[WebAssembly] Improve libObject support for reading/writing wasm imports and exports

[sbc100]

Summary

Previously we had only supported reading/writing certain
types of imports and exports (functions and global).

Also add usefull overload of getWasmSymbol() and
getNumberOfSymbols() in support of lld port.

[dschuff]

include/llvm/Object/Wasm.h

85

I'm surprised there's not some method for this purpose on ObjectFile... but I don't see one...

lib/Object/WasmObjectFile.cpp

499

I think table is the only one left, right?

[sbc100]

• handle all import and export types

[sbc100]

lib/Object/WasmObjectFile.cpp

499

OK, I made this a more complete change so now we can support all external types.

[dschuff]

Cool, looks good. Maybe just clarify in the commit description that this really just applies to reading and writing the sections rather than e.g. codegen.

include/llvm/Object/Wasm.h

public:
   std::vector<wasm::WasmRelocation> Relocations; // Relocations for this section
 };
 
 class WasmObjectFile : public ObjectFile {
 public:
   WasmObjectFile(MemoryBufferRef Object, Error &Err);
 
   const wasm::WasmObjectHeader &getHeader() const;
-  const WasmSymbol &getWasmSymbol(DataRefImpl Symb) const;
+  const WasmSymbol &getWasmSymbol(const DataRefImpl &Symb) const;
+  const WasmSymbol &getWasmSymbol(const SymbolRef &Symbol) const;
   const WasmSection &getWasmSection(const SectionRef &Section) const;
   const wasm::WasmRelocation &getWasmRelocation(const RelocationRef& Ref) const;
 
   static bool classof(const Binary *v) { return v->isWasm(); }
 
   const std::vector<wasm::WasmSignature>& types() const { return Signatures; }
   const std::vector<uint32_t>& functionTypes() const { return FunctionTypes; }
   const std::vector<wasm::WasmImport>& imports() const { return Imports; }
   const std::vector<wasm::WasmTable>& tables() const { return Tables; }
   const std::vector<wasm::WasmLimits>& memories() const { return Memories; }
   const std::vector<wasm::WasmGlobal>& globals() const { return Globals; }
   const std::vector<wasm::WasmExport>& exports() const { return Exports; }
 
+  uint32_t getNumberOfSymbols() const {
+    return Symbols.size();
+  }
+
   const std::vector<wasm::WasmElemSegment>& elements() const {
     return ElemSegments;
   }
 
   const std::vector<wasm::WasmDataSegment>& dataSegments() const {
     return DataSegments;
   }
 

lib/Object/WasmObjectFile.cpp

for (uint32_t i = 0; i < Count; i++) {
     case wasm::WASM_EXTERNAL_FUNCTION:
       Symbols.emplace_back(Ex.Name, WasmSymbol::SymbolType::FUNCTION_EXPORT,
                            Sections.size(), i);
       break;
     case wasm::WASM_EXTERNAL_GLOBAL:
       Symbols.emplace_back(Ex.Name, WasmSymbol::SymbolType::GLOBAL_EXPORT,
                            Sections.size(), i);
       break;
+    case wasm::WASM_EXTERNAL_MEMORY:
+      break;
     default:
       // TODO(sbc): Handle other kinds of exports
       return make_error<GenericBinaryError>(
           "Unexpected export kind", object_error::parse_failed);
     }
   }
   if (Ptr != End)
     return make_error<GenericBinaryError>("Export section ended prematurely",
                                           object_error::parse_failed);
   return Error::success();

 }
 
 basic_symbol_iterator WasmObjectFile::symbol_end() const {
   DataRefImpl Ref;
   Ref.d.a = Symbols.size();
   return BasicSymbolRef(Ref, this);
 }
 
-const WasmSymbol &WasmObjectFile::getWasmSymbol(DataRefImpl Symb) const {
+const WasmSymbol &WasmObjectFile::getWasmSymbol(const DataRefImpl &Symb) const {
   return Symbols[Symb.d.a];
 }
 
+const WasmSymbol &WasmObjectFile::getWasmSymbol(const SymbolRef &Symb) const {
+  return getWasmSymbol(Symb.getRawDataRefImpl());
+}
+
 Expected<StringRef> WasmObjectFile::getSymbolName(DataRefImpl Symb) const {
   const WasmSymbol &Sym = getWasmSymbol(Symb);
   return Sym.Name;
 }
 
 Expected<uint64_t> WasmObjectFile::getSymbolAddress(DataRefImpl Symb) const {
   return getSymbolValue(Symb);
 }