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) : EHStreamer(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   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 
74 void 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