| //===-- 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()); |
| } |