ExtractGV.cpp revision 0b8c9a80f20772c3793201ab5b251d3520b9cea3 
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>
22using namespace llvm;
23
24namespace {
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    ///
36    explicit GVExtractorPass(std::vector<GlobalValue*>& GVs, bool deleteS = true)
37      : ModulePass(ID), Named(GVs.begin(), GVs.end()), deleteStuff(deleteS) {}
38
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->hasLocalLinkage();
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->hasLocalLinkage();
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->hasLocalLinkage()) {
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
132ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue*>& GVs,
133                                         bool deleteFn) {
134  return new GVExtractorPass(GVs, deleteFn);
135}
136