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Re: -fno-tree-cselim not working?


On Fri, 2007-10-26 at 13:23 -0700, Ian Lance Taylor wrote:
> Andi Kleen <andi@firstfloor.org> writes:
> 
> > Ian Lance Taylor <iant@google.com> writes:
> > >
> > > This code isn't going to be a problem, because spin_unlock presumably
> > > includes a memory barrier.
> > 
> > At least in the Linux kernel and also in glibc for mutexes locks are just plain
> > function calls, which are not necessarily full memory barriers.
> 
> True, and problematic in some cases--but a function call which gcc
> can't see is a memory barrier for all addressable memory.

I would have thought it is the case iff the register aliasing
the variable is caller save rather than callee save according
to the ABI.


-- 
John Skaller <skaller at users dot sf dot net>
Felix, successor to C++: http://felix.sf.net


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