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/Mangler.h"
24 #include "llvm/IR/Module.h"
25 #include "llvm/MC/MCAsmInfo.h"
26 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCExpr.h"
28 #include "llvm/MC/MCSection.h"
29 #include "llvm/MC/MCStreamer.h"
30 #include "llvm/MC/MCSymbol.h"
31 #include "llvm/MC/MachineLocation.h"
32 #include "llvm/Support/Dwarf.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/FormattedStream.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 
42 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
43   : EHStreamer(A), shouldEmitPersonality(false), shouldEmitLSDA(false),
44     shouldEmitMoves(false), moveTypeModule(AsmPrinter::CFI_M_None) {}
45 
46 DwarfCFIException::~DwarfCFIException() {}
47 
48 /// endModule - Emit all exception information that should come after the
49 /// content.
50 void DwarfCFIException::endModule() {
51   if (moveTypeModule == AsmPrinter::CFI_M_Debug)
52     Asm->OutStreamer.EmitCFISections(false, true);
53 
54   if (!Asm->MAI->isExceptionHandlingDwarf())
55     return;
56 
57   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
58 
59   unsigned PerEncoding = TLOF.getPersonalityEncoding();
60 
61   if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
62     return;
63 
64   // Emit references to all used personality functions
65   bool AtLeastOne = false;
66   const std::vector<const Function*> &Personalities = MMI->getPersonalities();
67   for (size_t i = 0, e = Personalities.size(); i != e; ++i) {
68     if (!Personalities[i])
69       continue;
70     MCSymbol *Sym = Asm->getSymbol(Personalities[i]);
71     TLOF.emitPersonalityValue(Asm->OutStreamer, Asm->TM, Sym);
72     AtLeastOne = true;
73   }
74 
75   if (AtLeastOne && !TLOF.isFunctionEHFrameSymbolPrivate()) {
76     // This is a temporary hack to keep sections in the same order they
77     // were before. This lets us produce bit identical outputs while
78     // transitioning to CFI.
79     Asm->OutStreamer.SwitchSection(
80                const_cast<TargetLoweringObjectFile&>(TLOF).getEHFrameSection());
81   }
82 }
83 
84 /// beginFunction - Gather pre-function exception information. Assumes it's
85 /// being emitted immediately after the function entry point.
86 void 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(/*IsSimple=*/false);
116 
117   // Indicate personality routine, if any.
118   if (!shouldEmitPersonality)
119     return;
120 
121   const MCSymbol *Sym =
122       TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, 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 ///
140 void DwarfCFIException::endFunction(const MachineFunction *) {
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