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/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
  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                                  const MachineBasicBlock *MBB) {
  85   return Asm->getMBBExceptionSym(*MBB);
  86 }
  87
  88 void DwarfCFIException::beginFunction(const MachineFunction *MF) {
  89   shouldEmitPersonality = shouldEmitLSDA = false;
  90   const Function &F = MF->getFunction();
  91
  92   // If any landing pads survive, we need an EH table.
  93   bool hasLandingPads = !MF->getLandingPads().empty();
  94
  95   // See if we need frame move info.
  96   bool shouldEmitMoves =
  97       Asm->getFunctionCFISectionType(*MF) != AsmPrinter::CFISection::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   const MCAsmInfo &MAI = *MF->getMMI().getContext().getAsmInfo();
 124   if (MAI.getExceptionHandlingType() != ExceptionHandling::None)
 125     shouldEmitCFI =
 126         MAI.usesCFIForEH() && (shouldEmitPersonality || shouldEmitMoves);
 127   else
 128     shouldEmitCFI = Asm->needsCFIForDebug() && shouldEmitMoves;
 129
 130   beginFragment(&*MF->begin(), getExceptionSym);
 131 }
 132
 133 void DwarfCFIException::beginFragment(const MachineBasicBlock *MBB,
 134                                       ExceptionSymbolProvider ESP) {
 135   if (!shouldEmitCFI)
 136     return;
 137
 138   if (!hasEmittedCFISections) {
 139     AsmPrinter::CFISection CFISecType = Asm->getModuleCFISectionType();
 140     // If we don't say anything it implies `.cfi_sections .eh_frame`, so we
 141     // chose not to be verbose in that case. And with `ForceDwarfFrameSection`,
 142     // we should always emit .debug_frame.
 143     if (CFISecType == AsmPrinter::CFISection::Debug ||
 144         Asm->TM.Options.ForceDwarfFrameSection)
 145       Asm->OutStreamer->emitCFISections(
 146           CFISecType == AsmPrinter::CFISection::EH, true);
 147     hasEmittedCFISections = true;
 148   }
 149
 150   Asm->OutStreamer->emitCFIStartProc(/*IsSimple=*/false);
 151
 152   // Indicate personality routine, if any.
 153   if (!shouldEmitPersonality)
 154     return;
 155
 156   auto &F = MBB->getParent()->getFunction();
 157   auto *P = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
 158   assert(P && "Expected personality function");
 159
 160   // If we are forced to emit this personality, make sure to record
 161   // it because it might not appear in any landingpad
 162   if (forceEmitPersonality)
 163     MMI->addPersonality(P);
 164
 165   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
 166   unsigned PerEncoding = TLOF.getPersonalityEncoding();
 167   const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(P, Asm->TM, MMI);
 168   Asm->OutStreamer->emitCFIPersonality(Sym, PerEncoding);
 169
 170   // Provide LSDA information.
 171   if (shouldEmitLSDA)
 172     Asm->OutStreamer->emitCFILsda(ESP(Asm, MBB), TLOF.getLSDAEncoding());
 173 }
 174
 175 /// endFunction - Gather and emit post-function exception information.
 176 ///
 177 void DwarfCFIException::endFunction(const MachineFunction *MF) {
 178   if (!shouldEmitPersonality)
 179     return;
 180
 181   emitExceptionTable();
 182 }
 183
 184 void DwarfCFIException::beginBasicBlock(const MachineBasicBlock &MBB) {
 185   beginFragment(&MBB, getExceptionSym);
 186 }
 187
 188 void DwarfCFIException::endBasicBlock(const MachineBasicBlock &MBB) {
 189   if (shouldEmitCFI)
 190     Asm->OutStreamer->emitCFIEndProc();
 191 }