Enable finding bitcode in wasm objects

[alexcrichton]

Summary

This commit fixes using functions in IRObjectFile to load bitcode from
wasm objects by recognizing the file magic for wasm and also inheriting
the default implementation of classifying sections as bitcode.

[alexcrichton]

Oh dear sorry I'm still quite green on submitting patches to LLVM, so I'm not actually entirely sure what the build failure here means. Is that a transient CI issue or something that I need to address? (searching around for "No valid crumb was included in the request" doesn't seem to turn up much...)

[sbc100]

If you've tested locally I think that fine, I don't see any actionable information in that harbormaster error.

[alexcrichton]

Ok cool, thanks! I did test this out locally and it worked for use case, so on that front should be good to go!

I don't think I have commit access to LLVM though, would it be ok if you committed this for me?

llvm/include/llvm/Object/Wasm.h

public:
   Expected<ArrayRef<uint8_t>>
   getSectionContents(DataRefImpl Sec) const override;
   uint64_t getSectionAlignment(DataRefImpl Sec) const override;
   bool isSectionCompressed(DataRefImpl Sec) const override;
   bool isSectionText(DataRefImpl Sec) const override;
   bool isSectionData(DataRefImpl Sec) const override;
   bool isSectionBSS(DataRefImpl Sec) const override;
   bool isSectionVirtual(DataRefImpl Sec) const override;
-  bool isSectionBitcode(DataRefImpl Sec) const override;
   relocation_iterator section_rel_begin(DataRefImpl Sec) const override;
   relocation_iterator section_rel_end(DataRefImpl Sec) const override;
 
   // Overrides from RelocationRef.
   void moveRelocationNext(DataRefImpl &Rel) const override;
   uint64_t getRelocationOffset(DataRefImpl Rel) const override;
   symbol_iterator getRelocationSymbol(DataRefImpl Rel) const override;
   uint64_t getRelocationType(DataRefImpl Rel) const override;

llvm/lib/Object/IRObjectFile.cpp

 Expected<MemoryBufferRef>
 IRObjectFile::findBitcodeInMemBuffer(MemoryBufferRef Object) {
   file_magic Type = identify_magic(Object.getBuffer());
   switch (Type) {
   case file_magic::bitcode:
     return Object;
   case file_magic::elf_relocatable:
   case file_magic::macho_object:
+  case file_magic::wasm_object:
   case file_magic::coff_object: {
     Expected<std::unique_ptr<ObjectFile>> ObjFile =
         ObjectFile::createObjectFile(Object, Type);
     if (!ObjFile)
       return ObjFile.takeError();
     return findBitcodeInObject(*ObjFile->get());
   }
   default:

llvm/lib/Object/WasmObjectFile.cpp

 bool WasmObjectFile::isSectionData(DataRefImpl Sec) const {
   return getWasmSection(Sec).Type == wasm::WASM_SEC_DATA;
 }
 
 bool WasmObjectFile::isSectionBSS(DataRefImpl Sec) const { return false; }
 
 bool WasmObjectFile::isSectionVirtual(DataRefImpl Sec) const { return false; }
 
-bool WasmObjectFile::isSectionBitcode(DataRefImpl Sec) const { return false; }
-
 relocation_iterator WasmObjectFile::section_rel_begin(DataRefImpl Ref) const {
   DataRefImpl RelocRef;
   RelocRef.d.a = Ref.d.a;
   RelocRef.d.b = 0;
   return relocation_iterator(RelocationRef(RelocRef, this));
 }
 
 relocation_iterator WasmObjectFile::section_rel_end(DataRefImpl Ref) const {