1 //===- StripSymbols.cpp - Strip symbols and debug info from a module ------===//
3 // The LLVM Compiler Infrastructure
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.
8 //===----------------------------------------------------------------------===//
10 // This file implements stripping symbols out of symbol tables.
12 // Specifically, this allows you to strip all of the symbols out of:
13 // * All functions in a module
14 // * All non-essential symbols in a module (all function symbols + all module
16 // * Debug information.
19 // * This pass makes code much less readable, so it should only be used in
20 // situations where the 'strip' utility would be used (such as reducing
21 // code size, and making it harder to reverse engineer code).
23 //===----------------------------------------------------------------------===//
25 #include "llvm/Transforms/IPO.h"
26 #include "llvm/Constants.h"
27 #include "llvm/DerivedTypes.h"
28 #include "llvm/Instructions.h"
29 #include "llvm/Module.h"
30 #include "llvm/Pass.h"
31 #include "llvm/SymbolTable.h"
35 class StripSymbols : public ModulePass {
38 StripSymbols(bool ODI = false) : OnlyDebugInfo(ODI) {}
40 virtual bool runOnModule(Module &M);
42 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
46 RegisterOpt<StripSymbols> X("strip", "Strip all symbols from a module");
49 ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) {
50 return new StripSymbols(OnlyDebugInfo);
53 static void RemoveDeadConstant(Constant *C) {
54 assert(C->use_empty() && "Constant is not dead!");
55 std::vector<Constant*> Operands;
56 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
57 if (isa<DerivedType>(C->getOperand(i)->getType()) &&
58 C->getOperand(i)->hasOneUse())
59 Operands.push_back(C->getOperand(i));
60 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
61 if (!GV->hasInternalLinkage()) return; // Don't delete non static globals.
62 GV->eraseFromParent();
64 else if (!isa<Function>(C))
67 // If the constant referenced anything, see if we can delete it as well.
68 while (!Operands.empty()) {
69 RemoveDeadConstant(Operands.back());
74 bool StripSymbols::runOnModule(Module &M) {
75 // If we're not just stripping debug info, strip all symbols from the
76 // functions and the names from any internal globals.
78 for (Module::giterator I = M.gbegin(), E = M.gend(); I != E; ++I)
79 if (I->hasInternalLinkage())
80 I->setName(""); // Internal symbols can't participate in linkage
82 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
83 if (I->hasInternalLinkage())
84 I->setName(""); // Internal symbols can't participate in linkage
85 I->getSymbolTable().strip();
89 // Strip debug info in the module if it exists. To do this, we remove
90 // llvm.dbg.func.start, llvm.dbg.stoppoint, and llvm.dbg.region.end calls, and
91 // any globals they point to if now dead.
92 Function *FuncStart = M.getNamedFunction("llvm.dbg.func.start");
93 Function *StopPoint = M.getNamedFunction("llvm.dbg.stoppoint");
94 Function *RegionEnd = M.getNamedFunction("llvm.dbg.region.end");
95 if (!FuncStart && !StopPoint && !RegionEnd)
98 std::vector<GlobalVariable*> DeadGlobals;
100 // Remove all of the calls to the debugger intrinsics, and remove them from
103 Value *RV = UndefValue::get(StopPoint->getFunctionType()->getReturnType());
104 while (!FuncStart->use_empty()) {
105 CallInst *CI = cast<CallInst>(FuncStart->use_back());
106 Value *Arg = CI->getOperand(1);
107 CI->replaceAllUsesWith(RV);
108 CI->eraseFromParent();
109 if (Arg->use_empty())
110 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Arg))
111 DeadGlobals.push_back(GV);
113 FuncStart->eraseFromParent();
116 Value *RV = UndefValue::get(StopPoint->getFunctionType()->getReturnType());
117 while (!StopPoint->use_empty()) {
118 CallInst *CI = cast<CallInst>(StopPoint->use_back());
119 Value *Arg = CI->getOperand(4);
120 CI->replaceAllUsesWith(RV);
121 CI->eraseFromParent();
122 if (Arg->use_empty())
123 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Arg))
124 DeadGlobals.push_back(GV);
126 StopPoint->eraseFromParent();
129 Value *RV = UndefValue::get(RegionEnd->getFunctionType()->getReturnType());
130 while (!RegionEnd->use_empty()) {
131 CallInst *CI = cast<CallInst>(RegionEnd->use_back());
132 CI->replaceAllUsesWith(RV);
133 CI->eraseFromParent();
135 RegionEnd->eraseFromParent();
138 // Finally, delete any internal globals that were only used by the debugger
140 while (!DeadGlobals.empty()) {
141 GlobalVariable *GV = DeadGlobals.back();
142 DeadGlobals.pop_back();
143 if (GV->hasInternalLinkage())
144 RemoveDeadConstant(GV);