RFR: 8129920 - Vectorized loop unrolling

Berg, Michael C michael.c.berg at intel.com
Fri Jun 26 19:43:56 UTC 2015

Hi Folks,

I would like to contribute Vectorized loop unrolling. I need two reviewers to review this patch and comment as needed:

Bug-id: https://bugs.openjdk.java.net/browse/JDK-8129920


With this change we leverage superword unrolling queries and superword to stage re-entrance to ideal loop optimization. We do this when superword succeeds on vectorizing a loop which was unroll query mapped. When we re-enter ideal loop optimization, we have already done all major optimizations such as peeling, splitting, rce and superword on the vector map candidate loop. Thus we only unroll the loop. We utilize the standard loop unrolling environment to accomplish this with default and any applicable user settings. In this way we leverage unroll factors from the baseline loop which are much larger to obtain optimum throughput on x86 architectures. The uplift range on SpecJvm2008 is seen on scimark.lu.{small,large} with uplift noted at 3% and 8% respectively. We see as much as 1.5x uplift on vector centric micros like reductions on default optimizations.

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