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//===-- GlobalDCE.h - DCE unreachable internal functions ------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See 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/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include <unordered_map>
namespace llvm {
/// Pass to remove unused function declarations.
class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
PreservedAnalyses run(Module &M, ModuleAnalysisManager &);
SmallPtrSet<GlobalValue*, 32> AliveGlobals;
/// Global -> Global that uses this global.
DenseMap<GlobalValue *, SmallPtrSet<GlobalValue *, 4>> GVDependencies;
/// Constant -> Globals that use this global cache.
std::unordered_map<Constant *, SmallPtrSet<GlobalValue *, 8>>
/// Comdat -> Globals in that Comdat section.
std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
/// !type metadata -> set of (vtable, offset) pairs
DenseMap<Metadata *, SmallSet<std::pair<GlobalVariable *, uint64_t>, 4>>
// Global variables which are vtables, and which we have enough information
// about to safely do dead virtual function elimination.
SmallPtrSet<GlobalValue *, 32> VFESafeVTables;
void UpdateGVDependencies(GlobalValue &GV);
void MarkLive(GlobalValue &GV,
SmallVectorImpl<GlobalValue *> *Updates = nullptr);
bool RemoveUnusedGlobalValue(GlobalValue &GV);
// Dead virtual function elimination.
void AddVirtualFunctionDependencies(Module &M);
void ScanVTables(Module &M);
void ScanTypeCheckedLoadIntrinsics(Module &M);
void ScanVTableLoad(Function *Caller, Metadata *TypeId, uint64_t CallOffset);
void ComputeDependencies(Value *V, SmallPtrSetImpl<GlobalValue *> &U);