C++ GlobalAlias::eraseFromParent方法代码示例

bool ResolveAliases::runOnModule(Module &M) {
  bool Modified = false;

  for (auto I = M.alias_begin(), E = M.alias_end(); I != E;) {
    GlobalAlias *Alias = &*I++;
    Alias->replaceAllUsesWith(Alias->getAliasee());
    Alias->eraseFromParent();
    Modified = true;
  }
  return Modified;
}

//
// Method: runOnModule()
//
// Description:
//  Entry point for this LLVM pass.
//  Replace all internal aliases with the
//  aliasee value
//
// Inputs:
//  M - A reference to the LLVM module to transform
//
// Outputs:
//  M - The transformed LLVM module.
//
// Return value:
//  true  - The module was modified.
//  false - The module was not modified.
//
bool FuncSimplify::runOnModule(Module& M) {

  std::vector<GlobalAlias*> toDelete;
  for (Module::alias_iterator I = M.alias_begin(); I != M.alias_end(); ++I) {
    if(!I->hasInternalLinkage())
      continue;
    I->replaceAllUsesWith(I->getAliasee());
    toDelete.push_back(I);
  }
  numChanged += toDelete.size();

  while(!toDelete.empty()) {
    GlobalAlias *I = toDelete.back();
    toDelete.pop_back();
    I->eraseFromParent();
  }


  return true;
}

static void convertAliasToDeclaration(GlobalAlias &GA, Module &M) {
  GlobalValue *GVal = GA.getBaseObject();
  GlobalValue *NewGV;
  if (auto *GVar = dyn_cast<GlobalVariable>(GVal)) {
    GlobalVariable *NewGVar = new GlobalVariable(
        M, GVar->getType()->getElementType(), GVar->isConstant(),
        GVar->getLinkage(), /*init*/ nullptr, GA.getName(), GVar,
        GVar->getThreadLocalMode(), GVar->getType()->getAddressSpace());
    NewGV = NewGVar;
    NewGV->copyAttributesFrom(GVar);
  } else {
    auto *F = dyn_cast<Function>(GVal);
    assert(F);
    Function *NewF = Function::Create(F->getFunctionType(), F->getLinkage(),
                                      GA.getName(), &M);
    NewGV = NewF;
    NewGV->copyAttributesFrom(F);
  }
  GA.replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, GA.getType()));
  GA.eraseFromParent();
}

// destructively move the contents of src into dest
// this assumes that the targets of the two modules are the same
// including the DataLayout and ModuleFlags (for example)
// and that there is no module-level assembly
static void jl_merge_module(Module *dest, std::unique_ptr<Module> src)
{
    assert(dest != src.get());
    for (Module::global_iterator I = src->global_begin(), E = src->global_end(); I != E;) {
        GlobalVariable *sG = &*I;
        GlobalValue *dG = dest->getNamedValue(sG->getName());
        ++I;
        // Replace a declaration with the definition:
        if (dG) {
            if (sG->isDeclaration()) {
                sG->replaceAllUsesWith(dG);
                sG->eraseFromParent();
                continue;
            }
            else {
                dG->replaceAllUsesWith(sG);
                dG->eraseFromParent();
            }
        }
        // Reparent the global variable:
        sG->removeFromParent();
        dest->getGlobalList().push_back(sG);
        // Comdat is owned by the Module, recreate it in the new parent:
        addComdat(sG);
    }

    for (Module::iterator I = src->begin(), E = src->end(); I != E;) {
        Function *sG = &*I;
        GlobalValue *dG = dest->getNamedValue(sG->getName());
        ++I;
        // Replace a declaration with the definition:
        if (dG) {
            if (sG->isDeclaration()) {
                sG->replaceAllUsesWith(dG);
                sG->eraseFromParent();
                continue;
            }
            else {
                dG->replaceAllUsesWith(sG);
                dG->eraseFromParent();
            }
        }
        // Reparent the global variable:
        sG->removeFromParent();
        dest->getFunctionList().push_back(sG);
        // Comdat is owned by the Module, recreate it in the new parent:
        addComdat(sG);
    }

    for (Module::alias_iterator I = src->alias_begin(), E = src->alias_end(); I != E;) {
        GlobalAlias *sG = &*I;
        GlobalValue *dG = dest->getNamedValue(sG->getName());
        ++I;
        if (dG) {
            if (!dG->isDeclaration()) { // aliases are always definitions, so this test is reversed from the above two
                sG->replaceAllUsesWith(dG);
                sG->eraseFromParent();
                continue;
            }
            else {
                dG->replaceAllUsesWith(sG);
                dG->eraseFromParent();
            }
        }
        sG->removeFromParent();
        dest->getAliasList().push_back(sG);
    }

    // metadata nodes need to be explicitly merged not just copied
    // so there are special passes here for each known type of metadata
    NamedMDNode *sNMD = src->getNamedMetadata("llvm.dbg.cu");
    if (sNMD) {
        NamedMDNode *dNMD = dest->getOrInsertNamedMetadata("llvm.dbg.cu");
#ifdef LLVM35
        for (NamedMDNode::op_iterator I = sNMD->op_begin(), E = sNMD->op_end(); I != E; ++I) {
            dNMD->addOperand(*I);
        }
#else
        for (unsigned i = 0, l = sNMD->getNumOperands(); i < l; i++) {
            dNMD->addOperand(sNMD->getOperand(i));
        }
#endif
    }
}

// emit_alias_to_llvm - Given decl and target emit alias to target.
void emit_alias_to_llvm(tree decl, tree target, tree target_decl) {
  if (errorcount || sorrycount) return;

  timevar_push(TV_LLVM_GLOBALS);

  // Get or create LLVM global for our alias.
  GlobalValue *V = cast<GlobalValue>(DECL_LLVM(decl));
  
  GlobalValue *Aliasee = NULL;
  
  if (target_decl)
    Aliasee = cast<GlobalValue>(DECL_LLVM(target_decl));
  else {
    // This is something insane. Probably only LTHUNKs can be here
    // Try to grab decl from IDENTIFIER_NODE

    // Query SymTab for aliasee
    const char* AliaseeName = IDENTIFIER_POINTER(target);
    Aliasee =
      dyn_cast_or_null<GlobalValue>(TheModule->
                                    getValueSymbolTable().lookup(AliaseeName));

    // Last resort. Query for name set via __asm__
    if (!Aliasee) {
      std::string starred = std::string("\001") + AliaseeName;
      Aliasee =
        dyn_cast_or_null<GlobalValue>(TheModule->
                                      getValueSymbolTable().lookup(starred));
    }
    
    if (!Aliasee) {
      error ("%J%qD aliased to undefined symbol %qE",
             decl, decl, target);
      timevar_pop(TV_LLVM_GLOBALS);
      return;
    }
  }
  
  GlobalValue::LinkageTypes Linkage;

  // Check for external weak linkage
  if (DECL_EXTERNAL(decl) && DECL_WEAK(decl))
    Linkage = GlobalValue::WeakLinkage;
  else if (!TREE_PUBLIC(decl))
    Linkage = GlobalValue::InternalLinkage;
  else
    Linkage = GlobalValue::ExternalLinkage;

  GlobalAlias* GA = new GlobalAlias(Aliasee->getType(), Linkage, "",
                                    Aliasee, TheModule);
  // Handle visibility style
  if (TREE_PUBLIC(decl)) {
    if (DECL_VISIBILITY(decl) == VISIBILITY_HIDDEN)
      GA->setVisibility(GlobalValue::HiddenVisibility);
    else if (DECL_VISIBILITY(decl) == VISIBILITY_PROTECTED)
      GA->setVisibility(GlobalValue::ProtectedVisibility);
  }

  if (V->getType() == GA->getType())
    V->replaceAllUsesWith(GA);
  else if (!V->use_empty()) {
    error ("%J Alias %qD used with invalid type!", decl, decl);
    timevar_pop(TV_LLVM_GLOBALS);
    return;
  }
    
  changeLLVMValue(V, GA);
  GA->takeName(V);
  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
    GV->eraseFromParent();
  else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
    GA->eraseFromParent();
  else if (Function *F = dyn_cast<Function>(V))
    F->eraseFromParent();
  else
    assert(0 && "Unsuported global value");

  TREE_ASM_WRITTEN(decl) = 1;
  
  timevar_pop(TV_LLVM_GLOBALS);
  return;
}