... instead of prepending it at the beginning (the original behavior since implemented in r122535 2010-12-23). This builds up an AttributeList in the the order in which the attributes appear in the source.
The reverse order caused nodes for attributes in the AST (e.g. LoopHint) to be in the reverse order, and therefore printed in the wrong order in -ast-dump. Some TODO comments mention this. The order was explicitly reversed for enable_if attribute overload resolution and name mangling, which is not necessary anymore with this patch.
The change unfortunately has some secondary effect, especially on diagnostic output. In the simplest cases, the CHECK lines or expected diagnostic were changed to the the new output. If the kind of error/warning changed, the attribute' order was changed instead.
This unfortunately causes some 'previous occurrence here' hints to be textually after the main marker. This typically happens when attributes are merged, but are incompatible to each other. Interchanging the role of the the main and note SourceLocation will also cause the case where two different declaration's attributes (in contrast to multiple attributes of the same declaration) are merged to be reverse. There is no easy fix because sometimes previous attributes are merged into a new declaration's attribute list, sometimes new attributes are added to a previous declaration's attribute list. Since 'previous occurrence here' pointing to locations after the main marker is not rare, I left the markers as-is; it is only relevant when the attributes are declared in the same declaration anyway.