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1 : //===-- GlobalDCE.h - DCE unreachable internal functions ------------------===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 : //
10 : // This transform is designed to eliminate unreachable internal globals from the
11 : // program. It uses an aggressive algorithm, searching out globals that are
12 : // known to be alive. After it finds all of the globals which are needed, it
13 : // deletes whatever is left over. This allows it to delete recursive chunks of
14 : // the program which are unreachable.
15 : //
16 : //===----------------------------------------------------------------------===//
17 :
18 : #ifndef LLVM_TRANSFORMS_IPO_GLOBALDCE_H
19 : #define LLVM_TRANSFORMS_IPO_GLOBALDCE_H
20 :
21 : #include "llvm/ADT/DenseMap.h"
22 : #include "llvm/ADT/SmallSet.h"
23 : #include "llvm/IR/Module.h"
24 : #include "llvm/IR/PassManager.h"
25 : #include <unordered_map>
26 :
27 : namespace llvm {
28 :
29 : /// Pass to remove unused function declarations.
30 21600 : class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> {
31 : public:
32 : PreservedAnalyses run(Module &M, ModuleAnalysisManager &);
33 :
34 : private:
35 : SmallPtrSet<GlobalValue*, 32> AliveGlobals;
36 :
37 : /// Global -> Global that uses this global.
38 : DenseMap<GlobalValue *, SmallPtrSet<GlobalValue *, 4>> GVDependencies;
39 :
40 : /// Constant -> Globals that use this global cache.
41 : std::unordered_map<Constant *, SmallPtrSet<GlobalValue *, 8>>
42 : ConstantDependenciesCache;
43 :
44 : /// Comdat -> Globals in that Comdat section.
45 : std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
46 :
47 : void UpdateGVDependencies(GlobalValue &GV);
48 : void MarkLive(GlobalValue &GV,
49 : SmallVectorImpl<GlobalValue *> *Updates = nullptr);
50 : bool RemoveUnusedGlobalValue(GlobalValue &GV);
51 :
52 : void ComputeDependencies(Value *V, SmallPtrSetImpl<GlobalValue *> &U);
53 : };
54 :
55 : }
56 :
57 : #endif // LLVM_TRANSFORMS_IPO_GLOBALDCE_H
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