RFR: 8286104: use aggressive liveness for unstable_if traps [v7]

[Vladimir Kozlov]

On Wed, 1 Jun 2022 20:31:34 GMT, Xin Liu <xliu at openjdk.org> wrote:

> Yes, this is for 8287385. I will remove preprocessing logic from this PR.

Okay.

> Because we can determine a unstable_if trap is trivial after parsing. My idea is to do the leftover parsing job in this preprocess function. That's why I think preprocess should before `PhaseRemoveUseless`.

Then you should consider my proposal about cleaning the list and update counters in `Compile::remove_useless_nodes()`. Let discuss it in next changes.

>> test/hotspot/jtreg/compiler/c2/irTests/TestAggressiveLivenessForUnstableIf.java line 2:
>> 
>>> 1: /*
>>> 2:  * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
>> 
>> Missing year.
>
> I was told (by the company's open-source policy) to write a header like this.  I guess they just want to reduce chore of maintaining years.  This also consistent with other code we contributed.

Yes, you are right.

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PR: https://git.openjdk.java.net/jdk/pull/8545