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/ADT/StringRef.h" 40 #include "llvm/CodeGen/GCStrategy.h" 41 #include "llvm/IR/DebugLoc.h" 42 #include "llvm/Pass.h" 43 #include <algorithm> 44 #include <cstddef> 45 #include <cstdint> 46 #include <memory> 47 #include <vector> 48 49 namespace llvm { 50 51 class Constant; 52 class Function; 53 class MCSymbol; 54 55 /// GCPoint - Metadata for a collector-safe point in machine code. 56 /// 57 struct GCPoint { 58 GC::PointKind Kind; ///< The kind of the safe point. 59 MCSymbol *Label; ///< A label. 60 DebugLoc Loc; 61 62 GCPoint(GC::PointKind K, MCSymbol *L, DebugLoc DL) 63 : Kind(K), Label(L), Loc(std::move(DL)) {} 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 = -1; ///< Offset from the stack pointer. 71 const Constant *Metadata; ///< Metadata straight from the call 72 ///< to llvm.gcroot. 73 74 GCRoot(int N, const Constant *MD) : Num(N), Metadata(MD) {} 75 }; 76 77 /// Garbage collection metadata for a single function. Currently, this 78 /// information only applies to GCStrategies which use GCRoot. 79 class GCFunctionInfo { 80 public: 81 using iterator = std::vector<GCPoint>::iterator; 82 using roots_iterator = std::vector<GCRoot>::iterator; 83 using live_iterator = std::vector<GCRoot>::const_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 const Function &getFunction() const { return F; } 108 109 /// getStrategy - Return the GC strategy for the function. 110 GCStrategy &getStrategy() { return S; } 111 112 /// 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)); 117 } 118 119 /// removeStackRoot - Removes a root. 120 roots_iterator removeStackRoot(roots_iterator position) { 121 return Roots.erase(position); 122 } 123 124 /// 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); 129 } 130 131 /// getFrameSize/setFrameSize - Records the function's frame size. 132 uint64_t getFrameSize() const { return FrameSize; } 133 void setFrameSize(uint64_t S) { FrameSize = S; } 134 135 /// 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(); } 139 140 /// 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(); } 144 145 /// 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(); } 149 }; 150 151 /// 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; 159 160 public: 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); 165 166 /// 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>>; 169 170 FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); } 171 FuncInfoVec::iterator funcinfo_end() { return Functions.end(); } 172 173 private: 174 /// Owning list of all GCFunctionInfos associated with this Module 175 FuncInfoVec Functions; 176 177 /// 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; 181 182 public: 183 using iterator = SmallVector<std::unique_ptr<GCStrategy>, 1>::const_iterator; 184 185 static char ID; 186 187 GCModuleInfo(); 188 189 /// clear - Resets the pass. Any pass, which uses GCModuleInfo, should 190 /// call it in doFinalization(). 191 /// 192 void clear(); 193 194 /// begin/end - Iterators for used strategies. 195 /// 196 iterator begin() const { return GCStrategyList.begin(); } 197 iterator end() const { return GCStrategyList.end(); } 198 199 /// 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); 203 }; 204 205 } // end namespace llvm 206 207 #endif // LLVM_CODEGEN_GCMETADATA_H 208
