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/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/ADT/SmallPtrSet.h"
38 class StripSymbols : public ModulePass {
41 static char ID; // Pass identification, replacement for typeid
42 explicit StripSymbols(bool ODI = false)
43 : ModulePass(&ID), OnlyDebugInfo(ODI) {}
45 virtual bool runOnModule(Module &M);
47 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
52 class StripNonDebugSymbols : public ModulePass {
54 static char ID; // Pass identification, replacement for typeid
55 explicit StripNonDebugSymbols()
58 virtual bool runOnModule(Module &M);
60 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
65 class StripDebugDeclare : public ModulePass {
67 static char ID; // Pass identification, replacement for typeid
68 explicit StripDebugDeclare()
71 virtual bool runOnModule(Module &M);
73 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
79 char StripSymbols::ID = 0;
80 static RegisterPass<StripSymbols>
81 X("strip", "Strip all symbols from a module");
83 ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) {
84 return new StripSymbols(OnlyDebugInfo);
87 char StripNonDebugSymbols::ID = 0;
88 static RegisterPass<StripNonDebugSymbols>
89 Y("strip-nondebug", "Strip all symbols, except dbg symbols, from a module");
91 ModulePass *llvm::createStripNonDebugSymbolsPass() {
92 return new StripNonDebugSymbols();
95 char StripDebugDeclare::ID = 0;
96 static RegisterPass<StripDebugDeclare>
97 Z("strip-debug-declare", "Strip all llvm.dbg.declare intrinsics");
99 ModulePass *llvm::createStripDebugDeclarePass() {
100 return new StripDebugDeclare();
103 /// OnlyUsedBy - Return true if V is only used by Usr.
104 static bool OnlyUsedBy(Value *V, Value *Usr) {
105 for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
113 static void RemoveDeadConstant(Constant *C) {
114 assert(C->use_empty() && "Constant is not dead!");
115 SmallPtrSet<Constant *, 4> Operands;
116 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
117 if (isa<DerivedType>(C->getOperand(i)->getType()) &&
118 OnlyUsedBy(C->getOperand(i), C))
119 Operands.insert(C->getOperand(i));
120 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
121 if (!GV->hasLocalLinkage()) return; // Don't delete non static globals.
122 GV->eraseFromParent();
124 else if (!isa<Function>(C))
125 if (isa<CompositeType>(C->getType()))
126 C->destroyConstant();
128 // If the constant referenced anything, see if we can delete it as well.
129 for (SmallPtrSet<Constant *, 4>::iterator OI = Operands.begin(),
130 OE = Operands.end(); OI != OE; ++OI)
131 RemoveDeadConstant(*OI);
134 // Strip the symbol table of its names.
136 static void StripSymtab(ValueSymbolTable &ST, bool PreserveDbgInfo) {
137 for (ValueSymbolTable::iterator VI = ST.begin(), VE = ST.end(); VI != VE; ) {
138 Value *V = VI->getValue();
140 if (!isa<GlobalValue>(V) || cast<GlobalValue>(V)->hasLocalLinkage()) {
141 if (!PreserveDbgInfo || !V->getName().startswith("llvm.dbg"))
142 // Set name to "", removing from symbol table!
148 // Strip the symbol table of its names.
149 static void StripTypeSymtab(TypeSymbolTable &ST, bool PreserveDbgInfo) {
150 for (TypeSymbolTable::iterator TI = ST.begin(), E = ST.end(); TI != E; ) {
151 if (PreserveDbgInfo && strncmp(TI->first.c_str(), "llvm.dbg", 8) == 0)
158 /// Find values that are marked as llvm.used.
159 static void findUsedValues(GlobalVariable *LLVMUsed,
160 SmallPtrSet<const GlobalValue*, 8> &UsedValues) {
161 if (LLVMUsed == 0) return;
162 UsedValues.insert(LLVMUsed);
164 ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
165 if (Inits == 0) return;
167 for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
168 if (GlobalValue *GV =
169 dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
170 UsedValues.insert(GV);
173 /// StripSymbolNames - Strip symbol names.
174 static bool StripSymbolNames(Module &M, bool PreserveDbgInfo) {
176 SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
177 findUsedValues(M.getGlobalVariable("llvm.used"), llvmUsedValues);
178 findUsedValues(M.getGlobalVariable("llvm.compiler.used"), llvmUsedValues);
180 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
182 if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
183 if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
184 I->setName(""); // Internal symbols can't participate in linkage
187 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
188 if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
189 if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
190 I->setName(""); // Internal symbols can't participate in linkage
191 StripSymtab(I->getValueSymbolTable(), PreserveDbgInfo);
194 // Remove all names from types.
195 StripTypeSymtab(M.getTypeSymbolTable(), PreserveDbgInfo);
200 // StripDebugInfo - Strip debug info in the module if it exists.
201 // To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and
202 // llvm.dbg.region.end calls, and any globals they point to if now dead.
203 static bool StripDebugInfo(Module &M) {
205 // Remove all of the calls to the debugger intrinsics, and remove them from
207 Function *FuncStart = M.getFunction("llvm.dbg.func.start");
208 Function *StopPoint = M.getFunction("llvm.dbg.stoppoint");
209 Function *RegionStart = M.getFunction("llvm.dbg.region.start");
210 Function *RegionEnd = M.getFunction("llvm.dbg.region.end");
211 Function *Declare = M.getFunction("llvm.dbg.declare");
214 while (!FuncStart->use_empty()) {
215 CallInst *CI = cast<CallInst>(FuncStart->use_back());
216 CI->eraseFromParent();
218 FuncStart->eraseFromParent();
221 while (!StopPoint->use_empty()) {
222 CallInst *CI = cast<CallInst>(StopPoint->use_back());
223 CI->eraseFromParent();
225 StopPoint->eraseFromParent();
228 while (!RegionStart->use_empty()) {
229 CallInst *CI = cast<CallInst>(RegionStart->use_back());
230 CI->eraseFromParent();
232 RegionStart->eraseFromParent();
235 while (!RegionEnd->use_empty()) {
236 CallInst *CI = cast<CallInst>(RegionEnd->use_back());
237 CI->eraseFromParent();
239 RegionEnd->eraseFromParent();
242 while (!Declare->use_empty()) {
243 CallInst *CI = cast<CallInst>(Declare->use_back());
244 CI->eraseFromParent();
246 Declare->eraseFromParent();
249 NamedMDNode *NMD = M.getNamedMetadata("llvm.dbg.gv");
251 NMD->eraseFromParent();
253 // Remove dead metadata.
254 M.getContext().RemoveDeadMetadata();
258 bool StripSymbols::runOnModule(Module &M) {
259 bool Changed = false;
260 Changed |= StripDebugInfo(M);
262 Changed |= StripSymbolNames(M, false);
266 bool StripNonDebugSymbols::runOnModule(Module &M) {
267 return StripSymbolNames(M, true);
270 bool StripDebugDeclare::runOnModule(Module &M) {
272 Function *Declare = M.getFunction("llvm.dbg.declare");
273 std::vector<Constant*> DeadConstants;
276 while (!Declare->use_empty()) {
277 CallInst *CI = cast<CallInst>(Declare->use_back());
278 Value *Arg1 = CI->getOperand(1);
279 Value *Arg2 = CI->getOperand(2);
280 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
281 CI->eraseFromParent();
282 if (Arg1->use_empty()) {
283 if (Constant *C = dyn_cast<Constant>(Arg1))
284 DeadConstants.push_back(C);
286 RecursivelyDeleteTriviallyDeadInstructions(Arg1);
288 if (Arg2->use_empty())
289 if (Constant *C = dyn_cast<Constant>(Arg2))
290 DeadConstants.push_back(C);
292 Declare->eraseFromParent();
295 // Delete all llvm.dbg.global_variables.
296 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
298 GlobalVariable *GV = dyn_cast<GlobalVariable>(I);
300 if (GV->use_empty() && GV->getName().startswith("llvm.dbg.global_variable"))
301 DeadConstants.push_back(GV);
304 while (!DeadConstants.empty()) {
305 Constant *C = DeadConstants.back();
306 DeadConstants.pop_back();
307 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
308 if (GV->hasLocalLinkage())
309 RemoveDeadConstant(GV);
312 RemoveDeadConstant(C);