DwarfCFIException.cpp revision f0adba9a7ec8a3031876575a6ffb7db5f1b6f855 
1//===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
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#include "DwarfException.h"
15#include "llvm/Module.h"
16#include "llvm/CodeGen/AsmPrinter.h"
17#include "llvm/CodeGen/MachineModuleInfo.h"
18#include "llvm/CodeGen/MachineFrameInfo.h"
19#include "llvm/CodeGen/MachineFunction.h"
20#include "llvm/CodeGen/MachineLocation.h"
21#include "llvm/MC/MCAsmInfo.h"
22#include "llvm/MC/MCContext.h"
23#include "llvm/MC/MCExpr.h"
24#include "llvm/MC/MCSection.h"
25#include "llvm/MC/MCStreamer.h"
26#include "llvm/MC/MCSymbol.h"
27#include "llvm/Target/Mangler.h"
28#include "llvm/Target/TargetData.h"
29#include "llvm/Target/TargetFrameLowering.h"
30#include "llvm/Target/TargetLoweringObjectFile.h"
31#include "llvm/Target/TargetMachine.h"
32#include "llvm/Target/TargetOptions.h"
33#include "llvm/Target/TargetRegisterInfo.h"
34#include "llvm/Support/Dwarf.h"
35#include "llvm/Support/ErrorHandling.h"
36#include "llvm/Support/FormattedStream.h"
37#include "llvm/ADT/SmallString.h"
38#include "llvm/ADT/StringExtras.h"
39#include "llvm/ADT/Twine.h"
40using namespace llvm;
41
42DwarfCFIException::DwarfCFIException(AsmPrinter *A)
43  : DwarfException(A),
44    shouldEmitTable(false), shouldEmitMoves(false), shouldEmitTableModule(false)
45    {}
46
47DwarfCFIException::~DwarfCFIException() {}
48
49/// EndModule - Emit all exception information that should come after the
50/// content.
51void DwarfCFIException::EndModule() {
52  if (!Asm->MAI->isExceptionHandlingDwarf())
53    return;
54
55  if (!shouldEmitTableModule)
56    return;
57
58  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
59  unsigned PerEncoding = TLOF.getPersonalityEncoding();
60
61  // Begin eh frame section.
62  Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
63
64  if ((PerEncoding & 0x70) != dwarf::DW_EH_PE_pcrel)
65    return;
66
67  // Emit references to all used personality functions
68  const std::vector<const Function*> &Personalities = MMI->getPersonalities();
69  for (size_t i = 0, e = Personalities.size(); i != e; ++i) {
70    Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("personality", i));
71    const MCSymbol *Sym = Asm->Mang->getSymbol(Personalities[i]);
72    unsigned Size = Asm->TM.getTargetData()->getPointerSize();
73    Asm->OutStreamer.EmitSymbolValue(Sym, Size);
74  }
75}
76
77/// BeginFunction - Gather pre-function exception information. Assumes it's
78/// being emitted immediately after the function entry point.
79void DwarfCFIException::BeginFunction(const MachineFunction *MF) {
80  shouldEmitTable = shouldEmitMoves = false;
81
82  // If any landing pads survive, we need an EH table.
83  shouldEmitTable = !MMI->getLandingPads().empty();
84
85  // See if we need frame move info.
86  shouldEmitMoves = MMI->hasDebugInfo() ||
87    !Asm->MF->getFunction()->doesNotThrow() || UnwindTablesMandatory;
88
89  if (shouldEmitMoves || shouldEmitTable)
90    // Assumes in correct section after the entry point.
91    Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
92                                                  Asm->getFunctionNumber()));
93
94  shouldEmitTableModule |= shouldEmitTable;
95
96  if (shouldEmitMoves || shouldEmitTable)
97    Asm->OutStreamer.EmitCFIStartProc();
98
99  if (!shouldEmitTable)
100    return;
101
102  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
103
104  // Provide LSDA information.
105  unsigned LSDAEncoding = TLOF.getLSDAEncoding();
106  if (LSDAEncoding != dwarf::DW_EH_PE_omit)
107    Asm->OutStreamer.EmitCFILsda(Asm->GetTempSymbol("exception",
108                                                    Asm->getFunctionNumber()),
109                                 LSDAEncoding);
110
111  // Indicate personality routine, if any.
112  unsigned PerEncoding = TLOF.getPersonalityEncoding();
113  const Function *Per = MMI->getPersonalities()[MMI->getPersonalityIndex()];
114  if (PerEncoding == dwarf::DW_EH_PE_omit || !Per)
115    return;
116
117  const MCSymbol *Sym;
118  switch (PerEncoding & 0x70) {
119  default:
120    report_fatal_error("We do not support this DWARF encoding yet!");
121  case dwarf::DW_EH_PE_absptr: {
122    Sym = Asm->Mang->getSymbol(Per);
123    break;
124  }
125  case dwarf::DW_EH_PE_pcrel: {
126    Sym = Asm->GetTempSymbol("personality",
127                             MMI->getPersonalityIndex());
128    break;
129  }
130  }
131  Asm->OutStreamer.EmitCFIPersonality(Sym, PerEncoding);
132}
133
134/// EndFunction - Gather and emit post-function exception information.
135///
136void DwarfCFIException::EndFunction() {
137  if (!shouldEmitMoves && !shouldEmitTable) return;
138
139  if (shouldEmitMoves)
140    Asm->OutStreamer.EmitCFIEndProc();
141
142  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
143                                                Asm->getFunctionNumber()));
144
145  // Map all labels and get rid of any dead landing pads.
146  MMI->TidyLandingPads();
147
148  if (shouldEmitTable)
149    EmitExceptionTable();
150}
151