DwarfCFIException.cpp revision 2c3a4641a7785da78839caf574277df9cd93b52c 
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/ADT/SmallString.h"
16#include "llvm/ADT/StringExtras.h"
17#include "llvm/ADT/Twine.h"
18#include "llvm/CodeGen/AsmPrinter.h"
19#include "llvm/CodeGen/MachineFrameInfo.h"
20#include "llvm/CodeGen/MachineFunction.h"
21#include "llvm/CodeGen/MachineModuleInfo.h"
22#include "llvm/DataLayout.h"
23#include "llvm/MC/MCAsmInfo.h"
24#include "llvm/MC/MCContext.h"
25#include "llvm/MC/MCExpr.h"
26#include "llvm/MC/MCSection.h"
27#include "llvm/MC/MCStreamer.h"
28#include "llvm/MC/MCSymbol.h"
29#include "llvm/MC/MachineLocation.h"
30#include "llvm/Module.h"
31#include "llvm/Support/Dwarf.h"
32#include "llvm/Support/ErrorHandling.h"
33#include "llvm/Support/FormattedStream.h"
34#include "llvm/Target/Mangler.h"
35#include "llvm/Target/TargetFrameLowering.h"
36#include "llvm/Target/TargetLoweringObjectFile.h"
37#include "llvm/Target/TargetMachine.h"
38#include "llvm/Target/TargetOptions.h"
39#include "llvm/Target/TargetRegisterInfo.h"
40using namespace llvm;
41
42DwarfCFIException::DwarfCFIException(AsmPrinter *A)
43  : DwarfException(A),
44    shouldEmitPersonality(false), shouldEmitLSDA(false), shouldEmitMoves(false),
45    moveTypeModule(AsmPrinter::CFI_M_None) {}
46
47DwarfCFIException::~DwarfCFIException() {}
48
49/// EndModule - Emit all exception information that should come after the
50/// content.
51void DwarfCFIException::EndModule() {
52  if (moveTypeModule == AsmPrinter::CFI_M_Debug)
53    Asm->OutStreamer.EmitCFISections(false, true);
54
55  if (!Asm->MAI->isExceptionHandlingDwarf())
56    return;
57
58  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
59
60  unsigned PerEncoding = TLOF.getPersonalityEncoding();
61
62  if ((PerEncoding & 0x70) != dwarf::DW_EH_PE_pcrel)
63    return;
64
65  // Emit references to all used personality functions
66  bool AtLeastOne = false;
67  const std::vector<const Function*> &Personalities = MMI->getPersonalities();
68  for (size_t i = 0, e = Personalities.size(); i != e; ++i) {
69    if (!Personalities[i])
70      continue;
71    MCSymbol *Sym = Asm->Mang->getSymbol(Personalities[i]);
72    TLOF.emitPersonalityValue(Asm->OutStreamer, Asm->TM, Sym);
73    AtLeastOne = true;
74  }
75
76  if (AtLeastOne && !TLOF.isFunctionEHFrameSymbolPrivate()) {
77    // This is a temporary hack to keep sections in the same order they
78    // were before. This lets us produce bit identical outputs while
79    // transitioning to CFI.
80    Asm->OutStreamer.SwitchSection(
81               const_cast<TargetLoweringObjectFile&>(TLOF).getEHFrameSection());
82  }
83}
84
85/// BeginFunction - Gather pre-function exception information. Assumes it's
86/// being emitted immediately after the function entry point.
87void DwarfCFIException::BeginFunction(const MachineFunction *MF) {
88  shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
89
90  // If any landing pads survive, we need an EH table.
91  bool hasLandingPads = !MMI->getLandingPads().empty();
92
93  // See if we need frame move info.
94  AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
95  if (MoveType == AsmPrinter::CFI_M_EH ||
96      (MoveType == AsmPrinter::CFI_M_Debug &&
97       moveTypeModule == AsmPrinter::CFI_M_None))
98    moveTypeModule = MoveType;
99
100  shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
101
102  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
103  unsigned PerEncoding = TLOF.getPersonalityEncoding();
104  const Function *Per = MMI->getPersonalities()[MMI->getPersonalityIndex()];
105
106  shouldEmitPersonality = hasLandingPads &&
107    PerEncoding != dwarf::DW_EH_PE_omit && Per;
108
109  unsigned LSDAEncoding = TLOF.getLSDAEncoding();
110  shouldEmitLSDA = shouldEmitPersonality &&
111    LSDAEncoding != dwarf::DW_EH_PE_omit;
112
113  if (!shouldEmitPersonality && !shouldEmitMoves)
114    return;
115
116  Asm->OutStreamer.EmitCFIStartProc();
117
118  // Indicate personality routine, if any.
119  if (!shouldEmitPersonality)
120    return;
121
122  const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(Per, Asm->Mang, MMI);
123  Asm->OutStreamer.EmitCFIPersonality(Sym, PerEncoding);
124
125  Asm->OutStreamer.EmitDebugLabel
126    (Asm->GetTempSymbol("eh_func_begin",
127                        Asm->getFunctionNumber()));
128
129  // Provide LSDA information.
130  if (!shouldEmitLSDA)
131    return;
132
133  Asm->OutStreamer.EmitCFILsda(Asm->GetTempSymbol("exception",
134                                                  Asm->getFunctionNumber()),
135                               LSDAEncoding);
136}
137
138/// EndFunction - Gather and emit post-function exception information.
139///
140void DwarfCFIException::EndFunction() {
141  if (!shouldEmitPersonality && !shouldEmitMoves)
142    return;
143
144  Asm->OutStreamer.EmitCFIEndProc();
145
146  if (!shouldEmitPersonality)
147    return;
148
149  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
150                                                Asm->getFunctionNumber()));
151
152  // Map all labels and get rid of any dead landing pads.
153  MMI->TidyLandingPads();
154
155  EmitExceptionTable();
156}
157