C++ GlobalVariable::removeFromParent方法代码示例

// 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_global_to_llvm - Emit the specified VAR_DECL or aggregate CONST_DECL to
/// LLVM as a global variable.  This function implements the end of
/// assemble_variable.
void emit_global_to_llvm(tree decl) {
  if (errorcount || sorrycount) return;

  // FIXME: Support alignment on globals: DECL_ALIGN.
  // FIXME: DECL_PRESERVE_P indicates the var is marked with attribute 'used'.

  // Global register variables don't turn into LLVM GlobalVariables.
  if (TREE_CODE(decl) == VAR_DECL && DECL_REGISTER(decl))
    return;

  timevar_push(TV_LLVM_GLOBALS);

  // Get or create the global variable now.
  GlobalVariable *GV = cast<GlobalVariable>(DECL_LLVM(decl));
  
  // Convert the initializer over.
  Constant *Init;
  if (DECL_INITIAL(decl) == 0 || DECL_INITIAL(decl) == error_mark_node) {
    // This global should be zero initialized.  Reconvert the type in case the
    // forward def of the global and the real def differ in type (e.g. declared
    // as 'int A[]', and defined as 'int A[100]').
    Init = Constant::getNullValue(ConvertType(TREE_TYPE(decl)));
  } else {
    assert((TREE_CONSTANT(DECL_INITIAL(decl)) || 
            TREE_CODE(DECL_INITIAL(decl)) == STRING_CST) &&
           "Global initializer should be constant!");
    
    // Temporarily set an initializer for the global, so we don't infinitely
    // recurse.  If we don't do this, we can hit cases where we see "oh a global
    // with an initializer hasn't been initialized yet, call emit_global_to_llvm
    // on it".  When constructing the initializer it might refer to itself.
    // this can happen for things like void *G = &G;
    //
    GV->setInitializer(UndefValue::get(GV->getType()->getElementType()));
    Init = TreeConstantToLLVM::Convert(DECL_INITIAL(decl));
  }

  // If we had a forward definition that has a type that disagrees with our
  // initializer, insert a cast now.  This sort of thing occurs when we have a
  // global union, and the LLVM type followed a union initializer that is
  // different from the union element used for the type.
  if (GV->getType()->getElementType() != Init->getType()) {
    GV->removeFromParent();
    GlobalVariable *NGV = new GlobalVariable(Init->getType(), GV->isConstant(),
                                             GlobalValue::ExternalLinkage, 0,
                                             GV->getName(), TheModule);
    GV->replaceAllUsesWith(ConstantExpr::getBitCast(NGV, GV->getType()));
    delete GV;
    SET_DECL_LLVM(decl, NGV);
    GV = NGV;
  }
 
  // Set the initializer.
  GV->setInitializer(Init);

  // Set thread local (TLS)
  if (TREE_CODE(decl) == VAR_DECL && DECL_THREAD_LOCAL(decl))
    GV->setThreadLocal(true);

  // Set the linkage.
  if (!TREE_PUBLIC(decl)) {
    GV->setLinkage(GlobalValue::InternalLinkage);
  } else if (DECL_WEAK(decl) || DECL_ONE_ONLY(decl) ||
             (DECL_COMMON(decl) &&  // DECL_COMMON is only meaningful if no init
              (!DECL_INITIAL(decl) || DECL_INITIAL(decl) == error_mark_node))) {
    // llvm-gcc also includes DECL_VIRTUAL_P here.
    GV->setLinkage(GlobalValue::WeakLinkage);
  } else if (DECL_COMDAT(decl)) {
    GV->setLinkage(GlobalValue::LinkOnceLinkage);
  }

#ifdef TARGET_ADJUST_LLVM_LINKAGE
  TARGET_ADJUST_LLVM_LINKAGE(GV,decl);
#endif /* TARGET_ADJUST_LLVM_LINKAGE */

  // Handle visibility style
  if (TREE_PUBLIC(decl)) {
    if (DECL_VISIBILITY(decl) == VISIBILITY_HIDDEN)
      GV->setVisibility(GlobalValue::HiddenVisibility);
    else if (DECL_VISIBILITY(decl) == VISIBILITY_PROTECTED)
      GV->setVisibility(GlobalValue::ProtectedVisibility);
  }

  // Set the section for the global.
  if (TREE_CODE(decl) == VAR_DECL || TREE_CODE(decl) == CONST_DECL) {
    if (DECL_SECTION_NAME(decl)) {
      GV->setSection(TREE_STRING_POINTER(DECL_SECTION_NAME(decl)));
#ifdef LLVM_IMPLICIT_TARGET_GLOBAL_VAR_SECTION
    } else if (const char *Section = 
                LLVM_IMPLICIT_TARGET_GLOBAL_VAR_SECTION(decl)) {
      GV->setSection(Section);
#endif
    }
    
    // Set the alignment for the global if one of the following condition is met
    // 1) DECL_ALIGN_UNIT does not match alignment as per ABI specification
    // 2) DECL_ALIGN is set by user.
//.........这里部分代码省略.........