llvm/lib/MC/MCDXContainerWriter.cpp

   1 //===- llvm/MC/MCDXContainerWriter.cpp - DXContainer 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/MCDXContainerWriter.h"
  10 #include "llvm/BinaryFormat/DXContainer.h"
  11 #include "llvm/MC/MCAssembler.h"
  12 #include "llvm/MC/MCContext.h"
  13 #include "llvm/MC/MCSection.h"
  14 #include "llvm/MC/MCValue.h"
  15 #include "llvm/Support/Alignment.h"
  16 #include "llvm/Support/EndianStream.h"
  17
  18 using namespace llvm;
  19
  20 MCDXContainerTargetWriter::~MCDXContainerTargetWriter() {}
  21
  22 namespace {
  23 class DXContainerObjectWriter : public MCObjectWriter {
  24   ::support::endian::Writer W;
  25
  26   /// The target specific DXContainer writer instance.
  27   std::unique_ptr<MCDXContainerTargetWriter> TargetObjectWriter;
  28
  29 public:
  30   DXContainerObjectWriter(std::unique_ptr<MCDXContainerTargetWriter> MOTW,
  31                           raw_pwrite_stream &OS)
  32       : W(OS, llvm::endianness::little), TargetObjectWriter(std::move(MOTW)) {}
  33
  34   ~DXContainerObjectWriter() override {}
  35
  36 private:
  37   void recordRelocation(MCAssembler &Asm, const MCFragment *Fragment,
  38                         const MCFixup &Fixup, MCValue Target,
  39                         uint64_t &FixedValue) override {}
  40
  41   uint64_t writeObject(MCAssembler &Asm) override;
  42 };
  43 } // namespace
  44
  45 uint64_t DXContainerObjectWriter::writeObject(MCAssembler &Asm) {
  46   // Start the file size as the header plus the size of the part offsets.
  47   // Presently DXContainer files usually contain 7-10 parts. Reserving space for
  48   // 16 part offsets gives us a little room for growth.
  49   llvm::SmallVector<uint64_t, 16> PartOffsets;
  50   uint64_t PartOffset = 0;
  51   for (const MCSection &Sec : Asm) {
  52     uint64_t SectionSize = Asm.getSectionAddressSize(Sec);
  53     // Skip empty sections.
  54     if (SectionSize == 0)
  55       continue;
  56
  57     assert(SectionSize < std::numeric_limits<uint32_t>::max() &&
  58            "Section size too large for DXContainer");
  59
  60     PartOffsets.push_back(PartOffset);
  61     PartOffset += sizeof(dxbc::PartHeader) + SectionSize;
  62     PartOffset = alignTo(PartOffset, Align(4ul));
  63     // The DXIL part also writes a program header, so we need to include its
  64     // size when computing the offset for a part after the DXIL part.
  65     if (Sec.getName() == "DXIL")
  66       PartOffset += sizeof(dxbc::ProgramHeader);
  67   }
  68   assert(PartOffset < std::numeric_limits<uint32_t>::max() &&
  69          "Part data too large for DXContainer");
  70
  71   uint64_t PartStart =
  72       sizeof(dxbc::Header) + (PartOffsets.size() * sizeof(uint32_t));
  73   uint64_t FileSize = PartStart + PartOffset;
  74   assert(FileSize < std::numeric_limits<uint32_t>::max() &&
  75          "File size too large for DXContainer");
  76
  77   // Write the header.
  78   W.write<char>({'D', 'X', 'B', 'C'});
  79   // Write 16-bytes of 0's for the hash.
  80   W.OS.write_zeros(16);
  81   // Write 1.0 for file format version.
  82   W.write<uint16_t>(1u);
  83   W.write<uint16_t>(0u);
  84   // Write the file size.
  85   W.write<uint32_t>(static_cast<uint32_t>(FileSize));
  86   // Write the number of parts.
  87   W.write<uint32_t>(static_cast<uint32_t>(PartOffsets.size()));
  88   // Write the offsets for the part headers for each part.
  89   for (uint64_t Offset : PartOffsets)
  90     W.write<uint32_t>(static_cast<uint32_t>(PartStart + Offset));
  91
  92   for (const MCSection &Sec : Asm) {
  93     uint64_t SectionSize = Asm.getSectionAddressSize(Sec);
  94     // Skip empty sections.
  95     if (SectionSize == 0)
  96       continue;
  97
  98     unsigned Start = W.OS.tell();
  99     // Write section header.
 100     W.write<char>(ArrayRef<char>(Sec.getName().data(), 4));
 101
 102     uint64_t PartSize = SectionSize;
 103
 104     if (Sec.getName() == "DXIL")
 105       PartSize += sizeof(dxbc::ProgramHeader);
 106     // DXContainer parts should be 4-byte aligned.
 107     PartSize = alignTo(PartSize, Align(4));
 108     W.write<uint32_t>(static_cast<uint32_t>(PartSize));
 109     if (Sec.getName() == "DXIL") {
 110       dxbc::ProgramHeader Header;
 111       memset(reinterpret_cast<void *>(&Header), 0, sizeof(dxbc::ProgramHeader));
 112
 113       const Triple &TT = Asm.getContext().getTargetTriple();
 114       VersionTuple Version = TT.getOSVersion();
 115       uint8_t MajorVersion = static_cast<uint8_t>(Version.getMajor());
 116       uint8_t MinorVersion =
 117           static_cast<uint8_t>(Version.getMinor().value_or(0));
 118       Header.Version =
 119           dxbc::ProgramHeader::getVersion(MajorVersion, MinorVersion);
 120       if (TT.hasEnvironment())
 121         Header.ShaderKind =
 122             static_cast<uint16_t>(TT.getEnvironment() - Triple::Pixel);
 123
 124       // The program header's size field is in 32-bit words.
 125       Header.Size = (SectionSize + sizeof(dxbc::ProgramHeader) + 3) / 4;
 126       memcpy(Header.Bitcode.Magic, "DXIL", 4);
 127       VersionTuple DXILVersion = TT.getDXILVersion();
 128       Header.Bitcode.MajorVersion = DXILVersion.getMajor();
 129       Header.Bitcode.MinorVersion = DXILVersion.getMinor().value_or(0);
 130       Header.Bitcode.Offset = sizeof(dxbc::BitcodeHeader);
 131       Header.Bitcode.Size = SectionSize;
 132       if (sys::IsBigEndianHost)
 133         Header.swapBytes();
 134       W.write<char>(ArrayRef<char>(reinterpret_cast<char *>(&Header),
 135                                    sizeof(dxbc::ProgramHeader)));
 136     }
 137     Asm.writeSectionData(W.OS, &Sec);
 138     unsigned Size = W.OS.tell() - Start;
 139     W.OS.write_zeros(offsetToAlignment(Size, Align(4)));
 140   }
 141   return 0;
 142 }
 143
 144 std::unique_ptr<MCObjectWriter> llvm::createDXContainerObjectWriter(
 145     std::unique_ptr<MCDXContainerTargetWriter> MOTW, raw_pwrite_stream &OS) {
 146   return std::make_unique<DXContainerObjectWriter>(std::move(MOTW), OS);
 147 }