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/Optional.h"
  16 #include "llvm/ADT/SmallVector.h"
  17 #include "llvm/ADT/Statistic.h"
  18 #include "llvm/Analysis/DomTreeUpdater.h"
  19 #include "llvm/Analysis/GlobalsModRef.h"
  20 #include "llvm/Analysis/InstructionSimplify.h"
  21 #include "llvm/Analysis/LazyValueInfo.h"
  22 #include "llvm/Analysis/ValueTracking.h"
  23 #include "llvm/IR/Attributes.h"
  24 #include "llvm/IR/BasicBlock.h"
  25 #include "llvm/IR/CFG.h"
  26 #include "llvm/IR/Constant.h"
  27 #include "llvm/IR/ConstantRange.h"
  28 #include "llvm/IR/Constants.h"
  29 #include "llvm/IR/DerivedTypes.h"
  30 #include "llvm/IR/Function.h"
  31 #include "llvm/IR/IRBuilder.h"
  32 #include "llvm/IR/InstrTypes.h"
  33 #include "llvm/IR/Instruction.h"
  34 #include "llvm/IR/Instructions.h"
  35 #include "llvm/IR/IntrinsicInst.h"
  36 #include "llvm/IR/Operator.h"
  37 #include "llvm/IR/PassManager.h"
  38 #include "llvm/IR/Type.h"
  39 #include "llvm/IR/Value.h"
  40 #include "llvm/InitializePasses.h"
  41 #include "llvm/Pass.h"
  42 #include "llvm/Support/Casting.h"
  43 #include "llvm/Support/CommandLine.h"
  44 #include "llvm/Support/Debug.h"
  45 #include "llvm/Support/raw_ostream.h"
  46 #include "llvm/Transforms/Scalar.h"
  47 #include "llvm/Transforms/Utils/Local.h"
  48 #include <cassert>
  49 #include <utility>
  50
  51 using namespace llvm;
  52
  53 #define DEBUG_TYPE "correlated-value-propagation"
  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(NumMemAccess, "Number of memory access targets propagated");
  59 STATISTIC(NumCmps,      "Number of comparisons propagated");
  60 STATISTIC(NumReturns,   "Number of return values propagated");
  61 STATISTIC(NumDeadCases, "Number of switch cases removed");
  62 STATISTIC(NumSDivSRemsNarrowed,
  63           "Number of sdivs/srems whose width was decreased");
  64 STATISTIC(NumSDivs,     "Number of sdiv converted to udiv");
  65 STATISTIC(NumUDivURemsNarrowed,
  66           "Number of udivs/urems whose width was decreased");
  67 STATISTIC(NumAShrs,     "Number of ashr converted to lshr");
  68 STATISTIC(NumSRems,     "Number of srem converted to urem");
  69 STATISTIC(NumSExt,      "Number of sext converted to zext");
  70 STATISTIC(NumAnd,       "Number of ands removed");
  71 STATISTIC(NumNW,        "Number of no-wrap deductions");
  72 STATISTIC(NumNSW,       "Number of no-signed-wrap deductions");
  73 STATISTIC(NumNUW,       "Number of no-unsigned-wrap deductions");
  74 STATISTIC(NumAddNW,     "Number of no-wrap deductions for add");
  75 STATISTIC(NumAddNSW,    "Number of no-signed-wrap deductions for add");
  76 STATISTIC(NumAddNUW,    "Number of no-unsigned-wrap deductions for add");
  77 STATISTIC(NumSubNW,     "Number of no-wrap deductions for sub");
  78 STATISTIC(NumSubNSW,    "Number of no-signed-wrap deductions for sub");
  79 STATISTIC(NumSubNUW,    "Number of no-unsigned-wrap deductions for sub");
  80 STATISTIC(NumMulNW,     "Number of no-wrap deductions for mul");
  81 STATISTIC(NumMulNSW,    "Number of no-signed-wrap deductions for mul");
  82 STATISTIC(NumMulNUW,    "Number of no-unsigned-wrap deductions for mul");
  83 STATISTIC(NumShlNW,     "Number of no-wrap deductions for shl");
  84 STATISTIC(NumShlNSW,    "Number of no-signed-wrap deductions for shl");
  85 STATISTIC(NumShlNUW,    "Number of no-unsigned-wrap deductions for shl");
  86 STATISTIC(NumAbs,       "Number of llvm.abs intrinsics removed");
  87 STATISTIC(NumOverflows, "Number of overflow checks removed");
  88 STATISTIC(NumSaturating,
  89     "Number of saturating arithmetics converted to normal arithmetics");
  90 STATISTIC(NumNonNull, "Number of function pointer arguments marked non-null");
  91 STATISTIC(NumMinMax, "Number of llvm.[us]{min,max} intrinsics removed");
  92
  93 namespace {
  94
  95   class CorrelatedValuePropagation : public FunctionPass {
  96   public:
  97     static char ID;
  98
  99     CorrelatedValuePropagation(): FunctionPass(ID) {
 100      initializeCorrelatedValuePropagationPass(*PassRegistry::getPassRegistry());
 101     }
 102
 103     bool runOnFunction(Function &F) override;
 104
 105     void getAnalysisUsage(AnalysisUsage &AU) const override {
 106       AU.addRequired<DominatorTreeWrapperPass>();
 107       AU.addRequired<LazyValueInfoWrapperPass>();
 108       AU.addPreserved<GlobalsAAWrapperPass>();
 109       AU.addPreserved<DominatorTreeWrapperPass>();
 110       AU.addPreserved<LazyValueInfoWrapperPass>();
 111     }
 112   };
 113
 114 } // end anonymous namespace
 115
 116 char CorrelatedValuePropagation::ID = 0;
 117
 118 INITIALIZE_PASS_BEGIN(CorrelatedValuePropagation, "correlated-propagation",
 119                 "Value Propagation", false, false)
 120 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 121 INITIALIZE_PASS_DEPENDENCY(LazyValueInfoWrapperPass)
 122 INITIALIZE_PASS_END(CorrelatedValuePropagation, "correlated-propagation",
 123                 "Value Propagation", false, false)
 124
 125 // Public interface to the Value Propagation pass
 126 Pass *llvm::createCorrelatedValuePropagationPass() {
 127   return new CorrelatedValuePropagation();
 128 }
 129
 130 static bool processSelect(SelectInst *S, LazyValueInfo *LVI) {
 131   if (S->getType()->isVectorTy()) return false;
 132   if (isa<Constant>(S->getCondition())) return false;
 133
 134   Constant *C = LVI->getConstant(S->getCondition(), S);
 135   if (!C) return false;
 136
 137   ConstantInt *CI = dyn_cast<ConstantInt>(C);
 138   if (!CI) return false;
 139
 140   Value *ReplaceWith = CI->isOne() ? S->getTrueValue() : S->getFalseValue();
 141   S->replaceAllUsesWith(ReplaceWith);
 142   S->eraseFromParent();
 143
 144   ++NumSelects;
 145
 146   return true;
 147 }
 148
 149 /// Try to simplify a phi with constant incoming values that match the edge
 150 /// values of a non-constant value on all other edges:
 151 /// bb0:
 152 ///   %isnull = icmp eq i8* %x, null
 153 ///   br i1 %isnull, label %bb2, label %bb1
 154 /// bb1:
 155 ///   br label %bb2
 156 /// bb2:
 157 ///   %r = phi i8* [ %x, %bb1 ], [ null, %bb0 ]
 158 /// -->
 159 ///   %r = %x
 160 static bool simplifyCommonValuePhi(PHINode *P, LazyValueInfo *LVI,
 161                                    DominatorTree *DT) {
 162   // Collect incoming constants and initialize possible common value.
 163   SmallVector<std::pair<Constant *, unsigned>, 4> IncomingConstants;
 164   Value *CommonValue = nullptr;
 165   for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) {
 166     Value *Incoming = P->getIncomingValue(i);
 167     if (auto *IncomingConstant = dyn_cast<Constant>(Incoming)) {
 168       IncomingConstants.push_back(std::make_pair(IncomingConstant, i));
 169     } else if (!CommonValue) {
 170       // The potential common value is initialized to the first non-constant.
 171       CommonValue = Incoming;
 172     } else if (Incoming != CommonValue) {
 173       // There can be only one non-constant common value.
 174       return false;
 175     }
 176   }
 177
 178   if (!CommonValue || IncomingConstants.empty())
 179     return false;
 180
 181   // The common value must be valid in all incoming blocks.
 182   BasicBlock *ToBB = P->getParent();
 183   if (auto *CommonInst = dyn_cast<Instruction>(CommonValue))
 184     if (!DT->dominates(CommonInst, ToBB))
 185       return false;
 186
 187   // We have a phi with exactly 1 variable incoming value and 1 or more constant
 188   // incoming values. See if all constant incoming values can be mapped back to
 189   // the same incoming variable value.
 190   for (auto &IncomingConstant : IncomingConstants) {
 191     Constant *C = IncomingConstant.first;
 192     BasicBlock *IncomingBB = P->getIncomingBlock(IncomingConstant.second);
 193     if (C != LVI->getConstantOnEdge(CommonValue, IncomingBB, ToBB, P))
 194       return false;
 195   }
 196
 197   // LVI only guarantees that the value matches a certain constant if the value
 198   // is not poison. Make sure we don't replace a well-defined value with poison.
 199   // This is usually satisfied due to a prior branch on the value.
 200   if (!isGuaranteedNotToBePoison(CommonValue, nullptr, P, DT))
 201     return false;
 202
 203   // All constant incoming values map to the same variable along the incoming
 204   // edges of the phi. The phi is unnecessary.
 205   P->replaceAllUsesWith(CommonValue);
 206   P->eraseFromParent();
 207   ++NumPhiCommon;
 208   return true;
 209 }
 210
 211 static bool processPHI(PHINode *P, LazyValueInfo *LVI, DominatorTree *DT,
 212                        const SimplifyQuery &SQ) {
 213   bool Changed = false;
 214
 215   BasicBlock *BB = P->getParent();
 216   for (unsigned i = 0, e = P->getNumIncomingValues(); i < e; ++i) {
 217     Value *Incoming = P->getIncomingValue(i);
 218     if (isa<Constant>(Incoming)) continue;
 219
 220     Value *V = LVI->getConstantOnEdge(Incoming, P->getIncomingBlock(i), BB, P);
 221
 222     // Look if the incoming value is a select with a scalar condition for which
 223     // LVI can tells us the value. In that case replace the incoming value with
 224     // the appropriate value of the select. This often allows us to remove the
 225     // select later.
 226     if (!V) {
 227       SelectInst *SI = dyn_cast<SelectInst>(Incoming);
 228       if (!SI) continue;
 229
 230       Value *Condition = SI->getCondition();
 231       if (!Condition->getType()->isVectorTy()) {
 232         if (Constant *C = LVI->getConstantOnEdge(
 233                 Condition, P->getIncomingBlock(i), BB, P)) {
 234           if (C->isOneValue()) {
 235             V = SI->getTrueValue();
 236           } else if (C->isZeroValue()) {
 237             V = SI->getFalseValue();
 238           }
 239           // Once LVI learns to handle vector types, we could also add support
 240           // for vector type constants that are not all zeroes or all ones.
 241         }
 242       }
 243
 244       // Look if the select has a constant but LVI tells us that the incoming
 245       // value can never be that constant. In that case replace the incoming
 246       // value with the other value of the select. This often allows us to
 247       // remove the select later.
 248       if (!V) {
 249         Constant *C = dyn_cast<Constant>(SI->getFalseValue());
 250         if (!C) continue;
 251
 252         if (LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C,
 253               P->getIncomingBlock(i), BB, P) !=
 254             LazyValueInfo::False)
 255           continue;
 256         V = SI->getTrueValue();
 257       }
 258
 259       LLVM_DEBUG(dbgs() << "CVP: Threading PHI over " << *SI << '\n');
 260     }
 261
 262     P->setIncomingValue(i, V);
 263     Changed = true;
 264   }
 265
 266   if (Value *V = SimplifyInstruction(P, SQ)) {
 267     P->replaceAllUsesWith(V);
 268     P->eraseFromParent();
 269     Changed = true;
 270   }
 271
 272   if (!Changed)
 273     Changed = simplifyCommonValuePhi(P, LVI, DT);
 274
 275   if (Changed)
 276     ++NumPhis;
 277
 278   return Changed;
 279 }
 280
 281 static bool processMemAccess(Instruction *I, LazyValueInfo *LVI) {
 282   Value *Pointer = nullptr;
 283   if (LoadInst *L = dyn_cast<LoadInst>(I))
 284     Pointer = L->getPointerOperand();
 285   else
 286     Pointer = cast<StoreInst>(I)->getPointerOperand();
 287
 288   if (isa<Constant>(Pointer)) return false;
 289
 290   Constant *C = LVI->getConstant(Pointer, I);
 291   if (!C) return false;
 292
 293   ++NumMemAccess;
 294   I->replaceUsesOfWith(Pointer, C);
 295   return true;
 296 }
 297
 298 /// See if LazyValueInfo's ability to exploit edge conditions or range
 299 /// information is sufficient to prove this comparison. Even for local
 300 /// conditions, this can sometimes prove conditions instcombine can't by
 301 /// exploiting range information.
 302 static bool processCmp(CmpInst *Cmp, LazyValueInfo *LVI) {
 303   Value *Op0 = Cmp->getOperand(0);
 304   auto *C = dyn_cast<Constant>(Cmp->getOperand(1));
 305   if (!C)
 306     return false;
 307
 308   LazyValueInfo::Tristate Result =
 309       LVI->getPredicateAt(Cmp->getPredicate(), Op0, C, Cmp,
 310                           /*UseBlockValue=*/true);
 311   if (Result == LazyValueInfo::Unknown)
 312     return false;
 313
 314   ++NumCmps;
 315   Constant *TorF = ConstantInt::get(Type::getInt1Ty(Cmp->getContext()), Result);
 316   Cmp->replaceAllUsesWith(TorF);
 317   Cmp->eraseFromParent();
 318   return true;
 319 }
 320
 321 /// Simplify a switch instruction by removing cases which can never fire. If the
 322 /// uselessness of a case could be determined locally then constant propagation
 323 /// would already have figured it out. Instead, walk the predecessors and
 324 /// statically evaluate cases based on information available on that edge. Cases
 325 /// that cannot fire no matter what the incoming edge can safely be removed. If
 326 /// a case fires on every incoming edge then the entire switch can be removed
 327 /// and replaced with a branch to the case destination.
 328 static bool processSwitch(SwitchInst *I, LazyValueInfo *LVI,
 329                           DominatorTree *DT) {
 330   DomTreeUpdater DTU(*DT, DomTreeUpdater::UpdateStrategy::Lazy);
 331   Value *Cond = I->getCondition();
 332   BasicBlock *BB = I->getParent();
 333
 334   // Analyse each switch case in turn.
 335   bool Changed = false;
 336   DenseMap<BasicBlock*, int> SuccessorsCount;
 337   for (auto *Succ : successors(BB))
 338     SuccessorsCount[Succ]++;
 339
 340   { // Scope for SwitchInstProfUpdateWrapper. It must not live during
 341     // ConstantFoldTerminator() as the underlying SwitchInst can be changed.
 342     SwitchInstProfUpdateWrapper SI(*I);
 343
 344     for (auto CI = SI->case_begin(), CE = SI->case_end(); CI != CE;) {
 345       ConstantInt *Case = CI->getCaseValue();
 346       LazyValueInfo::Tristate State =
 347           LVI->getPredicateAt(CmpInst::ICMP_EQ, Cond, Case, I,
 348                               /* UseBlockValue */ true);
 349
 350       if (State == LazyValueInfo::False) {
 351         // This case never fires - remove it.
 352         BasicBlock *Succ = CI->getCaseSuccessor();
 353         Succ->removePredecessor(BB);
 354         CI = SI.removeCase(CI);
 355         CE = SI->case_end();
 356
 357         // The condition can be modified by removePredecessor's PHI simplification
 358         // logic.
 359         Cond = SI->getCondition();
 360
 361         ++NumDeadCases;
 362         Changed = true;
 363         if (--SuccessorsCount[Succ] == 0)
 364           DTU.applyUpdatesPermissive({{DominatorTree::Delete, BB, Succ}});
 365         continue;
 366       }
 367       if (State == LazyValueInfo::True) {
 368         // This case always fires.  Arrange for the switch to be turned into an
 369         // unconditional branch by replacing the switch condition with the case
 370         // value.
 371         SI->setCondition(Case);
 372         NumDeadCases += SI->getNumCases();
 373         Changed = true;
 374         break;
 375       }
 376
 377       // Increment the case iterator since we didn't delete it.
 378       ++CI;
 379     }
 380   }
 381
 382   if (Changed)
 383     // If the switch has been simplified to the point where it can be replaced
 384     // by a branch then do so now.
 385     ConstantFoldTerminator(BB, /*DeleteDeadConditions = */ false,
 386                            /*TLI = */ nullptr, &DTU);
 387   return Changed;
 388 }
 389
 390 // See if we can prove that the given binary op intrinsic will not overflow.
 391 static bool willNotOverflow(BinaryOpIntrinsic *BO, LazyValueInfo *LVI) {
 392   ConstantRange LRange = LVI->getConstantRange(BO->getLHS(), BO);
 393   ConstantRange RRange = LVI->getConstantRange(BO->getRHS(), BO);
 394   ConstantRange NWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
 395       BO->getBinaryOp(), RRange, BO->getNoWrapKind());
 396   return NWRegion.contains(LRange);
 397 }
 398
 399 static void setDeducedOverflowingFlags(Value *V, Instruction::BinaryOps Opcode,
 400                                        bool NewNSW, bool NewNUW) {
 401   Statistic *OpcNW, *OpcNSW, *OpcNUW;
 402   switch (Opcode) {
 403   case Instruction::Add:
 404     OpcNW = &NumAddNW;
 405     OpcNSW = &NumAddNSW;
 406     OpcNUW = &NumAddNUW;
 407     break;
 408   case Instruction::Sub:
 409     OpcNW = &NumSubNW;
 410     OpcNSW = &NumSubNSW;
 411     OpcNUW = &NumSubNUW;
 412     break;
 413   case Instruction::Mul:
 414     OpcNW = &NumMulNW;
 415     OpcNSW = &NumMulNSW;
 416     OpcNUW = &NumMulNUW;
 417     break;
 418   case Instruction::Shl:
 419     OpcNW = &NumShlNW;
 420     OpcNSW = &NumShlNSW;
 421     OpcNUW = &NumShlNUW;
 422     break;
 423   default:
 424     llvm_unreachable("Will not be called with other binops");
 425   }
 426
 427   auto *Inst = dyn_cast<Instruction>(V);
 428   if (NewNSW) {
 429     ++NumNW;
 430     ++*OpcNW;
 431     ++NumNSW;
 432     ++*OpcNSW;
 433     if (Inst)
 434       Inst->setHasNoSignedWrap();
 435   }
 436   if (NewNUW) {
 437     ++NumNW;
 438     ++*OpcNW;
 439     ++NumNUW;
 440     ++*OpcNUW;
 441     if (Inst)
 442       Inst->setHasNoUnsignedWrap();
 443   }
 444 }
 445
 446 static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI);
 447
 448 // See if @llvm.abs argument is alays positive/negative, and simplify.
 449 // Notably, INT_MIN can belong to either range, regardless of the NSW,
 450 // because it is negation-invariant.
 451 static bool processAbsIntrinsic(IntrinsicInst *II, LazyValueInfo *LVI) {
 452   Value *X = II->getArgOperand(0);
 453   bool IsIntMinPoison = cast<ConstantInt>(II->getArgOperand(1))->isOne();
 454
 455   Type *Ty = X->getType();
 456   Constant *IntMin =
 457       ConstantInt::get(Ty, APInt::getSignedMinValue(Ty->getScalarSizeInBits()));
 458   LazyValueInfo::Tristate Result;
 459
 460   // Is X in [0, IntMin]?  NOTE: INT_MIN is fine!
 461   Result = LVI->getPredicateAt(CmpInst::Predicate::ICMP_ULE, X, IntMin, II,
 462                                /*UseBlockValue=*/true);
 463   if (Result == LazyValueInfo::True) {
 464     ++NumAbs;
 465     II->replaceAllUsesWith(X);
 466     II->eraseFromParent();
 467     return true;
 468   }
 469
 470   // Is X in [IntMin, 0]?  NOTE: INT_MIN is fine!
 471   Constant *Zero = ConstantInt::getNullValue(Ty);
 472   Result = LVI->getPredicateAt(CmpInst::Predicate::ICMP_SLE, X, Zero, II,
 473                                /*UseBlockValue=*/true);
 474   assert(Result != LazyValueInfo::False && "Should have been handled already.");
 475
 476   if (Result == LazyValueInfo::Unknown) {
 477     // Argument's range crosses zero.
 478     bool Changed = false;
 479     if (!IsIntMinPoison) {
 480       // Can we at least tell that the argument is never INT_MIN?
 481       Result = LVI->getPredicateAt(CmpInst::Predicate::ICMP_NE, X, IntMin, II,
 482                                    /*UseBlockValue=*/true);
 483       if (Result == LazyValueInfo::True) {
 484         ++NumNSW;
 485         ++NumSubNSW;
 486         II->setArgOperand(1, ConstantInt::getTrue(II->getContext()));
 487         Changed = true;
 488       }
 489     }
 490     return Changed;
 491   }
 492
 493   IRBuilder<> B(II);
 494   Value *NegX = B.CreateNeg(X, II->getName(), /*HasNUW=*/false,
 495                             /*HasNSW=*/IsIntMinPoison);
 496   ++NumAbs;
 497   II->replaceAllUsesWith(NegX);
 498   II->eraseFromParent();
 499
 500   // See if we can infer some no-wrap flags.
 501   if (auto *BO = dyn_cast<BinaryOperator>(NegX))
 502     processBinOp(BO, LVI);
 503
 504   return true;
 505 }
 506
 507 // See if this min/max intrinsic always picks it's one specific operand.
 508 static bool processMinMaxIntrinsic(MinMaxIntrinsic *MM, LazyValueInfo *LVI) {
 509   CmpInst::Predicate Pred = CmpInst::getNonStrictPredicate(MM->getPredicate());
 510   LazyValueInfo::Tristate Result = LVI->getPredicateAt(
 511       Pred, MM->getLHS(), MM->getRHS(), MM, /*UseBlockValue=*/true);
 512   if (Result == LazyValueInfo::Unknown)
 513     return false;
 514
 515   ++NumMinMax;
 516   MM->replaceAllUsesWith(MM->getOperand(!Result));
 517   MM->eraseFromParent();
 518   return true;
 519 }
 520
 521 // Rewrite this with.overflow intrinsic as non-overflowing.
 522 static bool processOverflowIntrinsic(WithOverflowInst *WO, LazyValueInfo *LVI) {
 523   IRBuilder<> B(WO);
 524   Instruction::BinaryOps Opcode = WO->getBinaryOp();
 525   bool NSW = WO->isSigned();
 526   bool NUW = !WO->isSigned();
 527
 528   Value *NewOp =
 529       B.CreateBinOp(Opcode, WO->getLHS(), WO->getRHS(), WO->getName());
 530   setDeducedOverflowingFlags(NewOp, Opcode, NSW, NUW);
 531
 532   StructType *ST = cast<StructType>(WO->getType());
 533   Constant *Struct = ConstantStruct::get(ST,
 534       { UndefValue::get(ST->getElementType(0)),
 535         ConstantInt::getFalse(ST->getElementType(1)) });
 536   Value *NewI = B.CreateInsertValue(Struct, NewOp, 0);
 537   WO->replaceAllUsesWith(NewI);
 538   WO->eraseFromParent();
 539   ++NumOverflows;
 540
 541   // See if we can infer the other no-wrap too.
 542   if (auto *BO = dyn_cast<BinaryOperator>(NewOp))
 543     processBinOp(BO, LVI);
 544
 545   return true;
 546 }
 547
 548 static bool processSaturatingInst(SaturatingInst *SI, LazyValueInfo *LVI) {
 549   Instruction::BinaryOps Opcode = SI->getBinaryOp();
 550   bool NSW = SI->isSigned();
 551   bool NUW = !SI->isSigned();
 552   BinaryOperator *BinOp = BinaryOperator::Create(
 553       Opcode, SI->getLHS(), SI->getRHS(), SI->getName(), SI);
 554   BinOp->setDebugLoc(SI->getDebugLoc());
 555   setDeducedOverflowingFlags(BinOp, Opcode, NSW, NUW);
 556
 557   SI->replaceAllUsesWith(BinOp);
 558   SI->eraseFromParent();
 559   ++NumSaturating;
 560
 561   // See if we can infer the other no-wrap too.
 562   if (auto *BO = dyn_cast<BinaryOperator>(BinOp))
 563     processBinOp(BO, LVI);
 564
 565   return true;
 566 }
 567
 568 /// Infer nonnull attributes for the arguments at the specified callsite.
 569 static bool processCallSite(CallBase &CB, LazyValueInfo *LVI) {
 570
 571   if (CB.getIntrinsicID() == Intrinsic::abs) {
 572     return processAbsIntrinsic(&cast<IntrinsicInst>(CB), LVI);
 573   }
 574
 575   if (auto *MM = dyn_cast<MinMaxIntrinsic>(&CB)) {
 576     return processMinMaxIntrinsic(MM, LVI);
 577   }
 578
 579   if (auto *WO = dyn_cast<WithOverflowInst>(&CB)) {
 580     if (WO->getLHS()->getType()->isIntegerTy() && willNotOverflow(WO, LVI)) {
 581       return processOverflowIntrinsic(WO, LVI);
 582     }
 583   }
 584
 585   if (auto *SI = dyn_cast<SaturatingInst>(&CB)) {
 586     if (SI->getType()->isIntegerTy() && willNotOverflow(SI, LVI)) {
 587       return processSaturatingInst(SI, LVI);
 588     }
 589   }
 590
 591   bool Changed = false;
 592
 593   // Deopt bundle operands are intended to capture state with minimal
 594   // perturbance of the code otherwise.  If we can find a constant value for
 595   // any such operand and remove a use of the original value, that's
 596   // desireable since it may allow further optimization of that value (e.g. via
 597   // single use rules in instcombine).  Since deopt uses tend to,
 598   // idiomatically, appear along rare conditional paths, it's reasonable likely
 599   // we may have a conditional fact with which LVI can fold.
 600   if (auto DeoptBundle = CB.getOperandBundle(LLVMContext::OB_deopt)) {
 601     for (const Use &ConstU : DeoptBundle->Inputs) {
 602       Use &U = const_cast<Use&>(ConstU);
 603       Value *V = U.get();
 604       if (V->getType()->isVectorTy()) continue;
 605       if (isa<Constant>(V)) continue;
 606
 607       Constant *C = LVI->getConstant(V, &CB);
 608       if (!C) continue;
 609       U.set(C);
 610       Changed = true;
 611     }
 612   }
 613
 614   SmallVector<unsigned, 4> ArgNos;
 615   unsigned ArgNo = 0;
 616
 617   for (Value *V : CB.args()) {
 618     PointerType *Type = dyn_cast<PointerType>(V->getType());
 619     // Try to mark pointer typed parameters as non-null.  We skip the
 620     // relatively expensive analysis for constants which are obviously either
 621     // null or non-null to start with.
 622     if (Type && !CB.paramHasAttr(ArgNo, Attribute::NonNull) &&
 623         !isa<Constant>(V) &&
 624         LVI->getPredicateAt(ICmpInst::ICMP_EQ, V,
 625                             ConstantPointerNull::get(Type), &CB,
 626                             /*UseBlockValue=*/false) == LazyValueInfo::False)
 627       ArgNos.push_back(ArgNo);
 628     ArgNo++;
 629   }
 630
 631   assert(ArgNo == CB.arg_size() && "sanity check");
 632
 633   if (ArgNos.empty())
 634     return Changed;
 635
 636   NumNonNull += ArgNos.size();
 637   AttributeList AS = CB.getAttributes();
 638   LLVMContext &Ctx = CB.getContext();
 639   AS = AS.addParamAttribute(Ctx, ArgNos,
 640                             Attribute::get(Ctx, Attribute::NonNull));
 641   CB.setAttributes(AS);
 642
 643   return true;
 644 }
 645
 646 static bool isNonNegative(Value *V, LazyValueInfo *LVI, Instruction *CxtI) {
 647   Constant *Zero = ConstantInt::get(V->getType(), 0);
 648   auto Result = LVI->getPredicateAt(ICmpInst::ICMP_SGE, V, Zero, CxtI,
 649                                     /*UseBlockValue=*/true);
 650   return Result == LazyValueInfo::True;
 651 }
 652
 653 static bool isNonPositive(Value *V, LazyValueInfo *LVI, Instruction *CxtI) {
 654   Constant *Zero = ConstantInt::get(V->getType(), 0);
 655   auto Result = LVI->getPredicateAt(ICmpInst::ICMP_SLE, V, Zero, CxtI,
 656                                     /*UseBlockValue=*/true);
 657   return Result == LazyValueInfo::True;
 658 }
 659
 660 enum class Domain { NonNegative, NonPositive, Unknown };
 661
 662 Domain getDomain(Value *V, LazyValueInfo *LVI, Instruction *CxtI) {
 663   if (isNonNegative(V, LVI, CxtI))
 664     return Domain::NonNegative;
 665   if (isNonPositive(V, LVI, CxtI))
 666     return Domain::NonPositive;
 667   return Domain::Unknown;
 668 }
 669
 670 /// Try to shrink a sdiv/srem's width down to the smallest power of two that's
 671 /// sufficient to contain its operands.
 672 static bool narrowSDivOrSRem(BinaryOperator *Instr, LazyValueInfo *LVI) {
 673   assert(Instr->getOpcode() == Instruction::SDiv ||
 674          Instr->getOpcode() == Instruction::SRem);
 675   if (Instr->getType()->isVectorTy())
 676     return false;
 677
 678   // Find the smallest power of two bitwidth that's sufficient to hold Instr's
 679   // operands.
 680   unsigned OrigWidth = Instr->getType()->getIntegerBitWidth();
 681
 682   // What is the smallest bit width that can accomodate the entire value ranges
 683   // of both of the operands?
 684   std::array<Optional<ConstantRange>, 2> CRs;
 685   unsigned MinSignedBits = 0;
 686   for (auto I : zip(Instr->operands(), CRs)) {
 687     std::get<1>(I) = LVI->getConstantRange(std::get<0>(I), Instr);
 688     MinSignedBits = std::max(std::get<1>(I)->getMinSignedBits(), MinSignedBits);
 689   }
 690
 691   // sdiv/srem is UB if divisor is -1 and divident is INT_MIN, so unless we can
 692   // prove that such a combination is impossible, we need to bump the bitwidth.
 693   if (CRs[1]->contains(APInt::getAllOnesValue(OrigWidth)) &&
 694       CRs[0]->contains(
 695           APInt::getSignedMinValue(MinSignedBits).sextOrSelf(OrigWidth)))
 696     ++MinSignedBits;
 697
 698   // Don't shrink below 8 bits wide.
 699   unsigned NewWidth = std::max<unsigned>(PowerOf2Ceil(MinSignedBits), 8);
 700
 701   // NewWidth might be greater than OrigWidth if OrigWidth is not a power of
 702   // two.
 703   if (NewWidth >= OrigWidth)
 704     return false;
 705
 706   ++NumSDivSRemsNarrowed;
 707   IRBuilder<> B{Instr};
 708   auto *TruncTy = Type::getIntNTy(Instr->getContext(), NewWidth);
 709   auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
 710                                      Instr->getName() + ".lhs.trunc");
 711   auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
 712                                      Instr->getName() + ".rhs.trunc");
 713   auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
 714   auto *Sext = B.CreateSExt(BO, Instr->getType(), Instr->getName() + ".sext");
 715   if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
 716     if (BinOp->getOpcode() == Instruction::SDiv)
 717       BinOp->setIsExact(Instr->isExact());
 718
 719   Instr->replaceAllUsesWith(Sext);
 720   Instr->eraseFromParent();
 721   return true;
 722 }
 723
 724 /// Try to shrink a udiv/urem's width down to the smallest power of two that's
 725 /// sufficient to contain its operands.
 726 static bool processUDivOrURem(BinaryOperator *Instr, LazyValueInfo *LVI) {
 727   assert(Instr->getOpcode() == Instruction::UDiv ||
 728          Instr->getOpcode() == Instruction::URem);
 729   if (Instr->getType()->isVectorTy())
 730     return false;
 731
 732   // Find the smallest power of two bitwidth that's sufficient to hold Instr's
 733   // operands.
 734
 735   // What is the smallest bit width that can accomodate the entire value ranges
 736   // of both of the operands?
 737   unsigned MaxActiveBits = 0;
 738   for (Value *Operand : Instr->operands()) {
 739     ConstantRange CR = LVI->getConstantRange(Operand, Instr);
 740     MaxActiveBits = std::max(CR.getActiveBits(), MaxActiveBits);
 741   }
 742   // Don't shrink below 8 bits wide.
 743   unsigned NewWidth = std::max<unsigned>(PowerOf2Ceil(MaxActiveBits), 8);
 744
 745   // NewWidth might be greater than OrigWidth if OrigWidth is not a power of
 746   // two.
 747   if (NewWidth >= Instr->getType()->getIntegerBitWidth())
 748     return false;
 749
 750   ++NumUDivURemsNarrowed;
 751   IRBuilder<> B{Instr};
 752   auto *TruncTy = Type::getIntNTy(Instr->getContext(), NewWidth);
 753   auto *LHS = B.CreateTruncOrBitCast(Instr->getOperand(0), TruncTy,
 754                                      Instr->getName() + ".lhs.trunc");
 755   auto *RHS = B.CreateTruncOrBitCast(Instr->getOperand(1), TruncTy,
 756                                      Instr->getName() + ".rhs.trunc");
 757   auto *BO = B.CreateBinOp(Instr->getOpcode(), LHS, RHS, Instr->getName());
 758   auto *Zext = B.CreateZExt(BO, Instr->getType(), Instr->getName() + ".zext");
 759   if (auto *BinOp = dyn_cast<BinaryOperator>(BO))
 760     if (BinOp->getOpcode() == Instruction::UDiv)
 761       BinOp->setIsExact(Instr->isExact());
 762
 763   Instr->replaceAllUsesWith(Zext);
 764   Instr->eraseFromParent();
 765   return true;
 766 }
 767
 768 static bool processSRem(BinaryOperator *SDI, LazyValueInfo *LVI) {
 769   assert(SDI->getOpcode() == Instruction::SRem);
 770   if (SDI->getType()->isVectorTy())
 771     return false;
 772
 773   struct Operand {
 774     Value *V;
 775     Domain D;
 776   };
 777   std::array<Operand, 2> Ops;
 778
 779   for (const auto I : zip(Ops, SDI->operands())) {
 780     Operand &Op = std::get<0>(I);
 781     Op.V = std::get<1>(I);
 782     Op.D = getDomain(Op.V, LVI, SDI);
 783     if (Op.D == Domain::Unknown)
 784       return false;
 785   }
 786
 787   // We know domains of both of the operands!
 788   ++NumSRems;
 789
 790   // We need operands to be non-negative, so negate each one that isn't.
 791   for (Operand &Op : Ops) {
 792     if (Op.D == Domain::NonNegative)
 793       continue;
 794     auto *BO =
 795         BinaryOperator::CreateNeg(Op.V, Op.V->getName() + ".nonneg", SDI);
 796     BO->setDebugLoc(SDI->getDebugLoc());
 797     Op.V = BO;
 798   }
 799
 800   auto *URem =
 801       BinaryOperator::CreateURem(Ops[0].V, Ops[1].V, SDI->getName(), SDI);
 802   URem->setDebugLoc(SDI->getDebugLoc());
 803
 804   Value *Res = URem;
 805
 806   // If the divident was non-positive, we need to negate the result.
 807   if (Ops[0].D == Domain::NonPositive)
 808     Res = BinaryOperator::CreateNeg(Res, Res->getName() + ".neg", SDI);
 809
 810   SDI->replaceAllUsesWith(Res);
 811   SDI->eraseFromParent();
 812
 813   // Try to simplify our new urem.
 814   processUDivOrURem(URem, LVI);
 815
 816   return true;
 817 }
 818
 819 /// See if LazyValueInfo's ability to exploit edge conditions or range
 820 /// information is sufficient to prove the signs of both operands of this SDiv.
 821 /// If this is the case, replace the SDiv with a UDiv. Even for local
 822 /// conditions, this can sometimes prove conditions instcombine can't by
 823 /// exploiting range information.
 824 static bool processSDiv(BinaryOperator *SDI, LazyValueInfo *LVI) {
 825   assert(SDI->getOpcode() == Instruction::SDiv);
 826   if (SDI->getType()->isVectorTy())
 827     return false;
 828
 829   struct Operand {
 830     Value *V;
 831     Domain D;
 832   };
 833   std::array<Operand, 2> Ops;
 834
 835   for (const auto I : zip(Ops, SDI->operands())) {
 836     Operand &Op = std::get<0>(I);
 837     Op.V = std::get<1>(I);
 838     Op.D = getDomain(Op.V, LVI, SDI);
 839     if (Op.D == Domain::Unknown)
 840       return false;
 841   }
 842
 843   // We know domains of both of the operands!
 844   ++NumSDivs;
 845
 846   // We need operands to be non-negative, so negate each one that isn't.
 847   for (Operand &Op : Ops) {
 848     if (Op.D == Domain::NonNegative)
 849       continue;
 850     auto *BO =
 851         BinaryOperator::CreateNeg(Op.V, Op.V->getName() + ".nonneg", SDI);
 852     BO->setDebugLoc(SDI->getDebugLoc());
 853     Op.V = BO;
 854   }
 855
 856   auto *UDiv =
 857       BinaryOperator::CreateUDiv(Ops[0].V, Ops[1].V, SDI->getName(), SDI);
 858   UDiv->setDebugLoc(SDI->getDebugLoc());
 859   UDiv->setIsExact(SDI->isExact());
 860
 861   Value *Res = UDiv;
 862
 863   // If the operands had two different domains, we need to negate the result.
 864   if (Ops[0].D != Ops[1].D)
 865     Res = BinaryOperator::CreateNeg(Res, Res->getName() + ".neg", SDI);
 866
 867   SDI->replaceAllUsesWith(Res);
 868   SDI->eraseFromParent();
 869
 870   // Try to simplify our new udiv.
 871   processUDivOrURem(UDiv, LVI);
 872
 873   return true;
 874 }
 875
 876 static bool processSDivOrSRem(BinaryOperator *Instr, LazyValueInfo *LVI) {
 877   assert(Instr->getOpcode() == Instruction::SDiv ||
 878          Instr->getOpcode() == Instruction::SRem);
 879   if (Instr->getType()->isVectorTy())
 880     return false;
 881
 882   if (Instr->getOpcode() == Instruction::SDiv)
 883     if (processSDiv(Instr, LVI))
 884       return true;
 885
 886   if (Instr->getOpcode() == Instruction::SRem)
 887     if (processSRem(Instr, LVI))
 888       return true;
 889
 890   return narrowSDivOrSRem(Instr, LVI);
 891 }
 892
 893 static bool processAShr(BinaryOperator *SDI, LazyValueInfo *LVI) {
 894   if (SDI->getType()->isVectorTy())
 895     return false;
 896
 897   if (!isNonNegative(SDI->getOperand(0), LVI, SDI))
 898     return false;
 899
 900   ++NumAShrs;
 901   auto *BO = BinaryOperator::CreateLShr(SDI->getOperand(0), SDI->getOperand(1),
 902                                         SDI->getName(), SDI);
 903   BO->setDebugLoc(SDI->getDebugLoc());
 904   BO->setIsExact(SDI->isExact());
 905   SDI->replaceAllUsesWith(BO);
 906   SDI->eraseFromParent();
 907
 908   return true;
 909 }
 910
 911 static bool processSExt(SExtInst *SDI, LazyValueInfo *LVI) {
 912   if (SDI->getType()->isVectorTy())
 913     return false;
 914
 915   Value *Base = SDI->getOperand(0);
 916
 917   if (!isNonNegative(Base, LVI, SDI))
 918     return false;
 919
 920   ++NumSExt;
 921   auto *ZExt =
 922       CastInst::CreateZExtOrBitCast(Base, SDI->getType(), SDI->getName(), SDI);
 923   ZExt->setDebugLoc(SDI->getDebugLoc());
 924   SDI->replaceAllUsesWith(ZExt);
 925   SDI->eraseFromParent();
 926
 927   return true;
 928 }
 929
 930 static bool processBinOp(BinaryOperator *BinOp, LazyValueInfo *LVI) {
 931   using OBO = OverflowingBinaryOperator;
 932
 933   if (BinOp->getType()->isVectorTy())
 934     return false;
 935
 936   bool NSW = BinOp->hasNoSignedWrap();
 937   bool NUW = BinOp->hasNoUnsignedWrap();
 938   if (NSW && NUW)
 939     return false;
 940
 941   Instruction::BinaryOps Opcode = BinOp->getOpcode();
 942   Value *LHS = BinOp->getOperand(0);
 943   Value *RHS = BinOp->getOperand(1);
 944
 945   ConstantRange LRange = LVI->getConstantRange(LHS, BinOp);
 946   ConstantRange RRange = LVI->getConstantRange(RHS, BinOp);
 947
 948   bool Changed = false;
 949   bool NewNUW = false, NewNSW = false;
 950   if (!NUW) {
 951     ConstantRange NUWRange = ConstantRange::makeGuaranteedNoWrapRegion(
 952         Opcode, RRange, OBO::NoUnsignedWrap);
 953     NewNUW = NUWRange.contains(LRange);
 954     Changed |= NewNUW;
 955   }
 956   if (!NSW) {
 957     ConstantRange NSWRange = ConstantRange::makeGuaranteedNoWrapRegion(
 958         Opcode, RRange, OBO::NoSignedWrap);
 959     NewNSW = NSWRange.contains(LRange);
 960     Changed |= NewNSW;
 961   }
 962
 963   setDeducedOverflowingFlags(BinOp, Opcode, NewNSW, NewNUW);
 964
 965   return Changed;
 966 }
 967
 968 static bool processAnd(BinaryOperator *BinOp, LazyValueInfo *LVI) {
 969   if (BinOp->getType()->isVectorTy())
 970     return false;
 971
 972   // Pattern match (and lhs, C) where C includes a superset of bits which might
 973   // be set in lhs.  This is a common truncation idiom created by instcombine.
 974   Value *LHS = BinOp->getOperand(0);
 975   ConstantInt *RHS = dyn_cast<ConstantInt>(BinOp->getOperand(1));
 976   if (!RHS || !RHS->getValue().isMask())
 977     return false;
 978
 979   // We can only replace the AND with LHS based on range info if the range does
 980   // not include undef.
 981   ConstantRange LRange =
 982       LVI->getConstantRange(LHS, BinOp, /*UndefAllowed=*/false);
 983   if (!LRange.getUnsignedMax().ule(RHS->getValue()))
 984     return false;
 985
 986   BinOp->replaceAllUsesWith(LHS);
 987   BinOp->eraseFromParent();
 988   NumAnd++;
 989   return true;
 990 }
 991
 992
 993 static Constant *getConstantAt(Value *V, Instruction *At, LazyValueInfo *LVI) {
 994   if (Constant *C = LVI->getConstant(V, At))
 995     return C;
 996
 997   // TODO: The following really should be sunk inside LVI's core algorithm, or
 998   // at least the outer shims around such.
 999   auto *C = dyn_cast<CmpInst>(V);
1000   if (!C) return nullptr;
1001
1002   Value *Op0 = C->getOperand(0);
1003   Constant *Op1 = dyn_cast<Constant>(C->getOperand(1));
1004   if (!Op1) return nullptr;
1005
1006   LazyValueInfo::Tristate Result = LVI->getPredicateAt(
1007       C->getPredicate(), Op0, Op1, At, /*UseBlockValue=*/false);
1008   if (Result == LazyValueInfo::Unknown)
1009     return nullptr;
1010
1011   return (Result == LazyValueInfo::True) ?
1012     ConstantInt::getTrue(C->getContext()) :
1013     ConstantInt::getFalse(C->getContext());
1014 }
1015
1016 static bool runImpl(Function &F, LazyValueInfo *LVI, DominatorTree *DT,
1017                     const SimplifyQuery &SQ) {
1018   bool FnChanged = false;
1019   // Visiting in a pre-order depth-first traversal causes us to simplify early
1020   // blocks before querying later blocks (which require us to analyze early
1021   // blocks).  Eagerly simplifying shallow blocks means there is strictly less
1022   // work to do for deep blocks.  This also means we don't visit unreachable
1023   // blocks.
1024   for (BasicBlock *BB : depth_first(&F.getEntryBlock())) {
1025     bool BBChanged = false;
1026     for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
1027       Instruction *II = &*BI++;
1028       switch (II->getOpcode()) {
1029       case Instruction::Select:
1030         BBChanged |= processSelect(cast<SelectInst>(II), LVI);
1031         break;
1032       case Instruction::PHI:
1033         BBChanged |= processPHI(cast<PHINode>(II), LVI, DT, SQ);
1034         break;
1035       case Instruction::ICmp:
1036       case Instruction::FCmp:
1037         BBChanged |= processCmp(cast<CmpInst>(II), LVI);
1038         break;
1039       case Instruction::Load:
1040       case Instruction::Store:
1041         BBChanged |= processMemAccess(II, LVI);
1042         break;
1043       case Instruction::Call:
1044       case Instruction::Invoke:
1045         BBChanged |= processCallSite(cast<CallBase>(*II), LVI);
1046         break;
1047       case Instruction::SRem:
1048       case Instruction::SDiv:
1049         BBChanged |= processSDivOrSRem(cast<BinaryOperator>(II), LVI);
1050         break;
1051       case Instruction::UDiv:
1052       case Instruction::URem:
1053         BBChanged |= processUDivOrURem(cast<BinaryOperator>(II), LVI);
1054         break;
1055       case Instruction::AShr:
1056         BBChanged |= processAShr(cast<BinaryOperator>(II), LVI);
1057         break;
1058       case Instruction::SExt:
1059         BBChanged |= processSExt(cast<SExtInst>(II), LVI);
1060         break;
1061       case Instruction::Add:
1062       case Instruction::Sub:
1063       case Instruction::Mul:
1064       case Instruction::Shl:
1065         BBChanged |= processBinOp(cast<BinaryOperator>(II), LVI);
1066         break;
1067       case Instruction::And:
1068         BBChanged |= processAnd(cast<BinaryOperator>(II), LVI);
1069         break;
1070       }
1071     }
1072
1073     Instruction *Term = BB->getTerminator();
1074     switch (Term->getOpcode()) {
1075     case Instruction::Switch:
1076       BBChanged |= processSwitch(cast<SwitchInst>(Term), LVI, DT);
1077       break;
1078     case Instruction::Ret: {
1079       auto *RI = cast<ReturnInst>(Term);
1080       // Try to determine the return value if we can.  This is mainly here to
1081       // simplify the writing of unit tests, but also helps to enable IPO by
1082       // constant folding the return values of callees.
1083       auto *RetVal = RI->getReturnValue();
1084       if (!RetVal) break; // handle "ret void"
1085       if (isa<Constant>(RetVal)) break; // nothing to do
1086       if (auto *C = getConstantAt(RetVal, RI, LVI)) {
1087         ++NumReturns;
1088         RI->replaceUsesOfWith(RetVal, C);
1089         BBChanged = true;
1090       }
1091     }
1092     }
1093
1094     FnChanged |= BBChanged;
1095   }
1096
1097   return FnChanged;
1098 }
1099
1100 bool CorrelatedValuePropagation::runOnFunction(Function &F) {
1101   if (skipFunction(F))
1102     return false;
1103
1104   LazyValueInfo *LVI = &getAnalysis<LazyValueInfoWrapperPass>().getLVI();
1105   DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1106
1107   return runImpl(F, LVI, DT, getBestSimplifyQuery(*this, F));
1108 }
1109
1110 PreservedAnalyses
1111 CorrelatedValuePropagationPass::run(Function &F, FunctionAnalysisManager &AM) {
1112   LazyValueInfo *LVI = &AM.getResult<LazyValueAnalysis>(F);
1113   DominatorTree *DT = &AM.getResult<DominatorTreeAnalysis>(F);
1114
1115   bool Changed = runImpl(F, LVI, DT, getBestSimplifyQuery(AM, F));
1116
1117   PreservedAnalyses PA;
1118   if (!Changed) {
1119     PA = PreservedAnalyses::all();
1120   } else {
1121     PA.preserve<DominatorTreeAnalysis>();
1122     PA.preserve<LazyValueAnalysis>();
1123   }
1124
1125   // Keeping LVI alive is expensive, both because it uses a lot of memory, and
1126   // because invalidating values in LVI is expensive. While CVP does preserve
1127   // LVI, we know that passes after JumpThreading+CVP will not need the result
1128   // of this analysis, so we forcefully discard it early.
1129   PA.abandon<LazyValueAnalysis>();
1130   return PA;
1131 }