[WebAssembly] Attach a name to globals similarly to function naming

[ncw]

Summary

This allows LLD to print the name for an InputGlobal when encountering an error.

---

NB. This PR specifies globals in the "name" section - but I don't think we need that now, and it's not "official" yet anyway: https://github.com/WebAssembly/design/pull/1064

[sbc100]

lib/Object/WasmObjectFile.cpp

428 ↗

(On Diff #136797)

I'd rather not use auto unless the type is already present on the same line (i.e. when using dyn_cast).

[ncw]

lib/Object/WasmObjectFile.cpp

428 ↗

(On Diff #136797)

Committed with that fix

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

struct WasmGlobalType {
   uint8_t Type;
   bool Mutable;
 };
 
 struct WasmGlobal {
   uint32_t Index;
   WasmGlobalType Type;
   WasmInitExpr InitExpr;
+  StringRef Name; // from the "linking" or "names" section
 };
 
 struct WasmImport {
   StringRef Module;
   StringRef Field;
   uint8_t Kind;
   union {
     uint32_t SigIndex;

 };
 
 struct WasmFunction {
   uint32_t Index;
   std::vector<WasmLocalDecl> Locals;
   ArrayRef<uint8_t> Body;
   uint32_t CodeSectionOffset;
   uint32_t Size;
-  StringRef Name; // from the "names" section
+  StringRef Name; // from the "linking" or "names" section
   StringRef Comdat; // from the "comdat info" section
 };
 
 struct WasmDataSegment {
   uint32_t MemoryIndex;
   WasmInitExpr Offset;
   ArrayRef<uint8_t> Content;
   StringRef Name;

llvm/trunk/lib/Object/WasmObjectFile.cpp

case wasm::WASM_SYMBOL_TYPE_FUNCTION:
       if (!isValidFunctionIndex(Info.ElementIndex) ||
           IsDefined != isDefinedFunctionIndex(Info.ElementIndex))
         return make_error<GenericBinaryError>("invalid function symbol index",
                                               object_error::parse_failed);
       if (IsDefined) {
         Info.Name = readString(Ptr);
         unsigned FuncIndex = Info.ElementIndex - NumImportedFunctions;
         FunctionType = &Signatures[FunctionTypes[FuncIndex]];
-        auto &Function = Functions[FuncIndex];
+        wasm::WasmFunction &Function = Functions[FuncIndex];
         if (Function.Name.empty()) {
           // Use the symbol's name to set a name for the Function, but only if
           // one hasn't already been set.
           Function.Name = Info.Name;
         }
       } else {
         wasm::WasmImport &Import = *ImportedFunctions[Info.ElementIndex];
         FunctionType = &Signatures[Import.SigIndex];
         Info.Name = Import.Field;
       }
       break;
 
     case wasm::WASM_SYMBOL_TYPE_GLOBAL:
       Info.ElementIndex = readVaruint32(Ptr);
       if (!isValidGlobalIndex(Info.ElementIndex) ||
           IsDefined != isDefinedGlobalIndex(Info.ElementIndex))
         return make_error<GenericBinaryError>("invalid global symbol index",
                                               object_error::parse_failed);
       if (IsDefined) {
         Info.Name = readString(Ptr);
         unsigned GlobalIndex = Info.ElementIndex - NumImportedGlobals;
-        GlobalType = &Globals[GlobalIndex].Type;
+        wasm::WasmGlobal &Global = Globals[GlobalIndex];
+        GlobalType = &Global.Type;
+        if (Global.Name.empty()) {
+          // Use the symbol's name to set a name for the Global, but only if
+          // one hasn't already been set.
+          Global.Name = Info.Name;
+        }
       } else {
         wasm::WasmImport &Import = *ImportedGlobals[Info.ElementIndex];
         Info.Name = Import.Field;
         GlobalType = &Import.Global;
       }
       break;
 
     case wasm::WASM_SYMBOL_TYPE_DATA: