llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

   1 //===- CorrelatedValuePropagation.cpp - Propagate CFG-derived info --------===//
   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 implements the Correlated Value Propagation pass.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Transforms/Scalar/CorrelatedValuePropagation.h"
  14 #include "llvm/ADT/DepthFirstIterator.h"
  15 #include "llvm/ADT/SmallVector.h"
  16 #include "llvm/ADT/Statistic.h"
  17 #include "llvm/Analysis/DomTreeUpdater.h"
  18 #include "llvm/Analysis/GlobalsModRef.h"
  19 #include "llvm/Analysis/InstructionSimplify.h"
  20 #include "llvm/Analysis/LazyValueInfo.h"
  21 #include "llvm/Analysis/ValueTracking.h"
  22 #include "llvm/IR/Attributes.h"
  23 #include "llvm/IR/BasicBlock.h"
  24 #include "llvm/IR/CFG.h"
  25 #include "llvm/IR/Constant.h"
  26 #include "llvm/IR/ConstantRange.h"
  27 #include "llvm/IR/Constants.h"
  28 #include "llvm/IR/DerivedTypes.h"
  29 #include "llvm/IR/Function.h"
  30 #include "llvm/IR/IRBuilder.h"
  31 #include "llvm/IR/InstrTypes.h"
  32 #include "llvm/IR/Instruction.h"
  33 #include "llvm/IR/Instructions.h"
  34 #include "llvm/IR/IntrinsicInst.h"
  35 #include "llvm/IR/Operator.h"
  36 #include "llvm/IR/PassManager.h"
  37 #include "llvm/IR/Type.h"
  38 #include "llvm/IR/Value.h"
  39 #include "llvm/Support/Casting.h"
  40 #include "llvm/Support/CommandLine.h"
  41 #include "llvm/Transforms/Utils/Local.h"
  42 #include <cassert>
  43 #include <optional>
  44 #include <utility>
  45
  46 using namespace llvm;
  47
  48 #define DEBUG_TYPE "correlated-value-propagation"
  49
  50 static cl::opt<bool> CanonicalizeICmpPredicatesToUnsigned(
  51     "canonicalize-icmp-predicates-to-unsigned", cl::init(true), cl::Hidden,
  52     cl::desc("Enables canonicalization of signed relational predicates to "
  53              "unsigned (e.g. sgt => ugt)"));
  54
  55 STATISTIC(NumPhis,      "Number of phis propagated");
  56 STATISTIC(NumPhiCommon, "Number of phis deleted via common incoming value");
  57 STATISTIC(NumSelects,   "Number of selects propagated");
  58 STATISTIC(NumCmps,      "Number of comparisons propagated");
  59 STATISTIC(NumReturns,   "Number of return values propagated");
  60 STATISTIC(NumDeadCases, "Number of switch cases removed");
  61 STATISTIC(NumSDivSRemsNarrowed,
  62           "Number of sdivs/srems whose width was decreased");
  63 STATISTIC(NumSDivs,     "Number of sdiv converted to udiv");
  64 STATISTIC(NumUDivURemsNarrowed,
  65           "Number of udivs/urems whose width was decreased");
  66 STATISTIC(NumAShrsConverted, "Number of ashr converted to lshr");
  67 STATISTIC(NumAShrsRemoved, "Number of ashr removed");
  68 STATISTIC(NumSRems,     "Number of srem converted to urem");
  69 STATISTIC(NumSExt,      "Number of sext converted to zext");
  70 STATISTIC(NumSICmps,    "Number of signed icmp preds simplified to unsigned");
  71 STATISTIC(NumAnd,       "Number of ands removed");
  72 STATISTIC(NumNW,        "Number of no-wrap deductions");
  73 STATISTIC(NumNSW,       "Number of no-signed-wrap deductions");
  74 STATISTIC(NumNUW,       "Number of no-unsigned-wrap deductions");
  75 STATISTIC(NumAddNW,     "Number of no-wrap deductions for add");
  76 STATISTIC(NumAddNSW,    "Number of no-signed-wrap deductions for add");
  77 STATISTIC(NumAddNUW,    "Number of no-unsigned-wrap deductions for add");
  78 STATISTIC(NumSubNW,     "Number of no-wrap deductions for sub");
  79 STATISTIC(NumSubNSW,    "Number of no-signed-wrap deductions for sub");
  80 STATISTIC(NumSubNUW,    "Number of no-unsigned-wrap deductions for sub");
  81 STATISTIC(NumMulNW,     "Number of no-wrap deductions for mul");
  82 STATISTIC(NumMulNSW,    "Number of no-signed-wrap deductions for mul");
  83 STATISTIC(NumMulNUW,    "Number of no-unsigned-wrap deductions for mul");
  84 STATISTIC(NumShlNW,     "Number of no-wrap deductions for shl");
  85 STATISTIC(NumShlNSW,    "Number of no-signed-wrap deductions for shl");
  86 STATISTIC(NumShlNUW,    "Number of no-unsigned-wrap deductions for shl");
  87 STATISTIC(NumAbs,       "Number of llvm.abs intrinsics removed");
  88 STATISTIC(NumOverflows, "Number of overflow checks removed");
  89 STATISTIC(NumSaturating,
  90     "Number of saturating arithmetics converted to normal arithmetics");
  91 STATISTIC(NumNonNull, "Number of function pointer arguments marked non-null");
  92 STATISTIC(NumMinMax, "Number of llvm.[us]{min,max} intrinsics removed");
  93 STATISTIC(NumUDivURemsNarrowedExpanded,
  94           "Number of bound udiv's/urem's expanded");
  95 STATISTIC(NumZExt, "Number of non-negative deductions");
  96
  97 static Constant *getConstantAt(Value *V, Instruction *At, LazyValueInfo *LVI) {
  98   if (Constant *C = LVI->getConstant(V, At))
  99     return C;
 100
 101   // TODO: The following really should be sunk inside LVI's core algorithm, or
 102   // at least the outer shims around such.
 103   auto *C = dyn_cast<CmpInst>(V);
 104   if (!C)
 105     return nullptr;
 106
 107   Value *Op0 = C->getOperand(0);
 108   Constant *Op1 = dyn_cast<Constant>(C->getOperand(1));
 109   if (!Op1)
 110     return nullptr;
 111
 112   LazyValueInfo::Tristate Result = LVI->getPredicateAt(
 113       C->getPredicate(), Op0, Op1, At, /*UseBlockValue=*/false);
 114   if (Result == LazyValueInfo::Unknown)
 115     return nullptr;
 116
 117   return (Result == LazyValueInfo::True)
 118              ? ConstantInt::getTrue(C->getContext())
 119              : ConstantInt::getFalse(C->getContext());
 120 }
 121
 122 static bool processSelect(SelectInst *S, LazyValueInfo *LVI) {
 123   if (S->getType()->isVectorTy() || isa<Constant>(S->getCondition()))
 124     return false;
 125
 126   bool Changed = false;
 127   for (Use &U : make_early_inc_range(S->uses())) {
 128     auto *I = cast<Instruction>(U.getUser());
 129     Constant *C;
 130     if (auto *PN = dyn_cast<PHINode>(I))
 131       C = LVI->getConstantOnEdge(S->getCondition(), PN->getIncomingBlock(U),
 132                                  I->getParent(), I);
 133     else
 134       C = getConstantAt(S->getCondition(), I, LVI);
 135
 136     auto *CI = dyn_cast_or_null<ConstantInt>(C);
 137     if (!CI)
 138       continue;
 139
 140     U.set(CI->isOne() ? S->getTrueValue() : S->getFalseValue());
 141     Changed = true;
 142     ++NumSelects;
 143   }
 144
 145   if (Changed && S->use_empty())
 146     S->eraseFromParent();
 147
 148   return Changed;
 149 }
 150
 151 /// Try to simplify a phi with constant incoming values that match the edge
 152 /// values of a non-constant value on all other edges:
 153 /// bb0:
 154 ///   %isnull = icmp eq i8* %x, null
 155 ///   br i1 %isnull, label %bb2, label %bb1
 156 /// bb1:
 157 ///   br label %bb2
 158 /// bb2:
 159 ///   %r = phi i8* [ %x, %bb1 ], [ null, %bb0 ]
 160 /// -->
 161 ///   %r = %x
 162 static bool simplifyCommonValuePhi(PHINode *P, LazyValueInfo *LVI,
 163                                    DominatorTree *DT) {
 164   // Collect incoming constants and initialize possible common value.
 165   SmallVector<std::pair<Constant *, unsigned>, 4> IncomingConstants;
 166   Value *CommonValue = nullptr;
 167   for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) {
 168     Value *Incoming = P->getIncomingValue(i);
 169     if (auto *IncomingConstant = dyn_cast<Constant>(Incoming)) {
 170       IncomingConstants.push_back(std::make_pair(IncomingConstant, i));
 171     } else if (!CommonValue) {
 172       // The potential common value is initialized to the first non-constant.
 173       CommonValue = Incoming;
 174     } else if (Incoming != CommonValue) {
 175       // There can be only one non-constant common value.
 176       return false;
 177     }
 178   }
 179
 180   if (!CommonValue || IncomingConstants.empty())
 181     return false;
 182
 183   // The common value must be valid in all incoming blocks.
 184   BasicBlock *ToBB = P->getParent();
 185   if (auto *CommonInst = dyn_cast<Instruction>(CommonValue))
 186     if (!DT->dominates(CommonInst, ToBB))
 187       return false;
 188
 189   // We have a phi with exactly 1 variable incoming value and 1 or more constant
 190   // incoming values. See if all constant incoming values can be mapped back to
 191   // the same incoming variable value.
 192   for (auto &IncomingConstant : IncomingConstants) {
 193     Constant *C = IncomingConstant.first;
 194     BasicBlock *IncomingBB = P->getIncomingBlock(IncomingConstant.second);
 195     if (C != LVI->getConstantOnEdge(CommonValue, IncomingBB, ToBB, P))
 196       return false;
 197   }
 198
 199   // LVI only guarantees that the value matches a certain constant if the value
 200   // is not poison. Make sure we don't replace a well-defined value with poison.
 201   // This is usually satisfied due to a prior branch on the value.
 202   if (!isGuaranteedNotToBePoison(CommonValue, nullptr, P, DT))
 203     return false;
 204
 205   // All constant incoming values map to the same variable along the incoming
 206   // edges of the phi. The phi is unnecessary.
 207   P->replaceAllUsesWith(CommonValue);
 208   P->eraseFromParent();
 209   ++NumPhiCommon;
 210   return true;
 211 }
 212
 213 static Value *getValueOnEdge(LazyValueInfo *LVI, Value *Incoming,
 214                              BasicBlock *From, BasicBlock *To,
 215                              Instruction *CxtI) {
 216   if (Constant *C = LVI->getConstantOnEdge(Incoming, From, To, CxtI))
 217     return C;
 218
 219   // Look if the incoming value is a select with a scalar condition for which
 220   // LVI can tells us the value. In that case replace the incoming value with
 221   // the appropriate value of the select. This often allows us to remove the
 222   // select later.
 223   auto *SI = dyn_cast<SelectInst>(Incoming);
 224   if (!SI)
 225     return nullptr;
 226
 227   // Once LVI learns to handle vector types, we could also add support
 228   // for vector type constants that are not all zeroes or all ones.
 229   Value *Condition = SI->getCondition();
 230   if (!Condition->getType()->isVectorTy()) {
 231     if (Constant *C = LVI->getConstantOnEdge(Condition, From, To, CxtI)) {
 232       if (C->isOneValue())
 233         return SI->getTrueValue();
 234       if (C->isZeroValue())
 235         return SI->getFalseValue();
 236     }
 237   }
 238
 239   // Look if the select has a constant but LVI tells us that the incoming
 240   // value can never be that constant. In that case replace the incoming
 241   // value with the other value of the select. This often allows us to
 242   // remove the select later.
 243
 244   // The "false" case
 245   if (auto *C = dyn_cast<Constant>(SI->getFalseValue()))
 246     if (LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C, From, To, CxtI) ==
 247         LazyValueInfo::False)
 248       return SI->getTrueValue();
 249
 250   // The "true" case,
 251   // similar to the select "false" case, but try the select "true" value
 252   if (auto *C = dyn_cast<Constant>(SI->getTrueValue()))
 253     if (LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C, From, To, CxtI) ==
 254         LazyValueInfo::False)
 255       return SI->getFalseValue();
 256
 257   return nullptr;
 258 }
 259
 260 static bool processPHI(PHINode *P, LazyValueInfo *LVI, DominatorTree *DT,
 261                        const SimplifyQuery &SQ) {
 262   bool Changed = false;
 263
 264   BasicBlock *BB = P->getParent();
 265   for (unsigned i = 0, e = P->getNumIncomingValues(); i < e; ++i) {
 266     Value *Incoming = P->getIncomingValue(i);
 267     if (isa<Constant>(Incoming)) continue;
 268
 269     Value *V = getValueOnEdge(LVI, Incoming, P->getIncomingBlock(i), BB, P);
 270     if (V) {
 271       P->setIncomingValue(i, V);
 272       Changed = true;
 273     }
 274   }
 275
 276   if (Value *V = simplifyInstruction(P, SQ)) {
 277     P->replaceAllUsesWith(V);
 278     P->eraseFromParent();
 279     Changed = true;
 280   }
 281
 282   if (!Changed)
 283     Changed = simplifyCommonValuePhi(P, LVI, DT);
 284
 285   if (Changed)
 286     ++NumPhis;
 287
 288   return Changed;
 289 }
 290
 291 static bool processICmp(ICmpInst *Cmp, LazyValueInfo *LVI) {
 292   if (!CanonicalizeICmpPredicatesToUnsigned)
 293     return false;
 294
 295   // Only for signed relational comparisons of scalar integers.
 296   if (Cmp->getType()->isVectorTy() ||
 297       !Cmp->getOperand(0)->getType()->isIntegerTy())
 298     return false;
 299
 300   if (!Cmp->isSigned())
 301     return false;
 302
 303   ICmpInst::Predicate UnsignedPred =
 304       ConstantRange::getEquivalentPredWithFlippedSignedness(
 305           Cmp->getPredicate(),
 306           LVI->getConstantRangeAtUse(Cmp->getOperandUse(0),
 307                                      /*UndefAllowed*/ true),
 308           LVI->getConstantRangeAtUse(Cmp->getOperandUse(1),
 309                                      /*UndefAllowed*/ true));
 310
 311   if (UnsignedPred == ICmpInst::Predicate::BAD_ICMP_PREDICATE)
 312     return false;
 313
 314   ++NumSICmps;
 315   Cmp->setPredicate(UnsignedPred);
 316
 317   return true;
 318 }
 319
 320 /// See if LazyValueInfo's ability to exploit edge conditions or range
 321 /// information is sufficient to prove this comparison. Even for local
 322 /// conditions, this can sometimes prove conditions instcombine can't by
 323 /// exploiting range information.
 324 static bool constantFoldCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
 325   Value *Op0 = Cmp->getOperand(0);
 326   Value *Op1 = Cmp->getOperand(1);
 327   LazyValueInfo::Tristate Result =
 328       LVI->getPredicateAt(Cmp->getPredicate(), Op0, Op1, Cmp,
 329                           /*UseBlockValue=*/true);
 330   if (Result == LazyValueInfo::Unknown)
 331     return false;
 332
 333   ++NumCmps;
 334   Constant *TorF =
 335       ConstantInt::get(CmpInst::makeCmpResultType(Op0->getType()), Result);
 336   Cmp->replaceAllUsesWith(TorF);
 337   Cmp->eraseFromParent();
 338   return true;
 339 }
 340
 341 static bool processCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
 342   if (constantFoldCmp(Cmp, LVI))
 343     return true;
 344
 345   if (auto *ICmp = dyn_cast<ICmpInst>(Cmp))
 346     if (processICmp(ICmp, LVI))
 347       return true;
 348
 349   return false;
 350 }
 351
 352 /// Simplify a switch instruction by removing cases which can never fire. If the
 353 /// uselessness of a case could be determined locally then constant propagation
 354 /// would already have figured it out. Instead, walk the predecessors and
 355 /// statically evaluate cases based on information available on that edge. Cases
 356 /// that cannot fire no matter what the incoming edge can safely be removed. If
 357 /// a case fires on every incoming edge then the entire switch can be removed
 358 /// and replaced with a branch to the case destination.
 359 static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
 360                           DominatorTree *DT) {
 361   DomTreeUpdater DTU(*DT, DomTreeUpdater::UpdateStrategy::Lazy);
 362   Value *Cond = I->getCondition();
 363   BasicBlock *BB = I->getParent();
 364
 365   // Analyse each switch case in turn.
 366   bool Changed = false;
 367   DenseMap<BasicBlock*, int> SuccessorsCount;
 368   for (auto *Succ : successors(BB))
 369     SuccessorsCount[Succ]++;
 370
 371   { // Scope for SwitchInstProfUpdateWrapper. It must not live during
 372     // ConstantFoldTerminator() as the underlying SwitchInst can be changed.
 373     SwitchInstProfUpdateWrapper SI(*I);
 374
 375     for (auto CI = SI->case_begin(), CE = SI->case_end(); CI != CE;) {
 376       ConstantInt *Case = CI->getCaseValue();
 377       LazyValueInfo::Tristate State =
 378           LVI->getPredicateAt(CmpInst::ICMP_EQ, Cond, Case, I,
 379                               /* UseBlockValue */ true);
 380
 381       if (State == LazyValueInfo::False) {
 382         // This case never fires - remove it.
 383         BasicBlock *Succ = CI->getCaseSuccessor();
 384         Succ->removePredecessor(BB);
 385         CI = SI.removeCase(CI);
 386         CE = SI->case_end();
 387
 388         // The condition can be modified by removePredecessor's PHI simplification
 389         // logic.
 390         Cond = SI->getCondition();
 391
 392         ++NumDeadCases;
 393         Changed = true;
 394         if (--SuccessorsCount[Succ] == 0)
 395           DTU.applyUpdatesPermissive({{DominatorTree::Delete, BB, Succ}});
 396         continue;
 397       }
 398       if (State == LazyValueInfo::True) {
 399         // This case always fires.  Arrange for the switch to be turned into an
 400         // unconditional branch by replacing the switch condition with the case
 401         // value.
 402         SI->setCondition(Case);
 403         NumDeadCases += SI->getNumCases();
 404         Changed = true;
 405         break;
 406       }
 407
 408       // Increment the case iterator since we didn't delete it.
 409       ++CI;
 410     }
 411   }
 412
 413   if (Changed)
 414     // If the switch has been simplified to the point where it can be replaced
 415     // by a branch then do so now.
 416     ConstantFoldTerminator(BB, /*DeleteDeadConditions = */ false,
 417                            /*TLI = */ nullptr, &DTU);
 418   return Changed;
 419 }
 420
 421 // See if we can prove that the given binary op intrinsic will not overflow.
 422 static bool willNotOverflow(BinaryOpIntrinsic *BO, LazyValueInfo *LVI) {
 423   ConstantRange LRange =
 424       LVI->getConstantRangeAtUse(BO->getOperandUse(0), /*UndefAllowed*/ false);
 425   ConstantRange RRange =
 426       LVI->getConstantRangeAtUse(BO->getOperandUse(1), /*UndefAllowed*/ false);
 427   ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
 428       BO->getBinaryOp(), RRange, BO->getNoWrapKind());
 429   return NWRegion.contains(LRange);
 430 }
 431
 432 static void setDeducedOverflowingFlags(Value *V, Instruction::BinaryOps Opcode,
 433                                        bool NewNSW, bool NewNUW) {
 434   Statistic *OpcNW, *OpcNSW, *OpcNUW;
 435   switch (Opcode) {
 436   case Instruction::Add:
 437     OpcNW = &NumAddNW;
 438     OpcNSW = &NumAddNSW;
 439     OpcNUW = &NumAddNUW;
 440     break;
 441   case Instruction::Sub:
 442     OpcNW = &NumSubNW;
 443     OpcNSW = &NumSubNSW;
 444     OpcNUW = &NumSubNUW;
 445     break;
 446   case Instruction::Mul:
 447     OpcNW = &NumMulNW;
 448     OpcNSW = &NumMulNSW;
 449     OpcNUW = &NumMulNUW;
 450     break;
 451   case Instruction::Shl:
 452     OpcNW = &NumShlNW;
 453     OpcNSW = &NumShlNSW;
 454     OpcNUW = &NumShlNUW;
 455     break;
 456   default:
 457     llvm_unreachable("Will not be called with other binops");
 458   }
 459
 460   auto *Inst = dyn_cast<Instruction>(V);
 461   if (NewNSW) {
 462     ++NumNW;
 463     ++*OpcNW;
 464     ++NumNSW;
 465     ++*OpcNSW;
 466     if (Inst)
 467       Inst->setHasNoSignedWrap();
 468   }
 469   if (NewNUW) {
 470     ++NumNW;
 471     ++*OpcNW;
 472     ++NumNUW;
 473     ++*OpcNUW;
 474     if (Inst)
 475       Inst->setHasNoUnsignedWrap();
 476   }
 477 }
 478
 479 static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI);
 480
 481 // See if @llvm.abs argument is alays positive/negative, and simplify.
 482 // Notably, INT_MIN can belong to either range, regardless of the NSW,
 483 // because it is negation-invariant.
 484 static bool processAbsIntrinsic(IntrinsicInst *II, LazyValueInfo *LVI) {
 485   Value *X = II->getArgOperand(0);
 486   Type *Ty = X->getType();
 487   if (!Ty->isIntegerTy())
 488     return false;
 489
 490   bool IsIntMinPoison = cast<ConstantInt>(II->getArgOperand(1))->isOne();
 491   APInt IntMin = APInt::getSignedMinValue(Ty->getScalarSizeInBits());
 492   ConstantRange Range = LVI->getConstantRangeAtUse(
 493       II->getOperandUse(0), /*UndefAllowed*/ IsIntMinPoison);
 494
 495   // Is X in [0, IntMin]?  NOTE: INT_MIN is fine!
 496   if (Range.icmp(CmpInst::ICMP_ULE, IntMin)) {
 497     ++NumAbs;
 498     II->replaceAllUsesWith(X);
 499     II->eraseFromParent();
 500     return true;
 501   }
 502
 503   // Is X in [IntMin, 0]?  NOTE: INT_MIN is fine!
 504   if (Range.getSignedMax().isNonPositive()) {
 505     IRBuilder<> B(II);
 506     Value *NegX = B.CreateNeg(X, II->getName(), /*HasNUW=*/false,
 507                               /*HasNSW=*/IsIntMinPoison);
 508     ++NumAbs;
 509     II->replaceAllUsesWith(NegX);
 510     II->eraseFromParent();
 511
 512     // See if we can infer some no-wrap flags.
 513     if (auto *BO = dyn_cast<BinaryOperator>(NegX))
 514       processBinOp(BO, LVI);
 515
 516     return true;
 517   }
 518
 519   // Argument's range crosses zero.
 520   // Can we at least tell that the argument is never INT_MIN?
 521   if (!IsIntMinPoison && !Range.contains(IntMin)) {
 522     ++NumNSW;
 523     ++NumSubNSW;
 524     II->setArgOperand(1, ConstantInt::getTrue(II->getContext()));
 525     return true;
 526   }
 527   return false;
 528 }
 529
 530 // See if this min/max intrinsic always picks it's one specific operand.
 531 static bool processMinMaxIntrinsic(MinMaxIntrinsic *MM, LazyValueInfo *LVI) {
 532   CmpInst::Predicate Pred = CmpInst::getNonStrictPredicate(MM->getPredicate());
 533   LazyValueInfo::Tristate Result = LVI->getPredicateAt(
 534       Pred, MM->getLHS(), MM->getRHS(), MM, /*UseBlockValue=*/true);
 535   if (Result == LazyValueInfo::Unknown)
 536     return false;
 537
 538   ++NumMinMax;
 539   MM->replaceAllUsesWith(MM->getOperand(!Result));
 540   MM->eraseFromParent();
 541   return true;
 542 }
 543
 544 // Rewrite this with.overflow intrinsic as non-overflowing.
 545 static bool processOverflowIntrinsic(WithOverflowInst *WO, LazyValueInfo *LVI) {
 546   IRBuilder<> B(WO);
 547   Instruction::BinaryOps Opcode = WO->getBinaryOp();
 548   bool NSW = WO->isSigned();
 549   bool NUW = !WO->isSigned();
 550
 551   Value *NewOp =
 552       B.CreateBinOp(Opcode, WO->getLHS(), WO->getRHS(), WO->getName());
 553   setDeducedOverflowingFlags(NewOp, Opcode, NSW, NUW);
 554
 555   StructType *ST = cast<StructType>(WO->getType());
 556   Constant *Struct = ConstantStruct::get(ST,
 557       { PoisonValue::get(ST->getElementType(0)),
 558         ConstantInt::getFalse(ST->getElementType(1)) });
 559   Value *NewI = B.CreateInsertValue(Struct, NewOp, 0);
 560   WO->replaceAllUsesWith(NewI);
 561   WO->eraseFromParent();
 562   ++NumOverflows;
 563
 564   // See if we can infer the other no-wrap too.
 565   if (auto *BO = dyn_cast<BinaryOperator>(NewOp))
 566     processBinOp(BO, LVI);
 567
 568   return true;
 569 }
 570
 571 static bool processSaturatingInst(SaturatingInst *SI, LazyValueInfo *LVI) {
 572   Instruction::BinaryOps Opcode = SI->getBinaryOp();
 573   bool NSW = SI->isSigned();
 574   bool NUW = !SI->isSigned();
 575   BinaryOperator *BinOp = BinaryOperator::Create(
 576       Opcode, SI->getLHS(), SI->getRHS(), SI->getName(), SI);
 577   BinOp->setDebugLoc(SI->getDebugLoc());
 578   setDeducedOverflowingFlags(BinOp, Opcode, NSW, NUW);
 579
 580   SI->replaceAllUsesWith(BinOp);
 581   SI->eraseFromParent();
 582   ++NumSaturating;
 583
 584   // See if we can infer the other no-wrap too.
 585   if (auto *BO = dyn_cast<BinaryOperator>(BinOp))
 586     processBinOp(BO, LVI);
 587
 588   return true;
 589 }
 590
 591 /// Infer nonnull attributes for the arguments at the specified callsite.
 592 static bool processCallSite(CallBase &CB, LazyValueInfo *LVI) {
 593
 594   if (CB.getIntrinsicID() == Intrinsic::abs) {
 595     return processAbsIntrinsic(&cast<IntrinsicInst>(CB), LVI);
 596   }
 597
 598   if (auto *MM = dyn_cast<MinMaxIntrinsic>(&CB)) {
 599     return processMinMaxIntrinsic(MM, LVI);
 600   }
 601
 602   if (auto *WO = dyn_cast<WithOverflowInst>(&CB)) {
 603     if (WO->getLHS()->getType()->isIntegerTy() && willNotOverflow(WO, LVI)) {
 604       return processOverflowIntrinsic(WO, LVI);
 605     }
 606   }
 607
 608   if (auto *SI = dyn_cast<SaturatingInst>(&CB)) {
 609     if (SI->getType()->isIntegerTy() && willNotOverflow(SI, LVI)) {
 610       return processSaturatingInst(SI, LVI);
 611     }
 612   }
 613
 614   bool Changed = false;
 615
 616   // Deopt bundle operands are intended to capture state with minimal
 617   // perturbance of the code otherwise.  If we can find a constant value for
 618   // any such operand and remove a use of the original value, that's
 619   // desireable since it may allow further optimization of that value (e.g. via
 620   // single use rules in instcombine).  Since deopt uses tend to,
 621   // idiomatically, appear along rare conditional paths, it's reasonable likely
 622   // we may have a conditional fact with which LVI can fold.
 623   if (auto DeoptBundle = CB.getOperandBundle(LLVMContext::OB_deopt)) {
 624     for (const Use &ConstU : DeoptBundle->Inputs) {
 625       Use &U = const_cast<Use&>(ConstU);
 626       Value *V = U.get();
 627       if (V->getType()->isVectorTy()) continue;
 628       if (isa<Constant>(V)) continue;
 629
 630       Constant *C = LVI->getConstant(V, &CB);
 631       if (!C) continue;
 632       U.set(C);
 633       Changed = true;
 634     }
 635   }
 636
 637   SmallVector<unsigned, 4> ArgNos;
 638   unsigned ArgNo = 0;
 639
 640   for (Value *V : CB.args()) {
 641     PointerType *Type = dyn_cast<PointerType>(V->getType());
 642     // Try to mark pointer typed parameters as non-null.  We skip the
 643     // relatively expensive analysis for constants which are obviously either
 644     // null or non-null to start with.
 645     if (Type && !CB.paramHasAttr(ArgNo, Attribute::NonNull) &&
 646         !isa<Constant>(V) &&
 647         LVI->getPredicateAt(ICmpInst::ICMP_EQ, V,
 648                             ConstantPointerNull::get(Type), &CB,
 649                             /*UseBlockValue=*/false) == LazyValueInfo::False)
 650       ArgNos.push_back(ArgNo);
 651     ArgNo++;
 652   }
 653
 654   assert(ArgNo == CB.arg_size() && "Call arguments not processed correctly.");
 655
 656   if (ArgNos.empty())
 657     return Changed;
 658
 659   NumNonNull += ArgNos.size();
 660   AttributeList AS = CB.getAttributes();
 661   LLVMContext &Ctx = CB.getContext();
 662   AS = AS.addParamAttribute(Ctx, ArgNos,
 663                             Attribute::get(Ctx, Attribute::NonNull));
 664   CB.setAttributes(AS);
 665
 666   return true;
 667 }
 668
 669 enum class Domain { NonNegative, NonPositive, Unknown };
 670
 671 static Domain getDomain(const ConstantRange &CR) {
 672   if (CR.isAllNonNegative())
 673     return Domain::NonNegative;
 674   if (CR.icmp(ICmpInst::ICMP_SLE, APInt::getZero(CR.getBitWidth())))
 675     return Domain::NonPositive;
 676   return Domain::Unknown;
 677 }
 678
 679 /// Try to shrink a sdiv/srem's width down to the smallest power of two that's
 680 /// sufficient to contain its operands.
 681 static bool narrowSDivOrSRem(BinaryOperator *Instr, const ConstantRange &LCR,
 682                              const ConstantRange &RCR) {
 683   assert(Instr->getOpcode() == Instruction::SDiv ||
 684          Instr->getOpcode() == Instruction::SRem);
 685   assert(!Instr->getType()->isVectorTy());
 686
 687   // Find the smallest power of two bitwidth that's sufficient to hold Instr's
 688   // operands.
 689   unsigned OrigWidth = Instr->getType()->getIntegerBitWidth();
 690
 691   // What is the smallest bit width that can accommodate the entire value ranges
 692   // of both of the operands?
 693   unsigned MinSignedBits =
 694       std::max(LCR.getMinSignedBits(), RCR.getMinSignedBits());
 695
 696   // sdiv/srem is UB if divisor is -1 and divident is INT_MIN, so unless we can
 697   // prove that such a combination is impossible, we need to bump the bitwidth.
 698   if (RCR.contains(APInt::getAllOnes(OrigWidth)) &&
 699       LCR.contains(APInt::getSignedMinValue(MinSignedBits).sext(OrigWidth)))
 700     ++MinSignedBits;
 701
 702   // Don't shrink below 8 bits wide.
 703   unsigned NewWidth = std::max<unsigned>(PowerOf2Ceil(MinSignedBits), 8);
 704
 705   // NewWidth might be greater than OrigWidth if OrigWidth is not a power of
 706   // two.
 707   if (NewWidth >= OrigWidth)
 708     return false;
 709
 710   ++NumSDivSRemsNarrowed;
 711   IRBuilder<> B{Instr};
 712   auto *TruncTy = Type::getIntNTy(Instr->getContext(), NewWidth);
 713   auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
 714                                      Instr->getName() + ".lhs.trunc");
 715   auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
 716                                      Instr->getName() + ".rhs.trunc");
 717   auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
 718   auto *Sext = B.CreateSExt(BO, Instr->getType(), Instr->getName() + ".sext");
 719   if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
 720     if (BinOp->getOpcode() == Instruction::SDiv)
 721       BinOp->setIsExact(Instr->isExact());
 722
 723   Instr->replaceAllUsesWith(Sext);
 724   Instr->eraseFromParent();
 725   return true;
 726 }
 727
 728 static bool expandUDivOrURem(BinaryOperator *Instr, const ConstantRange &XCR,
 729                              const ConstantRange &YCR) {
 730   Type *Ty = Instr->getType();
 731   assert(Instr->getOpcode() == Instruction::UDiv ||
 732          Instr->getOpcode() == Instruction::URem);
 733   assert(!Ty->isVectorTy());
 734   bool IsRem = Instr->getOpcode() == Instruction::URem;
 735
 736   Value *X = Instr->getOperand(0);
 737   Value *Y = Instr->getOperand(1);
 738
 739   // X u/ Y -> 0  iff X u< Y
 740   // X u% Y -> X  iff X u< Y
 741   if (XCR.icmp(ICmpInst::ICMP_ULT, YCR)) {
 742     Instr->replaceAllUsesWith(IsRem ? X : Constant::getNullValue(Ty));
 743     Instr->eraseFromParent();
 744     ++NumUDivURemsNarrowedExpanded;
 745     return true;
 746   }
 747
 748   // Given
 749   //   R  = X u% Y
 750   // We can represent the modulo operation as a loop/self-recursion:
 751   //   urem_rec(X, Y):
 752   //     Z = X - Y
 753   //     if X u< Y
 754   //       ret X
 755   //     else
 756   //       ret urem_rec(Z, Y)
 757   // which isn't better, but if we only need a single iteration
 758   // to compute the answer, this becomes quite good:
 759   //   R  = X < Y ? X : X - Y    iff X u< 2*Y (w/ unsigned saturation)
 760   // Now, we do not care about all full multiples of Y in X, they do not change
 761   // the answer, thus we could rewrite the expression as:
 762   //   X* = X - (Y * |_ X / Y _|)
 763   //   R  = X* % Y
 764   // so we don't need the *first* iteration to return, we just need to
 765   // know *which* iteration will always return, so we could also rewrite it as:
 766   //   X* = X - (Y * |_ X / Y _|)
 767   //   R  = X* % Y                 iff X* u< 2*Y (w/ unsigned saturation)
 768   // but that does not seem profitable here.
 769
 770   // Even if we don't know X's range, the divisor may be so large, X can't ever
 771   // be 2x larger than that. I.e. if divisor is always negative.
 772   if (!XCR.icmp(ICmpInst::ICMP_ULT,
 773                 YCR.umul_sat(APInt(YCR.getBitWidth(), 2))) &&
 774       !YCR.isAllNegative())
 775     return false;
 776
 777   IRBuilder<> B(Instr);
 778   Value *ExpandedOp;
 779   if (XCR.icmp(ICmpInst::ICMP_UGE, YCR)) {
 780     // If X is between Y and 2*Y the result is known.
 781     if (IsRem)
 782       ExpandedOp = B.CreateNUWSub(X, Y);
 783     else
 784       ExpandedOp = ConstantInt::get(Instr->getType(), 1);
 785   } else if (IsRem) {
 786     // NOTE: this transformation introduces two uses of X,
 787     //       but it may be undef so we must freeze it first.
 788     Value *FrozenX = X;
 789     if (!isGuaranteedNotToBeUndef(X))
 790       FrozenX = B.CreateFreeze(X, X->getName() + ".frozen");
 791     auto *AdjX = B.CreateNUWSub(FrozenX, Y, Instr->getName() + ".urem");
 792     auto *Cmp =
 793         B.CreateICmp(ICmpInst::ICMP_ULT, FrozenX, Y, Instr->getName() + ".cmp");
 794     ExpandedOp = B.CreateSelect(Cmp, FrozenX, AdjX);
 795   } else {
 796     auto *Cmp =
 797         B.CreateICmp(ICmpInst::ICMP_UGE, X, Y, Instr->getName() + ".cmp");
 798     ExpandedOp = B.CreateZExt(Cmp, Ty, Instr->getName() + ".udiv");
 799   }
 800   ExpandedOp->takeName(Instr);
 801   Instr->replaceAllUsesWith(ExpandedOp);
 802   Instr->eraseFromParent();
 803   ++NumUDivURemsNarrowedExpanded;
 804   return true;
 805 }
 806
 807 /// Try to shrink a udiv/urem's width down to the smallest power of two that's
 808 /// sufficient to contain its operands.
 809 static bool narrowUDivOrURem(BinaryOperator *Instr, const ConstantRange &XCR,
 810                              const ConstantRange &YCR) {
 811   assert(Instr->getOpcode() == Instruction::UDiv ||
 812          Instr->getOpcode() == Instruction::URem);
 813   assert(!Instr->getType()->isVectorTy());
 814
 815   // Find the smallest power of two bitwidth that's sufficient to hold Instr's
 816   // operands.
 817
 818   // What is the smallest bit width that can accommodate the entire value ranges
 819   // of both of the operands?
 820   unsigned MaxActiveBits = std::max(XCR.getActiveBits(), YCR.getActiveBits());
 821   // Don't shrink below 8 bits wide.
 822   unsigned NewWidth = std::max<unsigned>(PowerOf2Ceil(MaxActiveBits), 8);
 823
 824   // NewWidth might be greater than OrigWidth if OrigWidth is not a power of
 825   // two.
 826   if (NewWidth >= Instr->getType()->getIntegerBitWidth())
 827     return false;
 828
 829   ++NumUDivURemsNarrowed;
 830   IRBuilder<> B{Instr};
 831   auto *TruncTy = Type::getIntNTy(Instr->getContext(), NewWidth);
 832   auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
 833                                      Instr->getName() + ".lhs.trunc");
 834   auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
 835                                      Instr->getName() + ".rhs.trunc");
 836   auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
 837   auto *Zext = B.CreateZExt(BO, Instr->getType(), Instr->getName() + ".zext");
 838   if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
 839     if (BinOp->getOpcode() == Instruction::UDiv)
 840       BinOp->setIsExact(Instr->isExact());
 841
 842   Instr->replaceAllUsesWith(Zext);
 843   Instr->eraseFromParent();
 844   return true;
 845 }
 846
 847 static bool processUDivOrURem(BinaryOperator *Instr, LazyValueInfo *LVI) {
 848   assert(Instr->getOpcode() == Instruction::UDiv ||
 849          Instr->getOpcode() == Instruction::URem);
 850   if (Instr->getType()->isVectorTy())
 851     return false;
 852
 853   ConstantRange XCR = LVI->getConstantRangeAtUse(Instr->getOperandUse(0),
 854                                                  /*UndefAllowed*/ false);
 855   // Allow undef for RHS, as we can assume it is division by zero UB.
 856   ConstantRange YCR = LVI->getConstantRangeAtUse(Instr->getOperandUse(1),
 857                                                  /*UndefAllowed*/ true);
 858   if (expandUDivOrURem(Instr, XCR, YCR))
 859     return true;
 860
 861   return narrowUDivOrURem(Instr, XCR, YCR);
 862 }
 863
 864 static bool processSRem(BinaryOperator *SDI, const ConstantRange &LCR,
 865                         const ConstantRange &RCR, LazyValueInfo *LVI) {
 866   assert(SDI->getOpcode() == Instruction::SRem);
 867   assert(!SDI->getType()->isVectorTy());
 868
 869   if (LCR.abs().icmp(CmpInst::ICMP_ULT, RCR.abs())) {
 870     SDI->replaceAllUsesWith(SDI->getOperand(0));
 871     SDI->eraseFromParent();
 872     return true;
 873   }
 874
 875   struct Operand {
 876     Value *V;
 877     Domain D;
 878   };
 879   std::array<Operand, 2> Ops = {{{SDI->getOperand(0), getDomain(LCR)},
 880                                  {SDI->getOperand(1), getDomain(RCR)}}};
 881   if (Ops[0].D == Domain::Unknown || Ops[1].D == Domain::Unknown)
 882     return false;
 883
 884   // We know domains of both of the operands!
 885   ++NumSRems;
 886
 887   // We need operands to be non-negative, so negate each one that isn't.
 888   for (Operand &Op : Ops) {
 889     if (Op.D == Domain::NonNegative)
 890       continue;
 891     auto *BO =
 892         BinaryOperator::CreateNeg(Op.V, Op.V->getName() + ".nonneg", SDI);
 893     BO->setDebugLoc(SDI->getDebugLoc());
 894     Op.V = BO;
 895   }
 896
 897   auto *URem =
 898       BinaryOperator::CreateURem(Ops[0].V, Ops[1].V, SDI->getName(), SDI);
 899   URem->setDebugLoc(SDI->getDebugLoc());
 900
 901   auto *Res = URem;
 902
 903   // If the divident was non-positive, we need to negate the result.
 904   if (Ops[0].D == Domain::NonPositive) {
 905     Res = BinaryOperator::CreateNeg(Res, Res->getName() + ".neg", SDI);
 906     Res->setDebugLoc(SDI->getDebugLoc());
 907   }
 908
 909   SDI->replaceAllUsesWith(Res);
 910   SDI->eraseFromParent();
 911
 912   // Try to simplify our new urem.
 913   processUDivOrURem(URem, LVI);
 914
 915   return true;
 916 }
 917
 918 /// See if LazyValueInfo's ability to exploit edge conditions or range
 919 /// information is sufficient to prove the signs of both operands of this SDiv.
 920 /// If this is the case, replace the SDiv with a UDiv. Even for local
 921 /// conditions, this can sometimes prove conditions instcombine can't by
 922 /// exploiting range information.
 923 static bool processSDiv(BinaryOperator *SDI, const ConstantRange &LCR,
 924                         const ConstantRange &RCR, LazyValueInfo *LVI) {
 925   assert(SDI->getOpcode() == Instruction::SDiv);
 926   assert(!SDI->getType()->isVectorTy());
 927
 928   // Check whether the division folds to a constant.
 929   ConstantRange DivCR = LCR.sdiv(RCR);
 930   if (const APInt *Elem = DivCR.getSingleElement()) {
 931     SDI->replaceAllUsesWith(ConstantInt::get(SDI->getType(), *Elem));
 932     SDI->eraseFromParent();
 933     return true;
 934   }
 935
 936   struct Operand {
 937     Value *V;
 938     Domain D;
 939   };
 940   std::array<Operand, 2> Ops = {{{SDI->getOperand(0), getDomain(LCR)},
 941                                  {SDI->getOperand(1), getDomain(RCR)}}};
 942   if (Ops[0].D == Domain::Unknown || Ops[1].D == Domain::Unknown)
 943     return false;
 944
 945   // We know domains of both of the operands!
 946   ++NumSDivs;
 947
 948   // We need operands to be non-negative, so negate each one that isn't.
 949   for (Operand &Op : Ops) {
 950     if (Op.D == Domain::NonNegative)
 951       continue;
 952     auto *BO =
 953         BinaryOperator::CreateNeg(Op.V, Op.V->getName() + ".nonneg", SDI);
 954     BO->setDebugLoc(SDI->getDebugLoc());
 955     Op.V = BO;
 956   }
 957
 958   auto *UDiv =
 959       BinaryOperator::CreateUDiv(Ops[0].V, Ops[1].V, SDI->getName(), SDI);
 960   UDiv->setDebugLoc(SDI->getDebugLoc());
 961   UDiv->setIsExact(SDI->isExact());
 962
 963   auto *Res = UDiv;
 964
 965   // If the operands had two different domains, we need to negate the result.
 966   if (Ops[0].D != Ops[1].D) {
 967     Res = BinaryOperator::CreateNeg(Res, Res->getName() + ".neg", SDI);
 968     Res->setDebugLoc(SDI->getDebugLoc());
 969   }
 970
 971   SDI->replaceAllUsesWith(Res);
 972   SDI->eraseFromParent();
 973
 974   // Try to simplify our new udiv.
 975   processUDivOrURem(UDiv, LVI);
 976
 977   return true;
 978 }
 979
 980 static bool processSDivOrSRem(BinaryOperator *Instr, LazyValueInfo *LVI) {
 981   assert(Instr->getOpcode() == Instruction::SDiv ||
 982          Instr->getOpcode() == Instruction::SRem);
 983   if (Instr->getType()->isVectorTy())
 984     return false;
 985
 986   ConstantRange LCR =
 987       LVI->getConstantRangeAtUse(Instr->getOperandUse(0), /*AllowUndef*/ false);
 988   // Allow undef for RHS, as we can assume it is division by zero UB.
 989   ConstantRange RCR =
 990       LVI->getConstantRangeAtUse(Instr->getOperandUse(1), /*AlloweUndef*/ true);
 991   if (Instr->getOpcode() == Instruction::SDiv)
 992     if (processSDiv(Instr, LCR, RCR, LVI))
 993       return true;
 994
 995   if (Instr->getOpcode() == Instruction::SRem) {
 996     if (processSRem(Instr, LCR, RCR, LVI))
 997       return true;
 998   }
 999
1000   return narrowSDivOrSRem(Instr, LCR, RCR);
1001 }
1002
1003 static bool processAShr(BinaryOperator *SDI, LazyValueInfo *LVI) {
1004   if (SDI->getType()->isVectorTy())
1005     return false;
1006
1007   ConstantRange LRange =
1008       LVI->getConstantRangeAtUse(SDI->getOperandUse(0), /*UndefAllowed*/ false);
1009   unsigned OrigWidth = SDI->getType()->getIntegerBitWidth();
1010   ConstantRange NegOneOrZero =
1011       ConstantRange(APInt(OrigWidth, (uint64_t)-1, true), APInt(OrigWidth, 1));
1012   if (NegOneOrZero.contains(LRange)) {
1013     // ashr of -1 or 0 never changes the value, so drop the whole instruction
1014     ++NumAShrsRemoved;
1015     SDI->replaceAllUsesWith(SDI->getOperand(0));
1016     SDI->eraseFromParent();
1017     return true;
1018   }
1019
1020   if (!LRange.isAllNonNegative())
1021     return false;
1022
1023   ++NumAShrsConverted;
1024   auto *BO = BinaryOperator::CreateLShr(SDI->getOperand(0), SDI->getOperand(1),
1025                                         "", SDI);
1026   BO->takeName(SDI);
1027   BO->setDebugLoc(SDI->getDebugLoc());
1028   BO->setIsExact(SDI->isExact());
1029   SDI->replaceAllUsesWith(BO);
1030   SDI->eraseFromParent();
1031
1032   return true;
1033 }
1034
1035 static bool processSExt(SExtInst *SDI, LazyValueInfo *LVI) {
1036   if (SDI->getType()->isVectorTy())
1037     return false;
1038
1039   const Use &Base = SDI->getOperandUse(0);
1040   if (!LVI->getConstantRangeAtUse(Base, /*UndefAllowed*/ false)
1041            .isAllNonNegative())
1042     return false;
1043
1044   ++NumSExt;
1045   auto *ZExt = CastInst::CreateZExtOrBitCast(Base, SDI->getType(), "", SDI);
1046   ZExt->takeName(SDI);
1047   ZExt->setDebugLoc(SDI->getDebugLoc());
1048   ZExt->setNonNeg();
1049   SDI->replaceAllUsesWith(ZExt);
1050   SDI->eraseFromParent();
1051
1052   return true;
1053 }
1054
1055 static bool processZExt(ZExtInst *ZExt, LazyValueInfo *LVI) {
1056   if (ZExt->getType()->isVectorTy())
1057     return false;
1058
1059   if (ZExt->hasNonNeg())
1060     return false;
1061
1062   const Use &Base = ZExt->getOperandUse(0);
1063   if (!LVI->getConstantRangeAtUse(Base, /*UndefAllowed*/ false)
1064            .isAllNonNegative())
1065     return false;
1066
1067   ++NumZExt;
1068   ZExt->setNonNeg();
1069
1070   return true;
1071 }
1072
1073 static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI) {
1074   using OBO = OverflowingBinaryOperator;
1075
1076   if (BinOp->getType()->isVectorTy())
1077     return false;
1078
1079   bool NSW = BinOp->hasNoSignedWrap();
1080   bool NUW = BinOp->hasNoUnsignedWrap();
1081   if (NSW && NUW)
1082     return false;
1083
1084   Instruction::BinaryOps Opcode = BinOp->getOpcode();
1085   Value *LHS = BinOp->getOperand(0);
1086   Value *RHS = BinOp->getOperand(1);
1087
1088   ConstantRange LRange =
1089       LVI->getConstantRange(LHS, BinOp, /*UndefAllowed*/ false);
1090   ConstantRange RRange =
1091       LVI->getConstantRange(RHS, BinOp, /*UndefAllowed*/ false);
1092
1093   bool Changed = false;
1094   bool NewNUW = false, NewNSW = false;
1095   if (!NUW) {
1096     ConstantRange NUWRange = ConstantRange::makeGuaranteedNoWrapRegion(
1097         Opcode, RRange, OBO::NoUnsignedWrap);
1098     NewNUW = NUWRange.contains(LRange);
1099     Changed |= NewNUW;
1100   }
1101   if (!NSW) {
1102     ConstantRange NSWRange = ConstantRange::makeGuaranteedNoWrapRegion(
1103         Opcode, RRange, OBO::NoSignedWrap);
1104     NewNSW = NSWRange.contains(LRange);
1105     Changed |= NewNSW;
1106   }
1107
1108   setDeducedOverflowingFlags(BinOp, Opcode, NewNSW, NewNUW);
1109
1110   return Changed;
1111 }
1112
1113 static bool processAnd(BinaryOperator *BinOp, LazyValueInfo *LVI) {
1114   if (BinOp->getType()->isVectorTy())
1115     return false;
1116
1117   // Pattern match (and lhs, C) where C includes a superset of bits which might
1118   // be set in lhs.  This is a common truncation idiom created by instcombine.
1119   const Use &LHS = BinOp->getOperandUse(0);
1120   ConstantInt *RHS = dyn_cast<ConstantInt>(BinOp->getOperand(1));
1121   if (!RHS || !RHS->getValue().isMask())
1122     return false;
1123
1124   // We can only replace the AND with LHS based on range info if the range does
1125   // not include undef.
1126   ConstantRange LRange =
1127       LVI->getConstantRangeAtUse(LHS, /*UndefAllowed=*/false);
1128   if (!LRange.getUnsignedMax().ule(RHS->getValue()))
1129     return false;
1130
1131   BinOp->replaceAllUsesWith(LHS);
1132   BinOp->eraseFromParent();
1133   NumAnd++;
1134   return true;
1135 }
1136
1137 static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
1138                     const SimplifyQuery &SQ) {
1139   bool FnChanged = false;
1140   // Visiting in a pre-order depth-first traversal causes us to simplify early
1141   // blocks before querying later blocks (which require us to analyze early
1142   // blocks).  Eagerly simplifying shallow blocks means there is strictly less
1143   // work to do for deep blocks.  This also means we don't visit unreachable
1144   // blocks.
1145   for (BasicBlock *BB : depth_first(&F.getEntryBlock())) {
1146     bool BBChanged = false;
1147     for (Instruction &II : llvm::make_early_inc_range(*BB)) {
1148       switch (II.getOpcode()) {
1149       case Instruction::Select:
1150         BBChanged |= processSelect(cast<SelectInst>(&II), LVI);
1151         break;
1152       case Instruction::PHI:
1153         BBChanged |= processPHI(cast<PHINode>(&II), LVI, DT, SQ);
1154         break;
1155       case Instruction::ICmp:
1156       case Instruction::FCmp:
1157         BBChanged |= processCmp(cast<CmpInst>(&II), LVI);
1158         break;
1159       case Instruction::Call:
1160       case Instruction::Invoke:
1161         BBChanged |= processCallSite(cast<CallBase>(II), LVI);
1162         break;
1163       case Instruction::SRem:
1164       case Instruction::SDiv:
1165         BBChanged |= processSDivOrSRem(cast<BinaryOperator>(&II), LVI);
1166         break;
1167       case Instruction::UDiv:
1168       case Instruction::URem:
1169         BBChanged |= processUDivOrURem(cast<BinaryOperator>(&II), LVI);
1170         break;
1171       case Instruction::AShr:
1172         BBChanged |= processAShr(cast<BinaryOperator>(&II), LVI);
1173         break;
1174       case Instruction::SExt:
1175         BBChanged |= processSExt(cast<SExtInst>(&II), LVI);
1176         break;
1177       case Instruction::ZExt:
1178         BBChanged |= processZExt(cast<ZExtInst>(&II), LVI);
1179         break;
1180       case Instruction::Add:
1181       case Instruction::Sub:
1182       case Instruction::Mul:
1183       case Instruction::Shl:
1184         BBChanged |= processBinOp(cast<BinaryOperator>(&II), LVI);
1185         break;
1186       case Instruction::And:
1187         BBChanged |= processAnd(cast<BinaryOperator>(&II), LVI);
1188         break;
1189       }
1190     }
1191
1192     Instruction *Term = BB->getTerminator();
1193     switch (Term->getOpcode()) {
1194     case Instruction::Switch:
1195       BBChanged |= processSwitch(cast<SwitchInst>(Term), LVI, DT);
1196       break;
1197     case Instruction::Ret: {
1198       auto *RI = cast<ReturnInst>(Term);
1199       // Try to determine the return value if we can.  This is mainly here to
1200       // simplify the writing of unit tests, but also helps to enable IPO by
1201       // constant folding the return values of callees.
1202       auto *RetVal = RI->getReturnValue();
1203       if (!RetVal) break; // handle "ret void"
1204       if (isa<Constant>(RetVal)) break; // nothing to do
1205       if (auto *C = getConstantAt(RetVal, RI, LVI)) {
1206         ++NumReturns;
1207         RI->replaceUsesOfWith(RetVal, C);
1208         BBChanged = true;
1209       }
1210     }
1211     }
1212
1213     FnChanged |= BBChanged;
1214   }
1215
1216   return FnChanged;
1217 }
1218
1219 PreservedAnalyses
1220 CorrelatedValuePropagationPass::run(Function &F, FunctionAnalysisManager &AM) {
1221   LazyValueInfo *LVI = &AM.getResult<LazyValueAnalysis>(F);
1222   DominatorTree *DT = &AM.getResult<DominatorTreeAnalysis>(F);
1223
1224   bool Changed = runImpl(F, LVI, DT, getBestSimplifyQuery(AM, F));
1225
1226   PreservedAnalyses PA;
1227   if (!Changed) {
1228     PA = PreservedAnalyses::all();
1229   } else {
1230     PA.preserve<DominatorTreeAnalysis>();
1231     PA.preserve<LazyValueAnalysis>();
1232   }
1233
1234   // Keeping LVI alive is expensive, both because it uses a lot of memory, and
1235   // because invalidating values in LVI is expensive. While CVP does preserve
1236   // LVI, we know that passes after JumpThreading+CVP will not need the result
1237   // of this analysis, so we forcefully discard it early.
1238   PA.abandon<LazyValueAnalysis>();
1239   return PA;
1240 }