llvm/lib/MC/SPIRVObjectWriter.cpp

   1 //===- llvm/MC/MCSPIRVObjectWriter.cpp - SPIR-V Object Writer ----*- C++ *-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "llvm/MC/MCAssembler.h"
  10 #include "llvm/MC/MCSPIRVObjectWriter.h"
  11 #include "llvm/MC/MCSection.h"
  12 #include "llvm/MC/MCValue.h"
  13 #include "llvm/Support/EndianStream.h"
  14
  15 using namespace llvm;
  16
  17 namespace {
  18 class SPIRVObjectWriter : public MCObjectWriter {
  19   ::support::endian::Writer W;
  20
  21   /// The target specific SPIR-V writer instance.
  22   std::unique_ptr<MCSPIRVObjectTargetWriter> TargetObjectWriter;
  23
  24 public:
  25   SPIRVObjectWriter(std::unique_ptr<MCSPIRVObjectTargetWriter> MOTW,
  26                     raw_pwrite_stream &OS)
  27       : W(OS, llvm::endianness::little), TargetObjectWriter(std::move(MOTW)) {}
  28
  29   ~SPIRVObjectWriter() override {}
  30
  31 private:
  32   void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
  33                         const MCFragment *Fragment, const MCFixup &Fixup,
  34                         MCValue Target, uint64_t &FixedValue) override {}
  35
  36   void executePostLayoutBinding(MCAssembler &Asm,
  37                                 const MCAsmLayout &Layout) override {}
  38
  39   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
  40   void writeHeader(const MCAssembler &Asm);
  41 };
  42 } // namespace
  43
  44 void SPIRVObjectWriter::writeHeader(const MCAssembler &Asm) {
  45   constexpr uint32_t MagicNumber = 0x07230203;
  46
  47   // TODO: set the version on a min-necessary basis (just like the translator
  48   // does) requires some refactoring of MCAssembler::VersionInfoType.
  49   constexpr uint32_t Major = 1;
  50   constexpr uint32_t Minor = 0;
  51   constexpr uint32_t VersionNumber = 0 | (Major << 16) | (Minor << 8);
  52   // TODO: check if we could use anything other than 0 (spec allows).
  53   constexpr uint32_t GeneratorMagicNumber = 0;
  54   // TODO: do not hardcode this as well.
  55   constexpr uint32_t Bound = 900;
  56   constexpr uint32_t Schema = 0;
  57
  58   W.write<uint32_t>(MagicNumber);
  59   W.write<uint32_t>(VersionNumber);
  60   W.write<uint32_t>(GeneratorMagicNumber);
  61   W.write<uint32_t>(Bound);
  62   W.write<uint32_t>(Schema);
  63 }
  64
  65 uint64_t SPIRVObjectWriter::writeObject(MCAssembler &Asm,
  66                                         const MCAsmLayout &Layout) {
  67   uint64_t StartOffset = W.OS.tell();
  68   writeHeader(Asm);
  69   for (const MCSection &S : Asm)
  70     Asm.writeSectionData(W.OS, &S, Layout);
  71   return W.OS.tell() - StartOffset;
  72 }
  73
  74 std::unique_ptr<MCObjectWriter>
  75 llvm::createSPIRVObjectWriter(std::unique_ptr<MCSPIRVObjectTargetWriter> MOTW,
  76                               raw_pwrite_stream &OS) {
  77   return std::make_unique<SPIRVObjectWriter>(std::move(MOTW), OS);
  78 }