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

[Andrew Haley]

On Sat, 6 Jan 2024 17:44:04 GMT, Andrew Haley <aph at openjdk.org> wrote:

>>> 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.

> @theRealAph do you want to fix this? Otherwise I'll just push a PR removing the assert, since it blocks this: #16245

I've just started working on it. If you like, push a removing the assert, and then my fix will re-insert it.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/16991#issuecomment-1915006526