1 //===- StripSymbols.cpp - Strip symbols and debug info from a module ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // The StripSymbols transformation implements code stripping. Specifically, it
13 // * names for virtual registers
14 // * symbols for internal globals and functions
15 // * debug information
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.
21 //===----------------------------------------------------------------------===//
23 #include "llvm/Transforms/IPO.h"
24 #include "llvm/Constants.h"
25 #include "llvm/DerivedTypes.h"
26 #include "llvm/Instructions.h"
27 #include "llvm/Module.h"
28 #include "llvm/Pass.h"
29 #include "llvm/ValueSymbolTable.h"
30 #include "llvm/TypeSymbolTable.h"
31 #include "llvm/Support/Compiler.h"
32 #include "llvm/ADT/SmallPtrSet.h"
36 class VISIBILITY_HIDDEN StripSymbols : public ModulePass {
39 static char ID; // Pass identification, replacement for typeid
40 explicit StripSymbols(bool ODI = false)
41 : ModulePass(&ID), OnlyDebugInfo(ODI) {}
43 virtual bool runOnModule(Module &M);
45 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
50 class VISIBILITY_HIDDEN StripNonDebugSymbols : public ModulePass {
52 static char ID; // Pass identification, replacement for typeid
53 explicit StripNonDebugSymbols()
56 virtual bool runOnModule(Module &M);
58 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
64 char StripSymbols::ID = 0;
65 static RegisterPass<StripSymbols>
66 X("strip", "Strip all symbols from a module");
68 ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) {
69 return new StripSymbols(OnlyDebugInfo);
72 char StripNonDebugSymbols::ID = 0;
73 static RegisterPass<StripNonDebugSymbols>
74 Y("strip-nondebug", "Strip all symbols, except dbg symbols, from a module");
76 ModulePass *llvm::createStripNonDebugSymbolsPass() {
77 return new StripNonDebugSymbols();
80 /// OnlyUsedBy - Return true if V is only used by Usr.
81 static bool OnlyUsedBy(Value *V, Value *Usr) {
82 for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
90 static void RemoveDeadConstant(Constant *C) {
91 assert(C->use_empty() && "Constant is not dead!");
92 SmallPtrSet<Constant *, 4> Operands;
93 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
94 if (isa<DerivedType>(C->getOperand(i)->getType()) &&
95 OnlyUsedBy(C->getOperand(i), C))
96 Operands.insert(C->getOperand(i));
97 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
98 if (!GV->hasInternalLinkage()) return; // Don't delete non static globals.
99 GV->eraseFromParent();
101 else if (!isa<Function>(C))
102 C->destroyConstant();
104 // If the constant referenced anything, see if we can delete it as well.
105 for (SmallPtrSet<Constant *, 4>::iterator OI = Operands.begin(),
106 OE = Operands.end(); OI != OE; ++OI)
107 RemoveDeadConstant(*OI);
110 // Strip the symbol table of its names.
112 static void StripSymtab(ValueSymbolTable &ST, bool PreserveDbgInfo) {
113 for (ValueSymbolTable::iterator VI = ST.begin(), VE = ST.end(); VI != VE; ) {
114 Value *V = VI->getValue();
116 if (!isa<GlobalValue>(V) || cast<GlobalValue>(V)->hasInternalLinkage()) {
117 if (!PreserveDbgInfo || strncmp(V->getNameStart(), "llvm.dbg", 8))
118 // Set name to "", removing from symbol table!
124 // Strip the symbol table of its names.
125 static void StripTypeSymtab(TypeSymbolTable &ST, bool PreserveDbgInfo) {
126 for (TypeSymbolTable::iterator TI = ST.begin(), E = ST.end(); TI != E; ) {
127 if (PreserveDbgInfo && strncmp(TI->first.c_str(), "llvm.dbg", 8) == 0)
134 /// Find values that are marked as llvm.used.
135 void findUsedValues(Module &M,
136 SmallPtrSet<const GlobalValue*, 8>& llvmUsedValues) {
137 if (GlobalVariable *LLVMUsed = M.getGlobalVariable("llvm.used")) {
138 llvmUsedValues.insert(LLVMUsed);
139 // Collect values that are preserved as per explicit request.
140 // llvm.used is used to list these values.
141 if (ConstantArray *Inits =
142 dyn_cast<ConstantArray>(LLVMUsed->getInitializer())) {
143 for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i) {
144 if (GlobalValue *GV = dyn_cast<GlobalValue>(Inits->getOperand(i)))
145 llvmUsedValues.insert(GV);
146 else if (ConstantExpr *CE =
147 dyn_cast<ConstantExpr>(Inits->getOperand(i)))
148 if (CE->getOpcode() == Instruction::BitCast)
149 if (GlobalValue *GV = dyn_cast<GlobalValue>(CE->getOperand(0)))
150 llvmUsedValues.insert(GV);
156 /// StripSymbolNames - Strip symbol names.
157 bool StripSymbolNames(Module &M, bool PreserveDbgInfo) {
159 SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
160 findUsedValues(M, llvmUsedValues);
162 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
164 if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
165 if (!PreserveDbgInfo || strncmp(I->getNameStart(), "llvm.dbg", 8))
166 I->setName(""); // Internal symbols can't participate in linkage
169 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
170 if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
171 if (!PreserveDbgInfo || strncmp(I->getNameStart(), "llvm.dbg", 8))
172 I->setName(""); // Internal symbols can't participate in linkage
173 StripSymtab(I->getValueSymbolTable(), PreserveDbgInfo);
176 // Remove all names from types.
177 StripTypeSymtab(M.getTypeSymbolTable(), PreserveDbgInfo);
182 // StripDebugInfo - Strip debug info in the module if it exists.
183 // To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and
184 // llvm.dbg.region.end calls, and any globals they point to if now dead.
185 bool StripDebugInfo(Module &M) {
187 Function *FuncStart = M.getFunction("llvm.dbg.func.start");
188 Function *StopPoint = M.getFunction("llvm.dbg.stoppoint");
189 Function *RegionStart = M.getFunction("llvm.dbg.region.start");
190 Function *RegionEnd = M.getFunction("llvm.dbg.region.end");
191 Function *Declare = M.getFunction("llvm.dbg.declare");
193 std::vector<Constant*> DeadConstants;
195 // Remove all of the calls to the debugger intrinsics, and remove them from
198 while (!FuncStart->use_empty()) {
199 CallInst *CI = cast<CallInst>(FuncStart->use_back());
200 Value *Arg = CI->getOperand(1);
201 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
202 CI->eraseFromParent();
203 if (Arg->use_empty())
204 if (Constant *C = dyn_cast<Constant>(Arg))
205 DeadConstants.push_back(C);
207 FuncStart->eraseFromParent();
210 while (!StopPoint->use_empty()) {
211 CallInst *CI = cast<CallInst>(StopPoint->use_back());
212 Value *Arg = CI->getOperand(3);
213 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
214 CI->eraseFromParent();
215 if (Arg->use_empty())
216 if (Constant *C = dyn_cast<Constant>(Arg))
217 DeadConstants.push_back(C);
219 StopPoint->eraseFromParent();
222 while (!RegionStart->use_empty()) {
223 CallInst *CI = cast<CallInst>(RegionStart->use_back());
224 Value *Arg = CI->getOperand(1);
225 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
226 CI->eraseFromParent();
227 if (Arg->use_empty())
228 if (Constant *C = dyn_cast<Constant>(Arg))
229 DeadConstants.push_back(C);
231 RegionStart->eraseFromParent();
234 while (!RegionEnd->use_empty()) {
235 CallInst *CI = cast<CallInst>(RegionEnd->use_back());
236 Value *Arg = CI->getOperand(1);
237 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
238 CI->eraseFromParent();
239 if (Arg->use_empty())
240 if (Constant *C = dyn_cast<Constant>(Arg))
241 DeadConstants.push_back(C);
243 RegionEnd->eraseFromParent();
246 while (!Declare->use_empty()) {
247 CallInst *CI = cast<CallInst>(Declare->use_back());
248 Value *Arg = CI->getOperand(2);
249 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
250 CI->eraseFromParent();
251 if (Arg->use_empty())
252 if (Constant *C = dyn_cast<Constant>(Arg))
253 DeadConstants.push_back(C);
255 Declare->eraseFromParent();
258 SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
259 findUsedValues(M, llvmUsedValues);
261 // llvm.dbg.compile_units and llvm.dbg.subprograms are marked as linkonce
262 // but since we are removing all debug information, make them internal now.
263 if (Constant *C = M.getNamedGlobal("llvm.dbg.compile_units"))
264 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
265 GV->setLinkage(GlobalValue::InternalLinkage);
267 if (Constant *C = M.getNamedGlobal("llvm.dbg.subprograms"))
268 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
269 GV->setLinkage(GlobalValue::InternalLinkage);
271 if (Constant *C = M.getNamedGlobal("llvm.dbg.global_variables"))
272 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
273 GV->setLinkage(GlobalValue::InternalLinkage);
275 // Delete all dbg variables.
276 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
278 GlobalVariable *GV = dyn_cast<GlobalVariable>(I);
280 if (GV->use_empty() && llvmUsedValues.count(I) == 0
281 && (!GV->hasSection()
282 || strcmp(GV->getSection().c_str(), "llvm.metadata") == 0))
283 DeadConstants.push_back(GV);
286 if (DeadConstants.empty())
289 // Delete any internal globals that were only used by the debugger intrinsics.
290 while (!DeadConstants.empty()) {
291 Constant *C = DeadConstants.back();
292 DeadConstants.pop_back();
293 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
294 if (GV->hasInternalLinkage())
295 RemoveDeadConstant(GV);
298 RemoveDeadConstant(C);
301 // Remove all llvm.dbg types.
302 TypeSymbolTable &ST = M.getTypeSymbolTable();
303 for (TypeSymbolTable::iterator TI = ST.begin(), TE = ST.end(); TI != TE; ) {
304 if (!strncmp(TI->first.c_str(), "llvm.dbg.", 9))
313 bool StripSymbols::runOnModule(Module &M) {
314 bool Changed = false;
315 Changed |= StripDebugInfo(M);
317 Changed |= StripSymbolNames(M, false);
321 bool StripNonDebugSymbols::runOnModule(Module &M) {
322 return StripSymbolNames(M, true);