//===- StripSymbols.cpp - Strip symbols and debug info from a module ------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// The StripSymbols transformation implements code stripping. Specifically, it
// can delete:
//
// * names for virtual registers
// * symbols for internal globals and functions
// * debug information
//
// Note that this transformation makes code much less readable, so it should
// only be used in situations where the 'strip' utility would be used, such as
// reducing code size or making it harder to reverse engineer code.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/ValueSymbolTable.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
using namespace llvm;
namespace {
class StripSymbols : public ModulePass {
bool OnlyDebugInfo;
public:
static char ID; // Pass identification, replacement for typeid
explicit StripSymbols(bool ODI = false)
: ModulePass(ID), OnlyDebugInfo(ODI) {
initializeStripSymbolsPass(*PassRegistry::getPassRegistry());
}
virtual bool runOnModule(Module &M);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
};
class StripNonDebugSymbols : public ModulePass {
public:
static char ID; // Pass identification, replacement for typeid
explicit StripNonDebugSymbols()
: ModulePass(ID) {
initializeStripNonDebugSymbolsPass(*PassRegistry::getPassRegistry());
}
virtual bool runOnModule(Module &M);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
};
class StripDebugDeclare : public ModulePass {
public:
static char ID; // Pass identification, replacement for typeid
explicit StripDebugDeclare()
: ModulePass(ID) {
initializeStripDebugDeclarePass(*PassRegistry::getPassRegistry());
}
virtual bool runOnModule(Module &M);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
};
class StripDeadDebugInfo : public ModulePass {
public:
static char ID; // Pass identification, replacement for typeid
explicit StripDeadDebugInfo()
: ModulePass(ID) {
initializeStripDeadDebugInfoPass(*PassRegistry::getPassRegistry());
}
virtual bool runOnModule(Module &M);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
}
};
}
char StripSymbols::ID = 0;
INITIALIZE_PASS(StripSymbols, "strip",
"Strip all symbols from a module", false, false)
ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) {
return new StripSymbols(OnlyDebugInfo);
}
char StripNonDebugSymbols::ID = 0;
INITIALIZE_PASS(StripNonDebugSymbols, "strip-nondebug",
"Strip all symbols, except dbg symbols, from a module",
false, false)
ModulePass *llvm::createStripNonDebugSymbolsPass() {
return new StripNonDebugSymbols();
}
char StripDebugDeclare::ID = 0;
INITIALIZE_PASS(StripDebugDeclare, "strip-debug-declare",
"Strip all llvm.dbg.declare intrinsics", false, false)
ModulePass *llvm::createStripDebugDeclarePass() {
return new StripDebugDeclare();
}
char StripDeadDebugInfo::ID = 0;
INITIALIZE_PASS(StripDeadDebugInfo, "strip-dead-debug-info",
"Strip debug info for unused symbols", false, false)
ModulePass *llvm::createStripDeadDebugInfoPass() {
return new StripDeadDebugInfo();
}
/// OnlyUsedBy - Return true if V is only used by Usr.
static bool OnlyUsedBy(Value *V, Value *Usr) {
for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
User *U = *I;
if (U != Usr)
return false;
}
return true;
}
static void RemoveDeadConstant(Constant *C) {
assert(C->use_empty() && "Constant is not dead!");
SmallPtrSet<Constant*, 4> Operands;
for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
if (OnlyUsedBy(C->getOperand(i), C))
Operands.insert(cast<Constant>(C->getOperand(i)));
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
if (!GV->hasLocalLinkage()) return; // Don't delete non static globals.
GV->eraseFromParent();
}
else if (!isa<Function>(C))
if (isa<CompositeType>(C->getType()))
C->destroyConstant();
// If the constant referenced anything, see if we can delete it as well.
for (SmallPtrSet<Constant*, 4>::iterator OI = Operands.begin(),
OE = Operands.end(); OI != OE; ++OI)
RemoveDeadConstant(*OI);
}
// Strip the symbol table of its names.
//
static void StripSymtab(ValueSymbolTable &ST, bool PreserveDbgInfo) {
for (ValueSymbolTable::iterator VI = ST.begin(), VE = ST.end(); VI != VE; ) {
Value *V = VI->getValue();
++VI;
if (!isa<GlobalValue>(V) || cast<GlobalValue>(V)->hasLocalLinkage()) {
if (!PreserveDbgInfo || !V->getName().startswith("llvm.dbg"))
// Set name to "", removing from symbol table!
V->setName("");
}
}
}
// Strip any named types of their names.
static void StripTypeNames(Module &M, bool PreserveDbgInfo) {
std::vector<StructType*> StructTypes;
M.findUsedStructTypes(StructTypes);
for (unsigned i = 0, e = StructTypes.size(); i != e; ++i) {
StructType *STy = StructTypes[i];
if (STy->isAnonymous() || STy->getName().empty()) continue;
if (PreserveDbgInfo && STy->getName().startswith("llvm.dbg"))
continue;
STy->setName("");
}
}
/// Find values that are marked as llvm.used.
static void findUsedValues(GlobalVariable *LLVMUsed,
SmallPtrSet<const GlobalValue*, 8> &UsedValues) {
if (LLVMUsed == 0) return;
UsedValues.insert(LLVMUsed);
ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
if (Inits == 0) return;
for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
if (GlobalValue *GV =
dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
UsedValues.insert(GV);
}
/// StripSymbolNames - Strip symbol names.
static bool StripSymbolNames(Module &M, bool PreserveDbgInfo) {
SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
findUsedValues(M.getGlobalVariable("llvm.used"), llvmUsedValues);
findUsedValues(M.getGlobalVariable("llvm.compiler.used"), llvmUsedValues);
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
I != E; ++I) {
if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
I->setName(""); // Internal symbols can't participate in linkage
}
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
if (I->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
I->setName(""); // Internal symbols can't participate in linkage
StripSymtab(I->getValueSymbolTable(), PreserveDbgInfo);
}
// Remove all names from types.
StripTypeNames(M, PreserveDbgInfo);
return true;
}
// StripDebugInfo - Strip debug info in the module if it exists.
// To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and
// llvm.dbg.region.end calls, and any globals they point to if now dead.
static bool StripDebugInfo(Module &M) {
bool Changed = false;
// Remove all of the calls to the debugger intrinsics, and remove them from
// the module.
if (Function *Declare = M.getFunction("llvm.dbg.declare")) {
while (!Declare->use_empty()) {
CallInst *CI = cast<CallInst>(Declare->use_back());
CI->eraseFromParent();
}
Declare->eraseFromParent();
Changed = true;
}
if (Function *DbgVal = M.getFunction("llvm.dbg.value")) {
while (!DbgVal->use_empty()) {
CallInst *CI = cast<CallInst>(DbgVal->use_back());
CI->eraseFromParent();
}
DbgVal->eraseFromParent();
Changed = true;
}
for (Module::named_metadata_iterator NMI = M.named_metadata_begin(),
NME = M.named_metadata_end(); NMI != NME;) {
NamedMDNode *NMD = NMI;
++NMI;
if (NMD->getName().startswith("llvm.dbg.")) {
NMD->eraseFromParent();
Changed = true;
}
}
for (Module::iterator MI = M.begin(), ME = M.end(); MI != ME; ++MI)
for (Function::iterator FI = MI->begin(), FE = MI->end(); FI != FE;
++FI)
for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE;
++BI) {
if (!BI->getDebugLoc().isUnknown()) {
Changed = true;
BI->setDebugLoc(DebugLoc());
}
}
return Changed;
}
bool StripSymbols::runOnModule(Module &M) {
bool Changed = false;
Changed |= StripDebugInfo(M);
if (!OnlyDebugInfo)
Changed |= StripSymbolNames(M, false);
return Changed;
}
bool StripNonDebugSymbols::runOnModule(Module &M) {
return StripSymbolNames(M, true);
}
bool StripDebugDeclare::runOnModule(Module &M) {
Function *Declare = M.getFunction("llvm.dbg.declare");
std::vector<Constant*> DeadConstants;
if (Declare) {
while (!Declare->use_empty()) {
CallInst *CI = cast<CallInst>(Declare->use_back());
Value *Arg1 = CI->getArgOperand(0);
Value *Arg2 = CI->getArgOperand(1);
assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
CI->eraseFromParent();
if (Arg1->use_empty()) {
if (Constant *C = dyn_cast<Constant>(Arg1))
DeadConstants.push_back(C);
else
RecursivelyDeleteTriviallyDeadInstructions(Arg1);
}
if (Arg2->use_empty())
if (Constant *C = dyn_cast<Constant>(Arg2))
DeadConstants.push_back(C);
}
Declare->eraseFromParent();
}
while (!DeadConstants.empty()) {
Constant *C = DeadConstants.back();
DeadConstants.pop_back();
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
if (GV->hasLocalLinkage())
RemoveDeadConstant(GV);
} else
RemoveDeadConstant(C);
}
return true;
}
/// getRealLinkageName - If special LLVM prefix that is used to inform the asm
/// printer to not emit usual symbol prefix before the symbol name is used then
/// return linkage name after skipping this special LLVM prefix.
static StringRef getRealLinkageName(StringRef LinkageName) {
char One = '\1';
if (LinkageName.startswith(StringRef(&One, 1)))
return LinkageName.substr(1);
return LinkageName;
}
bool StripDeadDebugInfo::runOnModule(Module &M) {
bool Changed = false;
// Debugging infomration is encoded in llvm IR using metadata. This is designed
// such a way that debug info for symbols preserved even if symbols are
// optimized away by the optimizer. This special pass removes debug info for
// such symbols.
// llvm.dbg.gv keeps track of debug info for global variables.
if (NamedMDNode *NMD = M.getNamedMetadata("llvm.dbg.gv")) {
SmallVector<MDNode *, 8> MDs;
for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
if (DIGlobalVariable(NMD->getOperand(i)).Verify())
MDs.push_back(NMD->getOperand(i));
else
Changed = true;
NMD->eraseFromParent();
NMD = NULL;
for (SmallVector<MDNode *, 8>::iterator I = MDs.begin(),
E = MDs.end(); I != E; ++I) {
GlobalVariable *GV = DIGlobalVariable(*I).getGlobal();
if (GV && M.getGlobalVariable(GV->getName(), true)) {
if (!NMD)
NMD = M.getOrInsertNamedMetadata("llvm.dbg.gv");
NMD->addOperand(*I);
}
else
Changed = true;
}
}
// llvm.dbg.sp keeps track of debug info for subprograms.
if (NamedMDNode *NMD = M.getNamedMetadata("llvm.dbg.sp")) {
SmallVector<MDNode *, 8> MDs;
for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
if (DISubprogram(NMD->getOperand(i)).Verify())
MDs.push_back(NMD->getOperand(i));
else
Changed = true;
NMD->eraseFromParent();
NMD = NULL;
for (SmallVector<MDNode *, 8>::iterator I = MDs.begin(),
E = MDs.end(); I != E; ++I) {
bool FnIsLive = false;
if (Function *F = DISubprogram(*I).getFunction())
if (M.getFunction(F->getName()))
FnIsLive = true;
if (FnIsLive) {
if (!NMD)
NMD = M.getOrInsertNamedMetadata("llvm.dbg.sp");
NMD->addOperand(*I);
} else {
// Remove llvm.dbg.lv.fnname named mdnode which may have been used
// to hold debug info for dead function's local variables.
StringRef FName = DISubprogram(*I).getLinkageName();
if (FName.empty())
FName = DISubprogram(*I).getName();
if (NamedMDNode *LVNMD =
M.getNamedMetadata(Twine("llvm.dbg.lv.",
getRealLinkageName(FName))))
LVNMD->eraseFromParent();
}
}
}
return Changed;
}