llvm/lib/IR/GCStrategy.cpp

   1 //===- GCStrategy.cpp - Garbage Collector Description ---------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the policy object GCStrategy which describes the
  10 // behavior of a given garbage collector.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/IR/GCStrategy.h"
  15 #include "llvm/ADT/Twine.h"
  16 #include "llvm/IR/BuiltinGCs.h"
  17
  18 using namespace llvm;
  19
  20 LLVM_INSTANTIATE_REGISTRY(GCRegistry)
  21
  22 GCStrategy::GCStrategy() = default;
  23
  24 std::unique_ptr<GCStrategy> llvm::getGCStrategy(const StringRef Name) {
  25   for (auto &S : GCRegistry::entries())
  26     if (S.getName() == Name)
  27       return S.instantiate();
  28
  29   // We need to link all the builtin GCs when LLVM is used as a static library.
  30   // The linker will quite happily remove the static constructors that register
  31   // the builtin GCs if we don't use a function from that object. This function
  32   // does nothing but we need to make sure it is (or at least could be, even
  33   // with all optimisations enabled) called *somewhere*, and this is a good
  34   // place to do that: if the GC strategies are being used then this function
  35   // obviously can't be removed by the linker, and here it won't affect
  36   // performance, since there's about to be a fatal error anyway.
  37   llvm::linkAllBuiltinGCs();
  38
  39   if (GCRegistry::begin() == GCRegistry::end()) {
  40     // In normal operation, the registry should not be empty.  There should
  41     // be the builtin GCs if nothing else.  The most likely scenario here is
  42     // that we got here without running the initializers used by the Registry
  43     // itself and it's registration mechanism.
  44     const std::string error =
  45         std::string("unsupported GC: ") + Name.str() +
  46         " (did you remember to link and initialize the library?)";
  47     report_fatal_error(Twine(error));
  48   } else
  49     report_fatal_error(Twine(std::string("unsupported GC: ") + Name.str()));
  50 }