DwarfException.h revision 75e113cb5a14f3e749d1c84b3f5c91706e1c47e8 
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 "DIE.h"
18#include "DwarfPrinter.h"
19#include "llvm/CodeGen/AsmPrinter.h"
20#include "llvm/ADT/DenseMap.h"
21#include <string>
22
23namespace llvm {
24
25struct LandingPadInfo;
26class MachineModuleInfo;
27class MCAsmInfo;
28class MCExpr;
29class Timer;
30class raw_ostream;
31
32//===----------------------------------------------------------------------===//
33/// DwarfException - Emits Dwarf exception handling directives.
34///
35class DwarfException : public DwarfPrinter {
36  struct FunctionEHFrameInfo {
37    MCSymbol *FunctionEHSym;  // L_foo.eh
38    unsigned Number;
39    unsigned PersonalityIndex;
40    bool hasCalls;
41    bool hasLandingPads;
42    std::vector<MachineMove> Moves;
43    const Function *function;
44
45    FunctionEHFrameInfo(MCSymbol *EHSym, unsigned Num, unsigned P,
46                        bool hC, bool hL,
47                        const std::vector<MachineMove> &M,
48                        const Function *f):
49      FunctionEHSym(EHSym), Number(Num), PersonalityIndex(P),
50      hasCalls(hC), hasLandingPads(hL), Moves(M), function (f) { }
51  };
52
53  std::vector<FunctionEHFrameInfo> EHFrames;
54
55  /// UsesLSDA - Indicates whether an FDE that uses the CIE at the given index
56  /// uses an LSDA. If so, then we need to encode that information in the CIE's
57  /// augmentation.
58  DenseMap<unsigned, bool> UsesLSDA;
59
60  /// shouldEmitTable - Per-function flag to indicate if EH tables should
61  /// be emitted.
62  bool shouldEmitTable;
63
64  /// shouldEmitMoves - Per-function flag to indicate if frame moves info
65  /// should be emitted.
66  bool shouldEmitMoves;
67
68  /// shouldEmitTableModule - Per-module flag to indicate if EH tables
69  /// should be emitted.
70  bool shouldEmitTableModule;
71
72  /// shouldEmitFrameModule - Per-module flag to indicate if frame moves
73  /// should be emitted.
74  bool shouldEmitMovesModule;
75
76  /// ExceptionTimer - Timer for the Dwarf exception writer.
77  Timer *ExceptionTimer;
78
79  /// EmitCIE - Emit a Common Information Entry (CIE). This holds information
80  /// that is shared among many Frame Description Entries.  There is at least
81  /// one CIE in every non-empty .debug_frame section.
82  void EmitCIE(const Function *Personality, unsigned Index);
83
84  /// EmitFDE - Emit the Frame Description Entry (FDE) for the function.
85  void EmitFDE(const FunctionEHFrameInfo &EHFrameInfo);
86
87  /// EmitExceptionTable - Emit landing pads and actions.
88  ///
89  /// The general organization of the table is complex, but the basic concepts
90  /// are easy.  First there is a header which describes the location and
91  /// organization of the three components that follow.
92  ///  1. The landing pad site information describes the range of code covered
93  ///     by the try.  In our case it's an accumulation of the ranges covered
94  ///     by the invokes in the try.  There is also a reference to the landing
95  ///     pad that handles the exception once processed.  Finally an index into
96  ///     the actions table.
97  ///  2. The action table, in our case, is composed of pairs of type ids
98  ///     and next action offset.  Starting with the action index from the
99  ///     landing pad site, each type Id is checked for a match to the current
100  ///     exception.  If it matches then the exception and type id are passed
101  ///     on to the landing pad.  Otherwise the next action is looked up.  This
102  ///     chain is terminated with a next action of zero.  If no type id is
103  ///     found the frame is unwound and handling continues.
104  ///  3. Type id table contains references to all the C++ typeinfo for all
105  ///     catches in the function.  This tables is reversed indexed base 1.
106
107  /// SharedTypeIds - How many leading type ids two landing pads have in common.
108  static unsigned SharedTypeIds(const LandingPadInfo *L,
109                                const LandingPadInfo *R);
110
111  /// PadLT - Order landing pads lexicographically by type id.
112  static bool PadLT(const LandingPadInfo *L, const LandingPadInfo *R);
113
114  /// PadRange - Structure holding a try-range and the associated landing pad.
115  struct PadRange {
116    // The index of the landing pad.
117    unsigned PadIndex;
118    // The index of the begin and end labels in the landing pad's label lists.
119    unsigned RangeIndex;
120  };
121
122  typedef DenseMap<MCSymbol *, PadRange> RangeMapType;
123
124  /// ActionEntry - Structure describing an entry in the actions table.
125  struct ActionEntry {
126    int ValueForTypeID; // The value to write - may not be equal to the type id.
127    int NextAction;
128    unsigned Previous;
129  };
130
131  /// CallSiteEntry - Structure describing an entry in the call-site table.
132  struct CallSiteEntry {
133    // The 'try-range' is BeginLabel .. EndLabel.
134    MCSymbol *BeginLabel; // zero indicates the start of the function.
135    MCSymbol *EndLabel;   // zero indicates the end of the function.
136
137    // The landing pad starts at PadLabel.
138    MCSymbol *PadLabel;   // zero indicates that there is no landing pad.
139    unsigned Action;
140  };
141
142  /// ComputeActionsTable - Compute the actions table and gather the first
143  /// action index for each landing pad site.
144  unsigned ComputeActionsTable(const SmallVectorImpl<const LandingPadInfo*>&LPs,
145                               SmallVectorImpl<ActionEntry> &Actions,
146                               SmallVectorImpl<unsigned> &FirstActions);
147
148  /// CallToNoUnwindFunction - Return `true' if this is a call to a function
149  /// marked `nounwind'. Return `false' otherwise.
150  bool CallToNoUnwindFunction(const MachineInstr *MI);
151
152  /// ComputeCallSiteTable - Compute the call-site table.  The entry for an
153  /// invoke has a try-range containing the call, a non-zero landing pad and an
154  /// appropriate action.  The entry for an ordinary call has a try-range
155  /// containing the call and zero for the landing pad and the action.  Calls
156  /// marked 'nounwind' have no entry and must not be contained in the try-range
157  /// of any entry - they form gaps in the table.  Entries must be ordered by
158  /// try-range address.
159  void ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
160                            const RangeMapType &PadMap,
161                            const SmallVectorImpl<const LandingPadInfo *> &LPs,
162                            const SmallVectorImpl<unsigned> &FirstActions);
163  void EmitExceptionTable();
164
165public:
166  //===--------------------------------------------------------------------===//
167  // Main entry points.
168  //
169  DwarfException(AsmPrinter *A);
170  virtual ~DwarfException();
171
172  /// BeginModule - Emit all exception information that should come prior to the
173  /// content.
174  void BeginModule(Module *m) {
175    this->M = m;
176    this->MMI = Asm->MMI;
177  }
178
179  /// EndModule - Emit all exception information that should come after the
180  /// content.
181  void EndModule();
182
183  /// BeginFunction - Gather pre-function exception information.  Assumes being
184  /// emitted immediately after the function entry point.
185  void BeginFunction(const MachineFunction *MF);
186
187  /// EndFunction - Gather and emit post-function exception information.
188  void EndFunction();
189};
190
191} // End of namespace llvm
192
193#endif
194