// specified in a function's 'gc' attribute. Algorithms are enabled by setting
// flags in a subclass's constructor, and some virtual methods can be
// overridden.
-//
-// When requested, the GCStrategy will be populated with data about each
-// function which uses it. Specifically:
-//
+//
+// GCStrategy is relevant for implementations using either gc.root or
+// gc.statepoint based lowering strategies, but is currently focused mostly on
+// options for gc.root. This will change over time.
+//
+// When requested by a subclass of GCStrategy, the gc.root implementation will
+// populate GCModuleInfo and GCFunctionInfo with that about each Function in
+// the Module that opts in to garbage collection. Specifically:
+//
// - Safe points
// Garbage collection is generally only possible at certain points in code.
// GCStrategy can request that the collector insert such points:
// - At and after any call to a subroutine
// - Before returning from the current function
// - Before backwards branches (loops)
-//
+//
// - Roots
// When a reference to a GC-allocated object exists on the stack, it must be
// stored in an alloca registered with llvm.gcoot.
// This information can used to emit the metadata tables which are required by
// the target garbage collector runtime.
//
+// When used with gc.statepoint, information about safepoint and roots can be
+// found in the binary StackMap section after code generation. Safepoint
+// placement is currently the responsibility of the frontend, though late
+// insertion support is planned. gc.statepoint does not currently support
+// custom stack map formats; such can be generated by parsing the standard
+// stack map section if desired.
+//
+// The read and write barrier support can be used with either implementation.
+//
//===----------------------------------------------------------------------===//
-#ifndef LLVM_CODEGEN_GCSTRATEGY_H
-#define LLVM_CODEGEN_GCSTRATEGY_H
+#ifndef LLVM_IR_GCSTRATEGY_H
+#define LLVM_IR_GCSTRATEGY_H
-#include "llvm/CodeGen/GCMetadata.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Value.h"
+#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Registry.h"
#include <string>
namespace llvm {
-
- class GCStrategy;
-
- /// The GC strategy registry uses all the defaults from Registry.
- ///
- typedef Registry<GCStrategy> GCRegistry;
-
- /// GCStrategy describes a garbage collector algorithm's code generation
- /// requirements, and provides overridable hooks for those needs which cannot
- /// be abstractly described.
- class GCStrategy {
- public:
- typedef std::vector<GCFunctionInfo*> list_type;
- typedef list_type::iterator iterator;
-
- private:
- friend class GCModuleInfo;
- const Module *M;
- std::string Name;
-
- list_type Functions;
-
- protected:
- unsigned NeededSafePoints; //< Bitmask of required safe points.
- bool CustomReadBarriers; //< Default is to insert loads.
- bool CustomWriteBarriers; //< Default is to insert stores.
- bool CustomRoots; //< Default is to pass through to backend.
- bool InitRoots; //< If set, roots are nulled during lowering.
- bool UsesMetadata; //< If set, backend must emit metadata tables.
-
- public:
- GCStrategy();
-
- virtual ~GCStrategy();
-
-
- /// getName - The name of the GC strategy, for debugging.
- ///
- const std::string &getName() const { return Name; }
-
- /// getModule - The module within which the GC strategy is operating.
- ///
- const Module &getModule() const { return *M; }
-
- /// needsSafePoitns - True if safe points of any kind are required. By
- // default, none are recorded.
- bool needsSafePoints() const { return NeededSafePoints != 0; }
-
- /// needsSafePoint(Kind) - True if the given kind of safe point is
- // required. By default, none are recorded.
- bool needsSafePoint(GC::PointKind Kind) const {
- return (NeededSafePoints & 1 << Kind) != 0;
- }
-
- /// customWriteBarrier - By default, write barriers are replaced with simple
- /// store instructions. If true, then
- /// performCustomLowering must instead lower them.
- bool customWriteBarrier() const { return CustomWriteBarriers; }
-
- /// customReadBarrier - By default, read barriers are replaced with simple
- /// load instructions. If true, then
- /// performCustomLowering must instead lower them.
- bool customReadBarrier() const { return CustomReadBarriers; }
-
- /// customRoots - By default, roots are left for the code generator so it
- /// can generate a stack map. If true, then
- // performCustomLowering must delete them.
- bool customRoots() const { return CustomRoots; }
-
- /// initializeRoots - If set, gcroot intrinsics should initialize their
- // allocas to null before the first use. This is
- // necessary for most GCs and is enabled by default.
- bool initializeRoots() const { return InitRoots; }
-
- /// usesMetadata - If set, appropriate metadata tables must be emitted by
- /// the back-end (assembler, JIT, or otherwise).
- bool usesMetadata() const { return UsesMetadata; }
-
- /// begin/end - Iterators for function metadata.
- ///
- iterator begin() { return Functions.begin(); }
- iterator end() { return Functions.end(); }
-
- /// insertFunctionMetadata - Creates metadata for a function.
- ///
- GCFunctionInfo *insertFunctionInfo(const Function &F);
-
- /// initializeCustomLowering/performCustomLowering - If any of the actions
- /// are set to custom, performCustomLowering must be overriden to transform
- /// the corresponding actions to LLVM IR. initializeCustomLowering is
- /// optional to override. These are the only GCStrategy methods through
- /// which the LLVM IR can be modified.
- virtual bool initializeCustomLowering(Module &F);
- virtual bool performCustomLowering(Function &F);
- };
-
+namespace GC {
+/// PointKind - Used to indicate whether the address of the call instruction
+/// or the address after the call instruction is listed in the stackmap. For
+/// most runtimes, PostCall safepoints are appropriate.
+///
+enum PointKind {
+ PreCall, ///< Instr is a call instruction.
+ PostCall ///< Instr is the return address of a call.
+};
+}
+
+/// GCStrategy describes a garbage collector algorithm's code generation
+/// requirements, and provides overridable hooks for those needs which cannot
+/// be abstractly described. GCStrategy objects must be looked up through
+/// the Function. The objects themselves are owned by the Context and must
+/// be immutable.
+class GCStrategy {
+private:
+ std::string Name;
+ friend class GCModuleInfo;
+
+protected:
+ bool UseStatepoints; /// Uses gc.statepoints as opposed to gc.roots,
+ /// if set, none of the other options can be
+ /// anything but their default values.
+
+ unsigned NeededSafePoints; ///< Bitmask of required safe points.
+ bool CustomReadBarriers; ///< Default is to insert loads.
+ bool CustomWriteBarriers; ///< Default is to insert stores.
+ bool CustomRoots; ///< Default is to pass through to backend.
+ bool InitRoots; ///< If set, roots are nulled during lowering.
+ bool UsesMetadata; ///< If set, backend must emit metadata tables.
+
+public:
+ GCStrategy();
+ virtual ~GCStrategy() {}
+
+ /// Return the name of the GC strategy. This is the value of the collector
+ /// name string specified on functions which use this strategy.
+ const std::string &getName() const { return Name; }
+
+ /// By default, write barriers are replaced with simple store
+ /// instructions. If true, you must provide a custom pass to lower
+ /// calls to @llvm.gcwrite.
+ bool customWriteBarrier() const { return CustomWriteBarriers; }
+
+ /// By default, read barriers are replaced with simple load
+ /// instructions. If true, you must provide a custom pass to lower
+ /// calls to @llvm.gcread.
+ bool customReadBarrier() const { return CustomReadBarriers; }
+
+ /// Returns true if this strategy is expecting the use of gc.statepoints,
+ /// and false otherwise.
+ bool useStatepoints() const { return UseStatepoints; }
+
+ /** @name Statepoint Specific Properties */
+ ///@{
+
+ /// If the type specified can be reliably distinguished, returns true for
+ /// pointers to GC managed locations and false for pointers to non-GC
+ /// managed locations. Note a GCStrategy can always return 'None' (i.e. an
+ /// empty optional indicating it can't reliably distinguish.
+ virtual Optional<bool> isGCManagedPointer(const Type *Ty) const {
+ return None;
+ }
+ ///@}
+
+ /** @name GCRoot Specific Properties
+ * These properties and overrides only apply to collector strategies using
+ * GCRoot.
+ */
+ ///@{
+
+ /// True if safe points of any kind are required. By default, none are
+ /// recorded.
+ bool needsSafePoints() const { return NeededSafePoints != 0; }
+
+ /// True if the given kind of safe point is required. By default, none are
+ /// recorded.
+ bool needsSafePoint(GC::PointKind Kind) const {
+ return (NeededSafePoints & 1 << Kind) != 0;
+ }
+
+ /// By default, roots are left for the code generator so it can generate a
+ /// stack map. If true, you must provide a custom pass to lower
+ /// calls to @llvm.gcroot.
+ bool customRoots() const { return CustomRoots; }
+
+ /// If set, gcroot intrinsics should initialize their allocas to null
+ /// before the first use. This is necessary for most GCs and is enabled by
+ /// default.
+ bool initializeRoots() const { return InitRoots; }
+
+ /// If set, appropriate metadata tables must be emitted by the back-end
+ /// (assembler, JIT, or otherwise). For statepoint, this method is
+ /// currently unsupported. The stackmap information can be found in the
+ /// StackMap section as described in the documentation.
+ bool usesMetadata() const { return UsesMetadata; }
+
+ ///@}
+};
+
+/// Subclasses of GCStrategy are made available for use during compilation by
+/// adding them to the global GCRegistry. This can done either within the
+/// LLVM source tree or via a loadable plugin. An example registeration
+/// would be:
+/// static GCRegistry::Add<CustomGC> X("custom-name",
+/// "my custom supper fancy gc strategy");
+///
+/// Note that to use a custom GCMetadataPrinter w/gc.roots, you must also
+/// register your GCMetadataPrinter subclass with the
+/// GCMetadataPrinterRegistery as well.
+typedef Registry<GCStrategy> GCRegistry;
}
#endif
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