Remove (attr 0) from tag text format (#3946)

This attribute is always 0 and reserved for future use. In Binayren's
unofficial text format we were writing this field as `(attr 0)`, but we
have recently come to the conclusion that this is not necessary.

Relevant discussion:
https://github.com/WebAssembly/exception-handling/pull/160#discussion_r653254680

4 files changed, 2 insertions, 26 deletions

diff --git a/src/passes/Print.cpp b/src/passes/Print.cpp
index 750bfbb38..c6bf13f42 100644
--- a/src/passes/Print.cpp
+++ b/src/passes/Print.cpp
@@ -2685,7 +2685,7 @@ struct PrintSExpression : public UnifiedExpressionVisitor<PrintSExpression> {
     emitImportHeader(curr);
     o << "(tag ";
     printName(curr->name, o);
-    o << maybeSpace << "(attr " << curr->attribute << ')' << maybeSpace;
+    o << maybeSpace;
     printParamType(o, curr->sig.params, currModule);
     o << "))";
     o << maybeNewLine;
@@ -2695,7 +2695,7 @@ struct PrintSExpression : public UnifiedExpressionVisitor<PrintSExpression> {
     o << '(';
     printMedium(o, "tag ");
     printName(curr->name, o);
-    o << maybeSpace << "(attr " << curr->attribute << ')' << maybeSpace;
+    o << maybeSpace;
     printParamType(o, curr->sig.params, currModule);
     o << ")" << maybeNewLine;
   }
diff --git a/src/shared-constants.h b/src/shared-constants.h
index a0de4b9bb..6ad3ab9ac 100644
--- a/src/shared-constants.h
+++ b/src/shared-constants.h
@@ -66,7 +66,6 @@ extern Name PRINT;
 extern Name EXIT;
 extern Name SHARED;
 extern Name TAG;
-extern Name ATTR;
 
 } // namespace wasm
 
diff --git a/src/wasm/wasm-s-parser.cpp b/src/wasm/wasm-s-parser.cpp
index c688630c3..8bedeab9f 100644
--- a/src/wasm/wasm-s-parser.cpp
+++ b/src/wasm/wasm-s-parser.cpp
@@ -3109,14 +3109,6 @@ void SExpressionWasmBuilder::parseImport(Element& s) {
     }
   } else if (kind == ExternalKind::Tag) {
     auto tag = make_unique<Tag>();
-    if (j >= inner.size()) {
-      throw ParseException("tag does not have an attribute", s.line, s.col);
-    }
-    auto& attrElem = *inner[j++];
-    if (!elementStartsWith(attrElem, ATTR) || attrElem.size() != 2) {
-      throw ParseException("invalid attribute", attrElem.line, attrElem.col);
-    }
-    tag->attribute = atoi(attrElem[1]->c_str());
     j = parseTypeUse(inner, j, tag->sig);
     tag->setName(name, hasExplicitName);
     tag->module = module;
@@ -3498,20 +3490,6 @@ void SExpressionWasmBuilder::parseTag(Element& s, bool preParseImport) {
     ex->kind = ExternalKind::Tag;
   }
 
-  // Parse attribute
-  if (i >= s.size()) {
-    throw ParseException("tag does not have an attribute", s.line, s.col);
-  }
-  auto& attrElem = *s[i++];
-  if (!elementStartsWith(attrElem, ATTR) || attrElem.size() != 2) {
-    throw ParseException("invalid attribute", attrElem.line, attrElem.col);
-  }
-  if (!attrElem[1]->isStr()) {
-    throw ParseException(
-      "invalid attribute", attrElem[1]->line, attrElem[1]->col);
-  }
-  tag->attribute = atoi(attrElem[1]->c_str());
-
   // Parse typeuse
   i = parseTypeUse(s, i, tag->sig);
 
diff --git a/src/wasm/wasm.cpp b/src/wasm/wasm.cpp
index ea82bac39..54c82159f 100644
--- a/src/wasm/wasm.cpp
+++ b/src/wasm/wasm.cpp
@@ -97,7 +97,6 @@ Name PRINT("print");
 Name EXIT("exit");
 Name SHARED("shared");
 Name TAG("tag");
-Name ATTR("attr");
 
 // Expressions