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
AIXException(AsmPrinter * A)24 AIXException::AIXException(AsmPrinter *A) : DwarfCFIExceptionBase(A) {}
25
markFunctionEnd()26 void AIXException::markFunctionEnd() { endFragment(); }
27
emitExceptionInfoTable(const MCSymbol * LSDA,const MCSymbol * PerSym)28 void AIXException::emitExceptionInfoTable(const MCSymbol *LSDA,
29 const MCSymbol *PerSym) {
30 // Generate EH Info Table.
31 // The EH Info Table, aka, 'compat unwind section' on AIX, have the following
32 // format: struct eh_info_t {
33 // unsigned version; /* EH info verion 0 */
34 // #if defined(__64BIT__)
35 // char _pad[4]; /* padding */
36 // #endif
37 // unsigned long lsda; /* Pointer to LSDA */
38 // unsigned long personality; /* Pointer to the personality routine */
39 // }
40
41 auto *EHInfo =
42 cast<MCSectionXCOFF>(Asm->getObjFileLowering().getCompactUnwindSection());
43 if (Asm->TM.getFunctionSections()) {
44 // If option -ffunction-sections is on, append the function name to the
45 // name of EH Info Table csect so that each function has its own EH Info
46 // Table csect. This helps the linker to garbage-collect EH info of unused
47 // functions.
48 SmallString<128> NameStr = EHInfo->getName();
49 raw_svector_ostream(NameStr) << '.' << Asm->MF->getFunction().getName();
50 EHInfo = Asm->OutContext.getXCOFFSection(NameStr, EHInfo->getKind(),
51 EHInfo->getCsectProp());
52 }
53 Asm->OutStreamer->switchSection(EHInfo);
54 MCSymbol *EHInfoLabel =
55 TargetLoweringObjectFileXCOFF::getEHInfoTableSymbol(Asm->MF);
56 Asm->OutStreamer->emitLabel(EHInfoLabel);
57
58 // Version number.
59 Asm->emitInt32(0);
60
61 const DataLayout &DL = MMI->getModule()->getDataLayout();
62 const unsigned PointerSize = DL.getPointerSize();
63
64 // Add necessary paddings in 64 bit mode.
65 Asm->OutStreamer->emitValueToAlignment(PointerSize);
66
67 // LSDA location.
68 Asm->OutStreamer->emitValue(MCSymbolRefExpr::create(LSDA, Asm->OutContext),
69 PointerSize);
70
71 // Personality routine.
72 Asm->OutStreamer->emitValue(MCSymbolRefExpr::create(PerSym, Asm->OutContext),
73 PointerSize);
74 }
75
endFunction(const MachineFunction * MF)76 void AIXException::endFunction(const MachineFunction *MF) {
77 // There is no easy way to access register information in `AIXException`
78 // class. when ShouldEmitEHBlock is false and VRs are saved, A dumy eh info
79 // table are emitted in PPCAIXAsmPrinter::emitFunctionBodyEnd.
80 if (!TargetLoweringObjectFileXCOFF::ShouldEmitEHBlock(MF))
81 return;
82
83 const MCSymbol *LSDALabel = emitExceptionTable();
84
85 const Function &F = MF->getFunction();
86 assert(F.hasPersonalityFn() &&
87 "Landingpads are presented, but no personality routine is found.");
88 const auto *Per =
89 cast<GlobalValue>(F.getPersonalityFn()->stripPointerCasts());
90 const MCSymbol *PerSym = Asm->TM.getSymbol(Per);
91
92 emitExceptionInfoTable(LSDALabel, PerSym);
93 }
94
95 } // End of namespace llvm
96