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//===-- WebAssemblyAsmBackend.cpp - WebAssembly Assembler Backend ---------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief This file implements the WebAssemblyAsmBackend class.
///
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.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 WebAssemblyAsmBackend final : public MCAsmBackend {
bool Is64Bit;
public:
explicit WebAssemblyAsmBackend(bool Is64Bit)
: MCAsmBackend(), Is64Bit(Is64Bit) {}
~WebAssemblyAsmBackend() override {}
void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
uint64_t Value, bool IsPCRel) const override;
MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override;
// No instruction requires relaxation
bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
const MCRelaxableFragment *DF,
const MCAsmLayout &Layout) const override {
return false;
}
unsigned getNumFixupKinds() const override {
// We currently just use the generic fixups in MCFixup.h and don't have any
// target-specific fixups.
return 0;
}
bool mayNeedRelaxation(const MCInst &Inst) const override { return false; }
void relaxInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
MCInst &Res) const override {}
bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
};
bool WebAssemblyAsmBackend::writeNopData(uint64_t Count,
MCObjectWriter *OW) const {
if (Count == 0)
return true;
// FIXME: Do something.
return false;
}
void WebAssemblyAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
unsigned DataSize, uint64_t Value,
bool IsPCRel) const {
const MCFixupKindInfo &Info = getFixupKindInfo(Fixup.getKind());
assert(Info.Flags == 0 && "WebAssembly does not use MCFixupKindInfo flags");
unsigned NumBytes = (Info.TargetSize + 7) / 8;
if (Value == 0)
return; // Doesn't change encoding.
// Shift the value into position.
Value <<= Info.TargetOffset;
unsigned 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] |= uint8_t((Value >> (i * 8)) & 0xff);
}
MCObjectWriter *
WebAssemblyAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
return createWebAssemblyELFObjectWriter(OS, Is64Bit, 0);
}
} // end anonymous namespace
MCAsmBackend *llvm::createWebAssemblyAsmBackend(const Triple &TT) {
return new WebAssemblyAsmBackend(TT.isArch64Bit());
}
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