RFR: 8352681: C2 compilation hits asserts "must set the initial type just once" [v2]

[Christian Hagedorn]

On Mon, 7 Apr 2025 16:54:47 GMT, Cesar Soares Lucas <cslucas at openjdk.org> wrote:

>> The reason for the error reported is that when RAM tries to reduce a field load through a Phi it ends up calling `step_through_mergemem` with `_delay_transform` set to true and, since `step_through_mergemem` assumes that `_delay_transform` is `false`, it calls `igvn->transform` passing a MergeMem that has been added to the graph long ago.
>> 
>> I didn't opt to make `_delay_transform` false during the RAM transformations because that seemed to be a risky move, nevertheless I'll create an RFE and keep investigating that option.
>> 
>> Also, while working on a test case I found that C2 doesn't remove (at least not before EA steps) the `if (param != param) {...}` and I'm going to investigate that as a separate RFE.
>> 
>> I tested this with JTREG Tier 1-3 on Linux x86_64.
>
> Cesar Soares Lucas has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix typo & test

Marked as reviewed by chagedorn (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/24471#pullrequestreview-2749408738