llvm/llvm/lib/Transforms/IPO/GlobalDCE.cpp

//===-- GlobalDCE.cpp - DCE unreachable internal functions ----------------===//
//
// 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 transform is designed to eliminate unreachable internal globals from the
// program.  It uses an aggressive algorithm, searching out globals that are
// known to be alive.  After it finds all of the globals which are needed, it
// deletes whatever is left over.  This allows it to delete recursive chunks of
// the program which are unreachable.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/IPO/GlobalDCE.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/TypeMetadataUtils.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Utils/CtorUtils.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"

usingnamespacellvm;

#define DEBUG_TYPE …

static cl::opt<bool>
    ClEnableVFE("enable-vfe", cl::Hidden, cl::init(true),
                cl::desc("Enable virtual function elimination"));

STATISTIC(NumAliases  , "Number of global aliases removed");
STATISTIC(NumFunctions, "Number of functions removed");
STATISTIC(NumIFuncs,    "Number of indirect functions removed");
STATISTIC(NumVariables, "Number of global variables removed");
STATISTIC(NumVFuncs,    "Number of virtual functions removed");

/// Returns true if F is effectively empty.
static bool isEmptyFunction(Function *F) { … }

/// Compute the set of GlobalValue that depends from V.
/// The recursion stops as soon as a GlobalValue is met.
void GlobalDCEPass::ComputeDependencies(Value *V,
                                        SmallPtrSetImpl<GlobalValue *> &Deps) { … }

void GlobalDCEPass::UpdateGVDependencies(GlobalValue &GV) { … }

/// Mark Global value as Live
void GlobalDCEPass::MarkLive(GlobalValue &GV,
                             SmallVectorImpl<GlobalValue *> *Updates) { … }

void GlobalDCEPass::ScanVTables(Module &M) { … }

void GlobalDCEPass::ScanVTableLoad(Function *Caller, Metadata *TypeId,
                                   uint64_t CallOffset) { … }

void GlobalDCEPass::ScanTypeCheckedLoadIntrinsics(Module &M) { … }

void GlobalDCEPass::AddVirtualFunctionDependencies(Module &M) { … }

PreservedAnalyses GlobalDCEPass::run(Module &M, ModuleAnalysisManager &MAM) { … }

void GlobalDCEPass::printPipeline(
    raw_ostream &OS, function_ref<StringRef(StringRef)> MapClassName2PassName) { … }