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//===-- PPCXCOFFObjectWriter.cpp - PowerPC XCOFF Writer -------------------===//
//
//
// 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/PPCFixupKinds.h"
#include "MCTargetDesc/PPCMCTargetDesc.h"
#include "llvm/BinaryFormat/XCOFF.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCValue.h"
#include "llvm/MC/MCXCOFFObjectWriter.h"
using namespace llvm;
namespace {
class PPCXCOFFObjectWriter : public MCXCOFFObjectTargetWriter {
static constexpr uint8_t SignBitMask = 0x80;
public:
PPCXCOFFObjectWriter(bool Is64Bit);
std::pair<uint8_t, uint8_t>
getRelocTypeAndSignSize(const MCValue &Target, const MCFixup &Fixup,
bool IsPCRel) const override;
};
} // end anonymous namespace
PPCXCOFFObjectWriter::PPCXCOFFObjectWriter(bool Is64Bit)
: MCXCOFFObjectTargetWriter(Is64Bit) {}
std::unique_ptr<MCObjectTargetWriter>
llvm::createPPCXCOFFObjectWriter(bool Is64Bit) {
return std::make_unique<PPCXCOFFObjectWriter>(Is64Bit);
}
std::pair<uint8_t, uint8_t> PPCXCOFFObjectWriter::getRelocTypeAndSignSize(
const MCValue &Target, const MCFixup &Fixup, bool IsPCRel) const {
const MCSymbolRefExpr::VariantKind Modifier =
Target.isAbsolute() ? MCSymbolRefExpr::VK_None
: Target.getSymA()->getKind();
// People from AIX OS team says AIX link editor does not care about
// the sign bit in the relocation entry "most" of the time.
// The system assembler seems to set the sign bit on relocation entry
// based on similar property of IsPCRel. So we will do the same here.
// TODO: More investigation on how assembler decides to set the sign
// bit, and we might want to match that.
const uint8_t EncodedSignednessIndicator = IsPCRel ? SignBitMask : 0u;
// The magic number we use in SignAndSize has a strong relationship with
// the corresponding MCFixupKind. In most cases, it's the MCFixupKind
// number - 1, because SignAndSize encodes the bit length being
// relocated minus 1.
switch ((unsigned)Fixup.getKind()) {
default:
report_fatal_error("Unimplemented fixup kind.");
case PPC::fixup_ppc_half16:
switch (Modifier) {
default:
report_fatal_error("Unsupported modifier for half16 fixup.");
case MCSymbolRefExpr::VK_None:
return {XCOFF::RelocationType::R_TOC, EncodedSignednessIndicator | 15};
}
break;
case PPC::fixup_ppc_br24:
// Branches are 4 byte aligned, so the 24 bits we encode in
// the instruction actually represents a 26 bit offset.
return {XCOFF::RelocationType::R_RBR, EncodedSignednessIndicator | 25};
case FK_Data_4:
return {XCOFF::RelocationType::R_POS, EncodedSignednessIndicator | 31};
}
}
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