RFR: 8370481: C2 SuperWord: Long/Integer.compareUnsigned return wrong value in SLP [v3]

[Emanuel Peter]

On Thu, 23 Oct 2025 14:33:04 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   add all possible Cmp cases; add comments
>
> src/hotspot/share/opto/superword.cpp line 1752:
> 
>> 1750:   case Op_CmpUL:
>> 1751:   case Op_CmpU3:
>> 1752:   case Op_CmpUL3:
> 
> Do these really ever survive to here? I thought they should all be turned into other ops? Do you have an example?

If these never come through here, then just let them go into the default case.

> src/hotspot/share/opto/superword.cpp line 1760:
> 
>> 1758:   case Op_CmpP:
>> 1759:   case Op_CmpD3:
>> 1760:   case Op_CmpF3:
> 
> These would probably have the same issue as the regular `CmpF/CmpD`, no? So are we sure we can "allow-list" them here?

If these never come through here, then just let them go into the default case.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/27942#discussion_r2455369138
PR Review Comment: https://git.openjdk.org/jdk/pull/27942#discussion_r2455369339