Re: Another security vulnerability

MitchAlsup1 <mitchalsup@aol.com> schrieb:

Thomas Koenig wrote:
>

Stefan Monnier <monnier@iro.umontreal.ca> schrieb:

Since each chased pointer starts back at LSQ, the cost is no different
than an explicit Prefetch instruction, except without (a),(b) and (c)
having been applied first.

>
I thought the important difference is that the decision to prefetch or
not can be done dynamically based on past history.

>

Programmers and compilers are notoriously bad at predicting
branches (except for error branches),

>
Which are always predicted to have no error.

On the second or third time, certainly.  Hmmm... given hot/cold
splitting which is fairly standard by now, do branch predictors
take this into account?

                                      but ought to be quite good
at predicting prefetches.

>
What makes you think programmers understand prefetches any better than
exceptions ??

Pointers are used in many common data structures; linked list,
trees, ...  A programmer who does not know about dereferencing
pointers should be kept away from computer keyboards, preferably
at a distance of at least 3 m.

 

                          If a pointer is loaded, chances are
very high that are it will be dereferenced.

>
What if the value loaded is NULL.

Then it should be trivially predicted that it should not be prefetched.