On Monday, 15 December 2014 at 18:55:42 UTC, Paulo Pinto wrote:
Interesting, given that bounds checking support is an old
feature
http://x86.renejeschke.de/html/file_module_x86_id_18.html
If I remember my Assembly days in the 90's BOUND was slower
than doing the check explicitly.
Yes, and the BOUND instruction is deprecated and not available in
64-bit mode. It was also rather primitive compared to MPX. MPX
basically could make it possible for most C programs to bounds
check pointers extensively, not only arrays. At least in debug
builds.
I guess now it is way faster and the MMU is doing it instead.
The instructions are explicit, so you need solid compiler
support. But the lookup structure reminds me of how page-tables
are structured. So I suppose Intel are leveraging the knowhow
they have on MMU design when doing the implementation for MPX.
