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/TargetOptions.h" 33 using namespace llvm; 34 35 DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A) 36 : EHStreamer(A), shouldEmitCFI(false), hasEmittedCFISections(false) {} 37 38 void DwarfCFIExceptionBase::markFunctionEnd() { 39 endFragment(); 40 41 // Map all labels and get rid of any dead landing pads. 42 if (!Asm->MF->getLandingPads().empty()) { 43 MachineFunction *NonConstMF = const_cast<MachineFunction*>(Asm->MF); 44 NonConstMF->tidyLandingPads(); 45 } 46 } 47 48 void DwarfCFIExceptionBase::endFragment() { 49 if (shouldEmitCFI) 50 Asm->OutStreamer->EmitCFIEndProc(); 51 } 52 53 DwarfCFIException::DwarfCFIException(AsmPrinter *A) 54 : DwarfCFIExceptionBase(A), shouldEmitPersonality(false), 55 forceEmitPersonality(false), shouldEmitLSDA(false), 56 shouldEmitMoves(false) {} 57 58 DwarfCFIException::~DwarfCFIException() {} 59 60 /// endModule - Emit all exception information that should come after the 61 /// content. 62 void DwarfCFIException::endModule() { 63 // SjLj uses this pass and it doesn't need this info. 64 if (!Asm->MAI->usesCFIForEH()) 65 return; 66 67 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); 68 69 unsigned PerEncoding = TLOF.getPersonalityEncoding(); 70 71 if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect) 72 return; 73 74 // Emit references to all used personality functions 75 for (const Function *Personality : MMI->getPersonalities()) { 76 if (!Personality) 77 continue; 78 MCSymbol *Sym = Asm->getSymbol(Personality); 79 TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym); 80 } 81 } 82 83 static MCSymbol *getExceptionSym(AsmPrinter *Asm) { 84 return Asm->getCurExceptionSym(); 85 } 86 87 void DwarfCFIException::beginFunction(const MachineFunction *MF) { 88 shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false; 89 const Function &F = MF->getFunction(); 90 91 // If any landing pads survive, we need an EH table. 92 bool hasLandingPads = !MF->getLandingPads().empty(); 93 94 // See if we need frame move info. 95 AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves(); 96 97 shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None; 98 99 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); 100 unsigned PerEncoding = TLOF.getPersonalityEncoding(); 101 const Function *Per = nullptr; 102 if (F.hasPersonalityFn()) 103 Per = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts()); 104 105 // Emit a personality function even when there are no landing pads 106 forceEmitPersonality = 107 // ...if a personality function is explicitly specified 108 F.hasPersonalityFn() && 109 // ... and it's not known to be a noop in the absence of invokes 110 !isNoOpWithoutInvoke(classifyEHPersonality(Per)) && 111 // ... and we're not explicitly asked not to emit it 112 F.needsUnwindTableEntry(); 113 114 shouldEmitPersonality = 115 (forceEmitPersonality || 116 (hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) && 117 Per; 118 119 unsigned LSDAEncoding = TLOF.getLSDAEncoding(); 120 shouldEmitLSDA = shouldEmitPersonality && 121 LSDAEncoding != dwarf::DW_EH_PE_omit; 122 123 shouldEmitCFI = MF->getMMI().getContext().getAsmInfo()->usesCFIForEH() && 124 (shouldEmitPersonality || shouldEmitMoves); 125 beginFragment(&*MF->begin(), getExceptionSym); 126 } 127 128 void DwarfCFIException::beginFragment(const MachineBasicBlock *MBB, 129 ExceptionSymbolProvider ESP) { 130 if (!shouldEmitCFI) 131 return; 132 133 if (!hasEmittedCFISections) { 134 if (Asm->needsOnlyDebugCFIMoves()) 135 Asm->OutStreamer->EmitCFISections(false, true); 136 hasEmittedCFISections = true; 137 } 138 139 Asm->OutStreamer->EmitCFIStartProc(/*IsSimple=*/false); 140 141 // Indicate personality routine, if any. 142 if (!shouldEmitPersonality) 143 return; 144 145 auto &F = MBB->getParent()->getFunction(); 146 auto *P = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts()); 147 assert(P && "Expected personality function"); 148 149 // If we are forced to emit this personality, make sure to record 150 // it because it might not appear in any landingpad 151 if (forceEmitPersonality) 152 MMI->addPersonality(P); 153 154 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering(); 155 unsigned PerEncoding = TLOF.getPersonalityEncoding(); 156 const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(P, Asm->TM, MMI); 157 Asm->OutStreamer->EmitCFIPersonality(Sym, PerEncoding); 158 159 // Provide LSDA information. 160 if (shouldEmitLSDA) 161 Asm->OutStreamer->EmitCFILsda(ESP(Asm), TLOF.getLSDAEncoding()); 162 } 163 164 /// endFunction - Gather and emit post-function exception information. 165 /// 166 void DwarfCFIException::endFunction(const MachineFunction *MF) { 167 if (!shouldEmitPersonality) 168 return; 169 170 emitExceptionTable(); 171 } 172