Re: [PATCH 1/24] make atomic_read() behave consistently on alpha

[Valdis . Kletnieks]

On Sat, 11 Aug 2007 02:38:40 +0200, Segher Boessenkool said:
> >> That means GCC cannot compile Linux; it already optimises
> >> some accesses to scalars to smaller accesses when it knows
> >> it is allowed to.  Not often though, since it hardly ever
> >> helps in the cost model it employs.
> >
> > Please give an example code snippet + gcc version + arch
> > to back this up.
> 
> 	unsigned char f(unsigned long *p)
> 	{
> 	        return *p & 1;
> 	}

Not really valid, because it's still able to do one atomic access to
compute the result.

Now, if you had found an example where it converts a 32-bit atomic access into
2 separate 16-bit accesses that weren't atomic as a whole....

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