1 //===-- EHStreamer.h - Exception Handling Directive Streamer ---*- 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 contains support for writing exception info into assembly files. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_CODEGEN_ASMPRINTER_EHSTREAMER_H 15 #define LLVM_CODEGEN_ASMPRINTER_EHSTREAMER_H 16 17 #include "AsmPrinterHandler.h" 18 #include "llvm/ADT/DenseMap.h" 19 20 namespace llvm { 21 struct LandingPadInfo; 22 class MachineModuleInfo; 23 class MachineInstr; 24 class MachineFunction; 25 class AsmPrinter; 26 27 template <typename T> 28 class SmallVectorImpl; 29 30 /// Emits exception handling directives. 31 class EHStreamer : public AsmPrinterHandler { 32 protected: 33 /// Target of directive emission. 34 AsmPrinter *Asm; 35 36 /// Collected machine module information. 37 MachineModuleInfo *MMI; 38 39 /// How many leading type ids two landing pads have in common. 40 static unsigned sharedTypeIDs(const LandingPadInfo *L, 41 const LandingPadInfo *R); 42 43 /// Structure holding a try-range and the associated landing pad. 44 struct PadRange { 45 // The index of the landing pad. 46 unsigned PadIndex; 47 // The index of the begin and end labels in the landing pad's label lists. 48 unsigned RangeIndex; 49 }; 50 51 typedef DenseMap<MCSymbol *, PadRange> RangeMapType; 52 53 /// Structure describing an entry in the actions table. 54 struct ActionEntry { 55 int ValueForTypeID; // The value to write - may not be equal to the type id. 56 int NextAction; 57 unsigned Previous; 58 }; 59 60 /// Structure describing an entry in the call-site table. 61 struct CallSiteEntry { 62 // The 'try-range' is BeginLabel .. EndLabel. 63 MCSymbol *BeginLabel; // zero indicates the start of the function. 64 MCSymbol *EndLabel; // zero indicates the end of the function. 65 66 // The landing pad starts at PadLabel. 67 MCSymbol *PadLabel; // zero indicates that there is no landing pad. 68 unsigned Action; 69 }; 70 71 /// Compute the actions table and gather the first action index for each 72 /// landing pad site. 73 unsigned computeActionsTable(const SmallVectorImpl<const LandingPadInfo*>&LPs, 74 SmallVectorImpl<ActionEntry> &Actions, 75 SmallVectorImpl<unsigned> &FirstActions); 76 77 /// Return `true' if this is a call to a function marked `nounwind'. Return 78 /// `false' otherwise. 79 bool callToNoUnwindFunction(const MachineInstr *MI); 80 81 /// Compute the call-site table. The entry for an invoke has a try-range 82 /// containing the call, a non-zero landing pad and an appropriate action. 83 /// The entry for an ordinary call has a try-range containing the call and 84 /// zero for the landing pad and the action. Calls marked 'nounwind' have 85 /// no entry and must not be contained in the try-range of any entry - they 86 /// form gaps in the table. Entries must be ordered by try-range address. 87 88 void computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites, 89 const RangeMapType &PadMap, 90 const SmallVectorImpl<const LandingPadInfo *> &LPs, 91 const SmallVectorImpl<unsigned> &FirstActions); 92 93 /// Emit landing pads and actions. 94 /// 95 /// The general organization of the table is complex, but the basic concepts 96 /// are easy. First there is a header which describes the location and 97 /// organization of the three components that follow. 98 /// 1. The landing pad site information describes the range of code covered 99 /// by the try. In our case it's an accumulation of the ranges covered 100 /// by the invokes in the try. There is also a reference to the landing 101 /// pad that handles the exception once processed. Finally an index into 102 /// the actions table. 103 /// 2. The action table, in our case, is composed of pairs of type ids 104 /// and next action offset. Starting with the action index from the 105 /// landing pad site, each type Id is checked for a match to the current 106 /// exception. If it matches then the exception and type id are passed 107 /// on to the landing pad. Otherwise the next action is looked up. This 108 /// chain is terminated with a next action of zero. If no type id is 109 /// found the frame is unwound and handling continues. 110 /// 3. Type id table contains references to all the C++ typeinfo for all 111 /// catches in the function. This tables is reversed indexed base 1. 112 void emitExceptionTable(); 113 114 virtual void emitTypeInfos(unsigned TTypeEncoding); 115 116 public: 117 EHStreamer(AsmPrinter *A); 118 virtual ~EHStreamer(); 119 120 /// Emit all exception information that should come after the content. 121 void endModule() override; 122 123 /// Gather pre-function exception information. Assumes being emitted 124 /// immediately after the function entry point. 125 void beginFunction(const MachineFunction *MF) override; 126 127 /// Gather and emit post-function exception information. 128 void endFunction(const MachineFunction *) override; 129 130 // Unused. 131 void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {} 132 void beginInstruction(const MachineInstr *MI) override {} 133 void endInstruction() override {} 134 }; 135 } 136 137 #endif 138 139
