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 36 DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A) 37 : EHStreamer(A), shouldEmitCFI(false), hasEmittedCFISections(false) {} 38 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 49 void DwarfCFIExceptionBase::endFragment() { 50 if (shouldEmitCFI && !Asm->MF->hasBBSections()) 51 Asm->OutStreamer->emitCFIEndProc(); 52 } 53 54 DwarfCFIException::DwarfCFIException(AsmPrinter *A) 55 : DwarfCFIExceptionBase(A), shouldEmitPersonality(false), 56 forceEmitPersonality(false), shouldEmitLSDA(false), 57 shouldEmitMoves(false) {} 58 59 DwarfCFIException::~DwarfCFIException() {} 60 61 /// endModule - Emit all exception information that should come after the 62 /// content. 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 84 static MCSymbol *getExceptionSym(AsmPrinter *Asm, 85 const MachineBasicBlock *MBB) { 86 return Asm->getMBBExceptionSym(*MBB); 87 } 88 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 } 129 130 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 /// 170 void DwarfCFIException::endFunction(const MachineFunction *MF) { 171 if (!shouldEmitPersonality) 172 return; 173 174 emitExceptionTable(); 175 } 176 177 void DwarfCFIException::beginBasicBlock(const MachineBasicBlock &MBB) { 178 beginFragment(&MBB, getExceptionSym); 179 } 180 181 void DwarfCFIException::endBasicBlock(const MachineBasicBlock &MBB) { 182 if (shouldEmitCFI) 183 Asm->OutStreamer->emitCFIEndProc(); 184 } 185