Boost logo

Boost :

From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-04-07 06:13:07

Ben Hutchings has kindly contributed the attached sp_counted_base
implementations for g++ on IA64 and 68020+. The IA64 version of decrement
should be changed to:

Ben Hutchings wrote:
>>> It isn't a memory barrier (unless you add .acq or .rel to it) but I
>>> don't believe a barrier is needed for the simple increment and
>>> decrement operations. It is always atomic, like lock xadd.
>> For increment, no. For decrement, yes. It needs to be a release when
>> the new value is nonzero,
> Oh yes, of course it does.
>> and an acquire when the new value is zero.
> Hmm, tricky. There would be need to be another instruction afterward
> that creates the acquire barrier. Maybe this would do:
> __asm__ (" fetchaddl.rel %0=[%4],-1 \n"
> " cmp.eq %2,%3=1,%0 \n"
> "(%2) ldl.acq %0=[%4] " :
> "=r"(rv), "=m"(*pw), "=c", "=c" :
> "r"(pw) :
> );
> Don't ask me whether that's the most efficient way to do this!

In your (Boost developers) opinion,

1. Do we need a platform-specific version for 68020+ at all? (It is my
understanding that threads aren't very popular there ;-) but I may be wrong)

2. Should we try to get an IA64 version in 1.33 or should this be postponed
for 1.34?

Boost list run by bdawes at, gregod at, cpdaniel at, john at