Many of the dromaeo tests end up using StringImpl::find() and ::reverseFind() including the IgnoreCase varieties. These methods don't have 8 bit string paths.
Created attachment 123163 [details]
This appears to be neutral to slightly positive to sun spider and v8 performance.
Comment on attachment 123163 [details]
I think you should factor out the shared hash-search code into a static helper function template, to avoid code duplication.
Committed r106019: <http://trac.webkit.org/changeset/106019>