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 DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A)
43     : EHStreamer(A), shouldEmitCFI(false) {}
44 
45 void DwarfCFIExceptionBase::markFunctionEnd() {
46   if (shouldEmitCFI)
47     Asm->OutStreamer->EmitCFIEndProc();
48 
49   if (MMI->getLandingPads().empty())
50     return;
51 
52   // Map all labels and get rid of any dead landing pads.
53   MMI->TidyLandingPads();
54 }
55 
56 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
57     : DwarfCFIExceptionBase(A), shouldEmitPersonality(false),
58       shouldEmitLSDA(false), shouldEmitMoves(false),
59       moveTypeModule(AsmPrinter::CFI_M_None) {}
60 
61 DwarfCFIException::~DwarfCFIException() {}
62 
63 /// endModule - Emit all exception information that should come after the
64 /// content.
65 void DwarfCFIException::endModule() {
66   if (moveTypeModule == AsmPrinter::CFI_M_Debug)
67     Asm->OutStreamer->EmitCFISections(false, true);
68 
69   // SjLj uses this pass and it doesn't need this info.
70   if (!Asm->MAI->usesCFIForEH())
71     return;
72 
73   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
74 
75   unsigned PerEncoding = TLOF.getPersonalityEncoding();
76 
77   if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
78     return;
79 
80   // Emit references to all used personality functions
81   const std::vector<const Function*> &Personalities = MMI->getPersonalities();
82   for (size_t i = 0, e = Personalities.size(); i != e; ++i) {
83     if (!Personalities[i])
84       continue;
85     MCSymbol *Sym = Asm->getSymbol(Personalities[i]);
86     TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym);
87   }
88 }
89 
90 void DwarfCFIException::beginFunction(const MachineFunction *MF) {
91   shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
92   const Function *F = MF->getFunction();
93 
94   // If any landing pads survive, we need an EH table.
95   bool hasLandingPads = !MMI->getLandingPads().empty();
96 
97   // See if we need frame move info.
98   AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
99   if (MoveType == AsmPrinter::CFI_M_EH ||
100       (MoveType == AsmPrinter::CFI_M_Debug &&
101        moveTypeModule == AsmPrinter::CFI_M_None))
102     moveTypeModule = MoveType;
103 
104   shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
105 
106   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
107   unsigned PerEncoding = TLOF.getPersonalityEncoding();
108   const Function *Per = nullptr;
109   if (F->hasPersonalityFn())
110     Per = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
111   assert(!MMI->getPersonality() || Per == MMI->getPersonality());
112 
113   // Emit a personality function even when there are no landing pads
114   bool forceEmitPersonality =
115       // ...if a personality function is explicitly specified
116       F->hasPersonalityFn() &&
117       // ... and it's not known to be a noop in the absence of invokes
118       !isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
119       // ... and we're not explicitly asked not to emit it
120       F->needsUnwindTableEntry();
121 
122   shouldEmitPersonality =
123       (forceEmitPersonality ||
124        (hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) &&
125       Per;
126 
127   unsigned LSDAEncoding = TLOF.getLSDAEncoding();
128   shouldEmitLSDA = shouldEmitPersonality &&
129     LSDAEncoding != dwarf::DW_EH_PE_omit;
130 
131   shouldEmitCFI = shouldEmitPersonality || shouldEmitMoves;
132   if (!shouldEmitCFI)
133     return;
134 
135   Asm->OutStreamer->EmitCFIStartProc(/*IsSimple=*/false);
136 
137   // Indicate personality routine, if any.
138   if (!shouldEmitPersonality)
139     return;
140 
141   // If we are forced to emit this personality, make sure to record
142   // it because it might not appear in any landingpad
143   if (forceEmitPersonality)
144     MMI->addPersonality(Per);
145 
146   const MCSymbol *Sym =
147       TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, MMI);
148   Asm->OutStreamer->EmitCFIPersonality(Sym, PerEncoding);
149 
150   // Provide LSDA information.
151   if (!shouldEmitLSDA)
152     return;
153 
154   Asm->OutStreamer->EmitCFILsda(Asm->getCurExceptionSym(), LSDAEncoding);
155 }
156 
157 /// endFunction - Gather and emit post-function exception information.
158 ///
159 void DwarfCFIException::endFunction(const MachineFunction *) {
160   if (!shouldEmitPersonality)
161     return;
162 
163   emitExceptionTable();
164 }
165