Comment on attachment 409383 [details] [diff] [review] patch >diff --git a/js/src/jsxml.h b/js/src/jsxml.h >--- a/js/src/jsxml.h >+++ b/js/src/jsxml.h >@@ -107,19 +107,18 @@ struct JSXML { > #ifdef DEBUG_notme > JSCList links; > uint32 serial; > #endif > JSObject *object; > void *domnode; /* DOM node if mapped info item */ > JSXML *parent; > JSObject *name; >- uint16 xml_class; /* discriminates u, below */ >- uint16 xml_flags; /* flags, see below */ >- uint32 align; >+ uint32 xml_class; /* discriminates u, below */ >+ uint32 xml_flags; /* flags, see below */ Nit: comment here that all fields must be at least 4 bytes in size and that for code simplicity we tolerate wasteful uint32 usage for xml_flags and xml_class. Also refer to this bug for reasons.

No space is wasted here. I eliminated the alignment field. So this patch is strictly faster without wasting a single bit. I am not convinced the 16-bit fields are actually a problem. This patch is mostly preventive. We don't comment JSObject either. I think I will add a comment to the conservative scanning code instead.