1 //===-- WebAssemblyELFObjectWriter.cpp - WebAssembly ELF Writer -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// \brief This file handles ELF-specific object emission, converting LLVM's
12 /// internal fixups into the appropriate relocations.
14 //===----------------------------------------------------------------------===//
16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
17 #include "llvm/MC/MCELFObjectWriter.h"
18 #include "llvm/MC/MCFixup.h"
19 #include "llvm/MC/MCObjectWriter.h"
20 #include "llvm/Support/ErrorHandling.h"
24 class WebAssemblyELFObjectWriter final : public MCELFObjectTargetWriter {
26 WebAssemblyELFObjectWriter(bool Is64Bit, uint8_t OSABI);
29 unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
30 const MCFixup &Fixup, bool IsPCRel) const override;
32 } // end anonymous namespace
34 WebAssemblyELFObjectWriter::WebAssemblyELFObjectWriter(bool Is64Bit,
36 : MCELFObjectTargetWriter(Is64Bit, OSABI, ELF::EM_WEBASSEMBLY,
37 /*HasRelocationAddend=*/false) {}
39 unsigned WebAssemblyELFObjectWriter::getRelocType(MCContext &Ctx,
40 const MCValue &Target,
43 // WebAssembly functions are not allocated in the address space. To resolve a
44 // pointer to a function, we must use a special relocation type.
45 if (const MCSymbolRefExpr *SyExp =
46 dyn_cast<MCSymbolRefExpr>(Fixup.getValue()))
47 if (SyExp->getKind() == MCSymbolRefExpr::VK_WebAssembly_FUNCTION)
48 return ELF::R_WEBASSEMBLY_FUNCTION;
50 switch (Fixup.getKind()) {
52 assert(!is64Bit() && "4-byte relocations only supported on wasm32");
53 return ELF::R_WEBASSEMBLY_DATA;
55 assert(is64Bit() && "8-byte relocations only supported on wasm64");
56 return ELF::R_WEBASSEMBLY_DATA;
58 llvm_unreachable("unimplemented fixup kind");
62 std::unique_ptr<MCObjectWriter>
63 llvm::createWebAssemblyELFObjectWriter(raw_pwrite_stream &OS,
66 auto MOTW = llvm::make_unique<WebAssemblyELFObjectWriter>(Is64Bit, OSABI);
67 return createELFObjectWriter(std::move(MOTW), OS, /*IsLittleEndian=*/true);