JDK-8168481 : Check possibility of improved performance with the (CastII (AddI x const)) -> (AddI (CastII x) const) transformation
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 9,10
  • Priority: P4
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2016-10-21
  • Updated: 2019-01-15
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Other
tbdUnresolved
Related Reports
Relates :  
JDK-8145322 - Code generated from unsafe loops can be slightly improved
Description
The [(CastII (AddI x const)) -> (AddI (CastII x) const) transformation change block in CastIINode::Ideal() - castnode.cpp] was earlier added as part of old JDK-8145322 enhancement fix. ("Code generated from unsafe loops can be slightly improved")

But in later reported JDK-8165661, found that the 8145322 part changes causing performance regression for x86_64. So the same got reverted for JDK-8165661 fix.

Creating this new enhancement CR to investigate issues with OLD 8145322 changes and for a possible better version of the same.
Comments
Hi [~roland], Request your help here. If you are not planning to get the fix in for this task, for JDK 11, can you please change the 'Fix Version' to tbd_feature or tbd_update. Thank you.
03-05-2018
We have to be careful to not re-introduce JDK-8177095 with this change because that optimization narrows the type of a range check dependent CastII.
23-03-2017