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 class SPIRVObjectWriter : public MCObjectWriter {
18   ::support::endian::Writer W;
19 
20   /// The target specific SPIR-V writer instance.
21   std::unique_ptr<MCSPIRVObjectTargetWriter> TargetObjectWriter;
22 
23 public:
24   SPIRVObjectWriter(std::unique_ptr<MCSPIRVObjectTargetWriter> MOTW,
25                     raw_pwrite_stream &OS)
26       : W(OS, support::little), TargetObjectWriter(std::move(MOTW)) {}
27 
28   ~SPIRVObjectWriter() override {}
29 
30 private:
31   void recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
32                         const MCFragment *Fragment, const MCFixup &Fixup,
33                         MCValue Target, uint64_t &FixedValue) override {}
34 
35   void executePostLayoutBinding(MCAssembler &Asm,
36                                 const MCAsmLayout &Layout) override {}
37 
38   uint64_t writeObject(MCAssembler &Asm, const MCAsmLayout &Layout) override;
39   void writeHeader(const MCAssembler &Asm);
40 };
41 
42 void SPIRVObjectWriter::writeHeader(const MCAssembler &Asm) {
43   constexpr uint32_t MagicNumber = 0x07230203;
44 
45   // TODO: set the version on a min-necessary basis (just like the translator
46   // does) requires some refactoring of MCAssembler::VersionInfoType.
47   constexpr uint32_t Major = 1;
48   constexpr uint32_t Minor = 0;
49   constexpr uint32_t VersionNumber = 0 | (Major << 16) | (Minor << 8);
50   // TODO: check if we could use anything other than 0 (spec allows).
51   constexpr uint32_t GeneratorMagicNumber = 0;
52   // TODO: do not hardcode this as well.
53   constexpr uint32_t Bound = 900;
54   constexpr uint32_t Schema = 0;
55 
56   W.write<uint32_t>(MagicNumber);
57   W.write<uint32_t>(VersionNumber);
58   W.write<uint32_t>(GeneratorMagicNumber);
59   W.write<uint32_t>(Bound);
60   W.write<uint32_t>(Schema);
61 }
62 
63 uint64_t SPIRVObjectWriter::writeObject(MCAssembler &Asm,
64                                         const MCAsmLayout &Layout) {
65   uint64_t StartOffset = W.OS.tell();
66   writeHeader(Asm);
67   for (const MCSection &S : Asm)
68     Asm.writeSectionData(W.OS, &S, Layout);
69   return W.OS.tell() - StartOffset;
70 }
71 
72 std::unique_ptr<MCObjectWriter>
73 llvm::createSPIRVObjectWriter(std::unique_ptr<MCSPIRVObjectTargetWriter> MOTW,
74                               raw_pwrite_stream &OS) {
75   return std::make_unique<SPIRVObjectWriter>(std::move(MOTW), OS);
76 }
77