1 //===- GCMetadata.h - Garbage collector metadata ----------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file declares the GCFunctionInfo and GCModuleInfo classes, which are 10 // used as a communication channel from the target code generator to the target 11 // garbage collectors. This interface allows code generators and garbage 12 // collectors to be developed independently. 13 // 14 // The GCFunctionInfo class logs the data necessary to build a type accurate 15 // stack map. The code generator outputs: 16 // 17 // - Safe points as specified by the GCStrategy's NeededSafePoints. 18 // - Stack offsets for GC roots, as specified by calls to llvm.gcroot 19 // 20 // As a refinement, liveness analysis calculates the set of live roots at each 21 // safe point. Liveness analysis is not presently performed by the code 22 // generator, so all roots are assumed live. 23 // 24 // GCModuleInfo simply collects GCFunctionInfo instances for each Function as 25 // they are compiled. This accretion is necessary for collectors which must emit 26 // a stack map for the compilation unit as a whole. Therefore, GCFunctionInfo 27 // outlives the MachineFunction from which it is derived and must not refer to 28 // any code generator data structures. 29 // 30 //===----------------------------------------------------------------------===// 31 32 #ifndef LLVM_CODEGEN_GCMETADATA_H 33 #define LLVM_CODEGEN_GCMETADATA_H 34 35 #include "llvm/ADT/DenseMap.h" 36 #include "llvm/ADT/SmallVector.h" 37 #include "llvm/ADT/StringMap.h" 38 #include "llvm/ADT/StringRef.h" 39 #include "llvm/IR/DebugLoc.h" 40 #include "llvm/IR/GCStrategy.h" 41 #include "llvm/IR/PassManager.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 MCSymbol *Label; ///< A label. 59 DebugLoc Loc; 60 61 GCPoint(MCSymbol *L, DebugLoc DL) 62 : Label(L), Loc(std::move(DL)) {} 63 }; 64 65 /// GCRoot - Metadata for a pointer to an object managed by the garbage 66 /// collector. 67 struct GCRoot { 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 71 ///< to llvm.gcroot. 72 73 GCRoot(int N, const Constant *MD) : Num(N), Metadata(MD) {} 74 }; 75 76 /// Garbage collection metadata for a single function. Currently, this 77 /// information only applies to GCStrategies which use GCRoot. 78 class GCFunctionInfo { 79 public: 80 using iterator = std::vector<GCPoint>::iterator; 81 using roots_iterator = std::vector<GCRoot>::iterator; 82 using live_iterator = std::vector<GCRoot>::const_iterator; 83 84 private: 85 const Function &F; 86 GCStrategy &S; 87 uint64_t FrameSize; 88 std::vector<GCRoot> Roots; 89 std::vector<GCPoint> SafePoints; 90 91 // FIXME: Liveness. A 2D BitVector, perhaps? 92 // 93 // BitVector Liveness; 94 // 95 // bool islive(int point, int root) = 96 // Liveness[point * SafePoints.size() + root] 97 // 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). 100 101 public: 102 GCFunctionInfo(const Function &F, GCStrategy &S); 103 ~GCFunctionInfo(); 104 105 /// Handle invalidation explicitly. 106 bool invalidate(Function &F, const PreservedAnalyses &PA, 107 FunctionAnalysisManager::Invalidator &Inv); 108 109 /// getFunction - Return the function to which this metadata applies. 110 const Function &getFunction() const { return F; } 111 112 /// getStrategy - Return the GC strategy for the function. 113 GCStrategy &getStrategy() { return S; } 114 115 /// addStackRoot - Registers a root that lives on the stack. Num is the 116 /// stack object ID for the alloca (if the code generator is 117 // using MachineFrameInfo). 118 void addStackRoot(int Num, const Constant *Metadata) { 119 Roots.push_back(GCRoot(Num, Metadata)); 120 } 121 122 /// removeStackRoot - Removes a root. 123 roots_iterator removeStackRoot(roots_iterator position) { 124 return Roots.erase(position); 125 } 126 127 /// addSafePoint - Notes the existence of a safe point. Num is the ID of the 128 /// label just prior to the safe point (if the code generator is using 129 /// MachineModuleInfo). 130 void addSafePoint(MCSymbol *Label, const DebugLoc &DL) { 131 SafePoints.emplace_back(Label, DL); 132 } 133 134 /// getFrameSize/setFrameSize - Records the function's frame size. 135 uint64_t getFrameSize() const { return FrameSize; } 136 void setFrameSize(uint64_t S) { FrameSize = S; } 137 138 /// begin/end - Iterators for safe points. 139 iterator begin() { return SafePoints.begin(); } 140 iterator end() { return SafePoints.end(); } 141 size_t size() const { return SafePoints.size(); } 142 143 /// roots_begin/roots_end - Iterators for all roots in the function. 144 roots_iterator roots_begin() { return Roots.begin(); } 145 roots_iterator roots_end() { return Roots.end(); } 146 size_t roots_size() const { return Roots.size(); } 147 148 /// live_begin/live_end - Iterators for live roots at a given safe point. 149 live_iterator live_begin(const iterator &p) { return roots_begin(); } 150 live_iterator live_end(const iterator &p) { return roots_end(); } 151 size_t live_size(const iterator &p) const { return roots_size(); } 152 }; 153 154 struct GCStrategyMap { 155 StringMap<std::unique_ptr<GCStrategy>> StrategyMap; 156 157 GCStrategyMap() = default; 158 GCStrategyMap(GCStrategyMap &&) = default; 159 160 /// Handle invalidation explicitly. 161 bool invalidate(Module &M, const PreservedAnalyses &PA, 162 ModuleAnalysisManager::Invalidator &Inv); 163 }; 164 165 /// An analysis pass which caches information about the entire Module. 166 /// Records a cache of the 'active' gc strategy objects for the current Module. 167 class CollectorMetadataAnalysis 168 : public AnalysisInfoMixin<CollectorMetadataAnalysis> { 169 friend struct AnalysisInfoMixin<CollectorMetadataAnalysis>; 170 static AnalysisKey Key; 171 172 public: 173 using Result = GCStrategyMap; 174 Result run(Module &M, ModuleAnalysisManager &MAM); 175 }; 176 177 /// An analysis pass which caches information about the Function. 178 /// Records the function level information used by GCRoots. 179 /// This pass depends on `CollectorMetadataAnalysis`. 180 class GCFunctionAnalysis : public AnalysisInfoMixin<GCFunctionAnalysis> { 181 friend struct AnalysisInfoMixin<GCFunctionAnalysis>; 182 static AnalysisKey Key; 183 184 public: 185 using Result = GCFunctionInfo; 186 Result run(Function &F, FunctionAnalysisManager &FAM); 187 }; 188 189 /// LowerIntrinsics - This pass rewrites calls to the llvm.gcread or 190 /// llvm.gcwrite intrinsics, replacing them with simple loads and stores as 191 /// directed by the GCStrategy. It also performs automatic root initialization 192 /// and custom intrinsic lowering. 193 /// 194 /// This pass requires `CollectorMetadataAnalysis`. 195 class GCLoweringPass : public PassInfoMixin<GCLoweringPass> { 196 public: 197 PreservedAnalyses run(Function &F, FunctionAnalysisManager &FAM); 198 }; 199 200 /// An analysis pass which caches information about the entire Module. 201 /// Records both the function level information used by GCRoots and a 202 /// cache of the 'active' gc strategy objects for the current Module. 203 class GCModuleInfo : public ImmutablePass { 204 /// An owning list of all GCStrategies which have been created 205 SmallVector<std::unique_ptr<GCStrategy>, 1> GCStrategyList; 206 /// A helper map to speedup lookups into the above list 207 StringMap<GCStrategy*> GCStrategyMap; 208 209 public: 210 /// Lookup the GCStrategy object associated with the given gc name. 211 /// Objects are owned internally; No caller should attempt to delete the 212 /// returned objects. 213 GCStrategy *getGCStrategy(const StringRef Name); 214 215 /// List of per function info objects. In theory, Each of these 216 /// may be associated with a different GC. 217 using FuncInfoVec = std::vector<std::unique_ptr<GCFunctionInfo>>; 218 219 FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); } 220 FuncInfoVec::iterator funcinfo_end() { return Functions.end(); } 221 222 private: 223 /// Owning list of all GCFunctionInfos associated with this Module 224 FuncInfoVec Functions; 225 226 /// Non-owning map to bypass linear search when finding the GCFunctionInfo 227 /// associated with a particular Function. 228 using finfo_map_type = DenseMap<const Function *, GCFunctionInfo *>; 229 finfo_map_type FInfoMap; 230 231 public: 232 using iterator = SmallVector<std::unique_ptr<GCStrategy>, 1>::const_iterator; 233 234 static char ID; 235 236 GCModuleInfo(); 237 238 /// clear - Resets the pass. Any pass, which uses GCModuleInfo, should 239 /// call it in doFinalization(). 240 /// 241 void clear(); 242 243 /// begin/end - Iterators for used strategies. 244 /// 245 iterator begin() const { return GCStrategyList.begin(); } 246 iterator end() const { return GCStrategyList.end(); } 247 248 /// get - Look up function metadata. This is currently assumed 249 /// have the side effect of initializing the associated GCStrategy. That 250 /// will soon change. 251 GCFunctionInfo &getFunctionInfo(const Function &F); 252 }; 253 254 } // end namespace llvm 255 256 #endif // LLVM_CODEGEN_GCMETADATA_H 257