RFR: 8281429: PhiNode::Value() is too conservative for tripcount of CountedLoop [v6]

[Roland Westrelin]

On Thu, 14 Apr 2022 00:37:21 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   redo change removed by error
>
> src/hotspot/share/opto/loopnode.cpp line 854:
> 
>> 852:     swap(lo, hi);
>> 853:   }
>> 854:   if (hi->hi_as_long() <= lo->lo_as_long()) {
> 
> why this is <= instead of < ?

If hi->hi_as_long() == lo->lo_as_long() the body is entered at most once and there's no loop, right?
FWIW, this test is in case the LongCountedLoop was created in the current pass of loop opts and igvn hasn't had a chance to run yet (and optimize the backedge out).

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PR: https://git.openjdk.java.net/jdk/pull/7823