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/ADT/DenseMap.h"
37#include "llvm/ADT/SmallVector.h"
38#include "llvm/ADT/StringMap.h"
39#include "llvm/CodeGen/GCStrategy.h"
40#include "llvm/IR/DebugLoc.h"
41#include "llvm/Pass.h"
42#include <memory>
43#include <utility>
44
45namespace llvm {
46class AsmPrinter;
47class Constant;
48class MCSymbol;
49
50/// GCPoint - Metadata for a collector-safe point in machine code.
51///
52struct GCPoint {
53  GC::PointKind Kind; ///< The kind of the safe point.
54  MCSymbol *Label;    ///< A label.
55  DebugLoc Loc;
56
57  GCPoint(GC::PointKind K, MCSymbol *L, DebugLoc DL)
58      : Kind(K), Label(L), Loc(std::move(DL)) {}
59};
60
61/// GCRoot - Metadata for a pointer to an object managed by the garbage
62/// collector.
63struct GCRoot {
64  int Num;                  ///< Usually a frame index.
65  int StackOffset;          ///< Offset from the stack pointer.
66  const Constant *Metadata; ///< Metadata straight from the call
67                            ///< to llvm.gcroot.
68
69  GCRoot(int N, const Constant *MD) : Num(N), StackOffset(-1), Metadata(MD) {}
70};
71
72/// Garbage collection metadata for a single function.  Currently, this
73/// information only applies to GCStrategies which use GCRoot.
74class GCFunctionInfo {
75public:
76  typedef std::vector<GCPoint>::iterator iterator;
77  typedef std::vector<GCRoot>::iterator roots_iterator;
78  typedef std::vector<GCRoot>::const_iterator live_iterator;
79
80private:
81  const Function &F;
82  GCStrategy &S;
83  uint64_t FrameSize;
84  std::vector<GCRoot> Roots;
85  std::vector<GCPoint> SafePoints;
86
87  // FIXME: Liveness. A 2D BitVector, perhaps?
88  //
89  //   BitVector Liveness;
90  //
91  //   bool islive(int point, int root) =
92  //     Liveness[point * SafePoints.size() + root]
93  //
94  // The bit vector is the more compact representation where >3.2% of roots
95  // are live per safe point (1.5% on 64-bit hosts).
96
97public:
98  GCFunctionInfo(const Function &F, GCStrategy &S);
99  ~GCFunctionInfo();
100
101  /// getFunction - Return the function to which this metadata applies.
102  ///
103  const Function &getFunction() const { return F; }
104
105  /// getStrategy - Return the GC strategy for the function.
106  ///
107  GCStrategy &getStrategy() { return S; }
108
109  /// addStackRoot - Registers a root that lives on the stack. Num is the
110  ///                stack object ID for the alloca (if the code generator is
111  //                 using  MachineFrameInfo).
112  void addStackRoot(int Num, const Constant *Metadata) {
113    Roots.push_back(GCRoot(Num, Metadata));
114  }
115
116  /// removeStackRoot - Removes a root.
117  roots_iterator removeStackRoot(roots_iterator position) {
118    return Roots.erase(position);
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, const DebugLoc &DL) {
125    SafePoints.emplace_back(Kind, Label, DL);
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/// An analysis pass which caches information about the entire Module.
153/// Records both the function level information used by GCRoots and a
154/// cache of the 'active' gc strategy objects for the current Module.
155class GCModuleInfo : public ImmutablePass {
156  /// An owning list of all GCStrategies which have been created
157  SmallVector<std::unique_ptr<GCStrategy>, 1> GCStrategyList;
158  /// A helper map to speedup lookups into the above list
159  StringMap<GCStrategy*> GCStrategyMap;
160
161public:
162  /// Lookup the GCStrategy object associated with the given gc name.
163  /// Objects are owned internally; No caller should attempt to delete the
164  /// returned objects.
165  GCStrategy *getGCStrategy(const StringRef Name);
166
167  /// List of per function info objects.  In theory, Each of these
168  /// may be associated with a different GC.
169  typedef std::vector<std::unique_ptr<GCFunctionInfo>> FuncInfoVec;
170
171  FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); }
172  FuncInfoVec::iterator funcinfo_end() { return Functions.end(); }
173
174private:
175  /// Owning list of all GCFunctionInfos associated with this Module
176  FuncInfoVec Functions;
177
178  /// Non-owning map to bypass linear search when finding the GCFunctionInfo
179  /// associated with a particular Function.
180  typedef DenseMap<const Function *, GCFunctionInfo *> finfo_map_type;
181  finfo_map_type FInfoMap;
182
183public:
184  typedef SmallVector<std::unique_ptr<GCStrategy>,1>::const_iterator iterator;
185
186  static char ID;
187
188  GCModuleInfo();
189
190  /// clear - Resets the pass. Any pass, which uses GCModuleInfo, should
191  /// call it in doFinalization().
192  ///
193  void clear();
194
195  /// begin/end - Iterators for used strategies.
196  ///
197  iterator begin() const { return GCStrategyList.begin(); }
198  iterator end() const { return GCStrategyList.end(); }
199
200  /// get - Look up function metadata.  This is currently assumed
201  /// have the side effect of initializing the associated GCStrategy.  That
202  /// will soon change.
203  GCFunctionInfo &getFunctionInfo(const Function &F);
204};
205}
206
207#endif
208