RFR: 8276673: Optimize abs operations in C2 compiler [v4]

[Jie Fu]

On Fri, 17 Dec 2021 09:04:39 GMT, Fei Gao <fgao at openjdk.org> wrote:

> Your cases also help prove that these several patterns, like abs(0-x) and abs(positive_value), are very fundamental and common.

I don't think so.
In real programs, I will never write code like `Math.abs(0 - x)`, `Math.abs(-1 * x)` and `Math.abs(x / (-1))`.

How about improving your micro-bechmark to show the performance gain?
To be honest, benchmarking with `Math.abs(-3)` seems strange to me since I don't think people will write that code.
So I would suggest writing a jmh test which may be used in real programs.
Thanks.

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PR: https://git.openjdk.java.net/jdk/pull/6755