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Re: Optimization of conditional access to globals: thread-unsafe?
Hi,
On Mon, 29 Oct 2007, Darryl Miles wrote:
> Don't you need the barrier before. This is to ensure it completed the
> condition test completely first before it then processed the assignment
> expression.
>
> if(condition) {
> somebarrier();
> *p = value;
> }
>
> The issue is not that the store is done too late, but that a
> write-access is done too early.
No. The initial cause for this needless thread was that a store was moved
down, out of its control region. Of course it doesn't help when people
keep shifting their point of focus in such discussions. Now it already
moved to fear that GCC would somehow introduce new traps. Without the
people discussing about that fear even bothering to check if that really
happens :-(
Ciao,
Michael.