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//===-- AMDGPUAsmBackend.cpp - AMDGPU Assembler Backend -------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
/// \file
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "MCTargetDesc/AMDGPUFixupKinds.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/TargetRegistry.h"
using namespace llvm;
namespace {
class AMDGPUAsmBackend : public MCAsmBackend {
public:
AMDGPUAsmBackend(const Target &T)
: MCAsmBackend() {}
unsigned getNumFixupKinds() const override { return AMDGPU::NumTargetFixupKinds; };
void processFixupValue(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFixup &Fixup, const MCFragment *DF,
const MCValue &Target, uint64_t &Value,
bool &IsResolved) override;
void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
uint64_t Value, bool IsPCRel) const override;
bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const override {
return false;
}
void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
MCInst &Res) const override {
llvm_unreachable("Not implemented");
}
bool mayNeedRelaxation(const MCInst &Inst) const override { return false; }
bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
};
} //End anonymous namespace
static unsigned getFixupKindNumBytes(unsigned Kind) {
switch (Kind) {
case AMDGPU::fixup_si_sopp_br:
return 2;
case FK_SecRel_1:
case FK_Data_1:
return 1;
case FK_SecRel_2:
case FK_Data_2:
return 2;
case FK_SecRel_4:
case FK_Data_4:
case FK_PCRel_4:
return 4;
case FK_SecRel_8:
case FK_Data_8:
return 8;
default:
llvm_unreachable("Unknown fixup kind!");
}
}
static uint64_t adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
MCContext *Ctx) {
int64_t SignedValue = static_cast<int64_t>(Value);
switch (Fixup.getKind()) {
case AMDGPU::fixup_si_sopp_br: {
int64_t BrImm = (SignedValue - 4) / 4;
if (Ctx && !isInt<16>(BrImm))
Ctx->reportError(Fixup.getLoc(), "branch size exceeds simm16");
return BrImm;
}
case FK_Data_1:
case FK_Data_2:
case FK_Data_4:
case FK_Data_8:
case FK_PCRel_4:
case FK_SecRel_4:
return Value;
default:
llvm_unreachable("unhandled fixup kind");
}
}
void AMDGPUAsmBackend::processFixupValue(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFixup &Fixup, const MCFragment *DF,
const MCValue &Target, uint64_t &Value,
bool &IsResolved) {
MCValue Res;
// When we have complex expressions like: BB0_1 + (BB0_2 - 4), which are
// used for long branches, this function will be called with
// IsResolved = false and Value set to some pre-computed value. In
// the example above, the value would be:
// (BB0_1 + (BB0_2 - 4)) - CurrentOffsetFromStartOfFunction.
// This is not what we want. We just want the expression computation
// only. The reason the MC layer subtracts the current offset from the
// expression is because the fixup is of kind FK_PCRel_4.
// For these scenarios, evaluateAsValue gives us the computation that we
// want.
if (!IsResolved && Fixup.getValue()->evaluateAsValue(Res, Layout) &&
Res.isAbsolute()) {
Value = Res.getConstant();
IsResolved = true;
}
if (IsResolved)
Value = adjustFixupValue(Fixup, Value, &Asm.getContext());
}
void AMDGPUAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
unsigned DataSize, uint64_t Value,
bool IsPCRel) const {
if (!Value)
return; // Doesn't change encoding.
MCFixupKindInfo Info = getFixupKindInfo(Fixup.getKind());
// Shift the value into position.
Value <<= Info.TargetOffset;
unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
uint32_t Offset = Fixup.getOffset();
assert(Offset + NumBytes <= DataSize && "Invalid fixup offset!");
// For each byte of the fragment that the fixup touches, mask in the bits from
// the fixup value.
for (unsigned i = 0; i != NumBytes; ++i)
Data[Offset + i] |= static_cast<uint8_t>((Value >> (i * 8)) & 0xff);
}
const MCFixupKindInfo &AMDGPUAsmBackend::getFixupKindInfo(
MCFixupKind Kind) const {
const static MCFixupKindInfo Infos[AMDGPU::NumTargetFixupKinds] = {
// name offset bits flags
{ "fixup_si_sopp_br", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
};
if (Kind < FirstTargetFixupKind)
return MCAsmBackend::getFixupKindInfo(Kind);
return Infos[Kind - FirstTargetFixupKind];
}
bool AMDGPUAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
OW->WriteZeros(Count);
return true;
}
//===----------------------------------------------------------------------===//
// ELFAMDGPUAsmBackend class
//===----------------------------------------------------------------------===//
namespace {
class ELFAMDGPUAsmBackend : public AMDGPUAsmBackend {
bool Is64Bit;
bool HasRelocationAddend;
public:
ELFAMDGPUAsmBackend(const Target &T, const Triple &TT) :
AMDGPUAsmBackend(T), Is64Bit(TT.getArch() == Triple::amdgcn),
HasRelocationAddend(TT.getOS() == Triple::AMDHSA) { }
MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
return createAMDGPUELFObjectWriter(Is64Bit, HasRelocationAddend, OS);
}
};
} // end anonymous namespace
MCAsmBackend *llvm::createAMDGPUAsmBackend(const Target &T,
const MCRegisterInfo &MRI,
const Triple &TT, StringRef CPU,
const MCTargetOptions &Options) {
// Use 64-bit ELF for amdgcn
return new ELFAMDGPUAsmBackend(T, TT);
}
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