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 
22 namespace llvm {
23 
24 AIXException::AIXException(AsmPrinter *A) : DwarfCFIExceptionBase(A) {}
25 
26 void 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   Asm->OutStreamer->SwitchSection(
40       Asm->getObjFileLowering().getCompactUnwindSection());
41   MCSymbol *EHInfoLabel =
42       TargetLoweringObjectFileXCOFF::getEHInfoTableSymbol(Asm->MF);
43   Asm->OutStreamer->emitLabel(EHInfoLabel);
44 
45   // Version number.
46   Asm->emitInt32(0);
47 
48   const DataLayout &DL = MMI->getModule()->getDataLayout();
49   const unsigned PointerSize = DL.getPointerSize();
50 
51   // Add necessary paddings in 64 bit mode.
52   Asm->OutStreamer->emitValueToAlignment(PointerSize);
53 
54   // LSDA location.
55   Asm->OutStreamer->emitValue(MCSymbolRefExpr::create(LSDA, Asm->OutContext),
56                               PointerSize);
57 
58   // Personality routine.
59   Asm->OutStreamer->emitValue(MCSymbolRefExpr::create(PerSym, Asm->OutContext),
60                               PointerSize);
61 }
62 
63 void AIXException::endFunction(const MachineFunction *MF) {
64   // There is no easy way to access register information in `AIXException`
65   // class. when ShouldEmitEHBlock is false and VRs are saved, A dumy eh info
66   // table are emitted in PPCAIXAsmPrinter::emitFunctionBodyEnd.
67   if (!TargetLoweringObjectFileXCOFF::ShouldEmitEHBlock(MF))
68     return;
69 
70   const MCSymbol *LSDALabel = emitExceptionTable();
71 
72   const Function &F = MF->getFunction();
73   assert(F.hasPersonalityFn() &&
74          "Landingpads are presented, but no personality routine is found.");
75   const GlobalValue *Per =
76       dyn_cast<GlobalValue>(F.getPersonalityFn()->stripPointerCasts());
77   const MCSymbol *PerSym = Asm->TM.getSymbol(Per);
78 
79   emitExceptionInfoTable(LSDALabel, PerSym);
80 }
81 
82 } // End of namespace llvm
83