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/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 }