LLVM 19.0.0git
InstCombineSimplifyDemanded.cpp
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1//===- InstCombineSimplifyDemanded.cpp ------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains logic for simplifying instructions based on information
10// about how they are used.
11//
12//===----------------------------------------------------------------------===//
13
14#include "InstCombineInternal.h"
21
22using namespace llvm;
23using namespace llvm::PatternMatch;
24
25#define DEBUG_TYPE "instcombine"
26
27static cl::opt<bool>
28 VerifyKnownBits("instcombine-verify-known-bits",
29 cl::desc("Verify that computeKnownBits() and "
30 "SimplifyDemandedBits() are consistent"),
31 cl::Hidden, cl::init(false));
32
33/// Check to see if the specified operand of the specified instruction is a
34/// constant integer. If so, check to see if there are any bits set in the
35/// constant that are not demanded. If so, shrink the constant and return true.
36static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
37 const APInt &Demanded) {
38 assert(I && "No instruction?");
39 assert(OpNo < I->getNumOperands() && "Operand index too large");
40
41 // The operand must be a constant integer or splat integer.
42 Value *Op = I->getOperand(OpNo);
43 const APInt *C;
44 if (!match(Op, m_APInt(C)))
45 return false;
46
47 // If there are no bits set that aren't demanded, nothing to do.
48 if (C->isSubsetOf(Demanded))
49 return false;
50
51 // This instruction is producing bits that are not demanded. Shrink the RHS.
52 I->setOperand(OpNo, ConstantInt::get(Op->getType(), *C & Demanded));
53
54 return true;
55}
56
57/// Returns the bitwidth of the given scalar or pointer type. For vector types,
58/// returns the element type's bitwidth.
59static unsigned getBitWidth(Type *Ty, const DataLayout &DL) {
60 if (unsigned BitWidth = Ty->getScalarSizeInBits())
61 return BitWidth;
62
63 return DL.getPointerTypeSizeInBits(Ty);
64}
65
66/// Inst is an integer instruction that SimplifyDemandedBits knows about. See if
67/// the instruction has any properties that allow us to simplify its operands.
69 KnownBits &Known) {
70 APInt DemandedMask(APInt::getAllOnes(Known.getBitWidth()));
71 Value *V = SimplifyDemandedUseBits(&Inst, DemandedMask, Known,
72 0, &Inst);
73 if (!V) return false;
74 if (V == &Inst) return true;
75 replaceInstUsesWith(Inst, V);
76 return true;
77}
78
79/// Inst is an integer instruction that SimplifyDemandedBits knows about. See if
80/// the instruction has any properties that allow us to simplify its operands.
82 KnownBits Known(getBitWidth(Inst.getType(), DL));
83 return SimplifyDemandedInstructionBits(Inst, Known);
84}
85
86/// This form of SimplifyDemandedBits simplifies the specified instruction
87/// operand if possible, updating it in place. It returns true if it made any
88/// change and false otherwise.
90 const APInt &DemandedMask,
91 KnownBits &Known, unsigned Depth) {
92 Use &U = I->getOperandUse(OpNo);
93 Value *NewVal = SimplifyDemandedUseBits(U.get(), DemandedMask, Known,
94 Depth, I);
95 if (!NewVal) return false;
96 if (Instruction* OpInst = dyn_cast<Instruction>(U))
97 salvageDebugInfo(*OpInst);
98
99 replaceUse(U, NewVal);
100 return true;
101}
102
103/// This function attempts to replace V with a simpler value based on the
104/// demanded bits. When this function is called, it is known that only the bits
105/// set in DemandedMask of the result of V are ever used downstream.
106/// Consequently, depending on the mask and V, it may be possible to replace V
107/// with a constant or one of its operands. In such cases, this function does
108/// the replacement and returns true. In all other cases, it returns false after
109/// analyzing the expression and setting KnownOne and known to be one in the
110/// expression. Known.Zero contains all the bits that are known to be zero in
111/// the expression. These are provided to potentially allow the caller (which
112/// might recursively be SimplifyDemandedBits itself) to simplify the
113/// expression.
114/// Known.One and Known.Zero always follow the invariant that:
115/// Known.One & Known.Zero == 0.
116/// That is, a bit can't be both 1 and 0. The bits in Known.One and Known.Zero
117/// are accurate even for bits not in DemandedMask. Note
118/// also that the bitwidth of V, DemandedMask, Known.Zero and Known.One must all
119/// be the same.
120///
121/// This returns null if it did not change anything and it permits no
122/// simplification. This returns V itself if it did some simplification of V's
123/// operands based on the information about what bits are demanded. This returns
124/// some other non-null value if it found out that V is equal to another value
125/// in the context where the specified bits are demanded, but not for all users.
127 KnownBits &Known,
128 unsigned Depth,
129 Instruction *CxtI) {
130 assert(V != nullptr && "Null pointer of Value???");
131 assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
132 uint32_t BitWidth = DemandedMask.getBitWidth();
133 Type *VTy = V->getType();
134 assert(
135 (!VTy->isIntOrIntVectorTy() || VTy->getScalarSizeInBits() == BitWidth) &&
136 Known.getBitWidth() == BitWidth &&
137 "Value *V, DemandedMask and Known must have same BitWidth");
138
139 if (isa<Constant>(V)) {
140 computeKnownBits(V, Known, Depth, CxtI);
141 return nullptr;
142 }
143
144 Known.resetAll();
145 if (DemandedMask.isZero()) // Not demanding any bits from V.
146 return UndefValue::get(VTy);
147
149 return nullptr;
150
151 Instruction *I = dyn_cast<Instruction>(V);
152 if (!I) {
153 computeKnownBits(V, Known, Depth, CxtI);
154 return nullptr; // Only analyze instructions.
155 }
156
157 // If there are multiple uses of this value and we aren't at the root, then
158 // we can't do any simplifications of the operands, because DemandedMask
159 // only reflects the bits demanded by *one* of the users.
160 if (Depth != 0 && !I->hasOneUse())
161 return SimplifyMultipleUseDemandedBits(I, DemandedMask, Known, Depth, CxtI);
162
163 KnownBits LHSKnown(BitWidth), RHSKnown(BitWidth);
164 // If this is the root being simplified, allow it to have multiple uses,
165 // just set the DemandedMask to all bits so that we can try to simplify the
166 // operands. This allows visitTruncInst (for example) to simplify the
167 // operand of a trunc without duplicating all the logic below.
168 if (Depth == 0 && !V->hasOneUse())
169 DemandedMask.setAllBits();
170
171 // Update flags after simplifying an operand based on the fact that some high
172 // order bits are not demanded.
173 auto disableWrapFlagsBasedOnUnusedHighBits = [](Instruction *I,
174 unsigned NLZ) {
175 if (NLZ > 0) {
176 // Disable the nsw and nuw flags here: We can no longer guarantee that
177 // we won't wrap after simplification. Removing the nsw/nuw flags is
178 // legal here because the top bit is not demanded.
179 I->setHasNoSignedWrap(false);
180 I->setHasNoUnsignedWrap(false);
181 }
182 return I;
183 };
184
185 // If the high-bits of an ADD/SUB/MUL are not demanded, then we do not care
186 // about the high bits of the operands.
187 auto simplifyOperandsBasedOnUnusedHighBits = [&](APInt &DemandedFromOps) {
188 unsigned NLZ = DemandedMask.countl_zero();
189 // Right fill the mask of bits for the operands to demand the most
190 // significant bit and all those below it.
191 DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
192 if (ShrinkDemandedConstant(I, 0, DemandedFromOps) ||
193 SimplifyDemandedBits(I, 0, DemandedFromOps, LHSKnown, Depth + 1) ||
194 ShrinkDemandedConstant(I, 1, DemandedFromOps) ||
195 SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1)) {
196 disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
197 return true;
198 }
199 return false;
200 };
201
202 switch (I->getOpcode()) {
203 default:
204 computeKnownBits(I, Known, Depth, CxtI);
205 break;
206 case Instruction::And: {
207 // If either the LHS or the RHS are Zero, the result is zero.
208 if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1) ||
209 SimplifyDemandedBits(I, 0, DemandedMask & ~RHSKnown.Zero, LHSKnown,
210 Depth + 1))
211 return I;
212 assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?");
213 assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?");
214
215 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
217
218 // If the client is only demanding bits that we know, return the known
219 // constant.
220 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
221 return Constant::getIntegerValue(VTy, Known.One);
222
223 // If all of the demanded bits are known 1 on one side, return the other.
224 // These bits cannot contribute to the result of the 'and'.
225 if (DemandedMask.isSubsetOf(LHSKnown.Zero | RHSKnown.One))
226 return I->getOperand(0);
227 if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.One))
228 return I->getOperand(1);
229
230 // If the RHS is a constant, see if we can simplify it.
231 if (ShrinkDemandedConstant(I, 1, DemandedMask & ~LHSKnown.Zero))
232 return I;
233
234 break;
235 }
236 case Instruction::Or: {
237 // If either the LHS or the RHS are One, the result is One.
238 if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1) ||
239 SimplifyDemandedBits(I, 0, DemandedMask & ~RHSKnown.One, LHSKnown,
240 Depth + 1)) {
241 // Disjoint flag may not longer hold.
242 I->dropPoisonGeneratingFlags();
243 return I;
244 }
245 assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?");
246 assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?");
247
248 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
250
251 // If the client is only demanding bits that we know, return the known
252 // constant.
253 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
254 return Constant::getIntegerValue(VTy, Known.One);
255
256 // If all of the demanded bits are known zero on one side, return the other.
257 // These bits cannot contribute to the result of the 'or'.
258 if (DemandedMask.isSubsetOf(LHSKnown.One | RHSKnown.Zero))
259 return I->getOperand(0);
260 if (DemandedMask.isSubsetOf(RHSKnown.One | LHSKnown.Zero))
261 return I->getOperand(1);
262
263 // If the RHS is a constant, see if we can simplify it.
264 if (ShrinkDemandedConstant(I, 1, DemandedMask))
265 return I;
266
267 // Infer disjoint flag if no common bits are set.
268 if (!cast<PossiblyDisjointInst>(I)->isDisjoint()) {
269 WithCache<const Value *> LHSCache(I->getOperand(0), LHSKnown),
270 RHSCache(I->getOperand(1), RHSKnown);
271 if (haveNoCommonBitsSet(LHSCache, RHSCache, SQ.getWithInstruction(I))) {
272 cast<PossiblyDisjointInst>(I)->setIsDisjoint(true);
273 return I;
274 }
275 }
276
277 break;
278 }
279 case Instruction::Xor: {
280 if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1) ||
281 SimplifyDemandedBits(I, 0, DemandedMask, LHSKnown, Depth + 1))
282 return I;
283 Value *LHS, *RHS;
284 if (DemandedMask == 1 &&
285 match(I->getOperand(0), m_Intrinsic<Intrinsic::ctpop>(m_Value(LHS))) &&
286 match(I->getOperand(1), m_Intrinsic<Intrinsic::ctpop>(m_Value(RHS)))) {
287 // (ctpop(X) ^ ctpop(Y)) & 1 --> ctpop(X^Y) & 1
290 auto *Xor = Builder.CreateXor(LHS, RHS);
291 return Builder.CreateUnaryIntrinsic(Intrinsic::ctpop, Xor);
292 }
293
294 assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?");
295 assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?");
296
297 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
299
300 // If the client is only demanding bits that we know, return the known
301 // constant.
302 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
303 return Constant::getIntegerValue(VTy, Known.One);
304
305 // If all of the demanded bits are known zero on one side, return the other.
306 // These bits cannot contribute to the result of the 'xor'.
307 if (DemandedMask.isSubsetOf(RHSKnown.Zero))
308 return I->getOperand(0);
309 if (DemandedMask.isSubsetOf(LHSKnown.Zero))
310 return I->getOperand(1);
311
312 // If all of the demanded bits are known to be zero on one side or the
313 // other, turn this into an *inclusive* or.
314 // e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
315 if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.Zero)) {
316 Instruction *Or =
317 BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1));
318 if (DemandedMask.isAllOnes())
319 cast<PossiblyDisjointInst>(Or)->setIsDisjoint(true);
320 Or->takeName(I);
321 return InsertNewInstWith(Or, I->getIterator());
322 }
323
324 // If all of the demanded bits on one side are known, and all of the set
325 // bits on that side are also known to be set on the other side, turn this
326 // into an AND, as we know the bits will be cleared.
327 // e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
328 if (DemandedMask.isSubsetOf(RHSKnown.Zero|RHSKnown.One) &&
329 RHSKnown.One.isSubsetOf(LHSKnown.One)) {
331 ~RHSKnown.One & DemandedMask);
332 Instruction *And = BinaryOperator::CreateAnd(I->getOperand(0), AndC);
333 return InsertNewInstWith(And, I->getIterator());
334 }
335
336 // If the RHS is a constant, see if we can change it. Don't alter a -1
337 // constant because that's a canonical 'not' op, and that is better for
338 // combining, SCEV, and codegen.
339 const APInt *C;
340 if (match(I->getOperand(1), m_APInt(C)) && !C->isAllOnes()) {
341 if ((*C | ~DemandedMask).isAllOnes()) {
342 // Force bits to 1 to create a 'not' op.
343 I->setOperand(1, ConstantInt::getAllOnesValue(VTy));
344 return I;
345 }
346 // If we can't turn this into a 'not', try to shrink the constant.
347 if (ShrinkDemandedConstant(I, 1, DemandedMask))
348 return I;
349 }
350
351 // If our LHS is an 'and' and if it has one use, and if any of the bits we
352 // are flipping are known to be set, then the xor is just resetting those
353 // bits to zero. We can just knock out bits from the 'and' and the 'xor',
354 // simplifying both of them.
355 if (Instruction *LHSInst = dyn_cast<Instruction>(I->getOperand(0))) {
356 ConstantInt *AndRHS, *XorRHS;
357 if (LHSInst->getOpcode() == Instruction::And && LHSInst->hasOneUse() &&
358 match(I->getOperand(1), m_ConstantInt(XorRHS)) &&
359 match(LHSInst->getOperand(1), m_ConstantInt(AndRHS)) &&
360 (LHSKnown.One & RHSKnown.One & DemandedMask) != 0) {
361 APInt NewMask = ~(LHSKnown.One & RHSKnown.One & DemandedMask);
362
363 Constant *AndC = ConstantInt::get(VTy, NewMask & AndRHS->getValue());
364 Instruction *NewAnd = BinaryOperator::CreateAnd(I->getOperand(0), AndC);
365 InsertNewInstWith(NewAnd, I->getIterator());
366
367 Constant *XorC = ConstantInt::get(VTy, NewMask & XorRHS->getValue());
368 Instruction *NewXor = BinaryOperator::CreateXor(NewAnd, XorC);
369 return InsertNewInstWith(NewXor, I->getIterator());
370 }
371 }
372 break;
373 }
374 case Instruction::Select: {
375 if (SimplifyDemandedBits(I, 2, DemandedMask, RHSKnown, Depth + 1) ||
376 SimplifyDemandedBits(I, 1, DemandedMask, LHSKnown, Depth + 1))
377 return I;
378 assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?");
379 assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?");
380
381 // If the operands are constants, see if we can simplify them.
382 // This is similar to ShrinkDemandedConstant, but for a select we want to
383 // try to keep the selected constants the same as icmp value constants, if
384 // we can. This helps not break apart (or helps put back together)
385 // canonical patterns like min and max.
386 auto CanonicalizeSelectConstant = [](Instruction *I, unsigned OpNo,
387 const APInt &DemandedMask) {
388 const APInt *SelC;
389 if (!match(I->getOperand(OpNo), m_APInt(SelC)))
390 return false;
391
392 // Get the constant out of the ICmp, if there is one.
393 // Only try this when exactly 1 operand is a constant (if both operands
394 // are constant, the icmp should eventually simplify). Otherwise, we may
395 // invert the transform that reduces set bits and infinite-loop.
396 Value *X;
397 const APInt *CmpC;
399 if (!match(I->getOperand(0), m_ICmp(Pred, m_Value(X), m_APInt(CmpC))) ||
400 isa<Constant>(X) || CmpC->getBitWidth() != SelC->getBitWidth())
401 return ShrinkDemandedConstant(I, OpNo, DemandedMask);
402
403 // If the constant is already the same as the ICmp, leave it as-is.
404 if (*CmpC == *SelC)
405 return false;
406 // If the constants are not already the same, but can be with the demand
407 // mask, use the constant value from the ICmp.
408 if ((*CmpC & DemandedMask) == (*SelC & DemandedMask)) {
409 I->setOperand(OpNo, ConstantInt::get(I->getType(), *CmpC));
410 return true;
411 }
412 return ShrinkDemandedConstant(I, OpNo, DemandedMask);
413 };
414 if (CanonicalizeSelectConstant(I, 1, DemandedMask) ||
415 CanonicalizeSelectConstant(I, 2, DemandedMask))
416 return I;
417
418 // Only known if known in both the LHS and RHS.
419 Known = LHSKnown.intersectWith(RHSKnown);
420 break;
421 }
422 case Instruction::Trunc: {
423 // If we do not demand the high bits of a right-shifted and truncated value,
424 // then we may be able to truncate it before the shift.
425 Value *X;
426 const APInt *C;
427 if (match(I->getOperand(0), m_OneUse(m_LShr(m_Value(X), m_APInt(C))))) {
428 // The shift amount must be valid (not poison) in the narrow type, and
429 // it must not be greater than the high bits demanded of the result.
430 if (C->ult(VTy->getScalarSizeInBits()) &&
431 C->ule(DemandedMask.countl_zero())) {
432 // trunc (lshr X, C) --> lshr (trunc X), C
435 Value *Trunc = Builder.CreateTrunc(X, VTy);
436 return Builder.CreateLShr(Trunc, C->getZExtValue());
437 }
438 }
439 }
440 [[fallthrough]];
441 case Instruction::ZExt: {
442 unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
443
444 APInt InputDemandedMask = DemandedMask.zextOrTrunc(SrcBitWidth);
445 KnownBits InputKnown(SrcBitWidth);
446 if (SimplifyDemandedBits(I, 0, InputDemandedMask, InputKnown, Depth + 1)) {
447 // For zext nneg, we may have dropped the instruction which made the
448 // input non-negative.
449 I->dropPoisonGeneratingFlags();
450 return I;
451 }
452 assert(InputKnown.getBitWidth() == SrcBitWidth && "Src width changed?");
453 if (I->getOpcode() == Instruction::ZExt && I->hasNonNeg() &&
454 !InputKnown.isNegative())
455 InputKnown.makeNonNegative();
456 Known = InputKnown.zextOrTrunc(BitWidth);
457
458 assert(!Known.hasConflict() && "Bits known to be one AND zero?");
459 break;
460 }
461 case Instruction::SExt: {
462 // Compute the bits in the result that are not present in the input.
463 unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
464
465 APInt InputDemandedBits = DemandedMask.trunc(SrcBitWidth);
466
467 // If any of the sign extended bits are demanded, we know that the sign
468 // bit is demanded.
469 if (DemandedMask.getActiveBits() > SrcBitWidth)
470 InputDemandedBits.setBit(SrcBitWidth-1);
471
472 KnownBits InputKnown(SrcBitWidth);
473 if (SimplifyDemandedBits(I, 0, InputDemandedBits, InputKnown, Depth + 1))
474 return I;
475
476 // If the input sign bit is known zero, or if the NewBits are not demanded
477 // convert this into a zero extension.
478 if (InputKnown.isNonNegative() ||
479 DemandedMask.getActiveBits() <= SrcBitWidth) {
480 // Convert to ZExt cast.
481 CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy);
482 NewCast->takeName(I);
483 return InsertNewInstWith(NewCast, I->getIterator());
484 }
485
486 // If the sign bit of the input is known set or clear, then we know the
487 // top bits of the result.
488 Known = InputKnown.sext(BitWidth);
489 assert(!Known.hasConflict() && "Bits known to be one AND zero?");
490 break;
491 }
492 case Instruction::Add: {
493 if ((DemandedMask & 1) == 0) {
494 // If we do not need the low bit, try to convert bool math to logic:
495 // add iN (zext i1 X), (sext i1 Y) --> sext (~X & Y) to iN
496 Value *X, *Y;
498 m_OneUse(m_SExt(m_Value(Y))))) &&
499 X->getType()->isIntOrIntVectorTy(1) && X->getType() == Y->getType()) {
500 // Truth table for inputs and output signbits:
501 // X:0 | X:1
502 // ----------
503 // Y:0 | 0 | 0 |
504 // Y:1 | -1 | 0 |
505 // ----------
509 return Builder.CreateSExt(AndNot, VTy);
510 }
511
512 // add iN (sext i1 X), (sext i1 Y) --> sext (X | Y) to iN
513 // TODO: Relax the one-use checks because we are removing an instruction?
515 m_OneUse(m_SExt(m_Value(Y))))) &&
516 X->getType()->isIntOrIntVectorTy(1) && X->getType() == Y->getType()) {
517 // Truth table for inputs and output signbits:
518 // X:0 | X:1
519 // -----------
520 // Y:0 | -1 | -1 |
521 // Y:1 | -1 | 0 |
522 // -----------
525 Value *Or = Builder.CreateOr(X, Y);
526 return Builder.CreateSExt(Or, VTy);
527 }
528 }
529
530 // Right fill the mask of bits for the operands to demand the most
531 // significant bit and all those below it.
532 unsigned NLZ = DemandedMask.countl_zero();
533 APInt DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
534 if (ShrinkDemandedConstant(I, 1, DemandedFromOps) ||
535 SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1))
536 return disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
537
538 // If low order bits are not demanded and known to be zero in one operand,
539 // then we don't need to demand them from the other operand, since they
540 // can't cause overflow into any bits that are demanded in the result.
541 unsigned NTZ = (~DemandedMask & RHSKnown.Zero).countr_one();
542 APInt DemandedFromLHS = DemandedFromOps;
543 DemandedFromLHS.clearLowBits(NTZ);
544 if (ShrinkDemandedConstant(I, 0, DemandedFromLHS) ||
545 SimplifyDemandedBits(I, 0, DemandedFromLHS, LHSKnown, Depth + 1))
546 return disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
547
548 // If we are known to be adding zeros to every bit below
549 // the highest demanded bit, we just return the other side.
550 if (DemandedFromOps.isSubsetOf(RHSKnown.Zero))
551 return I->getOperand(0);
552 if (DemandedFromOps.isSubsetOf(LHSKnown.Zero))
553 return I->getOperand(1);
554
555 // (add X, C) --> (xor X, C) IFF C is equal to the top bit of the DemandMask
556 {
557 const APInt *C;
558 if (match(I->getOperand(1), m_APInt(C)) &&
559 C->isOneBitSet(DemandedMask.getActiveBits() - 1)) {
562 return Builder.CreateXor(I->getOperand(0), ConstantInt::get(VTy, *C));
563 }
564 }
565
566 // Otherwise just compute the known bits of the result.
567 bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
568 bool NUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
569 Known = KnownBits::computeForAddSub(true, NSW, NUW, LHSKnown, RHSKnown);
570 break;
571 }
572 case Instruction::Sub: {
573 // Right fill the mask of bits for the operands to demand the most
574 // significant bit and all those below it.
575 unsigned NLZ = DemandedMask.countl_zero();
576 APInt DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
577 if (ShrinkDemandedConstant(I, 1, DemandedFromOps) ||
578 SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1))
579 return disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
580
581 // If low order bits are not demanded and are known to be zero in RHS,
582 // then we don't need to demand them from LHS, since they can't cause a
583 // borrow from any bits that are demanded in the result.
584 unsigned NTZ = (~DemandedMask & RHSKnown.Zero).countr_one();
585 APInt DemandedFromLHS = DemandedFromOps;
586 DemandedFromLHS.clearLowBits(NTZ);
587 if (ShrinkDemandedConstant(I, 0, DemandedFromLHS) ||
588 SimplifyDemandedBits(I, 0, DemandedFromLHS, LHSKnown, Depth + 1))
589 return disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
590
591 // If we are known to be subtracting zeros from every bit below
592 // the highest demanded bit, we just return the other side.
593 if (DemandedFromOps.isSubsetOf(RHSKnown.Zero))
594 return I->getOperand(0);
595 // We can't do this with the LHS for subtraction, unless we are only
596 // demanding the LSB.
597 if (DemandedFromOps.isOne() && DemandedFromOps.isSubsetOf(LHSKnown.Zero))
598 return I->getOperand(1);
599
600 // Otherwise just compute the known bits of the result.
601 bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
602 bool NUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
603 Known = KnownBits::computeForAddSub(false, NSW, NUW, LHSKnown, RHSKnown);
604 break;
605 }
606 case Instruction::Mul: {
607 APInt DemandedFromOps;
608 if (simplifyOperandsBasedOnUnusedHighBits(DemandedFromOps))
609 return I;
610
611 if (DemandedMask.isPowerOf2()) {
612 // The LSB of X*Y is set only if (X & 1) == 1 and (Y & 1) == 1.
613 // If we demand exactly one bit N and we have "X * (C' << N)" where C' is
614 // odd (has LSB set), then the left-shifted low bit of X is the answer.
615 unsigned CTZ = DemandedMask.countr_zero();
616 const APInt *C;
617 if (match(I->getOperand(1), m_APInt(C)) && C->countr_zero() == CTZ) {
618 Constant *ShiftC = ConstantInt::get(VTy, CTZ);
619 Instruction *Shl = BinaryOperator::CreateShl(I->getOperand(0), ShiftC);
620 return InsertNewInstWith(Shl, I->getIterator());
621 }
622 }
623 // For a squared value "X * X", the bottom 2 bits are 0 and X[0] because:
624 // X * X is odd iff X is odd.
625 // 'Quadratic Reciprocity': X * X -> 0 for bit[1]
626 if (I->getOperand(0) == I->getOperand(1) && DemandedMask.ult(4)) {
627 Constant *One = ConstantInt::get(VTy, 1);
628 Instruction *And1 = BinaryOperator::CreateAnd(I->getOperand(0), One);
629 return InsertNewInstWith(And1, I->getIterator());
630 }
631
632 computeKnownBits(I, Known, Depth, CxtI);
633 break;
634 }
635 case Instruction::Shl: {
636 const APInt *SA;
637 if (match(I->getOperand(1), m_APInt(SA))) {
638 const APInt *ShrAmt;
639 if (match(I->getOperand(0), m_Shr(m_Value(), m_APInt(ShrAmt))))
640 if (Instruction *Shr = dyn_cast<Instruction>(I->getOperand(0)))
641 if (Value *R = simplifyShrShlDemandedBits(Shr, *ShrAmt, I, *SA,
642 DemandedMask, Known))
643 return R;
644
645 // Do not simplify if shl is part of funnel-shift pattern
646 if (I->hasOneUse()) {
647 auto *Inst = dyn_cast<Instruction>(I->user_back());
648 if (Inst && Inst->getOpcode() == BinaryOperator::Or) {
649 if (auto Opt = convertOrOfShiftsToFunnelShift(*Inst)) {
650 auto [IID, FShiftArgs] = *Opt;
651 if ((IID == Intrinsic::fshl || IID == Intrinsic::fshr) &&
652 FShiftArgs[0] == FShiftArgs[1])
653 return nullptr;
654 }
655 }
656 }
657
658 // TODO: If we only want bits that already match the signbit then we don't
659 // need to shift.
660
661 // If we can pre-shift a right-shifted constant to the left without
662 // losing any high bits amd we don't demand the low bits, then eliminate
663 // the left-shift:
664 // (C >> X) << LeftShiftAmtC --> (C << RightShiftAmtC) >> X
665 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
666 Value *X;
667 Constant *C;
668 if (DemandedMask.countr_zero() >= ShiftAmt &&
669 match(I->getOperand(0), m_LShr(m_ImmConstant(C), m_Value(X)))) {
670 Constant *LeftShiftAmtC = ConstantInt::get(VTy, ShiftAmt);
671 Constant *NewC = ConstantFoldBinaryOpOperands(Instruction::Shl, C,
672 LeftShiftAmtC, DL);
673 if (ConstantFoldBinaryOpOperands(Instruction::LShr, NewC, LeftShiftAmtC,
674 DL) == C) {
675 Instruction *Lshr = BinaryOperator::CreateLShr(NewC, X);
676 return InsertNewInstWith(Lshr, I->getIterator());
677 }
678 }
679
680 APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt));
681
682 // If the shift is NUW/NSW, then it does demand the high bits.
683 ShlOperator *IOp = cast<ShlOperator>(I);
684 if (IOp->hasNoSignedWrap())
685 DemandedMaskIn.setHighBits(ShiftAmt+1);
686 else if (IOp->hasNoUnsignedWrap())
687 DemandedMaskIn.setHighBits(ShiftAmt);
688
689 if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1))
690 return I;
691 assert(!Known.hasConflict() && "Bits known to be one AND zero?");
692
693 Known = KnownBits::shl(Known,
695 /* NUW */ IOp->hasNoUnsignedWrap(),
696 /* NSW */ IOp->hasNoSignedWrap());
697 } else {
698 // This is a variable shift, so we can't shift the demand mask by a known
699 // amount. But if we are not demanding high bits, then we are not
700 // demanding those bits from the pre-shifted operand either.
701 if (unsigned CTLZ = DemandedMask.countl_zero()) {
702 APInt DemandedFromOp(APInt::getLowBitsSet(BitWidth, BitWidth - CTLZ));
703 if (SimplifyDemandedBits(I, 0, DemandedFromOp, Known, Depth + 1)) {
704 // We can't guarantee that nsw/nuw hold after simplifying the operand.
705 I->dropPoisonGeneratingFlags();
706 return I;
707 }
708 }
709 computeKnownBits(I, Known, Depth, CxtI);
710 }
711 break;
712 }
713 case Instruction::LShr: {
714 const APInt *SA;
715 if (match(I->getOperand(1), m_APInt(SA))) {
716 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
717
718 // Do not simplify if lshr is part of funnel-shift pattern
719 if (I->hasOneUse()) {
720 auto *Inst = dyn_cast<Instruction>(I->user_back());
721 if (Inst && Inst->getOpcode() == BinaryOperator::Or) {
722 if (auto Opt = convertOrOfShiftsToFunnelShift(*Inst)) {
723 auto [IID, FShiftArgs] = *Opt;
724 if ((IID == Intrinsic::fshl || IID == Intrinsic::fshr) &&
725 FShiftArgs[0] == FShiftArgs[1])
726 return nullptr;
727 }
728 }
729 }
730
731 // If we are just demanding the shifted sign bit and below, then this can
732 // be treated as an ASHR in disguise.
733 if (DemandedMask.countl_zero() >= ShiftAmt) {
734 // If we only want bits that already match the signbit then we don't
735 // need to shift.
736 unsigned NumHiDemandedBits = BitWidth - DemandedMask.countr_zero();
737 unsigned SignBits =
738 ComputeNumSignBits(I->getOperand(0), Depth + 1, CxtI);
739 if (SignBits >= NumHiDemandedBits)
740 return I->getOperand(0);
741
742 // If we can pre-shift a left-shifted constant to the right without
743 // losing any low bits (we already know we don't demand the high bits),
744 // then eliminate the right-shift:
745 // (C << X) >> RightShiftAmtC --> (C >> RightShiftAmtC) << X
746 Value *X;
747 Constant *C;
748 if (match(I->getOperand(0), m_Shl(m_ImmConstant(C), m_Value(X)))) {
749 Constant *RightShiftAmtC = ConstantInt::get(VTy, ShiftAmt);
750 Constant *NewC = ConstantFoldBinaryOpOperands(Instruction::LShr, C,
751 RightShiftAmtC, DL);
752 if (ConstantFoldBinaryOpOperands(Instruction::Shl, NewC,
753 RightShiftAmtC, DL) == C) {
754 Instruction *Shl = BinaryOperator::CreateShl(NewC, X);
755 return InsertNewInstWith(Shl, I->getIterator());
756 }
757 }
758 }
759
760 // Unsigned shift right.
761 APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
762 if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1)) {
763 // exact flag may not longer hold.
764 I->dropPoisonGeneratingFlags();
765 return I;
766 }
767 assert(!Known.hasConflict() && "Bits known to be one AND zero?");
768 Known.Zero.lshrInPlace(ShiftAmt);
769 Known.One.lshrInPlace(ShiftAmt);
770 if (ShiftAmt)
771 Known.Zero.setHighBits(ShiftAmt); // high bits known zero.
772 } else {
773 computeKnownBits(I, Known, Depth, CxtI);
774 }
775 break;
776 }
777 case Instruction::AShr: {
778 unsigned SignBits = ComputeNumSignBits(I->getOperand(0), Depth + 1, CxtI);
779
780 // If we only want bits that already match the signbit then we don't need
781 // to shift.
782 unsigned NumHiDemandedBits = BitWidth - DemandedMask.countr_zero();
783 if (SignBits >= NumHiDemandedBits)
784 return I->getOperand(0);
785
786 // If this is an arithmetic shift right and only the low-bit is set, we can
787 // always convert this into a logical shr, even if the shift amount is
788 // variable. The low bit of the shift cannot be an input sign bit unless
789 // the shift amount is >= the size of the datatype, which is undefined.
790 if (DemandedMask.isOne()) {
791 // Perform the logical shift right.
792 Instruction *NewVal = BinaryOperator::CreateLShr(
793 I->getOperand(0), I->getOperand(1), I->getName());
794 return InsertNewInstWith(NewVal, I->getIterator());
795 }
796
797 const APInt *SA;
798 if (match(I->getOperand(1), m_APInt(SA))) {
799 uint32_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
800
801 // Signed shift right.
802 APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
803 // If any of the high bits are demanded, we should set the sign bit as
804 // demanded.
805 if (DemandedMask.countl_zero() <= ShiftAmt)
806 DemandedMaskIn.setSignBit();
807
808 if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1)) {
809 // exact flag may not longer hold.
810 I->dropPoisonGeneratingFlags();
811 return I;
812 }
813
814 assert(!Known.hasConflict() && "Bits known to be one AND zero?");
815 // Compute the new bits that are at the top now plus sign bits.
817 BitWidth, std::min(SignBits + ShiftAmt - 1, BitWidth)));
818 Known.Zero.lshrInPlace(ShiftAmt);
819 Known.One.lshrInPlace(ShiftAmt);
820
821 // If the input sign bit is known to be zero, or if none of the top bits
822 // are demanded, turn this into an unsigned shift right.
823 assert(BitWidth > ShiftAmt && "Shift amount not saturated?");
824 if (Known.Zero[BitWidth-ShiftAmt-1] ||
825 !DemandedMask.intersects(HighBits)) {
826 BinaryOperator *LShr = BinaryOperator::CreateLShr(I->getOperand(0),
827 I->getOperand(1));
828 LShr->setIsExact(cast<BinaryOperator>(I)->isExact());
829 LShr->takeName(I);
830 return InsertNewInstWith(LShr, I->getIterator());
831 } else if (Known.One[BitWidth-ShiftAmt-1]) { // New bits are known one.
832 Known.One |= HighBits;
833 // SignBits may be out-of-sync with Known.countMinSignBits(). Mask out
834 // high bits of Known.Zero to avoid conflicts.
835 Known.Zero &= ~HighBits;
836 }
837 } else {
838 computeKnownBits(I, Known, Depth, CxtI);
839 }
840 break;
841 }
842 case Instruction::UDiv: {
843 // UDiv doesn't demand low bits that are zero in the divisor.
844 const APInt *SA;
845 if (match(I->getOperand(1), m_APInt(SA))) {
846 // TODO: Take the demanded mask of the result into account.
847 unsigned RHSTrailingZeros = SA->countr_zero();
848 APInt DemandedMaskIn =
849 APInt::getHighBitsSet(BitWidth, BitWidth - RHSTrailingZeros);
850 if (SimplifyDemandedBits(I, 0, DemandedMaskIn, LHSKnown, Depth + 1)) {
851 // We can't guarantee that "exact" is still true after changing the
852 // the dividend.
853 I->dropPoisonGeneratingFlags();
854 return I;
855 }
856
857 Known = KnownBits::udiv(LHSKnown, KnownBits::makeConstant(*SA),
858 cast<BinaryOperator>(I)->isExact());
859 } else {
860 computeKnownBits(I, Known, Depth, CxtI);
861 }
862 break;
863 }
864 case Instruction::SRem: {
865 const APInt *Rem;
866 if (match(I->getOperand(1), m_APInt(Rem))) {
867 // X % -1 demands all the bits because we don't want to introduce
868 // INT_MIN % -1 (== undef) by accident.
869 if (Rem->isAllOnes())
870 break;
871 APInt RA = Rem->abs();
872 if (RA.isPowerOf2()) {
873 if (DemandedMask.ult(RA)) // srem won't affect demanded bits
874 return I->getOperand(0);
875
876 APInt LowBits = RA - 1;
877 APInt Mask2 = LowBits | APInt::getSignMask(BitWidth);
878 if (SimplifyDemandedBits(I, 0, Mask2, LHSKnown, Depth + 1))
879 return I;
880
881 // The low bits of LHS are unchanged by the srem.
882 Known.Zero = LHSKnown.Zero & LowBits;
883 Known.One = LHSKnown.One & LowBits;
884
885 // If LHS is non-negative or has all low bits zero, then the upper bits
886 // are all zero.
887 if (LHSKnown.isNonNegative() || LowBits.isSubsetOf(LHSKnown.Zero))
888 Known.Zero |= ~LowBits;
889
890 // If LHS is negative and not all low bits are zero, then the upper bits
891 // are all one.
892 if (LHSKnown.isNegative() && LowBits.intersects(LHSKnown.One))
893 Known.One |= ~LowBits;
894
895 assert(!Known.hasConflict() && "Bits known to be one AND zero?");
896 break;
897 }
898 }
899
900 computeKnownBits(I, Known, Depth, CxtI);
901 break;
902 }
903 case Instruction::URem: {
905 if (SimplifyDemandedBits(I, 0, AllOnes, LHSKnown, Depth + 1) ||
906 SimplifyDemandedBits(I, 1, AllOnes, RHSKnown, Depth + 1))
907 return I;
908
909 Known = KnownBits::urem(LHSKnown, RHSKnown);
910 break;
911 }
912 case Instruction::Call: {
913 bool KnownBitsComputed = false;
914 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
915 switch (II->getIntrinsicID()) {
916 case Intrinsic::abs: {
917 if (DemandedMask == 1)
918 return II->getArgOperand(0);
919 break;
920 }
921 case Intrinsic::ctpop: {
922 // Checking if the number of clear bits is odd (parity)? If the type has
923 // an even number of bits, that's the same as checking if the number of
924 // set bits is odd, so we can eliminate the 'not' op.
925 Value *X;
926 if (DemandedMask == 1 && VTy->getScalarSizeInBits() % 2 == 0 &&
927 match(II->getArgOperand(0), m_Not(m_Value(X)))) {
929 II->getModule(), Intrinsic::ctpop, VTy);
930 return InsertNewInstWith(CallInst::Create(Ctpop, {X}), I->getIterator());
931 }
932 break;
933 }
934 case Intrinsic::bswap: {
935 // If the only bits demanded come from one byte of the bswap result,
936 // just shift the input byte into position to eliminate the bswap.
937 unsigned NLZ = DemandedMask.countl_zero();
938 unsigned NTZ = DemandedMask.countr_zero();
939
940 // Round NTZ down to the next byte. If we have 11 trailing zeros, then
941 // we need all the bits down to bit 8. Likewise, round NLZ. If we
942 // have 14 leading zeros, round to 8.
943 NLZ = alignDown(NLZ, 8);
944 NTZ = alignDown(NTZ, 8);
945 // If we need exactly one byte, we can do this transformation.
946 if (BitWidth - NLZ - NTZ == 8) {
947 // Replace this with either a left or right shift to get the byte into
948 // the right place.
949 Instruction *NewVal;
950 if (NLZ > NTZ)
951 NewVal = BinaryOperator::CreateLShr(
952 II->getArgOperand(0), ConstantInt::get(VTy, NLZ - NTZ));
953 else
954 NewVal = BinaryOperator::CreateShl(
955 II->getArgOperand(0), ConstantInt::get(VTy, NTZ - NLZ));
956 NewVal->takeName(I);
957 return InsertNewInstWith(NewVal, I->getIterator());
958 }
959 break;
960 }
961 case Intrinsic::ptrmask: {
962 unsigned MaskWidth = I->getOperand(1)->getType()->getScalarSizeInBits();
963 RHSKnown = KnownBits(MaskWidth);
964 // If either the LHS or the RHS are Zero, the result is zero.
965 if (SimplifyDemandedBits(I, 0, DemandedMask, LHSKnown, Depth + 1) ||
967 I, 1, (DemandedMask & ~LHSKnown.Zero).zextOrTrunc(MaskWidth),
968 RHSKnown, Depth + 1))
969 return I;
970
971 // TODO: Should be 1-extend
972 RHSKnown = RHSKnown.anyextOrTrunc(BitWidth);
973 assert(!RHSKnown.hasConflict() && "Bits known to be one AND zero?");
974 assert(!LHSKnown.hasConflict() && "Bits known to be one AND zero?");
975
976 Known = LHSKnown & RHSKnown;
977 KnownBitsComputed = true;
978
979 // If the client is only demanding bits we know to be zero, return
980 // `llvm.ptrmask(p, 0)`. We can't return `null` here due to pointer
981 // provenance, but making the mask zero will be easily optimizable in
982 // the backend.
983 if (DemandedMask.isSubsetOf(Known.Zero) &&
984 !match(I->getOperand(1), m_Zero()))
985 return replaceOperand(
986 *I, 1, Constant::getNullValue(I->getOperand(1)->getType()));
987
988 // Mask in demanded space does nothing.
989 // NOTE: We may have attributes associated with the return value of the
990 // llvm.ptrmask intrinsic that will be lost when we just return the
991 // operand. We should try to preserve them.
992 if (DemandedMask.isSubsetOf(RHSKnown.One | LHSKnown.Zero))
993 return I->getOperand(0);
994
995 // If the RHS is a constant, see if we can simplify it.
997 I, 1, (DemandedMask & ~LHSKnown.Zero).zextOrTrunc(MaskWidth)))
998 return I;
999
1000 // Combine:
1001 // (ptrmask (getelementptr i8, ptr p, imm i), imm mask)
1002 // -> (ptrmask (getelementptr i8, ptr p, imm (i & mask)), imm mask)
1003 // where only the low bits known to be zero in the pointer are changed
1004 Value *InnerPtr;
1005 uint64_t GEPIndex;
1006 uint64_t PtrMaskImmediate;
1007 if (match(I, m_Intrinsic<Intrinsic::ptrmask>(
1008 m_PtrAdd(m_Value(InnerPtr), m_ConstantInt(GEPIndex)),
1009 m_ConstantInt(PtrMaskImmediate)))) {
1010
1011 LHSKnown = computeKnownBits(InnerPtr, Depth + 1, I);
1012 if (!LHSKnown.isZero()) {
1013 const unsigned trailingZeros = LHSKnown.countMinTrailingZeros();
1014 uint64_t PointerAlignBits = (uint64_t(1) << trailingZeros) - 1;
1015
1016 uint64_t HighBitsGEPIndex = GEPIndex & ~PointerAlignBits;
1017 uint64_t MaskedLowBitsGEPIndex =
1018 GEPIndex & PointerAlignBits & PtrMaskImmediate;
1019
1020 uint64_t MaskedGEPIndex = HighBitsGEPIndex | MaskedLowBitsGEPIndex;
1021
1022 if (MaskedGEPIndex != GEPIndex) {
1023 auto *GEP = cast<GetElementPtrInst>(II->getArgOperand(0));
1025 Type *GEPIndexType =
1026 DL.getIndexType(GEP->getPointerOperand()->getType());
1027 Value *MaskedGEP = Builder.CreateGEP(
1028 GEP->getSourceElementType(), InnerPtr,
1029 ConstantInt::get(GEPIndexType, MaskedGEPIndex),
1030 GEP->getName(), GEP->isInBounds());
1031
1032 replaceOperand(*I, 0, MaskedGEP);
1033 return I;
1034 }
1035 }
1036 }
1037
1038 break;
1039 }
1040
1041 case Intrinsic::fshr:
1042 case Intrinsic::fshl: {
1043 const APInt *SA;
1044 if (!match(I->getOperand(2), m_APInt(SA)))
1045 break;
1046
1047 // Normalize to funnel shift left. APInt shifts of BitWidth are well-
1048 // defined, so no need to special-case zero shifts here.
1049 uint64_t ShiftAmt = SA->urem(BitWidth);
1050 if (II->getIntrinsicID() == Intrinsic::fshr)
1051 ShiftAmt = BitWidth - ShiftAmt;
1052
1053 APInt DemandedMaskLHS(DemandedMask.lshr(ShiftAmt));
1054 APInt DemandedMaskRHS(DemandedMask.shl(BitWidth - ShiftAmt));
1055 if (I->getOperand(0) != I->getOperand(1)) {
1056 if (SimplifyDemandedBits(I, 0, DemandedMaskLHS, LHSKnown,
1057 Depth + 1) ||
1058 SimplifyDemandedBits(I, 1, DemandedMaskRHS, RHSKnown, Depth + 1))
1059 return I;
1060 } else { // fshl is a rotate
1061 // Avoid converting rotate into funnel shift.
1062 // Only simplify if one operand is constant.
1063 LHSKnown = computeKnownBits(I->getOperand(0), Depth + 1, I);
1064 if (DemandedMaskLHS.isSubsetOf(LHSKnown.Zero | LHSKnown.One) &&
1065 !match(I->getOperand(0), m_SpecificInt(LHSKnown.One))) {
1066 replaceOperand(*I, 0, Constant::getIntegerValue(VTy, LHSKnown.One));
1067 return I;
1068 }
1069
1070 RHSKnown = computeKnownBits(I->getOperand(1), Depth + 1, I);
1071 if (DemandedMaskRHS.isSubsetOf(RHSKnown.Zero | RHSKnown.One) &&
1072 !match(I->getOperand(1), m_SpecificInt(RHSKnown.One))) {
1073 replaceOperand(*I, 1, Constant::getIntegerValue(VTy, RHSKnown.One));
1074 return I;
1075 }
1076 }
1077
1078 Known.Zero = LHSKnown.Zero.shl(ShiftAmt) |
1079 RHSKnown.Zero.lshr(BitWidth - ShiftAmt);
1080 Known.One = LHSKnown.One.shl(ShiftAmt) |
1081 RHSKnown.One.lshr(BitWidth - ShiftAmt);
1082 KnownBitsComputed = true;
1083 break;
1084 }
1085 case Intrinsic::umax: {
1086 // UMax(A, C) == A if ...
1087 // The lowest non-zero bit of DemandMask is higher than the highest
1088 // non-zero bit of C.
1089 const APInt *C;
1090 unsigned CTZ = DemandedMask.countr_zero();
1091 if (match(II->getArgOperand(1), m_APInt(C)) &&
1092 CTZ >= C->getActiveBits())
1093 return II->getArgOperand(0);
1094 break;
1095 }
1096 case Intrinsic::umin: {
1097 // UMin(A, C) == A if ...
1098 // The lowest non-zero bit of DemandMask is higher than the highest
1099 // non-one bit of C.
1100 // This comes from using DeMorgans on the above umax example.
1101 const APInt *C;
1102 unsigned CTZ = DemandedMask.countr_zero();
1103 if (match(II->getArgOperand(1), m_APInt(C)) &&
1104 CTZ >= C->getBitWidth() - C->countl_one())
1105 return II->getArgOperand(0);
1106 break;
1107 }
1108 default: {
1109 // Handle target specific intrinsics
1110 std::optional<Value *> V = targetSimplifyDemandedUseBitsIntrinsic(
1111 *II, DemandedMask, Known, KnownBitsComputed);
1112 if (V)
1113 return *V;
1114 break;
1115 }
1116 }
1117 }
1118
1119 if (!KnownBitsComputed)
1120 computeKnownBits(V, Known, Depth, CxtI);
1121 break;
1122 }
1123 }
1124
1125 if (V->getType()->isPointerTy()) {
1126 Align Alignment = V->getPointerAlignment(DL);
1127 Known.Zero.setLowBits(Log2(Alignment));
1128 }
1129
1130 // If the client is only demanding bits that we know, return the known
1131 // constant. We can't directly simplify pointers as a constant because of
1132 // pointer provenance.
1133 // TODO: We could return `(inttoptr const)` for pointers.
1134 if (!V->getType()->isPointerTy() && DemandedMask.isSubsetOf(Known.Zero | Known.One))
1135 return Constant::getIntegerValue(VTy, Known.One);
1136
1137 if (VerifyKnownBits) {
1138 KnownBits ReferenceKnown = computeKnownBits(V, Depth, CxtI);
1139 if (Known != ReferenceKnown) {
1140 errs() << "Mismatched known bits for " << *V << " in "
1141 << I->getFunction()->getName() << "\n";
1142 errs() << "computeKnownBits(): " << ReferenceKnown << "\n";
1143 errs() << "SimplifyDemandedBits(): " << Known << "\n";
1144 std::abort();
1145 }
1146 }
1147
1148 return nullptr;
1149}
1150
1151/// Helper routine of SimplifyDemandedUseBits. It computes Known
1152/// bits. It also tries to handle simplifications that can be done based on
1153/// DemandedMask, but without modifying the Instruction.
1155 Instruction *I, const APInt &DemandedMask, KnownBits &Known, unsigned Depth,
1156 Instruction *CxtI) {
1157 unsigned BitWidth = DemandedMask.getBitWidth();
1158 Type *ITy = I->getType();
1159
1160 KnownBits LHSKnown(BitWidth);
1161 KnownBits RHSKnown(BitWidth);
1162
1163 // Despite the fact that we can't simplify this instruction in all User's
1164 // context, we can at least compute the known bits, and we can
1165 // do simplifications that apply to *just* the one user if we know that
1166 // this instruction has a simpler value in that context.
1167 switch (I->getOpcode()) {
1168 case Instruction::And: {
1169 computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, CxtI);
1170 computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, CxtI);
1171 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
1172 Depth, SQ.getWithInstruction(CxtI));
1174
1175 // If the client is only demanding bits that we know, return the known
1176 // constant.
1177 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
1178 return Constant::getIntegerValue(ITy, Known.One);
1179
1180 // If all of the demanded bits are known 1 on one side, return the other.
1181 // These bits cannot contribute to the result of the 'and' in this context.
1182 if (DemandedMask.isSubsetOf(LHSKnown.Zero | RHSKnown.One))
1183 return I->getOperand(0);
1184 if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.One))
1185 return I->getOperand(1);
1186
1187 break;
1188 }
1189 case Instruction::Or: {
1190 computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, CxtI);
1191 computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, CxtI);
1192 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
1193 Depth, SQ.getWithInstruction(CxtI));
1195
1196 // If the client is only demanding bits that we know, return the known
1197 // constant.
1198 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
1199 return Constant::getIntegerValue(ITy, Known.One);
1200
1201 // We can simplify (X|Y) -> X or Y in the user's context if we know that
1202 // only bits from X or Y are demanded.
1203 // If all of the demanded bits are known zero on one side, return the other.
1204 // These bits cannot contribute to the result of the 'or' in this context.
1205 if (DemandedMask.isSubsetOf(LHSKnown.One | RHSKnown.Zero))
1206 return I->getOperand(0);
1207 if (DemandedMask.isSubsetOf(RHSKnown.One | LHSKnown.Zero))
1208 return I->getOperand(1);
1209
1210 break;
1211 }
1212 case Instruction::Xor: {
1213 computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, CxtI);
1214 computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, CxtI);
1215 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
1216 Depth, SQ.getWithInstruction(CxtI));
1218
1219 // If the client is only demanding bits that we know, return the known
1220 // constant.
1221 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
1222 return Constant::getIntegerValue(ITy, Known.One);
1223
1224 // We can simplify (X^Y) -> X or Y in the user's context if we know that
1225 // only bits from X or Y are demanded.
1226 // If all of the demanded bits are known zero on one side, return the other.
1227 if (DemandedMask.isSubsetOf(RHSKnown.Zero))
1228 return I->getOperand(0);
1229 if (DemandedMask.isSubsetOf(LHSKnown.Zero))
1230 return I->getOperand(1);
1231
1232 break;
1233 }
1234 case Instruction::Add: {
1235 unsigned NLZ = DemandedMask.countl_zero();
1236 APInt DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
1237
1238 // If an operand adds zeros to every bit below the highest demanded bit,
1239 // that operand doesn't change the result. Return the other side.
1240 computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, CxtI);
1241 if (DemandedFromOps.isSubsetOf(RHSKnown.Zero))
1242 return I->getOperand(0);
1243
1244 computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, CxtI);
1245 if (DemandedFromOps.isSubsetOf(LHSKnown.Zero))
1246 return I->getOperand(1);
1247
1248 bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
1249 bool NUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
1250 Known =
1251 KnownBits::computeForAddSub(/*Add=*/true, NSW, NUW, LHSKnown, RHSKnown);
1253 break;
1254 }
1255 case Instruction::Sub: {
1256 unsigned NLZ = DemandedMask.countl_zero();
1257 APInt DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
1258
1259 // If an operand subtracts zeros from every bit below the highest demanded
1260 // bit, that operand doesn't change the result. Return the other side.
1261 computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, CxtI);
1262 if (DemandedFromOps.isSubsetOf(RHSKnown.Zero))
1263 return I->getOperand(0);
1264
1265 bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
1266 bool NUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
1267 computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, CxtI);
1268 Known = KnownBits::computeForAddSub(/*Add=*/false, NSW, NUW, LHSKnown,
1269 RHSKnown);
1271 break;
1272 }
1273 case Instruction::AShr: {
1274 // Compute the Known bits to simplify things downstream.
1275 computeKnownBits(I, Known, Depth, CxtI);
1276
1277 // If this user is only demanding bits that we know, return the known
1278 // constant.
1279 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
1280 return Constant::getIntegerValue(ITy, Known.One);
1281
1282 // If the right shift operand 0 is a result of a left shift by the same
1283 // amount, this is probably a zero/sign extension, which may be unnecessary,
1284 // if we do not demand any of the new sign bits. So, return the original
1285 // operand instead.
1286 const APInt *ShiftRC;
1287 const APInt *ShiftLC;
1288 Value *X;
1289 unsigned BitWidth = DemandedMask.getBitWidth();
1290 if (match(I,
1291 m_AShr(m_Shl(m_Value(X), m_APInt(ShiftLC)), m_APInt(ShiftRC))) &&
1292 ShiftLC == ShiftRC && ShiftLC->ult(BitWidth) &&
1293 DemandedMask.isSubsetOf(APInt::getLowBitsSet(
1294 BitWidth, BitWidth - ShiftRC->getZExtValue()))) {
1295 return X;
1296 }
1297
1298 break;
1299 }
1300 default:
1301 // Compute the Known bits to simplify things downstream.
1302 computeKnownBits(I, Known, Depth, CxtI);
1303
1304 // If this user is only demanding bits that we know, return the known
1305 // constant.
1306 if (DemandedMask.isSubsetOf(Known.Zero|Known.One))
1307 return Constant::getIntegerValue(ITy, Known.One);
1308
1309 break;
1310 }
1311
1312 return nullptr;
1313}
1314
1315/// Helper routine of SimplifyDemandedUseBits. It tries to simplify
1316/// "E1 = (X lsr C1) << C2", where the C1 and C2 are constant, into
1317/// "E2 = X << (C2 - C1)" or "E2 = X >> (C1 - C2)", depending on the sign
1318/// of "C2-C1".
1319///
1320/// Suppose E1 and E2 are generally different in bits S={bm, bm+1,
1321/// ..., bn}, without considering the specific value X is holding.
1322/// This transformation is legal iff one of following conditions is hold:
1323/// 1) All the bit in S are 0, in this case E1 == E2.
1324/// 2) We don't care those bits in S, per the input DemandedMask.
1325/// 3) Combination of 1) and 2). Some bits in S are 0, and we don't care the
1326/// rest bits.
1327///
1328/// Currently we only test condition 2).
1329///
1330/// As with SimplifyDemandedUseBits, it returns NULL if the simplification was
1331/// not successful.
1333 Instruction *Shr, const APInt &ShrOp1, Instruction *Shl,
1334 const APInt &ShlOp1, const APInt &DemandedMask, KnownBits &Known) {
1335 if (!ShlOp1 || !ShrOp1)
1336 return nullptr; // No-op.
1337
1338 Value *VarX = Shr->getOperand(0);
1339 Type *Ty = VarX->getType();
1340 unsigned BitWidth = Ty->getScalarSizeInBits();
1341 if (ShlOp1.uge(BitWidth) || ShrOp1.uge(BitWidth))
1342 return nullptr; // Undef.
1343
1344 unsigned ShlAmt = ShlOp1.getZExtValue();
1345 unsigned ShrAmt = ShrOp1.getZExtValue();
1346
1347 Known.One.clearAllBits();
1348 Known.Zero.setLowBits(ShlAmt - 1);
1349 Known.Zero &= DemandedMask;
1350
1351 APInt BitMask1(APInt::getAllOnes(BitWidth));
1352 APInt BitMask2(APInt::getAllOnes(BitWidth));
1353
1354 bool isLshr = (Shr->getOpcode() == Instruction::LShr);
1355 BitMask1 = isLshr ? (BitMask1.lshr(ShrAmt) << ShlAmt) :
1356 (BitMask1.ashr(ShrAmt) << ShlAmt);
1357
1358 if (ShrAmt <= ShlAmt) {
1359 BitMask2 <<= (ShlAmt - ShrAmt);
1360 } else {
1361 BitMask2 = isLshr ? BitMask2.lshr(ShrAmt - ShlAmt):
1362 BitMask2.ashr(ShrAmt - ShlAmt);
1363 }
1364
1365 // Check if condition-2 (see the comment to this function) is satified.
1366 if ((BitMask1 & DemandedMask) == (BitMask2 & DemandedMask)) {
1367 if (ShrAmt == ShlAmt)
1368 return VarX;
1369
1370 if (!Shr->hasOneUse())
1371 return nullptr;
1372
1373 BinaryOperator *New;
1374 if (ShrAmt < ShlAmt) {
1375 Constant *Amt = ConstantInt::get(VarX->getType(), ShlAmt - ShrAmt);
1376 New = BinaryOperator::CreateShl(VarX, Amt);
1377 BinaryOperator *Orig = cast<BinaryOperator>(Shl);
1378 New->setHasNoSignedWrap(Orig->hasNoSignedWrap());
1379 New->setHasNoUnsignedWrap(Orig->hasNoUnsignedWrap());
1380 } else {
1381 Constant *Amt = ConstantInt::get(VarX->getType(), ShrAmt - ShlAmt);
1382 New = isLshr ? BinaryOperator::CreateLShr(VarX, Amt) :
1383 BinaryOperator::CreateAShr(VarX, Amt);
1384 if (cast<BinaryOperator>(Shr)->isExact())
1385 New->setIsExact(true);
1386 }
1387
1388 return InsertNewInstWith(New, Shl->getIterator());
1389 }
1390
1391 return nullptr;
1392}
1393
1394/// The specified value produces a vector with any number of elements.
1395/// This method analyzes which elements of the operand are poison and
1396/// returns that information in PoisonElts.
1397///
1398/// DemandedElts contains the set of elements that are actually used by the
1399/// caller, and by default (AllowMultipleUsers equals false) the value is
1400/// simplified only if it has a single caller. If AllowMultipleUsers is set
1401/// to true, DemandedElts refers to the union of sets of elements that are
1402/// used by all callers.
1403///
1404/// If the information about demanded elements can be used to simplify the
1405/// operation, the operation is simplified, then the resultant value is
1406/// returned. This returns null if no change was made.
1408 APInt DemandedElts,
1409 APInt &PoisonElts,
1410 unsigned Depth,
1411 bool AllowMultipleUsers) {
1412 // Cannot analyze scalable type. The number of vector elements is not a
1413 // compile-time constant.
1414 if (isa<ScalableVectorType>(V->getType()))
1415 return nullptr;
1416
1417 unsigned VWidth = cast<FixedVectorType>(V->getType())->getNumElements();
1418 APInt EltMask(APInt::getAllOnes(VWidth));
1419 assert((DemandedElts & ~EltMask) == 0 && "Invalid DemandedElts!");
1420
1421 if (match(V, m_Poison())) {
1422 // If the entire vector is poison, just return this info.
1423 PoisonElts = EltMask;
1424 return nullptr;
1425 }
1426
1427 if (DemandedElts.isZero()) { // If nothing is demanded, provide poison.
1428 PoisonElts = EltMask;
1429 return PoisonValue::get(V->getType());
1430 }
1431
1432 PoisonElts = 0;
1433
1434 if (auto *C = dyn_cast<Constant>(V)) {
1435 // Check if this is identity. If so, return 0 since we are not simplifying
1436 // anything.
1437 if (DemandedElts.isAllOnes())
1438 return nullptr;
1439
1440 Type *EltTy = cast<VectorType>(V->getType())->getElementType();
1441 Constant *Poison = PoisonValue::get(EltTy);
1443 for (unsigned i = 0; i != VWidth; ++i) {
1444 if (!DemandedElts[i]) { // If not demanded, set to poison.
1445 Elts.push_back(Poison);
1446 PoisonElts.setBit(i);
1447 continue;
1448 }
1449
1450 Constant *Elt = C->getAggregateElement(i);
1451 if (!Elt) return nullptr;
1452
1453 Elts.push_back(Elt);
1454 if (isa<PoisonValue>(Elt)) // Already poison.
1455 PoisonElts.setBit(i);
1456 }
1457
1458 // If we changed the constant, return it.
1459 Constant *NewCV = ConstantVector::get(Elts);
1460 return NewCV != C ? NewCV : nullptr;
1461 }
1462
1463 // Limit search depth.
1464 if (Depth == 10)
1465 return nullptr;
1466
1467 if (!AllowMultipleUsers) {
1468 // If multiple users are using the root value, proceed with
1469 // simplification conservatively assuming that all elements
1470 // are needed.
1471 if (!V->hasOneUse()) {
1472 // Quit if we find multiple users of a non-root value though.
1473 // They'll be handled when it's their turn to be visited by
1474 // the main instcombine process.
1475 if (Depth != 0)
1476 // TODO: Just compute the PoisonElts information recursively.
1477 return nullptr;
1478
1479 // Conservatively assume that all elements are needed.
1480 DemandedElts = EltMask;
1481 }
1482 }
1483
1484 Instruction *I = dyn_cast<Instruction>(V);
1485 if (!I) return nullptr; // Only analyze instructions.
1486
1487 bool MadeChange = false;
1488 auto simplifyAndSetOp = [&](Instruction *Inst, unsigned OpNum,
1489 APInt Demanded, APInt &Undef) {
1490 auto *II = dyn_cast<IntrinsicInst>(Inst);
1491 Value *Op = II ? II->getArgOperand(OpNum) : Inst->getOperand(OpNum);
1492 if (Value *V = SimplifyDemandedVectorElts(Op, Demanded, Undef, Depth + 1)) {
1493 replaceOperand(*Inst, OpNum, V);
1494 MadeChange = true;
1495 }
1496 };
1497
1498 APInt PoisonElts2(VWidth, 0);
1499 APInt PoisonElts3(VWidth, 0);
1500 switch (I->getOpcode()) {
1501 default: break;
1502
1503 case Instruction::GetElementPtr: {
1504 // The LangRef requires that struct geps have all constant indices. As
1505 // such, we can't convert any operand to partial undef.
1506 auto mayIndexStructType = [](GetElementPtrInst &GEP) {
1507 for (auto I = gep_type_begin(GEP), E = gep_type_end(GEP);
1508 I != E; I++)
1509 if (I.isStruct())
1510 return true;
1511 return false;
1512 };
1513 if (mayIndexStructType(cast<GetElementPtrInst>(*I)))
1514 break;
1515
1516 // Conservatively track the demanded elements back through any vector
1517 // operands we may have. We know there must be at least one, or we
1518 // wouldn't have a vector result to get here. Note that we intentionally
1519 // merge the undef bits here since gepping with either an poison base or
1520 // index results in poison.
1521 for (unsigned i = 0; i < I->getNumOperands(); i++) {
1522 if (i == 0 ? match(I->getOperand(i), m_Undef())
1523 : match(I->getOperand(i), m_Poison())) {
1524 // If the entire vector is undefined, just return this info.
1525 PoisonElts = EltMask;
1526 return nullptr;
1527 }
1528 if (I->getOperand(i)->getType()->isVectorTy()) {
1529 APInt PoisonEltsOp(VWidth, 0);
1530 simplifyAndSetOp(I, i, DemandedElts, PoisonEltsOp);
1531 // gep(x, undef) is not undef, so skip considering idx ops here
1532 // Note that we could propagate poison, but we can't distinguish between
1533 // undef & poison bits ATM
1534 if (i == 0)
1535 PoisonElts |= PoisonEltsOp;
1536 }
1537 }
1538
1539 break;
1540 }
1541 case Instruction::InsertElement: {
1542 // If this is a variable index, we don't know which element it overwrites.
1543 // demand exactly the same input as we produce.
1544 ConstantInt *Idx = dyn_cast<ConstantInt>(I->getOperand(2));
1545 if (!Idx) {
1546 // Note that we can't propagate undef elt info, because we don't know
1547 // which elt is getting updated.
1548 simplifyAndSetOp(I, 0, DemandedElts, PoisonElts2);
1549 break;
1550 }
1551
1552 // The element inserted overwrites whatever was there, so the input demanded
1553 // set is simpler than the output set.
1554 unsigned IdxNo = Idx->getZExtValue();
1555 APInt PreInsertDemandedElts = DemandedElts;
1556 if (IdxNo < VWidth)
1557 PreInsertDemandedElts.clearBit(IdxNo);
1558
1559 // If we only demand the element that is being inserted and that element
1560 // was extracted from the same index in another vector with the same type,
1561 // replace this insert with that other vector.
1562 // Note: This is attempted before the call to simplifyAndSetOp because that
1563 // may change PoisonElts to a value that does not match with Vec.
1564 Value *Vec;
1565 if (PreInsertDemandedElts == 0 &&
1566 match(I->getOperand(1),
1567 m_ExtractElt(m_Value(Vec), m_SpecificInt(IdxNo))) &&
1568 Vec->getType() == I->getType()) {
1569 return Vec;
1570 }
1571
1572 simplifyAndSetOp(I, 0, PreInsertDemandedElts, PoisonElts);
1573
1574 // If this is inserting an element that isn't demanded, remove this
1575 // insertelement.
1576 if (IdxNo >= VWidth || !DemandedElts[IdxNo]) {
1577 Worklist.push(I);
1578 return I->getOperand(0);
1579 }
1580
1581 // The inserted element is defined.
1582 PoisonElts.clearBit(IdxNo);
1583 break;
1584 }
1585 case Instruction::ShuffleVector: {
1586 auto *Shuffle = cast<ShuffleVectorInst>(I);
1587 assert(Shuffle->getOperand(0)->getType() ==
1588 Shuffle->getOperand(1)->getType() &&
1589 "Expected shuffle operands to have same type");
1590 unsigned OpWidth = cast<FixedVectorType>(Shuffle->getOperand(0)->getType())
1591 ->getNumElements();
1592 // Handle trivial case of a splat. Only check the first element of LHS
1593 // operand.
1594 if (all_of(Shuffle->getShuffleMask(), [](int Elt) { return Elt == 0; }) &&
1595 DemandedElts.isAllOnes()) {
1596 if (!isa<PoisonValue>(I->getOperand(1))) {
1597 I->setOperand(1, PoisonValue::get(I->getOperand(1)->getType()));
1598 MadeChange = true;
1599 }
1600 APInt LeftDemanded(OpWidth, 1);
1601 APInt LHSPoisonElts(OpWidth, 0);
1602 simplifyAndSetOp(I, 0, LeftDemanded, LHSPoisonElts);
1603 if (LHSPoisonElts[0])
1604 PoisonElts = EltMask;
1605 else
1606 PoisonElts.clearAllBits();
1607 break;
1608 }
1609
1610 APInt LeftDemanded(OpWidth, 0), RightDemanded(OpWidth, 0);
1611 for (unsigned i = 0; i < VWidth; i++) {
1612 if (DemandedElts[i]) {
1613 unsigned MaskVal = Shuffle->getMaskValue(i);
1614 if (MaskVal != -1u) {
1615 assert(MaskVal < OpWidth * 2 &&
1616 "shufflevector mask index out of range!");
1617 if (MaskVal < OpWidth)
1618 LeftDemanded.setBit(MaskVal);
1619 else
1620 RightDemanded.setBit(MaskVal - OpWidth);
1621 }
1622 }
1623 }
1624
1625 APInt LHSPoisonElts(OpWidth, 0);
1626 simplifyAndSetOp(I, 0, LeftDemanded, LHSPoisonElts);
1627
1628 APInt RHSPoisonElts(OpWidth, 0);
1629 simplifyAndSetOp(I, 1, RightDemanded, RHSPoisonElts);
1630
1631 // If this shuffle does not change the vector length and the elements
1632 // demanded by this shuffle are an identity mask, then this shuffle is
1633 // unnecessary.
1634 //
1635 // We are assuming canonical form for the mask, so the source vector is
1636 // operand 0 and operand 1 is not used.
1637 //
1638 // Note that if an element is demanded and this shuffle mask is undefined
1639 // for that element, then the shuffle is not considered an identity
1640 // operation. The shuffle prevents poison from the operand vector from
1641 // leaking to the result by replacing poison with an undefined value.
1642 if (VWidth == OpWidth) {
1643 bool IsIdentityShuffle = true;
1644 for (unsigned i = 0; i < VWidth; i++) {
1645 unsigned MaskVal = Shuffle->getMaskValue(i);
1646 if (DemandedElts[i] && i != MaskVal) {
1647 IsIdentityShuffle = false;
1648 break;
1649 }
1650 }
1651 if (IsIdentityShuffle)
1652 return Shuffle->getOperand(0);
1653 }
1654
1655 bool NewPoisonElts = false;
1656 unsigned LHSIdx = -1u, LHSValIdx = -1u;
1657 unsigned RHSIdx = -1u, RHSValIdx = -1u;
1658 bool LHSUniform = true;
1659 bool RHSUniform = true;
1660 for (unsigned i = 0; i < VWidth; i++) {
1661 unsigned MaskVal = Shuffle->getMaskValue(i);
1662 if (MaskVal == -1u) {
1663 PoisonElts.setBit(i);
1664 } else if (!DemandedElts[i]) {
1665 NewPoisonElts = true;
1666 PoisonElts.setBit(i);
1667 } else if (MaskVal < OpWidth) {
1668 if (LHSPoisonElts[MaskVal]) {
1669 NewPoisonElts = true;
1670 PoisonElts.setBit(i);
1671 } else {
1672 LHSIdx = LHSIdx == -1u ? i : OpWidth;
1673 LHSValIdx = LHSValIdx == -1u ? MaskVal : OpWidth;
1674 LHSUniform = LHSUniform && (MaskVal == i);
1675 }
1676 } else {
1677 if (RHSPoisonElts[MaskVal - OpWidth]) {
1678 NewPoisonElts = true;
1679 PoisonElts.setBit(i);
1680 } else {
1681 RHSIdx = RHSIdx == -1u ? i : OpWidth;
1682 RHSValIdx = RHSValIdx == -1u ? MaskVal - OpWidth : OpWidth;
1683 RHSUniform = RHSUniform && (MaskVal - OpWidth == i);
1684 }
1685 }
1686 }
1687
1688 // Try to transform shuffle with constant vector and single element from
1689 // this constant vector to single insertelement instruction.
1690 // shufflevector V, C, <v1, v2, .., ci, .., vm> ->
1691 // insertelement V, C[ci], ci-n
1692 if (OpWidth ==
1693 cast<FixedVectorType>(Shuffle->getType())->getNumElements()) {
1694 Value *Op = nullptr;
1695 Constant *Value = nullptr;
1696 unsigned Idx = -1u;
1697
1698 // Find constant vector with the single element in shuffle (LHS or RHS).
1699 if (LHSIdx < OpWidth && RHSUniform) {
1700 if (auto *CV = dyn_cast<ConstantVector>(Shuffle->getOperand(0))) {
1701 Op = Shuffle->getOperand(1);
1702 Value = CV->getOperand(LHSValIdx);
1703 Idx = LHSIdx;
1704 }
1705 }
1706 if (RHSIdx < OpWidth && LHSUniform) {
1707 if (auto *CV = dyn_cast<ConstantVector>(Shuffle->getOperand(1))) {
1708 Op = Shuffle->getOperand(0);
1709 Value = CV->getOperand(RHSValIdx);
1710 Idx = RHSIdx;
1711 }
1712 }
1713 // Found constant vector with single element - convert to insertelement.
1714 if (Op && Value) {
1716 Op, Value, ConstantInt::get(Type::getInt64Ty(I->getContext()), Idx),
1717 Shuffle->getName());
1718 InsertNewInstWith(New, Shuffle->getIterator());
1719 return New;
1720 }
1721 }
1722 if (NewPoisonElts) {
1723 // Add additional discovered undefs.
1725 for (unsigned i = 0; i < VWidth; ++i) {
1726 if (PoisonElts[i])
1728 else
1729 Elts.push_back(Shuffle->getMaskValue(i));
1730 }
1731 Shuffle->setShuffleMask(Elts);
1732 MadeChange = true;
1733 }
1734 break;
1735 }
1736 case Instruction::Select: {
1737 // If this is a vector select, try to transform the select condition based
1738 // on the current demanded elements.
1739 SelectInst *Sel = cast<SelectInst>(I);
1740 if (Sel->getCondition()->getType()->isVectorTy()) {
1741 // TODO: We are not doing anything with PoisonElts based on this call.
1742 // It is overwritten below based on the other select operands. If an
1743 // element of the select condition is known undef, then we are free to
1744 // choose the output value from either arm of the select. If we know that
1745 // one of those values is undef, then the output can be undef.
1746 simplifyAndSetOp(I, 0, DemandedElts, PoisonElts);
1747 }
1748
1749 // Next, see if we can transform the arms of the select.
1750 APInt DemandedLHS(DemandedElts), DemandedRHS(DemandedElts);
1751 if (auto *CV = dyn_cast<ConstantVector>(Sel->getCondition())) {
1752 for (unsigned i = 0; i < VWidth; i++) {
1753 // isNullValue() always returns false when called on a ConstantExpr.
1754 // Skip constant expressions to avoid propagating incorrect information.
1755 Constant *CElt = CV->getAggregateElement(i);
1756 if (isa<ConstantExpr>(CElt))
1757 continue;
1758 // TODO: If a select condition element is undef, we can demand from
1759 // either side. If one side is known undef, choosing that side would
1760 // propagate undef.
1761 if (CElt->isNullValue())
1762 DemandedLHS.clearBit(i);
1763 else
1764 DemandedRHS.clearBit(i);
1765 }
1766 }
1767
1768 simplifyAndSetOp(I, 1, DemandedLHS, PoisonElts2);
1769 simplifyAndSetOp(I, 2, DemandedRHS, PoisonElts3);
1770
1771 // Output elements are undefined if the element from each arm is undefined.
1772 // TODO: This can be improved. See comment in select condition handling.
1773 PoisonElts = PoisonElts2 & PoisonElts3;
1774 break;
1775 }
1776 case Instruction::BitCast: {
1777 // Vector->vector casts only.
1778 VectorType *VTy = dyn_cast<VectorType>(I->getOperand(0)->getType());
1779 if (!VTy) break;
1780 unsigned InVWidth = cast<FixedVectorType>(VTy)->getNumElements();
1781 APInt InputDemandedElts(InVWidth, 0);
1782 PoisonElts2 = APInt(InVWidth, 0);
1783 unsigned Ratio;
1784
1785 if (VWidth == InVWidth) {
1786 // If we are converting from <4 x i32> -> <4 x f32>, we demand the same
1787 // elements as are demanded of us.
1788 Ratio = 1;
1789 InputDemandedElts = DemandedElts;
1790 } else if ((VWidth % InVWidth) == 0) {
1791 // If the number of elements in the output is a multiple of the number of
1792 // elements in the input then an input element is live if any of the
1793 // corresponding output elements are live.
1794 Ratio = VWidth / InVWidth;
1795 for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx)
1796 if (DemandedElts[OutIdx])
1797 InputDemandedElts.setBit(OutIdx / Ratio);
1798 } else if ((InVWidth % VWidth) == 0) {
1799 // If the number of elements in the input is a multiple of the number of
1800 // elements in the output then an input element is live if the
1801 // corresponding output element is live.
1802 Ratio = InVWidth / VWidth;
1803 for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx)
1804 if (DemandedElts[InIdx / Ratio])
1805 InputDemandedElts.setBit(InIdx);
1806 } else {
1807 // Unsupported so far.
1808 break;
1809 }
1810
1811 simplifyAndSetOp(I, 0, InputDemandedElts, PoisonElts2);
1812
1813 if (VWidth == InVWidth) {
1814 PoisonElts = PoisonElts2;
1815 } else if ((VWidth % InVWidth) == 0) {
1816 // If the number of elements in the output is a multiple of the number of
1817 // elements in the input then an output element is undef if the
1818 // corresponding input element is undef.
1819 for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx)
1820 if (PoisonElts2[OutIdx / Ratio])
1821 PoisonElts.setBit(OutIdx);
1822 } else if ((InVWidth % VWidth) == 0) {
1823 // If the number of elements in the input is a multiple of the number of
1824 // elements in the output then an output element is undef if all of the
1825 // corresponding input elements are undef.
1826 for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) {
1827 APInt SubUndef = PoisonElts2.lshr(OutIdx * Ratio).zextOrTrunc(Ratio);
1828 if (SubUndef.popcount() == Ratio)
1829 PoisonElts.setBit(OutIdx);
1830 }
1831 } else {
1832 llvm_unreachable("Unimp");
1833 }
1834 break;
1835 }
1836 case Instruction::FPTrunc:
1837 case Instruction::FPExt:
1838 simplifyAndSetOp(I, 0, DemandedElts, PoisonElts);
1839 break;
1840
1841 case Instruction::Call: {
1842 IntrinsicInst *II = dyn_cast<IntrinsicInst>(I);
1843 if (!II) break;
1844 switch (II->getIntrinsicID()) {
1845 case Intrinsic::masked_gather: // fallthrough
1846 case Intrinsic::masked_load: {
1847 // Subtlety: If we load from a pointer, the pointer must be valid
1848 // regardless of whether the element is demanded. Doing otherwise risks
1849 // segfaults which didn't exist in the original program.
1850 APInt DemandedPtrs(APInt::getAllOnes(VWidth)),
1851 DemandedPassThrough(DemandedElts);
1852 if (auto *CV = dyn_cast<ConstantVector>(II->getOperand(2)))
1853 for (unsigned i = 0; i < VWidth; i++) {
1854 Constant *CElt = CV->getAggregateElement(i);
1855 if (CElt->isNullValue())
1856 DemandedPtrs.clearBit(i);
1857 else if (CElt->isAllOnesValue())
1858 DemandedPassThrough.clearBit(i);
1859 }
1860 if (II->getIntrinsicID() == Intrinsic::masked_gather)
1861 simplifyAndSetOp(II, 0, DemandedPtrs, PoisonElts2);
1862 simplifyAndSetOp(II, 3, DemandedPassThrough, PoisonElts3);
1863
1864 // Output elements are undefined if the element from both sources are.
1865 // TODO: can strengthen via mask as well.
1866 PoisonElts = PoisonElts2 & PoisonElts3;
1867 break;
1868 }
1869 default: {
1870 // Handle target specific intrinsics
1871 std::optional<Value *> V = targetSimplifyDemandedVectorEltsIntrinsic(
1872 *II, DemandedElts, PoisonElts, PoisonElts2, PoisonElts3,
1873 simplifyAndSetOp);
1874 if (V)
1875 return *V;
1876 break;
1877 }
1878 } // switch on IntrinsicID
1879 break;
1880 } // case Call
1881 } // switch on Opcode
1882
1883 // TODO: We bail completely on integer div/rem and shifts because they have
1884 // UB/poison potential, but that should be refined.
1885 BinaryOperator *BO;
1886 if (match(I, m_BinOp(BO)) && !BO->isIntDivRem() && !BO->isShift()) {
1887 Value *X = BO->getOperand(0);
1888 Value *Y = BO->getOperand(1);
1889
1890 // Look for an equivalent binop except that one operand has been shuffled.
1891 // If the demand for this binop only includes elements that are the same as
1892 // the other binop, then we may be able to replace this binop with a use of
1893 // the earlier one.
1894 //
1895 // Example:
1896 // %other_bo = bo (shuf X, {0}), Y
1897 // %this_extracted_bo = extelt (bo X, Y), 0
1898 // -->
1899 // %other_bo = bo (shuf X, {0}), Y
1900 // %this_extracted_bo = extelt %other_bo, 0
1901 //
1902 // TODO: Handle demand of an arbitrary single element or more than one
1903 // element instead of just element 0.
1904 // TODO: Unlike general demanded elements transforms, this should be safe
1905 // for any (div/rem/shift) opcode too.
1906 if (DemandedElts == 1 && !X->hasOneUse() && !Y->hasOneUse() &&
1907 BO->hasOneUse() ) {
1908
1909 auto findShufBO = [&](bool MatchShufAsOp0) -> User * {
1910 // Try to use shuffle-of-operand in place of an operand:
1911 // bo X, Y --> bo (shuf X), Y
1912 // bo X, Y --> bo X, (shuf Y)
1913 BinaryOperator::BinaryOps Opcode = BO->getOpcode();
1914 Value *ShufOp = MatchShufAsOp0 ? X : Y;
1915 Value *OtherOp = MatchShufAsOp0 ? Y : X;
1916 for (User *U : OtherOp->users()) {
1917 ArrayRef<int> Mask;
1918 auto Shuf = m_Shuffle(m_Specific(ShufOp), m_Value(), m_Mask(Mask));
1919 if (BO->isCommutative()
1920 ? match(U, m_c_BinOp(Opcode, Shuf, m_Specific(OtherOp)))
1921 : MatchShufAsOp0
1922 ? match(U, m_BinOp(Opcode, Shuf, m_Specific(OtherOp)))
1923 : match(U, m_BinOp(Opcode, m_Specific(OtherOp), Shuf)))
1924 if (match(Mask, m_ZeroMask()) && Mask[0] != PoisonMaskElem)
1925 if (DT.dominates(U, I))
1926 return U;
1927 }
1928 return nullptr;
1929 };
1930
1931 if (User *ShufBO = findShufBO(/* MatchShufAsOp0 */ true))
1932 return ShufBO;
1933 if (User *ShufBO = findShufBO(/* MatchShufAsOp0 */ false))
1934 return ShufBO;
1935 }
1936
1937 simplifyAndSetOp(I, 0, DemandedElts, PoisonElts);
1938 simplifyAndSetOp(I, 1, DemandedElts, PoisonElts2);
1939
1940 // Output elements are undefined if both are undefined. Consider things
1941 // like undef & 0. The result is known zero, not undef.
1942 PoisonElts &= PoisonElts2;
1943 }
1944
1945 // If we've proven all of the lanes poison, return a poison value.
1946 // TODO: Intersect w/demanded lanes
1947 if (PoisonElts.isAllOnes())
1948 return PoisonValue::get(I->getType());
1949
1950 return MadeChange ? I : nullptr;
1951}
1952
1953/// For floating-point classes that resolve to a single bit pattern, return that
1954/// value.
1956 switch (Mask) {
1957 case fcPosZero:
1958 return ConstantFP::getZero(Ty);
1959 case fcNegZero:
1960 return ConstantFP::getZero(Ty, true);
1961 case fcPosInf:
1962 return ConstantFP::getInfinity(Ty);
1963 case fcNegInf:
1964 return ConstantFP::getInfinity(Ty, true);
1965 case fcNone:
1966 return PoisonValue::get(Ty);
1967 default:
1968 return nullptr;
1969 }
1970}
1971
1973 Value *V, const FPClassTest DemandedMask, KnownFPClass &Known,
1974 unsigned Depth, Instruction *CxtI) {
1975 assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
1976 Type *VTy = V->getType();
1977
1978 assert(Known == KnownFPClass() && "expected uninitialized state");
1979
1980 if (DemandedMask == fcNone)
1981 return isa<UndefValue>(V) ? nullptr : PoisonValue::get(VTy);
1982
1984 return nullptr;
1985
1986 Instruction *I = dyn_cast<Instruction>(V);
1987 if (!I) {
1988 // Handle constants and arguments
1989 Known = computeKnownFPClass(V, fcAllFlags, CxtI, Depth + 1);
1990 Value *FoldedToConst =
1991 getFPClassConstant(VTy, DemandedMask & Known.KnownFPClasses);
1992 return FoldedToConst == V ? nullptr : FoldedToConst;
1993 }
1994
1995 if (!I->hasOneUse())
1996 return nullptr;
1997
1998 // TODO: Should account for nofpclass/FastMathFlags on current instruction
1999 switch (I->getOpcode()) {
2000 case Instruction::FNeg: {
2001 if (SimplifyDemandedFPClass(I, 0, llvm::fneg(DemandedMask), Known,
2002 Depth + 1))
2003 return I;
2004 Known.fneg();
2005 break;
2006 }
2007 case Instruction::Call: {
2008 CallInst *CI = cast<CallInst>(I);
2009 switch (CI->getIntrinsicID()) {
2010 case Intrinsic::fabs:
2011 if (SimplifyDemandedFPClass(I, 0, llvm::inverse_fabs(DemandedMask), Known,
2012 Depth + 1))
2013 return I;
2014 Known.fabs();
2015 break;
2016 case Intrinsic::arithmetic_fence:
2017 if (SimplifyDemandedFPClass(I, 0, DemandedMask, Known, Depth + 1))
2018 return I;
2019 break;
2020 case Intrinsic::copysign: {
2021 // Flip on more potentially demanded classes
2022 const FPClassTest DemandedMaskAnySign = llvm::unknown_sign(DemandedMask);
2023 if (SimplifyDemandedFPClass(I, 0, DemandedMaskAnySign, Known, Depth + 1))
2024 return I;
2025
2026 if ((DemandedMask & fcPositive) == fcNone) {
2027 // Roundabout way of replacing with fneg(fabs)
2028 I->setOperand(1, ConstantFP::get(VTy, -1.0));
2029 return I;
2030 }
2031
2032 if ((DemandedMask & fcNegative) == fcNone) {
2033 // Roundabout way of replacing with fabs
2034 I->setOperand(1, ConstantFP::getZero(VTy));
2035 return I;
2036 }
2037
2038 KnownFPClass KnownSign =
2039 computeKnownFPClass(I->getOperand(1), fcAllFlags, CxtI, Depth + 1);
2040 Known.copysign(KnownSign);
2041 break;
2042 }
2043 default:
2044 Known = computeKnownFPClass(I, ~DemandedMask, CxtI, Depth + 1);
2045 break;
2046 }
2047
2048 break;
2049 }
2050 case Instruction::Select: {
2051 KnownFPClass KnownLHS, KnownRHS;
2052 if (SimplifyDemandedFPClass(I, 2, DemandedMask, KnownRHS, Depth + 1) ||
2053 SimplifyDemandedFPClass(I, 1, DemandedMask, KnownLHS, Depth + 1))
2054 return I;
2055
2056 if (KnownLHS.isKnownNever(DemandedMask))
2057 return I->getOperand(2);
2058 if (KnownRHS.isKnownNever(DemandedMask))
2059 return I->getOperand(1);
2060
2061 // TODO: Recognize clamping patterns
2062 Known = KnownLHS | KnownRHS;
2063 break;
2064 }
2065 default:
2066 Known = computeKnownFPClass(I, ~DemandedMask, CxtI, Depth + 1);
2067 break;
2068 }
2069
2070 return getFPClassConstant(VTy, DemandedMask & Known.KnownFPClasses);
2071}
2072
2074 FPClassTest DemandedMask,
2075 KnownFPClass &Known,
2076 unsigned Depth) {
2077 Use &U = I->getOperandUse(OpNo);
2078 Value *NewVal =
2079 SimplifyDemandedUseFPClass(U.get(), DemandedMask, Known, Depth, I);
2080 if (!NewVal)
2081 return false;
2082 if (Instruction *OpInst = dyn_cast<Instruction>(U))
2083 salvageDebugInfo(*OpInst);
2084
2085 replaceUse(U, NewVal);
2086 return true;
2087}
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
Returns the sub type a function will return at a given Idx Should correspond to the result type of an ExtractValue instruction executed with just that one unsigned Idx
static GCMetadataPrinterRegistry::Add< ErlangGCPrinter > X("erlang", "erlang-compatible garbage collector")
Hexagon Common GEP
This file provides internal interfaces used to implement the InstCombine.
static Constant * getFPClassConstant(Type *Ty, FPClassTest Mask)
For floating-point classes that resolve to a single bit pattern, return that value.
static cl::opt< bool > VerifyKnownBits("instcombine-verify-known-bits", cl::desc("Verify that computeKnownBits() and " "SimplifyDemandedBits() are consistent"), cl::Hidden, cl::init(false))
static unsigned getBitWidth(Type *Ty, const DataLayout &DL)
Returns the bitwidth of the given scalar or pointer type.
static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo, const APInt &Demanded)
Check to see if the specified operand of the specified instruction is a constant integer.
This file provides the interface for the instcombine pass implementation.
#define I(x, y, z)
Definition: MD5.cpp:58
static GCMetadataPrinterRegistry::Add< OcamlGCMetadataPrinter > Y("ocaml", "ocaml 3.10-compatible collector")
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
SI optimize exec mask operations pre RA
static unsigned getBitWidth(Type *Ty, const DataLayout &DL)
Returns the bitwidth of the given scalar or pointer type.
Value * RHS
Value * LHS
Class for arbitrary precision integers.
Definition: APInt.h:76
static APInt getAllOnes(unsigned numBits)
Return an APInt of a specified width with all bits set.
Definition: APInt.h:212
void clearBit(unsigned BitPosition)
Set a given bit to 0.
Definition: APInt.h:1385
static APInt getSignMask(unsigned BitWidth)
Get the SignMask for a specific bit width.
Definition: APInt.h:207
uint64_t getZExtValue() const
Get zero extended value.
Definition: APInt.h:1491
void setHighBits(unsigned hiBits)
Set the top hiBits bits.
Definition: APInt.h:1370
unsigned popcount() const
Count the number of bits set.
Definition: APInt.h:1620
APInt zextOrTrunc(unsigned width) const
Zero extend or truncate to width.
Definition: APInt.cpp:1002
unsigned getActiveBits() const
Compute the number of active bits in the value.
Definition: APInt.h:1463
APInt trunc(unsigned width) const
Truncate to new width.
Definition: APInt.cpp:906
void setBit(unsigned BitPosition)
Set the given bit to 1 whose position is given as "bitPosition".
Definition: APInt.h:1308
APInt abs() const
Get the absolute value.
Definition: APInt.h:1737
bool isAllOnes() const
Determine if all bits are set. This is true for zero-width values.
Definition: APInt.h:349
bool isZero() const
Determine if this value is zero, i.e. all bits are clear.
Definition: APInt.h:358
APInt urem(const APInt &RHS) const
Unsigned remainder operation.
Definition: APInt.cpp:1672
void setSignBit()
Set the sign bit to 1.
Definition: APInt.h:1318
unsigned getBitWidth() const
Return the number of bits in the APInt.
Definition: APInt.h:1439
bool ult(const APInt &RHS) const
Unsigned less than comparison.
Definition: APInt.h:1089
bool intersects(const APInt &RHS) const
This operation tests if there are any pairs of corresponding bits between this APInt and RHS that are...
Definition: APInt.h:1227
void clearAllBits()
Set every bit to 0.
Definition: APInt.h:1375
unsigned countr_zero() const
Count the number of trailing zero bits.
Definition: APInt.h:1589
unsigned countl_zero() const
The APInt version of std::countl_zero.
Definition: APInt.h:1548
void clearLowBits(unsigned loBits)
Set bottom loBits bits to 0.
Definition: APInt.h:1395
uint64_t getLimitedValue(uint64_t Limit=UINT64_MAX) const
If this value is smaller than the specified limit, return it, otherwise return the limit value.
Definition: APInt.h:453
APInt ashr(unsigned ShiftAmt) const
Arithmetic right-shift function.
Definition: APInt.h:805
void setAllBits()
Set every bit to 1.
Definition: APInt.h:1297
APInt shl(unsigned shiftAmt) const
Left-shift function.
Definition: APInt.h:851
bool isSubsetOf(const APInt &RHS) const
This operation checks that all bits set in this APInt are also set in RHS.
Definition: APInt.h:1235
bool isPowerOf2() const
Check if this APInt's value is a power of two greater than zero.
Definition: APInt.h:418
static APInt getLowBitsSet(unsigned numBits, unsigned loBitsSet)
Constructs an APInt value that has the bottom loBitsSet bits set.
Definition: APInt.h:284
static APInt getHighBitsSet(unsigned numBits, unsigned hiBitsSet)
Constructs an APInt value that has the top hiBitsSet bits set.
Definition: APInt.h:274
void setLowBits(unsigned loBits)
Set the bottom loBits bits.
Definition: APInt.h:1367
bool isOne() const
Determine if this is a value of 1.
Definition: APInt.h:367
void lshrInPlace(unsigned ShiftAmt)
Logical right-shift this APInt by ShiftAmt in place.
Definition: APInt.h:836
APInt lshr(unsigned shiftAmt) const
Logical right-shift function.
Definition: APInt.h:829
bool uge(const APInt &RHS) const
Unsigned greater or equal comparison.
Definition: APInt.h:1199
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
BinaryOps getOpcode() const
Definition: InstrTypes.h:486
Intrinsic::ID getIntrinsicID() const
Returns the intrinsic ID of the intrinsic called or Intrinsic::not_intrinsic if the called function i...
This class represents a function call, abstracting a target machine's calling convention.
static CallInst * Create(FunctionType *Ty, Value *F, const Twine &NameStr, BasicBlock::iterator InsertBefore)
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:574
Predicate
This enumeration lists the possible predicates for CmpInst subclasses.
Definition: InstrTypes.h:960
static Constant * getInfinity(Type *Ty, bool Negative=false)
Definition: Constants.cpp:1083
static Constant * getZero(Type *Ty, bool Negative=false)
Definition: Constants.cpp:1037
This is the shared class of boolean and integer constants.
Definition: Constants.h:80
const APInt & getValue() const
Return the constant as an APInt value reference.
Definition: Constants.h:145
static Constant * get(ArrayRef< Constant * > V)
Definition: Constants.cpp:1398
This is an important base class in LLVM.
Definition: Constant.h:41
static Constant * getIntegerValue(Type *Ty, const APInt &V)
Return the value for an integer or pointer constant, or a vector thereof, with the given scalar value...
Definition: Constants.cpp:400
static Constant * getAllOnesValue(Type *Ty)
Definition: Constants.cpp:417
bool isAllOnesValue() const
Return true if this is the value that would be returned by getAllOnesValue.
Definition: Constants.cpp:107
static Constant * getNullValue(Type *Ty)
Constructor to create a '0' constant of arbitrary type.
Definition: Constants.cpp:370
Constant * getAggregateElement(unsigned Elt) const
For aggregates (struct/array/vector) return the constant that corresponds to the specified element if...
Definition: Constants.cpp:432
bool isNullValue() const
Return true if this is the value that would be returned by getNullValue.
Definition: Constants.cpp:90
This class represents an Operation in the Expression.
A parsed version of the target data layout string in and methods for querying it.
Definition: DataLayout.h:110
IntegerType * getIndexType(LLVMContext &C, unsigned AddressSpace) const
Returns the type of a GEP index in AddressSpace.
Definition: DataLayout.cpp:905
bool dominates(const BasicBlock *BB, const Use &U) const
Return true if the (end of the) basic block BB dominates the use U.
Definition: Dominators.cpp:122
an instruction for type-safe pointer arithmetic to access elements of arrays and structs
Definition: Instructions.h:973
CallInst * CreateUnaryIntrinsic(Intrinsic::ID ID, Value *V, Instruction *FMFSource=nullptr, const Twine &Name="")
Create a call to intrinsic ID with 1 operand which is mangled on its type.
Definition: IRBuilder.cpp:913
Value * CreateTrunc(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:2001
Value * CreateSExt(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:2017
Value * CreateLShr(Value *LHS, Value *RHS, const Twine &Name="", bool isExact=false)
Definition: IRBuilder.h:1431
Value * CreateNot(Value *V, const Twine &Name="")
Definition: IRBuilder.h:1743
Value * CreateAnd(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1469
Value * CreateOr(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1491
void SetInsertPoint(BasicBlock *TheBB)
This specifies that created instructions should be appended to the end of the specified block.
Definition: IRBuilder.h:180
Value * CreateXor(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1513
Value * CreateGEP(Type *Ty, Value *Ptr, ArrayRef< Value * > IdxList, const Twine &Name="", bool IsInBounds=false)
Definition: IRBuilder.h:1860
static InsertElementInst * Create(Value *Vec, Value *NewElt, Value *Idx, const Twine &NameStr, BasicBlock::iterator InsertBefore)
KnownFPClass computeKnownFPClass(Value *Val, FastMathFlags FMF, FPClassTest Interested=fcAllFlags, const Instruction *CtxI=nullptr, unsigned Depth=0) const
bool SimplifyDemandedBits(Instruction *I, unsigned Op, const APInt &DemandedMask, KnownBits &Known, unsigned Depth=0) override
This form of SimplifyDemandedBits simplifies the specified instruction operand if possible,...
Value * SimplifyDemandedVectorElts(Value *V, APInt DemandedElts, APInt &PoisonElts, unsigned Depth=0, bool AllowMultipleUsers=false) override
The specified value produces a vector with any number of elements.
Value * SimplifyDemandedUseBits(Value *V, APInt DemandedMask, KnownBits &Known, unsigned Depth, Instruction *CxtI)
Attempts to replace V with a simpler value based on the demanded bits.
std::optional< std::pair< Intrinsic::ID, SmallVector< Value *, 3 > > > convertOrOfShiftsToFunnelShift(Instruction &Or)
Value * SimplifyMultipleUseDemandedBits(Instruction *I, const APInt &DemandedMask, KnownBits &Known, unsigned Depth, Instruction *CxtI)
Helper routine of SimplifyDemandedUseBits.
Value * simplifyShrShlDemandedBits(Instruction *Shr, const APInt &ShrOp1, Instruction *Shl, const APInt &ShlOp1, const APInt &DemandedMask, KnownBits &Known)
Helper routine of SimplifyDemandedUseBits.
Value * SimplifyDemandedUseFPClass(Value *V, FPClassTest DemandedMask, KnownFPClass &Known, unsigned Depth, Instruction *CxtI)
Attempts to replace V with a simpler value based on the demanded floating-point classes.
bool SimplifyDemandedFPClass(Instruction *I, unsigned Op, FPClassTest DemandedMask, KnownFPClass &Known, unsigned Depth=0)
bool SimplifyDemandedInstructionBits(Instruction &Inst)
Tries to simplify operands to an integer instruction based on its demanded bits.
SimplifyQuery SQ
Definition: InstCombiner.h:76
Instruction * replaceInstUsesWith(Instruction &I, Value *V)
A combiner-aware RAUW-like routine.
Definition: InstCombiner.h:385
void replaceUse(Use &U, Value *NewValue)
Replace use and add the previously used value to the worklist.
Definition: InstCombiner.h:417
InstructionWorklist & Worklist
A worklist of the instructions that need to be simplified.
Definition: InstCombiner.h:64
Instruction * InsertNewInstWith(Instruction *New, BasicBlock::iterator Old)
Same as InsertNewInstBefore, but also sets the debug loc.
Definition: InstCombiner.h:374
const DataLayout & DL
Definition: InstCombiner.h:75
unsigned ComputeNumSignBits(const Value *Op, unsigned Depth=0, const Instruction *CxtI=nullptr) const
Definition: InstCombiner.h:451
std::optional< Value * > targetSimplifyDemandedVectorEltsIntrinsic(IntrinsicInst &II, APInt DemandedElts, APInt &UndefElts, APInt &UndefElts2, APInt &UndefElts3, std::function< void(Instruction *, unsigned, APInt, APInt &)> SimplifyAndSetOp)
Instruction * replaceOperand(Instruction &I, unsigned OpNum, Value *V)
Replace operand of instruction and add old operand to the worklist.
Definition: InstCombiner.h:409
DominatorTree & DT
Definition: InstCombiner.h:74
std::optional< Value * > targetSimplifyDemandedUseBitsIntrinsic(IntrinsicInst &II, APInt DemandedMask, KnownBits &Known, bool &KnownBitsComputed)
void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth, const Instruction *CxtI) const
Definition: InstCombiner.h:430
BuilderTy & Builder
Definition: InstCombiner.h:60
void push(Instruction *I)
Push the instruction onto the worklist stack.
bool hasNoUnsignedWrap() const LLVM_READONLY
Determine whether the no unsigned wrap flag is set.
bool hasNoSignedWrap() const LLVM_READONLY
Determine whether the no signed wrap flag is set.
bool isCommutative() const LLVM_READONLY
Return true if the instruction is commutative:
unsigned getOpcode() const
Returns a member of one of the enums like Instruction::Add.
Definition: Instruction.h:252
void setIsExact(bool b=true)
Set or clear the exact flag on this instruction, which must be an operator which supports this flag.
bool isShift() const
Definition: Instruction.h:259
bool isIntDivRem() const
Definition: Instruction.h:258
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:47
Intrinsic::ID getIntrinsicID() const
Return the intrinsic ID of this intrinsic.
Definition: IntrinsicInst.h:54
bool hasNoSignedWrap() const
Test whether this operation is known to never undergo signed overflow, aka the nsw property.
Definition: Operator.h:108
bool hasNoUnsignedWrap() const
Test whether this operation is known to never undergo unsigned overflow, aka the nuw property.
Definition: Operator.h:102
static PoisonValue * get(Type *T)
Static factory methods - Return an 'poison' object of the specified type.
Definition: Constants.cpp:1827
This class represents the LLVM 'select' instruction.
const Value * getCondition() const
void push_back(const T &Elt)
Definition: SmallVector.h:426
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1209
The instances of the Type class are immutable: once they are created, they are never changed.
Definition: Type.h:45
bool isVectorTy() const
True if this is an instance of VectorType.
Definition: Type.h:265
bool isIntOrIntVectorTy() const
Return true if this is an integer type or a vector of integer types.
Definition: Type.h:234
unsigned getScalarSizeInBits() const LLVM_READONLY
If this is a vector type, return the getPrimitiveSizeInBits value for the element type.
static IntegerType * getInt64Ty(LLVMContext &C)
static UndefValue * get(Type *T)
Static factory methods - Return an 'undef' object of the specified type.
Definition: Constants.cpp:1808
A Use represents the edge between a Value definition and its users.
Definition: Use.h:43
Value * getOperand(unsigned i) const
Definition: User.h:169
LLVM Value Representation.
Definition: Value.h:74
Type * getType() const
All values are typed, get the type of this value.
Definition: Value.h:255
bool hasOneUse() const
Return true if there is exactly one use of this value.
Definition: Value.h:434
iterator_range< user_iterator > users()
Definition: Value.h:421
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:309
void takeName(Value *V)
Transfer the name from V to this value.
Definition: Value.cpp:383
Base class of all SIMD vector types.
Definition: DerivedTypes.h:403
This class represents zero extension of integer types.
self_iterator getIterator()
Definition: ilist_node.h:109
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
@ C
The default llvm calling convention, compatible with C.
Definition: CallingConv.h:34
Function * getDeclaration(Module *M, ID id, ArrayRef< Type * > Tys=std::nullopt)
Create or insert an LLVM Function declaration for an intrinsic, and return it.
Definition: Function.cpp:1459
class_match< PoisonValue > m_Poison()
Match an arbitrary poison constant.
Definition: PatternMatch.h:155
PtrAdd_match< PointerOpTy, OffsetOpTy > m_PtrAdd(const PointerOpTy &PointerOp, const OffsetOpTy &OffsetOp)
Matches GEP with i8 source element type.
BinaryOp_match< LHS, RHS, Instruction::Add > m_Add(const LHS &L, const RHS &R)
class_match< BinaryOperator > m_BinOp()
Match an arbitrary binary operation and ignore it.
Definition: PatternMatch.h:100
BinaryOp_match< LHS, RHS, Instruction::AShr > m_AShr(const LHS &L, const RHS &R)
specific_intval< false > m_SpecificInt(const APInt &V)
Match a specific integer value or vector with all elements equal to the value.
Definition: PatternMatch.h:918
bool match(Val *V, const Pattern &P)
Definition: PatternMatch.h:49
specificval_ty m_Specific(const Value *V)
Match if we have a specific specified value.
Definition: PatternMatch.h:821
BinOpPred_match< LHS, RHS, is_right_shift_op > m_Shr(const LHS &L, const RHS &R)
Matches logical shift operations.
TwoOps_match< Val_t, Idx_t, Instruction::ExtractElement > m_ExtractElt(const Val_t &Val, const Idx_t &Idx)
Matches ExtractElementInst.
class_match< ConstantInt > m_ConstantInt()
Match an arbitrary ConstantInt and ignore it.
Definition: PatternMatch.h:163
CmpClass_match< LHS, RHS, ICmpInst, ICmpInst::Predicate > m_ICmp(ICmpInst::Predicate &Pred, const LHS &L, const RHS &R)
OneUse_match< T > m_OneUse(const T &SubPattern)
Definition: PatternMatch.h:67
TwoOps_match< V1_t, V2_t, Instruction::ShuffleVector > m_Shuffle(const V1_t &v1, const V2_t &v2)
Matches ShuffleVectorInst independently of mask value.
match_combine_and< class_match< Constant >, match_unless< constantexpr_match > > m_ImmConstant()
Match an arbitrary immediate Constant and ignore it.
Definition: PatternMatch.h:800
CastInst_match< OpTy, ZExtInst > m_ZExt(const OpTy &Op)
Matches ZExt.
BinaryOp_match< LHS, RHS, Instruction::Add, true > m_c_Add(const LHS &L, const RHS &R)
Matches a Add with LHS and RHS in either order.
apint_match m_APInt(const APInt *&Res)
Match a ConstantInt or splatted ConstantVector, binding the specified pointer to the contained APInt.
Definition: PatternMatch.h:294
class_match< Value > m_Value()
Match an arbitrary value and ignore it.
Definition: PatternMatch.h:92
AnyBinaryOp_match< LHS, RHS, true > m_c_BinOp(const LHS &L, const RHS &R)
Matches a BinaryOperator with LHS and RHS in either order.
BinaryOp_match< LHS, RHS, Instruction::LShr > m_LShr(const LHS &L, const RHS &R)
BinaryOp_match< LHS, RHS, Instruction::Shl > m_Shl(const LHS &L, const RHS &R)
auto m_Undef()
Match an arbitrary undef constant.
Definition: PatternMatch.h:152
BinaryOp_match< cst_pred_ty< is_all_ones >, ValTy, Instruction::Xor, true > m_Not(const ValTy &V)
Matches a 'Not' as 'xor V, -1' or 'xor -1, V'.
CastInst_match< OpTy, SExtInst > m_SExt(const OpTy &Op)
Matches SExt.
is_zero m_Zero()
Match any null constant or a vector with all elements equal to 0.
Definition: PatternMatch.h:561
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:450
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
bool haveNoCommonBitsSet(const WithCache< const Value * > &LHSCache, const WithCache< const Value * > &RHSCache, const SimplifyQuery &SQ)
Return true if LHS and RHS have no common bits set.
bool all_of(R &&range, UnaryPredicate P)
Provide wrappers to std::all_of which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1731
int countr_one(T Value)
Count the number of ones from the least significant bit to the first zero bit.
Definition: bit.h:307
void salvageDebugInfo(const MachineRegisterInfo &MRI, MachineInstr &MI)
Assuming the instruction MI is going to be deleted, attempt to salvage debug users of MI by writing t...
Definition: Utils.cpp:1582
gep_type_iterator gep_type_end(const User *GEP)
void computeKnownBitsFromContext(const Value *V, KnownBits &Known, unsigned Depth, const SimplifyQuery &Q)
Merge bits known from context-dependent facts into Known.
KnownBits analyzeKnownBitsFromAndXorOr(const Operator *I, const KnownBits &KnownLHS, const KnownBits &KnownRHS, unsigned Depth, const SimplifyQuery &SQ)
Using KnownBits LHS/RHS produce the known bits for logic op (and/xor/or).
constexpr unsigned MaxAnalysisRecursionDepth
Definition: ValueTracking.h:47
FPClassTest fneg(FPClassTest Mask)
Return the test mask which returns true if the value's sign bit is flipped.
FPClassTest
Floating-point class tests, supported by 'is_fpclass' intrinsic.
FPClassTest inverse_fabs(FPClassTest Mask)
Return the test mask which returns true after fabs is applied to the value.
Constant * ConstantFoldBinaryOpOperands(unsigned Opcode, Constant *LHS, Constant *RHS, const DataLayout &DL)
Attempt to constant fold a binary operation with the specified operands.
constexpr int PoisonMaskElem
raw_fd_ostream & errs()
This returns a reference to a raw_ostream for standard error.
@ Or
Bitwise or logical OR of integers.
@ Xor
Bitwise or logical XOR of integers.
@ And
Bitwise or logical AND of integers.
FPClassTest unknown_sign(FPClassTest Mask)
Return the test mask which returns true if the value could have the same set of classes,...
constexpr unsigned BitWidth
Definition: BitmaskEnum.h:191
gep_type_iterator gep_type_begin(const User *GEP)
unsigned Log2(Align A)
Returns the log2 of the alignment.
Definition: Alignment.h:208
uint64_t alignDown(uint64_t Value, uint64_t Align, uint64_t Skew=0)
Returns the largest uint64_t less than or equal to Value and is Skew mod Align.
Definition: MathExtras.h:428
This struct is a compact representation of a valid (non-zero power of two) alignment.
Definition: Alignment.h:39
static KnownBits makeConstant(const APInt &C)
Create known bits from a known constant.
Definition: KnownBits.h:297
KnownBits anyextOrTrunc(unsigned BitWidth) const
Return known bits for an "any" extension or truncation of the value we're tracking.
Definition: KnownBits.h:182
bool isNonNegative() const
Returns true if this value is known to be non-negative.
Definition: KnownBits.h:104
void makeNonNegative()
Make this value non-negative.
Definition: KnownBits.h:120
static KnownBits urem(const KnownBits &LHS, const KnownBits &RHS)
Compute known bits for urem(LHS, RHS).
Definition: KnownBits.cpp:1018
bool hasConflict() const
Returns true if there is conflicting information.
Definition: KnownBits.h:47
unsigned getBitWidth() const
Get the bit width of this value.
Definition: KnownBits.h:40
void resetAll()
Resets the known state of all bits.
Definition: KnownBits.h:71
KnownBits intersectWith(const KnownBits &RHS) const
Returns KnownBits information that is known to be true for both this and RHS.
Definition: KnownBits.h:307
KnownBits sext(unsigned BitWidth) const
Return known bits for a sign extension of the value we're tracking.
Definition: KnownBits.h:176
KnownBits zextOrTrunc(unsigned BitWidth) const
Return known bits for a zero extension or truncation of the value we're tracking.
Definition: KnownBits.h:192
static KnownBits udiv(const KnownBits &LHS, const KnownBits &RHS, bool Exact=false)
Compute known bits for udiv(LHS, RHS).
Definition: KnownBits.cpp:976
static KnownBits computeForAddSub(bool Add, bool NSW, bool NUW, const KnownBits &LHS, const KnownBits &RHS)
Compute known bits resulting from adding LHS and RHS.
Definition: KnownBits.cpp:57
bool isNegative() const
Returns true if this value is known to be negative.
Definition: KnownBits.h:101
static KnownBits shl(const KnownBits &LHS, const KnownBits &RHS, bool NUW=false, bool NSW=false, bool ShAmtNonZero=false)
Compute known bits for shl(LHS, RHS).
Definition: KnownBits.cpp:279
FPClassTest KnownFPClasses
Floating-point classes the value could be one of.
void copysign(const KnownFPClass &Sign)
bool isKnownNever(FPClassTest Mask) const
Return true if it's known this can never be one of the mask entries.
SimplifyQuery getWithInstruction(const Instruction *I) const
Definition: SimplifyQuery.h:96