1 //===-- CodeGen/AsmPrinter/ARMException.cpp - ARM EHABI 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 DWARF exception info into asm files.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "DwarfException.h"
14 #include "llvm/ADT/Twine.h"
15 #include "llvm/CodeGen/AsmPrinter.h"
16 #include "llvm/CodeGen/MachineFunction.h"
17 #include "llvm/IR/Function.h"
18 #include "llvm/MC/MCAsmInfo.h"
19 #include "llvm/MC/MCStreamer.h"
20 using namespace llvm;
21 
ARMException(AsmPrinter * A)22 ARMException::ARMException(AsmPrinter *A) : EHStreamer(A) {}
23 
24 ARMException::~ARMException() = default;
25 
getTargetStreamer()26 ARMTargetStreamer &ARMException::getTargetStreamer() {
27   MCTargetStreamer &TS = *Asm->OutStreamer->getTargetStreamer();
28   return static_cast<ARMTargetStreamer &>(TS);
29 }
30 
beginFunction(const MachineFunction * MF)31 void ARMException::beginFunction(const MachineFunction *MF) {
32   if (Asm->MAI->getExceptionHandlingType() == ExceptionHandling::ARM)
33     getTargetStreamer().emitFnStart();
34   // See if we need call frame info.
35   AsmPrinter::CFISection CFISecType = Asm->getFunctionCFISectionType(*MF);
36   assert(CFISecType != AsmPrinter::CFISection::EH &&
37          "non-EH CFI not yet supported in prologue with EHABI lowering");
38 
39   if (CFISecType == AsmPrinter::CFISection::Debug) {
40     if (!hasEmittedCFISections) {
41       if (Asm->getModuleCFISectionType() == AsmPrinter::CFISection::Debug)
42         Asm->OutStreamer->emitCFISections(false, true);
43       hasEmittedCFISections = true;
44     }
45 
46     shouldEmitCFI = true;
47     Asm->OutStreamer->emitCFIStartProc(false);
48   }
49 }
50 
markFunctionEnd()51 void ARMException::markFunctionEnd() {
52   if (shouldEmitCFI)
53     Asm->OutStreamer->emitCFIEndProc();
54 }
55 
56 /// endFunction - Gather and emit post-function exception information.
57 ///
endFunction(const MachineFunction * MF)58 void ARMException::endFunction(const MachineFunction *MF) {
59   ARMTargetStreamer &ATS = getTargetStreamer();
60   const Function &F = MF->getFunction();
61   const Function *Per = nullptr;
62   if (F.hasPersonalityFn())
63     Per = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
64   bool forceEmitPersonality =
65     F.hasPersonalityFn() && !isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
66     F.needsUnwindTableEntry();
67   bool shouldEmitPersonality = forceEmitPersonality ||
68     !MF->getLandingPads().empty();
69   if (!Asm->MF->getFunction().needsUnwindTableEntry() &&
70       !shouldEmitPersonality)
71     ATS.emitCantUnwind();
72   else if (shouldEmitPersonality) {
73     // Emit references to personality.
74     if (Per) {
75       MCSymbol *PerSym = Asm->getSymbol(Per);
76       ATS.emitPersonality(PerSym);
77     }
78 
79     // Emit .handlerdata directive.
80     ATS.emitHandlerData();
81 
82     // Emit actual exception table
83     emitExceptionTable();
84   }
85 
86   if (Asm->MAI->getExceptionHandlingType() == ExceptionHandling::ARM)
87     ATS.emitFnEnd();
88 }
89 
emitTypeInfos(unsigned TTypeEncoding,MCSymbol * TTBaseLabel)90 void ARMException::emitTypeInfos(unsigned TTypeEncoding,
91                                  MCSymbol *TTBaseLabel) {
92   const MachineFunction *MF = Asm->MF;
93   const std::vector<const GlobalValue *> &TypeInfos = MF->getTypeInfos();
94   const std::vector<unsigned> &FilterIds = MF->getFilterIds();
95 
96   bool VerboseAsm = Asm->OutStreamer->isVerboseAsm();
97 
98   int Entry = 0;
99   // Emit the Catch TypeInfos.
100   if (VerboseAsm && !TypeInfos.empty()) {
101     Asm->OutStreamer->AddComment(">> Catch TypeInfos <<");
102     Asm->OutStreamer->addBlankLine();
103     Entry = TypeInfos.size();
104   }
105 
106   for (const GlobalValue *GV : reverse(TypeInfos)) {
107     if (VerboseAsm)
108       Asm->OutStreamer->AddComment("TypeInfo " + Twine(Entry--));
109     Asm->emitTTypeReference(GV, TTypeEncoding);
110   }
111 
112   Asm->OutStreamer->emitLabel(TTBaseLabel);
113 
114   // Emit the Exception Specifications.
115   if (VerboseAsm && !FilterIds.empty()) {
116     Asm->OutStreamer->AddComment(">> Filter TypeInfos <<");
117     Asm->OutStreamer->addBlankLine();
118     Entry = 0;
119   }
120   for (std::vector<unsigned>::const_iterator
121          I = FilterIds.begin(), E = FilterIds.end(); I < E; ++I) {
122     unsigned TypeID = *I;
123     if (VerboseAsm) {
124       --Entry;
125       if (TypeID != 0)
126         Asm->OutStreamer->AddComment("FilterInfo " + Twine(Entry));
127     }
128 
129     Asm->emitTTypeReference((TypeID == 0 ? nullptr : TypeInfos[TypeID - 1]),
130                             TTypeEncoding);
131   }
132 }
133