Parse non-nullable tuple elements without special handling (WebAssemb…

…ly#5910)

In the binary parser, when creating a scratch local to hold multivalue results
as tuples, we previously ensured that the scratch local did not contain any
non-nullable by modifying its type and inserting ref.as_non_null as necessary.
Now that we properly support non-nullable elements in tuple locals, however,
this parser behavior is no longer necessary. Remove it.

src/wasm/wasm-binary.cpp

@@ -3006,32 +3006,14 @@ void WasmBinaryReader::skipUnreachableCode() {
 void WasmBinaryReader::pushExpression(Expression* curr) {
   auto type = curr->type;
   if (type.isTuple()) {
-    // Store tuple to local and push individual extracted values
+    // Store tuple to local and push individual extracted values.
     Builder builder(wasm);
-    // Non-nullable types require special handling as they cannot be stored to
-    // a local, so we may need to use a different local type than the original.
-    auto localType = type;
-    if (!wasm.features.hasGCNNLocals()) {
-      std::vector<Type> finalTypes;
-      for (auto t : type) {
-        if (t.isNonNullable()) {
-          t = Type(t.getHeapType(), Nullable);
-        }
-        finalTypes.push_back(t);
-      }
-      localType = Type(Tuple(finalTypes));
-    }
     requireFunctionContext("pushExpression-tuple");
-    Index tuple = builder.addVar(currFunction, localType);
+    Index tuple = builder.addVar(currFunction, type);
     expressionStack.push_back(builder.makeLocalSet(tuple, curr));
-    for (Index i = 0; i < localType.size(); ++i) {
-      Expression* value =
-        builder.makeTupleExtract(builder.makeLocalGet(tuple, localType), i);
-      if (localType[i] != type[i]) {
-        // We modified this to be nullable; undo that.
-        value = builder.makeRefAs(RefAsNonNull, value);
-      }
-      expressionStack.push_back(value);
+    for (Index i = 0; i < type.size(); ++i) {
+      expressionStack.push_back(
+        builder.makeTupleExtract(builder.makeLocalGet(tuple, type), i));
     }
   } else {
     expressionStack.push_back(curr);

test/lit/passes/roundtrip.wast

@@ -5,7 +5,7 @@
  ;; CHECK:      (type $none (func))
  (type $none (func))
  ;; CHECK:      (func $foo (type $none)
- ;; CHECK-NEXT:  (local $0 (funcref (ref null $none)))
+ ;; CHECK-NEXT:  (local $0 (funcref (ref $none)))
  ;; CHECK-NEXT:  (local $1 funcref)
  ;; CHECK-NEXT:  (local.set $0
  ;; CHECK-NEXT:   (block $label$1 (result funcref (ref $none))
@@ -23,10 +23,8 @@
  ;; CHECK-NEXT:     )
  ;; CHECK-NEXT:    )
  ;; CHECK-NEXT:    (drop
- ;; CHECK-NEXT:     (ref.as_non_null
- ;; CHECK-NEXT:      (tuple.extract 1
- ;; CHECK-NEXT:       (local.get $0)
- ;; CHECK-NEXT:      )
+ ;; CHECK-NEXT:     (tuple.extract 1
+ ;; CHECK-NEXT:      (local.get $0)
  ;; CHECK-NEXT:     )
  ;; CHECK-NEXT:    )
  ;; CHECK-NEXT:    (local.get $1)