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/StringExtras.h"
16 #include "llvm/ADT/Twine.h"
17 #include "llvm/CodeGen/AsmPrinter.h"
18 #include "llvm/CodeGen/MachineFrameInfo.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/CodeGen/MachineModuleInfo.h"
21 #include "llvm/IR/DataLayout.h"
22 #include "llvm/IR/Mangler.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/TargetFrameLowering.h"
35 #include "llvm/Target/TargetLoweringObjectFile.h"
36 #include "llvm/Target/TargetMachine.h"
37 #include "llvm/Target/TargetOptions.h"
38 #include "llvm/Target/TargetRegisterInfo.h"
39 using namespace llvm;
40
DwarfCFIExceptionBase(AsmPrinter * A)41 DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A)
42 : EHStreamer(A), shouldEmitCFI(false) {}
43
markFunctionEnd()44 void DwarfCFIExceptionBase::markFunctionEnd() {
45 endFragment();
46
47 if (MMI->getLandingPads().empty())
48 return;
49
50 // Map all labels and get rid of any dead landing pads.
51 MMI->TidyLandingPads();
52 }
53
endFragment()54 void DwarfCFIExceptionBase::endFragment() {
55 if (shouldEmitCFI)
56 Asm->OutStreamer->EmitCFIEndProc();
57 }
58
DwarfCFIException(AsmPrinter * A)59 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
60 : DwarfCFIExceptionBase(A), shouldEmitPersonality(false),
61 forceEmitPersonality(false), shouldEmitLSDA(false),
62 shouldEmitMoves(false), moveTypeModule(AsmPrinter::CFI_M_None) {}
63
~DwarfCFIException()64 DwarfCFIException::~DwarfCFIException() {}
65
66 /// endModule - Emit all exception information that should come after the
67 /// content.
endModule()68 void DwarfCFIException::endModule() {
69 if (moveTypeModule == AsmPrinter::CFI_M_Debug)
70 Asm->OutStreamer->EmitCFISections(false, true);
71
72 // SjLj uses this pass and it doesn't need this info.
73 if (!Asm->MAI->usesCFIForEH())
74 return;
75
76 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
77
78 unsigned PerEncoding = TLOF.getPersonalityEncoding();
79
80 if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
81 return;
82
83 // Emit references to all used personality functions
84 for (const Function *Personality : MMI->getPersonalities()) {
85 if (!Personality)
86 continue;
87 MCSymbol *Sym = Asm->getSymbol(Personality);
88 TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym);
89 }
90 }
91
getExceptionSym(AsmPrinter * Asm)92 static MCSymbol *getExceptionSym(AsmPrinter *Asm) {
93 return Asm->getCurExceptionSym();
94 }
95
beginFunction(const MachineFunction * MF)96 void DwarfCFIException::beginFunction(const MachineFunction *MF) {
97 shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
98 const Function *F = MF->getFunction();
99
100 // If any landing pads survive, we need an EH table.
101 bool hasLandingPads = !MMI->getLandingPads().empty();
102
103 // See if we need frame move info.
104 AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
105 if (MoveType == AsmPrinter::CFI_M_EH ||
106 (MoveType == AsmPrinter::CFI_M_Debug &&
107 moveTypeModule == AsmPrinter::CFI_M_None))
108 moveTypeModule = MoveType;
109
110 shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
111
112 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
113 unsigned PerEncoding = TLOF.getPersonalityEncoding();
114 const Function *Per = nullptr;
115 if (F->hasPersonalityFn())
116 Per = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
117
118 // Emit a personality function even when there are no landing pads
119 forceEmitPersonality =
120 // ...if a personality function is explicitly specified
121 F->hasPersonalityFn() &&
122 // ... and it's not known to be a noop in the absence of invokes
123 !isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
124 // ... and we're not explicitly asked not to emit it
125 F->needsUnwindTableEntry();
126
127 shouldEmitPersonality =
128 (forceEmitPersonality ||
129 (hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) &&
130 Per;
131
132 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
133 shouldEmitLSDA = shouldEmitPersonality &&
134 LSDAEncoding != dwarf::DW_EH_PE_omit;
135
136 shouldEmitCFI = shouldEmitPersonality || shouldEmitMoves;
137 beginFragment(&*MF->begin(), getExceptionSym);
138 }
139
beginFragment(const MachineBasicBlock * MBB,ExceptionSymbolProvider ESP)140 void DwarfCFIException::beginFragment(const MachineBasicBlock *MBB,
141 ExceptionSymbolProvider ESP) {
142 if (!shouldEmitCFI)
143 return;
144
145 Asm->OutStreamer->EmitCFIStartProc(/*IsSimple=*/false);
146
147 // Indicate personality routine, if any.
148 if (!shouldEmitPersonality)
149 return;
150
151 auto *F = MBB->getParent()->getFunction();
152 auto *P = dyn_cast<Function>(F->getPersonalityFn()->stripPointerCasts());
153 assert(P && "Expected personality function");
154
155 // If we are forced to emit this personality, make sure to record
156 // it because it might not appear in any landingpad
157 if (forceEmitPersonality)
158 MMI->addPersonality(P);
159
160 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
161 unsigned PerEncoding = TLOF.getPersonalityEncoding();
162 const MCSymbol *Sym =
163 TLOF.getCFIPersonalitySymbol(P, *Asm->Mang, Asm->TM, MMI);
164 Asm->OutStreamer->EmitCFIPersonality(Sym, PerEncoding);
165
166 // Provide LSDA information.
167 if (shouldEmitLSDA)
168 Asm->OutStreamer->EmitCFILsda(ESP(Asm), TLOF.getLSDAEncoding());
169 }
170
171 /// endFunction - Gather and emit post-function exception information.
172 ///
endFunction(const MachineFunction *)173 void DwarfCFIException::endFunction(const MachineFunction *) {
174 if (!shouldEmitPersonality)
175 return;
176
177 emitExceptionTable();
178 }
179