forked from OSchip/llvm-project
305 lines
10 KiB
C++
305 lines
10 KiB
C++
//===- StripSymbols.cpp - Strip symbols and debug info from a module ------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// The StripSymbols transformation implements code stripping. Specifically, it
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// can delete:
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//
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// * names for virtual registers
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// * symbols for internal globals and functions
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// * debug information
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//
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// Note that this transformation makes code much less readable, so it should
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// only be used in situations where the 'strip' utility would be used, such as
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// reducing code size or making it harder to reverse engineer code.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/ValueSymbolTable.h"
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#include "llvm/TypeSymbolTable.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/ADT/SmallPtrSet.h"
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using namespace llvm;
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namespace {
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class VISIBILITY_HIDDEN StripSymbols : public ModulePass {
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bool OnlyDebugInfo;
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public:
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static char ID; // Pass identification, replacement for typeid
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explicit StripSymbols(bool ODI = false)
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: ModulePass(&ID), OnlyDebugInfo(ODI) {}
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/// StripSymbolNames - Strip symbol names.
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bool StripSymbolNames(Module &M);
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// StripDebugInfo - Strip debug info in the module if it exists.
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// To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and
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// llvm.dbg.region.end calls, and any globals they point to if now dead.
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bool StripDebugInfo(Module &M);
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virtual bool runOnModule(Module &M);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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}
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};
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}
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char StripSymbols::ID = 0;
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static RegisterPass<StripSymbols>
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X("strip", "Strip all symbols from a module");
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ModulePass *llvm::createStripSymbolsPass(bool OnlyDebugInfo) {
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return new StripSymbols(OnlyDebugInfo);
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}
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/// OnlyUsedBy - Return true if V is only used by Usr.
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static bool OnlyUsedBy(Value *V, Value *Usr) {
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for(Value::use_iterator I = V->use_begin(), E = V->use_end(); I != E; ++I) {
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User *U = *I;
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if (U != Usr)
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return false;
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}
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return true;
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}
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static void RemoveDeadConstant(Constant *C) {
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assert(C->use_empty() && "Constant is not dead!");
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SmallPtrSet<Constant *, 4> Operands;
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for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i)
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if (isa<DerivedType>(C->getOperand(i)->getType()) &&
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OnlyUsedBy(C->getOperand(i), C))
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Operands.insert(C->getOperand(i));
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
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if (!GV->hasInternalLinkage()) return; // Don't delete non static globals.
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GV->eraseFromParent();
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}
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else if (!isa<Function>(C))
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C->destroyConstant();
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// If the constant referenced anything, see if we can delete it as well.
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for (SmallPtrSet<Constant *, 4>::iterator OI = Operands.begin(),
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OE = Operands.end(); OI != OE; ++OI)
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RemoveDeadConstant(*OI);
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}
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// Strip the symbol table of its names.
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//
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static void StripSymtab(ValueSymbolTable &ST) {
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for (ValueSymbolTable::iterator VI = ST.begin(), VE = ST.end(); VI != VE; ) {
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Value *V = VI->getValue();
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++VI;
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if (!isa<GlobalValue>(V) || cast<GlobalValue>(V)->hasInternalLinkage()) {
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// Set name to "", removing from symbol table!
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V->setName("");
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}
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}
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}
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bool StripSymbols::runOnModule(Module &M) {
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bool Changed = false;
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Changed |= StripDebugInfo(M);
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Changed |= StripSymbolNames(M);
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return Changed;
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}
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// Strip the symbol table of its names.
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static void StripTypeSymtab(TypeSymbolTable &ST) {
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for (TypeSymbolTable::iterator TI = ST.begin(), E = ST.end(); TI != E; )
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ST.remove(TI++);
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}
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/// Find values that are marked as llvm.used.
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void findUsedValues(Module &M,
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SmallPtrSet<const GlobalValue*, 8>& llvmUsedValues) {
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if (GlobalVariable *LLVMUsed = M.getGlobalVariable("llvm.used")) {
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llvmUsedValues.insert(LLVMUsed);
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// Collect values that are preserved as per explicit request.
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// llvm.used is used to list these values.
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if (ConstantArray *Inits =
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dyn_cast<ConstantArray>(LLVMUsed->getInitializer())) {
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for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i) {
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if (GlobalValue *GV = dyn_cast<GlobalValue>(Inits->getOperand(i)))
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llvmUsedValues.insert(GV);
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else if (ConstantExpr *CE =
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dyn_cast<ConstantExpr>(Inits->getOperand(i)))
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if (CE->getOpcode() == Instruction::BitCast)
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if (GlobalValue *GV = dyn_cast<GlobalValue>(CE->getOperand(0)))
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llvmUsedValues.insert(GV);
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}
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}
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}
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}
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/// StripSymbolNames - Strip symbol names.
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bool StripSymbols::StripSymbolNames(Module &M) {
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if (OnlyDebugInfo)
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return false;
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SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
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findUsedValues(M, llvmUsedValues);
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for (Module::global_iterator I = M.global_begin(), E = M.global_end();
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I != E; ++I) {
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if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
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I->setName(""); // Internal symbols can't participate in linkage
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}
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for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
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if (I->hasInternalLinkage() && llvmUsedValues.count(I) == 0)
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I->setName(""); // Internal symbols can't participate in linkage
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StripSymtab(I->getValueSymbolTable());
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}
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// Remove all names from types.
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StripTypeSymtab(M.getTypeSymbolTable());
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return true;
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}
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// StripDebugInfo - Strip debug info in the module if it exists.
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// To do this, we remove llvm.dbg.func.start, llvm.dbg.stoppoint, and
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// llvm.dbg.region.end calls, and any globals they point to if now dead.
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bool StripSymbols::StripDebugInfo(Module &M) {
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Function *FuncStart = M.getFunction("llvm.dbg.func.start");
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Function *StopPoint = M.getFunction("llvm.dbg.stoppoint");
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Function *RegionStart = M.getFunction("llvm.dbg.region.start");
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Function *RegionEnd = M.getFunction("llvm.dbg.region.end");
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Function *Declare = M.getFunction("llvm.dbg.declare");
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std::vector<Constant*> DeadConstants;
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// Remove all of the calls to the debugger intrinsics, and remove them from
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// the module.
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if (FuncStart) {
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while (!FuncStart->use_empty()) {
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CallInst *CI = cast<CallInst>(FuncStart->use_back());
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Value *Arg = CI->getOperand(1);
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assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
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CI->eraseFromParent();
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if (Arg->use_empty())
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if (Constant *C = dyn_cast<Constant>(Arg))
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DeadConstants.push_back(C);
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}
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FuncStart->eraseFromParent();
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}
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if (StopPoint) {
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while (!StopPoint->use_empty()) {
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CallInst *CI = cast<CallInst>(StopPoint->use_back());
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Value *Arg = CI->getOperand(3);
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assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
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CI->eraseFromParent();
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if (Arg->use_empty())
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if (Constant *C = dyn_cast<Constant>(Arg))
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DeadConstants.push_back(C);
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}
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StopPoint->eraseFromParent();
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}
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if (RegionStart) {
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while (!RegionStart->use_empty()) {
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CallInst *CI = cast<CallInst>(RegionStart->use_back());
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Value *Arg = CI->getOperand(1);
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assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
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CI->eraseFromParent();
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if (Arg->use_empty())
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if (Constant *C = dyn_cast<Constant>(Arg))
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DeadConstants.push_back(C);
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}
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RegionStart->eraseFromParent();
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}
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if (RegionEnd) {
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while (!RegionEnd->use_empty()) {
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CallInst *CI = cast<CallInst>(RegionEnd->use_back());
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Value *Arg = CI->getOperand(1);
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assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
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CI->eraseFromParent();
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if (Arg->use_empty())
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if (Constant *C = dyn_cast<Constant>(Arg))
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DeadConstants.push_back(C);
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}
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RegionEnd->eraseFromParent();
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}
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if (Declare) {
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while (!Declare->use_empty()) {
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CallInst *CI = cast<CallInst>(Declare->use_back());
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Value *Arg = CI->getOperand(2);
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assert(CI->use_empty() && "llvm.dbg intrinsic should have void result");
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CI->eraseFromParent();
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if (Arg->use_empty())
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if (Constant *C = dyn_cast<GlobalVariable>(Arg))
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DeadConstants.push_back(C);
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}
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Declare->eraseFromParent();
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}
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SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
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findUsedValues(M, llvmUsedValues);
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// llvm.dbg.compile_units and llvm.dbg.subprograms are marked as linkonce
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// but since we are removing all debug information, make them internal now.
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if (Constant *C = M.getNamedGlobal("llvm.dbg.compile_units"))
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
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GV->setLinkage(GlobalValue::InternalLinkage);
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if (Constant *C = M.getNamedGlobal("llvm.dbg.subprograms"))
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
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GV->setLinkage(GlobalValue::InternalLinkage);
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if (Constant *C = M.getNamedGlobal("llvm.dbg.global_variables"))
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
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GV->setLinkage(GlobalValue::InternalLinkage);
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// Delete all dbg variables.
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const Type *DbgVTy = M.getTypeByName("llvm.dbg.variable.type");
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const Type *DbgGVTy = M.getTypeByName("llvm.dbg.global_variable.type");
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if (DbgVTy || DbgGVTy)
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for (Module::global_iterator I = M.global_begin(), E = M.global_end();
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I != E; ++I) {
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GlobalVariable *GV = dyn_cast<GlobalVariable>(I);
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if (!GV) continue;
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if (GV->use_empty() && llvmUsedValues.count(I) == 0
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&& (!GV->hasSection()
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|| strcmp(GV->getSection().c_str(), "llvm.metadata") == 0))
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DeadConstants.push_back(GV);
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}
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if (DeadConstants.empty())
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return false;
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// Delete any internal globals that were only used by the debugger intrinsics.
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while (!DeadConstants.empty()) {
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Constant *C = DeadConstants.back();
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DeadConstants.pop_back();
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
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if (GV->hasInternalLinkage())
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RemoveDeadConstant(GV);
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}
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else
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RemoveDeadConstant(C);
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}
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// Remove all llvm.dbg types.
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TypeSymbolTable &ST = M.getTypeSymbolTable();
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for (TypeSymbolTable::iterator TI = ST.begin(), TE = ST.end(); TI != TE; ) {
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if (!strncmp(TI->first.c_str(), "llvm.dbg.", 9))
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ST.remove(TI++);
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else
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++TI;
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}
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return true;
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}
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