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 /// StripSymbolNames - Strip symbol names.
44 bool StripSymbolNames(Module &M);
46 // StripDebugInfo - Strip debug info in the module if it exists.
47 // To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and
48 // llvm.dbg.region.end calls, and any globals they point to if now dead.
49 bool StripDebugInfo(Module &M);
51 virtual bool runOnModule(Module &M);
53 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
59 char StripSymbols::ID = 0;
60 static RegisterPass<StripSymbols>
61 X("strip", "Strip all symbols from a module");
63 ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) {
64 return new StripSymbols(OnlyDebugInfo);
67 /// OnlyUsedBy - Return true if V is only used by Usr.
68 static bool OnlyUsedBy(Value *V, Value *Usr) {
69 for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
77 static void RemoveDeadConstant(Constant *C) {
78 assert(C->use_empty() && "Constant is not dead!");
79 SmallPtrSet<Constant *, 4> Operands;
80 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
81 if (isa<DerivedType>(C->getOperand(i)->getType()) &&
82 OnlyUsedBy(C->getOperand(i), C))
83 Operands.insert(C->getOperand(i));
84 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
85 if (!GV->hasInternalLinkage()) return; // Don't delete non static globals.
86 GV->eraseFromParent();
88 else if (!isa<Function>(C))
91 // If the constant referenced anything, see if we can delete it as well.
92 for (SmallPtrSet<Constant *, 4>::iterator OI = Operands.begin(),
93 OE = Operands.end(); OI != OE; ++OI)
94 RemoveDeadConstant(*OI);
97 // Strip the symbol table of its names.
99 static void StripSymtab(ValueSymbolTable &ST) {
100 for (ValueSymbolTable::iterator VI = ST.begin(), VE = ST.end(); VI != VE; ) {
101 Value *V = VI->getValue();
103 if (!isa<GlobalValue>(V) || cast<GlobalValue>(V)->hasInternalLinkage()) {
104 // Set name to "", removing from symbol table!
110 bool StripSymbols::runOnModule(Module &M) {
111 bool Changed = false;
112 Changed |= StripDebugInfo(M);
113 Changed |= StripSymbolNames(M);
117 // Strip the symbol table of its names.
118 static void StripTypeSymtab(TypeSymbolTable &ST) {
119 for (TypeSymbolTable::iterator TI = ST.begin(), E = ST.end(); TI != E; )
123 /// Find values that are marked as llvm.used.
124 void findUsedValues(Module &M,
125 SmallPtrSet<const GlobalValue*, 8>& llvmUsedValues) {
126 if (GlobalVariable *LLVMUsed = M.getGlobalVariable("llvm.used")) {
127 llvmUsedValues.insert(LLVMUsed);
128 // Collect values that are preserved as per explicit request.
129 // llvm.used is used to list these values.
130 if (ConstantArray *Inits =
131 dyn_cast<ConstantArray>(LLVMUsed->getInitializer())) {
132 for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i) {
133 if (GlobalValue *GV = dyn_cast<GlobalValue>(Inits->getOperand(i)))
134 llvmUsedValues.insert(GV);
135 else if (ConstantExpr *CE =
136 dyn_cast<ConstantExpr>(Inits->getOperand(i)))
137 if (CE->getOpcode() == Instruction::BitCast)
138 if (GlobalValue *GV = dyn_cast<GlobalValue>(CE->getOperand(0)))
139 llvmUsedValues.insert(GV);
145 /// StripSymbolNames - Strip symbol names.
146 bool StripSymbols::StripSymbolNames(Module &M) {
151 SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
152 findUsedValues(M, llvmUsedValues);
154 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
156 if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
157 I->setName(""); // Internal symbols can't participate in linkage
160 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
161 if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
162 I->setName(""); // Internal symbols can't participate in linkage
163 StripSymtab(I->getValueSymbolTable());
166 // Remove all names from types.
167 StripTypeSymtab(M.getTypeSymbolTable());
172 // StripDebugInfo - Strip debug info in the module if it exists.
173 // To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and
174 // llvm.dbg.region.end calls, and any globals they point to if now dead.
175 bool StripSymbols::StripDebugInfo(Module &M) {
177 Function *FuncStart = M.getFunction("llvm.dbg.func.start");
178 Function *StopPoint = M.getFunction("llvm.dbg.stoppoint");
179 Function *RegionStart = M.getFunction("llvm.dbg.region.start");
180 Function *RegionEnd = M.getFunction("llvm.dbg.region.end");
181 Function *Declare = M.getFunction("llvm.dbg.declare");
183 std::vector<Constant*> DeadConstants;
185 // Remove all of the calls to the debugger intrinsics, and remove them from
188 while (!FuncStart->use_empty()) {
189 CallInst *CI = cast<CallInst>(FuncStart->use_back());
190 Value *Arg = CI->getOperand(1);
191 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
192 CI->eraseFromParent();
193 if (Arg->use_empty())
194 if (Constant *C = dyn_cast<Constant>(Arg))
195 DeadConstants.push_back(C);
197 FuncStart->eraseFromParent();
200 while (!StopPoint->use_empty()) {
201 CallInst *CI = cast<CallInst>(StopPoint->use_back());
202 Value *Arg = CI->getOperand(3);
203 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
204 CI->eraseFromParent();
205 if (Arg->use_empty())
206 if (Constant *C = dyn_cast<Constant>(Arg))
207 DeadConstants.push_back(C);
209 StopPoint->eraseFromParent();
212 while (!RegionStart->use_empty()) {
213 CallInst *CI = cast<CallInst>(RegionStart->use_back());
214 Value *Arg = CI->getOperand(1);
215 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
216 CI->eraseFromParent();
217 if (Arg->use_empty())
218 if (Constant *C = dyn_cast<Constant>(Arg))
219 DeadConstants.push_back(C);
221 RegionStart->eraseFromParent();
224 while (!RegionEnd->use_empty()) {
225 CallInst *CI = cast<CallInst>(RegionEnd->use_back());
226 Value *Arg = CI->getOperand(1);
227 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
228 CI->eraseFromParent();
229 if (Arg->use_empty())
230 if (Constant *C = dyn_cast<Constant>(Arg))
231 DeadConstants.push_back(C);
233 RegionEnd->eraseFromParent();
236 while (!Declare->use_empty()) {
237 CallInst *CI = cast<CallInst>(Declare->use_back());
238 Value *Arg = CI->getOperand(2);
239 assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
240 CI->eraseFromParent();
241 if (Arg->use_empty())
242 if (Constant *C = dyn_cast<GlobalVariable>(Arg))
243 DeadConstants.push_back(C);
245 Declare->eraseFromParent();
248 SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
249 findUsedValues(M, llvmUsedValues);
251 // llvm.dbg.compile_units and llvm.dbg.subprograms are marked as linkonce
252 // but since we are removing all debug information, make them internal now.
253 if (Constant *C = M.getNamedGlobal("llvm.dbg.compile_units"))
254 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
255 GV->setLinkage(GlobalValue::InternalLinkage);
257 if (Constant *C = M.getNamedGlobal("llvm.dbg.subprograms"))
258 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
259 GV->setLinkage(GlobalValue::InternalLinkage);
261 if (Constant *C = M.getNamedGlobal("llvm.dbg.global_variables"))
262 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
263 GV->setLinkage(GlobalValue::InternalLinkage);
265 // Delete all dbg variables.
266 const Type *DbgVTy = M.getTypeByName("llvm.dbg.variable.type");
267 const Type *DbgGVTy = M.getTypeByName("llvm.dbg.global_variable.type");
268 if (DbgVTy || DbgGVTy)
269 for (Module::global_iterator I = M.global_begin(), E = M.global_end();
271 GlobalVariable *GV = dyn_cast<GlobalVariable>(I);
273 if (GV->use_empty() && llvmUsedValues.count(I) == 0
274 && (!GV->hasSection()
275 || strcmp(GV->getSection().c_str(), "llvm.metadata") == 0))
276 DeadConstants.push_back(GV);
279 if (DeadConstants.empty())
282 // Delete any internal globals that were only used by the debugger intrinsics.
283 while (!DeadConstants.empty()) {
284 Constant *C = DeadConstants.back();
285 DeadConstants.pop_back();
286 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
287 if (GV->hasInternalLinkage())
288 RemoveDeadConstant(GV);
291 RemoveDeadConstant(C);
294 // Remove all llvm.dbg types.
295 TypeSymbolTable &ST = M.getTypeSymbolTable();
296 for (TypeSymbolTable::iterator TI = ST.begin(), TE = ST.end(); TI != TE; ) {
297 if (!strncmp(TI->first.c_str(), "llvm.dbg.", 9))