1 //===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file contains support for writing DWARF exception info into asm files.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "DwarfException.h"
14 #include "llvm/ADT/Twine.h"
15 #include "llvm/BinaryFormat/Dwarf.h"
16 #include "llvm/CodeGen/AsmPrinter.h"
17 #include "llvm/CodeGen/MachineFunction.h"
18 #include "llvm/CodeGen/MachineModuleInfo.h"
19 #include "llvm/IR/DataLayout.h"
20 #include "llvm/IR/Mangler.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/MC/MCContext.h"
24 #include "llvm/MC/MCExpr.h"
25 #include "llvm/MC/MCSection.h"
26 #include "llvm/MC/MCStreamer.h"
27 #include "llvm/MC/MCSymbol.h"
28 #include "llvm/MC/MachineLocation.h"
29 #include "llvm/Support/ErrorHandling.h"
30 #include "llvm/Support/FormattedStream.h"
31 #include "llvm/Target/TargetLoweringObjectFile.h"
32 #include "llvm/Target/TargetMachine.h"
33 #include "llvm/Target/TargetOptions.h"
34 using namespace llvm;
35
DwarfCFIExceptionBase(AsmPrinter * A)36 DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A)
37 : EHStreamer(A), shouldEmitCFI(false), hasEmittedCFISections(false) {}
38
markFunctionEnd()39 void DwarfCFIExceptionBase::markFunctionEnd() {
40 endFragment();
41
42 // Map all labels and get rid of any dead landing pads.
43 if (!Asm->MF->getLandingPads().empty()) {
44 MachineFunction *NonConstMF = const_cast<MachineFunction*>(Asm->MF);
45 NonConstMF->tidyLandingPads();
46 }
47 }
48
endFragment()49 void DwarfCFIExceptionBase::endFragment() {
50 if (shouldEmitCFI && !Asm->MF->hasBBSections())
51 Asm->OutStreamer->emitCFIEndProc();
52 }
53
DwarfCFIException(AsmPrinter * A)54 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
55 : DwarfCFIExceptionBase(A), shouldEmitPersonality(false),
56 forceEmitPersonality(false), shouldEmitLSDA(false),
57 shouldEmitMoves(false) {}
58
~DwarfCFIException()59 DwarfCFIException::~DwarfCFIException() {}
60
61 /// endModule - Emit all exception information that should come after the
62 /// content.
endModule()63 void DwarfCFIException::endModule() {
64 // SjLj uses this pass and it doesn't need this info.
65 if (!Asm->MAI->usesCFIForEH())
66 return;
67
68 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
69
70 unsigned PerEncoding = TLOF.getPersonalityEncoding();
71
72 if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
73 return;
74
75 // Emit references to all used personality functions
76 for (const Function *Personality : MMI->getPersonalities()) {
77 if (!Personality)
78 continue;
79 MCSymbol *Sym = Asm->getSymbol(Personality);
80 TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym);
81 }
82 }
83
getExceptionSym(AsmPrinter * Asm,const MachineBasicBlock * MBB)84 static MCSymbol *getExceptionSym(AsmPrinter *Asm,
85 const MachineBasicBlock *MBB) {
86 return Asm->getMBBExceptionSym(*MBB);
87 }
88
beginFunction(const MachineFunction * MF)89 void DwarfCFIException::beginFunction(const MachineFunction *MF) {
90 shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
91 const Function &F = MF->getFunction();
92
93 // If any landing pads survive, we need an EH table.
94 bool hasLandingPads = !MF->getLandingPads().empty();
95
96 // See if we need frame move info.
97 AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
98
99 shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
100
101 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
102 unsigned PerEncoding = TLOF.getPersonalityEncoding();
103 const Function *Per = nullptr;
104 if (F.hasPersonalityFn())
105 Per = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
106
107 // Emit a personality function even when there are no landing pads
108 forceEmitPersonality =
109 // ...if a personality function is explicitly specified
110 F.hasPersonalityFn() &&
111 // ... and it's not known to be a noop in the absence of invokes
112 !isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
113 // ... and we're not explicitly asked not to emit it
114 F.needsUnwindTableEntry();
115
116 shouldEmitPersonality =
117 (forceEmitPersonality ||
118 (hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) &&
119 Per;
120
121 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
122 shouldEmitLSDA = shouldEmitPersonality &&
123 LSDAEncoding != dwarf::DW_EH_PE_omit;
124
125 shouldEmitCFI = MF->getMMI().getContext().getAsmInfo()->usesCFIForEH() &&
126 (shouldEmitPersonality || shouldEmitMoves);
127 beginFragment(&*MF->begin(), getExceptionSym);
128 }
129
beginFragment(const MachineBasicBlock * MBB,ExceptionSymbolProvider ESP)130 void DwarfCFIException::beginFragment(const MachineBasicBlock *MBB,
131 ExceptionSymbolProvider ESP) {
132 if (!shouldEmitCFI)
133 return;
134
135 if (!hasEmittedCFISections) {
136 if (Asm->needsOnlyDebugCFIMoves())
137 Asm->OutStreamer->emitCFISections(false, true);
138 else if (Asm->TM.Options.ForceDwarfFrameSection)
139 Asm->OutStreamer->emitCFISections(true, true);
140 hasEmittedCFISections = true;
141 }
142
143 Asm->OutStreamer->emitCFIStartProc(/*IsSimple=*/false);
144
145 // Indicate personality routine, if any.
146 if (!shouldEmitPersonality)
147 return;
148
149 auto &F = MBB->getParent()->getFunction();
150 auto *P = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
151 assert(P && "Expected personality function");
152
153 // If we are forced to emit this personality, make sure to record
154 // it because it might not appear in any landingpad
155 if (forceEmitPersonality)
156 MMI->addPersonality(P);
157
158 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
159 unsigned PerEncoding = TLOF.getPersonalityEncoding();
160 const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(P, Asm->TM, MMI);
161 Asm->OutStreamer->emitCFIPersonality(Sym, PerEncoding);
162
163 // Provide LSDA information.
164 if (shouldEmitLSDA)
165 Asm->OutStreamer->emitCFILsda(ESP(Asm, MBB), TLOF.getLSDAEncoding());
166 }
167
168 /// endFunction - Gather and emit post-function exception information.
169 ///
endFunction(const MachineFunction * MF)170 void DwarfCFIException::endFunction(const MachineFunction *MF) {
171 if (!shouldEmitPersonality)
172 return;
173
174 emitExceptionTable();
175 }
176
beginBasicBlock(const MachineBasicBlock & MBB)177 void DwarfCFIException::beginBasicBlock(const MachineBasicBlock &MBB) {
178 beginFragment(&MBB, getExceptionSym);
179 }
180
endBasicBlock(const MachineBasicBlock & MBB)181 void DwarfCFIException::endBasicBlock(const MachineBasicBlock &MBB) {
182 if (shouldEmitCFI)
183 Asm->OutStreamer->emitCFIEndProc();
184 }
185