RFR: 8319690: [AArch64] C2 compilation hits offset_ok_for_immed: assert "c2 compiler bug"

[Andrew Haley]

On Thu, 7 Dec 2023 06:45:30 GMT, Fei Gao <fgao at openjdk.org> wrote:

>> After this change, `immIOffset` and `immLOffset` appear to be obsolete.
>
>> After this change, `immIOffset` and `immLOffset` appear to be obsolete.
> 
> Removed them in the new commit. Thanks!

> @fg1417 what is the state on this?
> 
> The example here may look like a strange edge-case. But with my plans this may become more common: [JDK-8318446](https://bugs.openjdk.org/browse/JDK-8318446) C2: implement StoreNode::Ideal_merge_stores
> 
> I will merge stores, which can then look like unaligned stores of a larger type. This bug here blocks my progress. I'm not in a hurry, just curious if there is now a plan how to proceed here ;)

The problem with this PR is that the code is way too complex for such a simple problem. The port is correct as it is, in the release build.

The only problem is an assertion. We could simply remove that assertion, but if it were me I'd fix the problem properly. Both @dean-long and I have suggested ways to improve this patch with less code. If @fg1417 decides to drop this PR I'll fix it.

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PR Comment: https://git.openjdk.org/jdk/pull/16991#issuecomment-1879765450