DwarfCFIException.cpp revision 360784 
1//===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf 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/BinaryFormat/Dwarf.h"
16#include "llvm/CodeGen/AsmPrinter.h"
17#include "llvm/CodeGen/MachineFunction.h"
18#include "llvm/CodeGen/MachineModuleInfo.h"
19#include "llvm/IR/DataLayout.h"
20#include "llvm/IR/Mangler.h"
21#include "llvm/IR/Module.h"
22#include "llvm/MC/MCAsmInfo.h"
23#include "llvm/MC/MCContext.h"
24#include "llvm/MC/MCExpr.h"
25#include "llvm/MC/MCSection.h"
26#include "llvm/MC/MCStreamer.h"
27#include "llvm/MC/MCSymbol.h"
28#include "llvm/MC/MachineLocation.h"
29#include "llvm/Support/ErrorHandling.h"
30#include "llvm/Support/FormattedStream.h"
31#include "llvm/Target/TargetLoweringObjectFile.h"
32#include "llvm/Target/TargetMachine.h"
33#include "llvm/Target/TargetOptions.h"
34using namespace llvm;
35
36DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A)
37    : EHStreamer(A), shouldEmitCFI(false), hasEmittedCFISections(false) {}
38
39void DwarfCFIExceptionBase::markFunctionEnd() {
40  endFragment();
41
42  // Map all labels and get rid of any dead landing pads.
43  if (!Asm->MF->getLandingPads().empty()) {
44    MachineFunction *NonConstMF = const_cast<MachineFunction*>(Asm->MF);
45    NonConstMF->tidyLandingPads();
46  }
47}
48
49void DwarfCFIExceptionBase::endFragment() {
50  if (shouldEmitCFI)
51    Asm->OutStreamer->EmitCFIEndProc();
52}
53
54DwarfCFIException::DwarfCFIException(AsmPrinter *A)
55    : DwarfCFIExceptionBase(A), shouldEmitPersonality(false),
56      forceEmitPersonality(false), shouldEmitLSDA(false),
57      shouldEmitMoves(false) {}
58
59DwarfCFIException::~DwarfCFIException() {}
60
61/// endModule - Emit all exception information that should come after the
62/// content.
63void DwarfCFIException::endModule() {
64  // SjLj uses this pass and it doesn't need this info.
65  if (!Asm->MAI->usesCFIForEH())
66    return;
67
68  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
69
70  unsigned PerEncoding = TLOF.getPersonalityEncoding();
71
72  if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
73    return;
74
75  // Emit references to all used personality functions
76  for (const Function *Personality : MMI->getPersonalities()) {
77    if (!Personality)
78      continue;
79    MCSymbol *Sym = Asm->getSymbol(Personality);
80    TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym);
81  }
82}
83
84static MCSymbol *getExceptionSym(AsmPrinter *Asm) {
85  return Asm->getCurExceptionSym();
86}
87
88void DwarfCFIException::beginFunction(const MachineFunction *MF) {
89  shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
90  const Function &F = MF->getFunction();
91
92  // If any landing pads survive, we need an EH table.
93  bool hasLandingPads = !MF->getLandingPads().empty();
94
95  // See if we need frame move info.
96  AsmPrinter::CFIMoveType MoveType = Asm->needsCFIMoves();
97
98  shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
99
100  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
101  unsigned PerEncoding = TLOF.getPersonalityEncoding();
102  const Function *Per = nullptr;
103  if (F.hasPersonalityFn())
104    Per = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
105
106  // Emit a personality function even when there are no landing pads
107  forceEmitPersonality =
108      // ...if a personality function is explicitly specified
109      F.hasPersonalityFn() &&
110      // ... and it's not known to be a noop in the absence of invokes
111      !isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
112      // ... and we're not explicitly asked not to emit it
113      F.needsUnwindTableEntry();
114
115  shouldEmitPersonality =
116      (forceEmitPersonality ||
117       (hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) &&
118      Per;
119
120  unsigned LSDAEncoding = TLOF.getLSDAEncoding();
121  shouldEmitLSDA = shouldEmitPersonality &&
122    LSDAEncoding != dwarf::DW_EH_PE_omit;
123
124  shouldEmitCFI = MF->getMMI().getContext().getAsmInfo()->usesCFIForEH() &&
125                  (shouldEmitPersonality || shouldEmitMoves);
126  beginFragment(&*MF->begin(), getExceptionSym);
127}
128
129void DwarfCFIException::beginFragment(const MachineBasicBlock *MBB,
130                                      ExceptionSymbolProvider ESP) {
131  if (!shouldEmitCFI)
132    return;
133
134  if (!hasEmittedCFISections) {
135    if (Asm->needsOnlyDebugCFIMoves())
136      Asm->OutStreamer->EmitCFISections(false, true);
137    else if (Asm->TM.Options.ForceDwarfFrameSection)
138      Asm->OutStreamer->EmitCFISections(true, true);
139    hasEmittedCFISections = true;
140  }
141
142  Asm->OutStreamer->EmitCFIStartProc(/*IsSimple=*/false);
143
144  // Indicate personality routine, if any.
145  if (!shouldEmitPersonality)
146    return;
147
148  auto &F = MBB->getParent()->getFunction();
149  auto *P = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
150  assert(P && "Expected personality function");
151
152  // If we are forced to emit this personality, make sure to record
153  // it because it might not appear in any landingpad
154  if (forceEmitPersonality)
155    MMI->addPersonality(P);
156
157  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
158  unsigned PerEncoding = TLOF.getPersonalityEncoding();
159  const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(P, Asm->TM, MMI);
160  Asm->OutStreamer->EmitCFIPersonality(Sym, PerEncoding);
161
162  // Provide LSDA information.
163  if (shouldEmitLSDA)
164    Asm->OutStreamer->EmitCFILsda(ESP(Asm), TLOF.getLSDAEncoding());
165}
166
167/// endFunction - Gather and emit post-function exception information.
168///
169void DwarfCFIException::endFunction(const MachineFunction *MF) {
170  if (!shouldEmitPersonality)
171    return;
172
173  emitExceptionTable();
174}
175