SystemZMCAsmBackend.cpp
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//===-- SystemZMCAsmBackend.cpp - SystemZ assembler backend ---------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/SystemZMCFixups.h"
#include "MCTargetDesc/SystemZMCTargetDesc.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSubtargetInfo.h"
using namespace llvm;
// Value is a fully-resolved relocation value: Symbol + Addend [- Pivot].
// Return the bits that should be installed in a relocation field for
// fixup kind Kind.
static uint64_t extractBitsForFixup(MCFixupKind Kind, uint64_t Value) {
if (Kind < FirstTargetFixupKind)
return Value;
switch (unsigned(Kind)) {
case SystemZ::FK_390_PC12DBL:
case SystemZ::FK_390_PC16DBL:
case SystemZ::FK_390_PC24DBL:
case SystemZ::FK_390_PC32DBL:
return (int64_t)Value / 2;
case SystemZ::FK_390_TLS_CALL:
return 0;
}
llvm_unreachable("Unknown fixup kind!");
}
namespace {
class SystemZMCAsmBackend : public MCAsmBackend {
uint8_t OSABI;
public:
SystemZMCAsmBackend(uint8_t osABI)
: MCAsmBackend(support::big), OSABI(osABI) {}
// Override MCAsmBackend
unsigned getNumFixupKinds() const override {
return SystemZ::NumTargetFixupKinds;
}
const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
const MCValue &Target, MutableArrayRef<char> Data,
uint64_t Value, bool IsResolved,
const MCSubtargetInfo *STI) const override;
bool mayNeedRelaxation(const MCInst &Inst,
const MCSubtargetInfo &STI) const override {
return false;
}
bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
const MCRelaxableFragment *Fragment,
const MCAsmLayout &Layout) const override {
return false;
}
bool writeNopData(raw_ostream &OS, uint64_t Count) const override;
std::unique_ptr<MCObjectTargetWriter>
createObjectTargetWriter() const override {
return createSystemZObjectWriter(OSABI);
}
};
} // end anonymous namespace
const MCFixupKindInfo &
SystemZMCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
const static MCFixupKindInfo Infos[SystemZ::NumTargetFixupKinds] = {
{ "FK_390_PC12DBL", 4, 12, MCFixupKindInfo::FKF_IsPCRel },
{ "FK_390_PC16DBL", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
{ "FK_390_PC24DBL", 0, 24, MCFixupKindInfo::FKF_IsPCRel },
{ "FK_390_PC32DBL", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "FK_390_TLS_CALL", 0, 0, 0 }
};
if (Kind < FirstTargetFixupKind)
return MCAsmBackend::getFixupKindInfo(Kind);
assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
"Invalid kind!");
return Infos[Kind - FirstTargetFixupKind];
}
void SystemZMCAsmBackend::applyFixup(const MCAssembler &Asm,
const MCFixup &Fixup,
const MCValue &Target,
MutableArrayRef<char> Data, uint64_t Value,
bool IsResolved,
const MCSubtargetInfo *STI) const {
MCFixupKind Kind = Fixup.getKind();
unsigned Offset = Fixup.getOffset();
unsigned BitSize = getFixupKindInfo(Kind).TargetSize;
unsigned Size = (BitSize + 7) / 8;
assert(Offset + Size <= Data.size() && "Invalid fixup offset!");
// Big-endian insertion of Size bytes.
Value = extractBitsForFixup(Kind, Value);
if (BitSize < 64)
Value &= ((uint64_t)1 << BitSize) - 1;
unsigned ShiftValue = (Size * 8) - 8;
for (unsigned I = 0; I != Size; ++I) {
Data[Offset + I] |= uint8_t(Value >> ShiftValue);
ShiftValue -= 8;
}
}
bool SystemZMCAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count) const {
for (uint64_t I = 0; I != Count; ++I)
OS << '\x7';
return true;
}
MCAsmBackend *llvm::createSystemZMCAsmBackend(const Target &T,
const MCSubtargetInfo &STI,
const MCRegisterInfo &MRI,
const MCTargetOptions &Options) {
uint8_t OSABI =
MCELFObjectTargetWriter::getOSABI(STI.getTargetTriple().getOS());
return new SystemZMCAsmBackend(OSABI);
}