[Parser] Support references to struct fields by name (WebAssembly#6293)

Construct a mapping from heap type and field name to field index, then use it
while parsing instructions.

Author: tlively

src/parser/contexts.h

@@ -1096,6 +1096,8 @@ struct ParseDefsCtx : TypeParserCtx<ParseDefsCtx> {
 
   const std::vector<HeapType>& types;
   const std::unordered_map<Index, HeapType>& implicitTypes;
+  const std::unordered_map<HeapType, std::unordered_map<Name, Index>>&
+    typeNames;
   const std::unordered_map<Index, Index>& implicitElemIndices;
 
   // The index of the current module element.
@@ -1113,14 +1115,17 @@ struct ParseDefsCtx : TypeParserCtx<ParseDefsCtx> {
     return Ok{};
   }
 
-  ParseDefsCtx(std::string_view in,
-               Module& wasm,
-               const std::vector<HeapType>& types,
-               const std::unordered_map<Index, HeapType>& implicitTypes,
-               const std::unordered_map<Index, Index>& implicitElemIndices,
-               const IndexMap& typeIndices)
+  ParseDefsCtx(
+    std::string_view in,
+    Module& wasm,
+    const std::vector<HeapType>& types,
+    const std::unordered_map<Index, HeapType>& implicitTypes,
+    const std::unordered_map<HeapType, std::unordered_map<Name, Index>>&
+      typeNames,
+    const std::unordered_map<Index, Index>& implicitElemIndices,
+    const IndexMap& typeIndices)
     : TypeParserCtx(typeIndices), in(in), wasm(wasm), builder(wasm),
-      types(types), implicitTypes(implicitTypes),
+      types(types), implicitTypes(implicitTypes), typeNames(typeNames),
       implicitElemIndices(implicitElemIndices), irBuilder(wasm) {}
 
   template<typename T> Result<T> withLoc(Index pos, Result<T> res) {
@@ -1192,8 +1197,13 @@ struct ParseDefsCtx : TypeParserCtx<ParseDefsCtx> {
   }
 
   Result<Index> getFieldFromName(HeapType type, Name name) {
-    // TODO: Field names
-    return in.err("symbolic field names note yet supported");
+    if (auto typeIt = typeNames.find(type); typeIt != typeNames.end()) {
+      const auto& fieldIdxs = typeIt->second;
+      if (auto fieldIt = fieldIdxs.find(name); fieldIt != fieldIdxs.end()) {
+        return fieldIt->second;
+      }
+    }
+    return in.err("unrecognized field name");
   }
 
   Result<Index> getLocalFromIdx(uint32_t idx) {

src/parser/wat-parser.cpp

@@ -110,6 +110,7 @@ Result<> parseModule(Module& wasm, std::string_view input) {
 
   // Parse type definitions.
   std::vector<HeapType> types;
+  std::unordered_map<HeapType, std::unordered_map<Name, Index>> typeNames;
   {
     TypeBuilder builder(decls.subtypeDefs.size());
     ParseTypeDefsCtx ctx(input, builder, *typeIndices);
@@ -124,11 +125,16 @@ Result<> parseModule(Module& wasm, std::string_view input) {
       return ctx.in.err(decls.typeDefs[err->index].pos, msg.str());
     }
     types = *built;
-    // Record type names on the module.
+    // Record type names on the module and in typeNames.
     for (size_t i = 0; i < types.size(); ++i) {
       auto& names = ctx.names[i];
-      if (names.name.is() || names.fieldNames.size()) {
+      auto& fieldNames = names.fieldNames;
+      if (names.name.is() || fieldNames.size()) {
         wasm.typeNames.insert({types[i], names});
+        auto& fieldIdxMap = typeNames[types[i]];
+        for (auto [idx, name] : fieldNames) {
+          fieldIdxMap.insert({name, idx});
+        }
       }
     }
   }
@@ -167,6 +173,7 @@ Result<> parseModule(Module& wasm, std::string_view input) {
                      wasm,
                      types,
                      implicitTypes,
+                     typeNames,
                      decls.implicitElemIndices,
                      *typeIndices);
     CHECK_ERR(parseDefs(ctx, decls.tableDefs, table));