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/Pass.h" 42 #include <algorithm> 43 #include <cstddef> 44 #include <cstdint> 45 #include <memory> 46 #include <vector> 47 48 namespace llvm { 49 50 class Constant; 51 class Function; 52 class MCSymbol; 53 54 /// GCPoint - Metadata for a collector-safe point in machine code. 55 /// 56 struct GCPoint { 57 MCSymbol *Label; ///< A label. 58 DebugLoc Loc; 59 60 GCPoint(MCSymbol *L, DebugLoc DL) 61 : Label(L), Loc(std::move(DL)) {} 62 }; 63 64 /// GCRoot - Metadata for a pointer to an object managed by the garbage 65 /// collector. 66 struct GCRoot { 67 int Num; ///< Usually a frame index. 68 int StackOffset = -1; ///< Offset from the stack pointer. 69 const Constant *Metadata; ///< Metadata straight from the call 70 ///< to llvm.gcroot. 71 72 GCRoot(int N, const Constant *MD) : Num(N), Metadata(MD) {} 73 }; 74 75 /// Garbage collection metadata for a single function. Currently, this 76 /// information only applies to GCStrategies which use GCRoot. 77 class GCFunctionInfo { 78 public: 79 using iterator = std::vector<GCPoint>::iterator; 80 using roots_iterator = std::vector<GCRoot>::iterator; 81 using live_iterator = std::vector<GCRoot>::const_iterator; 82 83 private: 84 const Function &F; 85 GCStrategy &S; 86 uint64_t FrameSize; 87 std::vector<GCRoot> Roots; 88 std::vector<GCPoint> SafePoints; 89 90 // FIXME: Liveness. A 2D BitVector, perhaps? 91 // 92 // BitVector Liveness; 93 // 94 // bool islive(int point, int root) = 95 // Liveness[point * SafePoints.size() + root] 96 // 97 // The bit vector is the more compact representation where >3.2% of roots 98 // are live per safe point (1.5% on 64-bit hosts). 99 100 public: 101 GCFunctionInfo(const Function &F, GCStrategy &S); 102 ~GCFunctionInfo(); 103 104 /// getFunction - Return the function to which this metadata applies. 105 const Function &getFunction() const { return F; } 106 107 /// getStrategy - Return the GC strategy for the function. 108 GCStrategy &getStrategy() { return S; } 109 110 /// addStackRoot - Registers a root that lives on the stack. Num is the 111 /// stack object ID for the alloca (if the code generator is 112 // using MachineFrameInfo). 113 void addStackRoot(int Num, const Constant *Metadata) { 114 Roots.push_back(GCRoot(Num, Metadata)); 115 } 116 117 /// removeStackRoot - Removes a root. 118 roots_iterator removeStackRoot(roots_iterator position) { 119 return Roots.erase(position); 120 } 121 122 /// addSafePoint - Notes the existence of a safe point. Num is the ID of the 123 /// label just prior to the safe point (if the code generator is using 124 /// MachineModuleInfo). 125 void addSafePoint(MCSymbol *Label, const DebugLoc &DL) { 126 SafePoints.emplace_back(Label, DL); 127 } 128 129 /// getFrameSize/setFrameSize - Records the function's frame size. 130 uint64_t getFrameSize() const { return FrameSize; } 131 void setFrameSize(uint64_t S) { FrameSize = S; } 132 133 /// begin/end - Iterators for safe points. 134 iterator begin() { return SafePoints.begin(); } 135 iterator end() { return SafePoints.end(); } 136 size_t size() const { return SafePoints.size(); } 137 138 /// roots_begin/roots_end - Iterators for all roots in the function. 139 roots_iterator roots_begin() { return Roots.begin(); } 140 roots_iterator roots_end() { return Roots.end(); } 141 size_t roots_size() const { return Roots.size(); } 142 143 /// live_begin/live_end - Iterators for live roots at a given safe point. 144 live_iterator live_begin(const iterator &p) { return roots_begin(); } 145 live_iterator live_end(const iterator &p) { return roots_end(); } 146 size_t live_size(const iterator &p) const { return roots_size(); } 147 }; 148 149 /// An analysis pass which caches information about the entire Module. 150 /// Records both the function level information used by GCRoots and a 151 /// cache of the 'active' gc strategy objects for the current Module. 152 class GCModuleInfo : public ImmutablePass { 153 /// An owning list of all GCStrategies which have been created 154 SmallVector<std::unique_ptr<GCStrategy>, 1> GCStrategyList; 155 /// A helper map to speedup lookups into the above list 156 StringMap<GCStrategy*> GCStrategyMap; 157 158 public: 159 /// Lookup the GCStrategy object associated with the given gc name. 160 /// Objects are owned internally; No caller should attempt to delete the 161 /// returned objects. 162 GCStrategy *getGCStrategy(const StringRef Name); 163 164 /// List of per function info objects. In theory, Each of these 165 /// may be associated with a different GC. 166 using FuncInfoVec = std::vector<std::unique_ptr<GCFunctionInfo>>; 167 168 FuncInfoVec::iterator funcinfo_begin() { return Functions.begin(); } 169 FuncInfoVec::iterator funcinfo_end() { return Functions.end(); } 170 171 private: 172 /// Owning list of all GCFunctionInfos associated with this Module 173 FuncInfoVec Functions; 174 175 /// Non-owning map to bypass linear search when finding the GCFunctionInfo 176 /// associated with a particular Function. 177 using finfo_map_type = DenseMap<const Function *, GCFunctionInfo *>; 178 finfo_map_type FInfoMap; 179 180 public: 181 using iterator = SmallVector<std::unique_ptr<GCStrategy>, 1>::const_iterator; 182 183 static char ID; 184 185 GCModuleInfo(); 186 187 /// clear - Resets the pass. Any pass, which uses GCModuleInfo, should 188 /// call it in doFinalization(). 189 /// 190 void clear(); 191 192 /// begin/end - Iterators for used strategies. 193 /// 194 iterator begin() const { return GCStrategyList.begin(); } 195 iterator end() const { return GCStrategyList.end(); } 196 197 /// get - Look up function metadata. This is currently assumed 198 /// have the side effect of initializing the associated GCStrategy. That 199 /// will soon change. 200 GCFunctionInfo &getFunctionInfo(const Function &F); 201 }; 202 203 } // end namespace llvm 204 205 #endif // LLVM_CODEGEN_GCMETADATA_H 206
Indexes created Tue Jun 09 00:24:00 UTC 2026