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
20namespace llvm {
21struct LandingPadInfo;
22class MachineModuleInfo;
23class MachineInstr;
24class MachineFunction;
25class MCSymbol;
26class MCSymbolRefExpr;
27
28template <typename T>
29class SmallVectorImpl;
30
31/// Emits exception handling directives.
32class LLVM_LIBRARY_VISIBILITY EHStreamer : public AsmPrinterHandler {
33protected:
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.
117  static bool isFilterEHSelector(int Selector) { return Selector < 0; }
118  static bool isCleanupEHSelector(int Selector) { return Selector == 0; }
119  static bool isCatchEHSelector(int Selector) { return Selector > 0; }
120
121public:
122  EHStreamer(AsmPrinter *A);
123  ~EHStreamer() override;
124
125  // Unused.
126  void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {}
127  void beginInstruction(const MachineInstr *MI) override {}
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