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  static const char *const metaNames[] = {
46    // See http://en.wikipedia.org/wiki/Metasyntactic_variable
47    "foo", "bar", "baz", "quux", "barney", "snork", "zot", "blam", "hoge",
48    "wibble", "wobble", "widget", "wombat", "ham", "eggs", "pluto", "spam"
49  };
50
51  struct Renamer {
52    Renamer(unsigned int seed) {
53      prng.srand(seed);
54    }
55
56    const char *newName() {
57      return metaNames[prng.rand() % array_lengthof(metaNames)];
58    }
59
60    PRNG prng;
61  };
62
63  struct MetaRenamer : public ModulePass {
64    static char ID; // Pass identification, replacement for typeid
65    MetaRenamer() : ModulePass(ID) {
66      initializeMetaRenamerPass(*PassRegistry::getPassRegistry());
67    }
68
69    void getAnalysisUsage(AnalysisUsage &AU) const override {
70      AU.setPreservesAll();
71    }
72
73    bool runOnModule(Module &M) override {
74      // Seed our PRNG with simple additive sum of ModuleID. We're looking to
75      // simply avoid always having the same function names, and we need to
76      // remain deterministic.
77      unsigned int randSeed = 0;
78      for (auto C : M.getModuleIdentifier())
79        randSeed += C;
80
81      Renamer renamer(randSeed);
82
83      // Rename all aliases
84      for (auto AI = M.alias_begin(), AE = M.alias_end(); AI != AE; ++AI) {
85        StringRef Name = AI->getName();
86        if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
87          continue;
88
89        AI->setName("alias");
90      }
91
92      // Rename all global variables
93      for (auto GI = M.global_begin(), GE = M.global_end(); GI != GE; ++GI) {
94        StringRef Name = GI->getName();
95        if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
96          continue;
97
98        GI->setName("global");
99      }
100
101      // Rename all struct types
102      TypeFinder StructTypes;
103      StructTypes.run(M, true);
104      for (StructType *STy : StructTypes) {
105        if (STy->isLiteral() || STy->getName().empty()) continue;
106
107        SmallString<128> NameStorage;
108        STy->setName((Twine("struct.") +
109          renamer.newName()).toStringRef(NameStorage));
110      }
111
112      // Rename all functions
113      for (auto &F : M) {
114        StringRef Name = F.getName();
115        if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
116          continue;
117
118        F.setName(renamer.newName());
119        runOnFunction(F);
120      }
121      return true;
122    }
123
124    bool runOnFunction(Function &F) {
125      for (auto AI = F.arg_begin(), AE = F.arg_end(); AI != AE; ++AI)
126        if (!AI->getType()->isVoidTy())
127          AI->setName("arg");
128
129      for (auto &BB : F) {
130        BB.setName("bb");
131
132        for (auto &I : BB)
133          if (!I.getType()->isVoidTy())
134            I.setName("tmp");
135      }
136      return true;
137    }
138  };
139}
140
141char MetaRenamer::ID = 0;
142INITIALIZE_PASS(MetaRenamer, "metarenamer",
143                "Assign new names to everything", false, false)
144//===----------------------------------------------------------------------===//
145//
146// MetaRenamer - Rename everything with metasyntactic names.
147//
148ModulePass *llvm::createMetaRenamerPass() {
149  return new MetaRenamer();
150}
151