DwarfException.h revision ce3c6253d9783bd8ef899570110bfd4339570fb3 
1//===-- DwarfException.h - Dwarf Exception Framework -----------*- 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 dwarf exception info into asm files.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CODEGEN_ASMPRINTER_DWARFEXCEPTION_H
15#define LLVM_CODEGEN_ASMPRINTER_DWARFEXCEPTION_H
16
17#include "llvm/ADT/DenseMap.h"
18#include <vector>
19
20namespace llvm {
21
22template <typename T> class SmallVectorImpl;
23struct LandingPadInfo;
24class MachineModuleInfo;
25class MachineMove;
26class MachineInstr;
27class MachineFunction;
28class MCAsmInfo;
29class MCExpr;
30class MCSymbol;
31class Function;
32class AsmPrinter;
33
34//===----------------------------------------------------------------------===//
35/// DwarfException - Emits Dwarf exception handling directives.
36///
37class DwarfException {
38  /// Asm - Target of Dwarf emission.
39  AsmPrinter *Asm;
40
41  /// MMI - Collected machine module information.
42  MachineModuleInfo *MMI;
43
44  struct FunctionEHFrameInfo {
45    MCSymbol *FunctionEHSym;  // L_foo.eh
46    unsigned Number;
47    unsigned PersonalityIndex;
48    bool hasCalls;
49    bool hasLandingPads;
50    std::vector<MachineMove> Moves;
51    const Function *function;
52
53    FunctionEHFrameInfo(MCSymbol *EHSym, unsigned Num, unsigned P,
54                        bool hC, bool hL,
55                        const std::vector<MachineMove> &M,
56                        const Function *f):
57      FunctionEHSym(EHSym), Number(Num), PersonalityIndex(P),
58      hasCalls(hC), hasLandingPads(hL), Moves(M), function (f) { }
59  };
60
61  std::vector<FunctionEHFrameInfo> EHFrames;
62
63  /// UsesLSDA - Indicates whether an FDE that uses the CIE at the given index
64  /// uses an LSDA. If so, then we need to encode that information in the CIE's
65  /// augmentation.
66  DenseMap<unsigned, bool> UsesLSDA;
67
68  /// shouldEmitTable - Per-function flag to indicate if EH tables should
69  /// be emitted.
70  bool shouldEmitTable;
71
72  /// shouldEmitMoves - Per-function flag to indicate if frame moves info
73  /// should be emitted.
74  bool shouldEmitMoves;
75
76  /// shouldEmitTableModule - Per-module flag to indicate if EH tables
77  /// should be emitted.
78  bool shouldEmitTableModule;
79
80  /// shouldEmitFrameModule - Per-module flag to indicate if frame moves
81  /// should be emitted.
82  bool shouldEmitMovesModule;
83
84  /// EmitCIE - Emit a Common Information Entry (CIE). This holds information
85  /// that is shared among many Frame Description Entries.  There is at least
86  /// one CIE in every non-empty .debug_frame section.
87  void EmitCIE(const Function *Personality, unsigned Index);
88
89  /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
90  void EmitFDE(const FunctionEHFrameInfo &EHFrameInfo);
91
92  /// EmitExceptionTable - 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
112  /// SharedTypeIds - How many leading type ids two landing pads have in common.
113  static unsigned SharedTypeIds(const LandingPadInfo *L,
114                                const LandingPadInfo *R);
115
116  /// PadLT - Order landing pads lexicographically by type id.
117  static bool PadLT(const LandingPadInfo *L, const LandingPadInfo *R);
118
119  /// PadRange - Structure holding a try-range and the associated landing pad.
120  struct PadRange {
121    // The index of the landing pad.
122    unsigned PadIndex;
123    // The index of the begin and end labels in the landing pad's label lists.
124    unsigned RangeIndex;
125  };
126
127  typedef DenseMap<MCSymbol *, PadRange> RangeMapType;
128
129  /// ActionEntry - Structure describing an entry in the actions table.
130  struct ActionEntry {
131    int ValueForTypeID; // The value to write - may not be equal to the type id.
132    int NextAction;
133    unsigned Previous;
134  };
135
136  /// CallSiteEntry - Structure describing an entry in the call-site table.
137  struct CallSiteEntry {
138    // The 'try-range' is BeginLabel .. EndLabel.
139    MCSymbol *BeginLabel; // zero indicates the start of the function.
140    MCSymbol *EndLabel;   // zero indicates the end of the function.
141
142    // The landing pad starts at PadLabel.
143    MCSymbol *PadLabel;   // zero indicates that there is no landing pad.
144    unsigned Action;
145  };
146
147  /// ComputeActionsTable - Compute the actions table and gather the first
148  /// action index for each landing pad site.
149  unsigned ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*>&LPs,
150                               SmallVectorImpl<ActionEntry> &Actions,
151                               SmallVectorImpl<unsigned> &FirstActions);
152
153  /// CallToNoUnwindFunction - Return `true' if this is a call to a function
154  /// marked `nounwind'. Return `false' otherwise.
155  bool CallToNoUnwindFunction(const MachineInstr *MI);
156
157  /// ComputeCallSiteTable - Compute the call-site table.  The entry for an
158  /// invoke has a try-range containing the call, a non-zero landing pad and an
159  /// appropriate action.  The entry for an ordinary call has a try-range
160  /// containing the call and zero for the landing pad and the action.  Calls
161  /// marked 'nounwind' have no entry and must not be contained in the try-range
162  /// of any entry - they form gaps in the table.  Entries must be ordered by
163  /// try-range address.
164  void ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
165                            const RangeMapType &PadMap,
166                            const SmallVectorImpl<const LandingPadInfo *> &LPs,
167                            const SmallVectorImpl<unsigned> &FirstActions);
168  void EmitExceptionTable();
169
170public:
171  //===--------------------------------------------------------------------===//
172  // Main entry points.
173  //
174  DwarfException(AsmPrinter *A);
175  ~DwarfException();
176
177  /// EndModule - Emit all exception information that should come after the
178  /// content.
179  void EndModule();
180
181  /// BeginFunction - Gather pre-function exception information.  Assumes being
182  /// emitted immediately after the function entry point.
183  void BeginFunction(const MachineFunction *MF);
184
185  /// EndFunction - Gather and emit post-function exception information.
186  void EndFunction();
187};
188
189} // End of namespace llvm
190
191#endif
192