143 lines
5.4 KiB
C++
143 lines
5.4 KiB
C++
//===-- llvm/CodeGen/GCStrategy.h - Garbage collection ----------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// GCStrategy coordinates code generation algorithms and implements some itself
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// in order to generate code compatible with a target code generator as
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// specified in a function's 'gc' attribute. Algorithms are enabled by setting
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// flags in a subclass's constructor, and some virtual methods can be
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// overridden.
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//
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// When requested, the GCStrategy will be populated with data about each
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// function which uses it. Specifically:
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//
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// - Safe points
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// Garbage collection is generally only possible at certain points in code.
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// GCStrategy can request that the collector insert such points:
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//
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// - At and after any call to a subroutine
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// - Before returning from the current function
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// - Before backwards branches (loops)
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//
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// - Roots
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// When a reference to a GC-allocated object exists on the stack, it must be
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// stored in an alloca registered with llvm.gcoot.
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//
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// This information can used to emit the metadata tables which are required by
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// the target garbage collector runtime.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_GCSTRATEGY_H
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#define LLVM_CODEGEN_GCSTRATEGY_H
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#include "llvm/CodeGen/GCMetadata.h"
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#include "llvm/Support/Registry.h"
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#include <string>
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namespace llvm {
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class GCStrategy;
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/// The GC strategy registry uses all the defaults from Registry.
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///
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typedef Registry<GCStrategy> GCRegistry;
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/// GCStrategy describes a garbage collector algorithm's code generation
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/// requirements, and provides overridable hooks for those needs which cannot
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/// be abstractly described.
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class GCStrategy {
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public:
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typedef std::vector<GCFunctionInfo*> list_type;
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typedef list_type::iterator iterator;
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private:
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friend class GCModuleInfo;
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const Module *M;
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std::string Name;
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list_type Functions;
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protected:
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unsigned NeededSafePoints; //< Bitmask of required safe points.
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bool CustomReadBarriers; //< Default is to insert loads.
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bool CustomWriteBarriers; //< Default is to insert stores.
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bool CustomRoots; //< Default is to pass through to backend.
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bool InitRoots; //< If set, roots are nulled during lowering.
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bool UsesMetadata; //< If set, backend must emit metadata tables.
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public:
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GCStrategy();
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virtual ~GCStrategy();
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/// getName - The name of the GC strategy, for debugging.
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///
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const std::string &getName() const { return Name; }
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/// getModule - The module within which the GC strategy is operating.
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///
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const Module &getModule() const { return *M; }
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/// needsSafePoitns - True if safe points of any kind are required. By
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// default, none are recorded.
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bool needsSafePoints() const { return NeededSafePoints != 0; }
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/// needsSafePoint(Kind) - True if the given kind of safe point is
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// required. By default, none are recorded.
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bool needsSafePoint(GC::PointKind Kind) const {
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return (NeededSafePoints & 1 << Kind) != 0;
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}
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/// customWriteBarrier - By default, write barriers are replaced with simple
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/// store instructions. If true, then
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/// performCustomLowering must instead lower them.
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bool customWriteBarrier() const { return CustomWriteBarriers; }
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/// customReadBarrier - By default, read barriers are replaced with simple
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/// load instructions. If true, then
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/// performCustomLowering must instead lower them.
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bool customReadBarrier() const { return CustomReadBarriers; }
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/// customRoots - By default, roots are left for the code generator so it
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/// can generate a stack map. If true, then
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// performCustomLowering must delete them.
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bool customRoots() const { return CustomRoots; }
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/// initializeRoots - If set, gcroot intrinsics should initialize their
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// allocas to null before the first use. This is
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// necessary for most GCs and is enabled by default.
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bool initializeRoots() const { return InitRoots; }
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/// usesMetadata - If set, appropriate metadata tables must be emitted by
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/// the back-end (assembler, JIT, or otherwise).
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bool usesMetadata() const { return UsesMetadata; }
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/// begin/end - Iterators for function metadata.
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///
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iterator begin() { return Functions.begin(); }
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iterator end() { return Functions.end(); }
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/// insertFunctionMetadata - Creates metadata for a function.
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///
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GCFunctionInfo *insertFunctionInfo(const Function &F);
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/// initializeCustomLowering/performCustomLowering - If any of the actions
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/// are set to custom, performCustomLowering must be overriden to transform
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/// the corresponding actions to LLVM IR. initializeCustomLowering is
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/// optional to override. These are the only GCStrategy methods through
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/// which the LLVM IR can be modified.
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virtual bool initializeCustomLowering(Module &F);
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virtual bool performCustomLowering(Function &F);
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};
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}
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#endif
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