On 10/22/15 04:07, Richard Biener wrote:
Yeah, please make them either end or start a BB so we have to check
at most a single stmt. ECF_RETURNS_TWICE should achieve that,
it also makes it a code motion barrier.
Just so I'm clear, you're not saying that RETURNS_TWICE will stop the call being
duplicated though?
thinking a little further, a code motion barrier is stronger than I need (but
conservatively safe). For instance:
UNIQUE (HEAD)
for (...)
{
a = <loop_invariant_expr>
}
UNIQUE (TAIL)
It would be safe and desirable to move that loop invariant to before the UNIQUE.
Perhaps it won't matter in practice -- after all having N physical threads
calculate it in parallel (just after the HEAD marker, but before the loop) will
probably take no longer than a single thread doing it while the others wait.[*]
nathan
[*] ut it will take more power.
