aboutsummaryrefslogtreecommitdiff
path: root/lib/Transforms/IPO/ExtractGV.cpp
blob: 1a3b9253d72fca8e885abf13e3f926d94dc2e71a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
//===-- ExtractGV.cpp - Global Value extraction pass ----------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass extracts global values
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include <algorithm>
using namespace llvm;

/// Make sure GV is visible from both modules. Delete is true if it is
/// being deleted from this module.
/// This also makes sure GV cannot be dropped so that references from
/// the split module remain valid.
static void makeVisible(GlobalValue &GV, bool Delete) {
  bool Local = GV.hasLocalLinkage();
  if (Local || Delete) {
    GV.setLinkage(GlobalValue::ExternalLinkage);
    if (Local)
      GV.setVisibility(GlobalValue::HiddenVisibility);
    return;
  }

  if (!GV.hasLinkOnceLinkage()) {
    assert(!GV.isDiscardableIfUnused());
    return;
  }

  // Map linkonce* to weak* so that llvm doesn't drop this GV.
  switch(GV.getLinkage()) {
  default:
    llvm_unreachable("Unexpected linkage");
  case GlobalValue::LinkOnceAnyLinkage:
    GV.setLinkage(GlobalValue::WeakAnyLinkage);
    return;
  case GlobalValue::LinkOnceODRLinkage:
    GV.setLinkage(GlobalValue::WeakODRLinkage);
    return;
  }
}

namespace {
  /// @brief A pass to extract specific functions and their dependencies.
  class GVExtractorPass : public ModulePass {
    SetVector<GlobalValue *> Named;
    bool deleteStuff;
  public:
    static char ID; // Pass identification, replacement for typeid

    /// FunctionExtractorPass - If deleteFn is true, this pass deletes as the
    /// specified function. Otherwise, it deletes as much of the module as
    /// possible, except for the function specified.
    ///
    explicit GVExtractorPass(std::vector<GlobalValue*>& GVs, bool deleteS = true)
      : ModulePass(ID), Named(GVs.begin(), GVs.end()), deleteStuff(deleteS) {}

    bool runOnModule(Module &M) override {
      // Visit the global inline asm.
      if (!deleteStuff)
        M.setModuleInlineAsm("");

      // For simplicity, just give all GlobalValues ExternalLinkage. A trickier
      // implementation could figure out which GlobalValues are actually
      // referenced by the Named set, and which GlobalValues in the rest of
      // the module are referenced by the NamedSet, and get away with leaving
      // more internal and private things internal and private. But for now,
      // be conservative and simple.

      // Visit the GlobalVariables.
      for (Module::global_iterator I = M.global_begin(), E = M.global_end();
           I != E; ++I) {
        bool Delete =
            deleteStuff == (bool)Named.count(&*I) && !I->isDeclaration();
        if (!Delete) {
          if (I->hasAvailableExternallyLinkage())
            continue;
          if (I->getName() == "llvm.global_ctors")
            continue;
        }

        makeVisible(*I, Delete);

        if (Delete) {
          // Make this a declaration and drop it's comdat.
          I->setInitializer(nullptr);
          I->setComdat(nullptr);
        }
      }

      // Visit the Functions.
      for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
        bool Delete =
            deleteStuff == (bool)Named.count(&*I) && !I->isDeclaration();
        if (!Delete) {
          if (I->hasAvailableExternallyLinkage())
            continue;
        }

        makeVisible(*I, Delete);

        if (Delete) {
          // Make this a declaration and drop it's comdat.
          I->deleteBody();
          I->setComdat(nullptr);
        }
      }

      // Visit the Aliases.
      for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
           I != E;) {
        Module::alias_iterator CurI = I;
        ++I;

        bool Delete = deleteStuff == (bool)Named.count(&*CurI);
        makeVisible(*CurI, Delete);

        if (Delete) {
          Type *Ty =  CurI->getType()->getElementType();

          CurI->removeFromParent();
          llvm::Value *Declaration;
          if (FunctionType *FTy = dyn_cast<FunctionType>(Ty)) {
            Declaration = Function::Create(FTy, GlobalValue::ExternalLinkage,
                                           CurI->getName(), &M);

          } else {
            Declaration =
              new GlobalVariable(M, Ty, false, GlobalValue::ExternalLinkage,
                                 nullptr, CurI->getName());

          }
          CurI->replaceAllUsesWith(Declaration);
          delete &*CurI;
        }
      }

      return true;
    }
  };

  char GVExtractorPass::ID = 0;
}

ModulePass *llvm::createGVExtractionPass(std::vector<GlobalValue *> &GVs,
                                         bool deleteFn) {
  return new GVExtractorPass(GVs, deleteFn);
}