1 //===-- GCMetadata.h - Garbage collector metadata -------------------------===//
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 // This file declares the GCFunctionInfo and GCModuleInfo classes, which are
11 // used as a communication channel from the target code generator to the target
12 // garbage collectors. This interface allows code generators and garbage
13 // collectors to be developed independently.
15 // The GCFunctionInfo class logs the data necessary to build a type accurate
16 // stack map. The code generator outputs:
18 // - Safe points as specified by the GCStrategy's NeededSafePoints.
19 // - Stack offsets for GC roots, as specified by calls to llvm.gcroot
21 // As a refinement, liveness analysis calculates the set of live roots at each
22 // safe point. Liveness analysis is not presently performed by the code
23 // generator, so all roots are assumed live.
25 // GCModuleInfo simply collects GCFunctionInfo instances for each Function as
26 // they are compiled. This accretion is necessary for collectors which must emit
27 // a stack map for the compilation unit as a whole. Therefore, GCFunctionInfo
28 // outlives the MachineFunction from which it is derived and must not refer to
29 // any code generator data structures.
31 //===----------------------------------------------------------------------===//
33 #ifndef LLVM_CODEGEN_GCMETADATA_H
34 #define LLVM_CODEGEN_GCMETADATA_H
36 #include "llvm/Pass.h"
37 #include "llvm/ADT/DenseMap.h"
38 #include "llvm/ADT/StringMap.h"
49 /// PointKind - The type of a collector-safe point.
52 Loop, //< Instr is a loop (backwards branch).
53 Return, //< Instr is a return instruction.
54 PreCall, //< Instr is a call instruction.
55 PostCall //< Instr is the return address of a call.
59 /// GCPoint - Metadata for a collector-safe point in machine code.
62 GC::PointKind Kind; //< The kind of the safe point.
63 unsigned Num; //< Usually a label.
65 GCPoint(GC::PointKind K, unsigned N) : Kind(K), Num(N) {}
68 /// GCRoot - Metadata for a pointer to an object managed by the garbage
71 int Num; //< Usually a frame index.
72 int StackOffset; //< Offset from the stack pointer.
73 Constant *Metadata; //< Metadata straight from the call to llvm.gcroot.
75 GCRoot(int N, Constant *MD) : Num(N), StackOffset(-1), Metadata(MD) {}
79 /// GCFunctionInfo - Garbage collection metadata for a single function.
81 class GCFunctionInfo {
83 typedef std::vector<GCPoint>::iterator iterator;
84 typedef std::vector<GCRoot>::iterator roots_iterator;
85 typedef std::vector<GCRoot>::const_iterator live_iterator;
91 std::vector<GCRoot> Roots;
92 std::vector<GCPoint> SafePoints;
94 // FIXME: Liveness. A 2D BitVector, perhaps?
96 // BitVector Liveness;
98 // bool islive(int point, int root) =
99 // Liveness[point * SafePoints.size() + root]
101 // The bit vector is the more compact representation where >3.2% of roots
102 // are live per safe point (1.5% on 64-bit hosts).
105 GCFunctionInfo(const Function &F, GCStrategy &S);
108 /// getFunction - Return the function to which this metadata applies.
110 const Function &getFunction() const { return F; }
112 /// getStrategy - Return the GC strategy for the function.
114 GCStrategy &getStrategy() { return S; }
116 /// addStackRoot - Registers a root that lives on the stack. Num is the
117 /// stack object ID for the alloca (if the code generator is
118 // using MachineFrameInfo).
119 void addStackRoot(int Num, Constant *Metadata) {
120 Roots.push_back(GCRoot(Num, Metadata));
123 /// addSafePoint - Notes the existence of a safe point. Num is the ID of the
124 /// label just prior to the safe point (if the code generator is using
125 /// MachineModuleInfo).
126 void addSafePoint(GC::PointKind Kind, unsigned Num) {
127 SafePoints.push_back(GCPoint(Kind, Num));
130 /// getFrameSize/setFrameSize - Records the function's frame size.
132 uint64_t getFrameSize() const { return FrameSize; }
133 void setFrameSize(uint64_t S) { FrameSize = S; }
135 /// begin/end - Iterators for safe points.
137 iterator begin() { return SafePoints.begin(); }
138 iterator end() { return SafePoints.end(); }
139 size_t size() const { return SafePoints.size(); }
141 /// roots_begin/roots_end - Iterators for all roots in the function.
143 roots_iterator roots_begin() { return Roots.begin(); }
144 roots_iterator roots_end () { return Roots.end(); }
145 size_t roots_size() const { return Roots.size(); }
147 /// live_begin/live_end - Iterators for live roots at a given safe point.
149 live_iterator live_begin(const iterator &p) { return roots_begin(); }
150 live_iterator live_end (const iterator &p) { return roots_end(); }
151 size_t live_size(const iterator &p) const { return roots_size(); }
155 /// GCModuleInfo - Garbage collection metadata for a whole module.
157 class GCModuleInfo : public ImmutablePass {
158 typedef StringMap<GCStrategy*> strategy_map_type;
159 typedef std::vector<GCStrategy*> list_type;
160 typedef DenseMap<const Function*,GCFunctionInfo*> finfo_map_type;
162 strategy_map_type StrategyMap;
163 list_type StrategyList;
164 finfo_map_type FInfoMap;
166 GCStrategy *getOrCreateStrategy(const Module *M, const std::string &Name);
169 typedef list_type::const_iterator iterator;
176 /// clear - Resets the pass. The metadata deleter pass calls this.
180 /// begin/end - Iterators for used strategies.
182 iterator begin() const { return StrategyList.begin(); }
183 iterator end() const { return StrategyList.end(); }
185 /// get - Look up function metadata.
187 GCFunctionInfo &getFunctionInfo(const Function &F);