xref: /llvm-project/llvm/lib/IR/BuiltinGCs.cpp (revision 267768c9dd2657494a3d1314be8eb48ec3984914)
1d8b37de8SMax Kazantsev //===- BuiltinGCs.cpp - Boilerplate for our built in GC types -------------===//
2d8b37de8SMax Kazantsev //
3d8b37de8SMax Kazantsev // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4d8b37de8SMax Kazantsev // See https://llvm.org/LICENSE.txt for license information.
5d8b37de8SMax Kazantsev // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6d8b37de8SMax Kazantsev //
7d8b37de8SMax Kazantsev //===----------------------------------------------------------------------===//
8d8b37de8SMax Kazantsev //
9d8b37de8SMax Kazantsev // This file contains the boilerplate required to define our various built in
10d8b37de8SMax Kazantsev // gc lowering strategies.
11d8b37de8SMax Kazantsev //
12d8b37de8SMax Kazantsev //===----------------------------------------------------------------------===//
13d8b37de8SMax Kazantsev 
14d8b37de8SMax Kazantsev #include "llvm/IR/BuiltinGCs.h"
15d8b37de8SMax Kazantsev #include "llvm/IR/GCStrategy.h"
16d8b37de8SMax Kazantsev #include "llvm/IR/DerivedTypes.h"
17d8b37de8SMax Kazantsev #include "llvm/Support/Casting.h"
18d8b37de8SMax Kazantsev 
19d8b37de8SMax Kazantsev using namespace llvm;
20d8b37de8SMax Kazantsev 
21d8b37de8SMax Kazantsev namespace {
22d8b37de8SMax Kazantsev 
23a2d45017SKazu Hirata /// An example GC which attempts to be compatible with Erlang/OTP garbage
24d8b37de8SMax Kazantsev /// collector.
25d8b37de8SMax Kazantsev ///
26d8b37de8SMax Kazantsev /// The frametable emitter is in ErlangGCPrinter.cpp.
27d8b37de8SMax Kazantsev class ErlangGC : public GCStrategy {
28d8b37de8SMax Kazantsev public:
ErlangGC()29d8b37de8SMax Kazantsev   ErlangGC() {
30d8b37de8SMax Kazantsev     NeededSafePoints = true;
31d8b37de8SMax Kazantsev     UsesMetadata = true;
32d8b37de8SMax Kazantsev   }
33d8b37de8SMax Kazantsev };
34d8b37de8SMax Kazantsev 
35d8b37de8SMax Kazantsev /// An example GC which attempts to be compatible with Objective Caml 3.10.0
36d8b37de8SMax Kazantsev ///
37d8b37de8SMax Kazantsev /// The frametable emitter is in OcamlGCPrinter.cpp.
38d8b37de8SMax Kazantsev class OcamlGC : public GCStrategy {
39d8b37de8SMax Kazantsev public:
OcamlGC()40d8b37de8SMax Kazantsev   OcamlGC() {
41d8b37de8SMax Kazantsev     NeededSafePoints = true;
42d8b37de8SMax Kazantsev     UsesMetadata = true;
43d8b37de8SMax Kazantsev   }
44d8b37de8SMax Kazantsev };
45d8b37de8SMax Kazantsev 
46d8b37de8SMax Kazantsev /// A GC strategy for uncooperative targets.  This implements lowering for the
47d8b37de8SMax Kazantsev /// llvm.gc* intrinsics for targets that do not natively support them (which
48d8b37de8SMax Kazantsev /// includes the C backend). Note that the code generated is not quite as
49d8b37de8SMax Kazantsev /// efficient as algorithms which generate stack maps to identify roots.
50d8b37de8SMax Kazantsev ///
51d8b37de8SMax Kazantsev /// In order to support this particular transformation, all stack roots are
52d8b37de8SMax Kazantsev /// coallocated in the stack. This allows a fully target-independent stack map
53d8b37de8SMax Kazantsev /// while introducing only minor runtime overhead.
54d8b37de8SMax Kazantsev class ShadowStackGC : public GCStrategy {
55d8b37de8SMax Kazantsev public:
563a3cb929SKazu Hirata   ShadowStackGC() = default;
57d8b37de8SMax Kazantsev };
58d8b37de8SMax Kazantsev 
59d8b37de8SMax Kazantsev /// A GCStrategy which serves as an example for the usage of a statepoint based
60d8b37de8SMax Kazantsev /// lowering strategy.  This GCStrategy is intended to suitable as a default
61d8b37de8SMax Kazantsev /// implementation usable with any collector which can consume the standard
62d8b37de8SMax Kazantsev /// stackmap format generated by statepoints, uses the default addrespace to
63d8b37de8SMax Kazantsev /// distinguish between gc managed and non-gc managed pointers, and has
64d8b37de8SMax Kazantsev /// reasonable relocation semantics.
65d8b37de8SMax Kazantsev class StatepointGC : public GCStrategy {
66d8b37de8SMax Kazantsev public:
StatepointGC()67d8b37de8SMax Kazantsev   StatepointGC() {
68d8b37de8SMax Kazantsev     UseStatepoints = true;
69*267768c9SCampbell Suter     UseRS4GC = true;
70d8b37de8SMax Kazantsev     // These options are all gc.root specific, we specify them so that the
71d8b37de8SMax Kazantsev     // gc.root lowering code doesn't run.
72d8b37de8SMax Kazantsev     NeededSafePoints = false;
73d8b37de8SMax Kazantsev     UsesMetadata = false;
74d8b37de8SMax Kazantsev   }
75d8b37de8SMax Kazantsev 
isGCManagedPointer(const Type * Ty) const7689fae41eSFangrui Song   std::optional<bool> isGCManagedPointer(const Type *Ty) const override {
77d8b37de8SMax Kazantsev     // Method is only valid on pointer typed values.
78d8b37de8SMax Kazantsev     const PointerType *PT = cast<PointerType>(Ty);
79d8b37de8SMax Kazantsev     // For the sake of this example GC, we arbitrarily pick addrspace(1) as our
80d8b37de8SMax Kazantsev     // GC managed heap.  We know that a pointer into this heap needs to be
81d8b37de8SMax Kazantsev     // updated and that no other pointer does.  Note that addrspace(1) is used
82d8b37de8SMax Kazantsev     // only as an example, it has no special meaning, and is not reserved for
83d8b37de8SMax Kazantsev     // GC usage.
84d8b37de8SMax Kazantsev     return (1 == PT->getAddressSpace());
85d8b37de8SMax Kazantsev   }
86d8b37de8SMax Kazantsev };
87d8b37de8SMax Kazantsev 
88d8b37de8SMax Kazantsev /// A GCStrategy for the CoreCLR Runtime. The strategy is similar to
89d8b37de8SMax Kazantsev /// Statepoint-example GC, but differs from it in certain aspects, such as:
90d8b37de8SMax Kazantsev /// 1) Base-pointers need not be explicitly tracked and reported for
91d8b37de8SMax Kazantsev ///    interior pointers
92d8b37de8SMax Kazantsev /// 2) Uses a different format for encoding stack-maps
93d8b37de8SMax Kazantsev /// 3) Location of Safe-point polls: polls are only needed before loop-back
94d8b37de8SMax Kazantsev ///    edges and before tail-calls (not needed at function-entry)
95d8b37de8SMax Kazantsev ///
96d8b37de8SMax Kazantsev /// The above differences in behavior are to be implemented in upcoming
97d8b37de8SMax Kazantsev /// checkins.
98d8b37de8SMax Kazantsev class CoreCLRGC : public GCStrategy {
99d8b37de8SMax Kazantsev public:
CoreCLRGC()100d8b37de8SMax Kazantsev   CoreCLRGC() {
101d8b37de8SMax Kazantsev     UseStatepoints = true;
102*267768c9SCampbell Suter     UseRS4GC = true;
103d8b37de8SMax Kazantsev     // These options are all gc.root specific, we specify them so that the
104d8b37de8SMax Kazantsev     // gc.root lowering code doesn't run.
105d8b37de8SMax Kazantsev     NeededSafePoints = false;
106d8b37de8SMax Kazantsev     UsesMetadata = false;
107d8b37de8SMax Kazantsev   }
108d8b37de8SMax Kazantsev 
isGCManagedPointer(const Type * Ty) const10989fae41eSFangrui Song   std::optional<bool> isGCManagedPointer(const Type *Ty) const override {
110d8b37de8SMax Kazantsev     // Method is only valid on pointer typed values.
111d8b37de8SMax Kazantsev     const PointerType *PT = cast<PointerType>(Ty);
112d8b37de8SMax Kazantsev     // We pick addrspace(1) as our GC managed heap.
113d8b37de8SMax Kazantsev     return (1 == PT->getAddressSpace());
114d8b37de8SMax Kazantsev   }
115d8b37de8SMax Kazantsev };
116d8b37de8SMax Kazantsev 
117d8b37de8SMax Kazantsev } // end anonymous namespace
118d8b37de8SMax Kazantsev 
119d8b37de8SMax Kazantsev // Register all the above so that they can be found at runtime.  Note that
120d8b37de8SMax Kazantsev // these static initializers are important since the registration list is
121d8b37de8SMax Kazantsev // constructed from their storage.
122d8b37de8SMax Kazantsev static GCRegistry::Add<ErlangGC> A("erlang",
123d8b37de8SMax Kazantsev                                    "erlang-compatible garbage collector");
124d8b37de8SMax Kazantsev static GCRegistry::Add<OcamlGC> B("ocaml", "ocaml 3.10-compatible GC");
125d8b37de8SMax Kazantsev static GCRegistry::Add<ShadowStackGC>
126d8b37de8SMax Kazantsev     C("shadow-stack", "Very portable GC for uncooperative code generators");
127d8b37de8SMax Kazantsev static GCRegistry::Add<StatepointGC> D("statepoint-example",
128d8b37de8SMax Kazantsev                                        "an example strategy for statepoint");
129d8b37de8SMax Kazantsev static GCRegistry::Add<CoreCLRGC> E("coreclr", "CoreCLR-compatible GC");
130d8b37de8SMax Kazantsev 
131d8b37de8SMax Kazantsev // Provide hook to ensure the containing library is fully loaded.
linkAllBuiltinGCs()132d8b37de8SMax Kazantsev void llvm::linkAllBuiltinGCs() {}
133