//===- GCStrategy.cpp - Garbage Collector Description ---------------------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file implements the policy object GCStrategy which describes the

// behavior of a given garbage collector.

//

//===----------------------------------------------------------------------===//

#include "llvm/IR/GCStrategy.h"

#include "llvm/ADT/Twine.h"

#include "llvm/IR/BuiltinGCs.h"

using namespace llvm;

LLVM_INSTANTIATE_REGISTRY(GCRegistry)

GCStrategy::GCStrategy() = default;

std::unique_ptr<GCStrategy> llvm::getGCStrategy(const StringRef Name) {

  for (auto &S : GCRegistry::entries())

    if (S.getName() == Name)

      return S.instantiate();

  // We need to link all the builtin GCs when LLVM is used as a static library.

  // The linker will quite happily remove the static constructors that register

  // the builtin GCs if we don't use a function from that object. This function

  // does nothing but we need to make sure it is (or at least could be, even

  // with all optimisations enabled) called *somewhere*, and this is a good

  // place to do that: if the GC strategies are being used then this function

  // obviously can't be removed by the linker, and here it won't affect

  // performance, since there's about to be a fatal error anyway.

  llvm::linkAllBuiltinGCs();

  if (GCRegistry::begin() == GCRegistry::end()) {

    // In normal operation, the registry should not be empty.  There should

    // be the builtin GCs if nothing else.  The most likely scenario here is

    // that we got here without running the initializers used by the Registry

    // itself and it's registration mechanism.

    const std::string error =

        std::string("unsupported GC: ") + Name.str() +

        " (did you remember to link and initialize the library?)";

    report_fatal_error(Twine(error));

  } else

    report_fatal_error(Twine(std::string("unsupported GC: ") + Name.str()));

}