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"
40 using namespace llvm;
41 
42 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
43   : DwarfException(A),
44     shouldEmitPersonality(false), shouldEmitLSDA(false), shouldEmitMoves(false)
45     {}
46 
47 DwarfCFIException::~DwarfCFIException() {}
48 
49 /// EndModule - Emit all exception information that should come after the
50 /// content.
51 void 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.
83 void 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 ///
129 void 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