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 MCSymbol; 26 class MCSymbolRefExpr; 27 28 template <typename T> 29 class SmallVectorImpl; 30 31 /// Emits exception handling directives. 32 class LLVM_LIBRARY_VISIBILITY EHStreamer : public AsmPrinterHandler { 33 protected: 34 /// Target of directive emission. 35 AsmPrinter *Asm; 36 37 /// Collected machine module information. 38 MachineModuleInfo *MMI; 39 40 /// How many leading type ids two landing pads have in common. 41 static unsigned sharedTypeIDs(const LandingPadInfo *L, 42 const LandingPadInfo *R); 43 44 /// Structure holding a try-range and the associated landing pad. 45 struct PadRange { 46 // The index of the landing pad. 47 unsigned PadIndex; 48 // The index of the begin and end labels in the landing pad's label lists. 49 unsigned RangeIndex; 50 }; 51 52 typedef DenseMap<MCSymbol *, PadRange> RangeMapType; 53 54 /// Structure describing an entry in the actions table. 55 struct ActionEntry { 56 int ValueForTypeID; // The value to write - may not be equal to the type id. 57 int NextAction; 58 unsigned Previous; 59 }; 60 61 /// Structure describing an entry in the call-site table. 62 struct CallSiteEntry { 63 // The 'try-range' is BeginLabel .. EndLabel. 64 MCSymbol *BeginLabel; // Null indicates the start of the function. 65 MCSymbol *EndLabel; // Null indicates the end of the function. 66 67 // LPad contains the landing pad start labels. 68 const LandingPadInfo *LPad; // Null indicates that there is no landing pad. 69 unsigned Action; 70 }; 71 72 /// Compute the actions table and gather the first action index for each 73 /// landing pad site. 74 unsigned computeActionsTable(const SmallVectorImpl<const LandingPadInfo*>&LPs, 75 SmallVectorImpl<ActionEntry> &Actions, 76 SmallVectorImpl<unsigned> &FirstActions); 77 78 void computePadMap(const SmallVectorImpl<const LandingPadInfo *> &LandingPads, 79 RangeMapType &PadMap); 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 void computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites, 88 const SmallVectorImpl<const LandingPadInfo *> &LPs, 89 const SmallVectorImpl<unsigned> &FirstActions); 90 91 /// Emit landing pads and actions. 92 /// 93 /// The general organization of the table is complex, but the basic concepts 94 /// are easy. First there is a header which describes the location and 95 /// organization of the three components that follow. 96 /// 1. The landing pad site information describes the range of code covered 97 /// by the try. In our case it's an accumulation of the ranges covered 98 /// by the invokes in the try. There is also a reference to the landing 99 /// pad that handles the exception once processed. Finally an index into 100 /// the actions table. 101 /// 2. The action table, in our case, is composed of pairs of type ids 102 /// and next action offset. Starting with the action index from the 103 /// landing pad site, each type Id is checked for a match to the current 104 /// exception. If it matches then the exception and type id are passed 105 /// on to the landing pad. Otherwise the next action is looked up. This 106 /// chain is terminated with a next action of zero. If no type id is 107 /// found the frame is unwound and handling continues. 108 /// 3. Type id table contains references to all the C++ typeinfo for all 109 /// catches in the function. This tables is reversed indexed base 1. 110 void emitExceptionTable(); 111 112 virtual void emitTypeInfos(unsigned TTypeEncoding); 113 114 // Helpers for for identifying what kind of clause an EH typeid or selector 115 // corresponds to. Negative selectors are for filter clauses, the zero 116 // selector is for cleanups, and positive selectors are for catch clauses. isFilterEHSelector(int Selector)117 static bool isFilterEHSelector(int Selector) { return Selector < 0; } isCleanupEHSelector(int Selector)118 static bool isCleanupEHSelector(int Selector) { return Selector == 0; } isCatchEHSelector(int Selector)119 static bool isCatchEHSelector(int Selector) { return Selector > 0; } 120 121 public: 122 EHStreamer(AsmPrinter *A); 123 ~EHStreamer() override; 124 125 // Unused. setSymbolSize(const MCSymbol * Sym,uint64_t Size)126 void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {} beginInstruction(const MachineInstr * MI)127 void beginInstruction(const MachineInstr *MI) override {} endInstruction()128 void endInstruction() override {} 129 130 /// Return `true' if this is a call to a function marked `nounwind'. Return 131 /// `false' otherwise. 132 static bool callToNoUnwindFunction(const MachineInstr *MI); 133 }; 134 } 135 136 #endif 137 138