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 #include "llvm/Support/Compiler.h" 20 21 namespace llvm { 22 23 class AsmPrinter; 24 struct LandingPadInfo; 25 class MachineInstr; 26 class MachineModuleInfo; 27 class MCSymbol; 28 template <typename T> class SmallVectorImpl; 29 30 /// Emits exception handling directives. 31 class LLVM_LIBRARY_VISIBILITY 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 48 // The index of the begin and end labels in the landing pad's label lists. 49 unsigned RangeIndex; 50 }; 51 52 using RangeMapType = DenseMap<MCSymbol *, PadRange>; 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 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 void computePadMap(const SmallVectorImpl<const LandingPadInfo *> &LandingPads, 80 RangeMapType &PadMap); 81 82 /// Compute the call-site table. The entry for an invoke has a try-range 83 /// containing the call, a non-zero landing pad and an appropriate action. 84 /// The entry for an ordinary call has a try-range containing the call and 85 /// zero for the landing pad and the action. Calls marked 'nounwind' have 86 /// no entry and must not be contained in the try-range of any entry - they 87 /// form gaps in the table. Entries must be ordered by try-range address. 88 void computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites, 89 const SmallVectorImpl<const LandingPadInfo *> &LPs, 90 const SmallVectorImpl<unsigned> &FirstActions); 91 92 /// Emit landing pads and actions. 93 /// 94 /// The general organization of the table is complex, but the basic concepts 95 /// are easy. First there is a header which describes the location and 96 /// organization of the three components that follow. 97 /// 1. The landing pad site information describes the range of code covered 98 /// by the try. In our case it's an accumulation of the ranges covered 99 /// by the invokes in the try. There is also a reference to the landing 100 /// pad that handles the exception once processed. Finally an index into 101 /// the actions table. 102 /// 2. The action table, in our case, is composed of pairs of type ids 103 /// and next action offset. Starting with the action index from the 104 /// landing pad site, each type Id is checked for a match to the current 105 /// exception. If it matches then the exception and type id are passed 106 /// on to the landing pad. Otherwise the next action is looked up. This 107 /// chain is terminated with a next action of zero. If no type id is 108 /// found the frame is unwound and handling continues. 109 /// 3. Type id table contains references to all the C++ typeinfo for all 110 /// catches in the function. This tables is reversed indexed base 1. 111 void emitExceptionTable(); 112 113 virtual void emitTypeInfos(unsigned TTypeEncoding); 114 115 // Helpers for for identifying what kind of clause an EH typeid or selector 116 // corresponds to. Negative selectors are for filter clauses, the zero 117 // selector is for cleanups, and positive selectors are for catch clauses. 118 static bool isFilterEHSelector(int Selector) { return Selector < 0; } 119 static bool isCleanupEHSelector(int Selector) { return Selector == 0; } 120 static bool isCatchEHSelector(int Selector) { return Selector > 0; } 121 122 public: 123 EHStreamer(AsmPrinter *A); 124 ~EHStreamer() override; 125 126 // Unused. 127 void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {} 128 void beginInstruction(const MachineInstr *MI) override {} 129 void endInstruction() override {} 130 131 /// Return `true' if this is a call to a function marked `nounwind'. Return 132 /// `false' otherwise. 133 static bool callToNoUnwindFunction(const MachineInstr *MI); 134 }; 135 136 } // end namespace llvm 137 138 #endif // LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H 139