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📄 ADCE.cpp(24.71 KB)
📄 AlignmentFromAssumptions.cpp(15.9 KB)
📄 BDCE.cpp(7.42 KB)
📄 CallSiteSplitting.cpp(21.43 KB)
📄 ConstantHoisting.cpp(38.95 KB)
📄 ConstantProp.cpp(4.13 KB)
📄 CorrelatedValuePropagation.cpp(32.36 KB)
📄 DCE.cpp(6.84 KB)
📄 DeadStoreElimination.cpp(91.51 KB)
📄 DivRemPairs.cpp(15.01 KB)
📄 EarlyCSE.cpp(57.05 KB)
📄 FlattenCFGPass.cpp(2.74 KB)
📄 Float2Int.cpp(18.19 KB)
📄 GVN.cpp(100.11 KB)
📄 GVNHoist.cpp(44.85 KB)
📄 GVNSink.cpp(29.97 KB)
📄 GuardWidening.cpp(32.36 KB)
📄 IVUsersPrinter.cpp(839 B)
📄 IndVarSimplify.cpp(113.49 KB)
📄 InductiveRangeCheckElimination.cpp(72.96 KB)
📄 InferAddressSpaces.cpp(44.22 KB)
📄 InstSimplifyPass.cpp(5.39 KB)
📄 JumpThreading.cpp(115.06 KB)
📄 LICM.cpp(92.71 KB)
📄 LoopAccessAnalysisPrinter.cpp(977 B)
📄 LoopDataPrefetch.cpp(14.54 KB)
📄 LoopDeletion.cpp(11.37 KB)
📄 LoopDistribute.cpp(40.25 KB)
📄 LoopFuse.cpp(68.6 KB)
📄 LoopIdiomRecognize.cpp(69.09 KB)
📄 LoopInstSimplify.cpp(9.38 KB)
📄 LoopInterchange.cpp(60.65 KB)
📄 LoopLoadElimination.cpp(26.71 KB)
📄 LoopPassManager.cpp(4.02 KB)
📄 LoopPredication.cpp(49.21 KB)
📄 LoopRerollPass.cpp(58.54 KB)
📄 LoopRotation.cpp(4.79 KB)
📄 LoopSimplifyCFG.cpp(28.59 KB)
📄 LoopSink.cpp(14.93 KB)
📄 LoopStrengthReduce.cpp(216.88 KB)
📄 LoopUnrollAndJamPass.cpp(21.07 KB)
📄 LoopUnrollPass.cpp(60.73 KB)
📄 LoopUnswitch.cpp(64.17 KB)
📄 LoopVersioningLICM.cpp(23.65 KB)
📄 LowerAtomic.cpp(5.12 KB)
📄 LowerConstantIntrinsics.cpp(5.8 KB)
📄 LowerExpectIntrinsic.cpp(15 KB)
📄 LowerGuardIntrinsic.cpp(2.82 KB)
📄 LowerMatrixIntrinsics.cpp(73.36 KB)
📄 LowerWidenableCondition.cpp(2.75 KB)
📄 MakeGuardsExplicit.cpp(3.83 KB)
📄 MemCpyOptimizer.cpp(52.16 KB)
📄 MergeICmps.cpp(35.61 KB)
📄 MergedLoadStoreMotion.cpp(15.18 KB)
📄 NaryReassociate.cpp(19.86 KB)
📄 NewGVN.cpp(170.95 KB)
📄 PartiallyInlineLibCalls.cpp(6.22 KB)
📄 PlaceSafepoints.cpp(27.5 KB)
📄 Reassociate.cpp(95.61 KB)
📄 Reg2Mem.cpp(4.34 KB)
📄 RewriteStatepointsForGC.cpp(116.35 KB)
📄 SCCP.cpp(76.12 KB)
📄 SROA.cpp(183.83 KB)
📄 Scalar.cpp(10.08 KB)
📄 Scalarizer.cpp(32.93 KB)
📄 SeparateConstOffsetFromGEP.cpp(52.99 KB)
📄 SimpleLoopUnswitch.cpp(124.57 KB)
📄 SimplifyCFGPass.cpp(12.31 KB)
📄 Sink.cpp(10.81 KB)
📄 SpeculateAroundPHIs.cpp(35.69 KB)
📄 SpeculativeExecution.cpp(11.54 KB)
📄 StraightLineStrengthReduce.cpp(28.92 KB)
📄 StructurizeCFG.cpp(32.49 KB)
📄 TailRecursionElimination.cpp(34.9 KB)
📄 WarnMissedTransforms.cpp(6.14 KB)

Editing: DCE.cpp

//===- DCE.cpp - Code to perform dead code elimination --------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements dead inst elimination and dead code elimination.
//
// Dead Inst Elimination performs a single pass over the function removing
// instructions that are obviously dead.  Dead Code Elimination is similar, but
// it rechecks instructions that were used by removed instructions to see if
// they are newly dead.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/Scalar/DCE.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instruction.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/AssumeBundleBuilder.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;

#define DEBUG_TYPE "dce"

STATISTIC(DIEEliminated, "Number of insts removed by DIE pass");
STATISTIC(DCEEliminated, "Number of insts removed");
DEBUG_COUNTER(DCECounter, "dce-transform",
              "Controls which instructions are eliminated");

namespace {
  //===--------------------------------------------------------------------===//
  // DeadInstElimination pass implementation
  //
struct DeadInstElimination : public FunctionPass {
  static char ID; // Pass identification, replacement for typeid
  DeadInstElimination() : FunctionPass(ID) {
    initializeDeadInstEliminationPass(*PassRegistry::getPassRegistry());
  }
  bool runOnFunction(Function &F) override {
    if (skipFunction(F))
      return false;
    auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
    TargetLibraryInfo *TLI = TLIP ? &TLIP->getTLI(F) : nullptr;

bool Changed = false;
    for (auto &BB : F) {
      for (BasicBlock::iterator DI = BB.begin(); DI != BB.end(); ) {
        Instruction *Inst = &*DI++;
        if (isInstructionTriviallyDead(Inst, TLI)) {
          if (!DebugCounter::shouldExecute(DCECounter))
            continue;
          salvageDebugInfo(*Inst);
          Inst->eraseFromParent();
          Changed = true;
          ++DIEEliminated;
        }
      }
    }
    return Changed;
  }

void getAnalysisUsage(AnalysisUsage &AU) const override {
      AU.setPreservesCFG();
    }
};
}

char DeadInstElimination::ID = 0;
INITIALIZE_PASS(DeadInstElimination, "die",
                "Dead Instruction Elimination", false, false)

Pass *llvm::createDeadInstEliminationPass() {
  return new DeadInstElimination();
}

//===--------------------------------------------------------------------===//
// RedundantDbgInstElimination pass implementation
//

namespace {
struct RedundantDbgInstElimination : public FunctionPass {
  static char ID; // Pass identification, replacement for typeid
  RedundantDbgInstElimination() : FunctionPass(ID) {
    initializeRedundantDbgInstEliminationPass(*PassRegistry::getPassRegistry());
  }
  bool runOnFunction(Function &F) override {
    if (skipFunction(F))
      return false;
    bool Changed = false;
    for (auto &BB : F)
      Changed |= RemoveRedundantDbgInstrs(&BB);
    return Changed;
  }

void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.setPreservesCFG();
  }
};
}

char RedundantDbgInstElimination::ID = 0;
INITIALIZE_PASS(RedundantDbgInstElimination, "redundant-dbg-inst-elim",
                "Redundant Dbg Instruction Elimination", false, false)

Pass *llvm::createRedundantDbgInstEliminationPass() {
  return new RedundantDbgInstElimination();
}

//===--------------------------------------------------------------------===//
// DeadCodeElimination pass implementation
//

static bool DCEInstruction(Instruction *I,
                           SmallSetVector<Instruction *, 16> &WorkList,
                           const TargetLibraryInfo *TLI) {
  if (isInstructionTriviallyDead(I, TLI)) {
    if (!DebugCounter::shouldExecute(DCECounter))
      return false;

salvageDebugInfo(*I);
    salvageKnowledge(I);

// Null out all of the instruction's operands to see if any operand becomes
    // dead as we go.
    for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
      Value *OpV = I->getOperand(i);
      I->setOperand(i, nullptr);

if (!OpV->use_empty() || I == OpV)
        continue;

// If the operand is an instruction that became dead as we nulled out the
      // operand, and if it is 'trivially' dead, delete it in a future loop
      // iteration.
      if (Instruction *OpI = dyn_cast<Instruction>(OpV))
        if (isInstructionTriviallyDead(OpI, TLI))
          WorkList.insert(OpI);
    }

I->eraseFromParent();
    ++DCEEliminated;
    return true;
  }
  return false;
}

static bool eliminateDeadCode(Function &F, TargetLibraryInfo *TLI) {
  bool MadeChange = false;
  SmallSetVector<Instruction *, 16> WorkList;
  // Iterate over the original function, only adding insts to the worklist
  // if they actually need to be revisited. This avoids having to pre-init
  // the worklist with the entire function's worth of instructions.
  for (inst_iterator FI = inst_begin(F), FE = inst_end(F); FI != FE;) {
    Instruction *I = &*FI;
    ++FI;

// We're visiting this instruction now, so make sure it's not in the
    // worklist from an earlier visit.
    if (!WorkList.count(I))
      MadeChange |= DCEInstruction(I, WorkList, TLI);
  }

while (!WorkList.empty()) {
    Instruction *I = WorkList.pop_back_val();
    MadeChange |= DCEInstruction(I, WorkList, TLI);
  }
  return MadeChange;
}

PreservedAnalyses DCEPass::run(Function &F, FunctionAnalysisManager &AM) {
  if (!eliminateDeadCode(F, AM.getCachedResult<TargetLibraryAnalysis>(F)))
    return PreservedAnalyses::all();

PreservedAnalyses PA;
  PA.preserveSet<CFGAnalyses>();
  return PA;
}

namespace {
struct DCELegacyPass : public FunctionPass {
  static char ID; // Pass identification, replacement for typeid
  DCELegacyPass() : FunctionPass(ID) {
    initializeDCELegacyPassPass(*PassRegistry::getPassRegistry());
  }

bool runOnFunction(Function &F) override {
    if (skipFunction(F))
      return false;

auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
    TargetLibraryInfo *TLI = TLIP ? &TLIP->getTLI(F) : nullptr;

return eliminateDeadCode(F, TLI);
  }

void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.setPreservesCFG();
  }
};
}

char DCELegacyPass::ID = 0;
INITIALIZE_PASS(DCELegacyPass, "dce", "Dead Code Elimination", false, false)

FunctionPass *llvm::createDeadCodeEliminationPass() {
  return new DCELegacyPass();
}

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Editing: DCE.cpp

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