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//===-- X86AsmBackend.cpp - X86 Assembler Backend -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/Target/TargetAsmBackend.h"
#include "X86.h"
#include "X86FixupKinds.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Target/TargetRegistry.h"
#include "llvm/Target/TargetAsmBackend.h"
using namespace llvm;
namespace {
static unsigned getFixupKindLog2Size(unsigned Kind) {
switch (Kind) {
default: assert(0 && "invalid fixup kind!");
case X86::reloc_pcrel_1byte:
case FK_Data_1: return 0;
case FK_Data_2: return 1;
case X86::reloc_pcrel_4byte:
case X86::reloc_riprel_4byte:
case X86::reloc_riprel_4byte_movq_load:
case FK_Data_4: return 2;
case FK_Data_8: return 3;
}
}
class X86AsmBackend : public TargetAsmBackend {
public:
X86AsmBackend(const Target &T)
: TargetAsmBackend(T) {}
void ApplyFixup(const MCAsmFixup &Fixup, MCDataFragment &DF,
uint64_t Value) const {
unsigned Size = 1 << getFixupKindLog2Size(Fixup.Kind);
assert(Fixup.Offset + Size <= DF.getContents().size() &&
"Invalid fixup offset!");
for (unsigned i = 0; i != Size; ++i)
DF.getContents()[Fixup.Offset + i] = uint8_t(Value >> (i * 8));
}
};
class ELFX86AsmBackend : public X86AsmBackend {
public:
ELFX86AsmBackend(const Target &T)
: X86AsmBackend(T) {
HasAbsolutizedSet = true;
HasScatteredSymbols = true;
}
bool isVirtualSection(const MCSection &Section) const {
const MCSectionELF &SE = static_cast<const MCSectionELF&>(Section);
return SE.getType() == MCSectionELF::SHT_NOBITS;;
}
};
class DarwinX86AsmBackend : public X86AsmBackend {
public:
DarwinX86AsmBackend(const Target &T)
: X86AsmBackend(T) {
HasAbsolutizedSet = true;
HasScatteredSymbols = true;
}
bool isVirtualSection(const MCSection &Section) const {
const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
return (SMO.getType() == MCSectionMachO::S_ZEROFILL ||
SMO.getType() == MCSectionMachO::S_GB_ZEROFILL);
}
};
class DarwinX86_32AsmBackend : public DarwinX86AsmBackend {
public:
DarwinX86_32AsmBackend(const Target &T)
: DarwinX86AsmBackend(T) {}
};
class DarwinX86_64AsmBackend : public DarwinX86AsmBackend {
public:
DarwinX86_64AsmBackend(const Target &T)
: DarwinX86AsmBackend(T) {
HasReliableSymbolDifference = true;
}
virtual bool doesSectionRequireSymbols(const MCSection &Section) const {
// Temporary labels in the string literals sections require symbols. The
// issue is that the x86_64 relocation format does not allow symbol +
// offset, and so the linker does not have enough information to resolve the
// access to the appropriate atom unless an external relocation is used. For
// non-cstring sections, we expect the compiler to use a non-temporary label
// for anything that could have an addend pointing outside the symbol.
//
// See <rdar://problem/4765733>.
const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
return SMO.getType() == MCSectionMachO::S_CSTRING_LITERALS;
}
};
}
TargetAsmBackend *llvm::createX86_32AsmBackend(const Target &T,
const std::string &TT) {
switch (Triple(TT).getOS()) {
case Triple::Darwin:
return new DarwinX86_32AsmBackend(T);
default:
return new ELFX86AsmBackend(T);
}
}
TargetAsmBackend *llvm::createX86_64AsmBackend(const Target &T,
const std::string &TT) {
switch (Triple(TT).getOS()) {
case Triple::Darwin:
return new DarwinX86_64AsmBackend(T);
default:
return new ELFX86AsmBackend(T);
}
}
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