-//===-- ElimAvailExtern.cpp - DCE unreachable internal functions ----------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This transform is designed to eliminate available external global
-// definitions from the program, turning them into declarations.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/IPO.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Transforms/Utils/CtorUtils.h"
-#include "llvm/Transforms/Utils/GlobalStatus.h"
-#include "llvm/Pass.h"
-using namespace llvm;
-
-#define DEBUG_TYPE "elim-avail-extern"
-
-STATISTIC(NumAliases , "Number of global aliases removed");
-STATISTIC(NumFunctions, "Number of functions removed");
-STATISTIC(NumVariables, "Number of global variables removed");
-
-namespace {
- struct EliminateAvailableExternally : public ModulePass {
- static char ID; // Pass identification, replacement for typeid
- EliminateAvailableExternally() : ModulePass(ID) {
- initializeEliminateAvailableExternallyPass(
- *PassRegistry::getPassRegistry());
- }
-
- // run - Do the EliminateAvailableExternally pass on the specified module,
- // optionally updating the specified callgraph to reflect the changes.
- //
- bool runOnModule(Module &M) override;
- };
-}
-
-char EliminateAvailableExternally::ID = 0;
-INITIALIZE_PASS(EliminateAvailableExternally, "elim-avail-extern",
- "Eliminate Available Externally Globals", false, false)
-
-ModulePass *llvm::createEliminateAvailableExternallyPass() {
- return new EliminateAvailableExternally();
-}
-
-bool EliminateAvailableExternally::runOnModule(Module &M) {
- bool Changed = false;
-
- // Drop initializers of available externally global variables.
- for (Module::global_iterator I = M.global_begin(), E = M.global_end();
- I != E; ++I) {
- if (!I->hasAvailableExternallyLinkage())
- continue;
- if (I->hasInitializer()) {
- Constant *Init = I->getInitializer();
- I->setInitializer(nullptr);
- if (isSafeToDestroyConstant(Init))
- Init->destroyConstant();
- }
- I->removeDeadConstantUsers();
- I->setLinkage(GlobalValue::ExternalLinkage);
- NumVariables++;
- }
-
- // Drop the bodies of available externally functions.
- for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
- if (!I->hasAvailableExternallyLinkage())
- continue;
- if (!I->isDeclaration())
- // This will set the linkage to external
- I->deleteBody();
- I->removeDeadConstantUsers();
- NumFunctions++;
- }
-
- // Drop targets of available externally aliases.
- for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); I != E;
- ++I) {
- if (!I->hasAvailableExternallyLinkage())
- continue;
- I->setAliasee(nullptr);
- I->removeDeadConstantUsers();
- I->setLinkage(GlobalValue::ExternalLinkage);
- NumAliases++;
- }
-
- return Changed;
-}