LLVM 20.0.0git
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
34 "instcombine-simplify-vector-elts-depth",
36 "Depth limit when simplifying vector instructions and their operands"),
37 cl::Hidden, cl::init(10));
38
39/// Check to see if the specified operand of the specified instruction is a
40/// constant integer. If so, check to see if there are any bits set in the
41/// constant that are not demanded. If so, shrink the constant and return true.
42static bool ShrinkDemandedConstant(Instruction *I, unsigned OpNo,
43 const APInt &Demanded) {
44 assert(I && "No instruction?");
45 assert(OpNo < I->getNumOperands() && "Operand index too large");
46
47 // The operand must be a constant integer or splat integer.
48 Value *Op = I->getOperand(OpNo);
49 const APInt *C;
50 if (!match(Op, m_APInt(C)))
51 return false;
52
53 // If there are no bits set that aren't demanded, nothing to do.
54 if (C->isSubsetOf(Demanded))
55 return false;
56
57 // This instruction is producing bits that are not demanded. Shrink the RHS.
58 I->setOperand(OpNo, ConstantInt::get(Op->getType(), *C & Demanded));
59
60 return true;
61}
62
63/// Returns the bitwidth of the given scalar or pointer type. For vector types,
64/// returns the element type's bitwidth.
65static unsigned getBitWidth(Type *Ty, const DataLayout &DL) {
66 if (unsigned BitWidth = Ty->getScalarSizeInBits())
67 return BitWidth;
68
69 return DL.getPointerTypeSizeInBits(Ty);
70}
71
72/// Inst is an integer instruction that SimplifyDemandedBits knows about. See if
73/// the instruction has any properties that allow us to simplify its operands.
75 KnownBits &Known) {
76 APInt DemandedMask(APInt::getAllOnes(Known.getBitWidth()));
77 Value *V = SimplifyDemandedUseBits(&Inst, DemandedMask, Known,
78 0, SQ.getWithInstruction(&Inst));
79 if (!V) return false;
80 if (V == &Inst) return true;
81 replaceInstUsesWith(Inst, V);
82 return true;
83}
84
85/// Inst is an integer instruction that SimplifyDemandedBits knows about. See if
86/// the instruction has any properties that allow us to simplify its operands.
88 KnownBits Known(getBitWidth(Inst.getType(), DL));
89 return SimplifyDemandedInstructionBits(Inst, Known);
90}
91
92/// This form of SimplifyDemandedBits simplifies the specified instruction
93/// operand if possible, updating it in place. It returns true if it made any
94/// change and false otherwise.
96 const APInt &DemandedMask,
97 KnownBits &Known, unsigned Depth,
98 const SimplifyQuery &Q) {
99 Use &U = I->getOperandUse(OpNo);
100 Value *V = U.get();
101 if (isa<Constant>(V)) {
102 llvm::computeKnownBits(V, Known, Depth, Q);
103 return false;
104 }
105
106 Known.resetAll();
107 if (DemandedMask.isZero()) {
108 // Not demanding any bits from V.
109 replaceUse(U, UndefValue::get(V->getType()));
110 return true;
111 }
112
113 Instruction *VInst = dyn_cast<Instruction>(V);
114 if (!VInst) {
115 llvm::computeKnownBits(V, Known, Depth, Q);
116 return false;
117 }
118
120 return false;
121
122 Value *NewVal;
123 if (VInst->hasOneUse()) {
124 // If the instruction has one use, we can directly simplify it.
125 NewVal = SimplifyDemandedUseBits(VInst, DemandedMask, Known, Depth, Q);
126 } else {
127 // If there are multiple uses of this instruction, then we can simplify
128 // VInst to some other value, but not modify the instruction.
129 NewVal =
130 SimplifyMultipleUseDemandedBits(VInst, DemandedMask, Known, Depth, Q);
131 }
132 if (!NewVal) return false;
133 if (Instruction* OpInst = dyn_cast<Instruction>(U))
134 salvageDebugInfo(*OpInst);
135
136 replaceUse(U, NewVal);
137 return true;
138}
139
140/// This function attempts to replace V with a simpler value based on the
141/// demanded bits. When this function is called, it is known that only the bits
142/// set in DemandedMask of the result of V are ever used downstream.
143/// Consequently, depending on the mask and V, it may be possible to replace V
144/// with a constant or one of its operands. In such cases, this function does
145/// the replacement and returns true. In all other cases, it returns false after
146/// analyzing the expression and setting KnownOne and known to be one in the
147/// expression. Known.Zero contains all the bits that are known to be zero in
148/// the expression. These are provided to potentially allow the caller (which
149/// might recursively be SimplifyDemandedBits itself) to simplify the
150/// expression.
151/// Known.One and Known.Zero always follow the invariant that:
152/// Known.One & Known.Zero == 0.
153/// That is, a bit can't be both 1 and 0. The bits in Known.One and Known.Zero
154/// are accurate even for bits not in DemandedMask. Note
155/// also that the bitwidth of V, DemandedMask, Known.Zero and Known.One must all
156/// be the same.
157///
158/// This returns null if it did not change anything and it permits no
159/// simplification. This returns V itself if it did some simplification of V's
160/// operands based on the information about what bits are demanded. This returns
161/// some other non-null value if it found out that V is equal to another value
162/// in the context where the specified bits are demanded, but not for all users.
164 const APInt &DemandedMask,
165 KnownBits &Known,
166 unsigned Depth,
167 const SimplifyQuery &Q) {
168 assert(I != nullptr && "Null pointer of Value???");
169 assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
170 uint32_t BitWidth = DemandedMask.getBitWidth();
171 Type *VTy = I->getType();
172 assert(
173 (!VTy->isIntOrIntVectorTy() || VTy->getScalarSizeInBits() == BitWidth) &&
174 Known.getBitWidth() == BitWidth &&
175 "Value *V, DemandedMask and Known must have same BitWidth");
176
177 KnownBits LHSKnown(BitWidth), RHSKnown(BitWidth);
178
179 // Update flags after simplifying an operand based on the fact that some high
180 // order bits are not demanded.
181 auto disableWrapFlagsBasedOnUnusedHighBits = [](Instruction *I,
182 unsigned NLZ) {
183 if (NLZ > 0) {
184 // Disable the nsw and nuw flags here: We can no longer guarantee that
185 // we won't wrap after simplification. Removing the nsw/nuw flags is
186 // legal here because the top bit is not demanded.
187 I->setHasNoSignedWrap(false);
188 I->setHasNoUnsignedWrap(false);
189 }
190 return I;
191 };
192
193 // If the high-bits of an ADD/SUB/MUL are not demanded, then we do not care
194 // about the high bits of the operands.
195 auto simplifyOperandsBasedOnUnusedHighBits = [&](APInt &DemandedFromOps) {
196 unsigned NLZ = DemandedMask.countl_zero();
197 // Right fill the mask of bits for the operands to demand the most
198 // significant bit and all those below it.
199 DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
200 if (ShrinkDemandedConstant(I, 0, DemandedFromOps) ||
201 SimplifyDemandedBits(I, 0, DemandedFromOps, LHSKnown, Depth + 1, Q) ||
202 ShrinkDemandedConstant(I, 1, DemandedFromOps) ||
203 SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1, Q)) {
204 disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
205 return true;
206 }
207 return false;
208 };
209
210 switch (I->getOpcode()) {
211 default:
212 llvm::computeKnownBits(I, Known, Depth, Q);
213 break;
214 case Instruction::And: {
215 // If either the LHS or the RHS are Zero, the result is zero.
216 if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1, Q) ||
217 SimplifyDemandedBits(I, 0, DemandedMask & ~RHSKnown.Zero, LHSKnown,
218 Depth + 1, Q))
219 return I;
220
221 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
222 Depth, Q);
223
224 // If the client is only demanding bits that we know, return the known
225 // constant.
226 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
227 return Constant::getIntegerValue(VTy, Known.One);
228
229 // If all of the demanded bits are known 1 on one side, return the other.
230 // These bits cannot contribute to the result of the 'and'.
231 if (DemandedMask.isSubsetOf(LHSKnown.Zero | RHSKnown.One))
232 return I->getOperand(0);
233 if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.One))
234 return I->getOperand(1);
235
236 // If the RHS is a constant, see if we can simplify it.
237 if (ShrinkDemandedConstant(I, 1, DemandedMask & ~LHSKnown.Zero))
238 return I;
239
240 break;
241 }
242 case Instruction::Or: {
243 // If either the LHS or the RHS are One, the result is One.
244 if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1, Q) ||
245 SimplifyDemandedBits(I, 0, DemandedMask & ~RHSKnown.One, LHSKnown,
246 Depth + 1, Q)) {
247 // Disjoint flag may not longer hold.
248 I->dropPoisonGeneratingFlags();
249 return I;
250 }
251
252 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
253 Depth, Q);
254
255 // If the client is only demanding bits that we know, return the known
256 // constant.
257 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
258 return Constant::getIntegerValue(VTy, Known.One);
259
260 // If all of the demanded bits are known zero on one side, return the other.
261 // These bits cannot contribute to the result of the 'or'.
262 if (DemandedMask.isSubsetOf(LHSKnown.One | RHSKnown.Zero))
263 return I->getOperand(0);
264 if (DemandedMask.isSubsetOf(RHSKnown.One | LHSKnown.Zero))
265 return I->getOperand(1);
266
267 // If the RHS is a constant, see if we can simplify it.
268 if (ShrinkDemandedConstant(I, 1, DemandedMask))
269 return I;
270
271 // Infer disjoint flag if no common bits are set.
272 if (!cast<PossiblyDisjointInst>(I)->isDisjoint()) {
273 WithCache<const Value *> LHSCache(I->getOperand(0), LHSKnown),
274 RHSCache(I->getOperand(1), RHSKnown);
275 if (haveNoCommonBitsSet(LHSCache, RHSCache, Q)) {
276 cast<PossiblyDisjointInst>(I)->setIsDisjoint(true);
277 return I;
278 }
279 }
280
281 break;
282 }
283 case Instruction::Xor: {
284 if (SimplifyDemandedBits(I, 1, DemandedMask, RHSKnown, Depth + 1, Q) ||
285 SimplifyDemandedBits(I, 0, DemandedMask, LHSKnown, Depth + 1, Q))
286 return I;
287 Value *LHS, *RHS;
288 if (DemandedMask == 1 &&
289 match(I->getOperand(0), m_Intrinsic<Intrinsic::ctpop>(m_Value(LHS))) &&
290 match(I->getOperand(1), m_Intrinsic<Intrinsic::ctpop>(m_Value(RHS)))) {
291 // (ctpop(X) ^ ctpop(Y)) & 1 --> ctpop(X^Y) & 1
294 auto *Xor = Builder.CreateXor(LHS, RHS);
295 return Builder.CreateUnaryIntrinsic(Intrinsic::ctpop, Xor);
296 }
297
298 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
299 Depth, Q);
300
301 // If the client is only demanding bits that we know, return the known
302 // constant.
303 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
304 return Constant::getIntegerValue(VTy, Known.One);
305
306 // If all of the demanded bits are known zero on one side, return the other.
307 // These bits cannot contribute to the result of the 'xor'.
308 if (DemandedMask.isSubsetOf(RHSKnown.Zero))
309 return I->getOperand(0);
310 if (DemandedMask.isSubsetOf(LHSKnown.Zero))
311 return I->getOperand(1);
312
313 // If all of the demanded bits are known to be zero on one side or the
314 // other, turn this into an *inclusive* or.
315 // e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0
316 if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.Zero)) {
317 Instruction *Or =
318 BinaryOperator::CreateOr(I->getOperand(0), I->getOperand(1));
319 if (DemandedMask.isAllOnes())
320 cast<PossiblyDisjointInst>(Or)->setIsDisjoint(true);
321 Or->takeName(I);
322 return InsertNewInstWith(Or, I->getIterator());
323 }
324
325 // If all of the demanded bits on one side are known, and all of the set
326 // bits on that side are also known to be set on the other side, turn this
327 // into an AND, as we know the bits will be cleared.
328 // e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2
329 if (DemandedMask.isSubsetOf(RHSKnown.Zero|RHSKnown.One) &&
330 RHSKnown.One.isSubsetOf(LHSKnown.One)) {
332 ~RHSKnown.One & DemandedMask);
333 Instruction *And = BinaryOperator::CreateAnd(I->getOperand(0), AndC);
334 return InsertNewInstWith(And, I->getIterator());
335 }
336
337 // If the RHS is a constant, see if we can change it. Don't alter a -1
338 // constant because that's a canonical 'not' op, and that is better for
339 // combining, SCEV, and codegen.
340 const APInt *C;
341 if (match(I->getOperand(1), m_APInt(C)) && !C->isAllOnes()) {
342 if ((*C | ~DemandedMask).isAllOnes()) {
343 // Force bits to 1 to create a 'not' op.
344 I->setOperand(1, ConstantInt::getAllOnesValue(VTy));
345 return I;
346 }
347 // If we can't turn this into a 'not', try to shrink the constant.
348 if (ShrinkDemandedConstant(I, 1, DemandedMask))
349 return I;
350 }
351
352 // If our LHS is an 'and' and if it has one use, and if any of the bits we
353 // are flipping are known to be set, then the xor is just resetting those
354 // bits to zero. We can just knock out bits from the 'and' and the 'xor',
355 // simplifying both of them.
356 if (Instruction *LHSInst = dyn_cast<Instruction>(I->getOperand(0))) {
357 ConstantInt *AndRHS, *XorRHS;
358 if (LHSInst->getOpcode() == Instruction::And && LHSInst->hasOneUse() &&
359 match(I->getOperand(1), m_ConstantInt(XorRHS)) &&
360 match(LHSInst->getOperand(1), m_ConstantInt(AndRHS)) &&
361 (LHSKnown.One & RHSKnown.One & DemandedMask) != 0) {
362 APInt NewMask = ~(LHSKnown.One & RHSKnown.One & DemandedMask);
363
364 Constant *AndC = ConstantInt::get(VTy, NewMask & AndRHS->getValue());
365 Instruction *NewAnd = BinaryOperator::CreateAnd(I->getOperand(0), AndC);
366 InsertNewInstWith(NewAnd, I->getIterator());
367
368 Constant *XorC = ConstantInt::get(VTy, NewMask & XorRHS->getValue());
369 Instruction *NewXor = BinaryOperator::CreateXor(NewAnd, XorC);
370 return InsertNewInstWith(NewXor, I->getIterator());
371 }
372 }
373 break;
374 }
375 case Instruction::Select: {
376 if (SimplifyDemandedBits(I, 2, DemandedMask, RHSKnown, Depth + 1, Q) ||
377 SimplifyDemandedBits(I, 1, DemandedMask, LHSKnown, Depth + 1, Q))
378 return I;
379
380 // If the operands are constants, see if we can simplify them.
381 // This is similar to ShrinkDemandedConstant, but for a select we want to
382 // try to keep the selected constants the same as icmp value constants, if
383 // we can. This helps not break apart (or helps put back together)
384 // canonical patterns like min and max.
385 auto CanonicalizeSelectConstant = [](Instruction *I, unsigned OpNo,
386 const APInt &DemandedMask) {
387 const APInt *SelC;
388 if (!match(I->getOperand(OpNo), m_APInt(SelC)))
389 return false;
390
391 // Get the constant out of the ICmp, if there is one.
392 // Only try this when exactly 1 operand is a constant (if both operands
393 // are constant, the icmp should eventually simplify). Otherwise, we may
394 // invert the transform that reduces set bits and infinite-loop.
395 Value *X;
396 const APInt *CmpC;
397 if (!match(I->getOperand(0), m_ICmp(m_Value(X), m_APInt(CmpC))) ||
398 isa<Constant>(X) || CmpC->getBitWidth() != SelC->getBitWidth())
399 return ShrinkDemandedConstant(I, OpNo, DemandedMask);
400
401 // If the constant is already the same as the ICmp, leave it as-is.
402 if (*CmpC == *SelC)
403 return false;
404 // If the constants are not already the same, but can be with the demand
405 // mask, use the constant value from the ICmp.
406 if ((*CmpC & DemandedMask) == (*SelC & DemandedMask)) {
407 I->setOperand(OpNo, ConstantInt::get(I->getType(), *CmpC));
408 return true;
409 }
410 return ShrinkDemandedConstant(I, OpNo, DemandedMask);
411 };
412 if (CanonicalizeSelectConstant(I, 1, DemandedMask) ||
413 CanonicalizeSelectConstant(I, 2, DemandedMask))
414 return I;
415
416 // Only known if known in both the LHS and RHS.
417 adjustKnownBitsForSelectArm(LHSKnown, I->getOperand(0), I->getOperand(1),
418 /*Invert=*/false, Depth, Q);
419 adjustKnownBitsForSelectArm(RHSKnown, I->getOperand(0), I->getOperand(2),
420 /*Invert=*/true, Depth, Q);
421 Known = LHSKnown.intersectWith(RHSKnown);
422 break;
423 }
424 case Instruction::Trunc: {
425 // If we do not demand the high bits of a right-shifted and truncated value,
426 // then we may be able to truncate it before the shift.
427 Value *X;
428 const APInt *C;
429 if (match(I->getOperand(0), m_OneUse(m_LShr(m_Value(X), m_APInt(C))))) {
430 // The shift amount must be valid (not poison) in the narrow type, and
431 // it must not be greater than the high bits demanded of the result.
432 if (C->ult(VTy->getScalarSizeInBits()) &&
433 C->ule(DemandedMask.countl_zero())) {
434 // trunc (lshr X, C) --> lshr (trunc X), C
437 Value *Trunc = Builder.CreateTrunc(X, VTy);
438 return Builder.CreateLShr(Trunc, C->getZExtValue());
439 }
440 }
441 }
442 [[fallthrough]];
443 case Instruction::ZExt: {
444 unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
445
446 APInt InputDemandedMask = DemandedMask.zextOrTrunc(SrcBitWidth);
447 KnownBits InputKnown(SrcBitWidth);
448 if (SimplifyDemandedBits(I, 0, InputDemandedMask, InputKnown, Depth + 1,
449 Q)) {
450 // For zext nneg, we may have dropped the instruction which made the
451 // input non-negative.
452 I->dropPoisonGeneratingFlags();
453 return I;
454 }
455 assert(InputKnown.getBitWidth() == SrcBitWidth && "Src width changed?");
456 if (I->getOpcode() == Instruction::ZExt && I->hasNonNeg() &&
457 !InputKnown.isNegative())
458 InputKnown.makeNonNegative();
459 Known = InputKnown.zextOrTrunc(BitWidth);
460
461 break;
462 }
463 case Instruction::SExt: {
464 // Compute the bits in the result that are not present in the input.
465 unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
466
467 APInt InputDemandedBits = DemandedMask.trunc(SrcBitWidth);
468
469 // If any of the sign extended bits are demanded, we know that the sign
470 // bit is demanded.
471 if (DemandedMask.getActiveBits() > SrcBitWidth)
472 InputDemandedBits.setBit(SrcBitWidth-1);
473
474 KnownBits InputKnown(SrcBitWidth);
475 if (SimplifyDemandedBits(I, 0, InputDemandedBits, InputKnown, Depth + 1, Q))
476 return I;
477
478 // If the input sign bit is known zero, or if the NewBits are not demanded
479 // convert this into a zero extension.
480 if (InputKnown.isNonNegative() ||
481 DemandedMask.getActiveBits() <= SrcBitWidth) {
482 // Convert to ZExt cast.
483 CastInst *NewCast = new ZExtInst(I->getOperand(0), VTy);
484 NewCast->takeName(I);
485 return InsertNewInstWith(NewCast, I->getIterator());
486 }
487
488 // If the sign bit of the input is known set or clear, then we know the
489 // top bits of the result.
490 Known = InputKnown.sext(BitWidth);
491 break;
492 }
493 case Instruction::Add: {
494 if ((DemandedMask & 1) == 0) {
495 // If we do not need the low bit, try to convert bool math to logic:
496 // add iN (zext i1 X), (sext i1 Y) --> sext (~X & Y) to iN
497 Value *X, *Y;
499 m_OneUse(m_SExt(m_Value(Y))))) &&
500 X->getType()->isIntOrIntVectorTy(1) && X->getType() == Y->getType()) {
501 // Truth table for inputs and output signbits:
502 // X:0 | X:1
503 // ----------
504 // Y:0 | 0 | 0 |
505 // Y:1 | -1 | 0 |
506 // ----------
510 return Builder.CreateSExt(AndNot, VTy);
511 }
512
513 // add iN (sext i1 X), (sext i1 Y) --> sext (X | Y) to iN
514 if (match(I, m_Add(m_SExt(m_Value(X)), m_SExt(m_Value(Y)))) &&
515 X->getType()->isIntOrIntVectorTy(1) && X->getType() == Y->getType() &&
516 (I->getOperand(0)->hasOneUse() || I->getOperand(1)->hasOneUse())) {
517
518 // Truth table for inputs and output signbits:
519 // X:0 | X:1
520 // -----------
521 // Y:0 | -1 | -1 |
522 // Y:1 | -1 | 0 |
523 // -----------
526 Value *Or = Builder.CreateOr(X, Y);
527 return Builder.CreateSExt(Or, VTy);
528 }
529 }
530
531 // Right fill the mask of bits for the operands to demand the most
532 // significant bit and all those below it.
533 unsigned NLZ = DemandedMask.countl_zero();
534 APInt DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
535 if (ShrinkDemandedConstant(I, 1, DemandedFromOps) ||
536 SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1, Q))
537 return disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
538
539 // If low order bits are not demanded and known to be zero in one operand,
540 // then we don't need to demand them from the other operand, since they
541 // can't cause overflow into any bits that are demanded in the result.
542 unsigned NTZ = (~DemandedMask & RHSKnown.Zero).countr_one();
543 APInt DemandedFromLHS = DemandedFromOps;
544 DemandedFromLHS.clearLowBits(NTZ);
545 if (ShrinkDemandedConstant(I, 0, DemandedFromLHS) ||
546 SimplifyDemandedBits(I, 0, DemandedFromLHS, LHSKnown, Depth + 1, Q))
547 return disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
548
549 // If we are known to be adding zeros to every bit below
550 // the highest demanded bit, we just return the other side.
551 if (DemandedFromOps.isSubsetOf(RHSKnown.Zero))
552 return I->getOperand(0);
553 if (DemandedFromOps.isSubsetOf(LHSKnown.Zero))
554 return I->getOperand(1);
555
556 // (add X, C) --> (xor X, C) IFF C is equal to the top bit of the DemandMask
557 {
558 const APInt *C;
559 if (match(I->getOperand(1), m_APInt(C)) &&
560 C->isOneBitSet(DemandedMask.getActiveBits() - 1)) {
563 return Builder.CreateXor(I->getOperand(0), ConstantInt::get(VTy, *C));
564 }
565 }
566
567 // Otherwise just compute the known bits of the result.
568 bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
569 bool NUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
570 Known = KnownBits::add(LHSKnown, RHSKnown, NSW, NUW);
571 break;
572 }
573 case Instruction::Sub: {
574 // Right fill the mask of bits for the operands to demand the most
575 // significant bit and all those below it.
576 unsigned NLZ = DemandedMask.countl_zero();
577 APInt DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
578 if (ShrinkDemandedConstant(I, 1, DemandedFromOps) ||
579 SimplifyDemandedBits(I, 1, DemandedFromOps, RHSKnown, Depth + 1, Q))
580 return disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
581
582 // If low order bits are not demanded and are known to be zero in RHS,
583 // then we don't need to demand them from LHS, since they can't cause a
584 // borrow from any bits that are demanded in the result.
585 unsigned NTZ = (~DemandedMask & RHSKnown.Zero).countr_one();
586 APInt DemandedFromLHS = DemandedFromOps;
587 DemandedFromLHS.clearLowBits(NTZ);
588 if (ShrinkDemandedConstant(I, 0, DemandedFromLHS) ||
589 SimplifyDemandedBits(I, 0, DemandedFromLHS, LHSKnown, Depth + 1, Q))
590 return disableWrapFlagsBasedOnUnusedHighBits(I, NLZ);
591
592 // If we are known to be subtracting zeros from every bit below
593 // the highest demanded bit, we just return the other side.
594 if (DemandedFromOps.isSubsetOf(RHSKnown.Zero))
595 return I->getOperand(0);
596 // We can't do this with the LHS for subtraction, unless we are only
597 // demanding the LSB.
598 if (DemandedFromOps.isOne() && DemandedFromOps.isSubsetOf(LHSKnown.Zero))
599 return I->getOperand(1);
600
601 // Canonicalize sub mask, X -> ~X
602 const APInt *LHSC;
603 if (match(I->getOperand(0), m_LowBitMask(LHSC)) &&
604 DemandedFromOps.isSubsetOf(*LHSC)) {
607 return Builder.CreateNot(I->getOperand(1));
608 }
609
610 // Otherwise just compute the known bits of the result.
611 bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
612 bool NUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
613 Known = KnownBits::sub(LHSKnown, RHSKnown, NSW, NUW);
614 break;
615 }
616 case Instruction::Mul: {
617 APInt DemandedFromOps;
618 if (simplifyOperandsBasedOnUnusedHighBits(DemandedFromOps))
619 return I;
620
621 if (DemandedMask.isPowerOf2()) {
622 // The LSB of X*Y is set only if (X & 1) == 1 and (Y & 1) == 1.
623 // If we demand exactly one bit N and we have "X * (C' << N)" where C' is
624 // odd (has LSB set), then the left-shifted low bit of X is the answer.
625 unsigned CTZ = DemandedMask.countr_zero();
626 const APInt *C;
627 if (match(I->getOperand(1), m_APInt(C)) && C->countr_zero() == CTZ) {
628 Constant *ShiftC = ConstantInt::get(VTy, CTZ);
629 Instruction *Shl = BinaryOperator::CreateShl(I->getOperand(0), ShiftC);
630 return InsertNewInstWith(Shl, I->getIterator());
631 }
632 }
633 // For a squared value "X * X", the bottom 2 bits are 0 and X[0] because:
634 // X * X is odd iff X is odd.
635 // 'Quadratic Reciprocity': X * X -> 0 for bit[1]
636 if (I->getOperand(0) == I->getOperand(1) && DemandedMask.ult(4)) {
637 Constant *One = ConstantInt::get(VTy, 1);
638 Instruction *And1 = BinaryOperator::CreateAnd(I->getOperand(0), One);
639 return InsertNewInstWith(And1, I->getIterator());
640 }
641
642 llvm::computeKnownBits(I, Known, Depth, Q);
643 break;
644 }
645 case Instruction::Shl: {
646 const APInt *SA;
647 if (match(I->getOperand(1), m_APInt(SA))) {
648 const APInt *ShrAmt;
649 if (match(I->getOperand(0), m_Shr(m_Value(), m_APInt(ShrAmt))))
650 if (Instruction *Shr = dyn_cast<Instruction>(I->getOperand(0)))
651 if (Value *R = simplifyShrShlDemandedBits(Shr, *ShrAmt, I, *SA,
652 DemandedMask, Known))
653 return R;
654
655 // Do not simplify if shl is part of funnel-shift pattern
656 if (I->hasOneUse()) {
657 auto *Inst = dyn_cast<Instruction>(I->user_back());
658 if (Inst && Inst->getOpcode() == BinaryOperator::Or) {
659 if (auto Opt = convertOrOfShiftsToFunnelShift(*Inst)) {
660 auto [IID, FShiftArgs] = *Opt;
661 if ((IID == Intrinsic::fshl || IID == Intrinsic::fshr) &&
662 FShiftArgs[0] == FShiftArgs[1]) {
663 llvm::computeKnownBits(I, Known, Depth, Q);
664 break;
665 }
666 }
667 }
668 }
669
670 // We only want bits that already match the signbit then we don't
671 // need to shift.
672 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth - 1);
673 if (DemandedMask.countr_zero() >= ShiftAmt) {
674 if (I->hasNoSignedWrap()) {
675 unsigned NumHiDemandedBits = BitWidth - DemandedMask.countr_zero();
676 unsigned SignBits =
677 ComputeNumSignBits(I->getOperand(0), Depth + 1, Q.CxtI);
678 if (SignBits > ShiftAmt && SignBits - ShiftAmt >= NumHiDemandedBits)
679 return I->getOperand(0);
680 }
681
682 // If we can pre-shift a right-shifted constant to the left without
683 // losing any high bits and we don't demand the low bits, then eliminate
684 // the left-shift:
685 // (C >> X) << LeftShiftAmtC --> (C << LeftShiftAmtC) >> X
686 Value *X;
687 Constant *C;
688 if (match(I->getOperand(0), m_LShr(m_ImmConstant(C), m_Value(X)))) {
689 Constant *LeftShiftAmtC = ConstantInt::get(VTy, ShiftAmt);
690 Constant *NewC = ConstantFoldBinaryOpOperands(Instruction::Shl, C,
691 LeftShiftAmtC, DL);
692 if (ConstantFoldBinaryOpOperands(Instruction::LShr, NewC,
693 LeftShiftAmtC, DL) == C) {
694 Instruction *Lshr = BinaryOperator::CreateLShr(NewC, X);
695 return InsertNewInstWith(Lshr, I->getIterator());
696 }
697 }
698 }
699
700 APInt DemandedMaskIn(DemandedMask.lshr(ShiftAmt));
701
702 // If the shift is NUW/NSW, then it does demand the high bits.
703 ShlOperator *IOp = cast<ShlOperator>(I);
704 if (IOp->hasNoSignedWrap())
705 DemandedMaskIn.setHighBits(ShiftAmt+1);
706 else if (IOp->hasNoUnsignedWrap())
707 DemandedMaskIn.setHighBits(ShiftAmt);
708
709 if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1, Q))
710 return I;
711
712 Known = KnownBits::shl(Known,
714 /* NUW */ IOp->hasNoUnsignedWrap(),
715 /* NSW */ IOp->hasNoSignedWrap());
716 } else {
717 // This is a variable shift, so we can't shift the demand mask by a known
718 // amount. But if we are not demanding high bits, then we are not
719 // demanding those bits from the pre-shifted operand either.
720 if (unsigned CTLZ = DemandedMask.countl_zero()) {
721 APInt DemandedFromOp(APInt::getLowBitsSet(BitWidth, BitWidth - CTLZ));
722 if (SimplifyDemandedBits(I, 0, DemandedFromOp, Known, Depth + 1, Q)) {
723 // We can't guarantee that nsw/nuw hold after simplifying the operand.
724 I->dropPoisonGeneratingFlags();
725 return I;
726 }
727 }
728 llvm::computeKnownBits(I, Known, Depth, Q);
729 }
730 break;
731 }
732 case Instruction::LShr: {
733 const APInt *SA;
734 if (match(I->getOperand(1), m_APInt(SA))) {
735 uint64_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
736
737 // Do not simplify if lshr is part of funnel-shift pattern
738 if (I->hasOneUse()) {
739 auto *Inst = dyn_cast<Instruction>(I->user_back());
740 if (Inst && Inst->getOpcode() == BinaryOperator::Or) {
741 if (auto Opt = convertOrOfShiftsToFunnelShift(*Inst)) {
742 auto [IID, FShiftArgs] = *Opt;
743 if ((IID == Intrinsic::fshl || IID == Intrinsic::fshr) &&
744 FShiftArgs[0] == FShiftArgs[1]) {
745 llvm::computeKnownBits(I, Known, Depth, Q);
746 break;
747 }
748 }
749 }
750 }
751
752 // If we are just demanding the shifted sign bit and below, then this can
753 // be treated as an ASHR in disguise.
754 if (DemandedMask.countl_zero() >= ShiftAmt) {
755 // If we only want bits that already match the signbit then we don't
756 // need to shift.
757 unsigned NumHiDemandedBits = BitWidth - DemandedMask.countr_zero();
758 unsigned SignBits =
759 ComputeNumSignBits(I->getOperand(0), Depth + 1, Q.CxtI);
760 if (SignBits >= NumHiDemandedBits)
761 return I->getOperand(0);
762
763 // If we can pre-shift a left-shifted constant to the right without
764 // losing any low bits (we already know we don't demand the high bits),
765 // then eliminate the right-shift:
766 // (C << X) >> RightShiftAmtC --> (C >> RightShiftAmtC) << X
767 Value *X;
768 Constant *C;
769 if (match(I->getOperand(0), m_Shl(m_ImmConstant(C), m_Value(X)))) {
770 Constant *RightShiftAmtC = ConstantInt::get(VTy, ShiftAmt);
771 Constant *NewC = ConstantFoldBinaryOpOperands(Instruction::LShr, C,
772 RightShiftAmtC, DL);
773 if (ConstantFoldBinaryOpOperands(Instruction::Shl, NewC,
774 RightShiftAmtC, DL) == C) {
775 Instruction *Shl = BinaryOperator::CreateShl(NewC, X);
776 return InsertNewInstWith(Shl, I->getIterator());
777 }
778 }
779
780 const APInt *Factor;
781 if (match(I->getOperand(0),
782 m_OneUse(m_Mul(m_Value(X), m_APInt(Factor)))) &&
783 Factor->countr_zero() >= ShiftAmt) {
784 BinaryOperator *Mul = BinaryOperator::CreateMul(
785 X, ConstantInt::get(X->getType(), Factor->lshr(ShiftAmt)));
786 return InsertNewInstWith(Mul, I->getIterator());
787 }
788 }
789
790 // Unsigned shift right.
791 APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
792 if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1, Q)) {
793 // exact flag may not longer hold.
794 I->dropPoisonGeneratingFlags();
795 return I;
796 }
797 Known.Zero.lshrInPlace(ShiftAmt);
798 Known.One.lshrInPlace(ShiftAmt);
799 if (ShiftAmt)
800 Known.Zero.setHighBits(ShiftAmt); // high bits known zero.
801 } else {
802 llvm::computeKnownBits(I, Known, Depth, Q);
803 }
804 break;
805 }
806 case Instruction::AShr: {
807 unsigned SignBits = ComputeNumSignBits(I->getOperand(0), Depth + 1, Q.CxtI);
808
809 // If we only want bits that already match the signbit then we don't need
810 // to shift.
811 unsigned NumHiDemandedBits = BitWidth - DemandedMask.countr_zero();
812 if (SignBits >= NumHiDemandedBits)
813 return I->getOperand(0);
814
815 // If this is an arithmetic shift right and only the low-bit is set, we can
816 // always convert this into a logical shr, even if the shift amount is
817 // variable. The low bit of the shift cannot be an input sign bit unless
818 // the shift amount is >= the size of the datatype, which is undefined.
819 if (DemandedMask.isOne()) {
820 // Perform the logical shift right.
821 Instruction *NewVal = BinaryOperator::CreateLShr(
822 I->getOperand(0), I->getOperand(1), I->getName());
823 return InsertNewInstWith(NewVal, I->getIterator());
824 }
825
826 const APInt *SA;
827 if (match(I->getOperand(1), m_APInt(SA))) {
828 uint32_t ShiftAmt = SA->getLimitedValue(BitWidth-1);
829
830 // Signed shift right.
831 APInt DemandedMaskIn(DemandedMask.shl(ShiftAmt));
832 // If any of the bits being shifted in are demanded, then we should set
833 // the sign bit as demanded.
834 bool ShiftedInBitsDemanded = DemandedMask.countl_zero() < ShiftAmt;
835 if (ShiftedInBitsDemanded)
836 DemandedMaskIn.setSignBit();
837 if (SimplifyDemandedBits(I, 0, DemandedMaskIn, Known, Depth + 1, Q)) {
838 // exact flag may not longer hold.
839 I->dropPoisonGeneratingFlags();
840 return I;
841 }
842
843 // If the input sign bit is known to be zero, or if none of the shifted in
844 // bits are demanded, turn this into an unsigned shift right.
845 if (Known.Zero[BitWidth - 1] || !ShiftedInBitsDemanded) {
846 BinaryOperator *LShr = BinaryOperator::CreateLShr(I->getOperand(0),
847 I->getOperand(1));
848 LShr->setIsExact(cast<BinaryOperator>(I)->isExact());
849 LShr->takeName(I);
850 return InsertNewInstWith(LShr, I->getIterator());
851 }
852
853 Known = KnownBits::ashr(
854 Known, KnownBits::makeConstant(APInt(BitWidth, ShiftAmt)),
855 ShiftAmt != 0, I->isExact());
856 } else {
857 llvm::computeKnownBits(I, Known, Depth, Q);
858 }
859 break;
860 }
861 case Instruction::UDiv: {
862 // UDiv doesn't demand low bits that are zero in the divisor.
863 const APInt *SA;
864 if (match(I->getOperand(1), m_APInt(SA))) {
865 // TODO: Take the demanded mask of the result into account.
866 unsigned RHSTrailingZeros = SA->countr_zero();
867 APInt DemandedMaskIn =
868 APInt::getHighBitsSet(BitWidth, BitWidth - RHSTrailingZeros);
869 if (SimplifyDemandedBits(I, 0, DemandedMaskIn, LHSKnown, Depth + 1, Q)) {
870 // We can't guarantee that "exact" is still true after changing the
871 // the dividend.
872 I->dropPoisonGeneratingFlags();
873 return I;
874 }
875
876 Known = KnownBits::udiv(LHSKnown, KnownBits::makeConstant(*SA),
877 cast<BinaryOperator>(I)->isExact());
878 } else {
879 llvm::computeKnownBits(I, Known, Depth, Q);
880 }
881 break;
882 }
883 case Instruction::SRem: {
884 const APInt *Rem;
885 if (match(I->getOperand(1), m_APInt(Rem)) && Rem->isPowerOf2()) {
886 if (DemandedMask.ult(*Rem)) // srem won't affect demanded bits
887 return I->getOperand(0);
888
889 APInt LowBits = *Rem - 1;
890 APInt Mask2 = LowBits | APInt::getSignMask(BitWidth);
891 if (SimplifyDemandedBits(I, 0, Mask2, LHSKnown, Depth + 1, Q))
892 return I;
893 Known = KnownBits::srem(LHSKnown, KnownBits::makeConstant(*Rem));
894 break;
895 }
896
897 llvm::computeKnownBits(I, Known, Depth, Q);
898 break;
899 }
900 case Instruction::Call: {
901 bool KnownBitsComputed = false;
902 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
903 switch (II->getIntrinsicID()) {
904 case Intrinsic::abs: {
905 if (DemandedMask == 1)
906 return II->getArgOperand(0);
907 break;
908 }
909 case Intrinsic::ctpop: {
910 // Checking if the number of clear bits is odd (parity)? If the type has
911 // an even number of bits, that's the same as checking if the number of
912 // set bits is odd, so we can eliminate the 'not' op.
913 Value *X;
914 if (DemandedMask == 1 && VTy->getScalarSizeInBits() % 2 == 0 &&
915 match(II->getArgOperand(0), m_Not(m_Value(X)))) {
917 II->getModule(), Intrinsic::ctpop, VTy);
918 return InsertNewInstWith(CallInst::Create(Ctpop, {X}), I->getIterator());
919 }
920 break;
921 }
922 case Intrinsic::bswap: {
923 // If the only bits demanded come from one byte of the bswap result,
924 // just shift the input byte into position to eliminate the bswap.
925 unsigned NLZ = DemandedMask.countl_zero();
926 unsigned NTZ = DemandedMask.countr_zero();
927
928 // Round NTZ down to the next byte. If we have 11 trailing zeros, then
929 // we need all the bits down to bit 8. Likewise, round NLZ. If we
930 // have 14 leading zeros, round to 8.
931 NLZ = alignDown(NLZ, 8);
932 NTZ = alignDown(NTZ, 8);
933 // If we need exactly one byte, we can do this transformation.
934 if (BitWidth - NLZ - NTZ == 8) {
935 // Replace this with either a left or right shift to get the byte into
936 // the right place.
937 Instruction *NewVal;
938 if (NLZ > NTZ)
939 NewVal = BinaryOperator::CreateLShr(
940 II->getArgOperand(0), ConstantInt::get(VTy, NLZ - NTZ));
941 else
942 NewVal = BinaryOperator::CreateShl(
943 II->getArgOperand(0), ConstantInt::get(VTy, NTZ - NLZ));
944 NewVal->takeName(I);
945 return InsertNewInstWith(NewVal, I->getIterator());
946 }
947 break;
948 }
949 case Intrinsic::ptrmask: {
950 unsigned MaskWidth = I->getOperand(1)->getType()->getScalarSizeInBits();
951 RHSKnown = KnownBits(MaskWidth);
952 // If either the LHS or the RHS are Zero, the result is zero.
953 if (SimplifyDemandedBits(I, 0, DemandedMask, LHSKnown, Depth + 1, Q) ||
955 I, 1, (DemandedMask & ~LHSKnown.Zero).zextOrTrunc(MaskWidth),
956 RHSKnown, Depth + 1, Q))
957 return I;
958
959 // TODO: Should be 1-extend
960 RHSKnown = RHSKnown.anyextOrTrunc(BitWidth);
961
962 Known = LHSKnown & RHSKnown;
963 KnownBitsComputed = true;
964
965 // If the client is only demanding bits we know to be zero, return
966 // `llvm.ptrmask(p, 0)`. We can't return `null` here due to pointer
967 // provenance, but making the mask zero will be easily optimizable in
968 // the backend.
969 if (DemandedMask.isSubsetOf(Known.Zero) &&
970 !match(I->getOperand(1), m_Zero()))
971 return replaceOperand(
972 *I, 1, Constant::getNullValue(I->getOperand(1)->getType()));
973
974 // Mask in demanded space does nothing.
975 // NOTE: We may have attributes associated with the return value of the
976 // llvm.ptrmask intrinsic that will be lost when we just return the
977 // operand. We should try to preserve them.
978 if (DemandedMask.isSubsetOf(RHSKnown.One | LHSKnown.Zero))
979 return I->getOperand(0);
980
981 // If the RHS is a constant, see if we can simplify it.
983 I, 1, (DemandedMask & ~LHSKnown.Zero).zextOrTrunc(MaskWidth)))
984 return I;
985
986 // Combine:
987 // (ptrmask (getelementptr i8, ptr p, imm i), imm mask)
988 // -> (ptrmask (getelementptr i8, ptr p, imm (i & mask)), imm mask)
989 // where only the low bits known to be zero in the pointer are changed
990 Value *InnerPtr;
991 uint64_t GEPIndex;
992 uint64_t PtrMaskImmediate;
993 if (match(I, m_Intrinsic<Intrinsic::ptrmask>(
994 m_PtrAdd(m_Value(InnerPtr), m_ConstantInt(GEPIndex)),
995 m_ConstantInt(PtrMaskImmediate)))) {
996
997 LHSKnown = computeKnownBits(InnerPtr, Depth + 1, I);
998 if (!LHSKnown.isZero()) {
999 const unsigned trailingZeros = LHSKnown.countMinTrailingZeros();
1000 uint64_t PointerAlignBits = (uint64_t(1) << trailingZeros) - 1;
1001
1002 uint64_t HighBitsGEPIndex = GEPIndex & ~PointerAlignBits;
1003 uint64_t MaskedLowBitsGEPIndex =
1004 GEPIndex & PointerAlignBits & PtrMaskImmediate;
1005
1006 uint64_t MaskedGEPIndex = HighBitsGEPIndex | MaskedLowBitsGEPIndex;
1007
1008 if (MaskedGEPIndex != GEPIndex) {
1009 auto *GEP = cast<GEPOperator>(II->getArgOperand(0));
1011 Type *GEPIndexType =
1012 DL.getIndexType(GEP->getPointerOperand()->getType());
1013 Value *MaskedGEP = Builder.CreateGEP(
1014 GEP->getSourceElementType(), InnerPtr,
1015 ConstantInt::get(GEPIndexType, MaskedGEPIndex),
1016 GEP->getName(), GEP->isInBounds());
1017
1018 replaceOperand(*I, 0, MaskedGEP);
1019 return I;
1020 }
1021 }
1022 }
1023
1024 break;
1025 }
1026
1027 case Intrinsic::fshr:
1028 case Intrinsic::fshl: {
1029 const APInt *SA;
1030 if (!match(I->getOperand(2), m_APInt(SA)))
1031 break;
1032
1033 // Normalize to funnel shift left. APInt shifts of BitWidth are well-
1034 // defined, so no need to special-case zero shifts here.
1035 uint64_t ShiftAmt = SA->urem(BitWidth);
1036 if (II->getIntrinsicID() == Intrinsic::fshr)
1037 ShiftAmt = BitWidth - ShiftAmt;
1038
1039 APInt DemandedMaskLHS(DemandedMask.lshr(ShiftAmt));
1040 APInt DemandedMaskRHS(DemandedMask.shl(BitWidth - ShiftAmt));
1041 if (I->getOperand(0) != I->getOperand(1)) {
1042 if (SimplifyDemandedBits(I, 0, DemandedMaskLHS, LHSKnown, Depth + 1,
1043 Q) ||
1044 SimplifyDemandedBits(I, 1, DemandedMaskRHS, RHSKnown, Depth + 1,
1045 Q)) {
1046 // Range attribute may no longer hold.
1047 I->dropPoisonGeneratingReturnAttributes();
1048 return I;
1049 }
1050 } else { // fshl is a rotate
1051 // Avoid converting rotate into funnel shift.
1052 // Only simplify if one operand is constant.
1053 LHSKnown = computeKnownBits(I->getOperand(0), Depth + 1, I);
1054 if (DemandedMaskLHS.isSubsetOf(LHSKnown.Zero | LHSKnown.One) &&
1055 !match(I->getOperand(0), m_SpecificInt(LHSKnown.One))) {
1056 replaceOperand(*I, 0, Constant::getIntegerValue(VTy, LHSKnown.One));
1057 return I;
1058 }
1059
1060 RHSKnown = computeKnownBits(I->getOperand(1), Depth + 1, I);
1061 if (DemandedMaskRHS.isSubsetOf(RHSKnown.Zero | RHSKnown.One) &&
1062 !match(I->getOperand(1), m_SpecificInt(RHSKnown.One))) {
1063 replaceOperand(*I, 1, Constant::getIntegerValue(VTy, RHSKnown.One));
1064 return I;
1065 }
1066 }
1067
1068 Known.Zero = LHSKnown.Zero.shl(ShiftAmt) |
1069 RHSKnown.Zero.lshr(BitWidth - ShiftAmt);
1070 Known.One = LHSKnown.One.shl(ShiftAmt) |
1071 RHSKnown.One.lshr(BitWidth - ShiftAmt);
1072 KnownBitsComputed = true;
1073 break;
1074 }
1075 case Intrinsic::umax: {
1076 // UMax(A, C) == A if ...
1077 // The lowest non-zero bit of DemandMask is higher than the highest
1078 // non-zero bit of C.
1079 const APInt *C;
1080 unsigned CTZ = DemandedMask.countr_zero();
1081 if (match(II->getArgOperand(1), m_APInt(C)) &&
1082 CTZ >= C->getActiveBits())
1083 return II->getArgOperand(0);
1084 break;
1085 }
1086 case Intrinsic::umin: {
1087 // UMin(A, C) == A if ...
1088 // The lowest non-zero bit of DemandMask is higher than the highest
1089 // non-one bit of C.
1090 // This comes from using DeMorgans on the above umax example.
1091 const APInt *C;
1092 unsigned CTZ = DemandedMask.countr_zero();
1093 if (match(II->getArgOperand(1), m_APInt(C)) &&
1094 CTZ >= C->getBitWidth() - C->countl_one())
1095 return II->getArgOperand(0);
1096 break;
1097 }
1098 default: {
1099 // Handle target specific intrinsics
1100 std::optional<Value *> V = targetSimplifyDemandedUseBitsIntrinsic(
1101 *II, DemandedMask, Known, KnownBitsComputed);
1102 if (V)
1103 return *V;
1104 break;
1105 }
1106 }
1107 }
1108
1109 if (!KnownBitsComputed)
1110 llvm::computeKnownBits(I, Known, Depth, Q);
1111 break;
1112 }
1113 }
1114
1115 if (I->getType()->isPointerTy()) {
1116 Align Alignment = I->getPointerAlignment(DL);
1117 Known.Zero.setLowBits(Log2(Alignment));
1118 }
1119
1120 // If the client is only demanding bits that we know, return the known
1121 // constant. We can't directly simplify pointers as a constant because of
1122 // pointer provenance.
1123 // TODO: We could return `(inttoptr const)` for pointers.
1124 if (!I->getType()->isPointerTy() &&
1125 DemandedMask.isSubsetOf(Known.Zero | Known.One))
1126 return Constant::getIntegerValue(VTy, Known.One);
1127
1128 if (VerifyKnownBits) {
1129 KnownBits ReferenceKnown = llvm::computeKnownBits(I, Depth, Q);
1130 if (Known != ReferenceKnown) {
1131 errs() << "Mismatched known bits for " << *I << " in "
1132 << I->getFunction()->getName() << "\n";
1133 errs() << "computeKnownBits(): " << ReferenceKnown << "\n";
1134 errs() << "SimplifyDemandedBits(): " << Known << "\n";
1135 std::abort();
1136 }
1137 }
1138
1139 return nullptr;
1140}
1141
1142/// Helper routine of SimplifyDemandedUseBits. It computes Known
1143/// bits. It also tries to handle simplifications that can be done based on
1144/// DemandedMask, but without modifying the Instruction.
1146 Instruction *I, const APInt &DemandedMask, KnownBits &Known, unsigned Depth,
1147 const SimplifyQuery &Q) {
1148 unsigned BitWidth = DemandedMask.getBitWidth();
1149 Type *ITy = I->getType();
1150
1151 KnownBits LHSKnown(BitWidth);
1152 KnownBits RHSKnown(BitWidth);
1153
1154 // Despite the fact that we can't simplify this instruction in all User's
1155 // context, we can at least compute the known bits, and we can
1156 // do simplifications that apply to *just* the one user if we know that
1157 // this instruction has a simpler value in that context.
1158 switch (I->getOpcode()) {
1159 case Instruction::And: {
1160 llvm::computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, Q);
1161 llvm::computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, Q);
1162 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
1163 Depth, Q);
1165
1166 // If the client is only demanding bits that we know, return the known
1167 // constant.
1168 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
1169 return Constant::getIntegerValue(ITy, Known.One);
1170
1171 // If all of the demanded bits are known 1 on one side, return the other.
1172 // These bits cannot contribute to the result of the 'and' in this context.
1173 if (DemandedMask.isSubsetOf(LHSKnown.Zero | RHSKnown.One))
1174 return I->getOperand(0);
1175 if (DemandedMask.isSubsetOf(RHSKnown.Zero | LHSKnown.One))
1176 return I->getOperand(1);
1177
1178 break;
1179 }
1180 case Instruction::Or: {
1181 llvm::computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, Q);
1182 llvm::computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, Q);
1183 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
1184 Depth, Q);
1186
1187 // If the client is only demanding bits that we know, return the known
1188 // constant.
1189 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
1190 return Constant::getIntegerValue(ITy, Known.One);
1191
1192 // We can simplify (X|Y) -> X or Y in the user's context if we know that
1193 // only bits from X or Y are demanded.
1194 // If all of the demanded bits are known zero on one side, return the other.
1195 // These bits cannot contribute to the result of the 'or' in this context.
1196 if (DemandedMask.isSubsetOf(LHSKnown.One | RHSKnown.Zero))
1197 return I->getOperand(0);
1198 if (DemandedMask.isSubsetOf(RHSKnown.One | LHSKnown.Zero))
1199 return I->getOperand(1);
1200
1201 break;
1202 }
1203 case Instruction::Xor: {
1204 llvm::computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, Q);
1205 llvm::computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, Q);
1206 Known = analyzeKnownBitsFromAndXorOr(cast<Operator>(I), LHSKnown, RHSKnown,
1207 Depth, Q);
1209
1210 // If the client is only demanding bits that we know, return the known
1211 // constant.
1212 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
1213 return Constant::getIntegerValue(ITy, Known.One);
1214
1215 // We can simplify (X^Y) -> X or Y in the user's context if we know that
1216 // only bits from X or Y are demanded.
1217 // If all of the demanded bits are known zero on one side, return the other.
1218 if (DemandedMask.isSubsetOf(RHSKnown.Zero))
1219 return I->getOperand(0);
1220 if (DemandedMask.isSubsetOf(LHSKnown.Zero))
1221 return I->getOperand(1);
1222
1223 break;
1224 }
1225 case Instruction::Add: {
1226 unsigned NLZ = DemandedMask.countl_zero();
1227 APInt DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
1228
1229 // If an operand adds zeros to every bit below the highest demanded bit,
1230 // that operand doesn't change the result. Return the other side.
1231 llvm::computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, Q);
1232 if (DemandedFromOps.isSubsetOf(RHSKnown.Zero))
1233 return I->getOperand(0);
1234
1235 llvm::computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, Q);
1236 if (DemandedFromOps.isSubsetOf(LHSKnown.Zero))
1237 return I->getOperand(1);
1238
1239 bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
1240 bool NUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
1241 Known = KnownBits::add(LHSKnown, RHSKnown, NSW, NUW);
1243 break;
1244 }
1245 case Instruction::Sub: {
1246 unsigned NLZ = DemandedMask.countl_zero();
1247 APInt DemandedFromOps = APInt::getLowBitsSet(BitWidth, BitWidth - NLZ);
1248
1249 // If an operand subtracts zeros from every bit below the highest demanded
1250 // bit, that operand doesn't change the result. Return the other side.
1251 llvm::computeKnownBits(I->getOperand(1), RHSKnown, Depth + 1, Q);
1252 if (DemandedFromOps.isSubsetOf(RHSKnown.Zero))
1253 return I->getOperand(0);
1254
1255 bool NSW = cast<OverflowingBinaryOperator>(I)->hasNoSignedWrap();
1256 bool NUW = cast<OverflowingBinaryOperator>(I)->hasNoUnsignedWrap();
1257 llvm::computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, Q);
1258 Known = KnownBits::sub(LHSKnown, RHSKnown, NSW, NUW);
1260 break;
1261 }
1262 case Instruction::AShr: {
1263 // Compute the Known bits to simplify things downstream.
1264 llvm::computeKnownBits(I, Known, Depth, Q);
1265
1266 // If this user is only demanding bits that we know, return the known
1267 // constant.
1268 if (DemandedMask.isSubsetOf(Known.Zero | Known.One))
1269 return Constant::getIntegerValue(ITy, Known.One);
1270
1271 // If the right shift operand 0 is a result of a left shift by the same
1272 // amount, this is probably a zero/sign extension, which may be unnecessary,
1273 // if we do not demand any of the new sign bits. So, return the original
1274 // operand instead.
1275 const APInt *ShiftRC;
1276 const APInt *ShiftLC;
1277 Value *X;
1278 unsigned BitWidth = DemandedMask.getBitWidth();
1279 if (match(I,
1280 m_AShr(m_Shl(m_Value(X), m_APInt(ShiftLC)), m_APInt(ShiftRC))) &&
1281 ShiftLC == ShiftRC && ShiftLC->ult(BitWidth) &&
1282 DemandedMask.isSubsetOf(APInt::getLowBitsSet(
1283 BitWidth, BitWidth - ShiftRC->getZExtValue()))) {
1284 return X;
1285 }
1286
1287 break;
1288 }
1289 default:
1290 // Compute the Known bits to simplify things downstream.
1291 llvm::computeKnownBits(I, Known, Depth, Q);
1292
1293 // If this user is only demanding bits that we know, return the known
1294 // constant.
1295 if (DemandedMask.isSubsetOf(Known.Zero|Known.One))
1296 return Constant::getIntegerValue(ITy, Known.One);
1297
1298 break;
1299 }
1300
1301 return nullptr;
1302}
1303
1304/// Helper routine of SimplifyDemandedUseBits. It tries to simplify
1305/// "E1 = (X lsr C1) << C2", where the C1 and C2 are constant, into
1306/// "E2 = X << (C2 - C1)" or "E2 = X >> (C1 - C2)", depending on the sign
1307/// of "C2-C1".
1308///
1309/// Suppose E1 and E2 are generally different in bits S={bm, bm+1,
1310/// ..., bn}, without considering the specific value X is holding.
1311/// This transformation is legal iff one of following conditions is hold:
1312/// 1) All the bit in S are 0, in this case E1 == E2.
1313/// 2) We don't care those bits in S, per the input DemandedMask.
1314/// 3) Combination of 1) and 2). Some bits in S are 0, and we don't care the
1315/// rest bits.
1316///
1317/// Currently we only test condition 2).
1318///
1319/// As with SimplifyDemandedUseBits, it returns NULL if the simplification was
1320/// not successful.
1322 Instruction *Shr, const APInt &ShrOp1, Instruction *Shl,
1323 const APInt &ShlOp1, const APInt &DemandedMask, KnownBits &Known) {
1324 if (!ShlOp1 || !ShrOp1)
1325 return nullptr; // No-op.
1326
1327 Value *VarX = Shr->getOperand(0);
1328 Type *Ty = VarX->getType();
1329 unsigned BitWidth = Ty->getScalarSizeInBits();
1330 if (ShlOp1.uge(BitWidth) || ShrOp1.uge(BitWidth))
1331 return nullptr; // Undef.
1332
1333 unsigned ShlAmt = ShlOp1.getZExtValue();
1334 unsigned ShrAmt = ShrOp1.getZExtValue();
1335
1336 Known.One.clearAllBits();
1337 Known.Zero.setLowBits(ShlAmt - 1);
1338 Known.Zero &= DemandedMask;
1339
1340 APInt BitMask1(APInt::getAllOnes(BitWidth));
1341 APInt BitMask2(APInt::getAllOnes(BitWidth));
1342
1343 bool isLshr = (Shr->getOpcode() == Instruction::LShr);
1344 BitMask1 = isLshr ? (BitMask1.lshr(ShrAmt) << ShlAmt) :
1345 (BitMask1.ashr(ShrAmt) << ShlAmt);
1346
1347 if (ShrAmt <= ShlAmt) {
1348 BitMask2 <<= (ShlAmt - ShrAmt);
1349 } else {
1350 BitMask2 = isLshr ? BitMask2.lshr(ShrAmt - ShlAmt):
1351 BitMask2.ashr(ShrAmt - ShlAmt);
1352 }
1353
1354 // Check if condition-2 (see the comment to this function) is satified.
1355 if ((BitMask1 & DemandedMask) == (BitMask2 & DemandedMask)) {
1356 if (ShrAmt == ShlAmt)
1357 return VarX;
1358
1359 if (!Shr->hasOneUse())
1360 return nullptr;
1361
1362 BinaryOperator *New;
1363 if (ShrAmt < ShlAmt) {
1364 Constant *Amt = ConstantInt::get(VarX->getType(), ShlAmt - ShrAmt);
1365 New = BinaryOperator::CreateShl(VarX, Amt);
1366 BinaryOperator *Orig = cast<BinaryOperator>(Shl);
1367 New->setHasNoSignedWrap(Orig->hasNoSignedWrap());
1368 New->setHasNoUnsignedWrap(Orig->hasNoUnsignedWrap());
1369 } else {
1370 Constant *Amt = ConstantInt::get(VarX->getType(), ShrAmt - ShlAmt);
1371 New = isLshr ? BinaryOperator::CreateLShr(VarX, Amt) :
1372 BinaryOperator::CreateAShr(VarX, Amt);
1373 if (cast<BinaryOperator>(Shr)->isExact())
1374 New->setIsExact(true);
1375 }
1376
1377 return InsertNewInstWith(New, Shl->getIterator());
1378 }
1379
1380 return nullptr;
1381}
1382
1383/// The specified value produces a vector with any number of elements.
1384/// This method analyzes which elements of the operand are poison and
1385/// returns that information in PoisonElts.
1386///
1387/// DemandedElts contains the set of elements that are actually used by the
1388/// caller, and by default (AllowMultipleUsers equals false) the value is
1389/// simplified only if it has a single caller. If AllowMultipleUsers is set
1390/// to true, DemandedElts refers to the union of sets of elements that are
1391/// used by all callers.
1392///
1393/// If the information about demanded elements can be used to simplify the
1394/// operation, the operation is simplified, then the resultant value is
1395/// returned. This returns null if no change was made.
1397 APInt DemandedElts,
1398 APInt &PoisonElts,
1399 unsigned Depth,
1400 bool AllowMultipleUsers) {
1401 // Cannot analyze scalable type. The number of vector elements is not a
1402 // compile-time constant.
1403 if (isa<ScalableVectorType>(V->getType()))
1404 return nullptr;
1405
1406 unsigned VWidth = cast<FixedVectorType>(V->getType())->getNumElements();
1407 APInt EltMask(APInt::getAllOnes(VWidth));
1408 assert((DemandedElts & ~EltMask) == 0 && "Invalid DemandedElts!");
1409
1410 if (match(V, m_Poison())) {
1411 // If the entire vector is poison, just return this info.
1412 PoisonElts = EltMask;
1413 return nullptr;
1414 }
1415
1416 if (DemandedElts.isZero()) { // If nothing is demanded, provide poison.
1417 PoisonElts = EltMask;
1418 return PoisonValue::get(V->getType());
1419 }
1420
1421 PoisonElts = 0;
1422
1423 if (auto *C = dyn_cast<Constant>(V)) {
1424 // Check if this is identity. If so, return 0 since we are not simplifying
1425 // anything.
1426 if (DemandedElts.isAllOnes())
1427 return nullptr;
1428
1429 Type *EltTy = cast<VectorType>(V->getType())->getElementType();
1432 for (unsigned i = 0; i != VWidth; ++i) {
1433 if (!DemandedElts[i]) { // If not demanded, set to poison.
1434 Elts.push_back(Poison);
1435 PoisonElts.setBit(i);
1436 continue;
1437 }
1438
1439 Constant *Elt = C->getAggregateElement(i);
1440 if (!Elt) return nullptr;
1441
1442 Elts.push_back(Elt);
1443 if (isa<PoisonValue>(Elt)) // Already poison.
1444 PoisonElts.setBit(i);
1445 }
1446
1447 // If we changed the constant, return it.
1448 Constant *NewCV = ConstantVector::get(Elts);
1449 return NewCV != C ? NewCV : nullptr;
1450 }
1451
1452 // Limit search depth.
1454 return nullptr;
1455
1456 if (!AllowMultipleUsers) {
1457 // If multiple users are using the root value, proceed with
1458 // simplification conservatively assuming that all elements
1459 // are needed.
1460 if (!V->hasOneUse()) {
1461 // Quit if we find multiple users of a non-root value though.
1462 // They'll be handled when it's their turn to be visited by
1463 // the main instcombine process.
1464 if (Depth != 0)
1465 // TODO: Just compute the PoisonElts information recursively.
1466 return nullptr;
1467
1468 // Conservatively assume that all elements are needed.
1469 DemandedElts = EltMask;
1470 }
1471 }
1472
1473 Instruction *I = dyn_cast<Instruction>(V);
1474 if (!I) return nullptr; // Only analyze instructions.
1475
1476 bool MadeChange = false;
1477 auto simplifyAndSetOp = [&](Instruction *Inst, unsigned OpNum,
1478 APInt Demanded, APInt &Undef) {
1479 auto *II = dyn_cast<IntrinsicInst>(Inst);
1480 Value *Op = II ? II->getArgOperand(OpNum) : Inst->getOperand(OpNum);
1481 if (Value *V = SimplifyDemandedVectorElts(Op, Demanded, Undef, Depth + 1)) {
1482 replaceOperand(*Inst, OpNum, V);
1483 MadeChange = true;
1484 }
1485 };
1486
1487 APInt PoisonElts2(VWidth, 0);
1488 APInt PoisonElts3(VWidth, 0);
1489 switch (I->getOpcode()) {
1490 default: break;
1491
1492 case Instruction::GetElementPtr: {
1493 // The LangRef requires that struct geps have all constant indices. As
1494 // such, we can't convert any operand to partial undef.
1495 auto mayIndexStructType = [](GetElementPtrInst &GEP) {
1496 for (auto I = gep_type_begin(GEP), E = gep_type_end(GEP);
1497 I != E; I++)
1498 if (I.isStruct())
1499 return true;
1500 return false;
1501 };
1502 if (mayIndexStructType(cast<GetElementPtrInst>(*I)))
1503 break;
1504
1505 // Conservatively track the demanded elements back through any vector
1506 // operands we may have. We know there must be at least one, or we
1507 // wouldn't have a vector result to get here. Note that we intentionally
1508 // merge the undef bits here since gepping with either an poison base or
1509 // index results in poison.
1510 for (unsigned i = 0; i < I->getNumOperands(); i++) {
1511 if (i == 0 ? match(I->getOperand(i), m_Undef())
1512 : match(I->getOperand(i), m_Poison())) {
1513 // If the entire vector is undefined, just return this info.
1514 PoisonElts = EltMask;
1515 return nullptr;
1516 }
1517 if (I->getOperand(i)->getType()->isVectorTy()) {
1518 APInt PoisonEltsOp(VWidth, 0);
1519 simplifyAndSetOp(I, i, DemandedElts, PoisonEltsOp);
1520 // gep(x, undef) is not undef, so skip considering idx ops here
1521 // Note that we could propagate poison, but we can't distinguish between
1522 // undef & poison bits ATM
1523 if (i == 0)
1524 PoisonElts |= PoisonEltsOp;
1525 }
1526 }
1527
1528 break;
1529 }
1530 case Instruction::InsertElement: {
1531 // If this is a variable index, we don't know which element it overwrites.
1532 // demand exactly the same input as we produce.
1533 ConstantInt *Idx = dyn_cast<ConstantInt>(I->getOperand(2));
1534 if (!Idx) {
1535 // Note that we can't propagate undef elt info, because we don't know
1536 // which elt is getting updated.
1537 simplifyAndSetOp(I, 0, DemandedElts, PoisonElts2);
1538 break;
1539 }
1540
1541 // The element inserted overwrites whatever was there, so the input demanded
1542 // set is simpler than the output set.
1543 unsigned IdxNo = Idx->getZExtValue();
1544 APInt PreInsertDemandedElts = DemandedElts;
1545 if (IdxNo < VWidth)
1546 PreInsertDemandedElts.clearBit(IdxNo);
1547
1548 // If we only demand the element that is being inserted and that element
1549 // was extracted from the same index in another vector with the same type,
1550 // replace this insert with that other vector.
1551 // Note: This is attempted before the call to simplifyAndSetOp because that
1552 // may change PoisonElts to a value that does not match with Vec.
1553 Value *Vec;
1554 if (PreInsertDemandedElts == 0 &&
1555 match(I->getOperand(1),
1556 m_ExtractElt(m_Value(Vec), m_SpecificInt(IdxNo))) &&
1557 Vec->getType() == I->getType()) {
1558 return Vec;
1559 }
1560
1561 simplifyAndSetOp(I, 0, PreInsertDemandedElts, PoisonElts);
1562
1563 // If this is inserting an element that isn't demanded, remove this
1564 // insertelement.
1565 if (IdxNo >= VWidth || !DemandedElts[IdxNo]) {
1566 Worklist.push(I);
1567 return I->getOperand(0);
1568 }
1569
1570 // The inserted element is defined.
1571 PoisonElts.clearBit(IdxNo);
1572 break;
1573 }
1574 case Instruction::ShuffleVector: {
1575 auto *Shuffle = cast<ShuffleVectorInst>(I);
1576 assert(Shuffle->getOperand(0)->getType() ==
1577 Shuffle->getOperand(1)->getType() &&
1578 "Expected shuffle operands to have same type");
1579 unsigned OpWidth = cast<FixedVectorType>(Shuffle->getOperand(0)->getType())
1580 ->getNumElements();
1581 // Handle trivial case of a splat. Only check the first element of LHS
1582 // operand.
1583 if (all_of(Shuffle->getShuffleMask(), [](int Elt) { return Elt == 0; }) &&
1584 DemandedElts.isAllOnes()) {
1585 if (!isa<PoisonValue>(I->getOperand(1))) {
1586 I->setOperand(1, PoisonValue::get(I->getOperand(1)->getType()));
1587 MadeChange = true;
1588 }
1589 APInt LeftDemanded(OpWidth, 1);
1590 APInt LHSPoisonElts(OpWidth, 0);
1591 simplifyAndSetOp(I, 0, LeftDemanded, LHSPoisonElts);
1592 if (LHSPoisonElts[0])
1593 PoisonElts = EltMask;
1594 else
1595 PoisonElts.clearAllBits();
1596 break;
1597 }
1598
1599 APInt LeftDemanded(OpWidth, 0), RightDemanded(OpWidth, 0);
1600 for (unsigned i = 0; i < VWidth; i++) {
1601 if (DemandedElts[i]) {
1602 unsigned MaskVal = Shuffle->getMaskValue(i);
1603 if (MaskVal != -1u) {
1604 assert(MaskVal < OpWidth * 2 &&
1605 "shufflevector mask index out of range!");
1606 if (MaskVal < OpWidth)
1607 LeftDemanded.setBit(MaskVal);
1608 else
1609 RightDemanded.setBit(MaskVal - OpWidth);
1610 }
1611 }
1612 }
1613
1614 APInt LHSPoisonElts(OpWidth, 0);
1615 simplifyAndSetOp(I, 0, LeftDemanded, LHSPoisonElts);
1616
1617 APInt RHSPoisonElts(OpWidth, 0);
1618 simplifyAndSetOp(I, 1, RightDemanded, RHSPoisonElts);
1619
1620 // If this shuffle does not change the vector length and the elements
1621 // demanded by this shuffle are an identity mask, then this shuffle is
1622 // unnecessary.
1623 //
1624 // We are assuming canonical form for the mask, so the source vector is
1625 // operand 0 and operand 1 is not used.
1626 //
1627 // Note that if an element is demanded and this shuffle mask is undefined
1628 // for that element, then the shuffle is not considered an identity
1629 // operation. The shuffle prevents poison from the operand vector from
1630 // leaking to the result by replacing poison with an undefined value.
1631 if (VWidth == OpWidth) {
1632 bool IsIdentityShuffle = true;
1633 for (unsigned i = 0; i < VWidth; i++) {
1634 unsigned MaskVal = Shuffle->getMaskValue(i);
1635 if (DemandedElts[i] && i != MaskVal) {
1636 IsIdentityShuffle = false;
1637 break;
1638 }
1639 }
1640 if (IsIdentityShuffle)
1641 return Shuffle->getOperand(0);
1642 }
1643
1644 bool NewPoisonElts = false;
1645 unsigned LHSIdx = -1u, LHSValIdx = -1u;
1646 unsigned RHSIdx = -1u, RHSValIdx = -1u;
1647 bool LHSUniform = true;
1648 bool RHSUniform = true;
1649 for (unsigned i = 0; i < VWidth; i++) {
1650 unsigned MaskVal = Shuffle->getMaskValue(i);
1651 if (MaskVal == -1u) {
1652 PoisonElts.setBit(i);
1653 } else if (!DemandedElts[i]) {
1654 NewPoisonElts = true;
1655 PoisonElts.setBit(i);
1656 } else if (MaskVal < OpWidth) {
1657 if (LHSPoisonElts[MaskVal]) {
1658 NewPoisonElts = true;
1659 PoisonElts.setBit(i);
1660 } else {
1661 LHSIdx = LHSIdx == -1u ? i : OpWidth;
1662 LHSValIdx = LHSValIdx == -1u ? MaskVal : OpWidth;
1663 LHSUniform = LHSUniform && (MaskVal == i);
1664 }
1665 } else {
1666 if (RHSPoisonElts[MaskVal - OpWidth]) {
1667 NewPoisonElts = true;
1668 PoisonElts.setBit(i);
1669 } else {
1670 RHSIdx = RHSIdx == -1u ? i : OpWidth;
1671 RHSValIdx = RHSValIdx == -1u ? MaskVal - OpWidth : OpWidth;
1672 RHSUniform = RHSUniform && (MaskVal - OpWidth == i);
1673 }
1674 }
1675 }
1676
1677 // Try to transform shuffle with constant vector and single element from
1678 // this constant vector to single insertelement instruction.
1679 // shufflevector V, C, <v1, v2, .., ci, .., vm> ->
1680 // insertelement V, C[ci], ci-n
1681 if (OpWidth ==
1682 cast<FixedVectorType>(Shuffle->getType())->getNumElements()) {
1683 Value *Op = nullptr;
1684 Constant *Value = nullptr;
1685 unsigned Idx = -1u;
1686
1687 // Find constant vector with the single element in shuffle (LHS or RHS).
1688 if (LHSIdx < OpWidth && RHSUniform) {
1689 if (auto *CV = dyn_cast<ConstantVector>(Shuffle->getOperand(0))) {
1690 Op = Shuffle->getOperand(1);
1691 Value = CV->getOperand(LHSValIdx);
1692 Idx = LHSIdx;
1693 }
1694 }
1695 if (RHSIdx < OpWidth && LHSUniform) {
1696 if (auto *CV = dyn_cast<ConstantVector>(Shuffle->getOperand(1))) {
1697 Op = Shuffle->getOperand(0);
1698 Value = CV->getOperand(RHSValIdx);
1699 Idx = RHSIdx;
1700 }
1701 }
1702 // Found constant vector with single element - convert to insertelement.
1703 if (Op && Value) {
1705 Op, Value, ConstantInt::get(Type::getInt64Ty(I->getContext()), Idx),
1706 Shuffle->getName());
1707 InsertNewInstWith(New, Shuffle->getIterator());
1708 return New;
1709 }
1710 }
1711 if (NewPoisonElts) {
1712 // Add additional discovered undefs.
1714 for (unsigned i = 0; i < VWidth; ++i) {
1715 if (PoisonElts[i])
1717 else
1718 Elts.push_back(Shuffle->getMaskValue(i));
1719 }
1720 Shuffle->setShuffleMask(Elts);
1721 MadeChange = true;
1722 }
1723 break;
1724 }
1725 case Instruction::Select: {
1726 // If this is a vector select, try to transform the select condition based
1727 // on the current demanded elements.
1728 SelectInst *Sel = cast<SelectInst>(I);
1729 if (Sel->getCondition()->getType()->isVectorTy()) {
1730 // TODO: We are not doing anything with PoisonElts based on this call.
1731 // It is overwritten below based on the other select operands. If an
1732 // element of the select condition is known undef, then we are free to
1733 // choose the output value from either arm of the select. If we know that
1734 // one of those values is undef, then the output can be undef.
1735 simplifyAndSetOp(I, 0, DemandedElts, PoisonElts);
1736 }
1737
1738 // Next, see if we can transform the arms of the select.
1739 APInt DemandedLHS(DemandedElts), DemandedRHS(DemandedElts);
1740 if (auto *CV = dyn_cast<ConstantVector>(Sel->getCondition())) {
1741 for (unsigned i = 0; i < VWidth; i++) {
1742 Constant *CElt = CV->getAggregateElement(i);
1743
1744 // isNullValue() always returns false when called on a ConstantExpr.
1745 if (CElt->isNullValue())
1746 DemandedLHS.clearBit(i);
1747 else if (CElt->isOneValue())
1748 DemandedRHS.clearBit(i);
1749 }
1750 }
1751
1752 simplifyAndSetOp(I, 1, DemandedLHS, PoisonElts2);
1753 simplifyAndSetOp(I, 2, DemandedRHS, PoisonElts3);
1754
1755 // Output elements are undefined if the element from each arm is undefined.
1756 // TODO: This can be improved. See comment in select condition handling.
1757 PoisonElts = PoisonElts2 & PoisonElts3;
1758 break;
1759 }
1760 case Instruction::BitCast: {
1761 // Vector->vector casts only.
1762 VectorType *VTy = dyn_cast<VectorType>(I->getOperand(0)->getType());
1763 if (!VTy) break;
1764 unsigned InVWidth = cast<FixedVectorType>(VTy)->getNumElements();
1765 APInt InputDemandedElts(InVWidth, 0);
1766 PoisonElts2 = APInt(InVWidth, 0);
1767 unsigned Ratio;
1768
1769 if (VWidth == InVWidth) {
1770 // If we are converting from <4 x i32> -> <4 x f32>, we demand the same
1771 // elements as are demanded of us.
1772 Ratio = 1;
1773 InputDemandedElts = DemandedElts;
1774 } else if ((VWidth % InVWidth) == 0) {
1775 // If the number of elements in the output is a multiple of the number of
1776 // elements in the input then an input element is live if any of the
1777 // corresponding output elements are live.
1778 Ratio = VWidth / InVWidth;
1779 for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx)
1780 if (DemandedElts[OutIdx])
1781 InputDemandedElts.setBit(OutIdx / Ratio);
1782 } else if ((InVWidth % VWidth) == 0) {
1783 // If the number of elements in the input is a multiple of the number of
1784 // elements in the output then an input element is live if the
1785 // corresponding output element is live.
1786 Ratio = InVWidth / VWidth;
1787 for (unsigned InIdx = 0; InIdx != InVWidth; ++InIdx)
1788 if (DemandedElts[InIdx / Ratio])
1789 InputDemandedElts.setBit(InIdx);
1790 } else {
1791 // Unsupported so far.
1792 break;
1793 }
1794
1795 simplifyAndSetOp(I, 0, InputDemandedElts, PoisonElts2);
1796
1797 if (VWidth == InVWidth) {
1798 PoisonElts = PoisonElts2;
1799 } else if ((VWidth % InVWidth) == 0) {
1800 // If the number of elements in the output is a multiple of the number of
1801 // elements in the input then an output element is undef if the
1802 // corresponding input element is undef.
1803 for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx)
1804 if (PoisonElts2[OutIdx / Ratio])
1805 PoisonElts.setBit(OutIdx);
1806 } else if ((InVWidth % VWidth) == 0) {
1807 // If the number of elements in the input is a multiple of the number of
1808 // elements in the output then an output element is undef if all of the
1809 // corresponding input elements are undef.
1810 for (unsigned OutIdx = 0; OutIdx != VWidth; ++OutIdx) {
1811 APInt SubUndef = PoisonElts2.lshr(OutIdx * Ratio).zextOrTrunc(Ratio);
1812 if (SubUndef.popcount() == Ratio)
1813 PoisonElts.setBit(OutIdx);
1814 }
1815 } else {
1816 llvm_unreachable("Unimp");
1817 }
1818 break;
1819 }
1820 case Instruction::FPTrunc:
1821 case Instruction::FPExt:
1822 simplifyAndSetOp(I, 0, DemandedElts, PoisonElts);
1823 break;
1824
1825 case Instruction::Call: {
1826 IntrinsicInst *II = dyn_cast<IntrinsicInst>(I);
1827 if (!II) break;
1828 switch (II->getIntrinsicID()) {
1829 case Intrinsic::masked_gather: // fallthrough
1830 case Intrinsic::masked_load: {
1831 // Subtlety: If we load from a pointer, the pointer must be valid
1832 // regardless of whether the element is demanded. Doing otherwise risks
1833 // segfaults which didn't exist in the original program.
1834 APInt DemandedPtrs(APInt::getAllOnes(VWidth)),
1835 DemandedPassThrough(DemandedElts);
1836 if (auto *CV = dyn_cast<ConstantVector>(II->getOperand(2)))
1837 for (unsigned i = 0; i < VWidth; i++) {
1838 Constant *CElt = CV->getAggregateElement(i);
1839 if (CElt->isNullValue())
1840 DemandedPtrs.clearBit(i);
1841 else if (CElt->isAllOnesValue())
1842 DemandedPassThrough.clearBit(i);
1843 }
1844 if (II->getIntrinsicID() == Intrinsic::masked_gather)
1845 simplifyAndSetOp(II, 0, DemandedPtrs, PoisonElts2);
1846 simplifyAndSetOp(II, 3, DemandedPassThrough, PoisonElts3);
1847
1848 // Output elements are undefined if the element from both sources are.
1849 // TODO: can strengthen via mask as well.
1850 PoisonElts = PoisonElts2 & PoisonElts3;
1851 break;
1852 }
1853 default: {
1854 // Handle target specific intrinsics
1855 std::optional<Value *> V = targetSimplifyDemandedVectorEltsIntrinsic(
1856 *II, DemandedElts, PoisonElts, PoisonElts2, PoisonElts3,
1857 simplifyAndSetOp);
1858 if (V)
1859 return *V;
1860 break;
1861 }
1862 } // switch on IntrinsicID
1863 break;
1864 } // case Call
1865 } // switch on Opcode
1866
1867 // TODO: We bail completely on integer div/rem and shifts because they have
1868 // UB/poison potential, but that should be refined.
1869 BinaryOperator *BO;
1870 if (match(I, m_BinOp(BO)) && !BO->isIntDivRem() && !BO->isShift()) {
1871 Value *X = BO->getOperand(0);
1872 Value *Y = BO->getOperand(1);
1873
1874 // Look for an equivalent binop except that one operand has been shuffled.
1875 // If the demand for this binop only includes elements that are the same as
1876 // the other binop, then we may be able to replace this binop with a use of
1877 // the earlier one.
1878 //
1879 // Example:
1880 // %other_bo = bo (shuf X, {0}), Y
1881 // %this_extracted_bo = extelt (bo X, Y), 0
1882 // -->
1883 // %other_bo = bo (shuf X, {0}), Y
1884 // %this_extracted_bo = extelt %other_bo, 0
1885 //
1886 // TODO: Handle demand of an arbitrary single element or more than one
1887 // element instead of just element 0.
1888 // TODO: Unlike general demanded elements transforms, this should be safe
1889 // for any (div/rem/shift) opcode too.
1890 if (DemandedElts == 1 && !X->hasOneUse() && !Y->hasOneUse() &&
1891 BO->hasOneUse() ) {
1892
1893 auto findShufBO = [&](bool MatchShufAsOp0) -> User * {
1894 // Try to use shuffle-of-operand in place of an operand:
1895 // bo X, Y --> bo (shuf X), Y
1896 // bo X, Y --> bo X, (shuf Y)
1897 BinaryOperator::BinaryOps Opcode = BO->getOpcode();
1898 Value *ShufOp = MatchShufAsOp0 ? X : Y;
1899 Value *OtherOp = MatchShufAsOp0 ? Y : X;
1900 for (User *U : OtherOp->users()) {
1901 ArrayRef<int> Mask;
1902 auto Shuf = m_Shuffle(m_Specific(ShufOp), m_Value(), m_Mask(Mask));
1903 if (BO->isCommutative()
1904 ? match(U, m_c_BinOp(Opcode, Shuf, m_Specific(OtherOp)))
1905 : MatchShufAsOp0
1906 ? match(U, m_BinOp(Opcode, Shuf, m_Specific(OtherOp)))
1907 : match(U, m_BinOp(Opcode, m_Specific(OtherOp), Shuf)))
1908 if (match(Mask, m_ZeroMask()) && Mask[0] != PoisonMaskElem)
1909 if (DT.dominates(U, I))
1910 return U;
1911 }
1912 return nullptr;
1913 };
1914
1915 if (User *ShufBO = findShufBO(/* MatchShufAsOp0 */ true))
1916 return ShufBO;
1917 if (User *ShufBO = findShufBO(/* MatchShufAsOp0 */ false))
1918 return ShufBO;
1919 }
1920
1921 simplifyAndSetOp(I, 0, DemandedElts, PoisonElts);
1922 simplifyAndSetOp(I, 1, DemandedElts, PoisonElts2);
1923
1924 // Output elements are undefined if both are undefined. Consider things
1925 // like undef & 0. The result is known zero, not undef.
1926 PoisonElts &= PoisonElts2;
1927 }
1928
1929 // If we've proven all of the lanes poison, return a poison value.
1930 // TODO: Intersect w/demanded lanes
1931 if (PoisonElts.isAllOnes())
1932 return PoisonValue::get(I->getType());
1933
1934 return MadeChange ? I : nullptr;
1935}
1936
1937/// For floating-point classes that resolve to a single bit pattern, return that
1938/// value.
1940 if (Mask == fcNone)
1941 return PoisonValue::get(Ty);
1942
1943 if (Mask == fcPosZero)
1944 return Constant::getNullValue(Ty);
1945
1946 // TODO: Support aggregate types that are allowed by FPMathOperator.
1947 if (Ty->isAggregateType())
1948 return nullptr;
1949
1950 switch (Mask) {
1951 case fcNegZero:
1952 return ConstantFP::getZero(Ty, true);
1953 case fcPosInf:
1954 return ConstantFP::getInfinity(Ty);
1955 case fcNegInf:
1956 return ConstantFP::getInfinity(Ty, true);
1957 default:
1958 return nullptr;
1959 }
1960}
1961
1963 Value *V, const FPClassTest DemandedMask, KnownFPClass &Known,
1964 unsigned Depth, Instruction *CxtI) {
1965 assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
1966 Type *VTy = V->getType();
1967
1968 assert(Known == KnownFPClass() && "expected uninitialized state");
1969
1970 if (DemandedMask == fcNone)
1971 return isa<UndefValue>(V) ? nullptr : PoisonValue::get(VTy);
1972
1974 return nullptr;
1975
1976 Instruction *I = dyn_cast<Instruction>(V);
1977 if (!I) {
1978 // Handle constants and arguments
1979 Known = computeKnownFPClass(V, fcAllFlags, CxtI, Depth + 1);
1980 Value *FoldedToConst =
1981 getFPClassConstant(VTy, DemandedMask & Known.KnownFPClasses);
1982 return FoldedToConst == V ? nullptr : FoldedToConst;
1983 }
1984
1985 if (!I->hasOneUse())
1986 return nullptr;
1987
1988 // TODO: Should account for nofpclass/FastMathFlags on current instruction
1989 switch (I->getOpcode()) {
1990 case Instruction::FNeg: {
1991 if (SimplifyDemandedFPClass(I, 0, llvm::fneg(DemandedMask), Known,
1992 Depth + 1))
1993 return I;
1994 Known.fneg();
1995 break;
1996 }
1997 case Instruction::Call: {
1998 CallInst *CI = cast<CallInst>(I);
1999 switch (CI->getIntrinsicID()) {
2000 case Intrinsic::fabs:
2001 if (SimplifyDemandedFPClass(I, 0, llvm::inverse_fabs(DemandedMask), Known,
2002 Depth + 1))
2003 return I;
2004 Known.fabs();
2005 break;
2006 case Intrinsic::arithmetic_fence:
2007 if (SimplifyDemandedFPClass(I, 0, DemandedMask, Known, Depth + 1))
2008 return I;
2009 break;
2010 case Intrinsic::copysign: {
2011 // Flip on more potentially demanded classes
2012 const FPClassTest DemandedMaskAnySign = llvm::unknown_sign(DemandedMask);
2013 if (SimplifyDemandedFPClass(I, 0, DemandedMaskAnySign, Known, Depth + 1))
2014 return I;
2015
2016 if ((DemandedMask & fcPositive) == fcNone) {
2017 // Roundabout way of replacing with fneg(fabs)
2018 I->setOperand(1, ConstantFP::get(VTy, -1.0));
2019 return I;
2020 }
2021
2022 if ((DemandedMask & fcNegative) == fcNone) {
2023 // Roundabout way of replacing with fabs
2024 I->setOperand(1, ConstantFP::getZero(VTy));
2025 return I;
2026 }
2027
2028 KnownFPClass KnownSign =
2029 computeKnownFPClass(I->getOperand(1), fcAllFlags, CxtI, Depth + 1);
2030 Known.copysign(KnownSign);
2031 break;
2032 }
2033 default:
2034 Known = computeKnownFPClass(I, ~DemandedMask, CxtI, Depth + 1);
2035 break;
2036 }
2037
2038 break;
2039 }
2040 case Instruction::Select: {
2041 KnownFPClass KnownLHS, KnownRHS;
2042 if (SimplifyDemandedFPClass(I, 2, DemandedMask, KnownRHS, Depth + 1) ||
2043 SimplifyDemandedFPClass(I, 1, DemandedMask, KnownLHS, Depth + 1))
2044 return I;
2045
2046 if (KnownLHS.isKnownNever(DemandedMask))
2047 return I->getOperand(2);
2048 if (KnownRHS.isKnownNever(DemandedMask))
2049 return I->getOperand(1);
2050
2051 // TODO: Recognize clamping patterns
2052 Known = KnownLHS | KnownRHS;
2053 break;
2054 }
2055 default:
2056 Known = computeKnownFPClass(I, ~DemandedMask, CxtI, Depth + 1);
2057 break;
2058 }
2059
2060 return getFPClassConstant(VTy, DemandedMask & Known.KnownFPClasses);
2061}
2062
2064 FPClassTest DemandedMask,
2065 KnownFPClass &Known,
2066 unsigned Depth) {
2067 Use &U = I->getOperandUse(OpNo);
2068 Value *NewVal =
2069 SimplifyDemandedUseFPClass(U.get(), DemandedMask, Known, Depth, I);
2070 if (!NewVal)
2071 return false;
2072 if (Instruction *OpInst = dyn_cast<Instruction>(U))
2073 salvageDebugInfo(*OpInst);
2074
2075 replaceUse(U, NewVal);
2076 return true;
2077}
@ Poison
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 cl::opt< unsigned > SimplifyDemandedVectorEltsDepthLimit("instcombine-simplify-vector-elts-depth", cl::desc("Depth limit when simplifying vector instructions and their operands"), cl::Hidden, cl::init(10))
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
uint64_t IntrinsicInst * II
static GCMetadataPrinterRegistry::Add< OcamlGCMetadataPrinter > Y("ocaml", "ocaml 3.10-compatible collector")
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
static unsigned getNumElements(Type *Ty)
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:78
static APInt getAllOnes(unsigned numBits)
Return an APInt of a specified width with all bits set.
Definition: APInt.h:234
void clearBit(unsigned BitPosition)
Set a given bit to 0.
Definition: APInt.h:1407
static APInt getSignMask(unsigned BitWidth)
Get the SignMask for a specific bit width.
Definition: APInt.h:229
uint64_t getZExtValue() const
Get zero extended value.
Definition: APInt.h:1520
void setHighBits(unsigned hiBits)
Set the top hiBits bits.
Definition: APInt.h:1392
unsigned popcount() const
Count the number of bits set.
Definition: APInt.h:1649
APInt zextOrTrunc(unsigned width) const
Zero extend or truncate to width.
Definition: APInt.cpp:1007
unsigned getActiveBits() const
Compute the number of active bits in the value.
Definition: APInt.h:1492
APInt trunc(unsigned width) const
Truncate to new width.
Definition: APInt.cpp:910
void setBit(unsigned BitPosition)
Set the given bit to 1 whose position is given as "bitPosition".
Definition: APInt.h:1330
bool isAllOnes() const
Determine if all bits are set. This is true for zero-width values.
Definition: APInt.h:371
bool isZero() const
Determine if this value is zero, i.e. all bits are clear.
Definition: APInt.h:380
APInt urem(const APInt &RHS) const
Unsigned remainder operation.
Definition: APInt.cpp:1640
void setSignBit()
Set the sign bit to 1.
Definition: APInt.h:1340
unsigned getBitWidth() const
Return the number of bits in the APInt.
Definition: APInt.h:1468
bool ult(const APInt &RHS) const
Unsigned less than comparison.
Definition: APInt.h:1111
void clearAllBits()
Set every bit to 0.
Definition: APInt.h:1397
unsigned countr_zero() const
Count the number of trailing zero bits.
Definition: APInt.h:1618
unsigned countl_zero() const
The APInt version of std::countl_zero.
Definition: APInt.h:1577
void clearLowBits(unsigned loBits)
Set bottom loBits bits to 0.
Definition: APInt.h:1417
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:475
APInt ashr(unsigned ShiftAmt) const
Arithmetic right-shift function.
Definition: APInt.h:827
APInt shl(unsigned shiftAmt) const
Left-shift function.
Definition: APInt.h:873
bool isSubsetOf(const APInt &RHS) const
This operation checks that all bits set in this APInt are also set in RHS.
Definition: APInt.h:1257
bool isPowerOf2() const
Check if this APInt's value is a power of two greater than zero.
Definition: APInt.h:440
static APInt getLowBitsSet(unsigned numBits, unsigned loBitsSet)
Constructs an APInt value that has the bottom loBitsSet bits set.
Definition: APInt.h:306
static APInt getHighBitsSet(unsigned numBits, unsigned hiBitsSet)
Constructs an APInt value that has the top hiBitsSet bits set.
Definition: APInt.h:296
void setLowBits(unsigned loBits)
Set the bottom loBits bits.
Definition: APInt.h:1389
bool isOne() const
Determine if this is a value of 1.
Definition: APInt.h:389
void lshrInPlace(unsigned ShiftAmt)
Logical right-shift this APInt by ShiftAmt in place.
Definition: APInt.h:858
APInt lshr(unsigned shiftAmt) const
Logical right-shift function.
Definition: APInt.h:851
bool uge(const APInt &RHS) const
Unsigned greater or equal comparison.
Definition: APInt.h:1221
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:370
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="", InsertPosition InsertBefore=nullptr)
This is the base class for all instructions that perform data casts.
Definition: InstrTypes.h:444
static Constant * getInfinity(Type *Ty, bool Negative=false)
Definition: Constants.cpp:1103
static Constant * getZero(Type *Ty, bool Negative=false)
Definition: Constants.cpp:1057
This is the shared class of boolean and integer constants.
Definition: Constants.h:83
const APInt & getValue() const
Return the constant as an APInt value reference.
Definition: Constants.h:148
static Constant * get(ArrayRef< Constant * > V)
Definition: Constants.cpp:1421
This is an important base class in LLVM.
Definition: Constant.h:42
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:403
static Constant * getAllOnesValue(Type *Ty)
Definition: Constants.cpp:420
bool isOneValue() const
Returns true if the value is one.
Definition: Constants.cpp:124
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:373
Constant * getAggregateElement(unsigned Elt) const
For aggregates (struct/array/vector) return the constant that corresponds to the specified element if...
Definition: Constants.cpp:435
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:63
IntegerType * getIndexType(LLVMContext &C, unsigned AddressSpace) const
Returns the type of a GEP index in AddressSpace.
Definition: DataLayout.cpp:878
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:933
Value * CreateSExt(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:2045
Value * CreateLShr(Value *LHS, Value *RHS, const Twine &Name="", bool isExact=false)
Definition: IRBuilder.h:1480
Value * CreateGEP(Type *Ty, Value *Ptr, ArrayRef< Value * > IdxList, const Twine &Name="", GEPNoWrapFlags NW=GEPNoWrapFlags::none())
Definition: IRBuilder.h:1874
Value * CreateNot(Value *V, const Twine &Name="")
Definition: IRBuilder.h:1757
CallInst * CreateUnaryIntrinsic(Intrinsic::ID ID, Value *V, FMFSource FMFSource={}, const Twine &Name="")
Create a call to intrinsic ID with 1 operand which is mangled on its type.
Definition: IRBuilder.cpp:881
Value * CreateAnd(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1518
Value * CreateTrunc(Value *V, Type *DestTy, const Twine &Name="", bool IsNUW=false, bool IsNSW=false)
Definition: IRBuilder.h:2019
Value * CreateOr(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1540
void SetInsertPoint(BasicBlock *TheBB)
This specifies that created instructions should be appended to the end of the specified block.
Definition: IRBuilder.h:199
Value * CreateXor(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:1562
static InsertElementInst * Create(Value *Vec, Value *NewElt, Value *Idx, const Twine &NameStr="", InsertPosition InsertBefore=nullptr)
KnownFPClass computeKnownFPClass(Value *Val, FastMathFlags FMF, FPClassTest Interested=fcAllFlags, const Instruction *CtxI=nullptr, unsigned Depth=0) const
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(Instruction *I, const APInt &DemandedMask, KnownBits &Known, unsigned Depth, const SimplifyQuery &Q)
Attempts to replace I 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, const SimplifyQuery &Q)
Helper routine of SimplifyDemandedUseBits.
bool SimplifyDemandedBits(Instruction *I, unsigned Op, const APInt &DemandedMask, KnownBits &Known, unsigned Depth, const SimplifyQuery &Q) override
This form of SimplifyDemandedBits simplifies the specified instruction operand if possible,...
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:77
Instruction * replaceInstUsesWith(Instruction &I, Value *V)
A combiner-aware RAUW-like routine.
Definition: InstCombiner.h:388
void replaceUse(Use &U, Value *NewValue)
Replace use and add the previously used value to the worklist.
Definition: InstCombiner.h:420
InstructionWorklist & Worklist
A worklist of the instructions that need to be simplified.
Definition: InstCombiner.h:65
Instruction * InsertNewInstWith(Instruction *New, BasicBlock::iterator Old)
Same as InsertNewInstBefore, but also sets the debug loc.
Definition: InstCombiner.h:377
const DataLayout & DL
Definition: InstCombiner.h:76
unsigned ComputeNumSignBits(const Value *Op, unsigned Depth=0, const Instruction *CxtI=nullptr) const
Definition: InstCombiner.h:455
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:412
DominatorTree & DT
Definition: InstCombiner.h:75
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:433
BuilderTy & Builder
Definition: InstCombiner.h:61
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:291
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:299
bool isIntDivRem() const
Definition: Instruction.h:297
A wrapper class for inspecting calls to intrinsic functions.
Definition: IntrinsicInst.h:48
bool hasNoSignedWrap() const
Test whether this operation is known to never undergo signed overflow, aka the nsw property.
Definition: Operator.h:110
bool hasNoUnsignedWrap() const
Test whether this operation is known to never undergo unsigned overflow, aka the nuw property.
Definition: Operator.h:104
static PoisonValue * get(Type *T)
Static factory methods - Return an 'poison' object of the specified type.
Definition: Constants.cpp:1878
This class represents the LLVM 'select' instruction.
const Value * getCondition() const
void push_back(const T &Elt)
Definition: SmallVector.h:413
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:1196
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:270
bool isIntOrIntVectorTy() const
Return true if this is an integer type or a vector of integer types.
Definition: Type.h:243
unsigned getScalarSizeInBits() const LLVM_READONLY
If this is a vector type, return the getPrimitiveSizeInBits value for the element type.
bool isAggregateType() const
Return true if the type is an aggregate type.
Definition: Type.h:303
static IntegerType * getInt64Ty(LLVMContext &C)
static UndefValue * get(Type *T)
Static factory methods - Return an 'undef' object of the specified type.
Definition: Constants.cpp:1859
A Use represents the edge between a Value definition and its users.
Definition: Use.h:43
Value * getOperand(unsigned i) const
Definition: User.h:228
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:427
This class represents zero extension of integer types.
self_iterator getIterator()
Definition: ilist_node.h:132
#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 * getOrInsertDeclaration(Module *M, ID id, ArrayRef< Type * > Tys={})
Look up the Function declaration of the intrinsic id in the Module M.
Definition: Intrinsics.cpp:731
class_match< PoisonValue > m_Poison()
Match an arbitrary poison constant.
Definition: PatternMatch.h:160
cst_pred_ty< is_lowbit_mask > m_LowBitMask()
Match an integer or vector with only the low bit(s) set.
Definition: PatternMatch.h:673
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:982
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:885
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:168
BinaryOp_match< LHS, RHS, Instruction::Mul > m_Mul(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:864
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:299
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)
CmpClass_match< LHS, RHS, ICmpInst > m_ICmp(CmpPredicate &Pred, 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:612
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:443
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:1739
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:1683
constexpr T alignDown(U Value, V Align, W Skew=0)
Returns the largest unsigned integer less than or equal to Value and is Skew mod Align.
Definition: MathExtras.h:556
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:44
FPClassTest fneg(FPClassTest Mask)
Return the test mask which returns true if the value's sign bit is flipped.
void adjustKnownBitsForSelectArm(KnownBits &Known, Value *Cond, Value *Arm, bool Invert, unsigned Depth, const SimplifyQuery &Q)
Adjust Known for the given select Arm to include information from the select Cond.
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.
@ Mul
Product of integers.
@ Xor
Bitwise or logical XOR of integers.
@ And
Bitwise or logical AND of integers.
void computeKnownBits(const Value *V, KnownBits &Known, const DataLayout &DL, unsigned Depth=0, AssumptionCache *AC=nullptr, const Instruction *CxtI=nullptr, const DominatorTree *DT=nullptr, bool UseInstrInfo=true)
Determine which bits of V are known to be either zero or one and return them in the KnownZero/KnownOn...
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:217
gep_type_iterator gep_type_begin(const User *GEP)
unsigned Log2(Align A)
Returns the log2 of the alignment.
Definition: Alignment.h:208
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:293
KnownBits anyextOrTrunc(unsigned BitWidth) const
Return known bits for an "any" extension or truncation of the value we're tracking.
Definition: KnownBits.h:178
bool isNonNegative() const
Returns true if this value is known to be non-negative.
Definition: KnownBits.h:100
void makeNonNegative()
Make this value non-negative.
Definition: KnownBits.h:116
static KnownBits ashr(const KnownBits &LHS, const KnownBits &RHS, bool ShAmtNonZero=false, bool Exact=false)
Compute known bits for ashr(LHS, RHS).
Definition: KnownBits.cpp:428
unsigned getBitWidth() const
Get the bit width of this value.
Definition: KnownBits.h:43
void resetAll()
Resets the known state of all bits.
Definition: KnownBits.h:73
KnownBits intersectWith(const KnownBits &RHS) const
Returns KnownBits information that is known to be true for both this and RHS.
Definition: KnownBits.h:303
KnownBits sext(unsigned BitWidth) const
Return known bits for a sign extension of the value we're tracking.
Definition: KnownBits.h:172
static KnownBits add(const KnownBits &LHS, const KnownBits &RHS, bool NSW=false, bool NUW=false)
Compute knownbits resulting from addition of LHS and RHS.
Definition: KnownBits.h:336
KnownBits zextOrTrunc(unsigned BitWidth) const
Return known bits for a zero extension or truncation of the value we're tracking.
Definition: KnownBits.h:188
static KnownBits srem(const KnownBits &LHS, const KnownBits &RHS)
Compute known bits for srem(LHS, RHS).
Definition: KnownBits.cpp:1066
static KnownBits udiv(const KnownBits &LHS, const KnownBits &RHS, bool Exact=false)
Compute known bits for udiv(LHS, RHS).
Definition: KnownBits.cpp:1009
bool isNegative() const
Returns true if this value is known to be negative.
Definition: KnownBits.h:97
static KnownBits sub(const KnownBits &LHS, const KnownBits &RHS, bool NSW=false, bool NUW=false)
Compute knownbits resulting from subtraction of LHS and RHS.
Definition: KnownBits.h:342
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:285
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.
const Instruction * CxtI
Definition: SimplifyQuery.h:75
SimplifyQuery getWithInstruction(const Instruction *I) const