1 //===-- llvm/CodeGen/GCStrategy.h - Garbage collection ----------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // GCStrategy coordinates code generation algorithms and implements some itself
11 // in order to generate code compatible with a target code generator as
12 // specified in a function's 'gc' attribute. Algorithms are enabled by setting
13 // flags in a subclass's constructor, and some virtual methods can be
16 // When requested, the GCStrategy will be populated with data about each
17 // function which uses it. Specifically:
20 // Garbage collection is generally only possible at certain points in code.
21 // GCStrategy can request that the collector insert such points:
23 // - At and after any call to a subroutine
24 // - Before returning from the current function
25 // - Before backwards branches (loops)
28 // When a reference to a GC-allocated object exists on the stack, it must be
29 // stored in an alloca registered with llvm.gcoot.
31 // This information can used to emit the metadata tables which are required by
32 // the target garbage collector runtime.
34 //===----------------------------------------------------------------------===//
36 #ifndef LLVM_CODEGEN_GCSTRATEGY_H
37 #define LLVM_CODEGEN_GCSTRATEGY_H
39 #include "llvm/CodeGen/GCMetadata.h"
40 #include "llvm/Support/Registry.h"
47 /// The GC strategy registry uses all the defaults from Registry.
49 typedef Registry<GCStrategy> GCRegistry;
51 /// GCStrategy describes a garbage collector algorithm's code generation
52 /// requirements, and provides overridable hooks for those needs which cannot
53 /// be abstractly described.
56 typedef std::vector<GCFunctionInfo*> list_type;
57 typedef list_type::iterator iterator;
60 friend class GCModuleInfo;
67 unsigned NeededSafePoints; //< Bitmask of required safe points.
68 bool CustomReadBarriers; //< Default is to insert loads.
69 bool CustomWriteBarriers; //< Default is to insert stores.
70 bool CustomRoots; //< Default is to pass through to backend.
71 bool InitRoots; //< If set, roots are nulled during lowering.
72 bool UsesMetadata; //< If set, backend must emit metadata tables.
77 virtual ~GCStrategy();
80 /// getName - The name of the GC strategy, for debugging.
82 const std::string &getName() const { return Name; }
84 /// getModule - The module within which the GC strategy is operating.
86 const Module &getModule() const { return *M; }
88 /// needsSafePoitns - True if safe points of any kind are required. By
89 // default, none are recorded.
90 bool needsSafePoints() const { return NeededSafePoints != 0; }
92 /// needsSafePoint(Kind) - True if the given kind of safe point is
93 // required. By default, none are recorded.
94 bool needsSafePoint(GC::PointKind Kind) const {
95 return (NeededSafePoints & 1 << Kind) != 0;
98 /// customWriteBarrier - By default, write barriers are replaced with simple
99 /// store instructions. If true, then
100 /// performCustomLowering must instead lower them.
101 bool customWriteBarrier() const { return CustomWriteBarriers; }
103 /// customReadBarrier - By default, read barriers are replaced with simple
104 /// load instructions. If true, then
105 /// performCustomLowering must instead lower them.
106 bool customReadBarrier() const { return CustomReadBarriers; }
108 /// customRoots - By default, roots are left for the code generator so it
109 /// can generate a stack map. If true, then
110 // performCustomLowering must delete them.
111 bool customRoots() const { return CustomRoots; }
113 /// initializeRoots - If set, gcroot intrinsics should initialize their
114 // allocas to null before the first use. This is
115 // necessary for most GCs and is enabled by default.
116 bool initializeRoots() const { return InitRoots; }
118 /// usesMetadata - If set, appropriate metadata tables must be emitted by
119 /// the back-end (assembler, JIT, or otherwise).
120 bool usesMetadata() const { return UsesMetadata; }
122 /// begin/end - Iterators for function metadata.
124 iterator begin() { return Functions.begin(); }
125 iterator end() { return Functions.end(); }
127 /// insertFunctionMetadata - Creates metadata for a function.
129 GCFunctionInfo *insertFunctionInfo(const Function &F);
131 /// initializeCustomLowering/performCustomLowering - If any of the actions
132 /// are set to custom, performCustomLowering must be overriden to transform
133 /// the corresponding actions to LLVM IR. initializeCustomLowering is
134 /// optional to override. These are the only GCStrategy methods through
135 /// which the LLVM IR can be modified.
136 virtual bool initializeCustomLowering(Module &F);
137 virtual bool performCustomLowering(Function &F);