diff options
Diffstat (limited to 'include/llvm/CodeGen/GCStrategy.h')
| -rw-r--r-- | include/llvm/CodeGen/GCStrategy.h | 254 |
1 files changed, 139 insertions, 115 deletions
diff --git a/include/llvm/CodeGen/GCStrategy.h b/include/llvm/CodeGen/GCStrategy.h index 81e1f85..869f888 100644 --- a/include/llvm/CodeGen/GCStrategy.h +++ b/include/llvm/CodeGen/GCStrategy.h @@ -12,10 +12,15 @@ // 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: @@ -23,7 +28,7 @@ // - 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. @@ -31,123 +36,142 @@ // 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/CodeGen/MachineFunction.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<std::unique_ptr<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 CustomSafePoints; ///< Default is to use NeededSafePoints - ///< to find safe points. - 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 CustomSafePoints || 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; } - - /// customSafePoints - By default, the GC analysis will find safe - /// points according to NeededSafePoints. If true, - /// then findCustomSafePoints must create them. - bool customSafePoints() const { return CustomSafePoints; } - - /// 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); - virtual bool findCustomSafePoints(GCFunctionInfo& FI, MachineFunction& MF); - }; - +namespace GC { +/// PointKind - The type of a collector-safe point. +/// +enum PointKind { + Loop, ///< Instr is a loop (backwards branch). + Return, ///< Instr is a return instruction. + 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 value 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 Value *V) 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 |