llvm/lib/CodeGen/AsmPrinter/AIXException.cpp

   1 //===-- CodeGen/AsmPrinter/AIXException.cpp - AIX 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 AIX exception info into asm files.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "DwarfException.h"
  14 #include "llvm/CodeGen/AsmPrinter.h"
  15 #include "llvm/CodeGen/MachineModuleInfo.h"
  16 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
  17 #include "llvm/IR/Module.h"
  18 #include "llvm/MC/MCSectionXCOFF.h"
  19 #include "llvm/MC/MCStreamer.h"
  20 #include "llvm/Target/TargetLoweringObjectFile.h"
  21 #include "llvm/Target/TargetMachine.h"
  22
  23 namespace llvm {
  24
  25 AIXException::AIXException(AsmPrinter *A) : EHStreamer(A) {}
  26
  27 void AIXException::emitExceptionInfoTable(const MCSymbol *LSDA,
  28                                           const MCSymbol *PerSym) {
  29   // Generate EH Info Table.
  30   // The EH Info Table, aka, 'compat unwind section' on AIX, have the following
  31   // format: struct eh_info_t {
  32   //   unsigned version;           /* EH info verion 0 */
  33   // #if defined(__64BIT__)
  34   //   char _pad[4];               /* padding */
  35   // #endif
  36   //   unsigned long lsda;         /* Pointer to LSDA */
  37   //   unsigned long personality;  /* Pointer to the personality routine */
  38   //   }
  39
  40   auto *EHInfo =
  41       cast<MCSectionXCOFF>(Asm->getObjFileLowering().getCompactUnwindSection());
  42   if (Asm->TM.getFunctionSections()) {
  43     // If option -ffunction-sections is on, append the function name to the
  44     // name of EH Info Table csect so that each function has its own EH Info
  45     // Table csect. This helps the linker to garbage-collect EH info of unused
  46     // functions.
  47     SmallString<128> NameStr = EHInfo->getName();
  48     raw_svector_ostream(NameStr) << '.' << Asm->MF->getFunction().getName();
  49     EHInfo = Asm->OutContext.getXCOFFSection(NameStr, EHInfo->getKind(),
  50                                              EHInfo->getCsectProp());
  51   }
  52   Asm->OutStreamer->switchSection(EHInfo);
  53   MCSymbol *EHInfoLabel =
  54       TargetLoweringObjectFileXCOFF::getEHInfoTableSymbol(Asm->MF);
  55   Asm->OutStreamer->emitLabel(EHInfoLabel);
  56
  57   // Version number.
  58   Asm->emitInt32(0);
  59
  60   const DataLayout &DL = MMI->getModule()->getDataLayout();
  61   const unsigned PointerSize = DL.getPointerSize();
  62
  63   // Add necessary paddings in 64 bit mode.
  64   Asm->OutStreamer->emitValueToAlignment(Align(PointerSize));
  65
  66   // LSDA location.
  67   Asm->OutStreamer->emitValue(MCSymbolRefExpr::create(LSDA, Asm->OutContext),
  68                               PointerSize);
  69
  70   // Personality routine.
  71   Asm->OutStreamer->emitValue(MCSymbolRefExpr::create(PerSym, Asm->OutContext),
  72                               PointerSize);
  73 }
  74
  75 void AIXException::endFunction(const MachineFunction *MF) {
  76   // There is no easy way to access register information in `AIXException`
  77   // class. when ShouldEmitEHBlock is false and VRs are saved, A dumy eh info
  78   // table are emitted in PPCAIXAsmPrinter::emitFunctionBodyEnd.
  79   if (!TargetLoweringObjectFileXCOFF::ShouldEmitEHBlock(MF))
  80     return;
  81
  82   const MCSymbol *LSDALabel = emitExceptionTable();
  83
  84   const Function &F = MF->getFunction();
  85   assert(F.hasPersonalityFn() &&
  86          "Landingpads are presented, but no personality routine is found.");
  87   const auto *Per =
  88       cast<GlobalValue>(F.getPersonalityFn()->stripPointerCasts());
  89   const MCSymbol *PerSym = Asm->TM.getSymbol(Per);
  90
  91   emitExceptionInfoTable(LSDALabel, PerSym);
  92 }
  93
  94 } // End of namespace llvm