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//===- BuiltinGCs.cpp - Boilerplate for our built in GC types -------------===//
//
// 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 contains the boilerplate required to define our various built in
// gc lowering strategies.
//
//===----------------------------------------------------------------------===//
#include "llvm/IR/BuiltinGCs.h"
#include "llvm/IR/GCStrategy.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/Support/Casting.h"
using namespace llvm;
namespace {
/// An example GC which attempts to be compatible with Erlang/OTP garbage
/// collector.
///
/// The frametable emitter is in ErlangGCPrinter.cpp.
class ErlangGC : public GCStrategy {
public:
ErlangGC() {
NeededSafePoints = true;
UsesMetadata = true;
}
};
/// An example GC which attempts to be compatible with Objective Caml 3.10.0
///
/// The frametable emitter is in OcamlGCPrinter.cpp.
class OcamlGC : public GCStrategy {
public:
OcamlGC() {
NeededSafePoints = true;
UsesMetadata = true;
}
};
/// A GC strategy for uncooperative targets. This implements lowering for the
/// llvm.gc* intrinsics for targets that do not natively support them (which
/// includes the C backend). Note that the code generated is not quite as
/// efficient as algorithms which generate stack maps to identify roots.
///
/// In order to support this particular transformation, all stack roots are
/// coallocated in the stack. This allows a fully target-independent stack map
/// while introducing only minor runtime overhead.
class ShadowStackGC : public GCStrategy {
public:
ShadowStackGC() = default;
};
/// A GCStrategy which serves as an example for the usage of a statepoint based
/// lowering strategy. This GCStrategy is intended to suitable as a default
/// implementation usable with any collector which can consume the standard
/// stackmap format generated by statepoints, uses the default addrespace to
/// distinguish between gc managed and non-gc managed pointers, and has
/// reasonable relocation semantics.
class StatepointGC : public GCStrategy {
public:
StatepointGC() {
UseStatepoints = true;
UseRS4GC = true;
// These options are all gc.root specific, we specify them so that the
// gc.root lowering code doesn't run.
NeededSafePoints = false;
UsesMetadata = false;
}
std::optional<bool> isGCManagedPointer(const Type *Ty) const override {
// Method is only valid on pointer typed values.
const PointerType *PT = cast<PointerType>(Ty);
// For the sake of this example GC, we arbitrarily pick addrspace(1) as our
// GC managed heap. We know that a pointer into this heap needs to be
// updated and that no other pointer does. Note that addrspace(1) is used
// only as an example, it has no special meaning, and is not reserved for
// GC usage.
return (1 == PT->getAddressSpace());
}
};
/// A GCStrategy for the CoreCLR Runtime. The strategy is similar to
/// Statepoint-example GC, but differs from it in certain aspects, such as:
/// 1) Base-pointers need not be explicitly tracked and reported for
/// interior pointers
/// 2) Uses a different format for encoding stack-maps
/// 3) Location of Safe-point polls: polls are only needed before loop-back
/// edges and before tail-calls (not needed at function-entry)
///
/// The above differences in behavior are to be implemented in upcoming
/// checkins.
class CoreCLRGC : public GCStrategy {
public:
CoreCLRGC() {
UseStatepoints = true;
UseRS4GC = true;
// These options are all gc.root specific, we specify them so that the
// gc.root lowering code doesn't run.
NeededSafePoints = false;
UsesMetadata = false;
}
std::optional<bool> isGCManagedPointer(const Type *Ty) const override {
// Method is only valid on pointer typed values.
const PointerType *PT = cast<PointerType>(Ty);
// We pick addrspace(1) as our GC managed heap.
return (1 == PT->getAddressSpace());
}
};
} // end anonymous namespace
// Register all the above so that they can be found at runtime. Note that
// these static initializers are important since the registration list is
// constructed from their storage.
static GCRegistry::Add<ErlangGC> A("erlang",
"erlang-compatible garbage collector");
static GCRegistry::Add<OcamlGC> B("ocaml", "ocaml 3.10-compatible GC");
static GCRegistry::Add<ShadowStackGC>
C("shadow-stack", "Very portable GC for uncooperative code generators");
static GCRegistry::Add<StatepointGC> D("statepoint-example",
"an example strategy for statepoint");
static GCRegistry::Add<CoreCLRGC> E("coreclr", "CoreCLR-compatible GC");
// Provide hook to ensure the containing library is fully loaded.
void llvm::linkAllBuiltinGCs() {}
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