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_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H 15 #define LLVM_LIB_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 class MCSymbol; 27 class MCSymbolRefExpr; 28 29 template <typename T> 30 class SmallVectorImpl; 31 32 /// Emits exception handling directives. 33 class EHStreamer : public AsmPrinterHandler { 34 protected: 35 /// Target of directive emission. 36 AsmPrinter *Asm; 37 38 /// Collected machine module information. 39 MachineModuleInfo *MMI; 40 41 /// How many leading type ids two landing pads have in common. 42 static unsigned sharedTypeIDs(const LandingPadInfo *L, 43 const LandingPadInfo *R); 44 45 /// Structure holding a try-range and the associated landing pad. 46 struct PadRange { 47 // The index of the landing pad. 48 unsigned PadIndex; 49 // The index of the begin and end labels in the landing pad's label lists. 50 unsigned RangeIndex; 51 }; 52 53 typedef DenseMap<MCSymbol *, PadRange> RangeMapType; 54 55 /// Structure describing an entry in the actions table. 56 struct ActionEntry { 57 int ValueForTypeID; // The value to write - may not be equal to the type id. 58 int NextAction; 59 unsigned Previous; 60 }; 61 62 /// Structure describing an entry in the call-site table. 63 struct CallSiteEntry { 64 // The 'try-range' is BeginLabel .. EndLabel. 65 MCSymbol *BeginLabel; // Null indicates the start of the function. 66 MCSymbol *EndLabel; // Null indicates the end of the function. 67 68 // LPad contains the landing pad start labels. 69 const LandingPadInfo *LPad; // Null indicates that there is no landing pad. 70 unsigned Action; 71 }; 72 73 /// Compute the actions table and gather the first action index for each 74 /// landing pad site. 75 unsigned computeActionsTable(const SmallVectorImpl<const LandingPadInfo*>&LPs, 76 SmallVectorImpl<ActionEntry> &Actions, 77 SmallVectorImpl<unsigned> &FirstActions); 78 79 /// Return `true' if this is a call to a function marked `nounwind'. Return 80 /// `false' otherwise. 81 bool callToNoUnwindFunction(const MachineInstr *MI); 82 83 void computePadMap(const SmallVectorImpl<const LandingPadInfo *> &LandingPads, 84 RangeMapType &PadMap); 85 86 /// Compute the call-site table. The entry for an invoke has a try-range 87 /// containing the call, a non-zero landing pad and an appropriate action. 88 /// The entry for an ordinary call has a try-range containing the call and 89 /// zero for the landing pad and the action. Calls marked 'nounwind' have 90 /// no entry and must not be contained in the try-range of any entry - they 91 /// form gaps in the table. Entries must be ordered by try-range address. 92 void computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites, 93 const SmallVectorImpl<const LandingPadInfo *> &LPs, 94 const SmallVectorImpl<unsigned> &FirstActions); 95 96 /// Emit landing pads and actions. 97 /// 98 /// The general organization of the table is complex, but the basic concepts 99 /// are easy. First there is a header which describes the location and 100 /// organization of the three components that follow. 101 /// 1. The landing pad site information describes the range of code covered 102 /// by the try. In our case it's an accumulation of the ranges covered 103 /// by the invokes in the try. There is also a reference to the landing 104 /// pad that handles the exception once processed. Finally an index into 105 /// the actions table. 106 /// 2. The action table, in our case, is composed of pairs of type ids 107 /// and next action offset. Starting with the action index from the 108 /// landing pad site, each type Id is checked for a match to the current 109 /// exception. If it matches then the exception and type id are passed 110 /// on to the landing pad. Otherwise the next action is looked up. This 111 /// chain is terminated with a next action of zero. If no type id is 112 /// found the frame is unwound and handling continues. 113 /// 3. Type id table contains references to all the C++ typeinfo for all 114 /// catches in the function. This tables is reversed indexed base 1. 115 void emitExceptionTable(); 116 117 virtual void emitTypeInfos(unsigned TTypeEncoding); 118 119 // Helpers for for identifying what kind of clause an EH typeid or selector 120 // corresponds to. Negative selectors are for filter clauses, the zero 121 // selector is for cleanups, and positive selectors are for catch clauses. 122 static bool isFilterEHSelector(int Selector) { return Selector < 0; } 123 static bool isCleanupEHSelector(int Selector) { return Selector == 0; } 124 static bool isCatchEHSelector(int Selector) { return Selector > 0; } 125 126 public: 127 EHStreamer(AsmPrinter *A); 128 ~EHStreamer() 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
