreateNUWMul(Op0Conv->getOperand(0), CI, "mulconv");
446 return new ZExtInst(NewMul, I.getType());
447 }
448 }
449 }
450
451 // (mul (zext x), (zext y)) --> (zext (mul int x, y))
452 if (auto *Op1Conv = dyn_cast<ZExtInst>(Op1)) {
453 // Only do this if x/y have the same type, if at last one of them has a
454 // single use (so we don't increase the number of zexts), and if the
455 // integer mul will not overflow.
456 if (Op0Conv->getOperand(0)->getType() ==
457 Op1Conv->getOperand(0)->getType() &&
458 (Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&
459 willNotOverflowUnsignedMul(Op0Conv->getOperand(0),
460 Op1Conv->getOperand(0), I)) {
461 // Insert the new integer mul.
462 Value *NewMul = Builder.CreateNUWMul(
463 Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
464 return new ZExtInst(NewMul, I.getType());
465 }
466 }
467 }
468
469 if (!I.hasNoSignedWrap() && willNotOverflowSignedMul(Op0, Op1, I)) {
470 Changed = true;
471 I.setHasNoSignedWrap(true);
472 }
473
474 if (!I.hasNoUnsignedWrap() && willNotOverflowUnsignedMul(Op0, Op1, I)) {
475 Changed = true;
476 I.setHasNoUnsignedWrap(true);
477 }
478
479 return Changed ? &I : nullptr;
480}
481
482/// Detect pattern log2(Y * 0.5) with corresponding fast math flags.
483static void detectLog2OfHalf(Value *&Op, Value *&Y, IntrinsicInst *&Log2) {
484 if (!Op->hasOneUse())
485 return;
486
487 IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op);
488 if (!II)
489 return;
490 if (II->getIntrinsicID() != Intrinsic::log2 || !II->isFast())
491 return;
492 Log2 = II;
493
494 Value *OpLog2Of = II->getArgOperand(0);
495 if (!OpLog2Of->hasOneUse())
496 return;
497
498 Instruction *I = dyn_cast<Instruction>(OpLog2Of);
499 if (!I)
500 return;
501
502 if (I->getOpcode() != Instruction::FMul || !I->isFast())
503 return;
504
505 if (match(I->getOperand(0), m_SpecificFP(0.5)))
506 Y = I->getOperand(1);
507 else if (match(I->getOperand(1), m_SpecificFP(0.5)))
508 Y = I->getOperand(0);
509}
510
511static bool isFiniteNonZeroFp(Constant *C) {
512 if (C->getType()->isVectorTy()) {
513 for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E;
514 ++I) {
515 ConstantFP *CFP = dyn_cast_or_null<ConstantFP>(C->getAggregateElement(I));
516 if (!CFP || !CFP->getValueAPF().isFiniteNonZero())
517 return false;
518 }
519 return true;
520 }
521
522 return isa<ConstantFP>(C) &&
523 cast<ConstantFP>(C)->getValueAPF().isFiniteNonZero();
524}
525
526static bool isNormalFp(Constant *C) {
527 if (C->getType()->isVectorTy()) {
528 for (unsigned I = 0, E = C->getType()->getVectorNumElements(); I != E;
529 ++I) {
530 ConstantFP *CFP = dyn_cast_or_null<ConstantFP>(C->getAggregateElement(I));
531 if (!CFP || !CFP->getValueAPF().isNormal())
532 return false;
533 }
534 return true;
535 }
536
537 return isa<ConstantFP>(C) && cast<ConstantFP>(C)->getValueAPF().isNormal();
538}
539
540/// Helper function of InstCombiner::visitFMul(BinaryOperator(). It returns
541/// true iff the given value is FMul or FDiv with one and only one operand
542/// being a normal constant (i.e. not Zero/NaN/Infinity).
543static bool isFMulOrFDivWithConstant(Value *V) {
544 Instruction *I = dyn_cast<Instruction>(V);
545 if (!I || (I->getOpcode() != Instruction::FMul &&
546 I->getOpcode() != Instruction::FDiv))
547 return false;
548
549 Constant *C0 = dyn_cast<Constant>(I->getOperand(0));
550 Constant *C1 = dyn_cast<Constant>(I->getOperand(1));
551
552 if (C0 && C1)
553 return false;
554
555 return (C0 && isFiniteNonZeroFp(C0)) || (C1 && isFiniteNonZeroFp(C1));
556}
557
558/// foldFMulConst() is a helper routine of InstCombiner::visitFMul().
559/// The input \p FMulOrDiv is a FMul/FDiv with one and only one operand
560/// being a constant (i.e. isFMulOrFDivWithConstant(FMulOrDiv) == true).
561/// This function is to simplify "FMulOrDiv * C" and returns the
562/// resulting expression. Note that this function could return NULL in
563/// case the constants cannot be folded into a normal floating-point.
564Value *InstCombiner::foldFMulConst(Instruction *FMulOrDiv, Constant *C,
565 Instruction *InsertBefore) {
566 assert(isFMulOrFDivWithConstant(FMulOrDiv) && "V is invalid")(static_cast <bool> (isFMulOrFDivWithConstant(FMulOrDiv
) && "V is invalid") ? void (0) : __assert_fail ("isFMulOrFDivWithConstant(FMulOrDiv) && \"V is invalid\""
, "/build/llvm-toolchain-snapshot-6.0~svn321459/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp"
, 566, __extension__ __PRETTY_FUNCTION__));
567
568 Value *Opnd0 = FMulOrDiv->getOperand(0);
569 Value *Opnd1 = FMulOrDiv->getOperand(1);
570
571 Constant *C0 = dyn_cast<Constant>(Opnd0);
572 Constant *C1 = dyn_cast<Constant>(Opnd1);
573
574 BinaryOperator *R = nullptr;
575
576 // (X * C0) * C => X * (C0*C)
577 if (FMulOrDiv->getOpcode() == Instruction::FMul) {
578 Constant *F = ConstantExpr::getFMul(C1 ? C1 : C0, C);
579 if (isNormalFp(F))
580 R = BinaryOperator::CreateFMul(C1 ? Opnd0 : Opnd1, F);
581 } else {
582 if (C0) {
583 // (C0 / X) * C => (C0 * C) / X
584 if (FMulOrDiv->hasOneUse()) {
585 // It would otherwise introduce another div.
586 Constant *F = ConstantExpr::getFMul(C0, C);
587 if (isNormalFp(F))
588 R = BinaryOperator::CreateFDiv(F, Opnd1);
589 }
590 } else {
591 // (X / C1) * C => X * (C/C1) if C/C1 is not a denormal
592 Constant *F = ConstantExpr::getFDiv(C, C1);
593 if (isNormalFp(F)) {
594 R = BinaryOperator::CreateFMul(Opnd0, F);
595 } else {
596 // (X / C1) * C => X / (C1/C)
597 Constant *F = ConstantExpr::getFDiv(C1, C);
598 if (isNormalFp(F))
599 R = BinaryOperator::CreateFDiv(Opnd0, F);
600 }
601 }
602 }
603
604 if (R) {
605 R->setFast(true);
606 InsertNewInstWith(R, *InsertBefore);
607 }
608
609 return R;
610}
611
612Instruction *InstCombiner::visitFMul(BinaryOperator &I) {
613 bool Changed = SimplifyAssociativeOrCommutative(I);
614 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
615
616 if (Value *V = SimplifyVectorOp(I))
617 return replaceInstUsesWith(I, V);
618
619 if (isa<Constant>(Op0))
620 std::swap(Op0, Op1);
621
622 if (Value *V = SimplifyFMulInst(Op0, Op1, I.getFastMathFlags(),
623 SQ.getWithInstruction(&I)))
624 return replaceInstUsesWith(I, V);
625
626 bool AllowReassociate = I.isFast();
627
628 // Simplify mul instructions with a constant RHS.
629 if (isa<Constant>(Op1)) {
630 if (Instruction *FoldedMul = foldOpWithConstantIntoOperand(I))
631 return FoldedMul;
632
633 // (fmul X, -1.0) --> (fsub -0.0, X)
634 if (match(Op1, m_SpecificFP(-1.0))) {
635 Constant *NegZero = ConstantFP::getNegativeZero(Op1->getType());
636 Instruction *RI = BinaryOperator::CreateFSub(NegZero, Op0);
637 RI->copyFastMathFlags(&I);
638 return RI;
639 }
640
641 Constant *C = cast<Constant>(Op1);
642 if (AllowReassociate && isFiniteNonZeroFp(C)) {
643 // Let MDC denote an expression in one of these forms:
644 // X * C, C/X, X/C, where C is a constant.
645 //
646 // Try to simplify "MDC * Constant"
647 if (isFMulOrFDivWithConstant(Op0))
648 if (Value *V = foldFMulConst(cast<Instruction>(Op0), C, &I))
649 return replaceInstUsesWith(I, V);
650
651 // (MDC +/- C1) * C => (MDC * C) +/- (C1 * C)
652 Instruction *FAddSub = dyn_cast<Instruction>(Op0);
653 if (FAddSub &&
654 (FAddSub->getOpcode() == Instruction::FAdd ||
655 FAddSub->getOpcode() == Instruction::FSub)) {
656 Value *Opnd0 = FAddSub->getOperand(0);
657 Value *Opnd1 = FAddSub->getOperand(1);
658 Constant *C0 = dyn_cast<Constant>(Opnd0);
659 Constant *C1 = dyn_cast<Constant>(Opnd1);
660 bool Swap = false;
661 if (C0) {
662 std::swap(C0, C1);
663 std::swap(Opnd0, Opnd1);
664 Swap = true;
665 }
666
667 if (C1 && isFiniteNonZeroFp(C1) && isFMulOrFDivWithConstant(Opnd0)) {
668 Value *M1 = ConstantExpr::getFMul(C1, C);
669 Value *M0 = isNormalFp(cast<Constant>(M1)) ?
670 foldFMulConst(cast<Instruction>(Opnd0), C, &I) :
671 nullptr;
672 if (M0 && M1) {
673 if (Swap && FAddSub->getOpcode() == Instruction::FSub)
674 std::swap(M0, M1);
675
676 Instruction *RI = (FAddSub->getOpcode() == Instruction::FAdd)
677 ? BinaryOperator::CreateFAdd(M0, M1)
678 : BinaryOperator::CreateFSub(M0, M1);
679 RI->copyFastMathFlags(&I);
680 return RI;
681 }
682 }
683 }
684 }
685 }
686
687 if (Op0 == Op1) {
688 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0)) {
689 // sqrt(X) * sqrt(X) -> X
690 if (AllowReassociate && II->getIntrinsicID() == Intrinsic::sqrt)
691 return replaceInstUsesWith(I, II->getOperand(0));
692
693 // fabs(X) * fabs(X) -> X * X
694 if (II->getIntrinsicID() == Intrinsic::fabs) {
695 Instruction *FMulVal = BinaryOperator::CreateFMul(II->getOperand(0),
696 II->getOperand(0),
697 I.getName());
698 FMulVal->copyFastMathFlags(&I);
699 return FMulVal;
700 }
701 }
702 }
703
704 // Under unsafe algebra do:
705 // X * log2(0.5*Y) = X*log2(Y) - X
706 if (AllowReassociate) {
707 Value *OpX = nullptr;
708 Value *OpY = nullptr;
709 IntrinsicInst *Log2;
710 detectLog2OfHalf(Op0, OpY, Log2);
711 if (OpY) {
712 OpX = Op1;
713 } else {
714 detectLog2OfHalf(Op1, OpY, Log2);
715 if (OpY) {
716 OpX = Op0;
717 }
718 }
719 // if pattern detected emit alternate sequence
720 if (OpX && OpY) {
721 BuilderTy::FastMathFlagGuard Guard(Builder);
722 Builder.setFastMathFlags(Log2->getFastMathFlags());
723 Log2->setArgOperand(0, OpY);
724 Value *FMulVal = Builder.CreateFMul(OpX, Log2);
725 Value *FSub = Builder.CreateFSub(FMulVal, OpX);
726 FSub->takeName(&I);
727 return replaceInstUsesWith(I, FSub);
728 }
729 }
730
731 // Handle symmetric situation in a 2-iteration loop
732 Value *Opnd0 = Op0;
733 Value *Opnd1 = Op1;
734 for (int i = 0; i < 2; i++) {
735 bool IgnoreZeroSign = I.hasNoSignedZeros();
736 if (BinaryOperator::isFNeg(Opnd0, IgnoreZeroSign)) {
737 BuilderTy::FastMathFlagGuard Guard(Builder);
738 Builder.setFastMathFlags(I.getFastMathFlags());
739
740 Value *N0 = dyn_castFNegVal(Opnd0, IgnoreZeroSign);
741 Value *N1 = dyn_castFNegVal(Opnd1, IgnoreZeroSign);
742
743 // -X * -Y => X*Y
744 if (N1) {
745 Value *FMul = Builder.CreateFMul(N0, N1);
746 FMul->takeName(&I);
747 return replaceInstUsesWith(I, FMul);
748 }
749
750 if (Opnd0->hasOneUse()) {
751 // -X * Y => -(X*Y) (Promote negation as high as possible)
752 Value *T = Builder.CreateFMul(N0, Opnd1);
753 Value *Neg = Builder.CreateFNeg(T);
754 Neg->takeName(&I);
755 return replaceInstUsesWith(I, Neg);
756 }
757 }
758
759 // Handle specials cases for FMul with selects feeding the operation
760 if (Value *V = SimplifySelectsFeedingBinaryOp(I, Op0, Op1))
761 return replaceInstUsesWith(I, V);
762
763 // (X*Y) * X => (X*X) * Y where Y != X
764 // The purpose is two-fold:
765 // 1) to form a power expression (of X).
766 // 2) potentially shorten the critical path: After transformation, the
767 // latency of the instruction Y is amortized by the expression of X*X,
768 // and therefore Y is in a "less critical" position compared to what it
769 // was before the transformation.
770 if (AllowReassociate) {
771 Value *Opnd0_0, *Opnd0_1;
772 if (Opnd0->hasOneUse() &&
773 match(Opnd0, m_FMul(m_Value(Opnd0_0), m_Value(Opnd0_1)))) {
774 Value *Y = nullptr;
775 if (Opnd0_0 == Opnd1 && Opnd0_1 != Opnd1)
776 Y = Opnd0_1;
777 else if (Opnd0_1 == Opnd1 && Opnd0_0 != Opnd1)
778 Y = Opnd0_0;
779
780 if (Y) {
781 BuilderTy::FastMathFlagGuard Guard(Builder);
782 Builder.setFastMathFlags(I.getFastMathFlags());
783 Value *T = Builder.CreateFMul(Opnd1, Opnd1);
784 Value *R = Builder.CreateFMul(T, Y);
785 R->takeName(&I);
786 return replaceInstUsesWith(I, R);
787 }
788 }
789 }
790
791 if (!isa<Constant>(Op1))
792 std::swap(Opnd0, Opnd1);
793 else
794 break;
795 }
796
797 return Changed ? &I : nullptr;
798}
799
800/// Fold a divide or remainder with a select instruction divisor when one of the
801/// select operands is zero. In that case, we can use the other select operand
802/// because div/rem by zero is undefined.
803bool InstCombiner::simplifyDivRemOfSelectWithZeroOp(BinaryOperator &I) {
804 SelectInst *SI = dyn_cast<SelectInst>(I.getOperand(1));
805 if (!SI)
6
←
Assuming 'SI' is non-null
→
7
←
Taking false branch
→
806 return false;
807
808 int NonNullOperand;
809 if (match(SI->getTrueValue(), m_Zero()))
8
←
Taking false branch
→
810 // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
811 NonNullOperand = 2;
812 else if (match(SI->getFalseValue(), m_Zero()))
9
←
Assuming the condition is true
→
10
←
Taking true branch
→
813 // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
814 NonNullOperand = 1;
815 else
816 return false;
817
818 // Change the div/rem to use 'Y' instead of the select.
819 I.setOperand(1, SI->getOperand(NonNullOperand));
820
821 // Okay, we know we replace the operand of the div/rem with 'Y' with no
822 // problem. However, the select, or the condition of the select may have
823 // multiple uses. Based on our knowledge that the operand must be non-zero,
824 // propagate the known value for the select into other uses of it, and
825 // propagate a known value of the condition into its other users.
826
827 // If the select and condition only have a single use, don't bother with this,
828 // early exit.
829 Value *SelectCond = SI->getCondition();
830 if (SI->use_empty() && SelectCond->hasOneUse())
831 return true;
832
833 // Scan the current block backward, looking for other uses of SI.
834 BasicBlock::iterator BBI = I.getIterator(), BBFront = I.getParent()->begin();
835 Type *CondTy = SelectCond->getType();
836 while (BBI != BBFront) {
11
←
Loop condition is true. Entering loop body
→
18
←
Loop condition is true. Entering loop body
→
25
←
Loop condition is true. Entering loop body
→
33
←
Loop condition is true. Entering loop body
→
837 --BBI;
838 // If we found a call to a function, we can't assume it will return, so
839 // information from below it cannot be propagated above it.
840 if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
841 break;
842
843 // Replace uses of the select or its condition with the known values.
844 for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
13
←
Loop condition is false. Execution continues on line 857
→
20
←
Loop condition is false. Execution continues on line 857
→
27
←
Loop condition is false. Execution continues on line 857
→
34
←
Loop condition is true. Entering loop body
→
845 I != E; ++I) {
12
←
Assuming 'I' is equal to 'E'
→
19
←
Assuming 'I' is equal to 'E'
→
26
←
Assuming 'I' is equal to 'E'
→
846 if (*I == SI) {
35
←
Assuming the condition is true
→
36
←
Taking true branch
→
847 *I = SI->getOperand(NonNullOperand);
37
←
Called C++ object pointer is null
848 Worklist.Add(&*BBI);
849 } else if (*I == SelectCond) {
850 *I = NonNullOperand == 1 ? ConstantInt::getTrue(CondTy)
851 : ConstantInt::getFalse(CondTy);
852 Worklist.Add(&*BBI);
853 }
854 }
855
856 // If we past the instruction, quit looking for it.
857 if (&*BBI == SI)
14
←
Assuming the condition is false
→
15
←
Taking false branch
→
21
←
Assuming the condition is false
→
22
←
Taking false branch
→
28
←
Assuming the condition is true
→
29
←
Taking true branch
→
858 SI = nullptr;
30
←
Null pointer value stored to 'SI'
→
859 if (&*BBI == SelectCond)
16
←
Assuming the condition is false
→
17
←
Taking false branch
→
23
←
Assuming the condition is false
→
24
←
Taking false branch
→
31
←
Assuming the condition is false
→
32
←
Taking false branch
→
860 SelectCond = nullptr;
861
862 // If we ran out of things to eliminate, break out of the loop.
863 if (!SelectCond && !SI)
864 break;
865
866 }
867 return true;
868}
869
870/// This function implements the transforms common to both integer division
871/// instructions (udiv and sdiv). It is called by the visitors to those integer
872/// division instructions.
873/// @brief Common integer divide transforms
874Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) {
875 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
876
877 // The RHS is known non-zero.
878 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, I)) {
879 I.setOperand(1, V);
880 return &I;
881 }
882
883 // Handle cases involving: [su]div X, (select Cond, Y, Z)
884 // This does not apply for fdiv.
885 if (simplifyDivRemOfSelectWithZeroOp(I))
886 return &I;
887
888 if (Instruction *LHS = dyn_cast<Instruction>(Op0)) {
889 const APInt *C2;
890 if (match(Op1, m_APInt(C2))) {
891 Value *X;
892 const APInt *C1;
893 bool IsSigned = I.getOpcode() == Instruction::SDiv;
894
895 // (X / C1) / C2 -> X / (C1*C2)
896 if ((IsSigned && match(LHS, m_SDiv(m_Value(X), m_APInt(C1)))) ||
897 (!IsSigned && match(LHS, m_UDiv(m_Value(X), m_APInt(C1))))) {
898 APInt Product(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
899 if (!MultiplyOverflows(*C1, *C2, Product, IsSigned))
900 return BinaryOperator::Create(I.getOpcode(), X,
901 ConstantInt::get(I.getType(), Product));
902 }
903
904 if ((IsSigned && match(LHS, m_NSWMul(m_Value(X), m_APInt(C1)))) ||
905 (!IsSigned && match(LHS, m_NUWMul(m_Value(X), m_APInt(C1))))) {
906 APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
907
908 // (X * C1) / C2 -> X / (C2 / C1) if C2 is a multiple of C1.
909 if (IsMultiple(*C2, *C1, Quotient, IsSigned)) {
910 BinaryOperator *BO = BinaryOperator::Create(
911 I.getOpcode(), X, ConstantInt::get(X->getType(), Quotient));
912 BO->setIsExact(I.isExact());
913 return BO;
914 }
915
916 // (X * C1) / C2 -> X * (C1 / C2) if C1 is a multiple of C2.
917 if (IsMultiple(*C1, *C2, Quotient, IsSigned)) {
918 BinaryOperator *BO = BinaryOperator::Create(
919 Instruction::Mul, X, ConstantInt::get(X->getType(), Quotient));
920 BO->setHasNoUnsignedWrap(
921 !IsSigned &&
922 cast<OverflowingBinaryOperator>(LHS)->hasNoUnsignedWrap());
923 BO->setHasNoSignedWrap(
924 cast<OverflowingBinaryOperator>(LHS)->hasNoSignedWrap());
925 return BO;
926 }
927 }
928
929 if ((IsSigned && match(LHS, m_NSWShl(m_Value(X), m_APInt(C1))) &&
930 *C1 != C1->getBitWidth() - 1) ||
931 (!IsSigned && match(LHS, m_NUWShl(m_Value(X), m_APInt(C1))))) {
932 APInt Quotient(C1->getBitWidth(), /*Val=*/0ULL, IsSigned);
933 APInt C1Shifted = APInt::getOneBitSet(
934 C1->getBitWidth(), static_cast<unsigned>(C1->getLimitedValue()));
935
936 // (X << C1) / C2 -> X / (C2 >> C1) if C2 is a multiple of C1.
937 if (IsMultiple(*C2, C1Shifted, Quotient, IsSigned)) {
938 BinaryOperator *BO = BinaryOperator::Create(
939 I.getOpcode(), X, ConstantInt::get(X->getType(), Quotient));
940 BO->setIsExact(I.isExact());
941 return BO;
942 }
943
944 // (X << C1) / C2 -> X * (C2 >> C1) if C1 is a multiple of C2.
945 if (IsMultiple(C1Shifted, *C2, Quotient, IsSigned)) {
946 BinaryOperator *BO = BinaryOperator::Create(
947 Instruction::Mul, X, ConstantInt::get(X->getType(), Quotient));
948 BO->setHasNoUnsignedWrap(
949 !IsSigned &&
950 cast<OverflowingBinaryOperator>(LHS)->hasNoUnsignedWrap());
951 BO->setHasNoSignedWrap(
952 cast<OverflowingBinaryOperator>(LHS)->hasNoSignedWrap());
953 return BO;
954 }
955 }
956
957 if (!C2->isNullValue()) // avoid X udiv 0
958 if (Instruction *FoldedDiv = foldOpWithConstantIntoOperand(I))
959 return FoldedDiv;
960 }
961 }
962
963 if (match(Op0, m_One())) {
964 assert(!I.getType()->isIntOrIntVectorTy(1) && "i1 divide not removed?")(static_cast <bool> (!I.getType()->isIntOrIntVectorTy
(1) && "i1 divide not removed?") ? void (0) : __assert_fail
("!I.getType()->isIntOrIntVectorTy(1) && \"i1 divide not removed?\""
, "/build/llvm-toolchain-snapshot-6.0~svn321459/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp"
, 964, __extension__ __PRETTY_FUNCTION__));
965 if (I.getOpcode() == Instruction::SDiv) {
966 // If Op1 is 0 then it's undefined behaviour, if Op1 is 1 then the
967 // result is one, if Op1 is -1 then the result is minus one, otherwise
968 // it's zero.
969 Value *Inc = Builder.CreateAdd(Op1, Op0);
970 Value *Cmp = Builder.CreateICmpULT(Inc, ConstantInt::get(I.getType(), 3));
971 return SelectInst::Create(Cmp, Op1, ConstantInt::get(I.getType(), 0));
972 } else {
973 // If Op1 is 0 then it's undefined behaviour. If Op1 is 1 then the
974 // result is one, otherwise it's zero.
975 return new ZExtInst(Builder.CreateICmpEQ(Op1, Op0), I.getType());
976 }
977 }
978
979 // See if we can fold away this div instruction.
980 if (SimplifyDemandedInstructionBits(I))
981 return &I;
982
983 // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y
984 Value *X = nullptr, *Z = nullptr;
985 if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1
986 bool isSigned = I.getOpcode() == Instruction::SDiv;
987 if ((isSigned && match(Z, m_SRem(m_Specific(X), m_Specific(Op1)))) ||
988 (!isSigned && match(Z, m_URem(m_Specific(X), m_Specific(Op1)))))
989 return BinaryOperator::Create(I.getOpcode(), X, Op1);
990 }
991
992 return nullptr;
993}
994
995static const unsigned MaxDepth = 6;
996
997namespace {
998
999using FoldUDivOperandCb = Instruction *(*)(Value *Op0, Value *Op1,
1000 const BinaryOperator &I,
1001 InstCombiner &IC);
1002
1003/// \brief Used to maintain state for visitUDivOperand().
1004struct UDivFoldAction {
1005 /// Informs visitUDiv() how to fold this operand. This can be zero if this
1006 /// action joins two actions together.
1007 FoldUDivOperandCb FoldAction;
1008
1009 /// Which operand to fold.
1010 Value *OperandToFold;
1011
1012 union {
1013 /// The instruction returned when FoldAction is invoked.
1014 Instruction *FoldResult;
1015
1016 /// Stores the LHS action index if this action joins two actions together.
1017 size_t SelectLHSIdx;
1018 };
1019
1020 UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand)
1021 : FoldAction(FA), OperandToFold(InputOperand), FoldResult(nullptr) {}
1022 UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand, size_t SLHS)
1023 : FoldAction(FA), OperandToFold(InputOperand), SelectLHSIdx(SLHS) {}
1024};
1025
1026} // end anonymous namespace
1027
1028// X udiv 2^C -> X >> C
1029static Instruction *foldUDivPow2Cst(Value *Op0, Value *Op1,
1030 const BinaryOperator &I, InstCombiner &IC) {
1031 const APInt &C = cast<Constant>(Op1)->getUniqueInteger();
1032 BinaryOperator *LShr = BinaryOperator::CreateLShr(
1033 Op0, ConstantInt::get(Op0->getType(), C.logBase2()));
1034 if (I.isExact())
1035 LShr->setIsExact();
1036 return LShr;
1037}
1038
1039// X udiv C, where C >= signbit
1040static Instruction *foldUDivNegCst(Value *Op0, Value *Op1,
1041 const BinaryOperator &I, InstCombiner &IC) {
1042 Value *ICI = IC.Builder.CreateICmpULT(Op0, cast<ConstantInt>(Op1));
1043
1044 return SelectInst::Create(ICI, Constant::getNullValue(I.getType()),
1045 ConstantInt::get(I.getType(), 1));
1046}
1047
1048// X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
1049// X udiv (zext (C1 << N)), where C1 is "1<<C2" --> X >> (N+C2)
1050static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
1051 InstCombiner &IC) {
1052 Value *ShiftLeft;
1053 if (!match(Op1, m_ZExt(m_Value(ShiftLeft))))
1054 ShiftLeft = Op1;
1055
1056 const APInt *CI;
1057 Value *N;
1058 if (!match(ShiftLeft, m_Shl(m_APInt(CI), m_Value(N))))
1059 llvm_unreachable("match should never fail here!")::llvm::llvm_unreachable_internal("match should never fail here!"
, "/build/llvm-toolchain-snapshot-6.0~svn321459/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp"
, 1059);
1060 if (*CI != 1)
1061 N = IC.Builder.CreateAdd(N, ConstantInt::get(N->getType(), CI->logBase2()));
1062 if (Op1 != ShiftLeft)
1063 N = IC.Builder.CreateZExt(N, Op1->getType());
1064 BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N);
1065 if (I.isExact())
1066 LShr->setIsExact();
1067 return LShr;
1068}
1069
1070// \brief Recursively visits the possible right hand operands of a udiv
1071// instruction, seeing through select instructions, to determine if we can
1072// replace the udiv with something simpler. If we find that an operand is not
1073// able to simplify the udiv, we abort the entire transformation.
1074static size_t visitUDivOperand(Value *Op0, Value *Op1, const BinaryOperator &I,
1075 SmallVectorImpl<UDivFoldAction> &Actions,
1076 unsigned Depth = 0) {
1077 // Check to see if this is an unsigned division with an exact power of 2,
1078 // if so, convert to a right shift.
1079 if (match(Op1, m_Power2())) {
1080 Actions.push_back(UDivFoldAction(foldUDivPow2Cst, Op1));
1081 return Actions.size();
1082 }
1083
1084 if (ConstantInt *C = dyn_cast<ConstantInt>(Op1))
1085 // X udiv C, where C >= signbit
1086 if (C->getValue().isNegative()) {
1087 Actions.push_back(UDivFoldAction(foldUDivNegCst, C));
1088 return Actions.size();
1089 }
1090
1091 // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
1092 if (match(Op1, m_Shl(m_Power2(), m_Value())) ||
1093 match(Op1, m_ZExt(m_Shl(m_Power2(), m_Value())))) {
1094 Actions.push_back(UDivFoldAction(foldUDivShl, Op1));
1095 return Actions.size();
1096 }
1097
1098 // The remaining tests are all recursive, so bail out if we hit the limit.
1099 if (Depth++ == MaxDepth)
1100 return 0;
1101
1102 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1103 if (size_t LHSIdx =
1104 visitUDivOperand(Op0, SI->getOperand(1), I, Actions, Depth))
1105 if (visitUDivOperand(Op0, SI->getOperand(2), I, Actions, Depth)) {
1106 Actions.push_back(UDivFoldAction(nullptr, Op1, LHSIdx - 1));
1107 return Actions.size();
1108 }
1109
1110 return 0;
1111}
1112
1113/// If we have zero-extended operands of an unsigned div or rem, we may be able
1114/// to narrow the operation (sink the zext below the math).
1115static Instruction *narrowUDivURem(BinaryOperator &I,
1116 InstCombiner::BuilderTy &Builder) {
1117 Instruction::BinaryOps Opcode = I.getOpcode();
1118 Value *N = I.getOperand(0);
1119 Value *D = I.getOperand(1);
1120 Type *Ty = I.getType();
1121 Value *X, *Y;
1122 if (match(N, m_ZExt(m_Value(X))) && match(D, m_ZExt(m_Value(Y))) &&
1123 X->getType() == Y->getType() && (N->hasOneUse() || D->hasOneUse())) {
1124 // udiv (zext X), (zext Y) --> zext (udiv X, Y)
1125 // urem (zext X), (zext Y) --> zext (urem X, Y)
1126 Value *NarrowOp = Builder.CreateBinOp(Opcode, X, Y);
1127 return new ZExtInst(NarrowOp, Ty);
1128 }
1129
1130 Constant *C;
1131 if ((match(N, m_OneUse(m_ZExt(m_Value(X)))) && match(D, m_Constant(C))) ||
1132 (match(D, m_OneUse(m_ZExt(m_Value(X)))) && match(N, m_Constant(C)))) {
1133 // If the constant is the same in the smaller type, use the narrow version.
1134 Constant *TruncC = ConstantExpr::getTrunc(C, X->getType());
1135 if (ConstantExpr::getZExt(TruncC, Ty) != C)
1136 return nullptr;
1137
1138 // udiv (zext X), C --> zext (udiv X, C')
1139 // urem (zext X), C --> zext (urem X, C')
1140 // udiv C, (zext X) --> zext (udiv C', X)
1141 // urem C, (zext X) --> zext (urem C', X)
1142 Value *NarrowOp = isa<Constant>(D) ? Builder.CreateBinOp(Opcode, X, TruncC)
1143 : Builder.CreateBinOp(Opcode, TruncC, X);
1144 return new ZExtInst(NarrowOp, Ty);
1145 }
1146
1147 return nullptr;
1148}
1149
1150Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
1151 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1152
1153 if (Value *V = SimplifyVectorOp(I))
1154 return replaceInstUsesWith(I, V);
1155
1156 if (Value *V = SimplifyUDivInst(Op0, Op1, SQ.getWithInstruction(&I)))
1157 return replaceInstUsesWith(I, V);
1158
1159 // Handle the integer div common cases
1160 if (Instruction *Common = commonIDivTransforms(I))
1161 return Common;
1162
1163 // (x lshr C1) udiv C2 --> x udiv (C2 << C1)
1164 {
1165 Value *X;
1166 const APInt *C1, *C2;
1167 if (match(Op0, m_LShr(m_Value(X), m_APInt(C1))) &&
1168 match(Op1, m_APInt(C2))) {
1169 bool Overflow;
1170 APInt C2ShlC1 = C2->ushl_ov(*C1, Overflow);
1171 if (!Overflow) {
1172 bool IsExact = I.isExact() && match(Op0, m_Exact(m_Value()));
1173 BinaryOperator *BO = BinaryOperator::CreateUDiv(
1174 X, ConstantInt::get(X->getType(), C2ShlC1));
1175 if (IsExact)
1176 BO->setIsExact();
1177 return BO;
1178 }
1179 }
1180 }
1181
1182 if (Instruction *NarrowDiv = narrowUDivURem(I, Builder))
1183 return NarrowDiv;
1184
1185 // (LHS udiv (select (select (...)))) -> (LHS >> (select (select (...))))
1186 SmallVector<UDivFoldAction, 6> UDivActions;
1187 if (visitUDivOperand(Op0, Op1, I, UDivActions))
1188 for (unsigned i = 0, e = UDivActions.size(); i != e; ++i) {
1189 FoldUDivOperandCb Action = UDivActions[i].FoldAction;
1190 Value *ActionOp1 = UDivActions[i].OperandToFold;
1191 Instruction *Inst;
1192 if (Action)
1193 Inst = Action(Op0, ActionOp1, I, *this);
1194 else {
1195 // This action joins two actions together. The RHS of this action is
1196 // simply the last action we processed, we saved the LHS action index in
1197 // the joining action.
1198 size_t SelectRHSIdx = i - 1;
1199 Value *SelectRHS = UDivActions[SelectRHSIdx].FoldResult;
1200 size_t SelectLHSIdx = UDivActions[i].SelectLHSIdx;
1201 Value *SelectLHS = UDivActions[SelectLHSIdx].FoldResult;
1202 Inst = SelectInst::Create(cast<SelectInst>(ActionOp1)->getCondition(),
1203 SelectLHS, SelectRHS);
1204 }
1205
1206 // If this is the last action to process, return it to the InstCombiner.
1207 // Otherwise, we insert it before the UDiv and record it so that we may
1208 // use it as part of a joining action (i.e., a SelectInst).
1209 if (e - i != 1) {
1210 Inst->insertBefore(&I);
1211 UDivActions[i].FoldResult = Inst;
1212 } else
1213 return Inst;
1214 }
1215
1216 return nullptr;
1217}
1218
1219Instruction *InstCombiner::visitSDiv(BinaryOperator &I) {
1220 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1221
1222 if (Value *V = SimplifyVectorOp(I))
1223 return replaceInstUsesWith(I, V);
1224
1225 if (Value *V = SimplifySDivInst(Op0, Op1, SQ.getWithInstruction(&I)))
1226 return replaceInstUsesWith(I, V);
1227
1228 // Handle the integer div common cases
1229 if (Instruction *Common = commonIDivTransforms(I))
1230 return Common;
1231
1232 const APInt *Op1C;
1233 if (match(Op1, m_APInt(Op1C))) {
1234 // sdiv X, -1 == -X
1235 if (Op1C->isAllOnesValue())
1236 return BinaryOperator::CreateNeg(Op0);
1237
1238 // sdiv exact X, C --> ashr exact X, log2(C)
1239 if (I.isExact() && Op1C->isNonNegative() && Op1C->isPowerOf2()) {
1240 Value *ShAmt = ConstantInt::get(Op1->getType(), Op1C->exactLogBase2());
1241 return BinaryOperator::CreateExactAShr(Op0, ShAmt, I.getName());
1242 }
1243
1244 // If the dividend is sign-extended and the constant divisor is small enough
1245 // to fit in the source type, shrink the division to the narrower type:
1246 // (sext X) sdiv C --> sext (X sdiv C)
1247 Value *Op0Src;
1248 if (match(Op0, m_OneUse(m_SExt(m_Value(Op0Src)))) &&
1249 Op0Src->getType()->getScalarSizeInBits() >= Op1C->getMinSignedBits()) {
1250
1251 // In the general case, we need to make sure that the dividend is not the
1252 // minimum signed value because dividing that by -1 is UB. But here, we
1253 // know that the -1 divisor case is already handled above.
1254
1255 Constant *NarrowDivisor =
1256 ConstantExpr::getTrunc(cast<Constant>(Op1), Op0Src->getType());
1257 Value *NarrowOp = Builder.CreateSDiv(Op0Src, NarrowDivisor);
1258 return new SExtInst(NarrowOp, Op0->getType());
1259 }
1260 }
1261
1262 if (Constant *RHS = dyn_cast<Constant>(Op1)) {
1263 // X/INT_MIN -> X == INT_MIN
1264 if (RHS->isMinSignedValue())
1265 return new ZExtInst(Builder.CreateICmpEQ(Op0, Op1), I.getType());
1266
1267 // -X/C --> X/-C provided the negation doesn't overflow.
1268 Value *X;
1269 if (match(Op0, m_NSWSub(m_Zero(), m_Value(X)))) {
1270 auto *BO = BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(RHS));
1271 BO->setIsExact(I.isExact());
1272 return BO;
1273 }
1274 }
1275
1276 // If the sign bits of both operands are zero (i.e. we can prove they are
1277 // unsigned inputs), turn this into a udiv.
1278 APInt Mask(APInt::getSignMask(I.getType()->getScalarSizeInBits()));
1279 if (MaskedValueIsZero(Op0, Mask, 0, &I)) {
1280 if (MaskedValueIsZero(Op1, Mask, 0, &I)) {
1281 // X sdiv Y -> X udiv Y, iff X and Y don't have sign bit set
1282 auto *BO = BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
1283 BO->setIsExact(I.isExact());
1284 return BO;
1285 }
1286
1287 if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/ true, 0, &I)) {
1288 // X sdiv (1 << Y) -> X udiv (1 << Y) ( -> X u>> Y)
1289 // Safe because the only negative value (1 << Y) can take on is
1290 // INT_MIN, and X sdiv INT_MIN == X udiv INT_MIN == 0 if X doesn't have
1291 // the sign bit set.
1292 auto *BO = BinaryOperator::CreateUDiv(Op0, Op1, I.getName());
1293 BO->setIsExact(I.isExact());
1294 return BO;
1295 }
1296 }
1297
1298 return nullptr;
1299}
1300
1301/// CvtFDivConstToReciprocal tries to convert X/C into X*1/C if C not a special
1302/// FP value and:
1303/// 1) 1/C is exact, or
1304/// 2) reciprocal is allowed.
1305/// If the conversion was successful, the simplified expression "X * 1/C" is
1306/// returned; otherwise, nullptr is returned.
1307static Instruction *CvtFDivConstToReciprocal(Value *Dividend, Constant *Divisor,
1308 bool AllowReciprocal) {
1309 if (!isa<ConstantFP>(Divisor)) // TODO: handle vectors.
1310 return nullptr;
1311
1312 const APFloat &FpVal = cast<ConstantFP>(Divisor)->getValueAPF();
1313 APFloat Reciprocal(FpVal.getSemantics());
1314 bool Cvt = FpVal.getExactInverse(&Reciprocal);
1315
1316 if (!Cvt && AllowReciprocal && FpVal.isFiniteNonZero()) {
1317 Reciprocal = APFloat(FpVal.getSemantics(), 1.0f);
1318 (void)Reciprocal.divide(FpVal, APFloat::rmNearestTiesToEven);
1319 Cvt = !Reciprocal.isDenormal();
1320 }
1321
1322 if (!Cvt)
1323 return nullptr;
1324
1325 ConstantFP *R;
1326 R = ConstantFP::get(Dividend->getType()->getContext(), Reciprocal);
1327 return BinaryOperator::CreateFMul(Dividend, R);
1328}
1329
1330Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
1331 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1332
1333 if (Value *V = SimplifyVectorOp(I))
1334 return replaceInstUsesWith(I, V);
1335
1336 if (Value *V = SimplifyFDivInst(Op0, Op1, I.getFastMathFlags(),
1337 SQ.getWithInstruction(&I)))
1338 return replaceInstUsesWith(I, V);
1339
1340 if (isa<Constant>(Op0))
1341 if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
1342 if (Instruction *R = FoldOpIntoSelect(I, SI))
1343 return R;
1344
1345 bool AllowReassociate = I.isFast();
1346 bool AllowReciprocal = I.hasAllowReciprocal();
1347
1348 if (Constant *Op1C = dyn_cast<Constant>(Op1)) {
1349 if (SelectInst *SI = dyn_cast<SelectInst>(Op0))
1350 if (Instruction *R = FoldOpIntoSelect(I, SI))
1351 return R;
1352
1353 if (AllowReassociate) {
1354 Constant *C1 = nullptr;
1355 Constant *C2 = Op1C;
1356 Value *X;
1357 Instruction *Res = nullptr;
1358
1359 if (match(Op0, m_FMul(m_Value(X), m_Constant(C1)))) {
1360 // (X*C1)/C2 => X * (C1/C2)
1361 //
1362 Constant *C = ConstantExpr::getFDiv(C1, C2);
1363 if (isNormalFp(C))
1364 Res = BinaryOperator::CreateFMul(X, C);
1365 } else if (match(Op0, m_FDiv(m_Value(X), m_Constant(C1)))) {
1366 // (X/C1)/C2 => X /(C2*C1) [=> X * 1/(C2*C1) if reciprocal is allowed]
1367 Constant *C = ConstantExpr::getFMul(C1, C2);
1368 if (isNormalFp(C)) {
1369 Res = CvtFDivConstToReciprocal(X, C, AllowReciprocal);
1370 if (!Res)
1371 Res = BinaryOperator::CreateFDiv(X, C);
1372 }
1373 }
1374
1375 if (Res) {
1376 Res->setFastMathFlags(I.getFastMathFlags());
1377 return Res;
1378 }
1379 }
1380
1381 // X / C => X * 1/C
1382 if (Instruction *T = CvtFDivConstToReciprocal(Op0, Op1C, AllowReciprocal)) {
1383 T->copyFastMathFlags(&I);
1384 return T;
1385 }
1386
1387 return nullptr;
1388 }
1389
1390 if (AllowReassociate && isa<Constant>(Op0)) {
1391 Constant *C1 = cast<Constant>(Op0), *C2;
1392 Constant *Fold = nullptr;
1393 Value *X;
1394 bool CreateDiv = true;
1395
1396 // C1 / (X*C2) => (C1/C2) / X
1397 if (match(Op1, m_FMul(m_Value(X), m_Constant(C2))))
1398 Fold = ConstantExpr::getFDiv(C1, C2);
1399 else if (match(Op1, m_FDiv(m_Value(X), m_Constant(C2)))) {
1400 // C1 / (X/C2) => (C1*C2) / X
1401 Fold = ConstantExpr::getFMul(C1, C2);
1402 } else if (match(Op1, m_FDiv(m_Constant(C2), m_Value(X)))) {
1403 // C1 / (C2/X) => (C1/C2) * X
1404 Fold = ConstantExpr::getFDiv(C1, C2);
1405 CreateDiv = false;
1406 }
1407
1408 if (Fold && isNormalFp(Fold)) {
1409 Instruction *R = CreateDiv ? BinaryOperator::CreateFDiv(Fold, X)
1410 : BinaryOperator::CreateFMul(X, Fold);
1411 R->setFastMathFlags(I.getFastMathFlags());
1412 return R;
1413 }
1414 return nullptr;
1415 }
1416
1417 if (AllowReassociate) {
1418 Value *X, *Y;
1419 Value *NewInst = nullptr;
1420 Instruction *SimpR = nullptr;
1421
1422 if (Op0->hasOneUse() && match(Op0, m_FDiv(m_Value(X), m_Value(Y)))) {
1423 // (X/Y) / Z => X / (Y*Z)
1424 if (!isa<Constant>(Y) || !isa<Constant>(Op1)) {
1425 NewInst = Builder.CreateFMul(Y, Op1);
1426 if (Instruction *RI = dyn_cast<Instruction>(NewInst)) {
1427 FastMathFlags Flags = I.getFastMathFlags();
1428 Flags &= cast<Instruction>(Op0)->getFastMathFlags();
1429 RI->setFastMathFlags(Flags);
1430 }
1431 SimpR = BinaryOperator::CreateFDiv(X, NewInst);
1432 }
1433 } else if (Op1->hasOneUse() && match(Op1, m_FDiv(m_Value(X), m_Value(Y)))) {
1434 // Z / (X/Y) => Z*Y / X
1435 if (!isa<Constant>(Y) || !isa<Constant>(Op0)) {
1436 NewInst = Builder.CreateFMul(Op0, Y);
1437 if (Instruction *RI = dyn_cast<Instruction>(NewInst)) {
1438 FastMathFlags Flags = I.getFastMathFlags();
1439 Flags &= cast<Instruction>(Op1)->getFastMathFlags();
1440 RI->setFastMathFlags(Flags);
1441 }
1442 SimpR = BinaryOperator::CreateFDiv(NewInst, X);
1443 }
1444 }
1445
1446 if (NewInst) {
1447 if (Instruction *T = dyn_cast<Instruction>(NewInst))
1448 T->setDebugLoc(I.getDebugLoc());
1449 SimpR->setFastMathFlags(I.getFastMathFlags());
1450 return SimpR;
1451 }
1452 }
1453
1454 Value *LHS;
1455 Value *RHS;
1456
1457 // -x / -y -> x / y
1458 if (match(Op0, m_FNeg(m_Value(LHS))) && match(Op1, m_FNeg(m_Value(RHS)))) {
1459 I.setOperand(0, LHS);
1460 I.setOperand(1, RHS);
1461 return &I;
1462 }
1463
1464 return nullptr;
1465}
1466
1467/// This function implements the transforms common to both integer remainder
1468/// instructions (urem and srem). It is called by the visitors to those integer
1469/// remainder instructions.
1470/// @brief Common integer remainder transforms
1471Instruction *InstCombiner::commonIRemTransforms(BinaryOperator &I) {
1472 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1473
1474 // The RHS is known non-zero.
1475 if (Value *V = simplifyValueKnownNonZero(I.getOperand(1), *this, I)) {
1476 I.setOperand(1, V);
1477 return &I;
1478 }
1479
1480 // Handle cases involving: rem X, (select Cond, Y, Z)
1481 if (simplifyDivRemOfSelectWithZeroOp(I))
1482 return &I;
1483
1484 if (isa<Constant>(Op1)) {
1485 if (Instruction *Op0I = dyn_cast<Instruction>(Op0)) {
1486 if (SelectInst *SI = dyn_cast<SelectInst>(Op0I)) {
1487 if (Instruction *R = FoldOpIntoSelect(I, SI))
1488 return R;
1489 } else if (auto *PN = dyn_cast<PHINode>(Op0I)) {
1490 const APInt *Op1Int;
1491 if (match(Op1, m_APInt(Op1Int)) && !Op1Int->isMinValue() &&
1492 (I.getOpcode() == Instruction::URem ||
1493 !Op1Int->isMinSignedValue())) {
1494 // foldOpIntoPhi will speculate instructions to the end of the PHI's
1495 // predecessor blocks, so do this only if we know the srem or urem
1496 // will not fault.
1497 if (Instruction *NV = foldOpIntoPhi(I, PN))
1498 return NV;
1499 }
1500 }
1501
1502 // See if we can fold away this rem instruction.
1503 if (SimplifyDemandedInstructionBits(I))
1504 return &I;
1505 }
1506 }
1507
1508 return nullptr;
1509}
1510
1511Instruction *InstCombiner::visitURem(BinaryOperator &I) {
1512 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1513
1514 if (Value *V = SimplifyVectorOp(I))
1515 return replaceInstUsesWith(I, V);
1516
1517 if (Value *V = SimplifyURemInst(Op0, Op1, SQ.getWithInstruction(&I)))
1518 return replaceInstUsesWith(I, V);
1519
1520 if (Instruction *common = commonIRemTransforms(I))
1521 return common;
1522
1523 if (Instruction *NarrowRem = narrowUDivURem(I, Builder))
1524 return NarrowRem;
1525
1526 // X urem Y -> X and Y-1, where Y is a power of 2,
1527 if (isKnownToBeAPowerOfTwo(Op1, /*OrZero*/ true, 0, &I)) {
1528 Constant *N1 = Constant::getAllOnesValue(I.getType());
1529 Value *Add = Builder.CreateAdd(Op1, N1);
1530 return BinaryOperator::CreateAnd(Op0, Add);
1531 }
1532
1533 // 1 urem X -> zext(X != 1)
1534 if (match(Op0, m_One())) {
1535 Value *Cmp = Builder.CreateICmpNE(Op1, Op0);
1536 Value *Ext = Builder.CreateZExt(Cmp, I.getType());
1537 return replaceInstUsesWith(I, Ext);
1538 }
1539
1540 // X urem C -> X < C ? X : X - C, where C >= signbit.
1541 const APInt *DivisorC;
1542 if (match(Op1, m_APInt(DivisorC)) && DivisorC->isNegative()) {
1543 Value *Cmp = Builder.CreateICmpULT(Op0, Op1);
1544 Value *Sub = Builder.CreateSub(Op0, Op1);
1545 return SelectInst::Create(Cmp, Op0, Sub);
1546 }
1547
1548 return nullptr;
1549}
1550
1551Instruction *InstCombiner::visitSRem(BinaryOperator &I) {
1552 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1553
1554 if (Value *V = SimplifyVectorOp(I))
1555 return replaceInstUsesWith(I, V);
1556
1557 if (Value *V = SimplifySRemInst(Op0, Op1, SQ.getWithInstruction(&I)))
1558 return replaceInstUsesWith(I, V);
1559
1560 // Handle the integer rem common cases
1561 if (Instruction *Common = commonIRemTransforms(I))
1562 return Common;
1563
1564 {
1565 const APInt *Y;
1566 // X % -Y -> X % Y
1567 if (match(Op1, m_APInt(Y)) && Y->isNegative() && !Y->isMinSignedValue()) {
1568 Worklist.AddValue(I.getOperand(1));
1569 I.setOperand(1, ConstantInt::get(I.getType(), -*Y));
1570 return &I;
1571 }
1572 }
1573
1574 // If the sign bits of both operands are zero (i.e. we can prove they are
1575 // unsigned inputs), turn this into a urem.
1576 APInt Mask(APInt::getSignMask(I.getType()->getScalarSizeInBits()));
1577 if (MaskedValueIsZero(Op1, Mask, 0, &I) &&
1578 MaskedValueIsZero(Op0, Mask, 0, &I)) {
1579 // X srem Y -> X urem Y, iff X and Y don't have sign bit set
1580 return BinaryOperator::CreateURem(Op0, Op1, I.getName());
1581 }
1582
1583 // If it's a constant vector, flip any negative values positive.
1584 if (isa<ConstantVector>(Op1) || isa<ConstantDataVector>(Op1)) {
1585 Constant *C = cast<Constant>(Op1);
1586 unsigned VWidth = C->getType()->getVectorNumElements();
1587
1588 bool hasNegative = false;
1589 bool hasMissing = false;
1590 for (unsigned i = 0; i != VWidth; ++i) {
1591 Constant *Elt = C->getAggregateElement(i);
1592 if (!Elt) {
1593 hasMissing = true;
1594 break;
1595 }
1596
1597 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elt))
1598 if (RHS->isNegative())
1599 hasNegative = true;
1600 }
1601
1602 if (hasNegative && !hasMissing) {
1603 SmallVector<Constant *, 16> Elts(VWidth);
1604 for (unsigned i = 0; i != VWidth; ++i) {
1605 Elts[i] = C->getAggregateElement(i); // Handle undef, etc.
1606 if (ConstantInt *RHS = dyn_cast<ConstantInt>(Elts[i])) {
1607 if (RHS->isNegative())
1608 Elts[i] = cast<ConstantInt>(ConstantExpr::getNeg(RHS));
1609 }
1610 }
1611
1612 Constant *NewRHSV = ConstantVector::get(Elts);
1613 if (NewRHSV != C) { // Don't loop on -MININT
1614 Worklist.AddValue(I.getOperand(1));
1615 I.setOperand(1, NewRHSV);
1616 return &I;
1617 }
1618 }
1619 }
1620
1621 return nullptr;
1622}
1623
1624Instruction *InstCombiner::visitFRem(BinaryOperator &I) {
1625 Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
1626
1627 if (Value *V = SimplifyVectorOp(I))
1
Assuming 'V' is null
→
2
←
Taking false branch
→
1628 return replaceInstUsesWith(I, V);
1629
1630 if (Value *V = SimplifyFRemInst(Op0, Op1, I.getFastMathFlags(),
3
←
Assuming 'V' is null
→
4
←
Taking false branch
→
1631 SQ.getWithInstruction(&I)))
1632 return replaceInstUsesWith(I, V);
1633
1634 // Handle cases involving: rem X, (select Cond, Y, Z)
1635 if (simplifyDivRemOfSelectWithZeroOp(I))
5
←
Calling 'InstCombiner::simplifyDivRemOfSelectWithZeroOp'
→
1636 return &I;
1637
1638 return nullptr;
1639}