Loading... (original) (raw)

• Type: Enhancement
• Resolution: Fixed
• Priority: P3
• Fix Version/s: 9
• Affects Version/s: 9
• Environment:
  Only applicable for x86 targets. Vendors will need to enable first unrolling queries and possible augment this work for non x86 targets.

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 setting 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.

backported by

JDK-8135603 Vectorized loop unrolling

• 
• Resolved

relates to

JDK-8149421 Vectorized Post Loops

• 
• Resolved

JDK-8080325 SuperWord loop unrolling analysis

• 
• Resolved