DwarfCFIException.cpp revision e17e6c01c8d64b1081661ff7fbf0355bab75754c 
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    shouldEmitPersonality(false), shouldEmitLSDA(false), shouldEmitMoves(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  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
56
57  unsigned PerEncoding = TLOF.getPersonalityEncoding();
58
59  if ((PerEncoding & 0x70) != dwarf::DW_EH_PE_pcrel)
60    return;
61
62  // Emit references to all used personality functions
63  bool AtLeastOne = false;
64  const std::vector<const Function*> &Personalities = MMI->getPersonalities();
65  for (size_t i = 0, e = Personalities.size(); i != e; ++i) {
66    if (!Personalities[i])
67      continue;
68    MCSymbol *Sym = Asm->Mang->getSymbol(Personalities[i]);
69    TLOF.emitPersonalityValue(Asm->OutStreamer, Asm->TM, Sym);
70    AtLeastOne = true;
71  }
72
73  if (AtLeastOne && !TLOF.isFunctionEHFrameSymbolPrivate()) {
74    // This is a temporary hack to keep sections in the same order they
75    // were before. This lets us produce bit identical outputs while
76    // transitioning to CFI.
77    Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
78  }
79}
80
81/// BeginFunction - Gather pre-function exception information. Assumes it's
82/// being emitted immediately after the function entry point.
83void DwarfCFIException::BeginFunction(const MachineFunction *MF) {
84  shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
85
86  // If any landing pads survive, we need an EH table.
87  bool hasLandingPads = !MMI->getLandingPads().empty();
88
89  // See if we need frame move info.
90  shouldEmitMoves = Asm->needsCFIMoves();
91
92  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
93  unsigned PerEncoding = TLOF.getPersonalityEncoding();
94  const Function *Per = MMI->getPersonalities()[MMI->getPersonalityIndex()];
95
96  shouldEmitPersonality = hasLandingPads &&
97    PerEncoding != dwarf::DW_EH_PE_omit && Per;
98
99  unsigned LSDAEncoding = TLOF.getLSDAEncoding();
100  shouldEmitLSDA = shouldEmitPersonality &&
101    LSDAEncoding != dwarf::DW_EH_PE_omit;
102
103  if (!shouldEmitPersonality && !shouldEmitMoves)
104    return;
105
106  Asm->OutStreamer.EmitCFIStartProc();
107
108  // Indicate personality routine, if any.
109  if (!shouldEmitPersonality)
110    return;
111
112  const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(Per, Asm->Mang, MMI);
113  Asm->OutStreamer.EmitCFIPersonality(Sym, PerEncoding);
114
115  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
116                                                Asm->getFunctionNumber()));
117
118  // Provide LSDA information.
119  if (!shouldEmitLSDA)
120    return;
121
122  Asm->OutStreamer.EmitCFILsda(Asm->GetTempSymbol("exception",
123                                                  Asm->getFunctionNumber()),
124                               LSDAEncoding);
125}
126
127/// EndFunction - Gather and emit post-function exception information.
128///
129void DwarfCFIException::EndFunction() {
130  if (!shouldEmitPersonality && !shouldEmitMoves)
131    return;
132
133  Asm->OutStreamer.EmitCFIEndProc();
134
135  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
136                                                Asm->getFunctionNumber()));
137
138  // Map all labels and get rid of any dead landing pads.
139  MMI->TidyLandingPads();
140
141  if (shouldEmitPersonality)
142    EmitExceptionTable();
143}
144