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/IR/DataLayout.h"
23 #include "llvm/IR/Module.h"
24 #include "llvm/MC/MCAsmInfo.h"
25 #include "llvm/MC/MCContext.h"
26 #include "llvm/MC/MCExpr.h"
27 #include "llvm/MC/MCSection.h"
28 #include "llvm/MC/MCStreamer.h"
29 #include "llvm/MC/MCSymbol.h"
30 #include "llvm/MC/MachineLocation.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"
40 using namespace llvm;
41
DwarfCFIException(AsmPrinter * A)42 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
43 : DwarfException(A),
44 shouldEmitPersonality(false), shouldEmitLSDA(false), shouldEmitMoves(false),
45 moveTypeModule(AsmPrinter::CFI_M_None) {}
46
~DwarfCFIException()47 DwarfCFIException::~DwarfCFIException() {}
48
49 /// EndModule - Emit all exception information that should come after the
50 /// content.
EndModule()51 void 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.
BeginFunction(const MachineFunction * MF)87 void 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 ///
EndFunction()140 void 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