aboutsummaryrefslogtreecommitdiffstats
path: root/lib/CodeGen/AsmPrinter/EHStreamer.h
blob: 9b316ff00e9bb6364f182f3e2beb43f52dcdd30e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
//===-- EHStreamer.h - Exception Handling Directive Streamer ---*- C++ -*--===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing exception info into assembly files.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H
#define LLVM_LIB_CODEGEN_ASMPRINTER_EHSTREAMER_H

#include "AsmPrinterHandler.h"
#include "llvm/ADT/DenseMap.h"

namespace llvm {
struct LandingPadInfo;
class MachineModuleInfo;
class MachineInstr;
class MachineFunction;
class AsmPrinter;
class MCSymbol;
class MCSymbolRefExpr;

template <typename T>
class SmallVectorImpl;

/// Emits exception handling directives.
class EHStreamer : public AsmPrinterHandler {
protected:
  /// Target of directive emission.
  AsmPrinter *Asm;

  /// Collected machine module information.
  MachineModuleInfo *MMI;

  /// How many leading type ids two landing pads have in common.
  static unsigned sharedTypeIDs(const LandingPadInfo *L,
                                const LandingPadInfo *R);

  /// Structure holding a try-range and the associated landing pad.
  struct PadRange {
    // The index of the landing pad.
    unsigned PadIndex;
    // The index of the begin and end labels in the landing pad's label lists.
    unsigned RangeIndex;
  };

  typedef DenseMap<MCSymbol *, PadRange> RangeMapType;

  /// Structure describing an entry in the actions table.
  struct ActionEntry {
    int ValueForTypeID; // The value to write - may not be equal to the type id.
    int NextAction;
    unsigned Previous;
  };

  /// Structure describing an entry in the call-site table.
  struct CallSiteEntry {
    // The 'try-range' is BeginLabel .. EndLabel.
    MCSymbol *BeginLabel; // Null indicates the start of the function.
    MCSymbol *EndLabel;   // Null indicates the end of the function.

    // LPad contains the landing pad start labels.
    const LandingPadInfo *LPad; // Null indicates that there is no landing pad.
    unsigned Action;
  };

  /// Compute the actions table and gather the first action index for each
  /// landing pad site.
  unsigned computeActionsTable(const SmallVectorImpl<const LandingPadInfo*>&LPs,
                               SmallVectorImpl<ActionEntry> &Actions,
                               SmallVectorImpl<unsigned> &FirstActions);

  /// Return `true' if this is a call to a function marked `nounwind'. Return
  /// `false' otherwise.
  bool callToNoUnwindFunction(const MachineInstr *MI);

  /// Compute the call-site table.  The entry for an invoke has a try-range
  /// containing the call, a non-zero landing pad and an appropriate action.
  /// The entry for an ordinary call has a try-range containing the call and
  /// zero for the landing pad and the action.  Calls marked 'nounwind' have
  /// no entry and must not be contained in the try-range of any entry - they
  /// form gaps in the table.  Entries must be ordered by try-range address.

  void computeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
                            const SmallVectorImpl<const LandingPadInfo *> &LPs,
                            const SmallVectorImpl<unsigned> &FirstActions);

  /// Emit landing pads and actions.
  ///
  /// The general organization of the table is complex, but the basic concepts
  /// are easy.  First there is a header which describes the location and
  /// organization of the three components that follow.
  ///  1. The landing pad site information describes the range of code covered
  ///     by the try.  In our case it's an accumulation of the ranges covered
  ///     by the invokes in the try.  There is also a reference to the landing
  ///     pad that handles the exception once processed.  Finally an index into
  ///     the actions table.
  ///  2. The action table, in our case, is composed of pairs of type ids
  ///     and next action offset.  Starting with the action index from the
  ///     landing pad site, each type Id is checked for a match to the current
  ///     exception.  If it matches then the exception and type id are passed
  ///     on to the landing pad.  Otherwise the next action is looked up.  This
  ///     chain is terminated with a next action of zero.  If no type id is
  ///     found the frame is unwound and handling continues.
  ///  3. Type id table contains references to all the C++ typeinfo for all
  ///     catches in the function.  This tables is reversed indexed base 1.
  void emitExceptionTable();

  virtual void emitTypeInfos(unsigned TTypeEncoding);

  // Helpers for for identifying what kind of clause an EH typeid or selector
  // corresponds to. Negative selectors are for filter clauses, the zero
  // selector is for cleanups, and positive selectors are for catch clauses.
  static bool isFilterEHSelector(int Selector) { return Selector < 0; }
  static bool isCleanupEHSelector(int Selector) { return Selector == 0; }
  static bool isCatchEHSelector(int Selector) { return Selector > 0; }

public:
  EHStreamer(AsmPrinter *A);
  virtual ~EHStreamer();

  /// Emit all exception information that should come after the content.
  void endModule() override;

  /// Gather pre-function exception information.  Assumes being emitted
  /// immediately after the function entry point.
  void beginFunction(const MachineFunction *MF) override;

  /// Gather and emit post-function exception information.
  void endFunction(const MachineFunction *) override;

  // Unused.
  void setSymbolSize(const MCSymbol *Sym, uint64_t Size) override {}
  void beginInstruction(const MachineInstr *MI) override {}
  void endInstruction() override {}
};
}

#endif