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 }
51