[Parser] Parse explicit exports (WebAssembly#6179)

Author: tlively

src/parser/contexts.h

@@ -548,6 +548,9 @@ struct ParseDeclsCtx : NullTypeParserCtx, NullInstrParserCtx {
   std::vector<DefPos> dataDefs;
   std::vector<DefPos> tagDefs;
 
+  // Positions of export definitions.
+  std::vector<Index> exportDefs;
+
   // Positions of typeuses that might implicitly define new types.
   std::vector<Index> implicitTypeDefs;
 
@@ -684,6 +687,11 @@ struct ParseDeclsCtx : NullTypeParserCtx, NullInstrParserCtx {
                   ImportNames* import,
                   TypeUseT type,
                   Index pos);
+
+  Result<> addExport(Index pos, Ok, Name, ExternalKind) {
+    exportDefs.push_back(pos);
+    return Ok{};
+  }
 };
 
 // Phase 2: Parse type definitions into a TypeBuilder.
@@ -1265,6 +1273,11 @@ struct ParseDefsCtx : TypeParserCtx<ParseDefsCtx> {
   Result<>
   addData(Name, Name* mem, std::optional<ExprT> offset, DataStringT, Index pos);
 
+  Result<> addExport(Index, Name value, Name name, ExternalKind kind) {
+    wasm.addExport(builder.makeExport(name, value, kind));
+    return Ok{};
+  }
+
   Result<Index> addScratchLocal(Index pos, Type type) {
     if (!func) {
       return in.err(pos,

src/parser/parsers.h

@@ -194,6 +194,7 @@ template<typename Ctx> MaybeResult<> func(Ctx&);
 template<typename Ctx> MaybeResult<> table(Ctx&);
 template<typename Ctx> MaybeResult<> memory(Ctx&);
 template<typename Ctx> MaybeResult<> global(Ctx&);
+template<typename Ctx> MaybeResult<> export_(Ctx&);
 template<typename Ctx> MaybeResult<typename Ctx::ExprT> maybeElemexpr(Ctx&);
 template<typename Ctx> Result<typename Ctx::ElemListT> elemlist(Ctx&, bool);
 template<typename Ctx> MaybeResult<> elem(Ctx&);
@@ -2371,6 +2372,56 @@ template<typename Ctx> MaybeResult<> global(Ctx& ctx) {
   return Ok{};
 }
 
+// export ::= '(' 'export' nm:name exportdesc ')'
+// exportdesc ::= '(' 'func' x:funcidx ')'
+//              | '(' 'table' x:tableidx ')'
+//              | '(' 'memory' x:memidx ')'
+//              | '(' 'global' x:globalidx ')'
+//              | '(' 'tag' x:tagidx ')'
+template<typename Ctx> MaybeResult<> export_(Ctx& ctx) {
+  auto pos = ctx.in.getPos();
+  if (!ctx.in.takeSExprStart("export"sv)) {
+    return {};
+  }
+
+  auto name = ctx.in.takeName();
+  if (!name) {
+    return ctx.in.err("expected export name");
+  }
+
+  if (ctx.in.takeSExprStart("func"sv)) {
+    auto idx = funcidx(ctx);
+    CHECK_ERR(idx);
+    CHECK_ERR(ctx.addExport(pos, *idx, *name, ExternalKind::Function));
+  } else if (ctx.in.takeSExprStart("table"sv)) {
+    auto idx = tableidx(ctx);
+    CHECK_ERR(idx);
+    CHECK_ERR(ctx.addExport(pos, *idx, *name, ExternalKind::Table));
+  } else if (ctx.in.takeSExprStart("memory"sv)) {
+    auto idx = memidx(ctx);
+    CHECK_ERR(idx);
+    CHECK_ERR(ctx.addExport(pos, *idx, *name, ExternalKind::Memory));
+  } else if (ctx.in.takeSExprStart("global"sv)) {
+    auto idx = globalidx(ctx);
+    CHECK_ERR(idx);
+    CHECK_ERR(ctx.addExport(pos, *idx, *name, ExternalKind::Global));
+  } else if (ctx.in.takeSExprStart("tag"sv)) {
+    auto idx = tagidx(ctx);
+    CHECK_ERR(idx);
+    CHECK_ERR(ctx.addExport(pos, *idx, *name, ExternalKind::Tag));
+  } else {
+    return ctx.in.err("expected export description");
+  }
+
+  if (!ctx.in.takeRParen()) {
+    return ctx.in.err("expected end of export description");
+  }
+  if (!ctx.in.takeRParen()) {
+    return ctx.in.err("expected end of export");
+  }
+  return Ok{};
+}
+
 // elemexpr ::= '(' 'item' expr ')' | '(' instr ')'
 template<typename Ctx>
 MaybeResult<typename Ctx::ExprT> maybeElemexpr(Ctx& ctx) {
@@ -2611,6 +2662,10 @@ template<typename Ctx> MaybeResult<> modulefield(Ctx& ctx) {
     CHECK_ERR(res);
     return Ok{};
   }
+  if (auto res = export_(ctx)) {
+    CHECK_ERR(res);
+    return Ok{};
+  }
   if (auto res = elem(ctx)) {
     CHECK_ERR(res);
     return Ok{};

src/parser/wat-parser.cpp

@@ -178,6 +178,16 @@ Result<> parseModule(Module& wasm, std::string_view input) {
       CHECK_ERR(parsed);
       assert(parsed);
     }
+
+    // Parse exports.
+    // TODO: It would be more technically correct to interleave these properly
+    // with the implicit inline exports in other module field definitions.
+    for (auto pos : decls.exportDefs) {
+      WithPosition with(ctx, pos);
+      auto parsed = export_(ctx);
+      CHECK_ERR(parsed);
+      assert(parsed);
+    }
   }
 
   return Ok{};

test/lit/wat-kitchen-sink.wast

@@ -354,9 +354,7 @@
  ;; CHECK:      (tag $tag-pair (param i32 i64))
  (tag $tag-pair (param i32 i64))
 
- ;; functions
- (func)
-
+ ;; explicit exports
  ;; CHECK:      (export "g1" (global $g1))
 
  ;; CHECK:      (export "g1.1" (global $g1))
@@ -377,6 +375,20 @@
 
  ;; CHECK:      (export "t0.1" (tag $imported))
 
+ ;; CHECK:      (export "exported-func" (func $fimport$0))
+ (export "exported-func" (func 0))
+ ;; CHECK:      (export "exported-table" (table $timport$0))
+ (export "exported-table" (table 0))
+ ;; CHECK:      (export "exported-memory" (memory $mimport$0))
+ (export "exported-memory" (memory 0))
+ ;; CHECK:      (export "exported-global" (global $g1))
+ (export "exported-global" (global 0))
+ ;; CHECK:      (export "exported-tag" (tag $imported))
+ (export "exported-tag" (tag 0))
+
+ ;; functions
+ (func)
+
  ;; CHECK:      (func $1 (type $void)
  ;; CHECK-NEXT:  (nop)
  ;; CHECK-NEXT: )