ExtractGV.cpp revision 56cb2298663017eb77aa4f4dda8db7ecd1b58173 
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/Instructions.h"
15#include "llvm/LLVMContext.h"
16#include "llvm/Module.h"
17#include "llvm/Pass.h"
18#include "llvm/Constants.h"
19#include "llvm/Transforms/IPO.h"
20#include "llvm/ADT/SetVector.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        if (deleteStuff == (bool)Named.count(I) && !I->isDeclaration()) {
55          I->setInitializer(0);
56        } else {
57          if (I->hasAvailableExternallyLinkage())
58            continue;
59          if (I->getName() == "llvm.global_ctors")
60            continue;
61        }
62
63        if (I->hasLocalLinkage())
64          I->setVisibility(GlobalValue::HiddenVisibility);
65        I->setLinkage(GlobalValue::ExternalLinkage);
66      }
67
68      // Visit the Functions.
69      for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
70        if (deleteStuff == (bool)Named.count(I) && !I->isDeclaration()) {
71          I->deleteBody();
72        } else {
73          if (I->hasAvailableExternallyLinkage())
74            continue;
75        }
76
77        if (I->hasLocalLinkage())
78          I->setVisibility(GlobalValue::HiddenVisibility);
79        I->setLinkage(GlobalValue::ExternalLinkage);
80      }
81
82      return true;
83    }
84  };
85
86  char GVExtractorPass::ID = 0;
87}
88
89ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue*>& GVs,
90                                         bool deleteFn) {
91  return new GVExtractorPass(GVs, deleteFn);
92}
93