LLVM  8.0.0svn
DwarfCFIException.cpp
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1 //===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains support for writing DWARF exception info into asm files.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "DwarfException.h"
15 #include "llvm/ADT/Twine.h"
20 #include "llvm/IR/DataLayout.h"
21 #include "llvm/IR/Mangler.h"
22 #include "llvm/IR/Module.h"
23 #include "llvm/MC/MCAsmInfo.h"
24 #include "llvm/MC/MCContext.h"
25 #include "llvm/MC/MCExpr.h"
26 #include "llvm/MC/MCSection.h"
27 #include "llvm/MC/MCStreamer.h"
28 #include "llvm/MC/MCSymbol.h"
34 using namespace llvm;
35 
37  : EHStreamer(A), shouldEmitCFI(false), hasEmittedCFISections(false) {}
38 
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 
50  if (shouldEmitCFI)
51  Asm->OutStreamer->EmitCFIEndProc();
52 }
53 
55  : DwarfCFIExceptionBase(A), shouldEmitPersonality(false),
56  forceEmitPersonality(false), shouldEmitLSDA(false),
57  shouldEmitMoves(false) {}
58 
60 
61 /// endModule - Emit all exception information that should come after the
62 /// content.
64  // SjLj uses this pass and it doesn't need this info.
65  if (!Asm->MAI->usesCFIForEH())
66  return;
67 
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);
81  }
82 }
83 
85  return Asm->getCurExceptionSym();
86 }
87 
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.
97 
98  shouldEmitMoves = MoveType != AsmPrinter::CFI_M_None;
99 
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
112  // ... and we're not explicitly asked not to emit it
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 
125  (shouldEmitPersonality || shouldEmitMoves);
127 }
128 
131  if (!shouldEmitCFI)
132  return;
133 
134  if (!hasEmittedCFISections) {
136  Asm->OutStreamer->EmitCFISections(false, true);
137  hasEmittedCFISections = true;
138  }
139 
140  Asm->OutStreamer->EmitCFIStartProc(/*IsSimple=*/false);
141 
142  // Indicate personality routine, if any.
143  if (!shouldEmitPersonality)
144  return;
145 
146  auto &F = MBB->getParent()->getFunction();
147  auto *P = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
148  assert(P && "Expected personality function");
149 
150  // If we are forced to emit this personality, make sure to record
151  // it because it might not appear in any landingpad
152  if (forceEmitPersonality)
153  MMI->addPersonality(P);
154 
156  unsigned PerEncoding = TLOF.getPersonalityEncoding();
157  const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(P, Asm->TM, MMI);
158  Asm->OutStreamer->EmitCFIPersonality(Sym, PerEncoding);
159 
160  // Provide LSDA information.
161  if (shouldEmitLSDA)
162  Asm->OutStreamer->EmitCFILsda(ESP(Asm), TLOF.getLSDAEncoding());
163 }
164 
165 /// endFunction - Gather and emit post-function exception information.
166 ///
168  if (!shouldEmitPersonality)
169  return;
170 
172 }
const MCAsmInfo * getAsmInfo() const
Definition: MCContext.h:293
const TargetLoweringObjectFile & getObjFileLowering() const
Return information about object file lowering.
Definition: AsmPrinter.cpp:210
std::unique_ptr< MCStreamer > OutStreamer
This is the MCStreamer object for the file we are generating.
Definition: AsmPrinter.h:93
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
virtual void emitPersonalityValue(MCStreamer &Streamer, const DataLayout &TM, const MCSymbol *Sym) const
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:42
bool needsOnlyDebugCFIMoves() const
Returns false if needsCFIMoves() == CFI_M_EH for any function in the module.
Definition: AsmPrinter.h:320
CFIMoveType needsCFIMoves() const
Definition: AsmPrinter.cpp:952
void beginFragment(const MachineBasicBlock *MBB, ExceptionSymbolProvider ESP) override
bool shouldEmitCFI
Per-function flag to indicate if frame CFI info should be emitted.
F(f)
MachineFunction * MF
The current machine function.
Definition: AsmPrinter.h:96
MachineModuleInfo & getMMI() const
DwarfCFIException(AsmPrinter *A)
MachineModuleInfo * MMI
Collected machine module information.
Definition: EHStreamer.h:37
Emits exception handling directives.
Definition: EHStreamer.h:31
void endFunction(const MachineFunction *) override
Gather and emit post-function exception information.
void emitExceptionTable()
Emit landing pads and actions.
Definition: EHStreamer.cpp:347
const MCContext & getContext() const
bool hasPersonalityFn() const
Check whether this function has a personality function.
Definition: Function.h:702
void beginFunction(const MachineFunction *MF) override
Gather pre-function exception information.
#define P(N)
const MCAsmInfo * MAI
Target Asm Printer information.
Definition: AsmPrinter.h:84
void addPersonality(const Function *Personality)
Provide the personality function for the exception information.
TargetMachine & TM
Target machine description.
Definition: AsmPrinter.h:81
This class is intended to be used as a driving class for all asm writers.
Definition: AsmPrinter.h:78
EHPersonality classifyEHPersonality(const Value *Pers)
See if the given exception handling personality function is one that we understand.
const Constant * stripPointerCasts() const
Definition: Constant.h:173
AsmPrinter * Asm
Target of directive emission.
Definition: EHStreamer.h:34
bool hasEmittedCFISections
Per-module flag to indicate if .cfi_section has beeen emitted.
const std::vector< LandingPadInfo > & getLandingPads() const
Return a reference to the landing pad info for the current function.
MCSymbol * getSymbol(const GlobalValue *GV) const
Definition: AsmPrinter.cpp:428
static MCSymbol * getExceptionSym(AsmPrinter *Asm)
Module.h This file contains the declarations for the Module class.
MCSymbol * ExceptionSymbolProvider(AsmPrinter *Asm)
const Function & getFunction() const
Return the LLVM function that this machine code represents.
bool usesCFIForEH() const
Returns true if the exception handling method for the platform uses call frame information to unwind...
Definition: MCAsmInfo.h:579
bool needsUnwindTableEntry() const
True if this function needs an unwind table.
Definition: Function.h:573
This file contains constants used for implementing Dwarf debug support.
MCSymbol * getCurExceptionSym()
void endModule() override
Emit all exception information that should come after the content.
const MachineFunction * getParent() const
Return the MachineFunction containing this basic block.
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
const std::vector< const Function * > & getPersonalities() const
Return array of personality functions ever seen.
Constant * getPersonalityFn() const
Get the personality function associated with this function.
Definition: Function.cpp:1302
const DataLayout & getDataLayout() const
Return information about data layout.
Definition: AsmPrinter.cpp:214
virtual MCSymbol * getCFIPersonalitySymbol(const GlobalValue *GV, const TargetMachine &TM, MachineModuleInfo *MMI) const
bool isNoOpWithoutInvoke(EHPersonality Pers)
Return true if this personality may be safely removed if there are no invoke instructions remaining i...
void tidyLandingPads(DenseMap< MCSymbol *, uintptr_t > *LPMap=nullptr)
Remap landing pad labels and remove any deleted landing pads.