EHStreamer.h revision 0c7f116bb6950ef819323d855415b2f2b0aad987 
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 AsmPrinter;
26class MCSymbol;
27class MCSymbolRefExpr;
28
29template <typename T>
30class SmallVectorImpl;
31
32/// Emits exception handling directives.
33class EHStreamer : public AsmPrinterHandler {
34protected:
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
126public:
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