DwarfCFIException.cpp revision 354c82bdf554bc5e6fa5c77f7c357577860d66d8 
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    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(TLOF.getEHFrameSection());
81  }
82}
83
84/// BeginFunction - Gather pre-function exception information. Assumes it's
85/// being emitted immediately after the function entry point.
86void DwarfCFIException::BeginFunction(const MachineFunction *MF) {
87  shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
88
89  // If any landing pads survive, we need an EH table.
90  bool hasLandingPads = !MMI->getLandingPads().empty();
91
92  // See if we need frame move info.
93  AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
94  if (MoveType == AsmPrinter::CFI_M_EH ||
95      (MoveType == AsmPrinter::CFI_M_Debug &&
96       moveTypeModule == AsmPrinter::CFI_M_None))
97    moveTypeModule = MoveType;
98
99  shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
100
101  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
102  unsigned PerEncoding = TLOF.getPersonalityEncoding();
103  const Function *Per = MMI->getPersonalities()[MMI->getPersonalityIndex()];
104
105  shouldEmitPersonality = hasLandingPads &&
106    PerEncoding != dwarf::DW_EH_PE_omit && Per;
107
108  unsigned LSDAEncoding = TLOF.getLSDAEncoding();
109  shouldEmitLSDA = shouldEmitPersonality &&
110    LSDAEncoding != dwarf::DW_EH_PE_omit;
111
112  if (!shouldEmitPersonality && !shouldEmitMoves)
113    return;
114
115  Asm->OutStreamer.EmitCFIStartProc();
116
117  // Indicate personality routine, if any.
118  if (!shouldEmitPersonality)
119    return;
120
121  const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(Per, Asm->Mang, MMI);
122  Asm->OutStreamer.EmitCFIPersonality(Sym, PerEncoding);
123
124  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
125                                                Asm->getFunctionNumber()));
126
127  // Provide LSDA information.
128  if (!shouldEmitLSDA)
129    return;
130
131  Asm->OutStreamer.EmitCFILsda(Asm->GetTempSymbol("exception",
132                                                  Asm->getFunctionNumber()),
133                               LSDAEncoding);
134}
135
136/// EndFunction - Gather and emit post-function exception information.
137///
138void DwarfCFIException::EndFunction() {
139  if (!shouldEmitPersonality && !shouldEmitMoves)
140    return;
141
142  Asm->OutStreamer.EmitCFIEndProc();
143
144  Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
145                                                Asm->getFunctionNumber()));
146
147  // Map all labels and get rid of any dead landing pads.
148  MMI->TidyLandingPads();
149
150  if (shouldEmitPersonality)
151    EmitExceptionTable();
152}
153