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1//===- EHStreamer.h - Exception Handling Directive Streamer -----*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file contains support for writing exception info into assembly files.10//11//===----------------------------------------------------------------------===//12 13#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H14#define LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H15 16#include "llvm/ADT/DenseMap.h"17#include "llvm/CodeGen/AsmPrinterHandler.h"18#include "llvm/Support/Compiler.h"19 20namespace llvm {21 22class AsmPrinter;23struct LandingPadInfo;24class MachineInstr;25class MachineModuleInfo;26class MCSymbol;27template <typename T> class SmallVectorImpl;28 29/// Emits exception handling directives.30class LLVM_LIBRARY_VISIBILITY EHStreamer : public AsmPrinterHandler {31protected:32 /// Target of directive emission.33 AsmPrinter *Asm;34 35 /// Collected machine module information.36 MachineModuleInfo *MMI;37 38 /// How many leading type ids two landing pads have in common.39 static unsigned sharedTypeIDs(const LandingPadInfo *L,40 const LandingPadInfo *R);41 42 /// Structure holding a try-range and the associated landing pad.43 struct PadRange {44 // The index of the landing pad.45 unsigned PadIndex;46 47 // The index of the begin and end labels in the landing pad's label lists.48 unsigned RangeIndex;49 };50 51 using RangeMapType = DenseMap<MCSymbol *, PadRange>;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; // Null indicates the start of the function.64 MCSymbol *EndLabel; // Null indicates the end of the function.65 66 // LPad contains the landing pad start labels.67 const LandingPadInfo *LPad; // Null indicates that there is no landing pad.68 69 unsigned Action;70 };71 72 /// Structure describing a contiguous range of call-sites which reside73 /// in the same procedure fragment. With -fbasic-block-sections, there will74 /// be one call site range per basic block section. Otherwise, we will have75 /// one call site range containing all the call sites in the function.76 struct CallSiteRange {77 // Symbol marking the beginning of the precedure fragment.78 MCSymbol *FragmentBeginLabel = nullptr;79 // Symbol marking the end of the procedure fragment.80 MCSymbol *FragmentEndLabel = nullptr;81 // LSDA symbol for this call-site range.82 MCSymbol *ExceptionLabel = nullptr;83 // Index of the first call-site entry in the call-site table which84 // belongs to this range.85 size_t CallSiteBeginIdx = 0;86 // Index just after the last call-site entry in the call-site table which87 // belongs to this range.88 size_t CallSiteEndIdx = 0;89 // Whether this is the call-site range containing all the landing pads.90 bool IsLPRange = false;91 };92 93 /// Compute the actions table and gather the first action index for each94 /// landing pad site.95 void computeActionsTable(96 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,97 SmallVectorImpl<ActionEntry> &Actions,98 SmallVectorImpl<unsigned> &FirstActions);99 100 void computePadMap(const SmallVectorImpl<const LandingPadInfo *> &LandingPads,101 RangeMapType &PadMap);102 103 /// Compute the call-site table and the call-site ranges. The entry for an104 /// invoke has a try-range containing the call, a non-zero landing pad and an105 /// appropriate action. The entry for an ordinary call has a try-range106 /// containing the call and zero for the landing pad and the action. Calls107 /// marked 'nounwind' have no entry and must not be contained in the try-range108 /// of any entry - they form gaps in the table. Entries must be ordered by109 /// try-range address. CallSiteRanges vector is only populated for Itanium110 /// exception handling.111 virtual void computeCallSiteTable(112 SmallVectorImpl<CallSiteEntry> &CallSites,113 SmallVectorImpl<CallSiteRange> &CallSiteRanges,114 const SmallVectorImpl<const LandingPadInfo *> &LandingPads,115 const SmallVectorImpl<unsigned> &FirstActions);116 117 /// Emit landing pads and actions.118 ///119 /// The general organization of the table is complex, but the basic concepts120 /// are easy. First there is a header which describes the location and121 /// organization of the three components that follow.122 /// 1. The landing pad site information describes the range of code covered123 /// by the try. In our case it's an accumulation of the ranges covered124 /// by the invokes in the try. There is also a reference to the landing125 /// pad that handles the exception once processed. Finally an index into126 /// the actions table.127 /// 2. The action table, in our case, is composed of pairs of type ids128 /// and next action offset. Starting with the action index from the129 /// landing pad site, each type Id is checked for a match to the current130 /// exception. If it matches then the exception and type id are passed131 /// on to the landing pad. Otherwise the next action is looked up. This132 /// chain is terminated with a next action of zero. If no type id is133 /// found the frame is unwound and handling continues.134 /// 3. Type id table contains references to all the C++ typeinfo for all135 /// catches in the function. This tables is reversed indexed base 1.136 ///137 /// Returns the starting symbol of an exception table.138 MCSymbol *emitExceptionTable();139 140 virtual void emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel);141 142 // Helpers for identifying what kind of clause an EH typeid or selector143 // corresponds to. Negative selectors are for filter clauses, the zero144 // selector is for cleanups, and positive selectors are for catch clauses.145 static bool isFilterEHSelector(int Selector) { return Selector < 0; }146 static bool isCleanupEHSelector(int Selector) { return Selector == 0; }147 static bool isCatchEHSelector(int Selector) { return Selector > 0; }148 149public:150 EHStreamer(AsmPrinter *A);151 ~EHStreamer() override;152 153 /// Return `true' if this is a call to a function marked `nounwind'. Return154 /// `false' otherwise.155 static bool callToNoUnwindFunction(const MachineInstr *MI);156};157 158} // end namespace llvm159 160#endif // LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H161