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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 https://llvm.org/LICENSE.txt 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/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/IR/Function.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
DwarfCFIException::DwarfCFIException(AsmPrinter *A) : EHStreamer(A) {}
DwarfCFIException::~DwarfCFIException() = default;
void DwarfCFIException::addPersonality(const GlobalValue *Personality) {
if (!llvm::is_contained(Personalities, Personality))
Personalities.push_back(Personality);
}
/// 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())
return;
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
unsigned PerEncoding = TLOF.getPersonalityEncoding();
if ((PerEncoding & 0x80) != dwarf::DW_EH_PE_indirect)
return;
// Emit indirect reference table for all used personality functions
for (const GlobalValue *Personality : Personalities) {
MCSymbol *Sym = Asm->getSymbol(Personality);
TLOF.emitPersonalityValue(*Asm->OutStreamer, Asm->getDataLayout(), Sym);
}
Personalities.clear();
}
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 GlobalValue *Per = nullptr;
if (F.hasPersonalityFn())
Per = dyn_cast<GlobalValue>(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
F.needsUnwindTableEntry();
shouldEmitPersonality =
(forceEmitPersonality ||
(hasLandingPads && PerEncoding != dwarf::DW_EH_PE_omit)) &&
Per;
unsigned LSDAEncoding = TLOF.getLSDAEncoding();
shouldEmitLSDA = shouldEmitPersonality &&
LSDAEncoding != dwarf::DW_EH_PE_omit;
const MCAsmInfo &MAI = *MF->getContext().getAsmInfo();
if (MAI.getExceptionHandlingType() != ExceptionHandling::None)
shouldEmitCFI =
MAI.usesCFIForEH() && (shouldEmitPersonality || shouldEmitMoves);
else
shouldEmitCFI = Asm->usesCFIWithoutEH() && shouldEmitMoves;
}
void DwarfCFIException::beginBasicBlockSection(const MachineBasicBlock &MBB) {
if (!shouldEmitCFI)
return;
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 ||
Asm->TM.Options.ForceDwarfFrameSection)
Asm->OutStreamer->emitCFISections(
CFISecType == AsmPrinter::CFISection::EH, true);
hasEmittedCFISections = true;
}
Asm->OutStreamer->emitCFIStartProc(/*IsSimple=*/false);
// Indicate personality routine, if any.
if (!shouldEmitPersonality)
return;
auto &F = MBB.getParent()->getFunction();
auto *P = dyn_cast<GlobalValue>(F.getPersonalityFn()->stripPointerCasts());
assert(P && "Expected personality function");
// Record the personality function.
addPersonality(P);
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(Asm->getMBBExceptionSym(MBB),
TLOF.getLSDAEncoding());
}
void DwarfCFIException::endBasicBlockSection(const MachineBasicBlock &MBB) {
if (shouldEmitCFI)
Asm->OutStreamer->emitCFIEndProc();
}
/// endFunction - Gather and emit post-function exception information.
///
void DwarfCFIException::endFunction(const MachineFunction *MF) {
if (!shouldEmitPersonality)
return;
emitExceptionTable();
}
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