StripSymbols.cpp revision 57b83c78f56324e3a8ff636b311235f6f2350b4e
1//===- StripSymbols.cpp - Strip symbols and debug info from a module ------===// 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// The StripSymbols transformation implements code stripping. Specifically, it 11// can delete: 12// 13// * names for virtual registers 14// * symbols for internal globals and functions 15// * debug information 16// 17// Note that this transformation makes code much less readable, so it should 18// only be used in situations where the 'strip' utility would be used, such as 19// reducing code size or making it harder to reverse engineer code. 20// 21//===----------------------------------------------------------------------===// 22 23#include "llvm/Transforms/IPO.h" 24#include "llvm/Constants.h" 25#include "llvm/DerivedTypes.h" 26#include "llvm/Instructions.h" 27#include "llvm/LLVMContext.h" 28#include "llvm/Module.h" 29#include "llvm/Pass.h" 30#include "llvm/Analysis/DebugInfo.h" 31#include "llvm/ValueSymbolTable.h" 32#include "llvm/TypeSymbolTable.h" 33#include "llvm/Transforms/Utils/Local.h" 34#include "llvm/Support/Compiler.h" 35#include "llvm/ADT/SmallPtrSet.h" 36using namespace llvm; 37 38namespace { 39 class VISIBILITY_HIDDEN StripSymbols : public ModulePass { 40 bool OnlyDebugInfo; 41 public: 42 static char ID; // Pass identification, replacement for typeid 43 explicit StripSymbols(bool ODI = false) 44 : ModulePass(&ID), OnlyDebugInfo(ODI) {} 45 46 virtual bool runOnModule(Module &M); 47 48 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 49 AU.setPreservesAll(); 50 } 51 }; 52 53 class VISIBILITY_HIDDEN StripNonDebugSymbols : public ModulePass { 54 public: 55 static char ID; // Pass identification, replacement for typeid 56 explicit StripNonDebugSymbols() 57 : ModulePass(&ID) {} 58 59 virtual bool runOnModule(Module &M); 60 61 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 62 AU.setPreservesAll(); 63 } 64 }; 65 66 class VISIBILITY_HIDDEN StripDebugDeclare : public ModulePass { 67 public: 68 static char ID; // Pass identification, replacement for typeid 69 explicit StripDebugDeclare() 70 : ModulePass(&ID) {} 71 72 virtual bool runOnModule(Module &M); 73 74 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 75 AU.setPreservesAll(); 76 } 77 }; 78} 79 80char StripSymbols::ID = 0; 81static RegisterPass<StripSymbols> 82X("strip", "Strip all symbols from a module"); 83 84ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) { 85 return new StripSymbols(OnlyDebugInfo); 86} 87 88char StripNonDebugSymbols::ID = 0; 89static RegisterPass<StripNonDebugSymbols> 90Y("strip-nondebug", "Strip all symbols, except dbg symbols, from a module"); 91 92ModulePass *llvm::createStripNonDebugSymbolsPass() { 93 return new StripNonDebugSymbols(); 94} 95 96char StripDebugDeclare::ID = 0; 97static RegisterPass<StripDebugDeclare> 98Z("strip-debug-declare", "Strip all llvm.dbg.declare intrinsics"); 99 100ModulePass *llvm::createStripDebugDeclarePass() { 101 return new StripDebugDeclare(); 102} 103 104/// OnlyUsedBy - Return true if V is only used by Usr. 105static bool OnlyUsedBy(Value *V, Value *Usr) { 106 for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) { 107 User *U = *I; 108 if (U != Usr) 109 return false; 110 } 111 return true; 112} 113 114static void RemoveDeadConstant(Constant *C) { 115 assert(C->use_empty() && "Constant is not dead!"); 116 SmallPtrSet<Constant *, 4> Operands; 117 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) 118 if (isa<DerivedType>(C->getOperand(i)->getType()) && 119 OnlyUsedBy(C->getOperand(i), C)) 120 Operands.insert(C->getOperand(i)); 121 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 122 if (!GV->hasLocalLinkage()) return; // Don't delete non static globals. 123 GV->eraseFromParent(); 124 } 125 else if (!isa<Function>(C)) 126 if (isa<CompositeType>(C->getType())) 127 C->destroyConstant(); 128 129 // If the constant referenced anything, see if we can delete it as well. 130 for (SmallPtrSet<Constant *, 4>::iterator OI = Operands.begin(), 131 OE = Operands.end(); OI != OE; ++OI) 132 RemoveDeadConstant(*OI); 133} 134 135// Strip the symbol table of its names. 136// 137static void StripSymtab(ValueSymbolTable &ST, bool PreserveDbgInfo) { 138 for (ValueSymbolTable::iterator VI = ST.begin(), VE = ST.end(); VI != VE; ) { 139 Value *V = VI->getValue(); 140 ++VI; 141 if (!isa<GlobalValue>(V) || cast<GlobalValue>(V)->hasLocalLinkage()) { 142 if (!PreserveDbgInfo || !V->getName().startswith("llvm.dbg")) 143 // Set name to "", removing from symbol table! 144 V->setName(""); 145 } 146 } 147} 148 149// Strip the symbol table of its names. 150static void StripTypeSymtab(TypeSymbolTable &ST, bool PreserveDbgInfo) { 151 for (TypeSymbolTable::iterator TI = ST.begin(), E = ST.end(); TI != E; ) { 152 if (PreserveDbgInfo && strncmp(TI->first.c_str(), "llvm.dbg", 8) == 0) 153 ++TI; 154 else 155 ST.remove(TI++); 156 } 157} 158 159/// Find values that are marked as llvm.used. 160static void findUsedValues(GlobalVariable *LLVMUsed, 161 SmallPtrSet<const GlobalValue*, 8> &UsedValues) { 162 if (LLVMUsed == 0) return; 163 UsedValues.insert(LLVMUsed); 164 165 ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer()); 166 if (Inits == 0) return; 167 168 for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i) 169 if (GlobalValue *GV = 170 dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts())) 171 UsedValues.insert(GV); 172} 173 174/// StripSymbolNames - Strip symbol names. 175static bool StripSymbolNames(Module &M, bool PreserveDbgInfo) { 176 177 SmallPtrSet<const GlobalValue*, 8> llvmUsedValues; 178 findUsedValues(M.getGlobalVariable("llvm.used"), llvmUsedValues); 179 findUsedValues(M.getGlobalVariable("llvm.compiler.used"), llvmUsedValues); 180 181 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 182 I != E; ++I) { 183 if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0) 184 if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg")) 185 I->setName(""); // Internal symbols can't participate in linkage 186 } 187 188 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) { 189 if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0) 190 if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg")) 191 I->setName(""); // Internal symbols can't participate in linkage 192 StripSymtab(I->getValueSymbolTable(), PreserveDbgInfo); 193 } 194 195 // Remove all names from types. 196 StripTypeSymtab(M.getTypeSymbolTable(), PreserveDbgInfo); 197 198 return true; 199} 200 201// StripDebugInfo - Strip debug info in the module if it exists. 202// To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and 203// llvm.dbg.region.end calls, and any globals they point to if now dead. 204static bool StripDebugInfo(Module &M) { 205 206 // Remove all of the calls to the debugger intrinsics, and remove them from 207 // the module. 208 Function *FuncStart = M.getFunction("llvm.dbg.func.start"); 209 Function *StopPoint = M.getFunction("llvm.dbg.stoppoint"); 210 Function *RegionStart = M.getFunction("llvm.dbg.region.start"); 211 Function *RegionEnd = M.getFunction("llvm.dbg.region.end"); 212 Function *Declare = M.getFunction("llvm.dbg.declare"); 213 214 if (FuncStart) { 215 while (!FuncStart->use_empty()) { 216 CallInst *CI = cast<CallInst>(FuncStart->use_back()); 217 CI->eraseFromParent(); 218 } 219 FuncStart->eraseFromParent(); 220 } 221 if (StopPoint) { 222 while (!StopPoint->use_empty()) { 223 CallInst *CI = cast<CallInst>(StopPoint->use_back()); 224 CI->eraseFromParent(); 225 } 226 StopPoint->eraseFromParent(); 227 } 228 if (RegionStart) { 229 while (!RegionStart->use_empty()) { 230 CallInst *CI = cast<CallInst>(RegionStart->use_back()); 231 CI->eraseFromParent(); 232 } 233 RegionStart->eraseFromParent(); 234 } 235 if (RegionEnd) { 236 while (!RegionEnd->use_empty()) { 237 CallInst *CI = cast<CallInst>(RegionEnd->use_back()); 238 CI->eraseFromParent(); 239 } 240 RegionEnd->eraseFromParent(); 241 } 242 if (Declare) { 243 while (!Declare->use_empty()) { 244 CallInst *CI = cast<CallInst>(Declare->use_back()); 245 CI->eraseFromParent(); 246 } 247 Declare->eraseFromParent(); 248 } 249 250 NamedMDNode *NMD = M.getNamedMetadata("llvm.dbg.gv"); 251 if (NMD) 252 NMD->eraseFromParent(); 253 254 // Remove dead metadata. 255 M.getContext().RemoveDeadMetadata(); 256 return true; 257} 258 259bool StripSymbols::runOnModule(Module &M) { 260 bool Changed = false; 261 Changed |= StripDebugInfo(M); 262 if (!OnlyDebugInfo) 263 Changed |= StripSymbolNames(M, false); 264 return Changed; 265} 266 267bool StripNonDebugSymbols::runOnModule(Module &M) { 268 return StripSymbolNames(M, true); 269} 270 271bool StripDebugDeclare::runOnModule(Module &M) { 272 273 Function *Declare = M.getFunction("llvm.dbg.declare"); 274 std::vector<Constant*> DeadConstants; 275 276 if (Declare) { 277 while (!Declare->use_empty()) { 278 CallInst *CI = cast<CallInst>(Declare->use_back()); 279 Value *Arg1 = CI->getOperand(1); 280 Value *Arg2 = CI->getOperand(2); 281 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result"); 282 CI->eraseFromParent(); 283 if (Arg1->use_empty()) { 284 if (Constant *C = dyn_cast<Constant>(Arg1)) 285 DeadConstants.push_back(C); 286 else 287 RecursivelyDeleteTriviallyDeadInstructions(Arg1); 288 } 289 if (Arg2->use_empty()) 290 if (Constant *C = dyn_cast<Constant>(Arg2)) 291 DeadConstants.push_back(C); 292 } 293 Declare->eraseFromParent(); 294 } 295 296 // Delete all llvm.dbg.global_variables. 297 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 298 I != E; ++I) { 299 GlobalVariable *GV = dyn_cast<GlobalVariable>(I); 300 if (!GV) continue; 301 if (GV->use_empty() && GV->getName().startswith("llvm.dbg.global_variable")) 302 DeadConstants.push_back(GV); 303 } 304 305 while (!DeadConstants.empty()) { 306 Constant *C = DeadConstants.back(); 307 DeadConstants.pop_back(); 308 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 309 if (GV->hasLocalLinkage()) 310 RemoveDeadConstant(GV); 311 } 312 else 313 RemoveDeadConstant(C); 314 } 315 316 return true; 317} 318