GCMetadata.h revision 210299
1//===-- GCMetadata.h - Garbage collector metadata ---------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
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.
14//
15// The GCFunctionInfo class logs the data necessary to build a type accurate
16// stack map. The code generator outputs:
17//
18//   - Safe points as specified by the GCStrategy's NeededSafePoints.
19//   - Stack offsets for GC roots, as specified by calls to llvm.gcroot
20//
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.
24//
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.
30//
31//===----------------------------------------------------------------------===//
32
33#ifndef LLVM_CODEGEN_GCMETADATA_H
34#define LLVM_CODEGEN_GCMETADATA_H
35
36#include "llvm/Pass.h"
37#include "llvm/ADT/DenseMap.h"
38#include "llvm/ADT/StringMap.h"
39
40namespace llvm {
41  class AsmPrinter;
42  class GCStrategy;
43  class Constant;
44  class MCSymbol;
45
46  namespace GC {
47    /// PointKind - The type of a collector-safe point.
48    ///
49    enum PointKind {
50      Loop,    //< Instr is a loop (backwards branch).
51      Return,  //< Instr is a return instruction.
52      PreCall, //< Instr is a call instruction.
53      PostCall //< Instr is the return address of a call.
54    };
55  }
56
57  /// GCPoint - Metadata for a collector-safe point in machine code.
58  ///
59  struct GCPoint {
60    GC::PointKind Kind; //< The kind of the safe point.
61    MCSymbol *Label;    //< A label.
62
63    GCPoint(GC::PointKind K, MCSymbol *L) : Kind(K), Label(L) {}
64  };
65
66  /// GCRoot - Metadata for a pointer to an object managed by the garbage
67  /// collector.
68  struct GCRoot {
69    int Num;            //< Usually a frame index.
70    int StackOffset;    //< Offset from the stack pointer.
71    const Constant *Metadata;//< Metadata straight from the call to llvm.gcroot.
72
73    GCRoot(int N, const Constant *MD) : Num(N), StackOffset(-1), Metadata(MD) {}
74  };
75
76
77  /// GCFunctionInfo - Garbage collection metadata for a single function.
78  ///
79  class GCFunctionInfo {
80  public:
81    typedef std::vector<GCPoint>::iterator iterator;
82    typedef std::vector<GCRoot>::iterator roots_iterator;
83    typedef std::vector<GCRoot>::const_iterator live_iterator;
84
85  private:
86    const Function &F;
87    GCStrategy &S;
88    uint64_t FrameSize;
89    std::vector<GCRoot> Roots;
90    std::vector<GCPoint> SafePoints;
91
92    // FIXME: Liveness. A 2D BitVector, perhaps?
93    //
94    //   BitVector Liveness;
95    //
96    //   bool islive(int point, int root) =
97    //     Liveness[point * SafePoints.size() + root]
98    //
99    // The bit vector is the more compact representation where >3.2% of roots
100    // are live per safe point (1.5% on 64-bit hosts).
101
102  public:
103    GCFunctionInfo(const Function &F, GCStrategy &S);
104    ~GCFunctionInfo();
105
106    /// getFunction - Return the function to which this metadata applies.
107    ///
108    const Function &getFunction() const { return F; }
109
110    /// getStrategy - Return the GC strategy for the function.
111    ///
112    GCStrategy &getStrategy() { return S; }
113
114    /// addStackRoot - Registers a root that lives on the stack. Num is the
115    ///                stack object ID for the alloca (if the code generator is
116    //                 using  MachineFrameInfo).
117    void addStackRoot(int Num, const Constant *Metadata) {
118      Roots.push_back(GCRoot(Num, Metadata));
119    }
120
121    /// addSafePoint - Notes the existence of a safe point. Num is the ID of the
122    /// label just prior to the safe point (if the code generator is using
123    /// MachineModuleInfo).
124    void addSafePoint(GC::PointKind Kind, MCSymbol *Label) {
125      SafePoints.push_back(GCPoint(Kind, Label));
126    }
127
128    /// getFrameSize/setFrameSize - Records the function's frame size.
129    ///
130    uint64_t getFrameSize() const { return FrameSize; }
131    void setFrameSize(uint64_t S) { FrameSize = S; }
132
133    /// begin/end - Iterators for safe points.
134    ///
135    iterator begin() { return SafePoints.begin(); }
136    iterator end()   { return SafePoints.end();   }
137    size_t size() const { return SafePoints.size(); }
138
139    /// roots_begin/roots_end - Iterators for all roots in the function.
140    ///
141    roots_iterator roots_begin() { return Roots.begin(); }
142    roots_iterator roots_end  () { return Roots.end();   }
143    size_t roots_size() const { return Roots.size(); }
144
145    /// live_begin/live_end - Iterators for live roots at a given safe point.
146    ///
147    live_iterator live_begin(const iterator &p) { return roots_begin(); }
148    live_iterator live_end  (const iterator &p) { return roots_end();   }
149    size_t live_size(const iterator &p) const { return roots_size(); }
150  };
151
152
153  /// GCModuleInfo - Garbage collection metadata for a whole module.
154  ///
155  class GCModuleInfo : public ImmutablePass {
156    typedef StringMap<GCStrategy*> strategy_map_type;
157    typedef std::vector<GCStrategy*> list_type;
158    typedef DenseMap<const Function*,GCFunctionInfo*> finfo_map_type;
159
160    strategy_map_type StrategyMap;
161    list_type StrategyList;
162    finfo_map_type FInfoMap;
163
164    GCStrategy *getOrCreateStrategy(const Module *M, const std::string &Name);
165
166  public:
167    typedef list_type::const_iterator iterator;
168
169    static char ID;
170
171    GCModuleInfo();
172    ~GCModuleInfo();
173
174    /// clear - Resets the pass. The metadata deleter pass calls this.
175    ///
176    void clear();
177
178    /// begin/end - Iterators for used strategies.
179    ///
180    iterator begin() const { return StrategyList.begin(); }
181    iterator end()   const { return StrategyList.end();   }
182
183    /// get - Look up function metadata.
184    ///
185    GCFunctionInfo &getFunctionInfo(const Function &F);
186  };
187
188}
189
190#endif
191