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llvm-project/llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp

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//===-- RISCVAsmBackend.cpp - RISCV Assembler Backend ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/RISCVFixupKinds.h"
#include "MCTargetDesc/RISCVMCTargetDesc.h"
#include "llvm/ADT/APInt.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
namespace {
class RISCVAsmBackend : public MCAsmBackend {
uint8_t OSABI;
bool Is64Bit;
public:
RISCVAsmBackend(uint8_t OSABI, bool Is64Bit)
: MCAsmBackend(), OSABI(OSABI), Is64Bit(Is64Bit) {}
~RISCVAsmBackend() override {}
void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
const MCValue &Target, MutableArrayRef<char> Data,
uint64_t Value, bool IsResolved) const override;
std::unique_ptr<MCObjectWriter>
createObjectWriter(raw_pwrite_stream &OS) const override;
bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const override {
return false;
}
unsigned getNumFixupKinds() const override {
return RISCV::NumTargetFixupKinds;
}
const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override {
const static MCFixupKindInfo Infos[RISCV::NumTargetFixupKinds] = {
// This table *must* be in the order that the fixup_* kinds are defined in
// RISCVFixupKinds.h.
//
// name offset bits flags
{ "fixup_riscv_hi20", 12, 20, 0 },
{ "fixup_riscv_lo12_i", 20, 12, 0 },
{ "fixup_riscv_lo12_s", 0, 32, 0 },
{ "fixup_riscv_pcrel_hi20", 12, 20, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_riscv_jal", 12, 20, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_riscv_branch", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_riscv_rvc_jump", 2, 11, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_riscv_rvc_branch", 0, 16, MCFixupKindInfo::FKF_IsPCRel }
};
if (Kind < FirstTargetFixupKind)
return MCAsmBackend::getFixupKindInfo(Kind);
assert(unsigned(Kind - FirstTargetFixupKind) < getNumFixupKinds() &&
"Invalid kind!");
return Infos[Kind - FirstTargetFixupKind];
}
bool mayNeedRelaxation(const MCInst &Inst) const override { return false; }
void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
MCInst &Res) const override {
report_fatal_error("RISCVAsmBackend::relaxInstruction() unimplemented");
}
bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
};
bool RISCVAsmBackend::writeNopData(uint64_t Count, MCObjectWriter *OW) const {
// Once support for the compressed instruction set is added, we will be able
// to conditionally support 16-bit NOPs
if ((Count % 4) != 0)
return false;
// The canonical nop on RISC-V is addi x0, x0, 0
for (uint64_t i = 0; i < Count; i += 4)
OW->write32(0x13);
return true;
}
static uint64_t adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
MCContext &Ctx) {
unsigned Kind = Fixup.getKind();
switch (Kind) {
default:
llvm_unreachable("Unknown fixup kind!");
case FK_Data_1:
case FK_Data_2:
case FK_Data_4:
case FK_Data_8:
return Value;
case RISCV::fixup_riscv_lo12_i:
return Value & 0xfff;
case RISCV::fixup_riscv_lo12_s:
return (((Value >> 5) & 0x7f) << 25) | ((Value & 0x1f) << 7);
case RISCV::fixup_riscv_hi20:
case RISCV::fixup_riscv_pcrel_hi20:
// Add 1 if bit 11 is 1, to compensate for low 12 bits being negative.
return ((Value + 0x800) >> 12) & 0xfffff;
case RISCV::fixup_riscv_jal: {
if (!isInt<21>(Value))
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
if (Value & 0x1)
Ctx.reportError(Fixup.getLoc(), "fixup value must be 2-byte aligned");
// Need to produce imm[19|10:1|11|19:12] from the 21-bit Value.
unsigned Sbit = (Value >> 20) & 0x1;
unsigned Hi8 = (Value >> 12) & 0xff;
unsigned Mid1 = (Value >> 11) & 0x1;
unsigned Lo10 = (Value >> 1) & 0x3ff;
// Inst{31} = Sbit;
// Inst{30-21} = Lo10;
// Inst{20} = Mid1;
// Inst{19-12} = Hi8;
Value = (Sbit << 19) | (Lo10 << 9) | (Mid1 << 8) | Hi8;
return Value;
}
case RISCV::fixup_riscv_branch: {
if (!isInt<13>(Value))
Ctx.reportError(Fixup.getLoc(), "fixup value out of range");
if (Value & 0x1)
Ctx.reportError(Fixup.getLoc(), "fixup value must be 2-byte aligned");
// Need to extract imm[12], imm[10:5], imm[4:1], imm[11] from the 13-bit
// Value.
unsigned Sbit = (Value >> 12) & 0x1;
unsigned Hi1 = (Value >> 11) & 0x1;
unsigned Mid6 = (Value >> 5) & 0x3f;
unsigned Lo4 = (Value >> 1) & 0xf;
// Inst{31} = Sbit;
// Inst{30-25} = Mid6;
// Inst{11-8} = Lo4;
// Inst{7} = Hi1;
Value = (Sbit << 31) | (Mid6 << 25) | (Lo4 << 8) | (Hi1 << 7);
return Value;
}
case RISCV::fixup_riscv_rvc_jump: {
// Need to produce offset[11|4|9:8|10|6|7|3:1|5] from the 11-bit Value.
unsigned Bit11 = (Value >> 11) & 0x1;
unsigned Bit4 = (Value >> 4) & 0x1;
unsigned Bit9_8 = (Value >> 8) & 0x3;
unsigned Bit10 = (Value >> 10) & 0x1;
unsigned Bit6 = (Value >> 6) & 0x1;
unsigned Bit7 = (Value >> 7) & 0x1;
unsigned Bit3_1 = (Value >> 1) & 0x7;
unsigned Bit5 = (Value >> 5) & 0x1;
Value = (Bit11 << 10) | (Bit4 << 9) | (Bit9_8 << 7) | (Bit10 << 6) |
(Bit6 << 5) | (Bit7 << 4) | (Bit3_1 << 1) | Bit5;
return Value;
}
case RISCV::fixup_riscv_rvc_branch: {
// Need to produce offset[8|4:3], [reg 3 bit], offset[7:6|2:1|5]
unsigned Bit8 = (Value >> 8) & 0x1;
unsigned Bit7_6 = (Value >> 6) & 0x3;
unsigned Bit5 = (Value >> 5) & 0x1;
unsigned Bit4_3 = (Value >> 3) & 0x3;
unsigned Bit2_1 = (Value >> 1) & 0x3;
Value = (Bit8 << 12) | (Bit4_3 << 10) | (Bit7_6 << 5) | (Bit2_1 << 3) |
(Bit5 << 2);
return Value;
}
}
}
static unsigned getSize(unsigned Kind) {
switch (Kind) {
default:
return 4;
case RISCV::fixup_riscv_rvc_jump:
case RISCV::fixup_riscv_rvc_branch:
return 2;
}
}
void RISCVAsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
const MCValue &Target,
MutableArrayRef<char> Data, uint64_t Value,
bool IsResolved) const {
MCContext &Ctx = Asm.getContext();
MCFixupKindInfo Info = getFixupKindInfo(Fixup.getKind());
if (!Value)
return; // Doesn't change encoding.
// Apply any target-specific value adjustments.
Value = adjustFixupValue(Fixup, Value, Ctx);
// Shift the value into position.
Value <<= Info.TargetOffset;
unsigned Offset = Fixup.getOffset();
unsigned FullSize = getSize(Fixup.getKind());
#ifndef NDEBUG
unsigned NumBytes = (Info.TargetSize + 7) / 8;
assert(Offset + NumBytes <= Data.size() && "Invalid fixup offset!");
#endif
// For each byte of the fragment that the fixup touches, mask in the
// bits from the fixup value.
for (unsigned i = 0; i != FullSize; ++i) {
Data[Offset + i] |= uint8_t((Value >> (i * 8)) & 0xff);
}
}
std::unique_ptr<MCObjectWriter>
RISCVAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
return createRISCVELFObjectWriter(OS, OSABI, Is64Bit);
}
} // end anonymous namespace
MCAsmBackend *llvm::createRISCVAsmBackend(const Target &T,
const MCSubtargetInfo &STI,
const MCRegisterInfo &MRI,
const MCTargetOptions &Options) {
const Triple &TT = STI.getTargetTriple();
uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(TT.getOS());
return new RISCVAsmBackend(OSABI, TT.isArch64Bit());
}
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