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//===-- X86TargetObjectFile.cpp - X86 Object Info -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "X86TargetObjectFile.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Operator.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Target/TargetLowering.h"
using namespace llvm;
using namespace dwarf;
X86_64MachoTargetObjectFile::X86_64MachoTargetObjectFile()
: TargetLoweringObjectFileMachO() {
SupportIndirectSymViaGOTPCRel = true;
}
const MCExpr *X86_64MachoTargetObjectFile::getTTypeGlobalReference(
const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
const TargetMachine &TM, MachineModuleInfo *MMI,
MCStreamer &Streamer) const {
// On Darwin/X86-64, we can reference dwarf symbols with foo@GOTPCREL+4, which
// is an indirect pc-relative reference.
if ((Encoding & DW_EH_PE_indirect) && (Encoding & DW_EH_PE_pcrel)) {
const MCSymbol *Sym = TM.getSymbol(GV, Mang);
const MCExpr *Res =
MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext());
const MCExpr *Four = MCConstantExpr::Create(4, getContext());
return MCBinaryExpr::CreateAdd(Res, Four, getContext());
}
return TargetLoweringObjectFileMachO::getTTypeGlobalReference(
GV, Encoding, Mang, TM, MMI, Streamer);
}
MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol(
const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
MachineModuleInfo *MMI) const {
return TM.getSymbol(GV, Mang);
}
const MCExpr *X86_64MachoTargetObjectFile::getIndirectSymViaGOTPCRel(
const MCSymbol *Sym, int64_t Offset) const {
// On Darwin/X86-64, we need to use foo@GOTPCREL+4 to access the got entry
// from a data section. In case there's an additional offset, then use
// foo@GOTPCREL+4+<offset>.
const MCExpr *Res =
MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext());
const MCExpr *Off = MCConstantExpr::Create(Offset+4, getContext());
return MCBinaryExpr::CreateAdd(Res, Off, getContext());
}
void
X86LinuxTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM) {
TargetLoweringObjectFileELF::Initialize(Ctx, TM);
InitializeELF(TM.Options.UseInitArray);
}
const MCExpr *
X86LinuxTargetObjectFile::getDebugThreadLocalSymbol(
const MCSymbol *Sym) const {
return MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext());
}
const MCExpr *X86WindowsTargetObjectFile::getExecutableRelativeSymbol(
const ConstantExpr *CE, Mangler &Mang, const TargetMachine &TM) const {
// We are looking for the difference of two symbols, need a subtraction
// operation.
const SubOperator *Sub = dyn_cast<SubOperator>(CE);
if (!Sub)
return nullptr;
// Symbols must first be numbers before we can subtract them, we need to see a
// ptrtoint on both subtraction operands.
const PtrToIntOperator *SubLHS =
dyn_cast<PtrToIntOperator>(Sub->getOperand(0));
const PtrToIntOperator *SubRHS =
dyn_cast<PtrToIntOperator>(Sub->getOperand(1));
if (!SubLHS || !SubRHS)
return nullptr;
// Our symbols should exist in address space zero, cowardly no-op if
// otherwise.
if (SubLHS->getPointerAddressSpace() != 0 ||
SubRHS->getPointerAddressSpace() != 0)
return nullptr;
// Both ptrtoint instructions must wrap global variables:
// - Only global variables are eligible for image relative relocations.
// - The subtrahend refers to the special symbol __ImageBase, a global.
const GlobalVariable *GVLHS =
dyn_cast<GlobalVariable>(SubLHS->getPointerOperand());
const GlobalVariable *GVRHS =
dyn_cast<GlobalVariable>(SubRHS->getPointerOperand());
if (!GVLHS || !GVRHS)
return nullptr;
// We expect __ImageBase to be a global variable without a section, externally
// defined.
//
// It should look something like this: @__ImageBase = external constant i8
if (GVRHS->isThreadLocal() || GVRHS->getName() != "__ImageBase" ||
!GVRHS->hasExternalLinkage() || GVRHS->hasInitializer() ||
GVRHS->hasSection())
return nullptr;
// An image-relative, thread-local, symbol makes no sense.
if (GVLHS->isThreadLocal())
return nullptr;
return MCSymbolRefExpr::Create(TM.getSymbol(GVLHS, Mang),
MCSymbolRefExpr::VK_COFF_IMGREL32,
getContext());
}
static std::string APIntToHexString(const APInt &AI) {
unsigned Width = (AI.getBitWidth() / 8) * 2;
std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
unsigned Size = HexString.size();
assert(Width >= Size && "hex string is too large!");
HexString.insert(HexString.begin(), Width - Size, '0');
return HexString;
}
static std::string scalarConstantToHexString(const Constant *C) {
Type *Ty = C->getType();
APInt AI;
if (isa<UndefValue>(C)) {
AI = APInt(Ty->getPrimitiveSizeInBits(), /*val=*/0);
} else if (Ty->isFloatTy() || Ty->isDoubleTy()) {
const auto *CFP = cast<ConstantFP>(C);
AI = CFP->getValueAPF().bitcastToAPInt();
} else if (Ty->isIntegerTy()) {
const auto *CI = cast<ConstantInt>(C);
AI = CI->getValue();
} else {
llvm_unreachable("unexpected constant pool element type!");
}
return APIntToHexString(AI);
}
const MCSection *
X86WindowsTargetObjectFile::getSectionForConstant(SectionKind Kind,
const Constant *C) const {
if (Kind.isReadOnly()) {
if (C) {
Type *Ty = C->getType();
SmallString<32> COMDATSymName;
if (Ty->isFloatTy() || Ty->isDoubleTy()) {
COMDATSymName = "__real@";
COMDATSymName += scalarConstantToHexString(C);
} else if (const auto *VTy = dyn_cast<VectorType>(Ty)) {
uint64_t NumBits = VTy->getBitWidth();
if (NumBits == 128 || NumBits == 256) {
COMDATSymName = NumBits == 128 ? "__xmm@" : "__ymm@";
for (int I = VTy->getNumElements() - 1, E = -1; I != E; --I)
COMDATSymName +=
scalarConstantToHexString(C->getAggregateElement(I));
}
}
if (!COMDATSymName.empty()) {
unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_LNK_COMDAT;
return getContext().getCOFFSection(".rdata", Characteristics, Kind,
COMDATSymName,
COFF::IMAGE_COMDAT_SELECT_ANY);
}
}
}
return TargetLoweringObjectFile::getSectionForConstant(Kind, C);
}
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