StripSymbols.cpp revision 734068a90fd63bfb95362a23537e1a0cbd444481
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. 175bool 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. 204bool StripDebugInfo(Module &M) { 205 206 SmallPtrSet<const GlobalValue*, 8> llvmUsedValues; 207 findUsedValues(M.getGlobalVariable("llvm.used"), llvmUsedValues); 208 findUsedValues(M.getGlobalVariable("llvm.compiler.used"), llvmUsedValues); 209 210 DebugInfoFinder DbgFinder; 211 DbgFinder.processModule(M); 212 213 // These anchors use LinkOnce linkage so that the optimizer does not 214 // remove them accidently. Set InternalLinkage for all these debug 215 // info anchors. 216 for (DebugInfoFinder::iterator I = DbgFinder.compile_unit_begin(), 217 E = DbgFinder.compile_unit_end(); I != E; ++I) 218 (*I)->setLinkage(GlobalValue::InternalLinkage); 219 for (DebugInfoFinder::iterator I = DbgFinder.global_variable_begin(), 220 E = DbgFinder.global_variable_end(); I != E; ++I) 221 (*I)->setLinkage(GlobalValue::InternalLinkage); 222 for (DebugInfoFinder::iterator I = DbgFinder.subprogram_begin(), 223 E = DbgFinder.subprogram_end(); I != E; ++I) 224 (*I)->setLinkage(GlobalValue::InternalLinkage); 225 226 227 // Delete all dbg variables. 228 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 229 I != E; ++I) { 230 GlobalVariable *GV = dyn_cast<GlobalVariable>(I); 231 if (!GV) continue; 232 if (!GV->use_empty() && llvmUsedValues.count(I) == 0) { 233 if (GV->getName().startswith("llvm.dbg")) { 234 GV->replaceAllUsesWith(UndefValue::get(GV->getType())); 235 } 236 } 237 } 238 239 Function *FuncStart = M.getFunction("llvm.dbg.func.start"); 240 Function *StopPoint = M.getFunction("llvm.dbg.stoppoint"); 241 Function *RegionStart = M.getFunction("llvm.dbg.region.start"); 242 Function *RegionEnd = M.getFunction("llvm.dbg.region.end"); 243 Function *Declare = M.getFunction("llvm.dbg.declare"); 244 245 std::vector<Constant*> DeadConstants; 246 247 // Remove all of the calls to the debugger intrinsics, and remove them from 248 // the module. 249 if (FuncStart) { 250 while (!FuncStart->use_empty()) { 251 CallInst *CI = cast<CallInst>(FuncStart->use_back()); 252 Value *Arg = CI->getOperand(1); 253 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result"); 254 CI->eraseFromParent(); 255 if (Arg->use_empty()) 256 if (Constant *C = dyn_cast<Constant>(Arg)) 257 DeadConstants.push_back(C); 258 } 259 FuncStart->eraseFromParent(); 260 } 261 if (StopPoint) { 262 while (!StopPoint->use_empty()) { 263 CallInst *CI = cast<CallInst>(StopPoint->use_back()); 264 Value *Arg = CI->getOperand(3); 265 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result"); 266 CI->eraseFromParent(); 267 if (Arg->use_empty()) 268 if (Constant *C = dyn_cast<Constant>(Arg)) 269 DeadConstants.push_back(C); 270 } 271 StopPoint->eraseFromParent(); 272 } 273 if (RegionStart) { 274 while (!RegionStart->use_empty()) { 275 CallInst *CI = cast<CallInst>(RegionStart->use_back()); 276 Value *Arg = CI->getOperand(1); 277 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result"); 278 CI->eraseFromParent(); 279 if (Arg->use_empty()) 280 if (Constant *C = dyn_cast<Constant>(Arg)) 281 DeadConstants.push_back(C); 282 } 283 RegionStart->eraseFromParent(); 284 } 285 if (RegionEnd) { 286 while (!RegionEnd->use_empty()) { 287 CallInst *CI = cast<CallInst>(RegionEnd->use_back()); 288 Value *Arg = CI->getOperand(1); 289 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result"); 290 CI->eraseFromParent(); 291 if (Arg->use_empty()) 292 if (Constant *C = dyn_cast<Constant>(Arg)) 293 DeadConstants.push_back(C); 294 } 295 RegionEnd->eraseFromParent(); 296 } 297 if (Declare) { 298 while (!Declare->use_empty()) { 299 CallInst *CI = cast<CallInst>(Declare->use_back()); 300 Value *Arg1 = CI->getOperand(1); 301 Value *Arg2 = CI->getOperand(2); 302 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result"); 303 CI->eraseFromParent(); 304 if (Arg1->use_empty()) { 305 if (Constant *C = dyn_cast<Constant>(Arg1)) 306 DeadConstants.push_back(C); 307 else 308 RecursivelyDeleteTriviallyDeadInstructions(Arg1); 309 } 310 if (Arg2->use_empty()) 311 if (Constant *C = dyn_cast<Constant>(Arg2)) 312 DeadConstants.push_back(C); 313 } 314 Declare->eraseFromParent(); 315 } 316 317 // llvm.dbg.compile_units and llvm.dbg.subprograms are marked as linkonce 318 // but since we are removing all debug information, make them internal now. 319 // FIXME: Use private linkage maybe? 320 if (Constant *C = M.getNamedGlobal("llvm.dbg.compile_units")) 321 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 322 GV->setLinkage(GlobalValue::InternalLinkage); 323 324 if (Constant *C = M.getNamedGlobal("llvm.dbg.subprograms")) 325 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 326 GV->setLinkage(GlobalValue::InternalLinkage); 327 328 if (Constant *C = M.getNamedGlobal("llvm.dbg.global_variables")) 329 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 330 GV->setLinkage(GlobalValue::InternalLinkage); 331 332 // Delete all dbg variables. 333 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 334 I != E; ++I) { 335 GlobalVariable *GV = dyn_cast<GlobalVariable>(I); 336 if (!GV) continue; 337 if (GV->use_empty() && llvmUsedValues.count(I) == 0 338 && (!GV->hasSection() 339 || strcmp(GV->getSection().c_str(), "llvm.metadata") == 0)) 340 DeadConstants.push_back(GV); 341 } 342 343 if (DeadConstants.empty()) 344 return false; 345 346 // Delete any internal globals that were only used by the debugger intrinsics. 347 while (!DeadConstants.empty()) { 348 Constant *C = DeadConstants.back(); 349 DeadConstants.pop_back(); 350 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 351 if (GV->hasLocalLinkage()) 352 RemoveDeadConstant(GV); 353 } 354 else 355 RemoveDeadConstant(C); 356 } 357 358 // Remove all llvm.dbg types. 359 TypeSymbolTable &ST = M.getTypeSymbolTable(); 360 for (TypeSymbolTable::iterator TI = ST.begin(), TE = ST.end(); TI != TE; ) { 361 if (!strncmp(TI->first.c_str(), "llvm.dbg.", 9)) 362 ST.remove(TI++); 363 else 364 ++TI; 365 } 366 367 return true; 368} 369 370bool StripSymbols::runOnModule(Module &M) { 371 bool Changed = false; 372 Changed |= StripDebugInfo(M); 373 if (!OnlyDebugInfo) 374 Changed |= StripSymbolNames(M, false); 375 return Changed; 376} 377 378bool StripNonDebugSymbols::runOnModule(Module &M) { 379 return StripSymbolNames(M, true); 380} 381 382bool StripDebugDeclare::runOnModule(Module &M) { 383 384 Function *Declare = M.getFunction("llvm.dbg.declare"); 385 std::vector<Constant*> DeadConstants; 386 387 if (Declare) { 388 while (!Declare->use_empty()) { 389 CallInst *CI = cast<CallInst>(Declare->use_back()); 390 Value *Arg1 = CI->getOperand(1); 391 Value *Arg2 = CI->getOperand(2); 392 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result"); 393 CI->eraseFromParent(); 394 if (Arg1->use_empty()) { 395 if (Constant *C = dyn_cast<Constant>(Arg1)) 396 DeadConstants.push_back(C); 397 else 398 RecursivelyDeleteTriviallyDeadInstructions(Arg1); 399 } 400 if (Arg2->use_empty()) 401 if (Constant *C = dyn_cast<Constant>(Arg2)) 402 DeadConstants.push_back(C); 403 } 404 Declare->eraseFromParent(); 405 } 406 407 // Delete all llvm.dbg.global_variables. 408 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 409 I != E; ++I) { 410 GlobalVariable *GV = dyn_cast<GlobalVariable>(I); 411 if (!GV) continue; 412 if (GV->use_empty() && GV->getName().startswith("llvm.dbg.global_variable")) 413 DeadConstants.push_back(GV); 414 } 415 416 while (!DeadConstants.empty()) { 417 Constant *C = DeadConstants.back(); 418 DeadConstants.pop_back(); 419 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 420 if (GV->hasLocalLinkage()) 421 RemoveDeadConstant(GV); 422 } 423 else 424 RemoveDeadConstant(C); 425 } 426 427 return true; 428} 429