RFR: 8270366: C2: Add associative rule to add/sub node

[Zhengyu Gu]

On Wed, 14 Jul 2021 14:01:19 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> Hi Zhengyu,
> 
> It looks like you are missing a case for both long and int. Your code looks for these patterns:
> 
> ```
> a*b+a*c --> a*(b+c)
> a*b+b*c --> b*(a+c)
> a*c+b*c --> (a+b)*c
> ```
> 
> So you are not transforming this this case
> 
> ```
> a*b+c*a -> a*(b+c)
> ```


Thanks, Andrew.

Updated.

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PR: https://git.openjdk.java.net/jdk/pull/4765