blob: c33f7e957b54a6c8a11e4e8341a34c14aefc2274 [file] [log] [blame]
//===- lib/MC/AArch64ELFStreamer.cpp - ELF Object Output for AArch64 ------===//
// 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 assembles .s files and emits AArch64 ELF .o object files. Different
// from generic ELF streamer in emitting mapping symbols ($x and $d) to delimit
// regions of data and code.
#include "AArch64TargetStreamer.h"
#include "AArch64WinCOFFStreamer.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCELFStreamer.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbolELF.h"
#include "llvm/MC/MCWinCOFFStreamer.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
namespace {
class AArch64ELFStreamer;
class AArch64TargetAsmStreamer : public AArch64TargetStreamer {
formatted_raw_ostream &OS;
void emitInst(uint32_t Inst) override;
AArch64TargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS);
AArch64TargetAsmStreamer::AArch64TargetAsmStreamer(MCStreamer &S,
formatted_raw_ostream &OS)
: AArch64TargetStreamer(S), OS(OS) {}
void AArch64TargetAsmStreamer::emitInst(uint32_t Inst) {
OS << "\t.inst\t0x" << Twine::utohexstr(Inst) << "\n";
/// Extend the generic ELFStreamer class so that it can emit mapping symbols at
/// the appropriate points in the object files. These symbols are defined in the
/// AArch64 ELF ABI:
/// In brief: $x or $d should be emitted at the start of each contiguous region
/// of A64 code or data in a section. In practice, this emission does not rely
/// on explicit assembler directives but on inherent properties of the
/// directives doing the emission (e.g. ".byte" is data, "add x0, x0, x0" an
/// instruction).
/// As a result this system is orthogonal to the DataRegion infrastructure used
/// by MachO. Beware!
class AArch64ELFStreamer : public MCELFStreamer {
AArch64ELFStreamer(MCContext &Context, std::unique_ptr<MCAsmBackend> TAB,
std::unique_ptr<MCObjectWriter> OW,
std::unique_ptr<MCCodeEmitter> Emitter)
: MCELFStreamer(Context, std::move(TAB), std::move(OW),
MappingSymbolCounter(0), LastEMS(EMS_None) {}
void ChangeSection(MCSection *Section, const MCExpr *Subsection) override {
// We have to keep track of the mapping symbol state of any sections we
// use. Each one should start off as EMS_None, which is provided as the
// default constructor by DenseMap::lookup.
LastMappingSymbols[getPreviousSection().first] = LastEMS;
LastEMS = LastMappingSymbols.lookup(Section);
MCELFStreamer::ChangeSection(Section, Subsection);
// Reset state between object emissions
void reset() override {
MappingSymbolCounter = 0;
LastEMS = EMS_None;
/// This function is the one used to emit instruction data into the ELF
/// streamer. We override it to add the appropriate mapping symbol if
/// necessary.
void EmitInstruction(const MCInst &Inst,
const MCSubtargetInfo &STI) override {
MCELFStreamer::EmitInstruction(Inst, STI);
/// Emit a 32-bit value as an instruction. This is only used for the .inst
/// directive, EmitInstruction should be used in other cases.
void emitInst(uint32_t Inst) {
char Buffer[4];
// We can't just use EmitIntValue here, as that will emit a data mapping
// symbol, and swap the endianness on big-endian systems (instructions are
// always little-endian).
for (unsigned I = 0; I < 4; ++I) {
Buffer[I] = uint8_t(Inst);
Inst >>= 8;
MCELFStreamer::EmitBytes(StringRef(Buffer, 4));
/// This is one of the functions used to emit data into an ELF section, so the
/// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
/// if necessary.
void EmitBytes(StringRef Data) override {
/// This is one of the functions used to emit data into an ELF section, so the
/// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
/// if necessary.
void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override {
MCELFStreamer::EmitValueImpl(Value, Size, Loc);
void emitFill(const MCExpr &NumBytes, uint64_t FillValue,
SMLoc Loc) override {
MCObjectStreamer::emitFill(NumBytes, FillValue, Loc);
enum ElfMappingSymbol {
void EmitDataMappingSymbol() {
if (LastEMS == EMS_Data)
LastEMS = EMS_Data;
void EmitA64MappingSymbol() {
if (LastEMS == EMS_A64)
LastEMS = EMS_A64;
void EmitMappingSymbol(StringRef Name) {
auto *Symbol = cast<MCSymbolELF>(getContext().getOrCreateSymbol(
Name + "." + Twine(MappingSymbolCounter++)));
int64_t MappingSymbolCounter;
DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols;
ElfMappingSymbol LastEMS;
} // end anonymous namespace
namespace llvm {
AArch64ELFStreamer &AArch64TargetELFStreamer::getStreamer() {
return static_cast<AArch64ELFStreamer &>(Streamer);
void AArch64TargetELFStreamer::emitInst(uint32_t Inst) {
MCTargetStreamer *createAArch64AsmTargetStreamer(MCStreamer &S,
formatted_raw_ostream &OS,
MCInstPrinter *InstPrint,
bool isVerboseAsm) {
return new AArch64TargetAsmStreamer(S, OS);
MCELFStreamer *createAArch64ELFStreamer(MCContext &Context,
std::unique_ptr<MCAsmBackend> TAB,
std::unique_ptr<MCObjectWriter> OW,
std::unique_ptr<MCCodeEmitter> Emitter,
bool RelaxAll) {
AArch64ELFStreamer *S = new AArch64ELFStreamer(
Context, std::move(TAB), std::move(OW), std::move(Emitter));
if (RelaxAll)
return S;
} // end namespace llvm