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#include "llvm/Support/DebugLoc.h"
40
41namespace llvm {
42  class AsmPrinter;
43  class GCStrategy;
44  class Constant;
45  class MCSymbol;
46
47  namespace GC {
48    /// PointKind - The type of a collector-safe point.
49    ///
50    enum PointKind {
51      Loop,    ///< Instr is a loop (backwards branch).
52      Return,  ///< Instr is a return instruction.
53      PreCall, ///< Instr is a call instruction.
54      PostCall ///< Instr is the return address of a call.
55    };
56  }
57
58  /// GCPoint - Metadata for a collector-safe point in machine code.
59  ///
60  struct GCPoint {
61    GC::PointKind Kind; ///< The kind of the safe point.
62    MCSymbol *Label;    ///< A label.
63    DebugLoc Loc;
64
65    GCPoint(GC::PointKind K, MCSymbol *L, DebugLoc DL)
66        : Kind(K), Label(L), Loc(DL) {}
67  };
68
69  /// GCRoot - Metadata for a pointer to an object managed by the garbage
70  /// collector.
71  struct GCRoot {
72    int Num;            ///< Usually a frame index.
73    int StackOffset;    ///< Offset from the stack pointer.
74    const Constant *Metadata; ///< Metadata straight from the call
75                              ///< to llvm.gcroot.
76
77    GCRoot(int N, const Constant *MD) : Num(N), StackOffset(-1), Metadata(MD) {}
78  };
79
80
81  /// GCFunctionInfo - Garbage collection metadata for a single function.
82  ///
83  class GCFunctionInfo {
84  public:
85    typedef std::vector<GCPoint>::iterator iterator;
86    typedef std::vector<GCRoot>::iterator roots_iterator;
87    typedef std::vector<GCRoot>::const_iterator live_iterator;
88
89  private:
90    const Function &F;
91    GCStrategy &S;
92    uint64_t FrameSize;
93    std::vector<GCRoot> Roots;
94    std::vector<GCPoint> SafePoints;
95
96    // FIXME: Liveness. A 2D BitVector, perhaps?
97    //
98    //   BitVector Liveness;
99    //
100    //   bool islive(int point, int root) =
101    //     Liveness[point * SafePoints.size() + root]
102    //
103    // The bit vector is the more compact representation where >3.2% of roots
104    // are live per safe point (1.5% on 64-bit hosts).
105
106  public:
107    GCFunctionInfo(const Function &F, GCStrategy &S);
108    ~GCFunctionInfo();
109
110    /// getFunction - Return the function to which this metadata applies.
111    ///
112    const Function &getFunction() const { return F; }
113
114    /// getStrategy - Return the GC strategy for the function.
115    ///
116    GCStrategy &getStrategy() { return S; }
117
118    /// addStackRoot - Registers a root that lives on the stack. Num is the
119    ///                stack object ID for the alloca (if the code generator is
120    //                 using  MachineFrameInfo).
121    void addStackRoot(int Num, const Constant *Metadata) {
122      Roots.push_back(GCRoot(Num, Metadata));
123    }
124
125    /// addSafePoint - Notes the existence of a safe point. Num is the ID of the
126    /// label just prior to the safe point (if the code generator is using
127    /// MachineModuleInfo).
128    void addSafePoint(GC::PointKind Kind, MCSymbol *Label, DebugLoc DL) {
129      SafePoints.push_back(GCPoint(Kind, Label, DL));
130    }
131
132    /// getFrameSize/setFrameSize - Records the function's frame size.
133    ///
134    uint64_t getFrameSize() const { return FrameSize; }
135    void setFrameSize(uint64_t S) { FrameSize = S; }
136
137    /// begin/end - Iterators for safe points.
138    ///
139    iterator begin() { return SafePoints.begin(); }
140    iterator end()   { return SafePoints.end();   }
141    size_t size() const { return SafePoints.size(); }
142
143    /// roots_begin/roots_end - Iterators for all roots in the function.
144    ///
145    roots_iterator roots_begin() { return Roots.begin(); }
146    roots_iterator roots_end  () { return Roots.end();   }
147    size_t roots_size() const { return Roots.size(); }
148
149    /// live_begin/live_end - Iterators for live roots at a given safe point.
150    ///
151    live_iterator live_begin(const iterator &p) { return roots_begin(); }
152    live_iterator live_end  (const iterator &p) { return roots_end();   }
153    size_t live_size(const iterator &p) const { return roots_size(); }
154  };
155
156
157  /// GCModuleInfo - Garbage collection metadata for a whole module.
158  ///
159  class GCModuleInfo : public ImmutablePass {
160    typedef StringMap<GCStrategy*> strategy_map_type;
161    typedef std::vector<GCStrategy*> list_type;
162    typedef DenseMap<const Function*,GCFunctionInfo*> finfo_map_type;
163
164    strategy_map_type StrategyMap;
165    list_type StrategyList;
166    finfo_map_type FInfoMap;
167
168    GCStrategy *getOrCreateStrategy(const Module *M, const std::string &Name);
169
170  public:
171    typedef list_type::const_iterator iterator;
172
173    static char ID;
174
175    GCModuleInfo();
176    ~GCModuleInfo();
177
178    /// clear - Resets the pass. The metadata deleter pass calls this.
179    ///
180    void clear();
181
182    /// begin/end - Iterators for used strategies.
183    ///
184    iterator begin() const { return StrategyList.begin(); }
185    iterator end()   const { return StrategyList.end();   }
186
187    /// get - Look up function metadata.
188    ///
189    GCFunctionInfo &getFunctionInfo(const Function &F);
190  };
191
192}
193
194#endif
195