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