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 | |
26 | namespace llvm { |
27 | class Comdat; |
28 | class Constant; |
29 | class Function; |
30 | class GlobalVariable; |
31 | class Metadata; |
32 | class Module; |
33 | class Value; |
34 | |
35 | /// Pass to remove unused function declarations. |
36 | class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> { |
37 | public: |
38 | GlobalDCEPass(bool InLTOPostLink = false) : InLTOPostLink(InLTOPostLink) {} |
39 | |
40 | PreservedAnalyses run(Module &M, ModuleAnalysisManager &); |
41 | |
42 | void printPipeline(raw_ostream &OS, |
43 | function_ref<StringRef(StringRef)> MapClassName2PassName); |
44 | |
45 | private: |
46 | bool InLTOPostLink = false; |
47 | |
48 | SmallPtrSet<GlobalValue*, 32> AliveGlobals; |
49 | |
50 | /// Global -> Global that uses this global. |
51 | DenseMap<GlobalValue *, SmallPtrSet<GlobalValue *, 4>> GVDependencies; |
52 | |
53 | /// Constant -> Globals that use this global cache. |
54 | std::unordered_map<Constant *, SmallPtrSet<GlobalValue *, 8>> |
55 | ConstantDependenciesCache; |
56 | |
57 | /// Comdat -> Globals in that Comdat section. |
58 | std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers; |
59 | |
60 | /// !type metadata -> set of (vtable, offset) pairs |
61 | DenseMap<Metadata *, SmallSet<std::pair<GlobalVariable *, uint64_t>, 4>> |
62 | TypeIdMap; |
63 | |
64 | // Global variables which are vtables, and which we have enough information |
65 | // about to safely do dead virtual function elimination. |
66 | SmallPtrSet<GlobalValue *, 32> VFESafeVTables; |
67 | |
68 | void UpdateGVDependencies(GlobalValue &GV); |
69 | void MarkLive(GlobalValue &GV, |
70 | SmallVectorImpl<GlobalValue *> *Updates = nullptr); |
71 | |
72 | // Dead virtual function elimination. |
73 | void AddVirtualFunctionDependencies(Module &M); |
74 | void ScanVTables(Module &M); |
75 | void ScanTypeCheckedLoadIntrinsics(Module &M); |
76 | void ScanVTableLoad(Function *Caller, Metadata *TypeId, uint64_t CallOffset); |
77 | |
78 | void ComputeDependencies(Value *V, SmallPtrSetImpl<GlobalValue *> &U); |
79 | }; |
80 | |
81 | } |
82 | |
83 | #endif // LLVM_TRANSFORMS_IPO_GLOBALDCE_H |
84 | |