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 MCSymbol *Label; ///< A label.
61 GCPoint(MCSymbol *L, DebugLoc DL)
62 : Label(L), Loc(std::move(DL)) {}
65 /// GCRoot - Metadata for a pointer to an object managed by the garbage
68 int Num; ///< Usually a frame index.
69 int StackOffset = -1; ///< Offset from the stack pointer.
70 const Constant *Metadata; ///< Metadata straight from the call
73 GCRoot(int N, const Constant *MD) : Num(N), Metadata(MD) {}
76 /// Garbage collection metadata for a single function. Currently, this
77 /// information only applies to GCStrategies which use GCRoot.
78 class GCFunctionInfo {
80 using iterator = std::vector<GCPoint>::iterator;
81 using roots_iterator = std::vector<GCRoot>::iterator;
82 using live_iterator = std::vector<GCRoot>::const_iterator;
88 std::vector<GCRoot> Roots;
89 std::vector<GCPoint> SafePoints;
91 // FIXME: Liveness. A 2D BitVector, perhaps?
93 // BitVector Liveness;
95 // bool islive(int point, int root) =
96 // Liveness[point * SafePoints.size() + root]
98 // The bit vector is the more compact representation where >3.2% of roots
99 // are live per safe point (1.5% on 64-bit hosts).
102 GCFunctionInfo(const Function &F, GCStrategy &S);
105 /// getFunction - Return the function to which this metadata applies.
106 const Function &getFunction() const { return F; }
108 /// getStrategy - Return the GC strategy for the function.
109 GCStrategy &getStrategy() { return S; }
111 /// addStackRoot - Registers a root that lives on the stack. Num is the
112 /// stack object ID for the alloca (if the code generator is
113 // using MachineFrameInfo).
114 void addStackRoot(int Num, const Constant *Metadata) {
115 Roots.push_back(GCRoot(Num, Metadata));
118 /// removeStackRoot - Removes a root.
119 roots_iterator removeStackRoot(roots_iterator position) {
120 return Roots.erase(position);
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(MCSymbol *Label, const DebugLoc &DL) {
127 SafePoints.emplace_back(Label, DL);
130 /// getFrameSize/setFrameSize - Records the function's frame size.
131 uint64_t getFrameSize() const { return FrameSize; }
132 void setFrameSize(uint64_t S) { FrameSize = S; }
134 /// begin/end - Iterators for safe points.
135 iterator begin() { return SafePoints.begin(); }
136 iterator end() { return SafePoints.end(); }
137 size_t size() const { return SafePoints.size(); }
139 /// roots_begin/roots_end - Iterators for all roots in the function.
140 roots_iterator roots_begin() { return Roots.begin(); }
141 roots_iterator roots_end() { return Roots.end(); }
142 size_t roots_size() const { return Roots.size(); }
144 /// live_begin/live_end - Iterators for live roots at a given safe point.
145 live_iterator live_begin(const iterator &p) { return roots_begin(); }
146 live_iterator live_end(const iterator &p) { return roots_end(); }
147 size_t live_size(const iterator &p) const { return roots_size(); }
150 /// An analysis pass which caches information about the entire Module.
151 /// Records both the function level information used by GCRoots and a
152 /// cache of the 'active' gc strategy objects for the current Module.
153 class GCModuleInfo : public ImmutablePass {
154 /// An owning list of all GCStrategies which have been created
155 SmallVector<std::unique_ptr<GCStrategy>, 1> GCStrategyList;
156 /// A helper map to speedup lookups into the above list
157 StringMap<GCStrategy*> GCStrategyMap;
160 /// Lookup the GCStrategy object associated with the given gc name.
161 /// Objects are owned internally; No caller should attempt to delete the
162 /// returned objects.
163 GCStrategy *getGCStrategy(const StringRef Name);
165 /// List of per function info objects. In theory, Each of these
166 /// may be associated with a different GC.
167 using FuncInfoVec = std::vector<std::unique_ptr<GCFunctionInfo>>;
169 FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); }
170 FuncInfoVec::iterator funcinfo_end() { return Functions.end(); }
173 /// Owning list of all GCFunctionInfos associated with this Module
174 FuncInfoVec Functions;
176 /// Non-owning map to bypass linear search when finding the GCFunctionInfo
177 /// associated with a particular Function.
178 using finfo_map_type = DenseMap<const Function *, GCFunctionInfo *>;
179 finfo_map_type FInfoMap;
182 using iterator = SmallVector<std::unique_ptr<GCStrategy>, 1>::const_iterator;
188 /// clear - Resets the pass. Any pass, which uses GCModuleInfo, should
189 /// call it in doFinalization().
193 /// begin/end - Iterators for used strategies.
195 iterator begin() const { return GCStrategyList.begin(); }
196 iterator end() const { return GCStrategyList.end(); }
198 /// get - Look up function metadata. This is currently assumed
199 /// have the side effect of initializing the associated GCStrategy. That
200 /// will soon change.
201 GCFunctionInfo &getFunctionInfo(const Function &F);
204 } // end namespace llvm
206 #endif // LLVM_CODEGEN_GCMETADATA_H