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