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//===-- CodeGen/AsmPrinter/DwarfException.cpp - Dwarf Exception Impl ------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file contains support for writing DWARF exception info into asm files.
#include "DwarfException.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MachineLocation.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
DwarfCFIExceptionBase::DwarfCFIExceptionBase(AsmPrinter *A)
: EHStreamer(A), shouldEmitCFI(false), hasEmittedCFISections(false) {}
void DwarfCFIExceptionBase::markFunctionEnd() {
// Map all labels and get rid of any dead landing pads.
if (!Asm->MF->getLandingPads().empty()) {
MachineFunction *NonConstMF = const_cast<MachineFunction*>(Asm->MF);
void DwarfCFIExceptionBase::endFragment() {
if (shouldEmitCFI && !Asm->MF->hasBBSections())
DwarfCFIException::DwarfCFIException(AsmPrinter *A)
: DwarfCFIExceptionBase(A), shouldEmitPersonality(false),
forceEmitPersonality(false), shouldEmitLSDA(false) {}
DwarfCFIException::~DwarfCFIException() {}
/// endModule - Emit all exception information that should come after the
/// content.
void DwarfCFIException::endModule() {
// SjLj uses this pass and it doesn't need this info.
if (!Asm->MAI->usesCFIForEH())
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
unsigned PerEncoding = TLOF.getPersonalityEncoding();
if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
// Emit references to all used personality functions
for (const Function *Personality : MMI->getPersonalities()) {
if (!Personality)
MCSymbol *Sym = Asm->getSymbol(Personality);
TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym);
static MCSymbol *getExceptionSym(AsmPrinter *Asm,
const MachineBasicBlock *MBB) {
return Asm->getMBBExceptionSym(*MBB);
void DwarfCFIException::beginFunction(const MachineFunction *MF) {
shouldEmitPersonality = shouldEmitLSDA = false;
const Function &F = MF->getFunction();
// If any landing pads survive, we need an EH table.
bool hasLandingPads = !MF->getLandingPads().empty();
// See if we need frame move info.
bool shouldEmitMoves =
Asm->getFunctionCFISectionType(*MF) != AsmPrinter::CFISection::None;
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
unsigned PerEncoding = TLOF.getPersonalityEncoding();
const Function *Per = nullptr;
if (F.hasPersonalityFn())
Per = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
// Emit a personality function even when there are no landing pads
forceEmitPersonality =
// ...if a personality function is explicitly specified
F.hasPersonalityFn() &&
// ... and it's not known to be a noop in the absence of invokes
!isNoOpWithoutInvoke(classifyEHPersonality(Per)) &&
// ... and we're not explicitly asked not to emit it
shouldEmitPersonality =
(forceEmitPersonality ||
(hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) &&
unsigned LSDAEncoding = TLOF.getLSDAEncoding();
shouldEmitLSDA = shouldEmitPersonality &&
LSDAEncoding != dwarf::DW_EH_PE_omit;
const MCAsmInfo &MAI = *MF->getMMI().getContext().getAsmInfo();
if (MAI.getExceptionHandlingType() != ExceptionHandling::None)
shouldEmitCFI =
MAI.usesCFIForEH() && (shouldEmitPersonality || shouldEmitMoves);
shouldEmitCFI = Asm->needsCFIForDebug() && shouldEmitMoves;
beginFragment(&*MF->begin(), getExceptionSym);
void DwarfCFIException::beginFragment(const MachineBasicBlock *MBB,
ExceptionSymbolProvider ESP) {
if (!shouldEmitCFI)
if (!hasEmittedCFISections) {
AsmPrinter::CFISection CFISecType = Asm->getModuleCFISectionType();
// If we don't say anything it implies `.cfi_sections .eh_frame`, so we
// chose not to be verbose in that case. And with `ForceDwarfFrameSection`,
// we should always emit .debug_frame.
if (CFISecType == AsmPrinter::CFISection::Debug ||
CFISecType == AsmPrinter::CFISection::EH, true);
hasEmittedCFISections = true;
// Indicate personality routine, if any.
if (!shouldEmitPersonality)
auto &F = MBB->getParent()->getFunction();
auto *P = dyn_cast<Function>(F.getPersonalityFn()->stripPointerCasts());
assert(P && "Expected personality function");
// If we are forced to emit this personality, make sure to record
// it because it might not appear in any landingpad
if (forceEmitPersonality)
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
unsigned PerEncoding = TLOF.getPersonalityEncoding();
const MCSymbol *Sym = TLOF.getCFIPersonalitySymbol(P, Asm->TM, MMI);
Asm->OutStreamer->emitCFIPersonality(Sym, PerEncoding);
// Provide LSDA information.
if (shouldEmitLSDA)
Asm->OutStreamer->emitCFILsda(ESP(Asm, MBB), TLOF.getLSDAEncoding());
/// endFunction - Gather and emit post-function exception information.
void DwarfCFIException::endFunction(const MachineFunction *MF) {
if (!shouldEmitPersonality)
void DwarfCFIException::beginBasicBlock(const MachineBasicBlock &MBB) {
beginFragment(&MBB, getExceptionSym);
void DwarfCFIException::endBasicBlock(const MachineBasicBlock &MBB) {
if (shouldEmitCFI)