review (S) for 6984979: OptimizeFill misses some cases with an odd memory graph

[Vladimir Kozlov]

Tom,

Should we also check that n->is_Phi() && n->in(LoopNode::LoopBackControl) == store?

Thanks,
Vladimir

Tom Rodriguez wrote:
> http://cr.openjdk.java.net/~never/6984979
> 
> 6984979: OptimizeFill misses some cases with an odd memory graph
> Reviewed-by:
> 
> The logic for the new OptimizeFill code misses a case where the Phi
> usage is different than expected.  Sometimes during transformation of
> the loop there are uses of the memory phi outside the loop.  This
> appears to be a valid though slightly surprising structure but it
> interferes with the fill matching logic that assumes the store in the
> loop should be the only outgoing state.  The fix is to allow the phi
> to be used outside the loop and replace it with the outgoing memory of
> the call to the fill.  Tested with jbb, runthere and ctw.