RFR: 8129920 - Vectorized loop unrolling (original) (raw)

Vladimir Kozlov vladimir.kozlov at oracle.com
Mon Jun 29 20:59:48 UTC 2015

ignore_slp() and NoMoreSlp whould be fine names if they guard only superword optimization. You use it to skipp all loop optimizations except unrolling. It should be named differently. allow_unroll_only ?

why you need set_notpassed_slp()?:

more unrolling.

Thanks, Vladimir

On 6/26/15 12:43 PM, Berg, Michael C wrote:

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 webrev: http://cr.openjdk.java.net/~mcberg/8129920/webrev.01/ 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. Thanks, Michael

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