OK, 200 cycles...
But what is the cost of the conditional branch you added in prefetch(x) ?
if (!x) return;
(correctly predicted or not, but do powerPC have a BTB ?)
About the NULL 'potential problem', maybe we could use a dummy nil (but
mapped) object, and use its address in lists, ie compare for &nil instead of
NULL. This would avoid :
- The conditional test in some prefetch() implementations
- The potential TLB problem with the NULL value.
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