RFR: 8256730: Code that uses Object.checkIndex() range checks doesn't optimize well

[Roland Westrelin]

On Fri, 20 Nov 2020 09:42:03 GMT, Roland Westrelin <roland at openjdk.org> wrote:

> This was reported by Paul with the vector API. There are 2 issues:
> 
> - CastII nodes (added by Objects.checkIndex()) gets in the way of the
>   pattern matching performed by range check elimination
> 
> - By transforming (CastII (AddI x y)) into (AddI (CastII x) (CastII y))
>   some CastII can be eliminated which improves address computation code.

> @rwestrel this has now been approved, did you forget about it?

I didn't but the rule for non trivial hotspot/compiler changes is 2 reviews unless that has changed.

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PR: https://git.openjdk.java.net/jdk/pull/1342