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/BinaryFormat/Dwarf.h"
15#include "llvm/CodeGen/AsmPrinter.h"
16#include "llvm/CodeGen/MachineFunction.h"
17#include "llvm/CodeGen/MachineModuleInfo.h"
18#include "llvm/MC/MCAsmInfo.h"
19#include "llvm/MC/MCContext.h"
20#include "llvm/MC/MCStreamer.h"
21#include "llvm/Target/TargetLoweringObjectFile.h"
22#include "llvm/Target/TargetMachine.h"
23#include "llvm/Target/TargetOptions.h"
24using namespace llvm;
25
26DwarfCFIException::DwarfCFIException(AsmPrinter *A) : EHStreamer(A) {}
27
28DwarfCFIException::~DwarfCFIException() = default;
29
30void DwarfCFIException::addPersonality(const GlobalValue *Personality) {
31 if (!llvm::is_contained(Range&: Personalities, Element: Personality))
32 Personalities.push_back(x: Personality);
33}
34
35/// endModule - Emit all exception information that should come after the
36/// content.
37void DwarfCFIException::endModule() {
38 // SjLj uses this pass and it doesn't need this info.
39 if (!Asm->MAI->usesCFIForEH())
40 return;
41
42 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
43
44 unsigned PerEncoding = TLOF.getPersonalityEncoding();
45
46 if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
47 return;
48
49 // Emit indirect reference table for all used personality functions
50 for (const GlobalValue *Personality : Personalities) {
51 MCSymbol *Sym = Asm->getSymbol(GV: Personality);
52 TLOF.emitPersonalityValue(Streamer&: *Asm->OutStreamer, TM: Asm->getDataLayout(), Sym);
53 }
54 Personalities.clear();
55}
56
57void DwarfCFIException::beginFunction(const MachineFunction *MF) {
58 shouldEmitPersonality = shouldEmitLSDA = false;
59 const Function &F = MF->getFunction();
60
61 // If any landing pads survive, we need an EH table.
62 bool hasLandingPads = !MF->getLandingPads().empty();
63
64 // See if we need frame move info.
65 bool shouldEmitMoves =
66 Asm->getFunctionCFISectionType(MF: *MF) != AsmPrinter::CFISection::None;
67
68 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
69 unsigned PerEncoding = TLOF.getPersonalityEncoding();
70 const GlobalValue *Per = nullptr;
71 if (F.hasPersonalityFn())
72 Per = dyn_cast<GlobalValue>(Val: F.getPersonalityFn()->stripPointerCasts());
73
74 // Emit a personality function even when there are no landing pads
75 forceEmitPersonality =
76 // ...if a personality function is explicitly specified
77 F.hasPersonalityFn() &&
78 // ... and it's not known to be a noop in the absence of invokes
79 !isNoOpWithoutInvoke(Pers: classifyEHPersonality(Pers: Per)) &&
80 // ... and we're not explicitly asked not to emit it
81 F.needsUnwindTableEntry();
82
83 shouldEmitPersonality =
84 (forceEmitPersonality ||
85 (hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) &&
86 Per;
87
88 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
89 shouldEmitLSDA = shouldEmitPersonality &&
90 LSDAEncoding != dwarf::DW_EH_PE_omit;
91
92 const MCAsmInfo &MAI = *MF->getMMI().getContext().getAsmInfo();
93 if (MAI.getExceptionHandlingType() != ExceptionHandling::None)
94 shouldEmitCFI =
95 MAI.usesCFIForEH() && (shouldEmitPersonality || shouldEmitMoves);
96 else
97 shouldEmitCFI = Asm->usesCFIWithoutEH() && shouldEmitMoves;
98}
99
100void DwarfCFIException::beginBasicBlockSection(const MachineBasicBlock &MBB) {
101 if (!shouldEmitCFI)
102 return;
103
104 if (!hasEmittedCFISections) {
105 AsmPrinter::CFISection CFISecType = Asm->getModuleCFISectionType();
106 // If we don't say anything it implies `.cfi_sections .eh_frame`, so we
107 // chose not to be verbose in that case. And with `ForceDwarfFrameSection`,
108 // we should always emit .debug_frame.
109 if (CFISecType == AsmPrinter::CFISection::Debug ||
110 Asm->TM.Options.ForceDwarfFrameSection)
111 Asm->OutStreamer->emitCFISections(
112 EH: CFISecType == AsmPrinter::CFISection::EH, Debug: true);
113 hasEmittedCFISections = true;
114 }
115
116 Asm->OutStreamer->emitCFIStartProc(/*IsSimple=*/false);
117
118 // Indicate personality routine, if any.
119 if (!shouldEmitPersonality)
120 return;
121
122 auto &F = MBB.getParent()->getFunction();
123 auto *P = dyn_cast<GlobalValue>(Val: F.getPersonalityFn()->stripPointerCasts());
124 assert(P && "Expected personality function");
125 // Record the personality function.
126 addPersonality(Personality: P);
127
128 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
129 unsigned PerEncoding = TLOF.getPersonalityEncoding();
130 const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(GV: P, TM: Asm->TM, MMI);
131 Asm->OutStreamer->emitCFIPersonality(Sym, Encoding: PerEncoding);
132
133 // Provide LSDA information.
134 if (shouldEmitLSDA)
135 Asm->OutStreamer->emitCFILsda(Sym: Asm->getMBBExceptionSym(MBB),
136 Encoding: TLOF.getLSDAEncoding());
137}
138
139void DwarfCFIException::endBasicBlockSection(const MachineBasicBlock &MBB) {
140 if (shouldEmitCFI)
141 Asm->OutStreamer->emitCFIEndProc();
142}
143
144/// endFunction - Gather and emit post-function exception information.
145///
146void DwarfCFIException::endFunction(const MachineFunction *MF) {
147 if (!shouldEmitPersonality)
148 return;
149
150 emitExceptionTable();
151}
152

source code of llvm/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp