llvm/lib/CodeGen/AsmPrinter/DwarfCFIException.cpp

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