RFR: 8349139: C2: Div looses dependency on condition that guarantees divisor not null in counted loop [v2]

[Emanuel Peter]

On Tue, 25 Feb 2025 07:56:36 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Roland Westrelin has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:
>> 
>>  - Merge branch 'master' into JDK-8349139
>>  - fix & test
>
> test/hotspot/jtreg/compiler/controldependency/TestDivDependentOnMainLoopGuard.java line 50:
> 
>> 48:                 i1 <<= i3;
>> 49:             } while (++i2 < 68);
>> 50:             for (i23 = 68; i23 > 2; otherPhi=i23-1, i23--) {
> 
> This is essencially the test from https://github.com/openjdk/jdk/pull/3190, we only changed the `3` to a `2`. This indicates that we need to probably slightly generalize the test. Can we maybe randomize the constant, just to get a little better coverage?

Because the other test became ineffective, and it would be a shame if the same happened to this one ;)

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PR Review Comment: https://git.openjdk.org/jdk/pull/23617#discussion_r1969185979