RFR: 8281429: PhiNode::Value() is too conservative for tripcount of CountedLoop [v8]

[Vladimir Kozlov]

On Thu, 5 May 2022 08:35:58 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> The type for the iv phi of a counted loop is computed from the types
>> of the phi on loop entry and the type of the limit from the exit
>> test. Because the exit test is applied to the iv after increment, the
>> type of the iv phi is at least one less than the limit (for a positive
>> stride, one more for a negative stride).
>> 
>> Also, for a stride whose absolute value is not 1 and constant init and
>> limit values, it's possible to compute accurately the iv phi type.
>> 
>> This change caused a few failures and I had to make a few adjustments
>> to loop opts code as well.
>
> Roland Westrelin has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 23 commits:
> 
>  - whitespaces
>  - more review
>  - Merge branch 'master' into JDK-8281429
>  - review
>  - undo unneeded change
>  - Merge branch 'master' into JDK-8281429
>  - redo change removed by error
>  - review
>  - Merge branch 'master' into JDK-8281429
>  - undo
>  - ... and 13 more: https://git.openjdk.java.net/jdk/compare/29c2e54c...6d145597

This looks good. Thank you.

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Marked as reviewed by kvn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/7823