Internalize.cpp revision fd93908ae8b9684fe71c239e3c6cfe13ff6a2663 
1//===-- Internalize.cpp - Mark functions internal -------------------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This pass loops over all of the functions in the input module, looking for a
11// main function.  If a main function is found, all other functions and all
12// global variables with initializers are marked as internal.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Transforms/IPO.h"
17#include "llvm/Pass.h"
18#include "llvm/Module.h"
19#include "llvm/Support/CommandLine.h"
20#include "llvm/Support/Debug.h"
21#include "llvm/ADT/Statistic.h"
22#include <fstream>
23#include <set>
24using namespace llvm;
25
26namespace {
27  Statistic<> NumFunctions("internalize", "Number of functions internalized");
28  Statistic<> NumGlobals  ("internalize", "Number of global vars internalized");
29
30  // APIFile - A file which contains a list of symbols that should not be marked
31  // external.
32  cl::opt<std::string>
33  APIFile("internalize-public-api-file", cl::value_desc("filename"),
34          cl::desc("A file containing list of symbol names to preserve"));
35
36  // APIList - A list of symbols that should not be marked internal.
37  cl::list<std::string>
38  APIList("internalize-public-api-list", cl::value_desc("list"),
39          cl::desc("A list of symbol names to preserve"),
40          cl::CommaSeparated);
41
42  class InternalizePass : public ModulePass {
43    std::set<std::string> ExternalNames;
44  public:
45    InternalizePass() {
46      if (!APIFile.empty())           // If a filename is specified, use it
47        LoadFile(APIFile.c_str());
48      else                            // Else, if a list is specified, use it.
49        ExternalNames.insert(APIList.begin(), APIList.end());
50    }
51
52    void LoadFile(const char *Filename) {
53      // Load the APIFile...
54      std::ifstream In(Filename);
55      if (!In.good()) {
56        std::cerr << "WARNING: Internalize couldn't load file '" << Filename
57                  << "'!\n";
58        return;   // Do not internalize anything...
59      }
60      while (In) {
61        std::string Symbol;
62        In >> Symbol;
63        if (!Symbol.empty())
64          ExternalNames.insert(Symbol);
65      }
66    }
67
68    virtual bool runOnModule(Module &M) {
69      // If no list or file of symbols was specified, check to see if there is a
70      // "main" symbol defined in the module.  If so, use it, otherwise do not
71      // internalize the module, it must be a library or something.
72      //
73      if (ExternalNames.empty()) {
74        Function *MainFunc = M.getMainFunction();
75        if (MainFunc == 0 || MainFunc->isExternal())
76          return false;  // No main found, must be a library...
77
78        // Preserve main, internalize all else.
79        ExternalNames.insert(MainFunc->getName());
80      }
81
82      bool Changed = false;
83
84      // Found a main function, mark all functions not named main as internal.
85      for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
86        if (!I->isExternal() &&         // Function must be defined here
87            !I->hasInternalLinkage() &&  // Can't already have internal linkage
88            !ExternalNames.count(I->getName())) {// Not marked to keep external?
89          I->setLinkage(GlobalValue::InternalLinkage);
90          Changed = true;
91          ++NumFunctions;
92          DEBUG(std::cerr << "Internalizing func " << I->getName() << "\n");
93        }
94
95      // Mark all global variables with initializers as internal as well...
96      for (Module::global_iterator I = M.global_begin(), E = M.global_end(); I != E; ++I)
97        if (!I->isExternal() && !I->hasInternalLinkage() &&
98            !ExternalNames.count(I->getName())) {
99          // Special case handling of the global ctor and dtor list.  When we
100          // internalize it, we mark it constant, which allows elimination of
101          // the list if it's empty.
102          //
103          if (I->hasAppendingLinkage() && (I->getName() == "llvm.global_ctors"||
104                                           I->getName() == "llvm.global_dtors"))
105            I->setConstant(true);
106
107          I->setLinkage(GlobalValue::InternalLinkage);
108          Changed = true;
109          ++NumGlobals;
110          DEBUG(std::cerr << "Internalizing gvar " << I->getName() << "\n");
111        }
112
113      return Changed;
114    }
115  };
116
117  RegisterOpt<InternalizePass> X("internalize", "Internalize Global Symbols");
118} // end anonymous namespace
119
120ModulePass *llvm::createInternalizePass() {
121  return new InternalizePass();
122}
123