[WebAssembly] Export some more information on wasm functions

[sbc100]

Summary

These fields are useful for lld's gc-sections support

Also remove an unused field.

llvm/trunk/include/llvm/BinaryFormat/Wasm.h

 struct WasmLocalDecl {
   int32_t Type;
   uint32_t Count;
 };
 
 struct WasmFunction {
   std::vector<WasmLocalDecl> Locals;
   ArrayRef<uint8_t> Body;
+  size_t CodeSectionOffset;
+  size_t Size;
 };
 
 struct WasmDataSegment {
   uint32_t MemoryIndex;
   WasmInitExpr Offset;
   ArrayRef<uint8_t> Content;
   StringRef Name;
   uint32_t Alignment;

llvm/trunk/include/llvm/Object/Wasm.h

public:
   ArrayRef<wasm::WasmLimits> memories() const { return Memories; }
   ArrayRef<wasm::WasmGlobal> globals() const { return Globals; }
   ArrayRef<wasm::WasmExport> exports() const { return Exports; }
   const wasm::WasmLinkingData& linkingData() const { return LinkingData; }
   uint32_t getNumberOfSymbols() const { return Symbols.size(); }
   ArrayRef<wasm::WasmElemSegment> elements() const { return ElemSegments; }
   ArrayRef<WasmSegment> dataSegments() const { return DataSegments; }
   ArrayRef<wasm::WasmFunction> functions() const { return Functions; }
-  const ArrayRef<uint8_t>& code() const { return CodeSection; }
   uint32_t startFunction() const { return StartFunction; }
 
   void moveSymbolNext(DataRefImpl &Symb) const override;
 
   uint32_t getSymbolFlags(DataRefImpl Symb) const override;
 
   basic_symbol_iterator symbol_begin() const override;
 
private:
   std::vector<wasm::WasmLimits> Memories;
   std::vector<wasm::WasmGlobal> Globals;
   std::vector<wasm::WasmImport> Imports;
   std::vector<wasm::WasmExport> Exports;
   std::vector<wasm::WasmElemSegment> ElemSegments;
   std::vector<WasmSegment> DataSegments;
   std::vector<wasm::WasmFunction> Functions;
   std::vector<WasmSymbol> Symbols;
-  ArrayRef<uint8_t> CodeSection;
   uint32_t StartFunction = -1;
   bool HasLinkingSection = false;
   wasm::WasmLinkingData LinkingData;
   uint32_t NumImportedGlobals = 0;
   uint32_t NumImportedFunctions = 0;
   uint32_t ImportSection = 0;
   uint32_t ExportSection = 0;
 

llvm/trunk/lib/Object/WasmObjectFile.cpp

Error WasmObjectFile::parseStartSection(const uint8_t *Ptr, const uint8_t *End) {
   StartFunction = readVaruint32(Ptr);
   if (!isValidFunctionIndex(StartFunction))
     return make_error<GenericBinaryError>("Invalid start function",
                                           object_error::parse_failed);
   return Error::success();
 }
 
 Error WasmObjectFile::parseCodeSection(const uint8_t *Ptr, const uint8_t *End) {
+  const uint8_t *CodeSectionStart = Ptr;
   uint32_t FunctionCount = readVaruint32(Ptr);
   if (FunctionCount != FunctionTypes.size()) {
     return make_error<GenericBinaryError>("Invalid function count",
                                           object_error::parse_failed);
   }
 
-  CodeSection = ArrayRef<uint8_t>(Ptr, End - Ptr);
-
   while (FunctionCount--) {
     wasm::WasmFunction Function;
-    uint32_t FunctionSize = readVaruint32(Ptr);
-    const uint8_t *FunctionEnd = Ptr + FunctionSize;
+    const uint8_t *FunctionStart = Ptr;
+    uint32_t Size = readVaruint32(Ptr);
+    const uint8_t *FunctionEnd = Ptr + Size;
+
+    Function.CodeSectionOffset = FunctionStart - CodeSectionStart;
+    Function.Size = FunctionEnd - FunctionStart;
 
     uint32_t NumLocalDecls = readVaruint32(Ptr);
     Function.Locals.reserve(NumLocalDecls);
     while (NumLocalDecls--) {
       wasm::WasmLocalDecl Decl;
       Decl.Count = readVaruint32(Ptr);
       Decl.Type = readVarint7(Ptr);
       Function.Locals.push_back(Decl);