Request for reviews (S): 7035946: Up to 15% regression on JDK 7 b136 vs b135 on specjvm2008.crypto.rsa on x64
vladimir.kozlov at oracle.com
Fri Sep 9 09:54:24 PDT 2011
7035946: Up to 15% regression on JDK 7 b136 vs b135 on specjvm2008.crypto.rsa on x64
It is almost exact anti-delta of my changes in 7008866. I kept
replace_parallel_iv() as separate method and added new TraceLoopOpts output.
I traced down the most of regression to my changes for "replace parallel
induction variables" optimization in 7008866 fix. I replaced new nodes IGVN
registration with immediate Ideal transformation. As result Split_If
optimization reversed it back by doing spit through Phi and it prevents loop
predicates (which follow Split_If) execute RCE. If local transformation in
replace_parallel_iv() is not executed the created new code matches RCE shape:
iv*ratio+(init2-init*ratio) where (init2-init*ratio) is loop invariant. And
Split_If optimization does not execute spit through Phi for AddI nodes in
Counted loops. Yes, a lot of hidden dependences.
An other part of regression came from always creation of new loop iteration Phi
node. I was not able to find why it has regression affect. I returned code back
to keep original Phi.
I do not see affect on refworkload benchmark after this fix.
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