Re: Is gcc thread-unsafe?

Arjan van de Ven
2007-10-25T03:50:20Z

On Thu, 25 Oct 2007 13:24:49 +1000
Nick Piggin <nickpiggin@yahoo.com.au> wrote:

> Hi,
>
> Andi spotted this exchange on the gcc list. I don't think he's
> brought it up here yet, but it worries me enough that I'd like
> to discuss it.
>
> Starts here
> http://gcc.gnu.org/ml/gcc/2007-10/msg00266.html
>
> Concrete example here
> http://gcc.gnu.org/ml/gcc/2007-10/msg00275.html
>
> Basically, what the gcc developers are saying is that gcc is
> free to load and store to any memory location, so long as it
> behaves as if the instructions were executed in sequence.
>

this optimization btw is a serious mis-optimization, it makes memory
more dirty and causes cachelines to become unshared.... I'm sure it
works great on microbenchmarks but it sucks bigtime for anything real