Alan Cox wrote:
>
> On Sun, 2002-08-11 at 08:38, Andrew Morton wrote:
> > This information loss is unfortunate. Examples:
> >
> > for (i = 0; i < N; i++)
> > prefetch(foo[i]);
> >
> > Problem is, if `prefetch' is a no-op, the compiler will still
> > generate an empty busy-wait loop. Which it must do.
>
> Why - nothing there is volatile
Because the compiler sees:
for (i = 0; i < N; i++)
;
and it says "ah ha. A busy wait delay loop" and leaves it alone.
It's actually a special-case inside the compiler to not optimise
away such constructs.
-
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This archive was generated by hypermail 2b29 : Thu Aug 15 2002 - 22:00:24 EST