1 //===- GCMetadata.h - Garbage collector metadata ----------------*- 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 // 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/ADT/DenseMap.h"
37 #include "llvm/ADT/SmallVector.h"
38 #include "llvm/ADT/StringMap.h"
39 #include "llvm/ADT/StringRef.h"
40 #include "llvm/CodeGen/GCStrategy.h"
41 #include "llvm/IR/DebugLoc.h"
42 #include "llvm/Pass.h"
55 /// GCPoint - Metadata for a collector-safe point in machine code.
58 GC::PointKind Kind; ///< The kind of the safe point.
59 MCSymbol *Label; ///< A label.
62 GCPoint(GC::PointKind K, MCSymbol *L, DebugLoc DL)
63 : Kind(K), Label(L), Loc(std::move(DL)) {}
66 /// GCRoot - Metadata for a pointer to an object managed by the garbage
69 int Num; ///< Usually a frame index.
70 int StackOffset = -1; ///< Offset from the stack pointer.
71 const Constant *Metadata; ///< Metadata straight from the call
74 GCRoot(int N, const Constant *MD) : Num(N), Metadata(MD) {}
77 /// Garbage collection metadata for a single function. Currently, this
78 /// information only applies to GCStrategies which use GCRoot.
79 class GCFunctionInfo {
81 using iterator = std::vector<GCPoint>::iterator;
82 using roots_iterator = std::vector<GCRoot>::iterator;
83 using live_iterator = std::vector<GCRoot>::const_iterator;
89 std::vector<GCRoot> Roots;
90 std::vector<GCPoint> SafePoints;
92 // FIXME: Liveness. A 2D BitVector, perhaps?
94 // BitVector Liveness;
96 // bool islive(int point, int root) =
97 // Liveness[point * SafePoints.size() + root]
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).
103 GCFunctionInfo(const Function &F, GCStrategy &S);
106 /// getFunction - Return the function to which this metadata applies.
107 const Function &getFunction() const { return F; }
109 /// getStrategy - Return the GC strategy for the function.
110 GCStrategy &getStrategy() { return S; }
112 /// addStackRoot - Registers a root that lives on the stack. Num is the
113 /// stack object ID for the alloca (if the code generator is
114 // using MachineFrameInfo).
115 void addStackRoot(int Num, const Constant *Metadata) {
116 Roots.push_back(GCRoot(Num, Metadata));
119 /// removeStackRoot - Removes a root.
120 roots_iterator removeStackRoot(roots_iterator position) {
121 return Roots.erase(position);
124 /// addSafePoint - Notes the existence of a safe point. Num is the ID of the
125 /// label just prior to the safe point (if the code generator is using
126 /// MachineModuleInfo).
127 void addSafePoint(GC::PointKind Kind, MCSymbol *Label, const DebugLoc &DL) {
128 SafePoints.emplace_back(Kind, Label, DL);
131 /// 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.
136 iterator begin() { return SafePoints.begin(); }
137 iterator end() { return SafePoints.end(); }
138 size_t size() const { return SafePoints.size(); }
140 /// roots_begin/roots_end - Iterators for all roots in the function.
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(); }
145 /// live_begin/live_end - Iterators for live roots at a given safe point.
146 live_iterator live_begin(const iterator &p) { return roots_begin(); }
147 live_iterator live_end(const iterator &p) { return roots_end(); }
148 size_t live_size(const iterator &p) const { return roots_size(); }
151 /// An analysis pass which caches information about the entire Module.
152 /// Records both the function level information used by GCRoots and a
153 /// cache of the 'active' gc strategy objects for the current Module.
154 class GCModuleInfo : public ImmutablePass {
155 /// An owning list of all GCStrategies which have been created
156 SmallVector<std::unique_ptr<GCStrategy>, 1> GCStrategyList;
157 /// A helper map to speedup lookups into the above list
158 StringMap<GCStrategy*> GCStrategyMap;
161 /// Lookup the GCStrategy object associated with the given gc name.
162 /// Objects are owned internally; No caller should attempt to delete the
163 /// returned objects.
164 GCStrategy *getGCStrategy(const StringRef Name);
166 /// List of per function info objects. In theory, Each of these
167 /// may be associated with a different GC.
168 using FuncInfoVec = std::vector<std::unique_ptr<GCFunctionInfo>>;
170 FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); }
171 FuncInfoVec::iterator funcinfo_end() { return Functions.end(); }
174 /// Owning list of all GCFunctionInfos associated with this Module
175 FuncInfoVec Functions;
177 /// Non-owning map to bypass linear search when finding the GCFunctionInfo
178 /// associated with a particular Function.
179 using finfo_map_type = DenseMap<const Function *, GCFunctionInfo *>;
180 finfo_map_type FInfoMap;
183 using iterator = SmallVector<std::unique_ptr<GCStrategy>, 1>::const_iterator;
189 /// clear - Resets the pass. Any pass, which uses GCModuleInfo, should
190 /// call it in doFinalization().
194 /// begin/end - Iterators for used strategies.
196 iterator begin() const { return GCStrategyList.begin(); }
197 iterator end() const { return GCStrategyList.end(); }
199 /// get - Look up function metadata. This is currently assumed
200 /// have the side effect of initializing the associated GCStrategy. That
201 /// will soon change.
202 GCFunctionInfo &getFunctionInfo(const Function &F);
205 } // end namespace llvm
207 #endif // LLVM_CODEGEN_GCMETADATA_H