1 //===-- ExtractGV.cpp - Global Value extraction pass ----------------------===//
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 pass extracts global values
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "llvm/Transforms/IPO.h"
15 #include "llvm/ADT/SetVector.h"
16 #include "llvm/IR/Constants.h"
17 #include "llvm/IR/Instructions.h"
18 #include "llvm/IR/LLVMContext.h"
19 #include "llvm/IR/Module.h"
20 #include "llvm/Pass.h"
21 #include <algorithm>
22 using namespace llvm;
23
24 namespace {
25 /// @brief A pass to extract specific functions and their dependencies.
26 class GVExtractorPass : public ModulePass {
27 SetVector<GlobalValue *> Named;
28 bool deleteStuff;
29 public:
30 static char ID; // Pass identification, replacement for typeid
31
32 /// FunctionExtractorPass - If deleteFn is true, this pass deletes as the
33 /// specified function. Otherwise, it deletes as much of the module as
34 /// possible, except for the function specified.
35 ///
GVExtractorPass(std::vector<GlobalValue * > & GVs,bool deleteS=true)36 explicit GVExtractorPass(std::vector<GlobalValue*>& GVs, bool deleteS = true)
37 : ModulePass(ID), Named(GVs.begin(), GVs.end()), deleteStuff(deleteS) {}
38
runOnModule(Module & M)39 bool runOnModule(Module &M) {
40 // Visit the global inline asm.
41 if (!deleteStuff)
42 M.setModuleInlineAsm("");
43
44 // For simplicity, just give all GlobalValues ExternalLinkage. A trickier
45 // implementation could figure out which GlobalValues are actually
46 // referenced by the Named set, and which GlobalValues in the rest of
47 // the module are referenced by the NamedSet, and get away with leaving
48 // more internal and private things internal and private. But for now,
49 // be conservative and simple.
50
51 // Visit the GlobalVariables.
52 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
53 I != E; ++I) {
54 bool Delete =
55 deleteStuff == (bool)Named.count(I) && !I->isDeclaration();
56 if (!Delete) {
57 if (I->hasAvailableExternallyLinkage())
58 continue;
59 if (I->getName() == "llvm.global_ctors")
60 continue;
61 }
62
63 bool Local = I->isDiscardableIfUnused();
64 if (Local)
65 I->setVisibility(GlobalValue::HiddenVisibility);
66
67 if (Local || Delete)
68 I->setLinkage(GlobalValue::ExternalLinkage);
69
70 if (Delete)
71 I->setInitializer(0);
72 }
73
74 // Visit the Functions.
75 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
76 bool Delete =
77 deleteStuff == (bool)Named.count(I) && !I->isDeclaration();
78 if (!Delete) {
79 if (I->hasAvailableExternallyLinkage())
80 continue;
81 }
82
83 bool Local = I->isDiscardableIfUnused();
84 if (Local)
85 I->setVisibility(GlobalValue::HiddenVisibility);
86
87 if (Local || Delete)
88 I->setLinkage(GlobalValue::ExternalLinkage);
89
90 if (Delete)
91 I->deleteBody();
92 }
93
94 // Visit the Aliases.
95 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
96 I != E;) {
97 Module::alias_iterator CurI = I;
98 ++I;
99
100 if (CurI->isDiscardableIfUnused()) {
101 CurI->setVisibility(GlobalValue::HiddenVisibility);
102 CurI->setLinkage(GlobalValue::ExternalLinkage);
103 }
104
105 if (deleteStuff == (bool)Named.count(CurI)) {
106 Type *Ty = CurI->getType()->getElementType();
107
108 CurI->removeFromParent();
109 llvm::Value *Declaration;
110 if (FunctionType *FTy = dyn_cast<FunctionType>(Ty)) {
111 Declaration = Function::Create(FTy, GlobalValue::ExternalLinkage,
112 CurI->getName(), &M);
113
114 } else {
115 Declaration =
116 new GlobalVariable(M, Ty, false, GlobalValue::ExternalLinkage,
117 0, CurI->getName());
118
119 }
120 CurI->replaceAllUsesWith(Declaration);
121 delete CurI;
122 }
123 }
124
125 return true;
126 }
127 };
128
129 char GVExtractorPass::ID = 0;
130 }
131
createGVExtractionPass(std::vector<GlobalValue * > & GVs,bool deleteFn)132 ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue*>& GVs,
133 bool deleteFn) {
134 return new GVExtractorPass(GVs, deleteFn);
135 }
136