LLVM 17.0.0git
GlobalDCE.h
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1//===-- GlobalDCE.h - DCE unreachable internal functions ------------------===//
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 transform is designed to eliminate unreachable internal globals from the
10// program. It uses an aggressive algorithm, searching out globals that are
11// known to be alive. After it finds all of the globals which are needed, it
12// deletes whatever is left over. This allows it to delete recursive chunks of
13// the program which are unreachable.
14//
15//===----------------------------------------------------------------------===//
16
17#ifndef LLVM_TRANSFORMS_IPO_GLOBALDCE_H
18#define LLVM_TRANSFORMS_IPO_GLOBALDCE_H
19
20#include "llvm/ADT/DenseMap.h"
21#include "llvm/ADT/SmallSet.h"
22#include "llvm/IR/GlobalValue.h"
23#include "llvm/IR/PassManager.h"
24#include <unordered_map>
25
26namespace llvm {
27class Comdat;
28class Constant;
29class Function;
30class GlobalVariable;
31class Metadata;
32class Module;
33class Value;
34
35/// Pass to remove unused function declarations.
36class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
37public:
39
40private:
42
43 /// Global -> Global that uses this global.
45
46 /// Constant -> Globals that use this global cache.
47 std::unordered_map<Constant *, SmallPtrSet<GlobalValue *, 8>>
48 ConstantDependenciesCache;
49
50 /// Comdat -> Globals in that Comdat section.
51 std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
52
53 /// !type metadata -> set of (vtable, offset) pairs
55 TypeIdMap;
56
57 // Global variables which are vtables, and which we have enough information
58 // about to safely do dead virtual function elimination.
59 SmallPtrSet<GlobalValue *, 32> VFESafeVTables;
60
61 void UpdateGVDependencies(GlobalValue &GV);
62 void MarkLive(GlobalValue &GV,
63 SmallVectorImpl<GlobalValue *> *Updates = nullptr);
64
65 // Dead virtual function elimination.
66 void AddVirtualFunctionDependencies(Module &M);
67 void ScanVTables(Module &M);
68 void ScanTypeCheckedLoadIntrinsics(Module &M);
69 void ScanVTableLoad(Function *Caller, Metadata *TypeId, uint64_t CallOffset);
70
71 void ComputeDependencies(Value *V, SmallPtrSetImpl<GlobalValue *> &U);
72};
73
74}
75
76#endif // LLVM_TRANSFORMS_IPO_GLOBALDCE_H
This file defines the DenseMap class.
Machine Check Debug Module
This header defines various interfaces for pass management in LLVM.
This file defines the SmallSet class.
A container for analyses that lazily runs them and caches their results.
Definition: PassManager.h:620
Pass to remove unused function declarations.
Definition: GlobalDCE.h:36
PreservedAnalyses run(Module &M, ModuleAnalysisManager &)
Definition: GlobalDCE.cpp:247
Root of the metadata hierarchy.
Definition: Metadata.h:61
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:65
A set of analyses that are preserved following a run of a transformation pass.
Definition: PassManager.h:152
A templated base class for SmallPtrSet which provides the typesafe interface that is common across al...
Definition: SmallPtrSet.h:344
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements.
Definition: SmallPtrSet.h:450
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: SmallVector.h:577
LLVM Value Representation.
Definition: Value.h:74
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
A CRTP mix-in to automatically provide informational APIs needed for passes.
Definition: PassManager.h:371