lib/CodeGen/AsmPrinter/DwarfCFIException.cpp

   1 //===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file contains support for writing DWARF exception info into asm files.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "DwarfException.h"
  15 #include "llvm/Module.h"
  16 #include "llvm/CodeGen/AsmPrinter.h"
  17 #include "llvm/CodeGen/MachineModuleInfo.h"
  18 #include "llvm/CodeGen/MachineFrameInfo.h"
  19 #include "llvm/CodeGen/MachineFunction.h"
  20 #include "llvm/CodeGen/MachineLocation.h"
  21 #include "llvm/MC/MCAsmInfo.h"
  22 #include "llvm/MC/MCContext.h"
  23 #include "llvm/MC/MCExpr.h"
  24 #include "llvm/MC/MCSection.h"
  25 #include "llvm/MC/MCStreamer.h"
  26 #include "llvm/MC/MCSymbol.h"
  27 #include "llvm/Target/Mangler.h"
  28 #include "llvm/Target/TargetData.h"
  29 #include "llvm/Target/TargetFrameLowering.h"
  30 #include "llvm/Target/TargetLoweringObjectFile.h"
  31 #include "llvm/Target/TargetMachine.h"
  32 #include "llvm/Target/TargetOptions.h"
  33 #include "llvm/Target/TargetRegisterInfo.h"
  34 #include "llvm/Support/Dwarf.h"
  35 #include "llvm/Support/ErrorHandling.h"
  36 #include "llvm/Support/FormattedStream.h"
  37 #include "llvm/ADT/SmallString.h"
  38 #include "llvm/ADT/StringExtras.h"
  39 #include "llvm/ADT/Twine.h"
  40 using namespace llvm;
  41
  42 DwarfCFIException::DwarfCFIException(AsmPrinter *A)
  43   : DwarfException(A),
  44     shouldEmitPersonality(false), shouldEmitLSDA(false), shouldEmitMoves(false),
  45     moveTypeModule(AsmPrinter::CFI_M_None) {}
  46
  47 DwarfCFIException::~DwarfCFIException() {}
  48
  49 /// EndModule - Emit all exception information that should come after the
  50 /// content.
  51 void DwarfCFIException::EndModule() {
  52   if (moveTypeModule == AsmPrinter::CFI_M_Debug)
  53     Asm->OutStreamer.EmitCFISections(false, true);
  54
  55   if (!Asm->MAI->isExceptionHandlingDwarf())
  56     return;
  57
  58   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
  59
  60   unsigned PerEncoding = TLOF.getPersonalityEncoding();
  61
  62   if ((PerEncoding & 0x70) != dwarf::DW_EH_PE_pcrel)
  63     return;
  64
  65   // Emit references to all used personality functions
  66   bool AtLeastOne = false;
  67   const std::vector<const Function*> &Personalities = MMI->getPersonalities();
  68   for (size_t i = 0, e = Personalities.size(); i != e; ++i) {
  69     if (!Personalities[i])
  70       continue;
  71     MCSymbol *Sym = Asm->Mang->getSymbol(Personalities[i]);
  72     TLOF.emitPersonalityValue(Asm->OutStreamer, Asm->TM, Sym);
  73     AtLeastOne = true;
  74   }
  75
  76   if (AtLeastOne && !TLOF.isFunctionEHFrameSymbolPrivate()) {
  77     // This is a temporary hack to keep sections in the same order they
  78     // were before. This lets us produce bit identical outputs while
  79     // transitioning to CFI.
  80     Asm->OutStreamer.SwitchSection(TLOF.getEHFrameSection());
  81   }
  82 }
  83
  84 /// BeginFunction - Gather pre-function exception information. Assumes it's
  85 /// being emitted immediately after the function entry point.
  86 void DwarfCFIException::BeginFunction(const MachineFunction *MF) {
  87   shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
  88
  89   // If any landing pads survive, we need an EH table.
  90   bool hasLandingPads = !MMI->getLandingPads().empty();
  91
  92   // See if we need frame move info.
  93   AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
  94   if (MoveType == AsmPrinter::CFI_M_EH ||
  95       (MoveType == AsmPrinter::CFI_M_Debug &&
  96        moveTypeModule == AsmPrinter::CFI_M_None))
  97     moveTypeModule = MoveType;
  98
  99   shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
 100
 101   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
 102   unsigned PerEncoding = TLOF.getPersonalityEncoding();
 103   const Function *Per = MMI->getPersonalities()[MMI->getPersonalityIndex()];
 104
 105   shouldEmitPersonality = hasLandingPads &&
 106     PerEncoding != dwarf::DW_EH_PE_omit && Per;
 107
 108   unsigned LSDAEncoding = TLOF.getLSDAEncoding();
 109   shouldEmitLSDA = shouldEmitPersonality &&
 110     LSDAEncoding != dwarf::DW_EH_PE_omit;
 111
 112   if (!shouldEmitPersonality && !shouldEmitMoves)
 113     return;
 114
 115   Asm->OutStreamer.EmitCFIStartProc();
 116
 117   // Indicate personality routine, if any.
 118   if (!shouldEmitPersonality)
 119     return;
 120
 121   const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(Per, Asm->Mang, MMI);
 122   Asm->OutStreamer.EmitCFIPersonality(Sym, PerEncoding);
 123
 124   Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_begin",
 125                                                 Asm->getFunctionNumber()));
 126
 127   // Provide LSDA information.
 128   if (!shouldEmitLSDA)
 129     return;
 130
 131   Asm->OutStreamer.EmitCFILsda(Asm->GetTempSymbol("exception",
 132                                                   Asm->getFunctionNumber()),
 133                                LSDAEncoding);
 134 }
 135
 136 /// EndFunction - Gather and emit post-function exception information.
 137 ///
 138 void DwarfCFIException::EndFunction() {
 139   if (!shouldEmitPersonality && !shouldEmitMoves)
 140     return;
 141
 142   Asm->OutStreamer.EmitCFIEndProc();
 143
 144   Asm->OutStreamer.EmitLabel(Asm->GetTempSymbol("eh_func_end",
 145                                                 Asm->getFunctionNumber()));
 146
 147   // Map all labels and get rid of any dead landing pads.
 148   MMI->TidyLandingPads();
 149
 150   if (shouldEmitPersonality)
 151     EmitExceptionTable();
 152 }