This is a patch I should have gone ahead and committed when I wrote it against gcc 4.6, but... better late than never I suppose.
The Idea is to have some mechanism akin to __builtin_expect that can apply to the edges created by asm goto. We tossed around possible syntax additions to the asm construct, but nothing we came up with looked easy to use. In the end it seemed fantastically cleaner to simply use the existing attribute syntax and apply the existing hot/cold attributes to labels. This patch by itself doesn't actually accomplish what we really want for use in the kernel (which is why it didn't get committed before I guess), but it's the user-visible portion that would enable further work. Tested on x86_64 and committed. r~
