forked from OSchip/llvm-project
414 lines
13 KiB
C++
414 lines
13 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/Analysis/DebugInfo.h"
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#include "llvm/ValueSymbolTable.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/ADT/DenseMap.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 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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initializeStripSymbolsPass(*PassRegistry::getPassRegistry());
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}
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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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class StripNonDebugSymbols : public ModulePass {
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public:
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static char ID; // Pass identification, replacement for typeid
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explicit StripNonDebugSymbols()
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: ModulePass(ID) {
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initializeStripNonDebugSymbolsPass(*PassRegistry::getPassRegistry());
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}
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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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class StripDebugDeclare : public ModulePass {
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public:
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static char ID; // Pass identification, replacement for typeid
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explicit StripDebugDeclare()
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: ModulePass(ID) {
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initializeStripDebugDeclarePass(*PassRegistry::getPassRegistry());
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}
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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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class StripDeadDebugInfo : public ModulePass {
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public:
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static char ID; // Pass identification, replacement for typeid
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explicit StripDeadDebugInfo()
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: ModulePass(ID) {
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initializeStripDeadDebugInfoPass(*PassRegistry::getPassRegistry());
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}
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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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INITIALIZE_PASS(StripSymbols, "strip",
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"Strip all symbols from a module", false, false)
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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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char StripNonDebugSymbols::ID = 0;
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INITIALIZE_PASS(StripNonDebugSymbols, "strip-nondebug",
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"Strip all symbols, except dbg symbols, from a module",
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false, false)
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ModulePass *llvm::createStripNonDebugSymbolsPass() {
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return new StripNonDebugSymbols();
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}
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char StripDebugDeclare::ID = 0;
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INITIALIZE_PASS(StripDebugDeclare, "strip-debug-declare",
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"Strip all llvm.dbg.declare intrinsics", false, false)
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ModulePass *llvm::createStripDebugDeclarePass() {
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return new StripDebugDeclare();
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}
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char StripDeadDebugInfo::ID = 0;
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INITIALIZE_PASS(StripDeadDebugInfo, "strip-dead-debug-info",
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"Strip debug info for unused symbols", false, false)
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ModulePass *llvm::createStripDeadDebugInfoPass() {
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return new StripDeadDebugInfo();
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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 (OnlyUsedBy(C->getOperand(i), C))
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Operands.insert(cast<Constant>(C->getOperand(i)));
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) {
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if (!GV->hasLocalLinkage()) 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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if (isa<CompositeType>(C->getType()))
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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, bool PreserveDbgInfo) {
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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)->hasLocalLinkage()) {
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if (!PreserveDbgInfo || !V->getName().startswith("llvm.dbg"))
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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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// Strip any named types of their names.
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static void StripTypeNames(Module &M, bool PreserveDbgInfo) {
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std::vector<StructType*> StructTypes;
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M.findUsedStructTypes(StructTypes);
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for (unsigned i = 0, e = StructTypes.size(); i != e; ++i) {
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StructType *STy = StructTypes[i];
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if (STy->isAnonymous() || STy->getName().empty()) continue;
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if (PreserveDbgInfo && STy->getName().startswith("llvm.dbg"))
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continue;
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STy->setName("");
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}
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}
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/// Find values that are marked as llvm.used.
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static void findUsedValues(GlobalVariable *LLVMUsed,
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SmallPtrSet<const GlobalValue*, 8> &UsedValues) {
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if (LLVMUsed == 0) return;
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UsedValues.insert(LLVMUsed);
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ConstantArray *Inits = dyn_cast<ConstantArray>(LLVMUsed->getInitializer());
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if (Inits == 0) return;
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for (unsigned i = 0, e = Inits->getNumOperands(); i != e; ++i)
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if (GlobalValue *GV =
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dyn_cast<GlobalValue>(Inits->getOperand(i)->stripPointerCasts()))
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UsedValues.insert(GV);
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}
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/// StripSymbolNames - Strip symbol names.
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static bool StripSymbolNames(Module &M, bool PreserveDbgInfo) {
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SmallPtrSet<const GlobalValue*, 8> llvmUsedValues;
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findUsedValues(M.getGlobalVariable("llvm.used"), llvmUsedValues);
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findUsedValues(M.getGlobalVariable("llvm.compiler.used"), 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->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
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if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
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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->hasLocalLinkage() && llvmUsedValues.count(I) == 0)
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if (!PreserveDbgInfo || !I->getName().startswith("llvm.dbg"))
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I->setName(""); // Internal symbols can't participate in linkage
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StripSymtab(I->getValueSymbolTable(), PreserveDbgInfo);
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}
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// Remove all names from types.
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StripTypeNames(M, PreserveDbgInfo);
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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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static bool StripDebugInfo(Module &M) {
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bool Changed = false;
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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 (Function *Declare = M.getFunction("llvm.dbg.declare")) {
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while (!Declare->use_empty()) {
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CallInst *CI = cast<CallInst>(Declare->use_back());
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CI->eraseFromParent();
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}
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Declare->eraseFromParent();
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Changed = true;
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}
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if (Function *DbgVal = M.getFunction("llvm.dbg.value")) {
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while (!DbgVal->use_empty()) {
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CallInst *CI = cast<CallInst>(DbgVal->use_back());
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CI->eraseFromParent();
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}
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DbgVal->eraseFromParent();
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Changed = true;
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}
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for (Module::named_metadata_iterator NMI = M.named_metadata_begin(),
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NME = M.named_metadata_end(); NMI != NME;) {
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NamedMDNode *NMD = NMI;
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++NMI;
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if (NMD->getName().startswith("llvm.dbg.")) {
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NMD->eraseFromParent();
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Changed = true;
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}
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}
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for (Module::iterator MI = M.begin(), ME = M.end(); MI != ME; ++MI)
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for (Function::iterator FI = MI->begin(), FE = MI->end(); FI != FE;
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++FI)
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for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE;
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++BI) {
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if (!BI->getDebugLoc().isUnknown()) {
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Changed = true;
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BI->setDebugLoc(DebugLoc());
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}
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}
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return Changed;
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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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if (!OnlyDebugInfo)
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Changed |= StripSymbolNames(M, false);
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return Changed;
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}
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bool StripNonDebugSymbols::runOnModule(Module &M) {
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return StripSymbolNames(M, true);
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}
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bool StripDebugDeclare::runOnModule(Module &M) {
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Function *Declare = M.getFunction("llvm.dbg.declare");
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std::vector<Constant*> DeadConstants;
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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 *Arg1 = CI->getArgOperand(0);
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Value *Arg2 = CI->getArgOperand(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 (Arg1->use_empty()) {
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if (Constant *C = dyn_cast<Constant>(Arg1))
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DeadConstants.push_back(C);
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else
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RecursivelyDeleteTriviallyDeadInstructions(Arg1);
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}
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if (Arg2->use_empty())
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if (Constant *C = dyn_cast<Constant>(Arg2))
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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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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->hasLocalLinkage())
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RemoveDeadConstant(GV);
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} else
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RemoveDeadConstant(C);
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}
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return true;
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}
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/// getRealLinkageName - If special LLVM prefix that is used to inform the asm
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/// printer to not emit usual symbol prefix before the symbol name is used then
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/// return linkage name after skipping this special LLVM prefix.
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static StringRef getRealLinkageName(StringRef LinkageName) {
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char One = '\1';
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if (LinkageName.startswith(StringRef(&One, 1)))
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return LinkageName.substr(1);
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return LinkageName;
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}
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bool StripDeadDebugInfo::runOnModule(Module &M) {
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bool Changed = false;
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// Debugging infomration is encoded in llvm IR using metadata. This is designed
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// such a way that debug info for symbols preserved even if symbols are
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// optimized away by the optimizer. This special pass removes debug info for
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// such symbols.
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// llvm.dbg.gv keeps track of debug info for global variables.
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if (NamedMDNode *NMD = M.getNamedMetadata("llvm.dbg.gv")) {
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SmallVector<MDNode *, 8> MDs;
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for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
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if (DIGlobalVariable(NMD->getOperand(i)).Verify())
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MDs.push_back(NMD->getOperand(i));
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else
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Changed = true;
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NMD->eraseFromParent();
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NMD = NULL;
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for (SmallVector<MDNode *, 8>::iterator I = MDs.begin(),
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E = MDs.end(); I != E; ++I) {
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GlobalVariable *GV = DIGlobalVariable(*I).getGlobal();
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if (GV && M.getGlobalVariable(GV->getName(), true)) {
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if (!NMD)
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NMD = M.getOrInsertNamedMetadata("llvm.dbg.gv");
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NMD->addOperand(*I);
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}
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else
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Changed = true;
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}
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}
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// llvm.dbg.sp keeps track of debug info for subprograms.
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if (NamedMDNode *NMD = M.getNamedMetadata("llvm.dbg.sp")) {
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SmallVector<MDNode *, 8> MDs;
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for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i)
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if (DISubprogram(NMD->getOperand(i)).Verify())
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MDs.push_back(NMD->getOperand(i));
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else
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Changed = true;
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NMD->eraseFromParent();
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NMD = NULL;
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for (SmallVector<MDNode *, 8>::iterator I = MDs.begin(),
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E = MDs.end(); I != E; ++I) {
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bool FnIsLive = false;
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if (Function *F = DISubprogram(*I).getFunction())
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if (M.getFunction(F->getName()))
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FnIsLive = true;
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if (FnIsLive) {
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if (!NMD)
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NMD = M.getOrInsertNamedMetadata("llvm.dbg.sp");
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NMD->addOperand(*I);
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} else {
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// Remove llvm.dbg.lv.fnname named mdnode which may have been used
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// to hold debug info for dead function's local variables.
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StringRef FName = DISubprogram(*I).getLinkageName();
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if (FName.empty())
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FName = DISubprogram(*I).getName();
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if (NamedMDNode *LVNMD =
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M.getNamedMetadata(Twine("llvm.dbg.lv.",
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getRealLinkageName(FName))))
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LVNMD->eraseFromParent();
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}
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}
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}
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return Changed;
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}
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