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, support::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 }
79