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 45 namespace llvm { 46 class AsmPrinter; 47 class Constant; 48 class MCSymbol; 49 50 /// GCPoint - Metadata for a collector-safe point in machine code. 51 /// 52 struct GCPoint { 53 GC::PointKind Kind; ///< The kind of the safe point. 54 MCSymbol *Label; ///< A label. 55 DebugLoc Loc; 56 GCPointGCPoint57 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. 63 struct 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 GCRootGCRoot69 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. 74 class GCFunctionInfo { 75 public: 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 80 private: 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 97 public: 98 GCFunctionInfo(const Function &F, GCStrategy &S); 99 ~GCFunctionInfo(); 100 101 /// getFunction - Return the function to which this metadata applies. 102 /// getFunction()103 const Function &getFunction() const { return F; } 104 105 /// getStrategy - Return the GC strategy for the function. 106 /// getStrategy()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). addStackRoot(int Num,const Constant * Metadata)112 void addStackRoot(int Num, const Constant *Metadata) { 113 Roots.push_back(GCRoot(Num, Metadata)); 114 } 115 116 /// removeStackRoot - Removes a root. removeStackRoot(roots_iterator position)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). addSafePoint(GC::PointKind Kind,MCSymbol * Label,const DebugLoc & DL)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 /// getFrameSize()130 uint64_t getFrameSize() const { return FrameSize; } setFrameSize(uint64_t S)131 void setFrameSize(uint64_t S) { FrameSize = S; } 132 133 /// begin/end - Iterators for safe points. 134 /// begin()135 iterator begin() { return SafePoints.begin(); } end()136 iterator end() { return SafePoints.end(); } size()137 size_t size() const { return SafePoints.size(); } 138 139 /// roots_begin/roots_end - Iterators for all roots in the function. 140 /// roots_begin()141 roots_iterator roots_begin() { return Roots.begin(); } roots_end()142 roots_iterator roots_end() { return Roots.end(); } roots_size()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_begin(const iterator & p)147 live_iterator live_begin(const iterator &p) { return roots_begin(); } live_end(const iterator & p)148 live_iterator live_end(const iterator &p) { return roots_end(); } live_size(const iterator & p)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. 155 class 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; 160 161 public: 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 funcinfo_begin()171 FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); } funcinfo_end()172 FuncInfoVec::iterator funcinfo_end() { return Functions.end(); } 173 174 private: 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; 182 183 public: 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 /// begin()197 iterator begin() const { return GCStrategyList.begin(); } end()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