GCMetadata.h revision 207618
1//===-- GCMetadata.h - Garbage collector metadata -------------------------===// 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/Pass.h" 37#include "llvm/ADT/DenseMap.h" 38#include "llvm/ADT/StringMap.h" 39 40namespace llvm { 41 class AsmPrinter; 42 class GCStrategy; 43 class Constant; 44 class MCSymbol; 45 46 namespace GC { 47 /// PointKind - The type of a collector-safe point. 48 /// 49 enum PointKind { 50 Loop, //< Instr is a loop (backwards branch). 51 Return, //< Instr is a return instruction. 52 PreCall, //< Instr is a call instruction. 53 PostCall //< Instr is the return address of a call. 54 }; 55 } 56 57 /// GCPoint - Metadata for a collector-safe point in machine code. 58 /// 59 struct GCPoint { 60 GC::PointKind Kind; //< The kind of the safe point. 61 MCSymbol *Label; //< A label. 62 63 GCPoint(GC::PointKind K, MCSymbol *L) : Kind(K), Label(L) {} 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; //< Offset from the stack pointer. 71 const Constant *Metadata;//< Metadata straight from the call to llvm.gcroot. 72 73 GCRoot(int N, const Constant *MD) : Num(N), StackOffset(-1), Metadata(MD) {} 74 }; 75 76 77 /// GCFunctionInfo - Garbage collection metadata for a single function. 78 /// 79 class GCFunctionInfo { 80 public: 81 typedef std::vector<GCPoint>::iterator iterator; 82 typedef std::vector<GCRoot>::iterator roots_iterator; 83 typedef std::vector<GCRoot>::const_iterator live_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 /// 108 const Function &getFunction() const { return F; } 109 110 /// getStrategy - Return the GC strategy for the function. 111 /// 112 GCStrategy &getStrategy() { return S; } 113 114 /// addStackRoot - Registers a root that lives on the stack. Num is the 115 /// stack object ID for the alloca (if the code generator is 116 // using MachineFrameInfo). 117 void addStackRoot(int Num, const Constant *Metadata) { 118 Roots.push_back(GCRoot(Num, Metadata)); 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). 124 void addSafePoint(GC::PointKind Kind, MCSymbol *Label) { 125 SafePoints.push_back(GCPoint(Kind, Label)); 126 } 127 128 /// getFrameSize/setFrameSize - Records the function's frame size. 129 /// 130 uint64_t getFrameSize() const { return FrameSize; } 131 void setFrameSize(uint64_t S) { FrameSize = S; } 132 133 /// begin/end - Iterators for safe points. 134 /// 135 iterator begin() { return SafePoints.begin(); } 136 iterator end() { return SafePoints.end(); } 137 size_t size() const { return SafePoints.size(); } 138 139 /// roots_begin/roots_end - Iterators for all roots in the function. 140 /// 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 /// 147 live_iterator live_begin(const iterator &p) { return roots_begin(); } 148 live_iterator live_end (const iterator &p) { return roots_end(); } 149 size_t live_size(const iterator &p) const { return roots_size(); } 150 }; 151 152 153 /// GCModuleInfo - Garbage collection metadata for a whole module. 154 /// 155 class GCModuleInfo : public ImmutablePass { 156 typedef StringMap<GCStrategy*> strategy_map_type; 157 typedef std::vector<GCStrategy*> list_type; 158 typedef DenseMap<const Function*,GCFunctionInfo*> finfo_map_type; 159 160 strategy_map_type StrategyMap; 161 list_type StrategyList; 162 finfo_map_type FInfoMap; 163 164 GCStrategy *getOrCreateStrategy(const Module *M, const std::string &Name); 165 166 public: 167 typedef list_type::const_iterator iterator; 168 169 static char ID; 170 171 GCModuleInfo(); 172 ~GCModuleInfo(); 173 174 /// clear - Resets the pass. The metadata deleter pass calls this. 175 /// 176 void clear(); 177 178 /// begin/end - Iterators for used strategies. 179 /// 180 iterator begin() const { return StrategyList.begin(); } 181 iterator end() const { return StrategyList.end(); } 182 183 /// get - Look up function metadata. 184 /// 185 GCFunctionInfo &getFunctionInfo(const Function &F); 186 }; 187 188} 189 190#endif 191