MetaRenamer.cpp revision 263508 
1//===- MetaRenamer.cpp - Rename everything with metasyntatic names --------===//
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 renames everything with metasyntatic names. The intent is to use
11// this pass after bugpoint reduction to conceal the nature of the original
12// program.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Transforms/IPO.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/ADT/SmallString.h"
19#include "llvm/IR/DerivedTypes.h"
20#include "llvm/IR/Function.h"
21#include "llvm/IR/Module.h"
22#include "llvm/IR/Type.h"
23#include "llvm/IR/TypeFinder.h"
24#include "llvm/Pass.h"
25using namespace llvm;
26
27namespace {
28
29  // This PRNG is from the ISO C spec. It is intentionally simple and
30  // unsuitable for cryptographic use. We're just looking for enough
31  // variety to surprise and delight users.
32  struct PRNG {
33    unsigned long next;
34
35    void srand(unsigned int seed) {
36      next = seed;
37    }
38
39    int rand() {
40      next = next * 1103515245 + 12345;
41      return (unsigned int)(next / 65536) % 32768;
42    }
43  };
44
45  struct MetaRenamer : public ModulePass {
46    static char ID; // Pass identification, replacement for typeid
47    MetaRenamer() : ModulePass(ID) {
48      initializeMetaRenamerPass(*PassRegistry::getPassRegistry());
49    }
50
51    void getAnalysisUsage(AnalysisUsage &AU) const {
52      AU.setPreservesAll();
53    }
54
55    bool runOnModule(Module &M) {
56      static const char *const metaNames[] = {
57        // See http://en.wikipedia.org/wiki/Metasyntactic_variable
58        "foo", "bar", "baz", "quux", "barney", "snork", "zot", "blam", "hoge",
59        "wibble", "wobble", "widget", "wombat", "ham", "eggs", "pluto", "spam"
60      };
61
62      // Seed our PRNG with simple additive sum of ModuleID. We're looking to
63      // simply avoid always having the same function names, and we need to
64      // remain deterministic.
65      unsigned int randSeed = 0;
66      for (std::string::const_iterator I = M.getModuleIdentifier().begin(),
67           E = M.getModuleIdentifier().end(); I != E; ++I)
68        randSeed += *I;
69
70      PRNG prng;
71      prng.srand(randSeed);
72
73      // Rename all aliases
74      for (Module::alias_iterator AI = M.alias_begin(), AE = M.alias_end();
75           AI != AE; ++AI) {
76        StringRef Name = AI->getName();
77        if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
78          continue;
79
80        AI->setName("alias");
81      }
82
83      // Rename all global variables
84      for (Module::global_iterator GI = M.global_begin(), GE = M.global_end();
85           GI != GE; ++GI) {
86        StringRef Name = GI->getName();
87        if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
88          continue;
89
90        GI->setName("global");
91      }
92
93      // Rename all struct types
94      TypeFinder StructTypes;
95      StructTypes.run(M, true);
96      for (unsigned i = 0, e = StructTypes.size(); i != e; ++i) {
97        StructType *STy = StructTypes[i];
98        if (STy->isLiteral() || STy->getName().empty()) continue;
99
100        SmallString<128> NameStorage;
101        STy->setName((Twine("struct.") + metaNames[prng.rand() %
102                     array_lengthof(metaNames)]).toStringRef(NameStorage));
103      }
104
105      // Rename all functions
106      for (Module::iterator FI = M.begin(), FE = M.end();
107           FI != FE; ++FI) {
108        StringRef Name = FI->getName();
109        if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
110          continue;
111
112        FI->setName(metaNames[prng.rand() % array_lengthof(metaNames)]);
113        runOnFunction(*FI);
114      }
115      return true;
116    }
117
118    bool runOnFunction(Function &F) {
119      for (Function::arg_iterator AI = F.arg_begin(), AE = F.arg_end();
120           AI != AE; ++AI)
121        if (!AI->getType()->isVoidTy())
122          AI->setName("arg");
123
124      for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
125        BB->setName("bb");
126
127        for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
128          if (!I->getType()->isVoidTy())
129            I->setName("tmp");
130      }
131      return true;
132    }
133  };
134}
135
136char MetaRenamer::ID = 0;
137INITIALIZE_PASS(MetaRenamer, "metarenamer",
138                "Assign new names to everything", false, false)
139//===----------------------------------------------------------------------===//
140//
141// MetaRenamer - Rename everything with metasyntactic names.
142//
143ModulePass *llvm::createMetaRenamerPass() {
144  return new MetaRenamer();
145}
146