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llvm-project/llvm/lib/MC/MCWinCOFFStreamer.cpp

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//===- llvm/MC/MCWinCOFFStreamer.cpp --------------------------------------===//
//
// 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 an implementation of a Windows COFF object file streamer.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/COFF.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCFragment.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSymbolCOFF.h"
#include "llvm/MC/MCWinCOFFStreamer.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/SMLoc.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
using namespace llvm;
#define DEBUG_TYPE "WinCOFFStreamer"
MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context,
std::unique_ptr<MCAsmBackend> MAB,
std::unique_ptr<MCCodeEmitter> CE,
std::unique_ptr<MCObjectWriter> OW)
: MCObjectStreamer(Context, std::move(MAB), std::move(OW), std::move(CE)),
CurSymbol(nullptr) {}
void MCWinCOFFStreamer::emitInstToData(const MCInst &Inst,
const MCSubtargetInfo &STI) {
MCDataFragment *DF = getOrCreateDataFragment();
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
// Add the fixups and data.
for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
DF->getFixups().push_back(Fixups[i]);
}
DF->setHasInstructions(STI);
DF->getContents().append(Code.begin(), Code.end());
}
void MCWinCOFFStreamer::initSections(bool NoExecStack,
const MCSubtargetInfo &STI) {
// FIXME: this is identical to the ELF one.
// This emulates the same behavior of GNU as. This makes it easier
// to compare the output as the major sections are in the same order.
SwitchSection(getContext().getObjectFileInfo()->getTextSection());
emitCodeAlignment(4, &STI);
SwitchSection(getContext().getObjectFileInfo()->getDataSection());
emitCodeAlignment(4, &STI);
SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
emitCodeAlignment(4, &STI);
SwitchSection(getContext().getObjectFileInfo()->getTextSection());
}
void MCWinCOFFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
auto *Symbol = cast<MCSymbolCOFF>(S);
MCObjectStreamer::emitLabel(Symbol, Loc);
}
void MCWinCOFFStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
// Let the target do whatever target specific stuff it needs to do.
getAssembler().getBackend().handleAssemblerFlag(Flag);
switch (Flag) {
// None of these require COFF specific handling.
case MCAF_SyntaxUnified:
case MCAF_Code16:
case MCAF_Code32:
case MCAF_Code64:
break;
case MCAF_SubsectionsViaSymbols:
llvm_unreachable("COFF doesn't support .subsections_via_symbols");
}
}
void MCWinCOFFStreamer::emitThumbFunc(MCSymbol *Func) {
llvm_unreachable("not implemented");
}
bool MCWinCOFFStreamer::emitSymbolAttribute(MCSymbol *S,
MCSymbolAttr Attribute) {
auto *Symbol = cast<MCSymbolCOFF>(S);
getAssembler().registerSymbol(*Symbol);
switch (Attribute) {
default: return false;
case MCSA_WeakReference:
case MCSA_Weak:
Symbol->setIsWeakExternal();
Symbol->setExternal(true);
break;
case MCSA_Global:
Symbol->setExternal(true);
break;
case MCSA_AltEntry:
llvm_unreachable("COFF doesn't support the .alt_entry attribute");
}
return true;
}
void MCWinCOFFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
llvm_unreachable("not implemented");
}
void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) {
auto *Symbol = cast<MCSymbolCOFF>(S);
if (CurSymbol)
Error("starting a new symbol definition without completing the "
"previous one");
CurSymbol = Symbol;
}
void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
if (!CurSymbol) {
Error("storage class specified outside of symbol definition");
return;
}
if (StorageClass & ~COFF::SSC_Invalid) {
Error("storage class value '" + Twine(StorageClass) +
"' out of range");
return;
}
getAssembler().registerSymbol(*CurSymbol);
cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
}
void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
if (!CurSymbol) {
Error("symbol type specified outside of a symbol definition");
return;
}
if (Type & ~0xffff) {
Error("type value '" + Twine(Type) + "' out of range");
return;
}
getAssembler().registerSymbol(*CurSymbol);
cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
}
void MCWinCOFFStreamer::EndCOFFSymbolDef() {
if (!CurSymbol)
Error("ending symbol definition without starting one");
CurSymbol = nullptr;
}
void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
// SafeSEH is a feature specific to 32-bit x86. It does not exist (and is
// unnecessary) on all platforms which use table-based exception dispatch.
if (getContext().getTargetTriple().getArch() != Triple::x86)
return;
const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
if (CSymbol->isSafeSEH())
return;
MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
getAssembler().registerSection(*SXData);
if (SXData->getAlignment() < 4)
SXData->setAlignment(Align(4));
new MCSymbolIdFragment(Symbol, SXData);
getAssembler().registerSymbol(*Symbol);
CSymbol->setIsSafeSEH();
// The Microsoft linker requires that the symbol type of a handler be
// function. Go ahead and oblige it here.
CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
<< COFF::SCT_COMPLEX_TYPE_SHIFT);
}
void MCWinCOFFStreamer::EmitCOFFSymbolIndex(MCSymbol const *Symbol) {
MCSection *Sec = getCurrentSectionOnly();
getAssembler().registerSection(*Sec);
if (Sec->getAlignment() < 4)
Sec->setAlignment(Align(4));
new MCSymbolIdFragment(Symbol, getCurrentSectionOnly());
getAssembler().registerSymbol(*Symbol);
}
void MCWinCOFFStreamer::EmitCOFFSectionIndex(const MCSymbol *Symbol) {
visitUsedSymbol(*Symbol);
MCDataFragment *DF = getOrCreateDataFragment();
const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
DF->getFixups().push_back(Fixup);
DF->getContents().resize(DF->getContents().size() + 2, 0);
}
void MCWinCOFFStreamer::EmitCOFFSecRel32(const MCSymbol *Symbol,
uint64_t Offset) {
visitUsedSymbol(*Symbol);
MCDataFragment *DF = getOrCreateDataFragment();
// Create Symbol A for the relocation relative reference.
const MCExpr *MCE = MCSymbolRefExpr::create(Symbol, getContext());
// Add the constant offset, if given.
if (Offset)
MCE = MCBinaryExpr::createAdd(
MCE, MCConstantExpr::create(Offset, getContext()), getContext());
// Build the secrel32 relocation.
MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_SecRel_4);
// Record the relocation.
DF->getFixups().push_back(Fixup);
// Emit 4 bytes (zeros) to the object file.
DF->getContents().resize(DF->getContents().size() + 4, 0);
}
void MCWinCOFFStreamer::EmitCOFFImgRel32(const MCSymbol *Symbol,
int64_t Offset) {
visitUsedSymbol(*Symbol);
MCDataFragment *DF = getOrCreateDataFragment();
// Create Symbol A for the relocation relative reference.
const MCExpr *MCE = MCSymbolRefExpr::create(
Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
// Add the constant offset, if given.
if (Offset)
MCE = MCBinaryExpr::createAdd(
MCE, MCConstantExpr::create(Offset, getContext()), getContext());
// Build the imgrel relocation.
MCFixup Fixup = MCFixup::create(DF->getContents().size(), MCE, FK_Data_4);
// Record the relocation.
DF->getFixups().push_back(Fixup);
// Emit 4 bytes (zeros) to the object file.
DF->getContents().resize(DF->getContents().size() + 4, 0);
}
void MCWinCOFFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
unsigned ByteAlignment) {
auto *Symbol = cast<MCSymbolCOFF>(S);
const Triple &T = getContext().getTargetTriple();
if (T.isWindowsMSVCEnvironment()) {
if (ByteAlignment > 32)
report_fatal_error("alignment is limited to 32-bytes");
// Round size up to alignment so that we will honor the alignment request.
Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
}
getAssembler().registerSymbol(*Symbol);
Symbol->setExternal(true);
Symbol->setCommon(Size, ByteAlignment);
if (!T.isWindowsMSVCEnvironment() && ByteAlignment > 1) {
SmallString<128> Directive;
raw_svector_ostream OS(Directive);
const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
OS << " -aligncomm:\"" << Symbol->getName() << "\","
<< Log2_32_Ceil(ByteAlignment);
PushSection();
SwitchSection(MFI->getDrectveSection());
emitBytes(Directive);
PopSection();
}
}
void MCWinCOFFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
unsigned ByteAlignment) {
auto *Symbol = cast<MCSymbolCOFF>(S);
MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
PushSection();
SwitchSection(Section);
emitValueToAlignment(ByteAlignment, 0, 1, 0);
emitLabel(Symbol);
Symbol->setExternal(false);
emitZeros(Size);
PopSection();
}
void MCWinCOFFStreamer::emitWeakReference(MCSymbol *AliasS,
const MCSymbol *Symbol) {
auto *Alias = cast<MCSymbolCOFF>(AliasS);
emitSymbolAttribute(Alias, MCSA_Weak);
getAssembler().registerSymbol(*Symbol);
Alias->setVariableValue(MCSymbolRefExpr::create(
Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext()));
}
void MCWinCOFFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
uint64_t Size, unsigned ByteAlignment,
SMLoc Loc) {
llvm_unreachable("not implemented");
}
void MCWinCOFFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
uint64_t Size, unsigned ByteAlignment) {
llvm_unreachable("not implemented");
}
// TODO: Implement this if you want to emit .comment section in COFF obj files.
void MCWinCOFFStreamer::emitIdent(StringRef IdentString) {
llvm_unreachable("not implemented");
}
void MCWinCOFFStreamer::EmitWinEHHandlerData(SMLoc Loc) {
llvm_unreachable("not implemented");
}
void MCWinCOFFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
const MCSymbolRefExpr *To,
uint64_t Count) {
// Ignore temporary symbols for now.
if (!From->getSymbol().isTemporary() && !To->getSymbol().isTemporary())
getAssembler().CGProfile.push_back({From, To, Count});
}
void MCWinCOFFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
const MCSymbol *S = &SRE->getSymbol();
bool Created;
getAssembler().registerSymbol(*S, &Created);
if (Created)
cast<MCSymbolCOFF>(S)->setExternal(true);
}
void MCWinCOFFStreamer::finalizeCGProfile() {
for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
finalizeCGProfileEntry(E.From);
finalizeCGProfileEntry(E.To);
}
}
void MCWinCOFFStreamer::finishImpl() {
finalizeCGProfile();
MCObjectStreamer::finishImpl();
}
void MCWinCOFFStreamer::Error(const Twine &Msg) const {
getContext().reportError(SMLoc(), Msg);
}
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