RFR: 8283094: Add Ideal transformation: x + (con - y) -> (x - y) + con [v6]

[Vladimir Kozlov]

On Tue, 29 Mar 2022 23:21:37 GMT, Zhiqiang Zang <duke at openjdk.java.net> wrote:

>> Hello,
>> 
>> `x + (con - y)  -> (x - y) + con` is a widely seen pattern; however it is missing in current implementation, which prevents some obvious constant folding from happening, such as `x + (1 - y) + 2` will be not optimized at all, rather than into `x - y + 3`.
>> 
>> This pull request adds this transformation.
>
> Zhiqiang Zang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   do not transform for loop induction variable.

Good.

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Marked as reviewed by kvn (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/7795