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/FormattedStream.h"
36 #include "llvm/ADT/SmallString.h"
37 #include "llvm/ADT/StringExtras.h"
38 #include "llvm/ADT/Twine.h"
39 using namespace llvm;
40 
41 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
42   : DwarfException(A),
43     shouldEmitTable(false), shouldEmitMoves(false), shouldEmitTableModule(false)
44     {}
45 
46 DwarfCFIException::~DwarfCFIException() {}
47 
48 /// EndModule - Emit all exception information that should come after the
49 /// content.
50 void DwarfCFIException::EndModule() {
51   if (!Asm->MAI->isExceptionHandlingDwarf())
52     return;
53 
54   if (!shouldEmitTableModule)
55     return;
56 
57   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
58   unsigned PerEncoding = TLOF.getPersonalityEncoding();
59 
60   // Begin eh frame section.
61   Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
62 
63   // Emit references to all used personality functions
64   const std::vector<const Function*> &Personalities = MMI->getPersonalities();
65   for (size_t i = 0, e = Personalities.size(); i != e; ++i) {
66     Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("personality", i));
67     Asm->EmitReference(Personalities[i], PerEncoding);
68   }
69 }
70 
71 /// BeginFunction - Gather pre-function exception information. Assumes it's
72 /// being emitted immediately after the function entry point.
73 void DwarfCFIException::BeginFunction(const MachineFunction *MF) {
74   shouldEmitTable = shouldEmitMoves = false;
75 
76   // If any landing pads survive, we need an EH table.
77   shouldEmitTable = !MMI->getLandingPads().empty();
78 
79   // See if we need frame move info.
80   shouldEmitMoves =
81     !Asm->MF->getFunction()->doesNotThrow() || UnwindTablesMandatory;
82 
83   if (shouldEmitMoves || shouldEmitTable)
84     // Assumes in correct section after the entry point.
85     Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
86                                                   Asm->getFunctionNumber()));
87 
88   shouldEmitTableModule |= shouldEmitTable;
89 
90   if (shouldEmitMoves) {
91     const TargetFrameLowering *TFL = Asm->TM.getFrameLowering();
92     Asm->OutStreamer.EmitCFIStartProc();
93 
94     // Indicate locations of general callee saved registers in frame.
95     std::vector<MachineMove> Moves;
96     TFL->getInitialFrameState(Moves);
97     Asm->EmitCFIFrameMoves(Moves);
98     Asm->EmitCFIFrameMoves(MMI->getFrameMoves());
99   }
100 
101   if (!shouldEmitTable)
102     return;
103 
104   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
105 
106   // Provide LSDA information.
107   unsigned LSDAEncoding = TLOF.getLSDAEncoding();
108   if (LSDAEncoding != dwarf::DW_EH_PE_omit)
109     Asm->OutStreamer.EmitCFILsda(Asm->GetTempSymbol("exception",
110                                                     Asm->getFunctionNumber()),
111                                  LSDAEncoding);
112 
113   // Indicate personality routine, if any.
114   unsigned PerEncoding = TLOF.getPersonalityEncoding();
115   if (PerEncoding != dwarf::DW_EH_PE_omit &&
116       MMI->getPersonalities()[MMI->getPersonalityIndex()])
117     Asm->OutStreamer.EmitCFIPersonality(Asm->GetTempSymbol("personality",
118                                                     MMI->getPersonalityIndex()),
119                                         PerEncoding);
120 }
121 
122 /// EndFunction - Gather and emit post-function exception information.
123 ///
124 void DwarfCFIException::EndFunction() {
125   if (!shouldEmitMoves && !shouldEmitTable) return;
126 
127   if (shouldEmitMoves)
128     Asm->OutStreamer.EmitCFIEndProc();
129 
130   Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
131                                                 Asm->getFunctionNumber()));
132 
133   // Map all labels and get rid of any dead landing pads.
134   MMI->TidyLandingPads();
135 
136   if (shouldEmitTable)
137     EmitExceptionTable();
138 }
139