[GC] Consolidate all built in GCs into a single file [NFC]

Combine a bunch of small files into a single, still rather small, file.  The primary purpose of this is to get all of the static initializers into a single file so as to have a well defined order of initialization.  

llvm-svn: 258109

1 files changed, 139 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/BuiltinGCs.cpp b/llvm/lib/CodeGen/BuiltinGCs.cpp
new file mode 100644
index 00000000000..ff7c99de042
--- /dev/null
+++ b/llvm/lib/CodeGen/BuiltinGCs.cpp
@@ -0,0 +1,139 @@
+//===-- BuiltinGCs.cpp - Boilerplate for our built in GC types --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the boilerplate required to define our various built in
+// gc lowering strategies.  
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/GCs.h"
+#include "llvm/CodeGen/GCStrategy.h"
+
+using namespace llvm;
+
+namespace {
+
+/// An example GC which attempts to be compatibile with Erlang/OTP garbage
+/// collector.
+///
+/// The frametable emitter is in ErlangGCPrinter.cpp.
+class ErlangGC : public GCStrategy {
+public:
+  ErlangGC() {
+    InitRoots = false;
+    NeededSafePoints = 1 << GC::PostCall;
+    UsesMetadata = true;
+    CustomRoots = false;
+  }
+};
+
+/// 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 = 1 << GC::PostCall;
+    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() {
+    InitRoots = true;
+    CustomRoots = true;
+  }
+};
+
+/// 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;
+    // These options are all gc.root specific, we specify them so that the
+    // gc.root lowering code doesn't run.
+    InitRoots = false;
+    NeededSafePoints = 0;
+    UsesMetadata = false;
+    CustomRoots = false;
+  }
+  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;
+    // These options are all gc.root specific, we specify them so that the
+    // gc.root lowering code doesn't run.
+    InitRoots = false;
+    NeededSafePoints = 0;
+    UsesMetadata = false;
+    CustomRoots = false;
+  }
+  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());
+  }
+};
+}
+
+// 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 hooks to ensure the containing library is fully loaded.
+void llvm::linkErlangGC() {}
+void llvm::linkOcamlGC() {}
+void llvm::linkShadowStackGC() {}
+void llvm::linkStatepointExampleGC() {}
+void llvm::linkCoreCLRGC() {}